Understanding the Physical Nature of Coronal \u201cEIT Waves\u201d

D M Long,P T Gallagher,T Žic,P F Chen,C Downs,D S Bloomfield,A M Veronig,B Vršnak,R.-Y Kwon,A Warmuth,A Vourlidas,K Vanninathan

doi:10.1007/s11207-016-1030-y

Abstract

For almost 20 years the physical nature of globally propagating waves in the solar corona (commonly called “EIT waves”) has been controversial and subject to debate. Additional theories have been proposed over the years to explain observations that did not agree with the originally proposed fast-mode wave interpretation. However, the incompatibility of observations made using the Extreme-ultraviolet Imaging Telescope (EIT) onboard the Solar and Heliospheric Observatory with the fast-mode wave interpretation was challenged by differing viewpoints from the twin Solar Terrestrial Relations Observatory spacecraft and data with higher spatial and temporal resolution from the Solar Dynamics Observatory. In this article, we reexamine the theories proposed to explain EIT waves to identify measurable properties and behaviours that can be compared to current and future observations. Most of us conclude that the so-called EIT waves are best described as fast-mode large-amplitude waves or shocks that are initially driven by the impulsive expansion of an erupting coronal mass ejection in the low corona.

Highlights

Propagating waves in the solar corona have been studied in detail since they were first directly observed by the Extreme-ultraviolet Imaging Telescope (EIT: Delaboudinière et al, 1995) onboard the Solar and Heliospheric Observatory (SOHO: Domingo, Fleck, and Poland, 1995)
We aim to identify and quantify the physical properties and behaviour predicted by the theories that have been proposed to explain the EIT-wave phenomenon, greatly expanding on the initial attempt by Patsourakos et al (2009)
We have identified 15 fundamental EIT-wave properties that may be used to distinguish between the different theories proposed to explain the waves

Summary

Introduction

Propagating waves in the solar corona have been studied in detail since they were first directly observed by the Extreme-ultraviolet Imaging Telescope (EIT: Delaboudinière et al, 1995) onboard the Solar and Heliospheric Observatory (SOHO: Domingo, Fleck, and Poland, 1995). EIT waves are generally observed as bright pulses in the low solar corona emanating from the source of a solar eruption, and often traverse the solar disk in less than an hour. They can have velocities of up to ≈ 1400 km s−1 (cf Nitta et al, 2013), but are most typically observed at velocities of 200 – 500 km s−1 (Klassen et al, 2000; Thompson and Myers, 2009; Muhr et al, 2014). This was consistent with the global MHD fast-mode wave propagating in the corona that was predicted by Uchida (1968) to explain the chromospheric Moreton–Ramsey wave (Moreton, 1960; Moreton and Ramsey, 1960)

Objectives

Findings

Discussion

Conclusion