Optical signatures of auroral arcs produced by field line resonances: comparison with satellite observations and modeling
Optical signatures of auroral arcs produced by field line resonances: comparison with satellite observations and modeling
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DOI：
10.5194/angeo-21-933-2003
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发表时间：
2003-04
影响因子：
1.9
通讯作者：
J. Samson;R. Rankin;V. Tikhonchuk
中科院分区：
文献类型：
--
作者：
J. Samson;R. Rankin;V. Tikhonchuk
摘要。我们展示了1997年1月31日晚上由场线共振产生的极光弧光学特征的CANOPUS阵列的两个例子。第一个例子发生在当地晚上18:00左右（磁地方时），CANOPUS子午线扫描光度计数据显示了场线共振的所有经典特征。有两个，近单色共振（在大约2.0和2.5 mHz），并且都显示在振幅上的纬度峰值，在最大值上有大约180度的纬度相移。第二次场线共振事件发生在当地午夜附近，大约在22:00和22:40 MLT之间。磁强计和光学数据表明，场线共振频率很低，接近1.3 mHz。来自CANOPUS的全天成像仪数据显示，在这次事件中，场线共振产生了向西传播的极光弧，弧宽约为10公里。电子能量约为1kev。FAST卫星的数据也显示了这一事件（Lotko et al., 1998），我们将我们的观测结果与Lotko et al.（1998）的观测结果进行了比较。该场线共振的一个显著特征是其纬向相移明显大于180度。在我们的讨论中，我们提出了一个场线共振模型，它解释了主要的物理效应，并与观测结果很好地吻合。我们强调三点。首先，第二个事件中磁场线共振的低频可能是由于磁尾磁场线的拓扑结构被拉伸，磁场线上的磁场线共振穿过等离子体片的地球边缘。其次，纬度相结构可能表明由于电子捕获或有限的离子陀螺半径而产生的色散效应。第三，我们证明了非局域电导率模型可以很容易地解释在场线共振中看到的平行电场和沉淀电子能。关键字。磁层物理学（电场；高能粒子沉淀；电流系统）
Abstract. We show two examples from the CANOPUS array of the optical signatures of auroral arcs produced by field line resonances on the night of 31 January 1997. The first example occurs during local evening at about 18:00 MLT (Magnetic Local Time), where CANOPUS meridian scanning photometer data show all the classic features of field line resonances. There are two, near-monochromatic resonances (at approximately 2.0 and 2.5 mHz) and both show latitudinal peaks in amplitude with an approximately 180 degree latitudinal phase shift across the maximum. The second field line resonance event occurs closer to local midnight, between approximately 22:00 and 22:40 MLT. Magnetometer and optical data show that the field line resonance has a very low frequency, near 1.3 mHz. All-sky imager data from CANOPUS show that in this event the field line resonances produce auroral arcs with westward propagation, with arc widths of about 10 km. Electron energies are on the order of 1 keV. This event was also seen in data from the FAST satellite (Lotko et al., 1998), and we compare our observations with those of Lotko et al. (1998). A remarkable feature of this field line resonance is that the latitudinal phase shift was substantially greater than 180 degrees. In our discussion, we present a model of field line resonances which accounts for the dominant physical effects and which is in good agreement with the observations. We emphasize three points. First, the low frequency of the field line resonance in the second event is likely due to the stretched topology of the magnetotail field lines, with the field line resonance on field lines threading the earthward edge of the plasma sheet. Second, the latitudinal phase structure may indicate dispersive effects due to electron trapping or finite ion gyroradius. Third, we show that a nonlocal conductivity model can easily explain the parallel electric fields and the precipitating electron energies seen in the field line resonance. Key words. Magnetospheric physics (electric fields; energetic particles precipitating; current systems)