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Wikipedia

Solar flare

For the class of stars that undergo similar phenomena, see flare star. For the 1975 song by Robert Wyatt, see Ruth Is Stranger Than Richard.
"Sun flare" redirects here. For the rose variety, see Rosa 'Sun Flare'.

A solar flare is a sudden flash of increased brightness on the Sun, usually observed near its surface and in close proximity to a sunspot group. Powerful flares are often, but not always, accompanied by a coronal mass ejection. Even the most powerful flares are barely detectable in the total solar irradiance (the "solar constant").

Solar flare and its prominence eruption recorded on June 7, 2011 by SDO in extreme ultraviolet
Evolution of magnetism on the Sun
On August 31, 2012, a long prominence/filament of solar material that had been hovering in the Sun's atmosphere, the corona, erupted out into space at 4:36 p.m. EDT. Seen here from the Solar Dynamics Observatory, the flare caused auroras to be seen on Earth on September 3.

Solar flares occur in a power-law spectrum of magnitudes; an energy release of typically 1020 joules of energy suffices to produce a clearly observable event, while a major event can emit up to 1025 joules. Although originally observed in the visible electromagnetic spectrum, especially in the emission line of hydrogen, they can now be detected from radio waves to gamma-rays.

Flares are closely associated with the ejection of plasmas and particles through the Sun's corona into interplanetary space; flares also copiously emit radio waves. If the ejection is in the direction of the Earth, particles associated with this disturbance can penetrate into the upper atmosphere (the ionosphere) and cause bright auroras, and may even disrupt long-range radio communication. It usually takes days for the solar plasma ejecta to reach Earth. Flares also occur on other stars, where the term stellar flare applies. High-energy particles, which may be relativistic, can arrive almost simultaneously with the electromagnetic radiations.

Contents

Solar flares affect all layers of the solar atmosphere (photosphere, chromosphere, and corona). The plasma medium is heated to tens of millions of kelvins, while electrons, protons, and heavier ions are accelerated to near the speed of light. Flares produce electromagnetic radiation across the electromagnetic spectrum at all wavelengths, from radio waves to gamma rays. Most of the energy is spread over frequencies outside the visual range; the majority of the flares are not visible to the naked eye and must be observed with special instruments. Flares occur in active regions around sunspots, where intense magnetic fields penetrate the photosphere to link the corona to the solar interior. Flares are powered by the sudden (timescales of minutes to tens of minutes) release of magnetic energy stored in the corona. The same energy releases may produce coronal mass ejections (CMEs), although the relationship between CMEs and flares is still not well understood.

X-rays and UV radiation emitted by solar flares can affect Earth's ionosphere and disrupt long-range radio communications. Direct radio emission at decimetric wavelengths may disturb the operation of radars and other devices that use those frequencies.

Solar flares were first observed on the Sun by Richard Christopher Carrington and independently by Richard Hodgson in 1859 as localized visible brightenings of small areas within a sunspot group. Stellar flares can be inferred by looking at the lightcurves produced from the telescope or satellite data of variety of other stars.

The frequency of occurrence of solar flares varies following the 11-year solar cycle. It can range from several per day during solar maximum to less than one every week during solar minimum. Large flares are less frequent than smaller ones.

Flares occur when accelerated charged particles, mainly electrons, interact with the plasma medium. Evidence suggests that the phenomenon of magnetic reconnection leads to this extreme acceleration of charged particles. On the Sun, magnetic reconnection may happen on solar arcades – a series of closely occurring loops following magnetic lines of force. These lines of force quickly reconnect into a lower arcade of loops leaving a helix of magnetic field unconnected to the rest of the arcade. The sudden release of energy in this reconnection is the origin of the particle acceleration. The unconnected magnetic helical field and the material that it contains may violently expand outwards forming a coronal mass ejection. This also explains why solar flares typically erupt from active regions on the Sun where magnetic fields are much stronger.

Although there is a general agreement on the source of a flare's energy, the mechanisms involved are still not well understood. It's not clear how the magnetic energy is transformed into the kinetic energy of the particles, nor is it known how some particles can be accelerated to the GeV range (109 electron volt) and beyond. There are also some inconsistencies regarding the total number of accelerated particles, which sometimes seems to be greater than the total number in the coronal loop. Scientists are unable to forecast flares.[citation needed]

Powerful X-class flares create radiation storms that produce auroras and can give airline passengers flying over the poles small radiation doses.
On August 1, 2010, the Sun shows a C3-class solar flare (white area on upper left), a solar tsunami (wave-like structure, upper right) and multiple filaments of magnetism lifting off the stellar surface.
Multi-spacecraft observations of the March 20, 2014 X-class flare.

The classification system for solar flares uses the letters A, B, C, M or X, according to the peak flux in watts per square metre (W/m2) of X-rays with wavelengths 100 to 800 picometres (1 to 8 ångströms), as measured at the Earth by the GOES spacecraft.[clarification needed]

Classification Approximate peak flux range at 100–800 picometre
(watts/square metre)
A < 10−7
B 10−7 – 10−6
C 10−6 – 10−5
M 10−5 – 10−4
X > 10−4

The strength of an event within a class is noted by a numerical suffix ranging from 1 up to, but excluding, 10, which is also the factor for that event within the class. Hence, an X2 flare is twice the strength of an X1 flare, an X3 flare is three times as powerful as an X1, and only 50% more powerful than an X2. An X2 is four times more powerful than an M5 flare. X-class flares with a peak flux that exceeds 10−3 W/m2 may be noted with a numerical suffix equal to or greater than 10.

H-alpha classification

An earlier flare classification was based on spectral observations. The scheme uses both the intensity and emitting surface. The classification in intensity is qualitative, referring to the flares as: faint (f), normal (n) or brilliant (b). The emitting surface is measured in terms of millionths of the hemisphere and is described below. (The total hemisphere area AH = 15.5 × 1012 km2.)

Classification Corrected area
(millionths of hemisphere)
S < 100
1 100–250
2 250–600
3 600–1200
4 > 1200

A flare then is classified taking S or a number that represents its size and a letter that represents its peak intensity, v.g.: Sn is a normal sunflare.

Massive X6.9 class solar flare, August 9, 2011

Solar flares strongly influence the local space weather in the vicinity of the Earth. They can produce streams of highly energetic particles in the solar wind or stellar wind, known as a solar particle event. These particles can impact the Earth's magnetosphere (see main article at geomagnetic storm), and present radiation hazards to spacecraft and astronauts. Additionally, massive solar flares are sometimes accompanied by coronal mass ejections (CMEs) which can trigger geomagnetic storms that have been known to disable satellites and knock out terrestrial electric power grids for extended periods of time.

The soft X-ray flux of X class flares increases the ionization of the upper atmosphere, which can interfere with short-wave radio communication and can heat the outer atmosphere and thus increase the drag on low orbiting satellites, leading to orbital decay.[citation needed] Energetic particles in the magnetosphere contribute to the aurora borealis and aurora australis. Energy in the form of hard X-rays can be damaging to spacecraft electronics and are generally the result of large plasma ejection in the upper chromosphere.

