SOHO JOP047 Title: Correlations of Minutescale Changes in the Corona and Chromosphere above the Network of the Quiet Sun (Joint Observations with Radio and Optical Groundbased Observatories) Contributors: SOHO: R. Harrison (CDS), B. Thompson (EIT), tbd (SUMER) Groundbased: A.O. Benz (PI VLA), T.S. Bastian (VLA), C.U. Keller (NOAO) Basic idea: In our previous VLA observations of Feb-20-95 we have seen radio brightenings of 10 minutes total duration in the network of the quiet Sun correlating with soft X-ray peaks. Now we want to investigate their correlation with UV and EUV activity (intensity and Doppler shift) at a resolution of a few arcseconds. Some details on ground based instruments: Radio: We have received observing time at the Very Large Array and at Kitt Peak to observe the magnetic network of the QUIET SUN in radio and optical wavelengths at one minute time resolution. All observations will have spatial resolutions of a few arcseconds. The VLA observing times are: 1996, July 12, 13:47:30 - 21:46:15 UT 1996, July 27, 14:48:15 - 22:47:00 UT The three proposed radio frequencies will sample the upper chromosphere and transition region in short snapshots (3 minute time resolution) and long-duration single-frequency scans (20s time resolution). The origin of radio emission is mostly thermal bremsstrahlung from the upper chromosphere, but non-thermal contributions cannot be excluded. Optical: At Kitt Peak, the Zurich Imaging Stokes Polarimeter ZIMPOL will record the full Stokes vector at the 1.5 m McMath-Pierce telescope at Kitt Peak with up to four CCD cameras in parallel in various spectral lines to determine the magnetic field vector at various heights in the photosphere and the lower chromosphere. The Vacuum Telescope will be equipped with a narrow-band filter and a CCD camera to record magnetograms in the He I 10830 \AA\ line to determine the longitudinal component of the magnetic field vector in the lower corona. Pointing: It is essential for the VLA to point into a quiet region. The closest active region should be at least 5 arcminutes from the center of the field of view. As a first approximation we propose to observe the center of the Sun. This may have to shifted if the center is not quiet. Field of view: The VLA has a circular field of view depending on wavelength with the following diameters: 1.3 cm 138" 2.0 cm 212" 3.6 cm 328" SOHO observations: Here we propose joint observations by the two (and possibly other, incl YOHKOH) groundbased facilities with SOHO to investigate the energy input into the transition region and lower corona. To achieve sufficient resolution for temporal correlations, we request temporal resolutions of 3 minutes during the tree-frequency mode of the VLA and one minute resolution during the single-frequency scan. SUMER Observation Sequence Tentative pointing Center of Sun (if no activity) Slit Scan Area Step Size Resulting Number of Scan Locations Dwell Time Duration of Scan Line Selection Spectral Binning Estimated Reduction Factor Selection Compression Reduction -> CDS Observation Sequence Tentative pointing Center of Sun (if no activity) Slit 2" x 240" Scan Area 20" x 240" Resulting Number of Scan Locations 10 Dwell Time Duration of Scan Line Selection Spectral Binning 15 Compression Total image time (cadence) 2 minutes EIT Observation Sequence Tentative pointing Center of Sun (if no activity) Partial Frame Images 8 blocks Line Selection 171 A, 195 A, 304 A Timing Wavelength Exposure time 304 45 seconds 65 seconds 175 5 seconds 25 seconds 195 10 seconds 30 seconds Total image time (cadence) 2 minutes