 |
| Titel |
Cluster Multi-Scale Observation of MHD Shock-like Events in the Near-Earth Magnetotail |
| VerfasserIn |
Bertalan Zieger, Alessandro Retino, Rumi Nakamura, Wolfgang Baumjohann |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250041525
|
|
|
|
|
|
| Zusammenfassung |
| We re-analyze the October 27, 2007 Cluster event discussed in previous studies from
a new aspect. This event occurred in the near-Earth flow braking region around
XGSM= -10 RE, where a significant deceleration of the Earthward flow could be
detected by two Cluster spacecraft (C1 and C4). The plasma flow velocity was
obtained from the EÃB plasma drift velocity using high resolution electric field data
and also from the timing analysis of two closely spaced spacecraft (C3 and C4).
We argue that some of the observed thin structures associated with unusually high
current density could be interpreted as slow-mode MHD shock-like structures.
The phase velocity of Earthward propagating slow magnetosonic MHD waves was
estimated to be as small as ~77 km/s for the observed angle between the magnetic
field and the normal of the discontinuity (θBn = 67-), whereas the corresponding
fast magnetosonic velocity (~1230 km/s) was found to be much higher. Thus a
slow-mode shock is not unexpected where the plasma flow velocity abruptly drops from
400-500 km/s to almost zero. The rotation of the magnetic field vector across the
discontinuity also supports the slow-mode shock interpretation. Unfortunately, the
total pressure could not be calculated for this case due to the lack of appropriate
plasma data. We suggest that MHD shock-like structures may play an important role
in the particle acceleration in the near-Earth flow braking region, which needs to
be confirmed by more detailed case studies of Cluster or Themis observations. |
|
|
|
|
|
|