The radiation risks posed by solar flares are a major concern in discussions of a human mission to Mars, the Moon, or other planets. Energetic protons can pass through the human body, causing biochemical damage, presenting a hazard to astronauts during interplanetary travel. Some kind of physical or magnetic shielding would be required to protect the astronauts. Most proton storms take at least two hours from the time of visual detection to reach Earth's orbit. A solar flare on January 20, 2005, released the highest concentration of protons ever directly measured, which would have given astronauts on the moon little time to reach shelter.

Flares produce radiation across the electromagnetic spectrum, although with different intensity. They are not very intense in visible light, but they can be very bright at particular spectral lines. They normally produce bremsstrahlung in X-rays and synchrotron radiation in radio.

History

Optical observations

Richard Carrington observed a flare for the first time on 1 September 1859 projecting the image produced by an optical telescope through a broad-band filter. It was an extraordinarily intense white light flare. Since flares produce copious amounts of radiation at , adding a narrow ( ≈1 Å) passband filter centered at this wavelength to the optical telescope allows the observation of not very bright flares with small telescopes. For years Hα was the main, if not the only, source of information about solar flares. Other passband filters are also used.

Radio observations

During World War II, on February 25 and 26, 1942, British radar operators observed radiation that Stanley Hey interpreted as solar emission. Their discovery did not go public until the end of the conflict. The same year Southworth also observed the Sun in radio, but as with Hey, his observations were only known after 1945. In 1943 Grote Reber was the first to report radioastronomical observations of the Sun at 160 MHz. The fast development of radioastronomy revealed new peculiarities of the solar activity like storms and bursts related to the flares. Today ground-based radiotelescopes observe the Sun from c. 15 MHz up to 400 GHz.

Space telescopes

Since the beginning of space exploration, telescopes have been sent to space, where it is possible to detect wavelengths shorter than UV, which are completely absorbed by the Earth's atmosphere, and where flares may be very bright. Since the 1970s, the GOES series of satellites observe the Sun in soft X-rays, and their observations became the standard measure of flares, diminishing the importance of the classification. Hard X-rays were observed by many different instruments, the most important today being the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). Nonetheless, UV observations are today the stars of solar imaging with their incredible fine details that reveal the complexity of the solar corona. Spacecraft may also bring radio detectors at extremely long wavelengths (as long as a few kilometers) that cannot propagate through the ionosphere.

Optical telescopes

Two successive photos of a solar flare phenomenon. The solar disc was blocked in these photos for better visualization of the flare's accompanying protruding prominence.

Radio telescopes

  • Nançay Radioheliographe (NRH) is an interferometer composed of 48 antennas observing at meter-decimeter wavelengths. The radioheliographe is installed at the Nançay Radio Observatory, France.
  • Owens Valley Solar Array (OVSA) is a radio interferometer operated by the New Jersey Institute of Technology originally consisting of 7 antennas, observing from 1 to 18 GHz in both left and right circular polarization. OVSA is located in Owens Valley, California. It is now called Expanded Owens Valley Solar Array (EOVSA) after the expansion to upgrade its control system and increase the total number of antennas to 15.
  • Nobeyama Radioheliograph (NoRH) is an interferometer installed at the Nobeyama Radio Observatory, Japan, formed by 84 small (80 cm) antennas, with receivers at 17 GHz (left and right polarization) and 34 GHz operating simultaneously. It continuously observes the Sun, producing daily snapshots.
  • Siberian Solar Radio Telescope (SSRT) is a special-purpose solar radio telescope designed for studying solar activity in the microwave range (5.7 GHz) where the processes occurring in the solar corona are accessible to observation over the entire solar disk. It is a crossed interferometer, consisting of two arrays of 128x128 parabolic antennas 2.5 meters in diameter each, spaced equidistantly at 4.9 meters and oriented in the E-W and N-S directions. It is located in a wooded valley separating two mountain ridges of the Eastern Sayan Mountains and Khamar-Daban, 220 km from Irkutsk, Russia.
  • Nobeyama Radio Polarimeters are a set of radio telescopes installed at the Nobeyama Radio Observatory that continuously observes the full Sun (no images) at the frequencies of 1, 2, 3.75, 9.4, 17, 35, and 80 GHz, at left and right circular polarization.
  • Solar Submillimeter Telescope is a single dish telescope, that observes continuously the Sun at 212 and 405 GHz. It is installed at Complejo Astronomico El Leoncito in Argentina. It has a focal array composed by 4 beams at 212 GHz and 2 at 405 GHz, therefore it can instantaneously locate the position of the emitting source SST is the only solar submillimeter telescope currently in operation.
  • Polarization Emission of Millimeter Activity at the Sun (POEMAS) is a system of two circular polarization solar radio telescopes, for observations of the Sun at 45 and 90 GHz. The novel characteristic of these instruments is the capability to measure circular right- and left-hand polarizations at these high frequencies. The system is installed at Complejo Astronomico El Leoncito in Argentina. It started operations in November 2011. In November 2013 it went offline for repairs. It is expected to return to observing in January 2015.
  • Bleien Radio Observatory is a set of radio telescopes operating near Gränichen (Switzerland). They continuously observe the solar flare radio emission from 10 MHz (ionospheric limit) to 5 GHz. The broadband spectrometers are known as Phoenix and CALLISTO.

Space telescopes

GOES-17 captures a C2-class solar flare on May 28, 2018, across different spectral bands
GOES-16 ultraviolet image of a M1.1 solar flare on May 29, 2020

The following spacecraft missions have flares as their main observation target.

