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Triggering of whistler mode emissions by the band‐limited impulse (BLI) Associated with amplified Vlf signals from Siple Station, Antarctica
Author(s) -
Helliwell Robert A.
Publication year - 2000
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl003676
Subject(s) - whistler , physics , amplitude , impulse (physics) , cyclotron , narrowband , magnetic field , electron , computational physics , geophysics , optics , nuclear physics , quantum mechanics
At termination of an amplified and saturated ( B sat ) Vlf pulse from Siple Station, Antarctica, a band‐limited (50–500 Hz range) impulse (BLI) is generated which in turn triggers a narrowband emission, of about the same amplitude, that starts at about 50–150 Hz above the frequency of B sat , called the positive frequency offset (PFO). The BLI creates the PFO by reducing the parallel velocities of existing phase‐bunched cyclotron resonant electrons that form the source currents ( J ⟂ ) of the stimulated radiation. The PFO is proportional to the magnetic field intensity B BLI of the BLI. Since B BLI ≈ B sat the PFO then becomes a measure of the saturated field B sat . An example for L = 4 and a pitch angle of 60°, gives B sat ≅ 5pT, in good agreement with previous estimates of B sat .