Dynamics of Stellar Atmospheres

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***Detailed features in starlight are analyzed to determine 1) the kinds of motions seen in the gases comprising the atmospheres of stars, 2) how rapidly stars spin, 3) the kinds of magnetic fields generated in the stars, and 4) how fast stars move in space. From these measurements, we learn about the physical processes of convection, pulsation, and rotation in stars, how rotation combines with convection to make magnetic fields, how those magnetic fields cause dark spots on the surfaces of stars, and how mass escaping from stars interacts with the magnetic field of the star, acting as a brake, to slow its rotation. My work also involves monitoring dozens of stars over many years to see their changes, especially activity cycles like the 11-year magnetic cycle shown by our sun. Since life on earth depends critically on our sun, it is important to understand the sun as a star and to compare it to other stars.