 |
| Titel |
Cold Ion Escape from the Martian Ionosphere |
| VerfasserIn |
Markus Fränz, Eduard Dubinin, Yong Wei, David Morgan, Stas Barabash, Rickard Lundin, Andrei Fedorov |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250075401
|
|
|
|
|
|
| Zusammenfassung |
| It has always been challenging to observe the flux of ions with energies of less than 10eV
escaping from the planetary ionospheres. We here report on new measurements of the
ionospheric ion flows at Mars by the ASPERA-3 experiment on board Mars Express. We first
use support from the MARSIS radar experiment for some orbits with fortunate observation
geometry. Here we have observed a transterminator flow of O+ and O2+ ions with a
super-sonic velocity of around 5km/s and fluxes of 0.8 -
109/cm2s. If we assume a symmetric
flux around the terminator this corresponds to an ion flow of 3.1 ± 0.5 Ã 1025-s half of which
is expected to escape from Mars (Fraenz et al, Plan.Space Sci., 2010). This escape
flux is significantly higher than previously observed on the tailside of Mars, we
discuss possible reasons for the difference. Since 2008 the MARSIS radar does
nightside local plasma density measurements which often coincide with ASPERA-3
measurements. In a new analysis of the combined nightside datasets we show that
the main escape channel is along the shadow boundary on the tailside of Mars.
At a distance of half a Martian radius the flux settles at a constant value which
indicates that about half of the transterminator ionospheric flow escapes from the
planet.
Possible mechanism to generate this flux can be the ionospheric pressure gradient
between dayside and nightside or momentum transfer from the solar wind via the induced
magnetic field since the flow velocity is in the Alfvénic regime. |
|
|
|
|
|
|