  • Yohkoh – The Yohkoh (originally Solar A) spacecraft observed the Sun with a variety of instruments from its launch in 1991 until its failure in 2001. The observations spanned a period from one solar maximum to the next. Two instruments of particular use for flare observations were the Soft X-ray Telescope (SXT), a glancing incidence low energy X-ray telescope for photon energies of order 1 keV, and the Hard X-ray Telescope (HXT), a collimation counting instrument which produced images in higher energy X-rays (15–92 keV) by image synthesis.
  • WIND – The Wind spacecraft is devoted to the study of the interplanetary medium. Since the Solar Wind is its main driver, solar flares effects can be traced with the instruments aboard Wind. Some of the WIND experiments are: a very low frequency spectrometer, (WAVES), particles detectors (EPACT, SWE) and a magnetometer (MFI).
  • GOES – The GOES spacecraft are satellites in geostationary orbits around the Earth that have measured the soft X-ray flux from the Sun since the mid-1970s, following the use of similar instruments on the Solrad satellites. GOES X-ray observations are commonly used to classify flares, with A, B, C, M, and X representing different powers of ten – an X-class flare has a peak 1–8 Å flux above 0.0001 W/m2.
  • RHESSI – The Reuven Ramaty High Energy Solar Spectral Imager was designed to image solar flares in energetic photons from soft X rays (ca. 3 keV) to gamma rays (up to ca. 20 MeV) and to provide high resolution spectroscopy up to gamma-ray energies of ca. 20 MeV. Furthermore, it had the capability to perform spatially resolved spectroscopy with high spectral resolution. It was decommissioned in August 2018, after more than 16 years of operation.
  • SOHO – The Solar and Heliospheric Observatory is collaboration between the ESA and NASA which has been in continuous operation since December 1995.[citation needed] It carries 12 different instruments, among them the Extreme ultraviolet Imaging Telescope (EIT), the Large Angle and Spectrometric Coronagraph (LASCO) and the Michelson Doppler Imager (MDI). SOHO is in a halo orbit around the earth-sun L1 point.
  • TRACE – The Transition Region and Coronal Explorer is a NASA Small Explorer program (SMEX) to image the solar corona and transition region at high angular and temporal resolution. It has passband filters at 173 Å, 195 Å, 284 Å, 1600 Å with a spatial resolution of 0.5 arc sec, the best at these wavelengths.
  • SDO – The Solar Dynamics Observatory is a NASA project composed of 3 different instruments: the Helioseismic and Magnetic Imager (HMI), the Atmospheric Imaging Assembly (AIA) and the Extreme Ultraviolet Variability Experiment (EVE). As of June 2013[update], it had been planned to operate for many years after it is launched into a geosynchronous earth orbit.[needs update]
  • Hinode –The Hinode spacecraft, originally called Solar B, was launched by the Japan Aerospace Exploration Agency in September 2006 to observe solar flares in more precise detail. Its instrumentation, supplied by an international collaboration including Norway, the U.K., the U.S., and Africa focuses on the powerful magnetic fields thought to be the source of solar flares. Such studies should shed light on the causes of this activity, possibly helping to forecast future flares and thus minimize their dangerous effects on satellites and astronauts.[needs update]
  • ACE – The Advanced Composition Explorer was launched in 1997 into a halo orbit around the Earth–Sun L1 point. It carries spectrometers, magnetometers and charged particle detectors to analyze the solar wind. The Real Time Solar Wind (RTSW) beacon is continually monitored by a network of NOAA-sponsored ground stations to provide early warning of earth-bound CMEs.
  • MAVEN – The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, which launched from Cape Canaveral Air Force Station on November 18, 2013, is the first mission devoted to understanding the Martian upper atmosphere. The goal of MAVEN is to determine the role that loss of atmospheric gas to space played in changing the Martian climate through time. The Extreme Ultraviolet (EUV) monitor on MAVEN is part of the Langmuir Probe and Waves (LPW) instrument and measures solar EUV input and variability, and wave heating of the Martian upper atmosphere.[full citation needed]
  • STEREO – The Solar Terrestrial Relations Observatory is a solar observation mission consisting of two nearly identical spacecraft that were launched in 2006. Contact with STEREO-B was lost in 2014, but STEREO-A is still operational.[citation needed] Each spacecraft carries several instruments, including cameras, particle detectors and a radio burst tracker.

In addition to these solar observing facilities, many non-solar astronomical satellites observe flares either intentionally (e.g., NuSTAR), or simply because the penetrating hard radiations coming from a flare can readily penetrate most forms of shielding.

Examples of large solar flares

Short narrated video about Fermi's observations of the highest-energy light ever associated with an eruption on the Sun as of March 2012
Active Region 1515 released an X1.1 class flare from the lower right of the Sun on July 6, 2012, peaking at 7:08 PM EDT. This flare caused a radio blackout, labeled as an R3 on the National Oceanic and Atmospheric Administrations scale that goes from R1 to R5.
Space weather—March 2012.
Main article: List of solar storms

The most powerful flare ever observed was the first one to be observed, on September 1, 1859, and was reported by British astronomer Richard Carrington and independently by an observer named Richard Hodgson. The event is named the Solar storm of 1859, or the "Carrington event". The flare was visible to a naked eye (in white light), and produced stunning auroras down to tropical latitudes such as Cuba or Hawaii, and set telegraph systems on fire. The flare left a trace in Greenland ice in the form of nitrates and beryllium-10, which allow its strength to be measured today. Cliver and Svalgaard reconstructed the effects of this flare and compared with other events of the last 150 years. In their words: "While the 1859 event has close rivals or superiors in each of the above categories of space weather activity, it is the only documented event of the last ∼150 years that appears at or near the top of all of the lists." The intensity of the flare has been estimated to be around X50.

The ultra-fast coronal mass ejection of August 1972 is suspected of triggering magnetic fuses on naval mines during the Vietnam War, and would have been a life-threatening event to Apollo astronauts if it had occurred during a mission to the Moon.

In modern times, the largest solar flare measured with instruments occurred on November 4, 2003. This event saturated the GOES detectors, and because of this its classification is only approximate. Initially, extrapolating the GOES curve, it was estimated to be X28. Later analysis of the ionospheric effects suggested increasing this estimate to X45. This event produced the first clear evidence of a new spectral component above 100 GHz.

Other large solar flares also occurred on April 2, 2001 (X20), October 28, 2003 (X17.2 and 10), September 7, 2005 (X17), February 17, 2011 (X2), August 9, 2011 (X6.9), March 7, 2012 (X5.4), July 6, 2012 (X1.1). On July 6, 2012, a solar storm hit just after midnight UK time, when an X1.1 solar flare fired out of the AR1515 sunspot. Another X1.4 solar flare from AR 1520 region of the Sun, second in the week, reached the Earth on July 15, 2012 with a geomagnetic storm of G1–G2 level. A X1.8-class flare was recorded on October 24, 2012. There has been major solar flare activity in early 2013, notably within a 48-hour period starting on May 12, 2013, a total of four X-class solar flares were emitted ranging from an X1.2 and upwards of an X3.2, the latter of which was one of the largest year 2013 flares. Departing sunspot complex AR2035-AR2046 erupted on April 25, 2014, at 0032 UT, producing a strong X1.3-class solar flare and an HF communications blackout on the day-side of Earth. NASA's Solar Dynamics Observatory recorded a flash of extreme ultraviolet radiation from the explosion. The Solar Dynamics Observatory recorded an X9.3-class flare at around 1200 UTC on September 6, 2017.

On July 23, 2012, a massive, potentially damaging,[vague] solar storm (solar flare, coronal mass ejection and electromagnetic radiation) barely missed Earth. In 2014, Pete Riley of Predictive Science Inc. published a paper in which he attempted to calculate the odds of a similar solar storm hitting Earth within the next 10 years, by extrapolating records of past solar storms from the 1960s to the present day. He concluded that there may be as much as a 12% chance of such an event occurring.

