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| Titel |
Particle Acceleration at Interplanetary Discontinuities |
| VerfasserIn |
Harald Kucharek, Charles Farrugia, Mark Popecki, Berndt Klecker, Kristin Simunac, Antoinette Galvin |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093929
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| Publikation (Nr.) |
 EGU/EGU2014-9149.pdf |
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| Zusammenfassung |
| Interplanetary discontinuities, long-duration Alfvenic fluctuations and transient structures
such as shocks, stream interfaces (SIs), and coronal mass ejections (CME’s) are considered to
be prime candidates for accelerating particles in space and are therefore also responsible for
producing the suprathermal particle population. The spectral slope of the phase space density
of of the suprathermal particle population has been reported to cluster around v-5 but may
vary significantly over longer time periods [1]. It is unclear, however, how such as slope is
generated and how these interplanetary structures contribute. In a statistical study for
the years 2007-2009 we investigate shocks, SIs (alone or combined) as well as
CME’s with respect to ion acceleration efficiency and the formation of suprathermal
tails in the particle distribution. This depends on solar wind plasma conditions (for
example, the presence of Alfvenic fluctuations) and on the acceleration process,
the shock geometry, and on the intensity of the source population. Pickup helium
(He+) is an excellent tracer for interplanetary discontinuities. It is abundant at these
plasma discontinuities because it is preferentially accelerated compared to solar wind
ions (including He+2). This study shows that all of these discontinuities produce a
suprathermal population with varying number density and spectral slope. Depending on the
discontinuity/structure type, the solar wind plasma conditions, the data accumulation time,
and the location within the discontinuity, the slopes of the suprathermal tails are
shown to vary between v-3 and v-7. This large range is most likely due to the
fact that the plasma at these discontinuities has not yet reached stationary state
conditions. This conjecture can be confirmed by measurements and simulated particle
distributions.
[1] Gloeckler et al., : AIP Conf. Proc. 1436, 136 (2012); doi: 10.1063/1.4723601 |
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