 |
| Titel |
Electron-cylotron maser radiation from electron holes: upward current region |
| VerfasserIn |
R. A. Treumann, W. Baumjohann, R. Pottelette |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 29, no. 10 ; Nr. 29, no. 10 (2011-10-25), S.1885-1904 |
| Datensatznummer |
250017113
|
| Publikation (Nr.) |
 copernicus.org/angeo-29-1885-2011.pdf |
|
|
|
|
|
| Zusammenfassung |
| Electron holes are suggested to be an important source for generation of
electron-cyclotron maser radiation. We demonstrate that electron holes
generated in a ring-horseshoe distribution in the auroral-kilometric
radiation source region have the capacity to emit band-limited radiation. The
radiation is calculated in the proper frame of a circular model hole and
shown to be strictly perpendicular in this frame. Its bandwidth under auroral
conditions is of the order of ~1 kHz, which is a reasonable value. It
is also shown that much of the drift of fine structure in the radiation can
be interpreted as Doppler shift. Estimates based on data are in good
agreement with theory. Growth and absorption rates have been obtained for the
emitted radiation. However, the growth rate of a single hole obtained under
conservative conditions is small, too small for reproducing the observed fine
structure flux. Trapping of radiation inside the hole for the hole's lifetime
helps amplifying the radiation additionally but introduces other problems.
This entire set of questions is discussed at length and compared to radiation
from the global horseshoe distribution. The interior of the hole produces a
weak absorption at slightly higher frequency than emission. The absorptivity
is roughly two orders of magnitude below the growth rate of the radiation
thus being weak even when the emission and absorption bands overlap.
Transforming to the stationary observer's frame it is found that the
radiation becomes oblique against the magnetic field. For approaching holes
the radiated frequencies may even exceed the local electron cyclotron
frequency. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|