Velocity distribution function anisotropy of soft X-ray generated photoelectrons and resulting H alpha polarization in solar flares

Soft X-rays irradiation of the solar atmosphere during solar flares generat es photoelectrons which have an anisotropic velocity distribution. Using a 1-D test particle code, the anisotropy of the photoelectrons velocity distr ibution is derived, and the maximum degree of linear polarization in the hy drogen Ha and HP lines that photoelectrons could generate by impact is esti mated. Over a band pass of 0.75 and 0.5 Angstrom, the net polarization degr ee expected in both lines is predicted not to exceed 0.2%. Therefore, soft X-ray irradiation cannot explain the one order of magnitude higher degree o f linear polarization observed in solar flares.