上游太阳风对木星热层流动的影响
Influence of upstream solar wind on thermospheric flows at Jupiter
摘要：
木星的磁层和电离层的耦合在产生极光发射方面起着至关重要的作用。这些辐射的强度取决于木星高纬度热层和行星磁盘内旋转流的速度差异。利用一个方位对称的全球环流模式，模拟了上游太阳风条件对大气流动能量和方向的影响。为了模拟上游太阳风中动态压力变化的影响，我们计算了三个磁场剖面，分别代表压缩、平均和膨胀的“中间”磁层。然后，这些配置文件被用来解决磁层中的等离子体的角速度。这个角速度决定了在电离层和磁层之间流动的电流的强度。我们研究的影响，在目前的系统对全球的风和能量输入木星热层内的变化。我们发现，焦耳热和离子阻力消耗的功率从我们的压缩到扩展模型分别增加了约190%和约185%。我们研究了外部边界条件对我们模型的影响，发现通过减少磁盘外缘的径向电流，我们也限制了热层向该区域传输角动量的能力。
英文摘要：
The coupling of Jupiter's magnetosphere and ionosphere plays a vital role in creating its auroral emissions. The strength of these emissions is dependent on the difference in speed of the rotational flows within Jupiter's high-latitude thermosphere and the planet's magnetodisc. Using an azimuthally symmetric global circulation model, we have simulated how upstream solar wind conditions affect the energy and direction of atmospheric flows. In order to simulate the effect of a varying dynamic pressure in the upstream solar wind, we calculated three magnetic field profiles representing compressed, averaged and expanded `middle' magnetospheres. These profiles were then used to solve for the angular velocity of plasma in the magnetosphere. This angular velocity determines the strength of currents flowing between the ionosphere and magnetosphere. We examine the influence of variability in this current system upon the global winds and energy inputs within the Jovian thermosphere. We find that the power dissipated by Joule heating and ion drag increases by ~190% and ~185% from our compressed to expanded model respectively. We investigated the effect of exterior boundary conditions on our models and found that by reducing the radial current at the outer edge of the magnetodisc, we also limit the thermosphere's ability to transmit angular momentum to this region.
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