Solar Energetic Particles
- Solar Energetic Particles
Solar Energetic Particles 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.
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
ee also
*Solar cosmic rays
*Coronal Mass Ejection
*Solar Flare
*Solar proton event
External links
* [http://solarphysics.livingreviews.org/open?pubNo=lrsp-2006-2&page=articlesu15.html Solar Energetic Particles (Rainer Schwenn)]
* [http://helios.gsfc.nasa.gov/sep.html NASA]
Wikimedia Foundation.
2010.
Look at other dictionaries:
Solar proton event — A 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… … Wikipedia
Solar Sentinels — The Solar Sentinels is a space mission to study the Sun during its solar maximum, the last before the beginning of the Orion program. Six spacecraft will be launched, which will separate into three groups. The Solar Sentinels are part of the NASA … Wikipedia
Solar variation — Solar variations are changes in the amount of solar radiation emitted by the Sun. There are periodic components to these variations, the principal one being the 11 year solar cycle (or sunspot cycle), as well as aperiodic fluctuations. Solar… … Wikipedia
Solar Probe Plus — Artist s concept of NASA s Solar Probe Plus Operator NASA / Applied Physics Laboratory Mission type Orbiter … Wikipedia
Solar flare — A solar flare is a violent explosion in a star s (like the Sun s) atmosphere releasing as much energy as 6 times; 1025 Joules.cite journal last=Kopp first=G. coauthors=Lawrence, G and Rottman, G. year=2005… … Wikipedia
Solar Orbiter — The Solar Orbiter (also called SOLO) is a Sun observing satellite, in development by the European Space Agency. It is to be launched on an Atlas 5Fact|date=September 2008 from the Kennedy Space Center in Florida, USA in May 2015. It will perform… … Wikipedia
solar flare — Astron. flare (def. 22). [1935 40] * * * Sudden intense brightening of a small part of the Sun s surface, often near a sunspot group. Flares develop in a few minutes and may last several hours, releasing intense X rays and streams of energetic… … Universalium
Solar cycle — The solar cycle, or the solar magnetic activity cycle, is the main source of periodic variation of all solar phenomena driving variations in space weather. [ [http://www7.nationalacademies.org/ssb/SSB Space weather97.pdf Space Weather: A Research … Wikipedia
Energetic neutral atom — ENAs redirects here. For other uses, see Enas (disambiguation). Neutral Atom Imaging redirects here. For other uses, see Atom (disambiguation). ENA images of the fluctuation of Earth s ring current during July 15–16, 2000 geomagnetic storm made… … Wikipedia
Solar wind — For other uses, see Solar wind (disambiguation). The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of … Wikipedia
