Browsing by Author "Kagan, L. M."
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Item Restricted Energy exchange rate for the equatorial electrojet: Test of the model of two‐stream processes that includes thermal corrections(American Geophysical Union, 2007-10-25) Kagan, L. M.; Kissack, R. S.The experiment of Balsley and Farley (1971) in Jicamarca, Peru has been the only multi(3)‐frequency investigation of the equatorial electrojet. The radar was operated sequentially at frequencies of 16.25, 49.92 and 146.25 MHz and probed the same ionospheric volume. The most prominent feature of these observations was the increase in the phase velocity Vph of Farley‐Buneman (FB) waves with increasing radar frequency while the classical fluid theory gives Vph independent on their wavelength and the simple kinetic theory accounts for only a small increase in Vph. Our recent theory predicts a wavenumber dependence of the FB wave phase velocity. The rate of increase depends on the altitude of the electrojet and seems to match the observed wave behavior. The most important byproduct of this case study is our conclusion that the energy exchange rate in inelastic electron‐neutral interactions is about two‐to‐three times higher that it has been assumed in estimates.Item Restricted Unexpected rapid decrease in phase velocity of submeter Farley-Buneman waves with altitude(American Geophysical Union, 2008-02-09) Kagan, L. M.; Kissack, R. S.; Kelley, M. C.; Cuevas, R.An unexpected and drastic drop in the phase velocity Vph 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 Vph 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 Vph 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.