CORONAL MAGNETIC-STRUCTURES OBSERVING CAMPAIGN .4. MULTIWAVEBAND OBSERVATIONS OF SUNSPOT AND PLAGE-ASSOCIATED CORONAL EMISSION

Simultaneous observations of an active region located near central meridian were obtained with the Very Large Array, the Solar Maximum Mission X-Ray Polychromator, and the Beijing Observatory magnetograph on 1987 December 18, during the Coronal Magnetic Structures Observing Campaign (CoMStOC). 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. A high value of the Alfven speed, approximately 40,000 km s-1, is obtained at the location of the 6 cm source, with somewhat lower values, approximately 10,000-20,000 km s-1, at the location of the 20 cm emission. At the location of the 6 cm source, the plasma temperature diminishes with height from 2.5 x 10(6) K at approximately 5000 km to 1.3 x 10(6) K at approximately 15,000 km. The X-ray data associated with an area of trailing plage were used to predict the brightness temperature structure due to thermal bremsstrahlung emission in the 6 and 20 cm wavebands. The predicted 6 cm brightness temperature in and around the location of the X-ray peak is low, consistent with our lack of observed 6 cm plage emission. The predicted 20 cm brightness temperature is consistent with that observed in the central portions of the page, but the high 20 cm polarization requires the presence of cool (T(e) less-than-or-equal-to 5 x 10(5) K), absorbing plasma overlying the hot plasma observed in X-rays. Two different models for interpreting these observations are described.