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首页> 外文期刊>Annales Geophysicae >CHAMP observation of intense kilometer-scale field-aligned currents, evidence for an ionospheric Alfven resonator
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CHAMP observation of intense kilometer-scale field-aligned currents, evidence for an ionospheric Alfven resonator

机译：CHAMP观测到的千米级强场对准电流，是电离层Alfven谐振器的证据

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Bursts of very intense kilometer-scale field-aligned currents (KSFACs) are observed quite frequently by the CHAMP satellite when passing through the auroral region. In extreme cases estimated current densities exceed 3mA/m~2. Typical scale sizes of these KSFACs are 1 km.rnThe low-Earth, polar orbiting satellite CHAMP allows one to assess KSFACs down to scales of a couple of 100 m based on its high-precision magnetic field vector data sampled at 50 Hz. Using data from 5 years (2001-2005) details of these currents can be investigated. In our statistical study we find that most of the KSFAC bursts and the strongest events are encountered in the cusp/cleft region. Significantly fewer events are found on the nightside. The affected region is typically 15°-20° wide in latitude. There seems to be some dependence of the current intensity on the level of magnetic activity, K_p. On the other hand, no dependence has been found on sunspot number, the solar flux level, F10.7 or the solar zenith angle. The latitude, at which KSFAC bursts are encountered, expands equatorward with increasing K_p. This trend follows well the auroral oval expansion during enhanced magnetic activity. These KSFACs are generally accompanying large-scale FAC sheets, and they are predominantly associated with Region 1 currents. We propose an explanation of the KSFACs in terms of Alfven waves trapped in a ionospheric resonator, which is initiated when the convection electric field or current strength surpasses a critical value. Many properties of such a resonator are in agreement with our KSFAC results.
机译：CHAMP卫星在穿过极光区域时，经常会发生非常强烈的千米级场对准电流（KSFAC）爆炸。在极端情况下，估计的电流密度超过3mA / m〜2。这些KSFAC的典型尺度大小为1 km.rn低地球极地轨道卫星CHAMP允许人们根据以50 Hz采样的高精度磁场矢量数据评估低至100 m几对的KSFAC。使用5年（2001年至2005年）的数据，可以对这些电流的细节进行调查。在我们的统计研究中，我们发现大多数KSFAC爆发和最强事件发生在尖/裂区域。在夜晚发现的活动数量明显减少。受影响区域的纬度通常为15°-20°。电流强度似乎与磁活动水平K_p有所相关。另一方面，没有发现对太阳黑子数，太阳通量水平，F10.7或太阳天顶角的依赖性。遇到KSFAC突发的纬度随着K_p的增加而向赤道方向扩展。这种趋势很好地遵循了增强磁性活动期间的极光椭圆形膨胀。这些KSFAC通常伴随着大型FAC表，并且主要与1区电流相关。我们建议用电离层谐振器中捕获的Alfven波来解释KSFAC，这是在对流电场或电流强度超过临界值时启动的。这种谐振器的许多特性与我们的KSFAC结果一致。

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