Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 35, 1143-1149, 2017
https://doi.org/10.5194/angeo-35-1143-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Regular paper
24 Oct 2017
Plasma line observations from the EISCAT Svalbard Radar during the International Polar Year
Nickolay Ivchenko1, Nicola M. Schlatter1, Hanna Dahlgren1,2, Yasunobu Ogawa3, Yuka Sato3, and Ingemar Häggström4 1School of Electrical Engineering, Royal Institute of Technology KTH, Stockholm, Sweden
2School of Physics and Astronomy, University of Southampton, Southampton, UK
3National Institute of Polar Research, Tokyo, Japan
4EISCAT Scientific Association, Kiruna, Sweden
Abstract. Photo-electrons and secondary electrons from particle precipitation enhance the incoherent scatter plasma line to levels sufficient for detection. When detectable the plasma line gives accurate measure of the electron density and can potentially be used to constrain incoherent scatter estimates of electron temperature. We investigate the statistical occurrence of plasma line enhancements with data from the high-latitude EISCAT Svalbard Radar obtained during the International Polar Year (IPY, 2007–2008). A computationally fast method was implemented to recover the range-frequency dependence of the plasma line. Plasma line backscatter strength strongly depends on time of day, season, altitude, and geomagnetic activity, and the backscatter is detectable in 22.6 % of the total measurements during the IPY. As expected, maximum detection is achieved when photo-electrons due to the Sun's EUV radiation are present. During summer daytime hours the occurrence of detectable plasma lines at altitudes below the F-region peak is up to 90 %. During wintertime the occurrence is a few percent. Electron density profiles recovered from the plasma line show great detail of density variations in height and time. For example, effects of inertial gravity waves on the electron density are observed.

Citation: Ivchenko, N., Schlatter, N. M., Dahlgren, H., Ogawa, Y., Sato, Y., and Häggström, I.: Plasma line observations from the EISCAT Svalbard Radar during the International Polar Year, Ann. Geophys., 35, 1143-1149, https://doi.org/10.5194/angeo-35-1143-2017, 2017.
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Short summary
Photo-electrons and secondary electrons from particle precipitation enhance the incoherent scatter plasma line to levels sufficient for detection. A plasma line gives an accurate measure of the electron density and can be used to estimate electron temperature. The occurrence of plasma line enhancements in the EISCAT Svalbard Radar data was investigated. During summer daytime hours the plasma line is detectable in up to 90 % of the data. In winter time the occurrence is a few percent.
Photo-electrons and secondary electrons from particle precipitation enhance the incoherent...
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