电离层极风的EISCAT-VHF雷达观测

THE IONOSPHERIC POLAR WIND OBSERVATIONS WITH EISCAT VHF RADAR

极风现象从理论上提出已20多年了,实验上一直没有充分地证实这种现象的存在,以及它的形成区域位于高纬顶部电离层中.我们利用欧洲非相干散射协会(EISCAT)的VHF雷达(在挪威Tromsφ),对H^+离子极风进行了首次实验研究,结果表明,实验期间观测到H^+离子在顶部电离层中的运动速度始终向上,且随高度的增加而增大,从而证实在高纬顶部电离层中确实存在着一个永久向上的H^+离子流,即H^+离子极风,其速度在1000km 高度上达到1km/s,其通量在此高度上接近于饱和,达到10^(12)m^s(-1),而温度小于0.26eV.在我们的探测高度上仍未发展成超声速极风.

The polar wind was suggested theoretically more than 20 years before. Sufficient evidence has not been given by observations, especially observations in the high-latitude ionosphere. In this paper, we report the results of the first H+ polar wind observations with EISCAT VHF radar. It is shown during the observations that the H+ ion velocity is always upwards in the topside ionosphere and increases with altitude in the observed range, which implys that there is a pe-rament H+ thermal escape in the topside ionosphere with a temperature less than 0.26 eV, say the polar wind. Its outflow velocity is about 1 km/s at 1000 km altitude, and the flux arrives at about 1012 m-2.s-1 approaching the satured flux. The flow is still in the subsonic regime in the observed altitude range.