SSC-excited pulsations recorded near noon on GEOS 2 and on the ground (CDAW 6)

Autor: H. Voelker, K. Knott, M. Lester, U. Wedeken
Rok vydání: 1986
Předmět:
Zdroj: Journal of Geophysical Research. 91:3089
ISSN: 0148-0227
DOI: 10.1029/ja091ia03p03089
Popis: The SSC occurring on March 22, 1979, at 0826 UT had an unusually sharp onset in Scandinavia, in Middle Europe and in experiments on the geostationary satellite GEOS 2, which was near noon, local magnetic time. The ground magnetometer stations showed a small preimpulse which started ∼5 s before the main impulse. Both impulses needed ∼2 s to “propagate” from ground stations at L = 6.3–4.6. Search coil magnetometers indicate a very small precursor in northern Finland (L ∼ 4.4–6.0) which started ∼15–20 s before the main impulse. This small precursor also occurred close to the time of the SSC onset at GEOS 2. We interpret this precursor as an effect of precipitating electrons changing the ionospheric conductivity in a localized region. The main impulse triggered damped magnetic pulsations (Psc) with periods near 160 s and 50 s visible in northern Scandinavia and the electric field detector on GEOS 2. Furthermore, the magnetic field and the energetic ions at GEOS observed pulsations with periods near 80 s, but these could only be observed at the northernmost ground stations. There are several indications that the first three harmonics of standing hydromagnetic waves are detected. They may correspond to periodic oscillations of the subsolar point or eigenperiods of the SSC-excited fast mode (compressional cavity resonance). The tentatively identified second harmonic wave (period ∼80 s) is indicative of a bounce resonance of ring current protons. Inside the plasmasphere the dominant period of a superimposed Psc 4 event increased with latitude for the H component indicating several toroidal eigenoscillations.
Databáze: OpenAIRE
Externí odkaz: