 |
| Titel |
Europa's Alfvén wing: shrinkage and displacement influenced by an induced magnetic field |
| VerfasserIn |
M. Volwerk, K. Khurana, M. Kivelson |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 25, no. 4 ; Nr. 25, no. 4 (2007-05-08), S.905-914 |
| Datensatznummer |
250015828
|
| Publikation (Nr.) |
 copernicus.org/angeo-25-905-2007.pdf |
|
|
|
|
|
| Zusammenfassung |
| The Galileo magnetometer data are used to investigate the structure of the
Alfvén wing during three flybys of Europa. The presence of an induced
magnetic field is shown to shrink the cross section of the Alfvén wing and
offset it along the direction radial to Jupiter. Both the shrinkage and the
offset depend on the strength of the induced field. The entry and exit points
of the spacecraft into and out of the Alfvén wings are modeled to determine
the angle between the wings and the background magnetic field. Tracing of the
Alfvén characteristics in a model magnetic field consisting of Jupiter's
background field and an induced field in Europa produces an offset and
shrinking of the Alfvén wing consistent with the geometric modeling. Thus
we believe that the Alfvén wing properties have been determined correctly.
The Alfvén wing angle is directly proportional to the local Alfvén
velocity, and is thus a probe for the local plasma density. We show that the
inferred plasma density can be understood in terms of the electron density
measured by the plasma wave experiment. When Europa is located in the Jovian
plasma sheet the derived mass-per-charge exceeds the previous estimates,
which is a result of increased pickup of sputtered ions near the moon. The
estimated rate of O2+ pickup agrees well with the results from numerical
models. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|