 |
| Titel |
A model of the magnetosheath magnetic field during magnetic clouds |
| VerfasserIn |
L. Turc, D. Fontaine, P. Savoini, E. K. J. Kilpua |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
0992-7689
|
| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 32, no. 2 ; Nr. 32, no. 2 (2014-02-21), S.157-173 |
| Datensatznummer |
250121029
|
| Publikation (Nr.) |
 copernicus.org/angeo-32-157-2014.pdf |
|
|
|
|
|
| Zusammenfassung |
| Magnetic clouds (MCs) are huge interplanetary structures which originate from
the Sun and have a paramount importance in driving magnetospheric storms.
Before reaching the magnetosphere, MCs interact with the Earth's bow shock.
This may alter their structure and therefore modify their expected
geoeffectivity. We develop a simple 3-D model of the magnetosheath adapted to
MCs conditions. This model is the first to describe the interaction of MCs
with the bow shock and their propagation inside the magnetosheath. We find
that when the MC encounters the Earth centrally and with its axis
perpendicular to the Sun–Earth line, the MC's magnetic structure remains
mostly unchanged from the solar wind to the magnetosheath. In this case, the
entire dayside magnetosheath is located downstream of a quasi-perpendicular
bow shock. When the MC is encountered far from its centre, or when its axis
has a large tilt towards the ecliptic plane, the MC's structure downstream of
the bow shock differs significantly from that upstream. Moreover, the MC's
structure also differs from one region of the magnetosheath to another and
these differences vary with time and space as the MC passes by. In these
cases, the bow shock configuration is mainly quasi-parallel. Strong magnetic
field asymmetries arise in the magnetosheath; the sign of the magnetic field
north–south component may change from the solar wind to some parts of the
magnetosheath. We stress the importance of the Bx component. We estimate
the regions where the magnetosheath and magnetospheric magnetic fields are
anti-parallel at the magnetopause (i.e. favourable to reconnection). We find
that the location of anti-parallel fields varies with time as the MCs move
past Earth's environment, and that they may be situated near the subsolar
region even for an initially northward magnetic field upstream of the bow
shock. Our results point out the major role played by the bow shock
configuration in modifying or keeping the structure of the MCs unchanged.
Note that this model is not restricted to MCs, it can be used to describe the
magnetosheath magnetic field under an arbitrary slowly varying interplanetary
magnetic field. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|