3D Coronal Slow Modes: Towards 3D Seismology

TL;DR

This study uses stereoscopic observations from STEREO spacecraft to measure the true 3D speed of slow magnetoacoustic waves in the solar corona, providing new insights into coronal wave dynamics and temperature estimation.

Contribution

It introduces a novel 3D analysis technique to measure the true slow mode speed in the solar corona using stereoscopic data from STEREO A and B.

Findings

First measurement of the true coronal longitudinal slow mode speed.

Wave propagation inclination of approximately 37 degrees to the local normal.

Inferred coronal temperature of about 0.84 MK.

Abstract

On 2008 January 10, the twin Solar Terrestrial Relations Observatory (STEREO) A and B spacecraft conducted a high time cadence study of the solar corona with the Extreme UltraViolet Imager (EUVI) instruments with the aim of investigating coronal dynamics. Observations of the three-dimensional propagation of waves within active region coronal loops and a measurement of the true coronal slow mode speed are obtained. Intensity oscillations with a period of approximately 12 minutes are observed to propagate outwards from the base of a loop system, consistent with the slow magnetoacoustic mode. A novel analysis technique is applied to measure the wave phase velocity in the observations of the A and B spacecraft. These stereoscopic observations are used to infer the three-dimensional velocity vector of the wave propagation, with an inclination of 37 +- 6 deg to the local normal and a magnitude of 132 +- 9 and 132 +- 11 km s-1, giving the first measurement of the true coronal longitudinal slow mode speed, and an inferred temperature of 0.84 +- 12 MK and 0.84 +- 15 MK.