Flare sprays are a type of eruption associated with solar flares. They involve faster ejections of material than eruptive prominences, and reach velocities of 20 to 2000 kilometers per second.

Erich Rieger discovered with coworkers in 1984 a ~154 days period in hard solar flares at least since the solar cycle 19. The period has since been confirmed in most heliophysics data and the interplanetary magnetic field and is commonly known as the Rieger period. The period's resonance harmonics also have been reported from most data types in the heliosphere. Possible causes of this solar wind resonance include influences of planetary constellations on the Sun.

Current methods of flare prediction are problematic, and there is no certain indication that an active region on the Sun will produce a flare. However, many properties of sunspots and active regions correlate with flaring. For example, magnetically complex regions (based on line-of-sight magnetic field) called delta spots produce the largest flares. A simple scheme of sunspot classification due to McIntosh, or related to fractal complexity is commonly used as a starting point for flare prediction. Predictions are usually stated in terms of probabilities for occurrence of flares above M or X GOES class within 24 or 48 hours. The U.S. National Oceanic and Atmospheric Administration (NOAA) issues forecasts of this kind.MAG4 was developed at the University of Alabama in Huntsville with support from the Space Radiation Analysis Group at Johnson Space Flight Center (NASA/SRAG) for forecasting M and X class flares, CMEs, fast CME, and Solar Energetic Particle events. A physics-based method that can predict imminent large solar flares was proposed by Institute for Space-Earth Environmental Research (ISEE), Nagoya University.

