Needs and constraints for coordinated programs of photospheric and chromospheric studies of flares
Abstract
Suggestions for a coordinated observing program of the photospheric and chromospheric components of a flare are given; the maximum efficiency can be reached only if simultaneous measurements of coronal emission component may be obtained. The observing program has to be changed according to the different characteristics of a flare in each phase of its development. During the build-up phase it is of particular interest to establish the correlation between the photospheric velocity field (determined from bidimensional spectroscopic images in the 5576 Fe I line) and the magnetic field. During the transient explosive phase particular emphasys should be given to high time resolution observations (at least 1 sec) in order to correlate the response of chromospheric and photospheric signatures to the energy release producing the impusive phase in the hard X-ray and microwave emission. Observations with different filters in the center and red wing of the Hα line, in CN (0-0) band and in some continuous windows are suggested in order to have time and spatial resolution as high as possible. Spectral observations in the region 3400 - 4300 Å give the possibility to measure the red shift of the Balmer lines presumably associated to the chromospheric condensation moving downward. When the flare atmosphere may be considered in pressure balance (after tens of seconds) the time resolution is not crucial and the Hα and Na-D2 line profile may be obtained with the Zeiss and UBF filter used in bidimensional spectroscopic mode. Hα line gives the possibility to test the effect of the heating mechanism while the Na-D2 line is useful to monitor the penetration depth of the flare disturbance.
- Publication:
-
Advances in Space Research
- Pub Date:
- 1991
- DOI:
- 10.1016/0273-1177(91)90362-N
- Bibcode:
- 1991AdSpR..11e..85F
- Keywords:
-
- Chromosphere;
- Imaging Spectrometers;
- Photosphere;
- Solar Corona;
- Solar Flares;
- H Alpha Line;
- Microwave Emission;
- Spatial Resolution;
- Spectral Signatures;
- X Ray Irradiation;
- Astronomy