Observations of Transient Active Region Heating with Hinode

TL;DR

This paper reports on high-resolution observations of transient heating events in an active solar region using Hinode's instruments, revealing loop heating and cooling dynamics, and analyzing a significant flare's spectral signatures.

Contribution

It provides detailed observational analysis of transient active region heating events, including a specific flare, using Hinode's EIS and XRT instruments, advancing understanding of coronal heating processes.

Findings

Transient heating events are common in active regions.

The evolution of these events is consistent with loop heating and cooling.

Spectral signatures of a small flare include Doppler shifts and increased line widths.

Abstract

We present observations of transient active region heating events observed with the Extreme Ultraviolet Imaging Spectrometer (EIS) and X-ray Telescope (XRT) on Hinode. This initial investigation focuses on NOAA active region 10940 as observed by Hinode on February 1, 2007 between 12 and 19 UT. In these observations we find numerous examples of transient heating events within the active region. The high spatial resolution and broad temperature coverage of these instruments allows us to track the evolution of coronal plasma. The evolution of the emission observed with XRT and EIS during these events is generally consistent with loops that have been heated and are cooling. We have analyzed the most energetic heating event observed during this period, a small GOES B-class flare, in some detail and present some of the spectral signatures of the event, such as relative Doppler shifts at one of the loop footpoints and enhanced line widths during the rise phase of the event. While the analysis of these transient events has the potential to yield insights into the coronal heating mechanism, these observations do not rule out the possibility that there is a strong steady heating level in the active region. Detailed statistical analysis will be required to address this question definitively.