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Solar flare
Solar flare Language Watch Edit For the class of stars that undergo similar phenomena see flare star For the 1975 song by Robert Wyatt see Ruth Is Stranger Than Richard Sun flare redirects here For the rose variety see Rosa Sun Flare A solar flare is a sudden flash of increased brightness on the Sun usually observed near its surface and in close proximity to a sunspot group Powerful flares are often but not always accompanied by a coronal mass ejection Even the most powerful flares are barely detectable in the total solar irradiance the solar constant 1 Play mediaSolar flare and its prominence eruption recorded on June 7 2011 by SDO in extreme ultravioletPlay mediaEvolution of magnetism on the Sun On August 31 2012 a long prominence filament of solar material that had been hovering in the Sun s atmosphere the corona erupted out into space at 4 36 p m EDT Seen here from the Solar Dynamics Observatory the flare caused auroras to be seen on Earth on September 3 Solar flares occur in a power law spectrum of magnitudes an energy release of typically 1020 joules of energy suffices to produce a clearly observable event while a major event can emit up to 1025 joules 2 Although originally observed in the visible electromagnetic spectrum especially in the Ha emission line of hydrogen they can now be detected from radio waves to gamma rays Flares are closely associated with the ejection of plasmas and particles through the Sun s corona into interplanetary space flares also copiously emit radio waves If the ejection is in the direction of the Earth particles associated with this disturbance can penetrate into the upper atmosphere the ionosphere and cause bright auroras and may even disrupt long range radio communication It usually takes days for the solar plasma ejecta to reach Earth 3 Flares also occur on other stars where the term stellar flare applies High energy particles which may be relativistic can arrive almost simultaneously with the electromagnetic radiations Contents 1 Description 2 Cause 3 Classification 3 1 H alpha classification 4 Hazards 5 Observations 5 1 History 5 1 1 Optical observations 5 1 2 Radio observations 5 1 3 Space telescopes 5 2 Optical telescopes 5 3 Radio telescopes 5 4 Space telescopes 5 5 Examples of large solar flares 6 Flare spray 7 Flare periodicity 8 Prediction 9 See also 10 References 11 External linksDescription EditSolar flares affect all layers of the solar atmosphere photosphere chromosphere and corona The plasma medium is heated to tens of millions of kelvins while electrons protons and heavier ions are accelerated to near the speed of light Flares produce electromagnetic radiation across the electromagnetic spectrum at all wavelengths from radio waves to gamma rays Most of the energy is spread over frequencies outside the visual range the majority of the flares are not visible to the naked eye and must be observed with special instruments Flares occur in active regions around sunspots where intense magnetic fields penetrate the photosphere to link the corona to the solar interior Flares are powered by the sudden timescales of minutes to tens of minutes release of magnetic energy stored in the corona The same energy releases may produce coronal mass ejections CMEs although the relationship between CMEs and flares is still not well understood X rays and UV radiation emitted by solar flares can affect Earth s ionosphere and disrupt long range radio communications Direct radio emission at decimetric wavelengths may disturb the operation of radars and other devices that use those frequencies Solar flares were first observed on the Sun by Richard Christopher Carrington and independently by Richard Hodgson in 1859 4 as localized visible brightenings of small areas within a sunspot group Stellar flares can be inferred by looking at the lightcurves produced from the telescope or satellite data of variety of other stars The frequency of occurrence of solar flares varies following the 11 year solar cycle It can range from several per day during solar maximum to less than one every week during solar minimum Large flares are less frequent than smaller ones Cause EditFlares occur when accelerated charged particles mainly electrons interact with the plasma medium Evidence suggests that the phenomenon of magnetic reconnection leads to this extreme acceleration of charged particles 5 On the Sun magnetic reconnection may happen on solar arcades a series of closely occurring loops following magnetic lines of force These lines of force quickly reconnect into a lower arcade of loops leaving a helix of magnetic field unconnected to the rest of the arcade The sudden release of energy in this reconnection is the origin of the particle acceleration The unconnected magnetic helical field and the material that it contains may violently expand outwards forming a coronal mass ejection 6 This also explains why solar flares typically erupt from active regions on the Sun where magnetic fields are much stronger Although there is a general agreement on the source of a flare s energy the mechanisms involved are still not well understood It s not clear how the magnetic energy is transformed into the kinetic energy of the particles nor is it known how some particles can be accelerated to the GeV range 109 electron volt and beyond There are also some inconsistencies regarding the total number of accelerated particles which sometimes seems to be greater than the total number in the coronal loop Scientists are unable to forecast flares citation needed Classification Edit Play media Powerful X class flares create radiation storms that produce auroras and can give airline passengers flying over the poles small radiation doses On August 1 2010 the Sun shows a C3 class solar flare white area on upper left a solar tsunami wave like structure upper right and multiple filaments of magnetism lifting off the stellar surface 7 Play media Multi spacecraft observations of the March 20 2014 X class flare The classification system for solar flares uses the letters A B C M or X according to the peak flux in watts per square metre W m2 of X rays with wavelengths 100 to 800 picometres 1 to 8 angstroms as measured at the Earth by the GOES spacecraft clarification needed Classification Approximate peak flux range at 100 800 picometre watts square metre A lt 10 7B 10 7 10 6C 10 6 10 5M 10 5 10 4X gt 10 4 The strength of an event within a class is noted by a numerical suffix ranging from 1 up to but excluding 10 8 which is also the factor for that event within the class Hence an X2 flare is twice the strength of an X1 flare an X3 flare is three times as powerful as an X1 and only 50 more powerful than an X2 9 An X2 is four times more powerful than an M5 flare 10 X class flares with a peak flux that exceeds 10 3 W m2 may be noted with a numerical suffix equal to or greater than 10 11 H alpha classification Edit An earlier flare classification was based on Ha spectral observations The scheme uses both the intensity and emitting surface The classification in intensity is qualitative referring to the flares as faint f normal n or brilliant b The emitting surface is measured in terms of millionths of the hemisphere and is described below The total hemisphere area AH 15 5 1012 km2 Classification Corrected area millionths of hemisphere S lt 1001 100 2502 250 6003 600 12004 gt 1200 A flare then is classified taking S or a number that represents its size and a letter that represents its peak intensity v g Sn is a normal sunflare 12 Hazards Edit Play media Massive X6 9 class solar flare August 9 2011 Solar flares strongly influence the local space weather in the vicinity of the Earth They can produce streams of highly energetic particles in the solar wind or stellar wind known as a solar particle event These particles can impact the Earth s magnetosphere see main article at geomagnetic storm and present radiation hazards to spacecraft and astronauts Additionally massive solar flares are sometimes accompanied by coronal mass ejections CMEs which can trigger geomagnetic storms that have been known to disable satellites and knock out terrestrial electric power grids for extended periods of time The soft X ray flux of X class flares increases the ionization of the upper atmosphere which can interfere with short wave radio communication and can heat the outer atmosphere and thus increase the drag on low orbiting satellites leading to orbital decay citation needed Energetic particles in the magnetosphere contribute to the aurora borealis and aurora australis Energy in the form of hard X rays can be damaging to spacecraft electronics and are generally the result of large plasma ejection in the upper chromosphere The radiation risks posed by solar flares are a major concern in discussions of a human mission to Mars the Moon or other planets Energetic protons can pass through the human body