Line-Broadening in Solar Flares

Balmer line formation in solar flares affected by return currents

Aims. We investigate the effect of the electric return currents in solar flares on the profiles of hydrogen Balmer lines. We consider the monoenergetic approximation for the primary beam and runaway model of the neutralizing return current. Methods. Propagation of the 10 keV electron beam from a coronal reconnection site is considered for the semiempirical chromosphere model F1. We estimate the...

Hα-line impact polarisation by electron beams in solar flares

The Hα-line intensity, linear and circular impact polarisation were calculated during the impulsive phase of flares using the density matrix approach. Depolarising effects of diffusive radiation and collisions with thermal electrons are considered for a 3 levels Hydrogen model atom with Zeeman splitting in weak and intermediate magnetic fields. Electron beam energy and angular distributions in ...

Solar transition region line broadening: Limb to limb measurements

Full disk images from SUMER/SoHO taken in He i, C iv and Ne viii are used to investigate whether there exists a center-to-limb variation in the line width. Both C iv and He i show such a variation but the higher temperature Ne viii line is relatively constant. For C iv, this corresponds to ∼ 3 km s−1 difference while He i is significantly larger particularly at the limb. This work may suggest t...

7Li PRODUCTION IN SOLAR FLARES

The Y ohkoh satellite has registered X-ray spectra of two solar Ñares with a linelike feature in the region 400È500 keV. Analysis shows that this feature can be interpreted as gamma-ray lines from excited 7Li and 7Be produced from a ] a reactions. The 7Li production rate in the solar atmosphere is estimated from these observations. The lower limit on the Ñare-produced 7Li abundance on the Sun i...

Global Properties of Solar Flares