太阳风中的电子热传导：从Spitzer-Härm到无碰撞极限的转变
Electron heat conduction in the solar wind: transition from Spitzer-Härm to the collisionless limit
摘要：
我们使用一组统计上显着的测量表明，在太阳风在1 AU的场对齐的电子热通量$q_\parallel$是一致的斯皮策-Härm碰撞热通量$q_{sh}$的温度梯度尺度大于几个平均自由程$L_T \gtrsim 3.5 ~λ_{fp}$。这代表了大约65%的测量数据，主要对应于高$β$，弱碰撞等离子体（“慢太阳风”）。在更无碰撞的状态$λ_{fp}/L_T \gtrsim 0.28$中，电子热通量被限制为$q_\parallel/q_0 \sim 0.3$，与平均自由程无关，其中$q_0$是“自由流”值;测量的$q_\parallel$没有达到完全的$q_0$。这种限制$q_\parallel/q_0 \sim 0.3$可能是由于波粒相互作用，行星际电势，或固有的通量限制。我们还表明$β_e$依赖于这些结果是一致的局部径向电子温度分布$T_e \sim r^{-α}$，这是一个功能的热电子β $α= α(β_e)$和$β$依赖的无碰撞监管约束是不明显一致的哨声热通量不稳定性。我们在更广泛的天体物理学背景下讨论结果。
英文摘要：
We use a statistically significant set of measurements to show that the field-aligned electron heat flux $q_\parallel$ in the solar wind at 1 AU is consistent with the Spitzer-Härm collisional heat flux $q_{sh}$ for temperature gradient scales larger than a few mean free paths $L_T \gtrsim 3.5 ~λ_{fp}$. This represents about 65% of the measured data and corresponds primarily to high $β$, weakly collisional plasma ('slow solar wind'). In the more collisionless regime $λ_{fp}/L_T \gtrsim 0.28$, the electron heat flux is limited to $q_\parallel/q_0 \sim 0.3$, independent of mean free path, where $q_0$ is the 'free-streaming' value; the measured $q_\parallel$ does not achieve the full $q_0$. This constraint $q_\parallel/q_0 \sim 0.3$ might be attributed to wave-particle interactions, an interplanetary electric potential, or inherent flux limitation. We also show a $β_e$ dependence to these results that is consistent with a local radial electron temperature profile $T_e \sim r^{-α}$ that is a function of the thermal electron beta $α= α(β_e)$ and that the $β$ dependence of the collisionless regulation constraint is not obviously consistent with a whistler heat flux instability. We discuss the results in a broader astrophysical context.
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