A new perspective on plasma supply mechanisms to the magnetotail from a statistical comparison of dayside mirroring O+ at low altitudes with lobe/mantle beams
A new perspective on plasma supply mechanisms to the magnetotail from a statistical comparison of dayside mirroring O+ at low altitudes with lobe/mantle beams
复制标题
从低空日侧镜像 O 与波瓣/地幔束的统计比较对磁尾等离子体供应机制的新视角
DOI：
10.1029/2001ja900122
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发表时间：
2002
影响因子：
--
通讯作者：
T. Mukai
中科院分区：
文献类型：
--
作者：
K. Seki;K. Seki;R. Elphic;M. Thomsen;J. Bonnell;J. Mcfadden;E. Lund;M. Hirahara;T. Terasawa;T. Mukai
[1]在遥远的叶/地幔中观测到的尾部冷O+束(COB)揭示了向磁尾提供等离子体的机制，因为它们的位置直到尾部距离210RE用传统的磁层动力学观点是无法解释的。这些磁核主要存在于与日侧磁层顶重新连接的磁通量管的输运路线相对应的地幔区域，因此认为这些位于远端叶/地幔的高能磁核来自于日侧磁层中捕获的O+离子。为了检验这一假设的有效性，利用经验磁层模型中的粒子轨迹，对GeoTail观测到的磁核的相空间密度(PSD)和FAST观测到的低空(400-4200公里)尖点附近镜像O+离子的相空间密度(PSD)进行了统计比较。在低于和高于∼keV的能量范围内，COBS的平均峰值功率谱密度的能量分布是不同的，这表明对COBS有贡献的源不止一个。镜像O+的数量随着太阳活动的增加而增加，表明日侧磁层中捕获的O+离子增多。统计比较表明，低空尖点附近的O+功率谱密度与∼1keV以上的COB的功率谱密度相似，而在能量为<；∼1keV的快区，COB的功率谱密度通常高于O+的功率谱密度。这些结果表明，日侧磁层中捕获的O+是能量高于1keV的磁芯的潜在来源，而对于能量低于1keV的磁芯，从尖端/裂隙区域流出的O+是最有可能的来源，正如传统观点所指出的那样。
[1] Observations of tailward cold O + beams (COBs) in the distant lobe/mantle shed new light upon plasma supply mechanisms to the magnetotail since their location up to a tailward distance of 210 R E is not explicable with a conventional view of magnetospheric dynamics. The COBs exist primarily in the mantlelike regions that correspond to the transport route of magnetic flux tubes reconnected at the dayside magnetopause, and thus it has been suggested that these high-energy COBs in the distant lobe/mantle have originated from trapped O + ions in the dayside magnetosphere. In order to examine the validity of this scenario the phase space density (PSD) of the COBs observed by Geotail is compared statistically with that of mirroring O + ions around the cusp observed by FAST at low altitudes (400-4200 km) utilizing particle trajectory tracings in empirical magnetospheric models. The energy distribution of the averaged peak PSD of COBs is different at energies below and above ∼ keV and thus suggests that more than one source contributes to the COBs. The mirroring O + increases in quantity with increasing solar activity and suggest increment of trapped O + ions in the dayside magnetosphere. A statistical comparison shows that the O + PSD around the low-altitude cusp is similar to that of COBs above ∼1 keV, while the COB PSD is typically higher than that of O + at FAST at energies <∼1 keV. These results suggest that the trapped O + in the dayside magnetosphere is a potential source of COBs at energies above 1 keV, while for COBs below 1 keV, polar O + outflows from the cusp/cleft regions are the most probable source, as suggested by a conventional view.