Colloquium
Stochastic excitation of the solar acoustic oscillations – inverting the near field
Abstract
Oscillations of solar-like stars are thought to be stochastically excited, and following Lighthill, the primary excitation mechanism is often assumed to be quadrupolar turbulent Reynolds stresses, though other models for excitation have been proposed. Recently, techniques have been developed to measure the near field wavefronts emitted by individual solar acoustic sources. These techniques have been successfully applied to radiative magnetohydrodynamic simulations of the upper solar convection zone and lower solar atmosphere, and direct waveform fitting has been used to invert for the source properties. Efforts to extend these measurements to high spatial resolution, high temporal cadence solar observations are underway. In this talk we will summarize what the global p-mode spectrum suggests about the stochastic excitation of the solar acoustic oscillations, describe what we have learned about the excitation of acoustic waves recently from the numerical simulations, and outline an observational path to similar success with the real Sun.
About the talk
LASP, University of Colorado
iCalendar Google Calendar
About the speaker
Rast received a BA degree in philosophy with honors from the University of California, Davis in 1979. He subsequently worked for the Federal Aviation Administration as an air traffic control specialist before pursuing and receiving a BA degree in physics with highest honors from the University of California, Santa Cruz in 1987. Rast then entered the graduate program at the University of Colorado, Boulder in the Department of Astrophysical, Planetary and Atmospheric Sciences. During the six month period of January – June 1990 he participated in the Institute for Theoretical Physics Program on “Helioseismology – Probing the Interior of a Star” at the University of California, Santa Barbara. Graduate work was completed in 1992 with the successful defense of a PhD thesis entitled “Compressible Convection with Ionization.” Rast then moved to the University of Leeds, England as a research fellow in biophysical fluid dynamics, and from there to a two year postdoctoral position in the Advance Study Program at the National Center for Atmospheric Research. After two years as a research associate at the Joint Institute for Laboratory Astrophysics, Rast joined the scientific staff of the High Altitude Observatory at the National Center for Atmospheric Research. In 2006 he joined the faculty of University of Colorado, Boulder. His research interests include theory, modeling, and observation of stellar convective dynamics and scale selection, turbulent transport, the excitation of solar and stellar oscillations, spectropolarimetric inversions, the origin of solar/stellar irradiance variations, and recently epidemiological modeling. He served as the instrument scientist for the Precision Solar Photometric Telescope (PSPT) at Mauna Loa Solar Observatory (MLSO) over its period of operation from 1999 to 2015, and chair of the Daniel K. Inouye Solar Telescope (DKIST) Science Working Group from 2013 to 2021.