Stability within Jupiter’s polar auroral ‘Swirl region’ over moderate timescales
Stability within Jupiter’s polar auroral ‘Swirl region’ over moderate timescales
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木星极光“漩涡区域”在中等时间尺度内的稳定性
DOI：
10.1016/j.icarus.2015.12.044
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发表时间：
2016
期刊：
影响因子：
3.2
通讯作者：
M. Perry
中科院分区：
文献类型：
--
作者：
T. Stallard;J. Clarke;H. Melin;S. Miller;J. Nichols;J. O’Donoghue;Rosie E Johnson;J. Connerney;T. Satoh;M. Perry
木星的漩涡区域，主要极光发射的极向，在以前的观测中被描述为具有高度可变的极光发射，在两分钟的时间尺度上，紫外线图像的典型积分时间，整个区域发生急剧变化。这种可变性使得难以与H3+排放进行比较。在这里，我们表明，在H3+图像的漩涡区域的特点是相对稳定的发射，往往与弧形的漩涡和黑暗区域之间的边界上的发射。在电离层中H3+分子的近似寿命期间拍摄的多个紫外图像的叠加显示出与H3+图像中观察到的结构相似的结构。我们的分析表明，木星的漩涡区域内的紫外极光形态是高度可变的，只有很短的时间尺度上的100秒，粒子沉淀过程的固有属性，但这种可变性下降了5-15分钟的时间尺度。在10到100分钟的中等时间尺度上，漩涡区域是稳定的，通过尚未未知的潜在磁层相互作用而演变。这表明，在5-15分钟的时间尺度上观察紫外极光可以解析清晰的极光结构，这将有助于我们理解这些特征的磁层起源，并且计算不同时间尺度上的变化，特别是>15分钟，为我们理解木星的极地极光提供了一个新的重要的新工具。
Jupiter’s Swirl region, poleward of the main auroral emission, has been characterised in previous observations as having highly variable auroral emission, changing dramatically across the region on a two-minute timescale, the typical integration time for UV images. This variability has made comparisons with H3+emission difficult. Here, we show that the Swirl region in H3+images is characterised by relatively stable emission, often with an arc of emission on the boundary between the Swirl and Dark regions. Coadding multiple UV images taken over the approximate lifetime of the H3+molecule in the ionosphere, show similar structures to those observed in the H3+images. Our analysis shows that UV auroral morphology within Jupiter’s Swirl region is only highly variable on short timescales of ∼100 s, an intrinsic property of the particle precipitation process, but this variability drops away on timescales of 5–15 min. On moderate timescales between 10 and 100 min, the Swirl region is stable, evolving through as yet unknown underlying magnetospheric interactions. This shows that observing the UV aurora over timescales 5–15 min resolves clear auroral structures that will help us understand the magnetospheric origin of these features, and that calculating the variability over different timescales, especially >15 min, provides a new and important new tool in our understanding of Jupiter’s polar aurora.