H alpha polarization during a well-observed solar flare: Proton energeticsand implications for particle acceleration processes

Observations of polarization of chromospheric lines in solar hares can cons train the energy flux in accelerated protons. In this paper we analyze rece ntly reported observations of H alpha linear polarization obtained during a rather well observed hare on 1989 June 20. Modeling of the magnitude and o rientation of the H alpha polarization provides a constraint on the flux of low energy (greater than or similar to 200 keV) protons, while simultaneou s gamma-ray and hard X-ray observations provide constraints on the fluxes o f greater than or similar to 10 MeV protons and greater than or similar to 50 keV electrons, respectively. These, plus information on the energetics o f the low-temperature and high-temperature thermal emissions, permit evalua tion of both the absolute and relative roles of electrons and protons in th e flare energy budget. We find that accelerated protons with energies great er than or similar to 200 keV can contain a significant portion of the tota l energy released during the flare, consistent with a steep extrapolation o f the proton spectrum to such relatively low energies. We discuss these res ults in light of a unified electron/proton stochastic particle acceleration model and show that the energetics are indeed consistent with this large p roton energy content.