TIME HISTORY:
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Abstract
Along with the stable inner proton belt, temporal variations of the 1-15 MeV protons at L=2.5-3.5 have been
reported, with intensity increases and decreases registered during and after strong magnetic storms.
As a source of this additional proton population, energetic plasmasheet ions and solar protons were considered.
For the explanation of the origin of the additional proton belt the models of resonant acceleration and radial
particle injection were introduced, with strong electric field induced by the compression of the magnetosphere
as a driver.
Our study presents experimental evidences that creation and destruction of solar proton belts in the inner
magnetosphere may be produced by the fast shifts of the proton penetration boundary without additional acceleration
and injection.
Our conclusions are based on the solar protons and ions measurements by low altitude polar orbiter Coronas-F
during October - November 2003 magnetic storms events. Several times creation and destruction of solar cosmic ray
belts were observed during this interval. Compression of the magnetosphere make possible direct penetration of the
solar protons deep into the magnetosphere.
Inside the proton penetration boundary particle trajectories are open and previously trapped particles are free
to escape. During magnetosphere reconfiguration when penetration boundary shifts away from the Earth, solar protons
and alpha particles with relatively low magnetic drift velocity became stable trapped. Therefore discussed effect
differs from the SC induced solar proton injection events by the restricted energy range of the trapped protons.
Solar proton trapping into the inner magnetosphere (L=2-4) have been observed previously during several magnetic bays.
Accepted explanations were based on resonant particle radial injection during SC. SC-type injection was registered
by CRRES satellite particle detectors, receive theoretical explanation and reproduced by computer modeling.
This mechanism demand large amplitude of the SC impulse for deep injection into the inner magnetosphere and is
restricted for the solar protons with energies >15 MeV.
SCR belt created by SC injection might be destroyed during the main phase by inward motion of the SCR penetration
boundary as described in present paper.
In a present paper we propose new type of SCR trpping into the inner magnetosphere supported by the analysis of the
experimental data. The trapping of solar protons (ions) which penetrate into the inner magnetosphere during the main
phase occurs as a result of the transition from the open to the closed drift paths during the recovery of the
magnetosphere configuration without additional acceleration and injection.
Injection effect was recorded, but it did not play the major role.
Considered mechanism works effectively only if the impulsive recovery of the magnetosphere configuration was rather
fast as compared with the particle magnetic drift period. It imply restriction on the energy of the protons and
alpha particles. Particles with the energy larger than 5-15 MeV/nuclon might be trapped only in a rare occasions.
Following foundings might be listed:
1. Solar protons with energy 1 MeV and higher after earthward shift of the penetration boundary might be trapped
during the boundary retreat, creating solar cosmic ray belt on L= 2 - 4.
2. In some cases 2 or even 3 SCB can be created.
3. In new SCB stable trapping condition became established quickly. The flux of precipitation protons decrease
exponentially as N=No exp(-kt) , where t= 1.15 hours.
4. After the storms, position and intensity of the SCB might remains constant as long as 20 days.
5. SCB can be destroyed by the new strong enough magnetic storm.
6. During magnetic storm SCB may be shifted earthward for 0.1 - 0.2 L.
7. Energy spectrum of the protons in SCB decreases steeply from 4-10 MeV. Protons and alpha particles with E > 4 ÌýÂ
were recorded only occasionally and with small intensity. The efficiency of the trapping decreases with the energy
as P ~ E-2