Two Types of Dynamic Cool Coronal Structures Observed with STEREO and HINODE

TL;DR

This study identifies and characterizes two distinct types of dynamic cool coronal structures observed with STEREO and HINODE, revealing their properties, motions, and potential magnetic controls during solar eruptions.

Contribution

The paper reports the discovery and detailed analysis of two types of cool coronal structures, providing new insights into their dynamics and magnetic configurations.

Findings

Type I structures are threadlike, flow downward at 72 km/s, and merge with chromospheric fibrils.

Type II structures are shape-transformable, sometimes rolling, flow downward at 37 km/s, and disappear in the chromosphere.

A plasmoid moves along an arch at 31 km/s, leading to arch formation and disappearance.

Abstract

Solar coronal loops show significant plasma motions during their formation and eruption stages. Dynamic cool coronal structures, on the other hand, are often observed to propagate along coronal loops. In this paper, we report on the discovery of two types of dynamic cool coronal structures, and characterize their fundamental properties. Using the EUV 304 angstrom images from the Extreme UltraViolet Imager (EUVI) telescope on the Solar TErrestrial RElation Observatory (STEREO) and the Ca II filtergrams from the Solar Optical Telescope (SOT) instrument on HINODE, we study the evolution of an EUV arch and the kinematics of cool coronal structures. The EUV 304 angstrom observations show that a missile-like plasmoid moves along an arch-shaped trajectory, with an average velocity of 31 km/s. About three hours later, a plasma arch forms along the trajectory, subsequently the top part of the arch fades away and disappears, meanwhile the plasma belonging to the two legs of the arch flows downward to the arch feet. During the arch formation and disappearance, SOT Ca II images explore dynamic cool coronal structures beneath the arch. By tracking these structures, we classify them into two types. Type I is threadlike in shape and flows downward with a greater average velocity of 72 km/s, finally it combines a loop fibril at chromospheric altitude. Type II is shape-transformable and sometimes rolling as it flows downward with a smaller velocity of 37 km/s, then disappears insularly in the chromosphere. It is suggested that the two types of structures are possibly controlled by different magnetic configurations.