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Titel |
Dependence of the location of the Martian magnetic lobes on the interplanetary magnetic field direction |
VerfasserIn |
Norberto Romanelli, Christian Mazelle, Cesar Bertucci, Daniel Gómez |
Konferenz |
EGU General Assembly 2016
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 18 (2016) |
Datensatznummer |
250125599
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Publikation (Nr.) |
EGU/EGU2016-5192.pdf |
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Zusammenfassung |
The magnetic field topology surrounding the Martian atmosphere is mainly the result of
gradients in the velocity of the solar wind (SW). Such variations in the SW velocity
are in turn the result of a massloading process and forces associated with electric
currents flowing around the ionosphere of Mars [Nagy et al 2004, Mazelle et al
2004, Brain et al 2015]. In particular, in the regions where the collisionless regime
holds, the interplanetary magnetic field (IMF) frozen into the SW piles up in front of
the stagnation region of the flow. At the same time, the magnetic field lines are
stretched in the direction of the unperturbed SW as this stream moves away from Mars,
giving rise to a magnetotail [Alfvén, 1957]. As a result and in contrast with an
obstacle with and intrinsic global magnetic field, the structure and organization of the
magnetic field around Mars depends on the direction of the IMF and its variabilities
[Yeroshenko et al., 1990; Crider et al., 2004; Bertucci et al., 2003; Romanelli et al
2015].
In this study we use magnetometer data from the Mars Global Surveyor (MGS) spacecraft
during portions of the premapping orbits of the mission to study the variability of the
Martian-induced magnetotail as a function of the orientation of the IMF. The time spent by
MGS in the magnetotail lobes during periods with positive solar wind flow-aligned IMF
component B∥IMF suggests that their location as well as the position of the central polarity
reversal layer (PRL) are displaced in the direction antiparallel to the IMF cross-flow
component B⊥IMF . Analogously, in the cases where B∥IMF is negative, the lobes are
displaced in the direction of B⊥IMF. We find this behavior to be compatible with a
previously published B⊥IMF analytical model of the IMF draping, where for the first time,
the displacement of a complementary reversal layer (denoted as IPRL for inverse
polarity reversal layer) is deduced from first principles [Romanelli et al 2014]. We
also analyzed these results in the context of recent observations provided by the
Mars Atmospheric and Volatile Evolution spacecraft [e.g. DiBraccio et al 2015]. |
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