IRIS burst properties in active regions

TL;DR

This study investigates IRIS burst properties across seven active regions over 48 hours, finding their spectral and spatial characteristics remain consistent despite AR evolution, and they predominantly occur in complex, evolving AR cores.

Contribution

It provides the first comprehensive analysis of IRIS burst properties over active region evolution, showing their consistency and spatial association with magnetic features.

Findings

IRIS burst properties are consistent over AR evolution.

IRIS bursts mainly occur in complex, evolving AR cores.

Burst regions tend to increase in size as ARs age.

Abstract

Interface Region Imaging Spectrograph (IRIS) bursts are localised features thought to be driven by magnetic reconnection. Although these events are well-studied, it remains unknown whether their properties vary as their host active regions (ARs) evolve. Here, we aim to understand whether the measurable properties of IRIS bursts are consistent during the evolution of their host ARs. We study 42 dense 400-step rasters sampled by IRIS. These rasters each covered one of seven ARs, with each AR being sampled at least four times over a minimum of 48 hours. An automated detection algorithm is used to identify IRIS burst profiles. Data from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager are also used to provide context about the co-spatial line-of-sight magnetic field. Of the rasters studied, 36 were found to contain IRIS burst profiles. Five ARs (11850, 11909, 11916, 12104, and 12139) contained IRIS burst profiles in each raster that sampled them whilst one AR (11871) was found to contain no such spectra at any time. A total of 4019 IRIS burst profiles belonging to 752 connected objects, which we define as parent IRIS bursts, were identified. IRIS burst profiles were only detected within compact regions in each raster, with these regions appearing to increase in size as the host ARs aged. No systematic changes in the frequency of IRIS burst profiles or the spectral characteristic of IRIS burst profiles through time were found for these ARs. Finally, 93 % of parent IRIS bursts with areas between 1 arcsec^2 and 4 arcsec^2 occurred co-spatial to bi-poles in the photosphere. Overall, IRIS bursts have remarkably consistent spectral and spatial properties throughout the evolution of ARs. These events predominantly form within the cores of larger and more complex ARs, with the regions containing these events appearing to increase in size as the host region itself evolves.