Geoscience Reference
In-Depth Information
THE DAYSIDE MAGNETOSPHERE OF MERCURY
S. MASSETTI, S. ORSINI, E. DE ANGELIS, V. MANGANO,
A. MILILLO and A. MURA
Istituto di Fisica dello Spazio Interplanetario, IFSI-INAF, Roma, Italy
stefano.massetti@ifsi-roma.inaf.it
Many efforts are currently in progress to depict a realistic model of the Hermean
magnetosphere, also in the frame of the researches that will be performed by the
next space missions
Messenger
and
BepiColomb
o. Although the magnetosphere
of this planet can be roughly approximated by scaling the Earth's one (about
1:6.9), several differences are expected due to both the lack of an ionosphere,
which rise questions concerning the closure of the magnetospheric currents, and
the likely absence of a stable ring current. A remarkable feature, outlined by
the models, is represented by the wide area accessible by the solar wind plasma
on the Mercury's dayside, due to the broad footprint of the magnetospheric
cusp regions. Moreover, the absence of a dense atmosphere/ionosphere implies
that a large faction of the impinging plasma can reach the planet's surface. We
present the results obtained by comparing two modelization of the Mercury's
magnetosphere by means of
ad hoc
modified
Tsyganenko
and
Toffoletto-Hill
models. The analysis is focused on the dayside magnetospheric configurations
and plasma entry patterns, derived by taking into account the effect of the
magnetic reconnection with the interplanetary magnetic field. The role played
by the radial IMF component (
B
x
) is also discussed.
1. Introduction
We present preliminary results obtained by comparing two modelization
of the Mercury's magnetosphere by means of
ad hoc
modified
Tsyganenko
(T96) and
Toffoletto-Hill
(TH93) models, hereafter referred as T96* and
TH93*, respectively. The analysis is focused on the dayside magnetospheric
configurations and plasma entry patterns, derived by taking into account
the effect of the magnetic reconnection with the interplanetary magnetic
field (IMF). Figure 1 sketches the reconnection geometry on the dayside
magnetopause, and the related key parameters. We applied the stress bal-
ance condition to the
de Hoffmann-Teller
(HT) reference frame, moving
along the magnetopause at the rotational discontinuity produced by the
magnetic reconnection between the planet's magnetic field and the inter-
planetary magnetic field (e.g., Refs. 1 and 2). Equations (1)-(5) permit us
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