A mechanism for deep chromospheric heating during solar flares

MACHADO, M.E.; EMSLIE, A.G.; MAUAS, P J D

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 1986 vol. 159 p. 33 - 39

0004-6361

The authors reexamine the role of the negative hydrogen ion, H-, in the energy balance of the deep solar chromosphere and find, in contrast with earlier authors, that H- is a source of heating in these levels. The response of this region to an ionizing flux of flare-associated UV radiation (1500 ⪉ λ ⪉ 1900 Å) is then addressed: the authors find that the excess ionization of Si to Si+ increases the local electron number density considerably, since most species are largely neutral at deep chromospheric levels. This in turn increases the electron-hydrogen atom association rate, the H- abundance, and the rate of absorption of photospheric radiation by this ion. The authors find that the excess absorption by this process may lead to a substantial temperature enhancement at temperature minimum levels during flares.