Reconciling spectroscopic electron temperature measurements in the solar corona with in situ charge state observations

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, w e 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 distributio n function has to be Maxwellian or dose 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 propertie s inside of a few solar radii, and (3) ions of different elements have to f low with significantly different speeds to separate their "freezing-in" dis tances sufficiently so that they can encounter different distribution funct ions. We choose two examples to demonstrate that these conditions are gener al requirements if both coronal electron temperatures and in situ ion fract ions are correct. However, these two examples also show that the details of the required distribution functions are very sensitive to the exact electr on temperature, density, and ion flow speed profiles in the region of the c orona where the ions predominantly form.