HAO 2011 Profiles In Science: Dr. Michael Thompson

Contact

303-497-1500
mjt@ucar.edu

Specialties:

Helioseismology and asteroseismology; Solar physics (external link to current solar images); Inverse problems; Stellar structure and evolution; Astrophysical fluid dynamics.

Michael Thompson is the Director of the High Altitude Observatory of the National Center for Atmospheric Research. He is responsible for the overall scientific and strategic mission, productivity, and excellence of the Observatory in the areas of Solar and Heliospheric physics, and the effects of solar variability on the Earth's magnetosphere, ionosphere, and upper atmosphere. Dr. Thompson's main scientific interests are in the structure and dynamics of the interior of the Sun and other stars, and in helio- and asteroseismology.

Summary of Achievements:

Dr. Michael Thompson's research continues in the areas of helioseismology and asteroseismology. In helioseismology, his recent focus has been on inferences from global-mode frequencies regarding the Sun's radial stratification and on inferences from the temporal variability of the global-mode frequency splittings regarding the evolving zonal flows within the solar interior. The year saw the culmination of a long-standing project with affiliate scientist J. Christensen-Dalsgaard, M. Monteiro, and M. Rempel to characterize the overshoot at the base of the solar convective envelope using helioseismic data: the data favor models with a rather smooth transition in stratification from the lower convection zone to the radiative interior. Regarding the zonal flows in the solar interior, Thompson was co-author with R. Howe and others of three conference proceedings during the year on the first rotation inversion from HMI data, on rotation-rate variations near the solar tachocline, and on the torsional oscillations with particular focus on the recent extended solar minimum. Thompson was also involved during the year on several papers featuring research on solar-like stars using data from the Kepler satellite, and with J. Christensen-Dalsgaard he published a review on recent results from space-based asteroseismic observations entitled "Stellar hydrodynamics caught in the act: asteroseismology with CoRoT and Kepler" for the proceedings of IAU Symposium 271.

Publications

(1) J. Christensen-Dalsgaard, M.J.P.F.G. Monteiro, M. Rempel & M.J. Thompson. 2011: A more realistic representation of overshoot at the base of the solar convective envelope as seen by helioseismology, Monthly Notices of the Royal Astronomical Society, 414, pp. 1158–1174. See online article.

Abstract: The stratification near the base of the Sun's convective envelope is governed by processes of convective overshooting and element diffusion, and the region is widely believed to play a key role in the solar dynamo. The stratification in that region gives rise to a characteristic signal in the frequencies of solar p modes, which has been used to determine the depth of the solar convection zone and to investigate the extent of convective overshoot. Previous helioseismic investigations have shown that the Sun's spherically symmetric stratification in this region is smoother than that in a standard solar model without overshooting, and have ruled out simple models incorporating overshooting, which extend the region of adiabatic stratification and have a more-or-less abrupt transition to subadiabatic stratification at the edge of the overshoot region. In this paper we consider physically motivated models which have a smooth transition in stratification bridging the region from the lower convection zone to the radiative interior beneath. We find that such a model is in better agreement with the helioseismic data than a standard solar model.