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Unexpected rapid decrease in phase velocity of submeter Farley‐Buneman waves with altitude
Author(s) -
Kagan L. M.,
Kissack R. S.,
Kelley M. C.,
Cuevas R.
Publication year - 2008
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 - 10.1029/2007gl032459
Subject(s) - altitude (triangle) , radar , physics , electrojet , atmospheric sciences , meteorology , geodesy , geology , geophysics , magnetic field , earth's magnetic field , telecommunications , geometry , mathematics , quantum mechanics , computer science
An unexpected and drastic drop in the phase velocity V ph of Farley‐Buneman (FB) waves with increasing altitude was observed in the equatorial electrojet over Jicamarca. The effect was detected with the newly employed 430‐MHz radar looking vertically. The decrease in V ph was 67 m/s and 36 m/s over 2.4 km for the FB waves moving towards and away from the radar, respectively. By contrast, the 430‐MHz data from 20° west displayed little dependence on altitude. Simultaneous observations with a 50‐MHz radar at 23° and 51° west also displayed little change of V ph with altitude. We show that electron inelastic cooling which defines gradual transition from super‐adiabatic to isothermal processes at 50 MHz (used in majority of observations), becomes unimportant at higher frequencies. The effect is evinced at radar frequencies ≥150 MHz and requires altitude resolution <2 km to be observed. Averaging over >7 km at oblique incidence masks the effect.