05/02/02
Balanca Christian	Observatoire de Paris
5, place J. Janssen	PNST- ENS
92195	Meudon, France

Presentation 1 : Poster
Polarization and collisions in the solar atmosphere
C. Balança and N. Feautrier
Collisions present in the solar atmosphere must be taken into account for polarization line studies. Two very different effects occur according to the angular distribution of the velocities leading either to polarization or depolarization of the lines. The first case is illustrated by its application to the diagnostic of proton beams in solar flares~: the direction of polarization depends on the initial energy distribution of the beam, before propagation in the atmosphere. The case of isotropic collisions is discussed in the context of the interpretation of the "second solar spectrum" as observed with THEMIS.

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