causing biochemical damage 13 presenting a hazard to astronauts during interplanetary travel Some kind of physical or magnetic shielding would be required to protect the astronauts Most proton storms take at least two hours from the time of visual detection to reach Earth s orbit A solar flare on January 20 2005 released the highest concentration of protons ever directly measured which would have given astronauts on the moon little time to reach shelter 14 15 Observations EditFlares produce radiation across the electromagnetic spectrum although with different intensity They are not very intense in visible light but they can be very bright at particular spectral lines They normally produce bremsstrahlung in X rays and synchrotron radiation in radio History Edit Optical observations Edit Richard Carrington observed a flare for the first time on 1 September 1859 projecting the image produced by an optical telescope through a broad band filter It was an extraordinarily intense white light flare Since flares produce copious amounts of radiation at Ha adding a narrow 1 A passband filter centered at this wavelength to the optical telescope allows the observation of not very bright flares with small telescopes For years Ha was the main if not the only source of information about solar flares Other passband filters are also used Radio observations Edit During World War II on February 25 and 26 1942 British radar operators observed radiation that Stanley Hey interpreted as solar emission Their discovery did not go public until the end of the conflict The same year Southworth also observed the Sun in radio but as with Hey his observations were only known after 1945 In 1943 Grote Reber was the first to report radioastronomical observations of the Sun at 160 MHz The fast development of radioastronomy revealed new peculiarities of the solar activity like storms and bursts related to the flares Today ground based radiotelescopes observe the Sun from c 15 MHz up to 400 GHz Space telescopes Edit Since the beginning of space exploration telescopes have been sent to space where it is possible to detect wavelengths shorter than UV which are completely absorbed by the Earth s atmosphere and where flares may be very bright Since the 1970s the GOES series of satellites observe the Sun in soft X rays and their observations became the standard measure of flares diminishing the importance of the Ha classification Hard X rays were observed by many different instruments the most important today being the Reuven Ramaty High Energy Solar Spectroscopic Imager RHESSI Nonetheless UV observations are today the stars of solar imaging with their incredible fine details that reveal the complexity of the solar corona Spacecraft may also bring radio detectors at extremely long wavelengths as long as a few kilometers that cannot propagate through the ionosphere Optical telescopes Edit Two successive photos of a solar flare phenomenon The solar disc was blocked in these photos for better visualization of the flare s accompanying protruding prominence Big Bear Solar Observatory located in Big Bear Lake California and operated by the New Jersey Institute of Technology is a solar dedicated observatory with different instruments as well as a huge data bank of full disk Ha images 16 Swedish 1 m Solar Telescope operated by the Institute for Solar Physics Sweden is located in the Observatorio del Roque de los Muchachos on the island of La Palma Spain McMath Pierce Solar Telescope located at Kitt Peak National Observatory in Arizona is the world s largest solar telescope Radio telescopes Edit Nancay Radioheliographe NRH is an interferometer composed of 48 antennas observing at meter decimeter wavelengths The radioheliographe is installed at the Nancay Radio Observatory France 17 Owens Valley Solar Array OVSA is a radio interferometer operated by the New Jersey Institute of Technology originally consisting of 7 antennas observing from 1 to 18 GHz in both left and right circular polarization OVSA is located in Owens Valley California It is now called Expanded Owens Valley Solar Array EOVSA after the expansion to upgrade its control system and increase the total number of antennas to 15 18 Nobeyama Radioheliograph NoRH is an interferometer installed at the Nobeyama Radio Observatory Japan formed by 84 small 80 cm antennas with receivers at 17 GHz left and right polarization and 34 GHz operating simultaneously It continuously observes the Sun producing daily snapshots 19 Siberian Solar Radio Telescope SSRT is a special purpose solar radio telescope designed for studying solar activity in the microwave range 5 7 GHz where the processes occurring in the solar corona are accessible to observation over the entire solar disk It is a crossed interferometer consisting of two arrays of 128x128 parabolic antennas 2 5 meters in diameter each spaced equidistantly at 4 9 meters and oriented in the E W and N S directions It is located in a wooded valley separating two mountain ridges of the Eastern Sayan Mountains and Khamar Daban 220 km from Irkutsk Russia 20 Nobeyama Radio Polarimeters are a set of radio telescopes installed at the Nobeyama Radio Observatory that continuously observes the full Sun no images at the frequencies of 1 2 3 75 9 4 17 35 and 80 GHz at left and right circular polarization 21 Solar Submillimeter Telescope is a single dish telescope that observes continuously the Sun at 212 and 405 GHz It is installed at Complejo Astronomico El Leoncito in Argentina It has a focal array composed by 4 beams at 212 GHz and 2 at 405 GHz therefore it can instantaneously locate the position of the emitting source 22 SST is the only solar submillimeter telescope currently in operation Polarization Emission of Millimeter Activity at the Sun POEMAS is a system of two circular polarization solar radio telescopes for observations of the Sun at 45 and 90 GHz The novel characteristic of these instruments is the capability to measure circular right and left hand polarizations at these high frequencies The system is installed at Complejo Astronomico El Leoncito in Argentina It started operations in November 2011 In November 2013 it went offline for repairs It is expected to return to observing in January 2015 Bleien Radio Observatory is a set of radio telescopes operating near Granichen Switzerland They continuously observe the solar flare radio emission from 10 MHz ionospheric limit to 5 GHz The broadband spectrometers are known as Phoenix and CALLISTO 23 Space telescopes Edit GOES 17 captures a C2 class solar flare on May 28 2018 across different spectral bands GOES 16 ultraviolet image of a M1 1 solar flare on May 29 2020 The following spacecraft missions have flares as their main observation target Yohkoh The Yohkoh originally Solar A spacecraft observed the Sun with a variety of instruments from its launch in 1991 until its failure in 2001 The observations spanned a period from one solar maximum to the next Two instruments of particular use for flare observations were the Soft X ray Telescope SXT a glancing incidence low energy X ray telescope for photon energies of order 1 keV and the Hard X ray Telescope HXT a collimation counting instrument which produced images in higher energy X rays 15 92 keV by image synthesis WIND The Wind spacecraft is devoted to the study of the interplanetary medium Since the Solar Wind is its main driver solar flares effects can be traced with the instruments aboard Wind Some of the WIND experiments are a very low frequency spectrometer WAVES particles detectors EPACT SWE and a magnetometer MFI GOES The GOES spacecraft are satellites in geostationary orbits around the Earth that have measured the soft X ray flux from the Sun since the mid 1970s following the use of similar instruments on the Solrad satellites GOES X ray observations are commonly used to classify flares with A B C M and X representing different powers of ten an X class flare has a peak 1 8 A flux above 0 0001 W m2 RHESSI The Reuven Ramaty High Energy Solar Spectral Imager was designed to image solar flares in energetic photons from soft X rays ca 3 keV to gamma rays up to ca 20 MeV and to provide high resolution spectroscopy up to gamma ray energies of ca 20 MeV Furthermore it had the capability to perform spatially resolved spectroscopy with high spectral resolution It was decommissioned in August 2018 after more than 16 years of operation SOHO The Solar and Heliospheric Observatory is collaboration between the ESA and NASA which has been in continuous operation since December 1995 citation needed It carries 12 different instruments among them the Extreme ultraviolet Imaging Telescope EIT the Large Angle and Spectrometric Coronagraph LASCO and the Michelson Doppler Imager MDI SOHO is in a halo orbit around the earth sun L1 point TRACE The Transition Region and Coronal Explorer is a NASA Small Explorer program SMEX to image the solar corona and transition region at high angular and