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Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 35, 475-479, 2017
https://doi.org/10.5194/angeo-35-475-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
ANGEO Communicates
22 Mar 2017
Relation of anomalous F region radar echoes in the high-latitude ionosphere to auroral precipitation
Hanna Dahlgren1,2, Nicola M. Schlatter1, Nickolay Ivchenko1, Lorenz Roth1, and Alexander Karlsson1 1School of Electrical Engineering, Royal Institute of Technology KTH, Stockholm, Sweden
2School of Physics and Astronomy, University of Southampton, Southampton, UK
Abstract. Non-thermal echoes in incoherent scatter radar observations are occasionally seen in the high-latitude ionosphere. Such anomalous echoes are a manifestation of plasma instabilities on spatial scales matching the radar wavelength. Here we investigate the occurrence of a class of spatially localized anomalous echoes with an enhanced zero Doppler frequency feature and their relation to auroral particle precipitation. The ionization profile of the E region is used to parametrize the precipitation, with nmE and hmE being the E region peak electron density and the altitude of the peak, respectively. We find the occurrence rate of the echoes to generally increase with nmE and decrease with hmE, thereby indicating a correlation between the echoes and high-energy flux precipitation of particles with a high characteristic energy. The highest occurrence rate of > 20 % is found for hmE  =  109 km and nmE  =  1011. 9 m−3, averaged over the radar observation volume.

Citation: Dahlgren, H., Schlatter, N. M., Ivchenko, N., Roth, L., and Karlsson, A.: Relation of anomalous F region radar echoes in the high-latitude ionosphere to auroral precipitation, Ann. Geophys., 35, 475-479, https://doi.org/10.5194/angeo-35-475-2017, 2017.
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Short summary
Anomalous strong echoes with three frequency peaks are occasionally seen with incoherent scatter radars in the ionosphere near 200 km altitude at high latitudes. We investigate how they relate to electron precipitation, by finding the resulting peak electron density and the height of the peak, respectively. We find that occurrence rate increases with density and decreases with height, indicating a correlation between the echoes and precipitating electrons with high energy and energy flux.
Anomalous strong echoes with three frequency peaks are occasionally seen with incoherent scatter...
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