Studies on generation mechanism of the electron density irregularity in the ionospheric cusp region

强相干HF后向散射回波是极尖的一个众所周知的特征，并且被认为是由具有decliter尺度长度的场对准等离子体不规则性引起的。2008年12月，我们发射了探测火箭，对电子密度不均匀性进行了直接测量，成功地解释了电子密度不均匀性的产生机理。目前的研究带来了新的见解，这一事件; 1）密度不规则性的空间分布和功率谱，2）与630 nm极光发射的空间关系，和3）相关的100 eV沉淀电子作为一种可能的能源。

Strong coherent HF backscatter echoes are a well-known characteristic of the polar cusp, and are believed to result from field-aligned plasma irregularities with decameter scale length. However, the generation mechanism has not been understood.In December 2008, we launched the sounding rocket to elucidate its generation mechanism, and succeeded the direct measurement of the electron density irregularity. The present study brought new insights of this event ; 1) spatial distribution and power spectrum of the density irregularity, 2) spatial relationship with 630 nm auroral emission, and 3) relevance to 100 eV precipitating electrons as a possible energy source.