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arXiv 2404.04030astro-ph.EPphysics.space-ph
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磁层条件对木星紫外主极光发射形态的影响——基于Juno-UVS观测

Effect of magnetospheric conditions on the morphology of Jupiter's UV main auroral emission, as observed by Juno-UVS

L. A. Head, D. Grodent, B. Bonfond, A. Moirano, B. Benmahi, G. Sicorello, J-C Gérard, M. F. Vogt, V. Hue, T. Greathouse, G. R. Gladstone, Z. Yao

AI总结:

本研究利用Juno-UVS观测数据,通过新弧形探测技术分析木星紫外主极光发射(ME)形态随磁层状态的变化,发现ME尺寸变化与电流片磁场和磁层压缩相关,且其亮度分布与场向电流理论预期不符。

摘要:

极光发射是磁层过程的反映,而在木星上,紫外主极光发射(ME)的形态如何随磁层压缩或中心电流片强度变化尚不完全确定。本研究利用Juno-UVS的观测将ME的变率与磁层状态联系起来。采用新颖的弧形探测技术,为南北两个半球从近木点1至54的ME确定了新的参考卵形线,并分析了ME相对于该参考卵形线的尺寸和形状变化。ME的形态和亮度随地方时变化:与参考卵形线相比,晨侧ME通常扩张,昏侧ME通常收缩,且昏侧ME的亮度通常是晨侧ME的两倍。北半球和南半球的ME,以及昼侧和夜侧的ME,均相对于其参考卵形线同步扩张和收缩,这表明ME尺寸的可变性是由贯穿整个木星磁层的过程所引起的。Ganymede极光足点的向极纬度偏移与ME的向极运动相关,而Io的足点则不存在类似关系。此外,ME的扩张与磁层盘电流的增加具有良好的相关性。这两个结果表明,不断变化的电流片磁场是导致ME尺寸可变的部分原因。最后,磁层压缩与全球ME收缩和增亮有关,尽管这种增亮主要发生在昼侧ME。这一观测结果,以及昏侧ME通常比晨侧ME更亮的观测,与场向电流的模拟和观测行为形成对比,从而削弱了场向电流与极光ME产生之间的理论联系。

英文摘要:

Auroral emissions are a reflection of magnetospheric processes, and, at Jupiter, it is not entirely certain how the morphology of the UV main emission (ME) varies with magnetospheric compression or the strength of the central current sheet. This work leverages the observations from Juno-UVS to link ME variability with magnetospheric states. Novel arc-detection techniques are used to determine new reference ovals for the ME from perijoves 1 through 54, in both hemispheres, and analyse how the size and shape of the ME vary compared to this reference oval. The morphology and brightness of the ME vary in local time: the dawn-side ME is typically expanded and the dusk-side ME typically contracted compared to the reference oval, and the dusk-side ME being typically twice as bright as the dawn-side ME. Both the northern and southern ME, and the day-side and night-side ME, expand and contract from their reference ovals synchronously, which indicates that the variable size of the ME is caused by a process occurring throughout the jovian magnetosphere. The poleward latitudinal shift of the auroral footprint of Ganymede correlates with the poleward motion of the ME, whereas a similar relation is not present for the footprint of Io. Additionally, the expansion of the ME correlates well with an increase in magnetodisc current. These two results suggest that a changing current-sheet magnetic field is partially responsible for the variable size of the ME. Finally, magnetospheric compression is linked to a global ME contraction and brightening, though this brightening occurs predominantly in the day-side ME. This observation, and the observation that the dusk-side ME is typically brighter than the dawn-side ME, stands in contrast to the modelled and observed behaviour of field-aligned currents and thus weakens the theoretical link between field-aligned currents and the generation of the auroral ME.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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