Absence of linear polarization in Hα emission of solar flares
Additional information
Authors
Type
Journal Article
Year
2005
Language
English
Abstract
High sensitivity observations of Hα polarization of 30 flares of different sizes and disk positions are reported. Both filter and spectrographic techniques have been used. The ZIMPOL system eliminates spurious polarizations due to seeing and flat-field effects. We didn't find any clear linear polarization signature above our sensitivity level which was usually better than 0.1%. The observations include an X17.1 flare with gamma-ray lines reported by the RHESSI satellite. These results cast serious doubts on previous claims of linear polarization at the one percent level and more, attributed to impact polarization. The absence of linear polarization limits the anisotropy of energetic protons in the Hα emitting region. The likely causes are isotropization by collisions with neutrals in the chromosphere and defocusing by the converging magnetic field.
Journal
Astronomy and Astrophysics
Volume
434
Start page number
1183
End page number
1189
Keywords
irsol-refereed-scientific-papers
