Ground‐based optical observations of hydrogen emission in the auroral substorm
Ground‐based optical observations of hydrogen emission in the auroral substorm
复制标题
极光亚暴氢排放的地基光学观测
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
D. Lummerzheim
中科院分区：
文献类型：
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作者：
C. Deehr;D. Lummerzheim
全天空成像仪（ASTV）和扫描光度计（MSP）的组合被用来确定在阿拉斯加部门的33个极光亚暴的生长阶段，发病，扩张和恢复的光学特征。离散的极光弧，在极光亚暴发病变亮被认为是极向的弥漫极光，其中包含的H发射的距离在10和300公里之间。平均起始时间为2215磁地方时，起始弧和H弧的平均地理纬度分别为64.6°和63.6°。峰值H排放的极向交叉发生在亚暴开始后不久，亚暴加强后2100 MLT。在2100和0100 MLT之间的亚暴恢复期间，峰值H排放穿越回赤道位置。0100 MLT后的峰值H的排放仍然极的电子捕获边界的其余的夜晚。在生长阶段的峰值H发射更快地向赤道移动比发病弧和单调的两倍，在向赤道运动的总强度，在一种方式无关的发病弧的亮度波动。在开始弧的427.8-nm的N2+和557.7-nm的[O I]排放量的减少之前，发病已被报道较早，并被称为“极光衰落”。我们发现630.0 nm的[O I]辐射相对于其他辐射显著增加，我们得出结论，在开始前几分钟内观察到的“衰落”是能量小于100 eV的> 1010电子cm 2 s-V −1的脉冲的电离层特征。因此，这里报告的观测结果并不支持亚暴开始于质子沉淀内部的论点，但在开始之前的“极光衰落”期间发现的软电子脉冲确实支持了那些亚暴开始理论，需要阿尔文速度电子脉冲电子捕获边界的极向和向上场向电流的区域。
A combination of all-sky imagers (ASTV) and meridian-scanning photometers (MSP) was used to identify the optical signature of the growth phase, onset, expansion, and recovery of 33 auroral substorms in the Alaskan sector. The discrete auroral arc that brightens at auroral substorm onset was found to be poleward of the diffuse aurora that contains the H emission by a distance of between 10 and 300 km. The average onset time was 2215 magnetic local time (MLT) and the average geographic latitude of the onset arc and the H arc was 64.6° and 63.6°, respectively. The poleward crossover of the peak H emission occurs shortly after substorm onset, for substorm intensification after 2100 MLT. The peak H emission crosses back to the equatorward position during substorm recovery between 2100 and 0100 MLT. After 0100 MLT the peak H emission remains poleward of the electron-trapping boundary for the rest of the night. During the growth phase the peak H emission moves equatorward more quickly than does the onset arc and monotonically doubles in total intensity during the equatorward motion, in a manner quite unrelated to the fluctuations in brightness of the onset arc. In the onset arc a reduction of 427.8-nm N2+ and 557.7-nm [O I] emissions just prior to onset has been reported earlier and dubbed “auroral fading”. We find that the 630.0-nm [O I] emission rises considerably relative to the others, and we conclude that the “fading” observed in the few minutes prior to onset is the ionospheric signature of a pulse of > 1010 electrons cm2s-V−1 with energies less than 100 eV. Thus the observations reported here do not support the argument that the substorm onset begins from within the proton precipitation, but the discovery of the soft electron pulse during “auroral fading” just prior to onset does support those substorm onset theories requiring a pulse of Alfven speed electrons poleward of the electron trapping boundary and in the region of upward field-aligned current.