朱诺号对木星夜侧磁层大规模方位场及相关径向流的观测

IF 2.6 2区 地球科学 Q2 ASTRONOMY & ASTROPHYSICS
G. Provan, S. W. H. Cowley, J. D. Nichols
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引用次数: 0

摘要

我们结合极轨运行的朱诺号宇宙飞船从黎明到黄昏再到午夜的前 46 个数据采集周期的磁数据,研究木星夜间磁层的方位场和相关电流。数据按距磁轴 4-32 RJ 的垂直径向距离 ρ 和当地时间(LT)分类,沿经验极性模型场线从磁层尾部跨至磁层中部(电离层极坐标 θi ∼ 5°-17°)。这些参数对数据进行了很好的组织。在南部尾场线(∼ 5 ° < θ i ≤ 11 ° ${\sim 5{}^{\circ}< \theta }_{i}\le 11{}^{\circ}$ )上,方位场被很好地表示为回扫场的总和,回扫场以 1/ρ 的形式下降,几乎与 θi 和 LT 无关,还有一个与指向太阳的 ∼3.5 nT 一致的近恒定场。该组合在黎明/午夜时后退,但在黄昏时前倾至 ∼5 RJ 以外。外磁层(θi ∼ 12°-15.5°)方位场则几乎与 LT 无关,在黎明扇区与尾场近乎连续,但在黄昏-午夜扇区,尾场界面和外磁层场线上有很大的剪切。尾区 1/ρ 场与位于磁轴 θi ∼ 5° 范围内的夜间向内极轴电流 ∼5.8 MA 有关,而在∼30 RJ 研究边界附近测量到的黄昏-午夜场剪切提供了与近恒定场有关的向内电流 ∼15.4 MA。方位磁场在中磁层磁场线之间(θi ∼ 15.5°-17°)下降到很小的数值,与每个半球 21.2 MA 的外向磁流有关,几乎与形成夜侧赤道磁流层的 LT 无关,从而平衡了这些内向磁流。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Juno Observations of Large-Scale Azimuthal Fields in Jupiter's Nightside Magnetosphere and Related Radial Currents

Juno Observations of Large-Scale Azimuthal Fields in Jupiter's Nightside Magnetosphere and Related Radial Currents

We combine magnetic data from the first 46 data-taking periapsides of the polar orbiting Juno spacecraft spanning dawn to dusk via midnight to investigate azimuthal fields and related currents in Jupiter's nightside magnetosphere. Data are binned by perpendicular radial distance ρ from the magnetic axis over 4–32 RJ along empirical poloidal model field lines spanning from tail to middle magnetosphere regions (ionospheric colatitudes θi ∼ 5°–17°), and by local time (LT). The data are well organized by these parameters. On southern tail field lines ( 5 ° < θ i 11 ° ${\sim 5{}^{\circ}< \theta }_{i}\le 11{}^{\circ}$ ) the azimuthal field is well represented as the sum of sweepback fields falling as 1/ρ that are near-independent of θi and LT, and a near-constant field consistent with ∼3.5 nT pointing sunward. The combination is swept back at dawn/midnight but swept forward at dusk outside ∼5 RJ. Outer magnetosphere (θi ∼ 12°–15.5°) azimuthal fields are instead swept back near-independent of LT, near-continuous with the tail field in the dawn sector, but with large shear at the tail interface and across outer magnetosphere field lines in the dusk-midnight sector. The tail region 1/ρ field is associated with a nightside inward polar axial current ∼5.8 MA located within θi ∼ 5° of the magnetic axis, while the dusk-midnight field shear measured near the ∼30 RJ study boundary provides an inward current ∼15.4 MA, related to the near-constant field. Azimuthal fields fall to small values across middle magnetosphere field lines (θi ∼ 15.5°–17°), associated with outward currents ∼21.2 MA per hemisphere near-independent of LT forming the nightside equatorial current sheet, balancing these inward currents.

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来源期刊
Journal of Geophysical Research: Space Physics
Journal of Geophysical Research: Space Physics Earth and Planetary Sciences-Geophysics
CiteScore
5.30
自引率
35.70%
发文量
570
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