Type 5 echoes observed by VHF Doppler radar at the auroral ionosphere

摘要

A new type of coherent radar echoes from the auroral E region, which shows a narrow spectrum peak around 12Hz, has been observed by 50 MHz VHF Doppler radar at Syowa Station during severe magnetic disturbances. The appearance of new type echoes are restricted to post-midnight hours. Plasma waves responsible for these echoes seem to propagate obliquely to the magnetic field.