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Flares occur in active regions often 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. Solar flares occur in a power-law spectrum of magnitudes; an energy release of typically 10 20 joules of energy suffices to produce a clearly observable event, while a major event can emit up to 10 25 joules.

Associated with solar flares are flare sprays. The frequency of occurrence of solar flares varies with the year solar cycle. It can range from several per day during solar maximum to less than one every week during solar minimum. Additionally, more powerful flares are less frequent than weaker ones.

For example, Xclass severe flares occur on average about eight times per cycle, whereas M1-class minor flares occur on average about times per cycle. Erich Rieger discovered with coworkers in an approximately day period in the occurrence of gamma-ray emitting solar flares at least since the solar cycle The period’s resonance harmonics also have been reported from most data types in the heliosphere.

The duration of a solar flare depends heavily on the wavelength of the electromagnetic radiation used in its calculation. This is due to different wavelengths being emitted through different processes and at different heights in the Sun’s atmosphere.

A common measure of flare duration is the full width at half maximum FWHM time of soft X-ray flux within the wavelength bands 0. The FWHM time spans from when a flare’s flux first reaches halfway between its maximum flux and the background flux and when it again reaches this value as the flare decays. Using this measure, the duration of a flare ranges from approximately tens of seconds to several hours with a median duration of approximately 6 and 11 minutes in the 0.

Solar flares lasting longer than approximately 30 minutes are regarded as long duration events LDE. After the eruption of a solar flare, post-eruption loops made up of hot plasma begin to form across the neutral line separating regions of opposite magnetic polarity near the flare’s source.

These loops extend from the photosphere up into the corona and form along the neutral line at increasingly greater distances from the source as time progresses. In sufficiently powerful flares, typically of C-class or higher, the loops may combine to form an elongated arch-like structure known as a post-eruption arcade. These structures may last anywhere from multiple hours to multiple days after the initial flare.

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.

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.

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 10 9 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. The strength of an event within a class is noted by a numerical suffix ranging from 1 up to, but excluding, 10, [18] which is also the factor for that event within the class. This system was originally devised in and included only the letters C, M, and X. These letters were chosen to avoid confusion with other optical classification systems.

The A and B classes would later be added in the s as instruments became more sensitive to weaker flares. Around the same time, the backronym moderate for M-class flares and extreme for X-class flares began to be used. An earlier flare classification was based on H-alpha 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. A flare then is classified taking S or a number that represents its size and a letter that represents its peak intensity, v. X-rays and extreme ultraviolet radiation emitted by solar flares are absorbed by the daylight side of Earth’s atmosphere and do not reach the Earth’s surface.

Therefore, solar flares pose no direct danger to humans on Earth. However, this absorption of high-energy electromagnetic radiation can temporarily increase the ionization of the upper atmosphere, which can interfere with short-wave radio communication, and can temporarily heat and expand the Earth’s outer atmosphere. This expansion can increase drag on satellites in low Earth orbit , which can lead to orbital decay over time.

The temporary increase in ionization of the daylight side of Earth’s atmosphere, in particular the D layer of the ionosphere , can interfere with short-wave radio communications that rely on its level of ionization for skywave propagation.

Skywave, or skip, refers to the propagation of radio waves reflected or refracted off of the ionized ionosphere. When ionization is higher than normal, radio waves get degraded or completely absorbed by losing energy from the more frequent collisions with free electrons. The level of ionization of the atmosphere correlates with the strength of the associated solar flare in soft X-ray radiation.

The increased ionization of the D and E layers of the ionosphere caused by large solar flares increases the electrical conductivity of these layers allowing for the flow of electric currents. These ionospheric currents induce a magnetic field which can be measured by ground-based magnetometers.

This phenomenon is known as a magnetic crochet or solar flare effect SFE. For astronauts in space, [ where? Of much more concern for astronauts is the particle radiation associated with solar particle events. 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. Solar flares were first observed by Richard Carrington and Richard Hodgson independently on 1 September by projecting the image of the solar disk produced by an optical telescope through a broad-band filter.

It was an extraordinarily intense white light flare , a flare emitting a high amount of light in the visual spectrum. Other passband filters are also used. 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 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. Because the Earth’s atmosphere absorbs much of the electromagnetic radiation emitted by the Sun with wavelengths shorter than nm, space-based telescopes allowed for the observation of solar flares in previously unobserved high-energy spectral lines. Since the s, the GOES series of satellites have been continuously observing the Sun in soft X-rays, and their observations have become the standard measure of flares, diminishing the importance of the H-alpha classification.

Additionally, space-based telescopes allow for the observation of extremely long wavelengths—as long as a few kilometres—which cannot propagate through the ionosphere. The most powerful flare ever observed is thought to be the flare associated with the Carrington Event. Using these magnetometer readings, its soft X-ray class has been estimated to be greater than X In modern times, the largest solar flare measured with instruments occurred on 4 November This event saturated the GOES detectors, and because of this its classification is only approximate.

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 [43] is commonly used as a starting point for flare prediction. The U. They are also a popular doomsday scenario in disaster films, where their effects on Earth are often greatly exaggerated. From Wikipedia, the free encyclopedia. Eruption of electromagnetic radiation in the atmosphere of the Sun. For the class of stars that undergo similar phenomena, see flare star.

For the rose variety, see Rosa ‘Sun Flare’. Heliospheric current sheet. Plasma Flux tube Magnetic reconnection Particle acceleration Nuclear physics. Interplanetary medium. Solar phenomena. See also: Coronal loop. Further information: Solar observation. Further information: Solar radio emission. See also: List of solar storms. Retrieved 11 November Retrieved May 12, Archived from the original PDF on Retrieved March Solar Physics.

Bibcode : SoPh ISSN S2CID Retrieved 20 November Bibcode : Natur. Khalid , People spent much less time watching gaming streams this spring, report says By K. Holt , Bonifacic , People spent much less time watching gaming streams this spring, report says Facebook Gaming saw a far bigger decline than Twitch and YouTube Gaming, according to Streamlabs and Stream Hatchet.

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