2011 SuperDARN Workshop
Characteristics of ionospheric responses to solar flares observed by the SuperDARN Hokkaido radar
N. Nishitani (1), T. Ogawa (2), T. Kikuchi (1), and T. Hori (1)
(1) STEL, Nagoya University, Nagoya, Japan
(2) NICT, Tokyo, Japan
abstract. Solar flares emit X-rays onto the earth?s ionosphere and causes a variety of changes such as abnormal ionization, which lead to absorption of HF waves. In this paper characteristics of ionospheric responses to solar flares observed by the SuperDARN Hokkaido radar will be presented. We use mainly ground / sea scatter (GS-scatter) echoes, which are commonly observed by the Hokkaido radar in the daytime region. The change of the echoes are characterized by the disappearance / weakening of GS-scatter echoes, preceded by short (a few minutes) periods of positive Doppler velocities corresponding to downward motion of the ionospheric reflection point, indicating increased ionization rate in the E and F region ionospheres. We also observe horizontal asymmetry of reappearance of echoes in the recovery phase probably due to the horizontal non-uniformity in the chemical reaction rate. Details of ionospheric responses to solar flares and their physical interpretation will be presented.