Alfven Waves in the Lower Solar Atmosphere

TL;DR

This paper reports the detection of torsional Alfven waves in the lower solar atmosphere, showing their potential role in heating the solar corona through observed oscillations and energy flux measurements.

Contribution

It provides the first observational evidence of torsional Alfven waves in a large bright point, with detailed analysis of their properties and implications for coronal heating.

Findings

Detected Alfven waves with 126-700 s periodicities

Oscillations have 2.6 km/s amplitude and 23 km/s blue shift

Energy flux is sufficient for solar corona heating

Abstract

We report the detection of oscillatory phenomena associated with a large bright-point group that is 430,000 square kilometers in area and located near the solar disk center. Wavelet analysis reveals full-width half-maximum oscillations with periodicities ranging from 126 to 700 seconds originating above the bright point and significance levels exceeding 99%. These oscillations, 2.6 kilometers per second in amplitude, are coupled with chromospheric line-of-sight Doppler velocities with an average blue shift of 23 kilometers per second. A lack of cospatial intensity oscillations and transversal displacements rules out the presence of magneto-acoustic wave modes. The oscillations are a signature of Alfven waves produced by a torsional twist of +/-22 degrees. A phase shift of 180 degrees across the diameter of the bright point suggests that these torsional Alfven oscillations are induced globally throughout the entire brightening. The energy flux associated with this wave mode is sufficient to heat the solar corona.