Analysis of SOHO/MDI and TRACE Observations of Sunspot Torsional Oscillation in AR10421

TL;DR

This study analyzes sunspot torsional oscillations in AR10421 using SOHO/MDI and TRACE data, revealing synchronized torsional rotations with a period of about 3.8 days in magnetic and velocity fields.

Contribution

It provides a detailed analysis of sunspot torsional oscillations using combined magnetogram, Dopplergram, and white-light observations, highlighting the coherence of magnetic and velocity torsional motions.

Findings

Sunspot magnetic and velocity fields show torsional oscillations with a 3.8-day period.

Both umbra and penumbra exhibit synchronized torsional rotation.

TRACE data confirms torsional rotation in white-light images.

Abstract

Rotation of the leading sunspot of active region NOAA 10421 was investigated using magnetograms and Dopplergrams from the MDI instrument of the Solar and Heliospheric Observatory (SOHO), and white-light images from the Transition Region and Coronal Explorer (TRACE). The vertical, radial, and azimuthal axisymmetrical components of both magnetic and velocity field vectors were reconstructed for the sunspot umbra and penumbra. All three components of both vectors in the umbra and penumbra show torsional oscillations with the same rotational period of about 3.8 days. The TRACE white-light data also show that the sunspot umbra and penumbra are torsionally rotating with the same period. Possible mechanisms of sunspot torsional motions are discussed.