Energy conversion rate of an active region transient brightening estimated by a spectroscopic observation of Hinode

TL;DR

This study estimates the energy conversion rates during active-region transient brightenings using spectroscopic and imaging data, revealing their limited contribution to active region heating.

Contribution

It provides the first statistical estimation of energy conversion rates from Doppler, thermal, and non-thermal energies in transient brightenings.

Findings

Doppler energy is about 0.1-1% of thermal energy change.

Non-thermal energy is about 10-100% of thermal energy change.

Transient brightenings contribute at most 2% to active region heating.

Abstract

We statistically estimate the conversion rate of the energy released during an active-region transient brightening to Doppler motion and thermal and non-thermal energies. We used two types of datasets for the energy estimation and detection of transient brightenings. One includes spectroscopic images of Fe xiv, Fe xv, and Fe xvi lines observed by the Hinode/EUV Imaging Spectrometer. The other includes images obtained from the 211 \AA channel of the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA). The observed active region was NOAA 11890 on November 09, 2013, and the day after that. As a result, the released Doppler motion and non-thermal energies were found to be approximately 0.1 \-- 1% and 10 \-- 100% of the change in the amount of thermal energy in each enhancement, respectively. Using this conversion rate, we estimated the contribution of the total energy flux of AIA transient brightenings to the active region heating to be at most 2% of the conduction and radiative losses.