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| Titel |
Can upstream ion events at the Lagrangian point L1 mimic ions accelerated at an interplanetary shock wave? |
| VerfasserIn |
George C. Anagnostopoulos, Mιchael Maragakis, Efthymios Vassiliadis |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077236
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| Zusammenfassung |
| Changes in plasma, magnetic field and energetic ion observations at Libration Point L1
(~220 Re) are important for space whether research. However, short-lived (from some
minutes to a few hours) ion intensity enhancements at L1 have been attributed to various
sources and acceleration sites: interplanetary shock acceleration, acceleration at Earth’s bow
shock, leakage from Earth’s magnetosphere etc. The scope of this study is to examine to
which extent ion events originating from the Earth’s magnetosphere environment
could mimic ion events propagating up to L1 point after acceleration at (distant)
interplanetary shock waves. For this reason we performed a statistical study and
compared ion events observed almost simultaneously by the Geotail spacecraft near the
Earth’s bow shock and by ACE moving around the Libration point L1. Due to drastic
changes of several parameters between the two sites, we found that at around the point
L1, the ACE ion events show a strong spectrum with an average spectral index
as low as γA = 2.1 (for a power law spectrum) at the level of 200 keV, while the
average spectral index for the corresponding ion events observed by Goetail was
found to be γG = 5.4. We infer that a short duration ion event with a hard “solar” /
“interplanetary” type energy spectrum can originate from the Earth’s magnetosphere,
and, that, therefore, these results should be seriously taken into account in space
weather prediction research. More detailed information on the varying features of
travelling ions and electrons from the bow shock to far distances are important as
regards the problem of their origin and are also presented and discussed in the paper. |
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