 |
| Titel |
A case for variational geomagnetic data assimilation: insights from a one-dimensional, nonlinear, and sparsely observed MHD system |
| VerfasserIn |
A. Fournier, C. Eymin, T. Alboussière |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1023-5809
|
| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 14, no. 2 ; Nr. 14, no. 2 (2007-04-25), S.163-180 |
| Datensatznummer |
250012161
|
| Publikation (Nr.) |
 copernicus.org/npg-14-163-2007.pdf |
|
|
|
|
|
| Zusammenfassung |
| Secular variations of the geomagnetic field have been measured with a
continuously improving accuracy during the last few hundred years,
culminating nowadays with satellite data. It is however well known that the
dynamics of the magnetic field is linked to that of the velocity field in
the core and any attempt to model secular variations will involve a
coupled dynamical system for magnetic field and core velocity.
Unfortunately, there is no direct observation of the velocity.
Independently of the exact nature of the above-mentioned coupled system –
some version being currently under construction – the question is debated
in this paper whether good knowledge of the magnetic field can be
translated into good knowledge of core dynamics. Furthermore, what
will be the impact of the most recent and precise geomagnetic data on our
knowledge of the geomagnetic field of the past and future? These questions
are cast into the language of variational data assimilation, while the dynamical system
considered in this paper consists in a set of two oversimplified
one-dimensional equations for magnetic and velocity fields. This toy model
retains important features inherited from the induction and Navier-Stokes
equations: non-linear magnetic and momentum terms are present and its
linear response to small disturbances contains Alfvén waves. It is
concluded that variational data assimilation is indeed appropriate in principle, even
though the velocity field remains hidden at all times; it allows us to
recover the entire evolution of both fields from partial and irregularly
distributed information on the magnetic field. This work constitutes a
first step on the way toward the reassimilation of historical geomagnetic
data and geomagnetic forecast. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|