 |
| Titel |
Earth magnetopause motion associated with ULF wave activity in the magnetosphere |
| VerfasserIn |
O. Agapitov, K.-H. Glassmeier, Yu. Yampolsky |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250030571
|
|
|
|
|
|
| Zusammenfassung |
| We focus our study on the properties of the quasi periodic magnetopause motion and magnetosphere waves with the same frequencies (ULF range) registered by the THEMIS spacecraft Fluxgate Magnetometer (FGM) and Electrostatic Analyzer (ESA). Two different types of magnetopause motion associated to magnetosphere wave activity can be distinguished: surface waves generated by growth of the Kelvin - Helmholtz instability and quasi static one dimensional displacement of the magnetopause surface. Surface waves penetrate to the resonance field line and generate toroidal and poloidal alfven modes with typical FLR properties. One dimensional quasi periodic displacements of the dayside magnetopause are probably caused by cavity modes – standing fast MHD wave between the magnetopause and reflection point near the plasmapause. ULF waves observed in the low latitude magnetopause region manifest themselves as fast MHD modes propagated tailward. The estimation of phase velocity based on multispacecraft timing technique gives the value about 0.1 – 0.2 of the local alfven velocity estimation. Observed slowing-down waves can be identified as magnetosphere waveguide modes. Simultaneous measurements of magnetic field and plasma parameters inside the magnetosphere and in the magnetosheath demonstrate high correlation of magnetopause displacements with maxima of magnetic field wave perturbation. We model fast MHD wave propagation and reflection in the magnetosphere (with the source in the subsolar region) by means of ray-tracing technique and obtain good agreement with observed properties of waveguide and cavity modes. Thus magnetopause motion properties can be used as indicator of magnetosphere ULF wave activity type. |
|
|
|
|
|