High Resolution Observations of the Photosphere

Abstract

High resolution observations, theoretical models, and simulations are discovering many new and exciting phenomena in the solar atmosphere. In recent years, there have been a number of very high quality observations of the solar surface and lower photosphere made on the ground at Sacramento Peak Observatory, Pic du Midi, and at the Swedish Solar Observatory, La Palma. In space the Solar Optical Universal Polarimeter (SOUP) has made diffraction limited (30 cm aperture) time sequences completely free from atmospheric disturbances. The recognition that significant progress is possible in non-linear dynamics has encouraged a number of theoretical groups to attack the problem of convection in the solar atmosphere. Two, two and a half, and three dimensional simulations yield the geometry of the flow below the surface and a prediction of the response of the atmosphere above the surface. Models of magnetic flux tubes are now very sophisticated, and modern high resolution observations should be able to test these theories. The development of the technique of Local Correlation Tracking (LCT) has allowed the direct measurement of horizontal velocities in the atmosphere near disk center. The combination of Doppler and LCT measurements allows a direct measurement of the photospheric vector flow field. Measurements from SOUP, Sacramento Peak, Pic du Midi, and La Palma have shown that mesoscale flows cover the surface and that there exist still larger scale flows associated with emerging pores and active regions. Much of the recent experimental and theoretical progress in processing and understanding high resolution data has resulted from the availability of powerful scientific workstations for user interaction, large amounts of memory for image storage, and supercomputers for the massive fluid dynamics calculations. We are now in the very early stages of learning how to use these new computer tools to identify and follow processes in the solar atmosphere.