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

强相干高频后向散射回波是极尖的一个众所周知的特征，并且被认为是由场向等离子体不规则的十米尺度长度引起的。然而，其产生机制尚不清楚。2008年12月，我们发射了探空火箭，阐明了其产生机理，并成功地直接测量了电子密度的不规则性。本研究对这一事件有了新的认识；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；3)与100 eV沉淀电子作为可能的能量源的相关性。

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.