Statistics – Applications
Scientific paper
May 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agusmsm42a..06s&link_type=abstract
American Geophysical Union, Spring Meeting 2002, abstract #SM42A-06
Statistics
Applications
2736 Magnetosphere/Ionosphere Interactions, 1640 Remote Sensing, 2431 Ionosphere/Magnetosphere Interactions (2736)
Scientific paper
The fast, quasiperiodic variations of the geomagnetic field known as micropulsations are carried through the magnetosphere and ionosphere by hydromagnetic (HM) waves of lower frequencies than the ion gyroresonance. As for ground signatures of the pulsations, they exist in the form of ULF (ultra low frequency) electromagnetic (EM) oscillations owing to the HM-to-EM mode conversion at the lower ionospheric boundary. The angular and polarizational field structure at the observation point apparently bears an imprint of the structural and electric properties of the ionosphere (transverse conductivities of the plasma before all), and hence can be used for diagnosis of the environmental plasma. Discussed in this paper are the results of observation, numerical simulation and diagnostic applications of the Pc3/Pc4 geomagnetic pulsations recorded at the Ukrainian Antarctic Base `Akademik Vernadsky' and in the Boston, MA area, which is close to `Vernadsky's' conjugate point. The initial data from both sites represent 1 Hz-sampled records of the H, D and Z geomagnetic field components that are subjected to statistical and spectral data analysis. The pulsations in the Northern hemisphere often show a 2 to 3 sec time lag compared with the Antarctic site, which reflects the difference in plasma conductivities of the conjugate ionospheres. The time lag demonstrates diurnal variations, increasing near the dawn and dusk and remaining almost zero through midday and midnight hours. These variations, as well as changes in the difference of pulsation amplitudes at the conjugate points are controlled by variations of the ionospheric transverse conductivities. The theoretical model developed, incorporating the upper and the lower ionosphere, the neutral atmosphere gap and the conducting ground has been used to simulate the spatial and polarization structure of the ULF field at the ground level and recover essential parameters of the ionospheric E-region, and modal composition and angular spectrum of the MHD waves that give rise to the ground response observed.
Groves Keith M.
Moldwin Mark B.
Sinitsin V. G.
Yampolski Yu. M.
Zalizovski A. V.
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