Robert F. Willson

Structure of a solar active region from Ratan 600 and very large array observations

Observations de la region active solaire AR 3804 les memes jours de juillet 1982 avec le RATAN 600 et le VLA

Magnetospheres of solar active regions inferred from spectral-polarization observations with high spatial resolution

The strong magnetic fields of active regions organize both the plasma structures and energy processes in the chromosphere and corona. Recent radio observations with high spatial resolution permit measurements of the magnetic fields in these regions and also localize regions of thermal and nonthermal energy release. They can additionally be used to determine temperatures and electron densities in these regions. The results of such diagnostics suggest the term magnetosphere for the space surrounding an active region in the solar atmosphere where the basic structures and physical processes are controlled by the magnetic fields/electric currents of the particular region

Coronal magnetic structures observing campaign. IV - Multiwaveband observations of sunspot and plage-associated coronal emission

Results of simultaneous observations of an active region located near the central meridian obtained on December 18, 1987, are presented. An asymmetric looplike structure connects the strong leading sunspot with a nearby region of opposite polarity. Both 6- and 20-cm emission lie along this structure, rather than over the sunspot, with higher frequency emission originating closer to the footpoint inside the sunspot. The 20-cm emission is due to a superposition of second- and third-harmonic gyroemission, where the field strength is 160-300 G, while the 6-cm emission is due to third-harmonic gyroemission from a region where the magnetic field strength ranges from 547 to 583 G. X-ray data associated with an area of trailing plage are used to predict the brightness temperature structure due to thermal bremsstrahlung emission in the 6- and 20-cm wavebands.