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Energetics of long period resonant hydromagnetic waves
Author(s) -
Greenwald R. A.,
Walker A. D. M.
Publication year - 1980
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl007i010p00745
Subject(s) - physics , substorm , geophysics , ionosphere , joule heating , magnetopause , alfvén wave , resonance (particle physics) , dissipation , ring current , magnetosphere , instability , energetics , computational physics , atmospheric sciences , plasma , magnetohydrodynamics , mechanics , atomic physics , quantum mechanics , thermodynamics
Recently, the STARE (Scandinavian Twin Auroral Radar Experiment) radar system has been used to measure oscillatory electric fields and latitudinal resonance widths of Pc5 toroidal mode pulsations. In this letter we use these values to determine heights‐integrated Pedersen conductivities in the resonance regions, the quality factors of the resonances, Joule heating in the ionosphere by the pulsations and magnetospheric energy storage in the resonant waves. We have found that the energy stored in a large pulsation is approximately 1% of the energy stored in the ring current. Moreover, the energy dissipated in the ionosphere by such an event can be an appreciable percentage of the equivalent dissipation by a small substorm. Assuming that the pulsation is produced by the Kelvin‐Helmholtz instability on the magnetopause or by a similar solar‐wind driven mechanism, one has a situation in which energy is transported directly from the solar wind to the ionosphere via the medium of a resonant hydromagnetic wave. Lastly, field‐aligned currents associated with this wave may be sufficient to excite topside current instabilities. Hence, we predict that poleward moving bands of auroral precipitation should be observed in association with strong pulsation events.