Soft X{ray and Gyroresonance Emission above Sunspots

Using Yohkoh SXT and Nobeyama 17 GHz data, we have studied the soft X{ray and microwave emission above several stable, large sunspots near central meridian passage. Our study connrms the well known fact that soft X{ray emission is depressed above sunspots. It also shows that the distribution of their soft X{ray intensity is not uniform; usually the darkest pixels are associated with the umbra or the far edges of the leading part of the penumbra while the following part of the penumbra may contain higher intensity pixels associated with brighter loops. For the rst time, we present a systematic survey of the temperatures and emission measures of the soft X{ray material above sunspots. Sunspots always contain the lowest temperatures and emission measures in the active regions. The mean umbral temperature is 1:8 10 6 K and the mean penumbral temperature is 2:4 10 6 K. The mean umbral and penumbral emission measures are log EM = 26:60 cm ?5 and log EM = 27:00 cm ?5 , respectively. The diierences between the umbral and penumbral plasma temperatures are physically signiicant. The higher penumbral values imply that the loops associated with the penumbrae are generally hotter and denser than the loops associated with the umbrae. The highest sunspot temperatures and emission measures are still lower than the average active region parameters but higher than the quiet Sun plasma parameters. The coronal radiative energy loss rate above the umbrae is 15% higher than the radiative loss rate of the quiet Sun plasma but a factor of 8.3 lower than the typical active region radiative loss rate. The radio emission comes from the gyroresonance mechanism and as expected, it is sensitive to the magnetic eld rather than the soft X{ray emitting plasma.