Spatial Evolution of Wave‐Particle Interaction Region Deduced From Flash‐Type Auroras and Chorus‐Ray Tracing
Spatial Evolution of Wave‐Particle Interaction Region Deduced From Flash‐Type Auroras and Chorus‐Ray Tracing
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DOI：
10.1029/2021ja029254
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发表时间：
2021-07
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通讯作者：
M. Ozaki;Tomohiro Inoue;Yoshimasa Tanaka;S. Yagitani;Y. Kasahara;K. Shiokawa;Y. Miyoshi;K. Imamura;K. Hosokawa;S. Oyama;R. Kataoka;Y. Ebihara;Y. Ogawa;A. Kadokura
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作者：
M. Ozaki;Tomohiro Inoue;Yoshimasa Tanaka;S. Yagitani;Y. Kasahara;K. Shiokawa;Y. Miyoshi;K. Imamura;K. Hosokawa;S. Oyama;R. Kataoka;Y. Ebihara;Y. Ogawa;A. Kadokura
现场观测波粒相互作用区域的空间变化需要大量的卫星探测器。作为替代方案，闪光型极光，一种由离散合唱元素驱动的脉动极光，可用于研究具有高空间分辨率的相互作用区域。我们根据阿拉斯加加科纳（62.39 ° N，214.78 ° E）亚极光纬度地区的地面观测资料估计了波粒相互作用区域的空间范围，发现极光扩展主要向低纬度一侧扩展。空间位移被认为是由磁层中合唱波的传播效应引起的。使用射线追踪分析来考虑合唱波传播，我们重建了体积发射率的时空演变，并确认主要的膨胀是朝向电离层的低纬度一侧。这项研究表明，合唱波在磁层中的传播为表征波粒相互作用区域的横向尺寸（穿过地磁场线）提供了新的见解。在磁层赤道面10 °以内的磁纬度上，柱极光发射的空间尺度与共振区的磁纬度相关。我们的研究结果表明，闪光极光的空间尺度与合唱振幅间接相关，因为波粒相互作用的纬度范围对波振幅的增长很重要。
In‐situ observations of spatial variations of the wave‐particle interaction region require a large number of satellite probes. As an alternative, flash‐type auroras, a kind of pulsating aurora, driven by discrete chorus elements, can be used to investigate the interaction region with a high spatial resolution. We estimated the spatial extent of wave‐particle interaction region from ground‐based observations of flash aurora at Gakona (62.39°N, 214.78°E), Alaska at subauroral latitudes, and found that the auroral expansion was predominantly to the low‐latitude side. The spatial displacement is thought to be caused by the propagation effects of chorus waves in the magnetosphere. Using ray tracing analysis to take into account chorus wave propagation, we reconstructed the spatiotemporal evolution of the volume emission rate and confirmed that the predominant expansion is toward the lower‐latitude side in the ionosphere. This study shows that chorus wave propagation in the magnetosphere gives new insight for characterizing the transverse size (across the geomagnetic field line) of wave‐particle interaction regions. The calculated spatial scale of the column auroral emission shows a correlation with the magnetic latitude of the resonance region at magnetic latitudes within 10° of the equatorial plane of the magnetosphere. Our results suggest that the spatial scale of a flash aurora is indirectly related to the chorus amplitude because the latitudinal range of the wave‐particle interaction is important for the growth of wave amplitude.