A Scenario for Origin of Global 4 mHz Oscillations in Solar Corona

TL;DR

This paper presents a spherically symmetric hydrodynamic model of the solar atmosphere that explains the origin of 4 mHz oscillations in the corona as a result of p-modes amplified in a resonant cavity, aligning with observations.

Contribution

It introduces a novel model linking p-mode oscillations to coronal 4 mHz oscillations, explaining their ubiquity without requiring p-mode transmission through the chromosphere.

Findings

Oscillations with a peak frequency of ~4 mHz were found in simulations.

The 4 mHz oscillations originate from p-modes amplified in a resonant cavity.

Mass upflows may supply plasma to the corona and prominences.

Abstract

We establish a spherically symmetric model of solar atmosphere, which consists of the whole chromosphere and low corona below the $1.25$ solar radius. It is a hydrodynamic model with heating in the chromosphere through an artificial energy flux. We performed a series of simulations with our model and found oscillations with a peak frequency of $\sim$4 $\rm{mHz}$ in the power spectrum. We confirmed that this resulted from the $p$-mode excited in the transition region and amplified in a resonant cavity situated in the height range $\sim$$4\times10^3$--$2\times10^4$ km. This result is consistent with global observations of Alfv\'enic waves in corona and can naturally explain the observational ubiquity of $4\ \rm{mHz}$ without the difficulty of the $p$-mode passing through the acoustic-damping chromosphere. We also confirmed that acoustic shock waves alone cannot heat the corona to the observed temperature, and found mass upflows in the height range $\sim$$7\times10^3$--$7\times10^4$ km in our model, which pumped the dense and cool plasma into the corona and might be the mass supplier for solar prominences.