Electrons under the dominant action of shock-electric fields
Electrons under the dominant action of shock-electric fields
复制标题
冲击电场主导作用下的电子
DOI：
--
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发表时间：
2016
期刊：
影响因子：
--
通讯作者：
D. Verscharen
中科院分区：
文献类型：
--
作者：
H. Fahr;D. Verscharen
我们认为一个快速的磁声多流体激波作为太阳风终止激波的代表。我们假设转变的过程分为三步：第一步，上游的超音速太阳风等离子体受到一个强电场的作用，这个电场在一个小的距离尺度$\Delta z\simeq U_1/ \Omega _{\mathrm e}$（过渡层的第一部分）上闪烁，其中$\Omega_{\mathrm e}$是电子回旋频率，$U_1$是上游的速度。该电场既使超音速离子流减速又使电子加速到高速。在过渡区的这一部分中，与离子流的减速有关的电力强烈地支配洛伦兹力。因此，我们称这部分为退磁区。在第二阶段，由于对流磁场的洛伦兹力与电场竞争，并且高度各向异性和高能电子分布函数被转换成壳分布，其中高能壳电子存储约3/4的上游离子动能。在第三阶段中，等离子体粒子由于等离子体不稳定性引起的自由能松弛而热化。过渡区的第一部分开辟了一个新的热力学自由度，以前从未考虑过电子，因为电子通常被认为是受控的，以遵循质子在所有速度时刻的行为，如密度，体积速度和温度。我们表明，电子可能是下游等离子体流体，主导下游等离子体压力。
We consider a fast magnetosonic multifluid shock as a representation of the solar-wind termination shock. We assume the action of the transition happens in a three-step process: In the first step, the upstream supersonic solar-wind plasma is subject to a strong electric field that flashes up on a small distance scale $\Delta z\simeq U_1/ \Omega _{\mathrm e}$ (first part of the transition layer), where $\Omega_{\mathrm e}$ is the electron gyro-frequency and $U_1$ is the upstream speed. This electric field both decelerates the supersonic ion flow and accelerates the electrons up to high velocities. In this part of the transition region, the electric forces connected with the deceleration of the ion flow strongly dominate over the Lorentz forces. We, therefore, call this part the demagnetization region. In the second phase, Lorentz forces due to convected magnetic fields compete with the electric field, and the highly anisotropic and energetic electron distribution function is converted into a shell distribution with energetic shell electrons storing about 3/4 of the upstream ion kinetic energy. In the third phase, the plasma particles thermalize due to the relaxation of free energy by plasma instabilities. The first part of the transition region opens up a new thermodynamic degree of freedom never before taken into account for the electrons, since the electrons are usually considered to be enslaved to follow the behavior of the protons in all velocity moments like density, bulk velocity, and temperature. We show that electrons may be the downstream plasma fluid that dominates the downstream plasma pressure.
影响因子：
6.5
作者：
H. Fahr;M. Siewert
通讯作者：
H. Fahr;M. Siewert
影响因子：
6.5
作者：
H.-J. ;Siewert
通讯作者：
Siewert