Standing Slow-Mode Waves in Hot Coronal Loops: Observations, Modeling, and Coronal Seismology

TL;DR

This paper reviews observations and models of strongly damped slow-mode waves in hot coronal loops, highlighting their excitation, damping mechanisms, and applications in coronal seismology.

Contribution

It provides a comprehensive synthesis of observational data and theoretical models, advancing understanding of slow-mode wave dynamics and their seismological applications.

Findings

Damped slow-mode waves are frequently observed in hot coronal loops.

Thermal conduction and viscosity are primary damping mechanisms.

Mode coupling contributes to rapid wave excitation.

Abstract

Strongly damped Doppler shift oscillations are observed frequently associated with flarelike events in hot coronal loops. In this paper, a review of the observed properties and the theoretical modeling is presented. Statistical measurements of physical parameters (period, decay time, and amplitude) have been obtained based on a large number of events observed by SOHO/SUMER and Yohkoh/BCS. Several pieces of evidence are found to support their interpretation in terms of the fundamental standing longitudinal slow mode. The high excitation rate of these oscillations in small- or micro-flares suggest that the slow mode waves are a natural response of the coronal plasma to impulsive heating in closed magnetic structure. The strong damping and the rapid excitation of the observed waves are two major aspects of the waves that are poorly understood, and are the main subject of theoretical modeling. The slow waves are found mainly damped by thermal conduction and viscosity in hot coronal loops. The mode coupling seems to play an important role in rapid excitation of the standing slow mode. Several seismology applications such as determination of the magnetic field, temperature, and density in coronal loops are demonstrated. Further, some open issues are discussed.