Evolution of microflares associated with bright points in coronal holes and in quiet regions

TL;DR

This study compares microflares at bright points in coronal holes and quiet regions, revealing similarities in their physical evolution and differences in their surrounding phenomena due to magnetic field configurations.

Contribution

It provides a comparative analysis of microflares in different solar regions, highlighting the influence of magnetic topology on their surroundings and evolution.

Findings

Microflares show impulsive hot peaks followed by cooling phases.

Density increases during impulsive peaks, supporting chromospheric evaporation.

Coronal jets are associated with microflares in coronal holes, while dimmings occur in quiet regions.

Abstract

We aim to find similarities and differences between microflares at coronal bright points found in quiet regions and coronal holes, and to study their relationship with large scale flares. Coronal bright points in quiet regions and in coronal holes were observed with Hinode/EIS using the same sequence. Microflares associated with bright points are identified from the X-ray lightcurve. The temporal variation of physical properties was traced in the course of microflares. The lightcurves of microflares indicated an impulsive peak at hot emission followed by an enhancement at cool emission, which is compatible with the cooling model of flare loops. The density was found to increase at the rise of the impulsive peak, supporting chromospheric evaporation models. A notable difference is found in the surroundings of microflares; diffuse coronal jets are produced above microflares in coronal holes while coronal dimmings are formed in quiet regions. The microflares associated with bright points share common characteristics to active region flares. The difference in the surroundings of microflares are caused by open and closed configurations of the pre-existing magnetic field.