Hydromagnetic spectroscopy of the magnetosphere with Pc3 geomagnetic pulsations along the 210° meridian

V. Pilipenko (1) , K. Yumoto (2) , E. Fedorov (1) , N. Yagova (1)

1 IPE - Schmidt United Institute of Physics of the Earth [Moscow]
2 Kyushu University

Analysis of Pc3 observational data along the 210° magnetic meridian showed a complicated frequency-latitude structure at middle latitudes. The observed period-latitude distributions vary between events with a "noisy source": the D component has a colored-noise spectrum, while the spectrum of H component exhibits regular peaks that vary with latitude, and events with a "band-limited source": the spectral power density of the D component is enhanced at certain frequencies throughout the network. For most ULF events a local gap of the H component amplitude has been exhibited at both conjugate stations at L ~ 2.1. A quantitative interpretation has been given assuming that band-limited MHD emission from an extra-magnetospheric source is distorted by local field line resonances. Resonant frequencies had been singled out with the use of the asymmetry between spectra of H and D components. Additionally, a local resonant frequency at L ~ 1.6 was determined by the quasi-gradient method using the data from nearly conjugate stations. The experimentally determined local resonance frequencies agree satisfactorily with those obtained from a numerical model of the Alfven resonator with the equatorial plasma density taken by extrapolation of Carpenter-Anderson model. We demonstrate how simple methods of hydromagnetic spectroscopy enable us to monitor simultaneously both the magnitude of the IMF and the magnetospheric plasma density from ULF data.

Domaines: Océan, Atmosphère; Sciences de la Terre

V. Pilipenko, K. Yumoto, E. Fedorov, N. Yagova. Hydromagnetic spectroscopy of the magnetosphere with Pc3 geomagnetic pulsations along the 210° meridian. Annales Geophysicae, 1999, 17 (1), pp.53-65. ⟨hal-00316492⟩