Line profiles in moustaches produced by an impacting energetic particle beam

The Hα line profile in moustaches is characterized by enhanced wings and a deep central absorption. We explore the possibility that such a profile may be due to the effect of energetic particles bombarding the atmosphere. Computations show that the characteristics of moustache line profiles can be qualitatively reproduced in two extreme cases, either injection from the corona of high energy particles (>∼ 60 keV electrons or >∼ 3 MeV protons) or injection in a low-lying site, in middle chromosphere or deeper, of less energetic particles (∼ 20 keV electrons or ∼ 400 keV protons). The requirements on the energy and on the depth of the injection site of energetic particles are reduced in the case of observations close to the solar limb. The rôle of protons of energies below 1 MeV is slightly less significant than that of deka-keV electrons in the case of a high particle injection site, but such protons remain to be viable candidates in the case of lower particle injection sites and of observations at larger heliocentric angles. Observations at various wavelengths are needed to find which of these hypotheses is convenient for explaining a given event.