Premium
Enhanced ELF wave generation efficiency using ‘O’ Mode HF heating of the ionosphere: An instrumental explanation
Author(s) -
Barr Richard,
Stubbe P.,
Rietveld M. T.,
Nielsen E.
Publication year - 1998
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 - 10.1029/98gl02665
Subject(s) - ionosphere , physics , amplitude , harmonics , modulation (music) , mode (computer interface) , excitation , computational physics , radio wave , high frequency , square wave , amplitude modulation , frequency modulation , acoustics , optics , geophysics , radio frequency , telecommunications , quantum mechanics , voltage , computer science , operating system
In [ Barr et al. 1997 ] we presented ELF signals received near the Tromsø ionospheric heater facility when the heater radiated HF signals amplitude modulated by a 505Hz square wave. Square wave modulation enabled simultaneous multiple frequency measurements to be made of the signals radiated from the ionosphere as the heater was switched to radiate both ‘X’ and ‘O’ mode HF waves. We found that whereas the first 3 odd harmonics of the square wave (≥ 1515 Hz) all showed the accepted behaviour of reduced wave excitation on switching from ‘X’ to ‘O’ mode HF heating, the fundamental frequency showed enhanced excitation of more than 10dB with ‘O’ mode heating. These observations were given an ionospheric explanation in terms of a change from Hall to Pedersen current modulation with the change from ‘X’ to ‘O’ mode HF heating. We present here an alternative analysis, which has both instrumental and ionospheric components and is also able to explain the observations.