Clique du Soleil

[ Clique Publications ]

Solar Physics

The Solar Physics group at Monash University is predominantly concerned with the local helioseismology of magnetic activity. It leads the field in sunquake research, having discovered 15 of the 16 known quakes. A major theme is the development of a detailed theoretical understanding of how surface magnetism blurs our helioseismic view of the solar interior -- the ``showerglass effect''. The group uses data from a wide range of space and ground-based observatories, and is expert in various numerical data analysis techniques and in numerical simulations. Modelling of particle emission from flares and tachocline instabilities are amongst other current interests.

• Discovery of a wide range of 2D and 3D magneto-rotational instabilities in the solar tachocline -- the shear layer at the base of the Sun's convection zone;
• Development of a new technique using Helioseismic Holography to find and explore sunquakes; all but one of the known quakes were discovered at Monash using this technique;
• Discovery that magnetic field inclination is the long-sought "missing ingredient" in understanding the absorption of helioseismic waves by sunspots;
• Development of a new Generalized Ray Theory for MHD waves in solar active regions which allows quantitative calculation of mode conversion between magnetic and acoustic waves in helioseismology, allowing us to understand the seismology of magnetic activity.

CSPA Sunquake Database

	A helioseismic acoustic ray coming up underneath a sunspot in inclined magnetic field splits into acoustic and magnetic parts at the level (horizontal line) where the sound and Alfven speeds are equal. (Image credit: Paul Cally)
	This composite image combines EIT images from three wavelengths (171Å, 195Å and 284Å) into one that reveals solar features unique to each wavelength. Since the EIT images come to us from the spacecraft in black and white, they are color coded for easy identification. For this image, the nearly simultaneous images from May 1998 were each given a color code (red, yellow and blue) and merged into one. (Image credit: SOHO)
	A fast MHD wave packet (green-yellow) moves to the right in a cold magneto-atmosphere where Alfven speed is increasing exponentially with x. It reflects from this gradient, but also partially converts to and Alfven wave (red-blue) trapped on the magnetic field lines (oriented in the z-direction). These Alfven waves phase mix, producing arbitrarily fine spatial scales that inevitably will lead to dissipation. At most, 50% of the wave energy is converted to Alfven waves. (Image credit: Paul Cally) See the full animation here. (Animated GIF, File size 14.8MB; Credit: Paul Cally).