TERRAPUB Earth, Planets and Space

Earth Planets Space, Vol. 64 (No. 7), pp. 605-611, 2012

Soliton-induced spectrally uniform ion line power enhancements at the ionospheric F region peak

Jonas Ekeberg1, Gudmund Wannberg1, Lars Eliasson1, and Ingemar Häggström2

1Swedish Institute of Space Physics, P.O. Box 812, SE-981 28 Kiruna, Sweden
2EISCAT Scientific Association, P.O. Box 812, SE-981 28 Kiruna, Sweden

(Received April 18, 2011; Revised February 24, 2012; Accepted February 28, 2012; Online published August 16, 2012)

Abstract: We present European Incoherent Scatter (EISCAT) observations of spectrally uniform ion line power enhancements (SUIPE), where the up- and downshifted shoulder and the spectral valley between them are enhanced simultaneously and equally. We have identified 48 cases of this type of ion line enhancement in data from the EISCAT Svalbard radar taken during the International Polar Year (extending from March 2007 to the end of February 2008). The SUIPEs are observed at altitudes between 210 km and 280 km with a standard deviation of 9% of the average occurrence height 230 km. The power enhancements are one order of magnitude above the thermal level. The SUIPEs occur at the ionospheric F region density peak with 85% of the cases located within 10 km of the peak. These characteristics are in good agreement with the predictions of a recently published model for soliton-induced ion-line enhancements at the F region peak. The SUIPE occurrence shows a clear preference for magnetically disturbed conditions, with the likelihood of occurrence increasing with increasing K index. A majority of the events occur in the magnetic evening to pre-midnight sector.
Key words: Auroral ionosphere, radar observations, plasma waves and instabilities, solitons and solitary waves.

Corresponding author E-mail: jonas.ekeberg@irf.se

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