Coseismic Ionospheric Disturbances at Multiple Altitudes Associated with the Foreshock of Tohoku Earthquake Observed by HF Doppler Sounding

Hiroyuki Nakata1, Kazuto Takaboshi1, Toshiaki Takano1 and Ichiro Tomizawa2, (1)Chiba University, Department of Electrical and Electronics Engineering, Chiba, Japan, (2)University of Electro-Communications, Tokyo, Japan