Abstract
A unique combination of Solar Maximum Mission X-ray spectra and Sacramento Peak Observatory Hα imaging spectra has enabled us, for the first time, to measure and compare momentum values of upflowing and downflowing plasmas during the impulsive phase of a solar flare. We observed the well-known blue asymmetry of X-ray spectral lines1, indicative of upflow, in the coronal Ca XIX line. We simultaneously observed the red asymmetry of Hα line profiles, indicative of downflow, in bright Ha kernels. We find that, to within observational uncertainty, the momentum transported by the upflowing X-ray plasma was the same as that of the downflowing Hα material. Of the several physical mechanisms advanced2 to explain the observed blue asymmetry of X-ray lines, only explosive chromospheric evaporation predicts oppositely directed momenta of equal amplitude.
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