temporal resolution It has passband filters at 173 A 195 A 284 A 1600 A with a spatial resolution of 0 5 arc sec the best at these wavelengths SDO The Solar Dynamics Observatory is a NASA project composed of 3 different instruments the Helioseismic and Magnetic Imager HMI the Atmospheric Imaging Assembly AIA and the Extreme Ultraviolet Variability Experiment EVE As of June 2013 update it had been planned to operate for many years after it is launched into a geosynchronous earth orbit 24 needs update Hinode The Hinode spacecraft originally called Solar B was launched by the Japan Aerospace Exploration Agency in September 2006 to observe solar flares in more precise detail Its instrumentation supplied by an international collaboration including Norway the U K the U S and Africa focuses on the powerful magnetic fields thought to be the source of solar flares Such studies should shed light on the causes of this activity possibly helping to forecast future flares and thus minimize their dangerous effects on satellites and astronauts 25 needs update ACE The Advanced Composition Explorer was launched in 1997 into a halo orbit around the Earth Sun L1 point It carries spectrometers magnetometers and charged particle detectors to analyze the solar wind The Real Time Solar Wind RTSW beacon is continually monitored by a network of NOAA sponsored ground stations to provide early warning of earth bound CMEs MAVEN The Mars Atmosphere and Volatile EvolutioN MAVEN mission which launched from Cape Canaveral Air Force Station on November 18 2013 is the first mission devoted to understanding the Martian upper atmosphere The goal of MAVEN is to determine the role that loss of atmospheric gas to space played in changing the Martian climate through time The Extreme Ultraviolet EUV monitor on MAVEN is part of the Langmuir Probe and Waves LPW instrument and measures solar EUV input and variability and wave heating of the Martian upper atmosphere 26 full citation needed STEREO The Solar Terrestrial Relations Observatory is a solar observation mission consisting of two nearly identical spacecraft that were launched in 2006 Contact with STEREO B was lost in 2014 but STEREO A is still operational citation needed Each spacecraft carries several instruments including cameras particle detectors and a radio burst tracker In addition to these solar observing facilities many non solar astronomical satellites observe flares either intentionally e g NuSTAR or simply because the penetrating hard radiations coming from a flare can readily penetrate most forms of shielding Examples of large solar flares Edit Play media Short narrated video about Fermi s observations of the highest energy light ever associated with an eruption on the Sun as of March 2012 Play media Active Region 1515 released an X1 1 class flare from the lower right of the Sun on July 6 2012 peaking at 7 08 PM EDT This flare caused a radio blackout labeled as an R3 on the National Oceanic and Atmospheric Administrations scale that goes from R1 to R5 Space weather March 2012 27 Main article List of solar storms The most powerful flare ever observed was the first one to be observed 28 on September 1 1859 and was reported by British astronomer Richard Carrington and independently by an observer named Richard Hodgson The event is named the Solar storm of 1859 or the Carrington event The flare was visible to a naked eye in white light and produced stunning auroras down to tropical latitudes such as Cuba or Hawaii and set telegraph systems on fire 29 The flare left a trace in Greenland ice in the form of nitrates and beryllium 10 which allow its strength to be measured today 30 Cliver and Svalgaard 31 reconstructed the effects of this flare and compared with other events of the last 150 years In their words While the 1859 event has close rivals or superiors in each of the above categories of space weather activity it is the only documented event of the last 150 years that appears at or near the top of all of the lists The intensity of the flare has been estimated to be around X50 32 The ultra fast coronal mass ejection of August 1972 is suspected of triggering magnetic fuses on naval mines during the Vietnam War and would have been a life threatening event to Apollo astronauts if it had occurred during a mission to the Moon 33 34 In modern times the largest solar flare measured with instruments occurred on November 4 2003 This event saturated the GOES detectors and because of this its classification is only approximate Initially extrapolating the GOES curve it was estimated to be X28 35 Later analysis of the ionospheric effects suggested increasing this estimate to X45 36 This event produced the first clear evidence of a new spectral component above 100 GHz 37 Other large solar flares also occurred on April 2 2001 X20 38 October 28 2003 X17 2 and 10 39 September 7 2005 X17 38 February 17 2011 X2 40 41 42 August 9 2011 X6 9 43 44 March 7 2012 X5 4 45 46 July 6 2012 X1 1 47 On July 6 2012 a solar storm hit just after midnight UK time 48 when an X1 1 solar flare fired out of the AR1515 sunspot Another X1 4 solar flare from AR 1520 region of the Sun 49 second in the week reached the Earth on July 15 2012 50 with a geomagnetic storm of G1 G2 level 51 52 A X1 8 class flare was recorded on October 24 2012 53 There has been major solar flare activity in early 2013 notably within a 48 hour period starting on May 12 2013 a total of four X class solar flares were emitted ranging from an X1 2 and upwards of an X3 2 54 the latter of which was one of the largest year 2013 flares 55 56 Departing sunspot complex AR2035 AR2046 erupted on April 25 2014 at 0032 UT producing a strong X1 3 class solar flare and an HF communications blackout on the day side of Earth NASA s Solar Dynamics Observatory recorded a flash of extreme ultraviolet radiation from the explosion The Solar Dynamics Observatory recorded an X9 3 class flare at around 1200 UTC on September 6 2017 57 On July 23 2012 a massive potentially damaging vague solar storm solar flare coronal mass ejection and electromagnetic radiation barely missed Earth 58 59 In 2014 Pete Riley of Predictive Science Inc published a paper in which he attempted to calculate the odds of a similar solar storm hitting Earth within the next 10 years by extrapolating records of past solar storms from the 1960s to the present day He concluded that there may be as much as a 12 chance of such an event occurring 58 Flare spray EditFlare sprays are a type of eruption associated with solar flares 60 They involve faster ejections of material than eruptive prominences 61 and reach velocities of 20 to 2000 kilometers per second 62 Flare periodicity EditErich Rieger discovered with coworkers in 1984 a 154 days period in hard solar flares at least since the solar cycle 19 63 The period has since been confirmed in most heliophysics data and the interplanetary magnetic field and is commonly known as the Rieger period The period s resonance harmonics also have been reported from most data types in the heliosphere Possible causes of this solar wind resonance include influences of planetary constellations on the Sun Prediction EditCurrent methods of flare prediction are problematic and there is no certain indication that an active region on the Sun will produce a flare However many properties of sunspots and active regions correlate with flaring For example magnetically complex regions based on line of sight magnetic field called delta spots produce the largest flares A simple scheme of sunspot classification due to McIntosh or related to fractal complexity 64 is commonly used as a starting point for flare prediction 65 Predictions are usually stated in terms of probabilities for occurrence of flares above M or X GOES class within 24 or 48 hours The U S National Oceanic and Atmospheric Administration NOAA issues forecasts of this kind 66 MAG4 was developed at the University of Alabama in Huntsville with support from the Space Radiation Analysis Group at Johnson Space Flight Center NASA SRAG for forecasting M and X class flares CMEs fast CME and Solar Energetic Particle events 67 A physics based method that can predict imminent large solar flares was proposed by Institute for Space Earth Environmental Research ISEE Nagoya University 68 See also EditAurora Coronal cloud Flare star Gamma ray burst Hyder flare List of plasma physics articles List of solar storms Magnetic cloud Moreton wave Neupert effect Rieger period Superflare Supra arcade downflowsReferences Edit Kopp G Lawrence G Rottman G 2005 The Total Irradiance Monitor TIM Science Results Solar Physics 20 1 2 129 139 Bibcode 2005SoPh 230 129K doi 10 1007 s11207 005 7433 9 S2CID 44013218 What is a Solar Flare NASA Retrieved May 12 2016 Menzel Whipple and de Vaucouleurs Survey of the Universe 1970 Description of a Singular Appearance seen in the Sun on September 1 1859 Monthly Notices of the Royal Astronomical Society v20 pp13 1859 Zhu