Dreicer电场定义与太阳耀斑中的逃逸电子
Dreicer electric field definition and runaway electrons in solar flares
AI总结：
本文基于Dreicer和Spitzer方法分析太阳耀斑日冕条件下电场对电子的加速，指出常用Dreicer电场定义使其值被高估约5倍，且部分研究因忽略库仑碰撞低估了临界速度，发现亚Dreicer电场加速电子存在困难。
摘要：
我们基于Dreicer和Spitzer提出的电子动态摩擦力方法，分析了在太阳耀斑日冕条件下碰撞氢等离子体中大规模电场$E$对电子的加速作用。Dreicer电场$E_{Dr}$被确定为使整个电子群发生逃逸的临界电场。讨论了强电场（$E \lesssim E_{Dr}$）和弱电场（$E \ll E_{Dr}$）两种情况。结果表明，常用的Dreicer电场形式化定义导致其值被高估约5倍。由于未考虑逃逸电子与热电子之间的库仑碰撞，某些工作中Maxwell分布“尾部”电子在亚Dreicer电场作用下变为逃逸电子的临界速度被低估了$\sqrt{3}$倍。在日冕中产生的亚Dreicer电场加速电子面临困难。
英文摘要：
We analyse electron acceleration by a large-scale electric field $E$ in a collisional hydrogen plasma under the solar flare coronal conditions based on approaches proposed by Dreicer and Spitzer for the dynamic friction force of electrons. The Dreicer electric field $E_{Dr}$ is determined as a critical electric field at which the entire electron population runs away. Two regimes of strong ($E \lesssim E_{Dr}$) and weak ($E \ll E_{Dr}$) electric field are discussed. It is shown that the commonly used formal definition of the Dreicer field leads to an overestimation of its value by about five times. The critical velocity at which the electrons of the ``tail'' of the Maxwell distribution become runaway under the action of the sub-Dreiser electric fields turns out to be underestimated by $\sqrt{3}$ times in some works because the Coulomb collisions between runaway and thermal electrons are not taken into account. The electron acceleration by sub-Dreicer electric fields generated in the solar corona faces difficulties.
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