 |
| Titel |
A quantitative model of the planetary Na+ contribution to Mercury’s magnetosphere |
| VerfasserIn |
D. C. Delcourt, S. Grimald, F. Leblanc, J.-J. Berthelier, A. Millilo, A. Mura, S. Orsini, T. E. Moore |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 21, no. 8 ; Nr. 21, no. 8, S.1723-1736 |
| Datensatznummer |
250014674
|
| Publikation (Nr.) |
 copernicus.org/angeo-21-1723-2003.pdf |
|
|
|
|
|
| Zusammenfassung |
We examine the
circulation of heavy ions of planetary origin within Mercury’s magnetosphere.
Using single particle trajectory calculations, we focus on the dynamics of
sodium ions, one of the main species that are ejected from the planet’s
surface. The numerical simulations reveal a significant population in the
near-Mercury environment in the nightside sector, with energetic (several keV)
Na + densities that reach several tenths cm-3 at planetary
perihelion. At aphelion, a lesser (by about one order of magnitude) density
contribution is obtained, due to weaker photon flux and solar wind flux. The
numerical simulations also display several features of interest that follow
from the small spatial scales of Mercury’s magnetosphere. First, in contrast
to the situation prevailing at Earth, ions in the magnetospheric lobes are
found to be relatively energetic (a few hundreds of eV), despite the low-energy
character of the exospheric source. This results from enhanced centrifugal
acceleration during E × B transport over the polar cap. Second,
the large Larmor radii in the mid-tail result in the loss of most Na + into the
dusk flank at radial distances greater than a few planetary radii. Because
gyroradii are comparable to, or larger than, the magnetic field variation
length scale, the Na + motion is also found to be non-adiabatic throughout most
of Mercury’s equatorial magnetosphere, leading to chaotic scattering into the
loss cone or meandering (Speiser-type) motion in the near-tail. As a direct
consequence, a localized region of energetic Na + precipitation develops at the
planet’s surface. In this region which extends over a wide range of
longitudes at mid-latitudes ( ~ 30°–40°), one may expect additional
sputtering of planetary material.
Key words. Magnetospheric physics
(planetary magnetospheres) – Space plasma physics (charged particle motion
and acceleration; numerical simulation studies) |
| |
|
| Teil von |
|
|
|
|
|
|
|
|