Non-LTE Calculation of the Ni I 676.8 nm Line in a Flaring Atmosphere
Abstract
The Ni I 676.8 nm line is used by SOHO/MDI to measure the magnetic field and velocity field in the solar atmosphere. We make non-LTE calculations of this line in a flaring atmosphere which is heated by an energetic electron beam. The electron beam produces nonthermal ionization and excitation of the hydrogen atoms and redistributes the level populations. This results in an enhanced opacity near the Ni I line and an upward shift of its formation height. We find that the line may appear emission in the presence of a fairly strong electron beam. On the other hand, if there is no bombarding electron beam, the profile can hardly turn to emission even though the atmosphere may be heated through other ways. This result implies that at least in some cases, the sign reversal of the longitudinal magnetic field observed in some flare events may not be a true reversal, but just an artifact associated with the production of an emission profile.
- Publication:
-
American Astronomical Society Meeting Abstracts #200
- Pub Date:
- June 2002
- Bibcode:
- 2002AAS...200.9103D