Ionospheric Joule dissipation as a damping mechanism for high latitude ULF pulsations: Observational evidence |
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| Authors: | KH Glaßmeier H Volpers W Baumjohann |
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| Institution: | Institut für Geophysik, Universität Münster, Corrensstr. 24, D-4400 Münster, Federal Republic of Germany;Max-Planck-Institut für Physik und Astrophysik, Institut für extraterrestrische Physik, D-8046 Garching, Federal Republic of Germany |
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| Abstract: | On 9 January 1979 an SI-excited pulsation event was observed by the Scandinavian Magnetometer Array. The pulsation period shows a clear variation with latitude which suggests decoupled oscillations of individual magnetic field shells. The pulsation amplitudes exhibit an e-fold decay with the damping rate γ varying both in longitudinal and latitudinal directions. Assuming Joule heating in the ionosphere as the dominant damping mechanism (and thus γ ～ Σ?1p) approximate height-integrated Pedersen conductivity profiles were calculated which fit well with previously observed Σp distributions. This is interpreted as observational evidence for ionosopheric Joule dissipation as the major damping mechanism for high-latitude ULF-pulsations. |
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