Esser R, Edgar RJ
Astrophys J. 2000 Mar 20;532(1):L71-L74. doi: 10.1086/312548.
It has been a puzzle for quite some time that spectroscopic measurements in the inner corona indicate electron temperatures far too low to produce the ion fractions observed in situ in the solar wind. In the present Letter, we show that in order to reconcile the two sets of measurements, a number of conditions have to exist in the inner corona: (1) The electron distribution function has to be Maxwellian or close to Maxwellian at the coronal base, (2) the non-Maxwellian character of the distribution has to develop rapidly as a function of height and has to reach close to interplanetary properties inside of a few solar radii, and (3) ions of different elements have to flow with significantly different speeds to separate their "freezing-in" distances sufficiently so that they can encounter different distribution functions. We choose two examples to demonstrate that these conditions are general requirements if both coronal electron temperatures and in situ ion fractions are correct. However, these two examples also show that the details of the required distribution functions are very sensitive to the exact electron temperature, density, and ion flow speed profiles in the region of the corona where the ions predominantly form.
一段时间以来，一个谜题始终存在：日冕内层的光谱测量显示，电子温度过低，无法产生在太阳风原位观测到的离子比例。在本信函中，我们表明，为了协调这两组测量结果，日冕内层必须存在若干条件：（1）在日冕底部，电子分布函数必须是麦克斯韦分布或接近麦克斯韦分布；（2）分布的非麦克斯韦特性必须随高度迅速发展，并且必须在几个太阳半径范围内接近行星际特性；（3）不同元素的离子必须以显著不同的速度流动，以充分分离它们的“冻结”距离，以便它们能够遇到不同的分布函数。我们选择两个例子来证明，如果日冕电子温度和原位离子比例都是正确的，那么这些条件是普遍要求。然而，这两个例子也表明，所需分布函数的细节对离子主要形成区域的精确电子温度、密度和离子流速剖面非常敏感。
