Wind observations of mixed magnetosheath-plasma sheet ions deep inside the magnetosphere
Wind observations of mixed magnetosheath-plasma sheet ions deep inside the magnetosphere
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DOI：
10.1029/1999ja900455
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发表时间：
2000-03-01
影响因子：
2.8
通讯作者：
Fujimoto, M
中科院分区：
文献类型：
--
作者：
Phan, TD;Lin, RP;Fujimoto, M
我们详细分析了1998年11月27日风航天器穿越高纬度磁鞘，磁层顶，叶，和高，低纬度等离子体片。这次穿越发生在风号（新的）高倾角（45度）花瓣轨道的第一次近地点通过期间。在波瓣和黄昏侧的热等离子体片之间，探测到一个扩展区域（x（GSM）近似于-2.8到-7.8R（E），y（GSM）近似于7. 8 R-E，z（GSM）近似于-11.6到-4. 3R-E），是低能磁鞘和高能等离子体片离子混合的区域。这个区域是在一个强（类似于40 nT）和稳定的波瓣状磁场区域中探测到的，当航天器接近中性片时，这个区域就不复存在了。混合离子种群是非常相似的（在其热性能）在相邻的磁鞘和等离子体片适当的分布检测，除了混合离子几乎停滞。当接近中性片时，混合离子的低能量成分逐渐被加热，而高能量成分未被改变。在中性层附近，离子分布主要由单一的高能粒子群控制。电子的行为与离子的行为明显不同。在混合离子区，电子由单一的人口之间的磁鞘和等离子体片本身的能量。电子俯仰角信息表明，整个混合区是封闭的场线。然而，高能量等离子体片电子在该区域中的大幅减少可能表明穿过该区域的场线曾经是开放的。等离子体进入以形成混合区域的确切路径不能用单点观察来辨别，特别是因为混合离子是停滞的。然而，（对于这一事件）有可能排除地幔作为混合离子低能成分的来源。混合离子和磁鞘人口的低能量成分的热性能之间的相似性表明，磁鞘等离子体直接进入这一地区没有显着的加热沿着其路径。存在的几乎未修改的磁鞘等离子体深处的磁层，提出了有关等离子体进入磁层顶的过程的问题。最后，在此事件中的混合区被检测到在一个持久的向北和黄昏行星际磁场，这使得这一事件理想的模式比较的延长期。
We have analyzed in detail a Wind spacecraft crossing of the high-latitude magnetosheath, magnetopause, lobe, and the high- and low-latitude plasma sheet on November 27, 1998. The crossing occurred during the first perigee pass of Wind's (new) high-inclination (45 degrees) petal orbit. Between the lobe and the hot plasma sheet on the duskside, an extended region (x(GSM)similar to -2.8 to -7.8R(E), y(GSM)similar to 7.8 R-E, z(GSM)similar to -11.6 to -4.3 R-E) of mixed low-energy magnetosheath and high-energy plasma sheet ion populations was detected. This region was detected in a region of strong (similar to 40nT) and steady lobe-like magnetic field and ceased to exist when the spacecraft approached the neutral sheet. The mixed ion populations are remarkably similar (in their thermal properties) to the distributions detected in the adjacent magnetosheath and plasma sheet proper, except that the mixed ions are nearly stagnant. As the neutral sheet is approached, the low-energy component of the mixed ions is gradually heated, while the high-energy component is unmodified. Near the neutral sheet the ion distributions are dominated by a single, high-energy population. The electron behavior is significantly different from that of the ions. In the mixed ion region the electrons consist of a single population with energy between those of the magnetosheath and the plasma sheet proper. Electron pitch angle information suggests that the entire mixed region is on closed field lines. However, the large reduction of high-energy plasma sheet electrons in this region may indicate that the field lines threading this regions were once open. The exact path of plasma entry to form the mixed region cannot be discerned with single-point observations, especially since the mixed ions are stagnant. However, it is possible (for this event) to rule out the mantle as a source for the low-energy component of the mixed ions. The similarity between the thermal property of the low-energy component of the mixed ions and the magnetosheath population suggests that the magnetosheath plasma had direct access to this region without significant heating along its path. The presence of nearly unmodified magnetosheath plasma deep inside the magnetosphere, raises questions concerning the processes of plasma entry across the magnetopause. Finally, the mixed region in this event was detected during an extended period of persistent northward and duskward interplanetary magnetic field, which makes this event ideal for model comparisons.