Dynamical consequences of two modes of centrifugal instability in Jupiter's outer magnetosphere
Dynamical consequences of two modes of centrifugal instability in Jupiter's outer magnetosphere
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DOI：
10.1029/2005ja011176
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发表时间：
2004-12
影响因子：
--
通讯作者：
M. Kivelson;D. Southwood
中科院分区：
文献类型：
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作者：
M. Kivelson;D. Southwood
2005 年 4 月 7 日收到； 2005年8月16日修订； 2005 年 9 月 13 日接受； 2005 年 12 月 13 日发表。 [1] 木星磁层中部和外部的重要全球尺度特性可以用等离子体对旋转应力的响应而经历边缘或爆炸性离心不稳定性来解释。该过程解释了等离子体片的特征，特别是从磁场数据推断出的强烈的黎明-黄昏不对称性。磁层顶外部施加的限制力对于该分析至关重要。由于磁层通量管的长度很大，当通量管旋转穿过本地时间扇区时，大多数等离子体盘离子不会在镜像点之间反弹。旋转应力会导致不可逆加热并增加等离子体各向异性，从而为消防水带不稳定创造条件。等离子体盘的外缘在中午前显得稍微稳定，但其外缘有微弱的等离子体损失。等离子盘在中午后进一步变厚，因为它同化了外磁层的空通量管，其中小的垂直尺度不稳定性使等离子体的玻姆扩散能够重新填充耗尽的通量管。在夜间，等离子体片变得非常不稳定，物质从尾部流出，等离子体盘变薄，其外部部分可能会破裂，留下耗尽的闭合通量管。这种流出必定主导磁尾中太阳风控制的重联。晨侧大径向距离处的耗尽通量管形成了覆盖薄等离子体盘的独特的低密度等离子体/磁区。紫外线极光的黎明-黄昏不对称性可能与下午扇区电离层飞轮的较大敲击有关，以驱动模型提出的加热和不稳定性。
Received 7 April 2005; revised 16 August 2005; accepted 13 September 2005; published 13 December 2005. [1] Important global-scale properties of the middle and outer portions of the Jovian magnetosphere can be interpreted in terms of plasma experiencing either marginal or explosive centrifugal instability as a response to rotational stresses. The process accounts for characteristics of the plasmasheet, particularly a strong dawn-dusk asymmetry, inferred from magnetic field data. Confining forces externally imposed at the magnetopause are critical to this analysis. Because of the vast length of magnetospheric flux tubes, most plasma-disk ions do not bounce between mirror points as a flux tube rotates through local time sectors. Rotational stresses can lead to irreversible heating and increase plasma anisotropy, creating the conditions for firehose instability. The outer edge of the plasma disk appears marginally stable prenoon, but there is weak loss of plasma from its outer edge. The plasma disk thickens further postnoon as it assimilates the empty flux tubes of the outer magnetosphere where small perpendicular scale instability enables Bohm diffusion of plasma to refill depleted flux tubes. On the nightside, the plasmasheet becomes strongly unstable, material flows out down tail, the plasma disk thins, and its outer portions can break off leaving depleted closed flux tubes behind. This outflow must dominate solar wind-controlled reconnection in the magnetotail. The depleted flux tubes at large radial distance on the morningside form a distinct low-density plasma/magnetic regime that overlays a thin plasma disk. The dawn-dusk asymmetry in the UV aurora is likely associated with the larger tapping of the ionospheric flywheel in the afternoon sector to drive the heating and instability that the model proposes.