Three‐dimensional lunar wake reconstructed from ARTEMIS data
Three‐dimensional lunar wake reconstructed from ARTEMIS data
复制标题
DOI：
10.1002/2014ja020111
复制
发表时间：
2014-07
期刊：
影响因子：
--
通讯作者：
H. Zhang;K. Khurana;M. Kivelson;V. Angelopoulos;W. Wan;L. Liu;Q. Zong;Z. Pu;Q. Shi;W. L. Liu
中科院分区：
文献类型：
--
作者：
H. Zhang;K. Khurana;M. Kivelson;V. Angelopoulos;W. Wan;L. Liu;Q. Zong;Z. Pu;Q. Shi;W. L. Liu
来自两个航天器的加速、重联、湍流和月球与太阳相互作用的电动力学数据已经被利用，以前所未有的保真度来表征月球尾流。航天器在离月球很近的太阳风中进行的测量与另一艘航天器在近月球尾流中同时进行的测量之间的差异很小，但却是系统的。它们使我们能够建立等离子体密度、温度、热、磁和总压力、场的扰动，以及月球下游12个月球半径（RM）的流动。尾迹扰动是在月球后方由月球终端线处的反磁电流引起的。稀薄波以高速MHD波速向外传播。超过~6.5 RM，所有的等离子体和场参数结构都很差，这表明存在由逆流粒子激发的不稳定性。通过压力梯度力和双极电场加速向内流动的等离子体压缩磁场，导致磁扰动幅度不断增加。除了下游距离外，磁场扰动幅度也是太阳风离子β和太阳风与行星际磁场夹角（IMF）的函数。离子和电子温度的升高是能量色散效应的结果，其解释需要完全的动力学模型。在月球的下游，国际货币基金组织磁场线被观测到向月球方向凸起，这是意想不到的，可能是由等离子体压力梯度力或/和月球后面重带电尘埃颗粒的拾取引起的。
Data from the two‐spacecraft Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun mission to the Moon have been exploited to characterize the lunar wake with unprecedented fidelity. The differences between measurements made by a spacecraft in the solar wind very near the Moon and concurrent measurements made by a second spacecraft in the near lunar wake are small but systematic. They enabled us to establish the perturbations of plasma density, temperature, thermal, magnetic and total pressure, field, and flow downstream of the Moon to distances of 12 lunar radii (RM). The wake disturbances are initiated immediately behind the Moon by the diamagnetic currents at the lunar terminator. Rarefaction waves propagate outward at fast MHD wave velocities. Beyond ~6.5 RM, all plasma and field parameters are poorly structured which suggests the presence of instabilities excited by counter‐streaming particles. Inward flowing plasma accelerated through pressure gradient force and ambipolar electric field compresses the magnetic field and leads to continuous increase in magnitude of magnetic perturbations. Besides the downstream distance, the field perturbation magnitude is also a function of the solar wind ion beta and the angle between the solar wind and the interplanetary magnetic field (IMF). Both ion and electron temperatures increase as a consequence of an energy dispersion effect, whose explanation requires fully kinetic models. Downstream of the Moon, the IMF field lines are observed to bulge toward the Moon, which is unexpected and may be caused by a plasma pressure gradient force or/and the pickup of heavy charged dust grains behind the Moon.