 |
| Titel |
Cluster observations of sub-proton scale magnetic holes in Earth's plasma sheet |
| VerfasserIn |
Torbjorn Sundberg, David Burgess, Christopher T. Haynes |
| Konferenz |
EGU General Assembly 2014
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093748
|
| Publikation (Nr.) |
 EGU/EGU2014-8777.pdf |
|
|
|
|
|
| Zusammenfassung |
| Spacecraft observations from Earth's plasma sheet have shown that magnetic holes with high electron perpendicular temperature anisotropy can develop when the magnetotail is in a relaxed (dipolarized) state. As these appear in environments that are stable to the mirror-mode instability and they often have cross-field scale-sizes equivalent to or shorter than the local proton gyro radius, these magnetic holes cannot exclusively be explained in terms of a standard mirror-mode growth from an anisotropic proton distribution.
We here investigate a series of such events observed by the Cluster spacecraft and assess whether they may in be explained in terms of electron-vortex magnetic holes (EVMH) – a formation scenario where turbulent depressions in the magnetic field interact with the local electron population, leading to a self-consistent growth of magnetic holes by trapped or quasi-trapped electrons with high energies and large pitch angles. Some of the observable features of EVMH are that they should be close to circularly symmetric with non-gyrotropic electron distributions, and there should be a clear relation between the characteristic electron energy and their cross-field scale-size. In addition to evaluating these criteria, we also attempt to constrain the scale-size of the observed magnetic holes, and we show that they in fact can be highly localized in both the direction parallel and perpendicular to the local magnetic field. |
|
|
|
|
|
|