et al ApJ 2016 821 L29 The Mysterious Origins of Solar Flares Scientific American April 2006 Great Ball of Fire NASA Retrieved May 21 2012 Strong M9 9 solar flare erupted from AR 1936 The Watchers Retrieved 29 October 2021 Garner Rob 6 September 2017 Sun Erupts With Significant Flare NASA Retrieved 2 June 2019 Schrijver Carolus J Siscoe George L eds 2010 Heliophysics Space Storms and Radiation Causes and Effects Cambridge University Press p 375 ISBN 978 1107049048 Solar Flares What Does It Take to Be X Class NASA Retrieved 29 October 2021 Tandberg Hanssen Einar Emslie A Gordon 1988 Cambridge University Press ed The physics of solar flares New Study Questions the Effects of Cosmic Proton Radiation on Human Cells Archived from the original on 2008 10 06 Retrieved 2008 10 11 A New Kind of Solar Storm NASA Science nasa gov Archived from the original on 2010 03 23 R A Mewaldt et al May 2005 Space Weather Implications of the 20 January 2005 Solar Energetic Particle Event Paper at American Geophysical Union Meeting 2005 Bibcode 2005AGUSMSH32A 05M Big Bear Solar Observatory New Jersey Institute of Technology Retrieved 18 June 2017 Station de Radioastronomie de Nancay www obs nancay fr Retrieved 2 June 2019 OVSA Expanstion Project New Jersey Institute of Technology Retrieved 18 June 2017 Nobeyama Radioheliograph Nobeyama Radio Observatory Retrieved 18 June 2017 The Siberian Solar Radio Telescope ISTP SB RAS en iszf irk ru Retrieved 2 June 2019 Nobeyama Radio Polarimeters Nobeyama Radio Observatory Retrieved 18 June 2017 Gimenez de Castro C G Raulin J P Makhmutov V Kaufmann P Csota J E R Instantaneous positions of microwave solar bursts Properties and validity of the multiple beam observations Astron Astrophys Suppl Ser 140 3 December II 1999 doi 10 1051 aas 1999428 Radioastronomy FHNW soleil i4ds ch Retrieved 2 June 2019 About the SDO Mission Solar Dynamics Observatory 30 June 2007 retrieved 15 July 2013 Japan launches Sun microscope BBC 2006 09 23 Retrieved 2009 05 19 MAVEN Retrieved 2019 06 02 Extreme Space Weather Events National Geophysical Data Center Retrieved May 21 2012 A Super Solar Flare NASA 6 May 2008 Retrieved 22 December 2012 Bell Trudy E Phillips Tony 2008 A Super Solar Flare Science NASA Retrieved May 21 2012 Battersby Stephen 21 March 2005 Superflares could kill unprotected astronauts New Scientist Retrieved 8 April 2013 Cliver E W Svalgaard L 2004 The 1859 solar terrestrial disturbance and the current limits of extreme space weather activity PDF Archived from the original PDF on 2011 08 11 Retrieved 2011 04 22 Woods Tom Solar Flares PDF Retrieved 24 November 2019 Knipp Delores J Fraser Brian J Shea M A Smart D F October 25 2018 On the Little Known Consequences of the 4 August 1972 Ultra Fast Coronal Mass Ejecta Facts Commentary and Call to Action Space Weather 16 11 1635 1643 Bibcode 2018SpWea 16 1635K doi 10 1029 2018SW002024 Solar Storm and Space Weather Frequently Asked Questions NASA Mission Pages Sun Earth 19 March 2015 Retrieved November 12 2018 SOHO Hotshots Sohowww nascom nasa gov Retrieved May 21 2012 Biggest ever solar flare was even bigger than thought SpaceRef Your Space Reference SpaceRef 2004 03 15 Retrieved May 21 2012 Kaufmann Pierre Raulin Jean Pierre Gimenez de Castro C G Levato Hugo Gary Dale E Costa Joaquim E R Marun Adolfo Pereyra Pablo Silva Adriana V R Correia Emilia March 10 2004 A new solar burst spectral component emitting only in the terahertz range PDF The Astrophysical Journal 603 2 121 124 Bibcode 2004ApJ 603L 121K doi 10 1086 383186 Retrieved November 22 2014 a b BIGGEST SOLAR X RAY FLARE ON RECORD X20 NASA Retrieved May 21 2012 X 17 2 AND 10 0 FLARES NASA Retrieved May 21 2012 Hendrix Susan 2012 03 07 Valentine s Day Solar Flare video included Nasa Goddard Space Flight Center Retrieved May 21 2012 Solar flare to jam Earth s communications ABC News ABC 17 February 2011 Retrieved May 21 2012 Kremer Ken Sun Erupts with Enormous X2 Solar Flare Universe Today Retrieved May 21 2012 Fox Karen C Hendrix Susan August 9 2011 Sun Unleashes X6 9 Class Flare NASA Goddard Space Flight Center Retrieved April 10 2021 Bergen Jennifer Sun fires powerful X6 9 class solar flare Geek com Archived from the original on October 18 2012 Retrieved May 21 2012 Zalaznick Matt 8 March 2012 Gimme Some Space Solar Flare Solar Storm Strike The Norwalk Daily Voice Retrieved July 19 2012 Geomagnetic Storm Strength Increases NASA Retrieved July 9 2012 Fox Karen July 7 2012 Sunspot 1515 Release X1 1 Class Solar Flare Nasa Goddard Space Flight Center Retrieved July 14 2012 Massive X Class Solar Flare Bursts From Sun Causing Radio Blackouts VIDEO Huffington Post UK July 9 2012 Retrieved July 14 2012 Big Sunspot 1520 Releases X1 4 Class Flare With Earth Directed CME NASA July 12 2012 Retrieved July 14 2012 Solar storm rising to hit Earth today The Times of India Archived from the original on November 11 2013 Retrieved July 14 2012 Minor solar storm reaches Earth aljazeera com Retrieved July 15 2012 Space Weather Alerts and Warnings Timeline July 16 2012 NOAA Retrieved July 17 2012 Sun Unleashes Powerful Solar Flare Sky News October 24 2012 Retrieved October 24 2012 Three X class Flares in 24 Hours First Update NASA Missions Sun Earth May 13 2013 Retrieved April 10 2021 Three X class Flares in 24 Hours Third Update NASA Missions Sun Earth May 14 2013 Retrieved April 10 2021 Malik Tariq 13 May 2013 Major Solar Flare Erupts from the Sun Strongest of 2013 Space com Retrieved 13 May 2013 Two Significant Solar Flares Imaged by NASA s SDO 6 September 2017 Retrieved 6 September 2017 a b Phillips Dr Tony July 23 2014 Near Miss The Solar Superstorm of July 2012 NASA Retrieved July 26 2014 Staff April 28 2014 Video 04 03 Carrington class coronal mass ejection narrowly misses Earth NASA Retrieved July 26 2014 Morimoto Tarou Kurokawa Hiroki Effects of Magnetic and Gravity forces on the Acceleration of Solar Filaments and Coronal Mass Ejections PDF Archived from the original PDF on 2011 06 11 Retrieved 2009 10 08 Tandberg Hanssen E Martin Sara F Hansen Richard T March 1980 Dynamics of flare sprays Solar Physics 65 2 357 368 Bibcode 1980SoPh 65 357T doi 10 1007 BF00152799 ISSN 0038 0938 S2CID 122385884 NASA Visible Earth Biggest Solar Flare on Record nasa gov 15 May 2001 Rieger E Share G H Forrest D J Kanbach G Reppin C Chupp E L 1984 A 154 day periodicity in the occurrence of hard solar flares Nature 312 5995 623 625 Bibcode 1984Natur 312 623R doi 10 1038 312623a0 S2CID 4348672 McAteer James 2005 Statistics of Active Region Complexy The Astrophysical Journal 631 2 638 Bibcode 2005ApJ 631 628M doi 10 1086 432412 Wheatland M S 2008 A Bayesian approach to solar flare prediction The Astrophysical Journal 609 2 1134 1139 arXiv astro ph 0403613 Bibcode 2004ApJ 609 1134W doi 10 1086 421261 S2CID 10273389 Space Weather Prediction Center NOAA Retrieved August 1 2012 Falconer 2011 A tool for empirical forecasting of major flares coronal mass ejections and solar particle eventsfrom a proxy of active region free magnetic energy PDF Kusano Kanya Iju Tomoya Bamba Yumi Inoue Satoshi July 31 2020 A physics based method that can predict imminent large solar flares Science 369 6503 587 591 Bibcode 2020Sci 369 587K doi 10 1126 science aaz2511 PMID 32732427 External links EditWikimedia Commons has media related to Solar flares Real time space weather on the iPhone iPad and Android from 150 data streams and 19 institutions Live Solar Images and Data Site Includes x ray flare geomagnetic space weather information detailing current solar events Solar Cycle 24 and VHF Aurora Website www solarcycle24 com Solar Weather Site Current Solar Flare and geomagnetic activity in dashboard style www solar flares info Archived 2021 02 25 at the Wayback Machine STEREO Spacecraft Site BBC report on the November 4 2003 flare NASA SOHO observations of flares The Sun Kings lecture by Dr Stuart Clark on the discovery of solar flares given at Gresham College 12 September 2007 available as a video or audio download as well as a text file NASA Astronomy Picture of the Day An X Class Flare Region on the Sun 6 November 2007 Sun trek website An educational resource for teachers and students about the Sun and its effect on the Earth NASA Carrington Super Flare NASA May 6 2008 Archive of the most severe solar storms Animated explanation of Solar Flares from the Photosphere Archived 2015 11 16 at the Wayback Machine University of South Wales 1 min 35 sec Mini documentary How big are solar flares prominences A simplified explanation of the size of solar flares prominences as compared to Earth The Most Powerful Solar Flares Ever Recorded spaceweather com X9 summary Most Energetic Flares since 1976 X5 7 details Davis Chris Tracking the X Flare Backstage Science Brady Haran Study solar flares with Sunspot Data Retrieved from https en wikipedia org w index php title Solar flare amp oldid 1052842849, wikipedia, wiki, book,

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