Periodicities and Colors of Pulsating Auroras: DSLR Camera Observations From the International Space Station
Periodicities and Colors of Pulsating Auroras: DSLR Camera Observations From the International Space Station
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DOI：
10.1029/2021ja029564
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发表时间：
2021-10-01
影响因子：
2.8
通讯作者：
Kurita, Satoshi
中科院分区：
文献类型：
--
作者：
Nanjo, Sota;Hozumi, Yuta;Kurita, Satoshi
我们研究了脉动极光（PsA）的空间特征，使用数码相机测量从国际空间站。这些测量涵盖了在短时间间隔（类似于10分钟）的磁本地时间（MLT）方向上类似于5小时宽的区域的PsAs。两个事件的分析表明，PsA的主脉动的周期性没有表现出任何明显的依赖于磁纬度（63-66度）和MLT（00-05）。这些结果表明，周期不是由捕获的电子的反弹时间，但由当地的条件，如温度梯度和/或磁层源区附近的电子密度控制。我们还分析了PsAs的颜色作为沉淀电子能量的代理。数码相机的蓝色和绿色通道分别对分子氮离子的带发射和氧原子的绿色线敏感。因为产生这两种发射的沉淀电子的能带是不同的，所以蓝色与绿色的比率（B/G比率）可以用作PsA电子的能量的替代。的B/G比往往是在上午部门比在午夜部门，这是与以前的研究表明的MLT依赖的PsA电子的能量的结果相一致。这种从数码相机图像中估计极光电子能量的能力预计将为公民科学家提供更多的机会，为极光科学做出更深入的贡献。
We investigated the spatial characteristics of pulsating auroras (PsA) using digital camera measurements from the International Space Station. These measurements covered PsAs in similar to 5-h wide regions in the magnetic local time (MLT) direction in short time intervals (similar to 10 min). Analyses of two events suggested that the periodicity of the main pulsation of a PsA does not exhibit any clear dependence on the magnetic latitude (63-66 degrees) and MLT (00-05). These results suggest that the periods are not controlled by the bounce time of trapped electrons but by local conditions such as gradients of temperature and/or density of electrons near the magnetospheric source region. We also analyzed the colors of PsAs as proxies for the energies of precipitating electrons. The blue and green channels of the digital camera are sensitive to the band emission of molecular nitrogen ions and the green line of oxygen atoms, respectively. Because the energy bands of precipitating electrons producing those two emissions are different, ratios of blue to green (B/G ratios) can be used as proxies for the energies of PsA electrons. The B/G ratio tends to be higher in the morning sector than in the midnight sector, which is consistent with the results of previous studies showing the MLT dependence of the energies of PsA electrons. This capability of estimating the energies of auroral electrons from digital camera images is expected to provide more opportunities for citizen scientists to contribute more deeply to auroral science.