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| Titel |
Particle acceleration in shock-shock interaction: model to data comparison |
| VerfasserIn |
H. Hietala, A. Sandroos, R. Vainio |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250068804
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| Zusammenfassung |
| On August 10, 1998, an interplanetary (IP) shock hit the bow shock of the Earth. The
quasi-radial interplanetary magnetic field configuration and the advantageously located
spacecraft made it possible to analyze in detail the different particle acceleration processes as
the shocks approached each other.
After crossing a tangential discontinuity (TD), the spacecraft moved into a flux tube that
was filled with a seed population of energetic particles accelerated by the IP shock
(phase 1). Since ACE near the L1 point was magnetically connected to the IP shock
but not to the bow shock, its measurements could be used to characterize the seed
population. Flat flux intensity profiles were observed during the 6–7 hours from the TD
crossing to the IP shock crossing. No ‘shock-spike’ could be identified at the crossing.
Wind, located at X ~ 78RE, observed several particle bursts coming from the bow
shock direction during the first part of the event (phase 2). Later, Wind became
continuously connected to both shocks, and measured an increasing flux as well as two
counter-streaming populations until the IP shock crossing (phase 3). Geotail was
located at the edge of the Earth’s foreshock and continuously connected to both
shocks. It recorded the highest peak intensity at the IP shock crossing. Furthermore,
immediately after the crossing Geotail observed a burst of very high energy particles
propagating sunwards (phase 4). Based on the velocity dispersion of the burst and
the analysis of the geometry of the two shocks, Hietala et al. [2011] claimed that
these particles had been released from the magnetic trap between the shocks as they
collided.
In the present study we use a global 2.5D test-particle simulation to further
investigate particle acceleration in this event. We concentrate on the last hour of the
shock-shock interaction, when the IP shock crossed the spacecraft and acceleration phases
(3) and (4) were observed. The simulation results confirm that the peak intensity
around Geotail’s location occurs after the shock crossing due to the shock-shock
interaction.
Hietala et al. (2011), J. Geophys. Res. 116, A10105. |
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