It is well known that collisionless systems are dissipation free from the perspective of particle collision and thus conserve entropy. However, processes such as magnetic reconnection and turbulence appear to convert large-scale magnetic energy into heat. In this paper, we investigate the energization and heating of collisionless plasma. The dissipation process is discussed in terms of fluid entropy in both isotropic and gyrotropic forms. Evolution equations for the entropy are derived and they reveal mechanisms that lead to changes in fluid entropy. These equations are verified by a collisionless particle-in-cell simulation of multiple reconnecting current sheets. In addition to previous findings regarding the pressure tensor, we emphasize the role of heat flux in the dissipation process.

中文翻译：

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无碰撞等离子体中的能量耗散和熵

众所周知，无碰撞系统从粒子碰撞的角度来看是无耗散的，因此可以保持熵。但是，诸如磁重连接和湍流之类的过程似乎会将大规模的磁能转化为热量。在本文中，我们研究了无碰撞等离子体的通电和加热。分别以各向同性和回旋形式的流体熵来讨论耗散过程。导出了熵的演化方程，并揭示了导致流体熵变化的机理。这些方程式通过多个重新连接的电流表的无碰撞粒子模拟进行验证。除了先前关于压力张量的发现外，我们还强调了热通量在耗散过程中的作用。