The Rotational Period of the Sun Using the Doppler Shift of the H-alpha Spectral Line (Abstract)

Volume 40 number 2 (2012)

Robert M. Gill

California State University, San Marcos, Physics Department, 333 S.Twin Oaks Valley Rd., San Marcos, CA 92096; rgill@csusm.edu

Abstract

The fact that the sun rotates is obvious by observing the daily motion of sunspots. The overall sunspot movement to the west is a result of this solar rotation. However, solar rotation can also be determined by observing the solar spectrum at the solar limbs. The absorption lines in the spectrum will display a Doppler shift since the east limb is coming toward the observer and the west limb is moving away. The velocity of the limb, relative to the observer, can be determined from these spectral line shifts. Knowing the solar radius, the rotational period can be calculated.