HIGH SPATIAL-RESOLUTION SOLAR PHOTOSPHERIC LINE OBSERVATIONS IN CA+ ACTIVE REGIONS

Spatially highly resolved solar photospheric line profiles were analysed by the calculation of bisectors, line center velocities and line asymmetries to investigate the influence of magnetic fields on these parameters. We used a set of three selected spectrograms which contained regions of different magnetic activity. In the active regions both, a reduction of continuum intensity fluctuations as well as small scale velocity fluctuations, was confirmed. However, on subgranular scales the continuum intensity fluctuations and the line center velocities for lines originating higher than 200 km in the photosphere increased in active regions and became equal or even higher than in non-active regions. The spatially highly resolved line profiles also showed significant changes. The mean line asymmetry was negative in non-active and positive with a reduction of the standard deviation in active regions. Thus the interaction of the magnetic field with the plasma reduces the velocity gradients as also shown by spatially highly resolved bisectors in both non-active and active regions. The results found here are in accordance with the general concept that magnetic flux is concentrated in small fluxtubes which themselves concentrate in downflow regions.