Simultaneous conjugate ground-satellite ULF pulsation measurements at the middle latitudes
The spectra of three series of simultaneous ground (Budkov Observatory) and satellite (Freja) ULF measurements have been processed. The following features were studied in the FFT spectra, power-spectra and cross-spectra of the six-minute samples, recorded during quasi-conjugate approaches of Fre...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
1997-06-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/15/645/1997/angeo-15-645-1997.pdf |
| Summary: | The spectra of three series of simultaneous
ground (Budkov Observatory) and satellite (Freja) ULF measurements have been
processed. The following features were studied in the FFT spectra, power-spectra
and cross-spectra of the six-minute samples, recorded during quasi-conjugate
approaches of Freja to the local Budkov magnetic field line: (a) the Doppler
frequency shift (about 1mHz and less) in the predominant and some particular
spectral components on Freja; (b) the amplitude relations between the ground and
satellite (ratios 0.3 to 0.8); (c) phase shifts between particular signal
components on the spacecraft above the ionosphere (in the azimuthal <i>y</i>-direction
on Freja) and on the ground (in the meridional <i>x</i>-direction at Budkov)
have been estimated (phase lags on the ground ≤ 0.9rad) and (d) also dynamical
characteristics of the fundamental wave modes in the (<i>x</i>,<i>y</i>)-plane,
perpendicular to the magnetic field line, have been estimated for the
predominant spectral components, considering standing oscillation along the
field line. Azimuthal wave numbers were about 2.0, propagating northwest at
~400km/s. |
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| ISSN: | 0992-7689 1432-0576 |