Optical emissions enhanced by X mode ionosphere HF pumping
Swedish Institute of Space Physics
Strong enhancement of the optical emissions with excitation thresholds from 1.96 eV up to 18.75 eV have been observed during experiments of ionosphere modiﬁcation by high power HF radio waves since the early 1970s. Up to now all these emissions were observed only during the interaction of the O-mode HF radio wave with the ionospheric plasma. On 19 October 2012, during an EISCAT heating experiment, strong optical emissions were observed by ALIS, in first time, for X-mode ionosphere pumping. While for O-mode heating the optical emission enhancements can be explained by the ionospheric electron heating and acceleration due to the nonlinear interaction of the powerful radio wave with ionosphere, the mechanism responsible for the emission enhancements during the X-mode heating is not known.
In the experiment optical emissions have been measured in three different wave-lengths simultaneously from four ALIS stations. The emission intensity ratios as well as the characteristics of the spatial distribution of the enhanced optical emissions provide important information on the possible mechanisms of the radio wave â€“ ionosphere interaction. In this report we present the results of comparison of the characteristics of the optical emissions caused by X-mode heating with the characteristics of the emissions enhanced by O-mode measured during same experiment.
Created 2013-10-03 10:38:46 by Uwe Raffalski Last changed 2014-02-05 12:14:41 by Mats HolmstrÃ¶m