Microarsecond Solar Limb Astrometry from Space

Thursday, 18 December 2014
Jeff R. Kuhn1, Ian Cunnyngham1, Rock I Bush2, Marcelo Emilio3 and Isabelle F. Scholl1, (1)University of Hawaii at Manoa, Institute for Astronomy, Honolulu, HI, United States, (2)Stanford University, Stanford, CA, United States, (3)University, Ponta Grossa, Brazil
The solar limb astrometry program for HMI has accumulated several years of precise limb brightness and shape measurements. From above the Earth's atmosphere, with the stable SDO/HMI instrument platform, individual limb measurements are accurate to the 10's of milliarcsecond level. The combined timeseries of solar limb shape is sensitive to solar shape perturbations at the submicroarcsecond level. Oscillatory phenomena (like solar g- and r-modes) may be detected at low frequencies with effective velocity amplitudes of 10's of microns per second. We describe here the low frequency shape and limb brightness oscillations observed by HMI from 1 - 3000 microHz.