Using Polar Faculae to Determine the Sun's High-Latitude Rotation Rate. I. Techniques and Initial Measurements ...

• Main Author: Sheeley, Neil R.
• Format: Text
• Language: unknown
• Published: arXiv 2024
• Subjects: Solar and Stellar Astrophysics astro-ph.SR; FOS: Physical sciences; South Pole; South pole
• Online Access: https://dx.doi.org/10.48550/arxiv.2411.02245; https://arxiv.org/abs/2411.02245

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 A continuum during February 1997-1998 and used those frames to construct space-time 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, Ls. When the slopes are measured and plotted as a function of latitude, they show relatively little scatter 0.01-02 km/s from a straight line whose zero-speed extension passes through the Sun's south pole. This means that the speed, v(Ls), and the latitudinal radius, R cos(Ls), approach 0 at the same rate, so that their ratio gives a nearly constant synodic rotation rate 8.6 deg/day surrounding the Sun's south pole. A few measurements of the unfavorably oriented north ... : 13 pages, 8 figures ...