 |
| Titel |
Relativistic E > 0.6, > 2.0 and > 4.0 MeV electron acceleration and HILDCAAs |
| VerfasserIn |
Rajkumar Hajra, Bruce Tsurutani, Ezequiel Echer, Walter Gonzalez |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092212
|
| Publikation (Nr.) |
 EGU/EGU2014-6541.pdf |
|
|
|
|
|
| Zusammenfassung |
| Relativistic (E ≥ 0.6 MeV) electrons at geosynchronous orbit during solar cycle 23 are
well-correlated with the intervals of High-Intensity, Long-Duration, Continuous AE Activity
(HILDCAA) events. The response of the energetic electrons to HILDCAAs is found to vary
with solar cycle phase. The initial electron fluxes are lower for events occurring during the
ascending and solar maximum (AMAX) phases than for events occurring during the
descending and solar minimum (DMIN) phases. The flux increases for the DMIN-phase
events are > 50% larger than for the AMAX-phase events. It is concluded that electrons are
accelerated to relativistic energies most often and most efficiently during the DMIN-phases of
the solar cycle. We propose two possible solar UV-related mechanisms to explain this solar
cycle effect. Enhanced E > 0.6 MeV electron fluxes at geosynchronous orbit are first
detected ~1 day after the statistical onset of HILDCAAs, E > 2.0 MeV electrons
after ~11 -2 days, and E > 4.0 MeV electrons after ~21 -2 days. As expected from
the above, for short-duration (D -¤ 3 days) HILDCAA events, there are no E >
4.0 MeV electron enhancements. For longer-duration (D > 3 days) HILDCAAs,
the E > 0.6 MeV and E > 2.0 MeV fluxes appear to reach saturation values of
~3-4x105 and 5-6x103 cm-2 s-1 sr-1 respectively. The above results are consistent
with the general concepts of theoretical models of relativistic electron acceleration
(and losses). Relativistic electrons are bootstrapped from high energy electrons: the
E > 0.6 MeV electrons are accelerated from HILDCAA-injected E ~100 keV
electrons, the E > 2.0 MeV electrons from the E > 0.6 MeV electron population, and
consequently the E > 4.0 MeV electrons are accelerated from the E > 2.0 MeV population,
etc. Relativistic electron acceleration and decay time scales will be provided for
wave-particle investigators to attempt to match their models to empirically derived values. |
|
|
|
|
|
|