Convectively coupled equatorial trapped waves in stars and planets

TL;DR

This study investigates convectively coupled equatorial trapped waves in stars and planets, analyzing their behavior under various conditions including magnetic fields, stratification, and non-traditional Coriolis effects, with applications to solar phenomena.

Contribution

It introduces a comprehensive model for equatorial waves in stars and planets, incorporating magnetic fields and non-traditional Coriolis effects, and applies it to solar observations.

Findings

Wave frequencies depend on stratification and buoyancy.

Non-traditional Coriolis terms influence wave width and phase.

Magnetic field strength constrains Rieger periodicities in the Sun.

Abstract

In this paper, we have studied the convectively coupled equatorially trapped waves in rotating stars, with and without magnetic field. The equatorial trapped HD and MHD Poincar\'e, Rossby, mixed Rossby-Poincar\'e, and Kelvin waves were identified. The effects of stratification and non-traditional Coriolis force terms have been investigated. When the flow is strongly stratified, the wave frequencies of the convectively coupled model are almost the same as those of shallow water model. However, when the flow is weakly stratified, the wave frequencies are constrained by the buoyancy frequency. The non-traditional Coriolis terms affect the widths and phases of the equatorial waves. The width increases with the increasing non-traditional Coriolis parameter. Phase shift occurs when the non-traditional Coriolis parameter is included. Magnetic effect is significant when the magnetic field is strong. We have applied the model in the solar atmosphere and solar tachocline to explain the Rieger type periodicities. For the solar atmosphere, when magnetic effect is taken into account, we find that the magnetic field should be smaller than $5G$ in the solar photosphere. Otherwise, the Rieger type periodicities can be only attributed to long Rossby waves. For the solar tachocline, we find that magnetic field of the solar tachocline should be smaller than $50kG$ to observe the 160 days Rieger period. In addition, we find that the effect of the non-traditional Coriolis terms is not obvious in the solar photosphere, but its effect on the tachocline is significant.