Dynamic models for magnetospheric oscillations on the minute scale
Abstract
Sudden pulses in the model solar wind sets the Earth's magnetosphere into damped oscillatory motions. Oscillation periods on the order of 5-10 min have been observed by instrumented spacecrafts. A simple model is capable of explaining the basic properties of these oscillations and give scaling laws for their characteristics in terms of the parameters of the problem, such as the Solar wind momentum density. The period of the oscillations, their damping and anharmonic nature are accounted for.The model has no free adjustable numerical parameters and can be seen as an effort to predict some dynamic properties of the magnetosphere on the basis of measurable steady state characteristics. A simple test of the model is found by comparing its prediction of the Earth-Magnetopause distance with observed values. The results agree well with observations. The analysis is supported by numerical simulations solving the Magneto-Hydro-Dynamic (MHD) equations in two spatial dimensions, where we let a solar wind interact with a magnetic dipole representing a magnetized Earth. Two tilt-angles of the magnetic dipole axis were considered. We observe the formation of a magnetosheath, with the magnetopause at a distance corresponding well to the analytical results. The analytical model seem to be robust, and gives good qualitative agreement with the numerical simulations for a range of parameters, also concerning oscillation periods and damping times for cases where the dynamic response to perturbations are considered. The analysis allows also for predicting the magnetic field perturbations detected on Earth due to changes in the magnetosheath current. In order to improve the model we study a conformal mapping that brings the shape of the magnetosheath model closer to observations.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMSM11C2315S
- Keywords:
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- 2740 MAGNETOSPHERIC PHYSICS / Magnetospheric configuration and dynamics;
- 2784 MAGNETOSPHERIC PHYSICS / Solar wind/magnetosphere interactions;
- 7899 SPACE PLASMA PHYSICS / General or miscellaneous