ULF Doppler oscillation of L = 2.5 flux tubes
Menk, F.W.; Clilverd, M.A.; Yearby, K.H.; Milinevski, G.; Thomson, N.R.; Rose, M.C.. 2006 ULF Doppler oscillation of L = 2.5 flux tubes. Journal of Geophysical Research, 111 (A7), A07205. 12, pp. doi 10.1029/2005JA011192Full text not available from this repository.
Plasmaspheric ducts may execute Doppler oscillations driven by propagating ultra-low frequency (ULF) waves. We examined about 100 such events recorded over 1 year under magnetically quiet conditions at L = 2.5 using artificially generated whistler-mode VLF signals and ground magnetometers. Joint peaks in the VLF Doppler and magnetometer spectra occurred at the frequency expected for ULF waves generated by the ion-cyclotron instability in the upstream solar wind. The VLF Doppler shifts are most likely due to radial motion of flux tubes of a few kilometers, driven by the east-west electric field of propagating ULF waves. When the frequencies match, the incoming wave energy also couples to standing poloidal and azimuthal field line oscillations, producing field line resonance signatures in both the D and H components on ground-based magnetometers. The phases of the VLF and ULF oscillations are consistent with ionospheric rotation of the downgoing ULF wave field. Since the scale size of VLF flux tubes is significantly smaller than for ULF flux tubes, VLF Doppler observations can provide more precise spatial information on ULF wave fields in the plasmasphere. Furthermore, it should be possible to use ULF oscillations to monitor the formation of quarter wavelength mode standing field line oscillations when the conjugate ionospheres have different conductivities.
|Identification Number/DOI:||doi 10.1029/2005JA011192|
|Programmes:||BAS Programmes > Antarctic Funding Initiative Projects|
|Additional Information:||Full text not available from this repository|
|NORA Subject Terms:||Atmospheric Sciences
|Date made live:||22 Aug 2007 14:48|
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