Solar Energetic Particles
Encyclopedia
Solar Energetic Particles (SEP) are high-energy particles coming from the Sun which had been first observed in the early 1940s. They consist of protons, electrons and heavy ions with energy ranging from a few tens of keV
to GeV
(the fastest particles can reach speed up to 80% of the speed of light). They are of particular interest and importance because they can endanger life in outer space (especially particles above 40 MeV
). Solar Energetic Particles (SEPs) can originate from two processes: energetization at a solar flare
site or by shock waves
associated with Coronal Mass Ejection
(CMEs). However, only about 1% of the CMEs produce strong SEP events.
SEPs are also of interest because they provide a good sample of solar material. Despite the nuclear fusion occurring in the core, the majority of solar material is representative of the material which formed our solar system. By studying the isotopic composition of SEPs, scientists can obtain an indirect measurement of the material which formed the solar system, and thus learn about its origins.
Two main mechanisms of acceleration are possible: diffusive shock acceleration (DSA, sometimes referred as first-order Fermi acceleration
) or shock-drift mechanism. SEPs can be accelerated to energies of several tens of MeV within 5-10 solar radii (0.05% of the Sun-Earth distance) and can reach Earth in a matter of a few hours after a flare or an ejection. This makes prediction and warning of SEP events quite challenging. The seed population and composition of these SEP events is also an active area of research.
Kev
Kev can refer to:*Kev Hawkins, a fictional character.*Kevin, a given name occasionally shortened to "Kev".*Kiloelectronvolt, a unit of energy who symbol is "KeV".* Krefelder Eislauf-VereinKEV can refer to:...
to GeV
GEV
GEV or GeV may stand for:*GeV or gigaelectronvolt, a unit of energy equal to billion electron volts*GEV or Grid Enabled Vehicle that is fully or partially powered by the electric grid, see plug-in electric vehicle...
(the fastest particles can reach speed up to 80% of the speed of light). They are of particular interest and importance because they can endanger life in outer space (especially particles above 40 MeV
MEV
MeV and meV are multiples and submultiples of the electron volt unit referring to 1,000,000 eV and 0.001 eV, respectively.Mev or MEV may refer to:In entertainment:* Musica Elettronica Viva, an Italian musical group...
). Solar Energetic Particles (SEPs) can originate from two processes: energetization at a solar flare
Solar flare
A solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...
site or by shock waves
Shock Waves
Shock Waves, , is a 1977 horror movie written and directed by Ken Wiederhorn...
associated with Coronal Mass Ejection
Coronal mass ejection
A coronal mass ejection is a massive burst of solar wind, other light isotope plasma, and magnetic fields rising above the solar corona or being released into space....
(CMEs). However, only about 1% of the CMEs produce strong SEP events.
SEPs are also of interest because they provide a good sample of solar material. Despite the nuclear fusion occurring in the core, the majority of solar material is representative of the material which formed our solar system. By studying the isotopic composition of SEPs, scientists can obtain an indirect measurement of the material which formed the solar system, and thus learn about its origins.
Two main mechanisms of acceleration are possible: diffusive shock acceleration (DSA, sometimes referred as first-order Fermi acceleration
Fermi acceleration
Fermi acceleration , sometimes referred to as diffusive shock acceleration , is the acceleration that charged particles undergo when being repeatedly reflected, usually by a magnetic mirror. This is thought to be the primary mechanism by which particles gain non thermal energies in astrophysical...
) or shock-drift mechanism. SEPs can be accelerated to energies of several tens of MeV within 5-10 solar radii (0.05% of the Sun-Earth distance) and can reach Earth in a matter of a few hours after a flare or an ejection. This makes prediction and warning of SEP events quite challenging. The seed population and composition of these SEP events is also an active area of research.
See also
- Solar cosmic rays
- Coronal Mass EjectionCoronal mass ejectionA coronal mass ejection is a massive burst of solar wind, other light isotope plasma, and magnetic fields rising above the solar corona or being released into space....
- Solar FlareSolar flareA solar flare is a sudden brightening observed over the Sun surface or the solar limb, which is interpreted as a large energy release of up to 6 × 1025 joules of energy . The flare ejects clouds of electrons, ions, and atoms through the corona into space. These clouds typically reach Earth a day...
- Solar proton eventSolar proton eventA Solar proton event occurs when protons emitted by the Sun become accelerated to very high energies either close to the Sun during a solar flare or in interplanetary space by the shocks associated with coronal mass ejections. These high energy protons cause several effects. They can penetrate the...