Radial Differential Rotation of Solar Corona using Radio Emissions

TL;DR

This study investigates radial variations in solar coronal rotation by analyzing radio emissions at multiple frequencies over five years, revealing variable rotation periods at different coronal heights.

Contribution

It introduces a method to analyze radial and temporal variations in solar rotation using radio emission data at multiple frequencies with data gap handling.

Findings

Rotation period varies with height in the solar corona.

Radio emission at different frequencies originates from different coronal heights.

The study finds both similarities and contradictions with previous research.

Abstract

The present work is an effort to investigate possible radial variations in the solar coronal rotation by analyzing the solar radio emission data at 15 different frequencies (275-1755 MHz) for the period starting from July 1994 to May 1999. We used a time series of disk-integrated radio flux recorded daily at these frequencies through radio telescopes situated at Astronomical Observatory of the Jagellonian University in Cracow. The different frequency radiation originates from different heights in the solar corona. Existing models, indicate its origin at the height range from nearly $\sim12,000$ km (for emission at 275 MHz), below up to $\sim2,400$ km (for emission at 1755 MHz). There are some data gaps in the time series used for the study, so we used statistical analysis using the Lomb-Scargle Periodogram (LSP). This method has successfully estimated the periodicity present in time series even with such data gaps. The rotation period estimated through LSP shows variation in rotation period, which is compared with the earlier reported estimate using auto correlation technique. The present study indicates some similarity as well as contradiction with studies reported earlier. The radial and temporal variation in solar rotation period are presented and discussed for the whole period analyzed.