Using Polar Faculae to Determine the Sun’s High-latitude Rotation Rate. I. Techniques and Initial Measurements
Year: 2024
Type: article
Abstract: This paper describes a new way of determining the high-latitude solar rotation rate statistically from simultaneous observations of many polar faculae. In this experiment, I extracted frames from a movie made previously from flat-fielded images obtained in the 6767 Å continuum during 1997–1998 February and used those frames to construct spacetime maps from high-latitude slices of the favorably oriented south polar cap. These maps show an array of slanted tracks whose average slope indicates the east–west speed of faculae at that latitude, λ s . When the slopes are measured and plotted as a function of latitude, they show relatively little scatter ∼ 0.01–02 km s−1 from a straight line whose zero-speed extension passes through the Sun’s south pole. This means that the speed, v(λ s ), and the latitudinal radius, R ⊙ cos λ s , approach 0 at the same rate, so that their ratio gives a nearly constant synodic rotation rate ∼8.°6 day−1 surrounding the Sun’s south pole. A few measurements of the unfavorably oriented north polar cap are consistent with these measurements near the south pole.
Source: The Astrophysical Journal
Author: Neil R. Sheeley
Institution: University of Arizona
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
OpenAlex ID: W4404341635