Open AccessStimulated electromagnetic emissions during pump frequency sweep through fourth electron cyclotron harmonic
Author(s) -
Carozzi T. D.,
Thidé B.,
Grach S. M.,
Leyser T. B.,
Holz M.,
Komrakov G. P.,
Frolov V. L.,
Sergeev E. N.
Publication year - 2002
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2001ja005082
Subject(s) - cyclotron , harmonic , physics , ionosphere , electron , sweep frequency response analysis , cutoff frequency , computational physics , electromagnetic radiation , atomic physics , optics , acoustics , geophysics , nuclear physics
The frequency of a high‐power HF radio wave incident on the ionosphere was swept, using a computer‐controlled transmitter signal, in <10 s within a 60‐kHz‐wide frequency band approximately centered on the fourth harmonic of the electron cyclotron frequency. Measurements of the spectral behavior of stimulated electromagnetic emissions (SEE) across this harmonic after preconditioning could thereby be made with unprecedented resolution, speed, and ionospheric stability. Comparison of local electron cyclotron frequency estimations based on the experimental data reveals discrepancies between certain downshifted maximum models and the empirical broad upshifted maximum (BUM) feature formula Δ f BUM = f 0 − nf ce . Weak emissions related to the BUM were discovered below the nominal BUM cutoff frequency. Finally, we observed that the intensity of certain SEE components differed depending on the whether the pump frequency sweep was ascending or descending.