The Evolution of Coronal Dimmings. I. The Photospheric Footpoint Flux Imbalance
- 1University of Colorado Boulder
- 2National Oceanic and Atmospheric Administration
Abstract
Coronal dimmings mark the footpoint regions of coronal mass ejections (CMEs). Measuring the photospheric magnetic field within dimmings offers a direct view of how the eruption’s footpoints evolve. We track the footpoint magnetic flux imbalance across the lifetime of 48 coronal dimmings observed on disk. In contrast to studies based on difference imaging—which measure a blend of the evacuated footpoint cavity and the projected CME plasma cloud—we detect dimmings directly in Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) 193 Å images as transient coronal holes (CHs) with the COronal DImming Tracker (CoDiT), isolating the footpoint cavity and its Helioseismic and Magnetic Imager (HMI) magnetic properties within an evolving boundary. In simple cases, we observe the footpoint flux imbalance growing as the dimming expands, reaching a peak at maximum area, and gradually relaxing as the dimming fades. However, the observation of this coherent rise-and-relax process depends on eruption number: when separating the sample by the number of associated ≥C-class flares, we observe it in single-eruption dimmings, but find it washed out in multieruption dimmings, where several eruptions overprint the same region. A displaced-region null test confirms that the effect is specific to the erupting footpoints and not a property of one-sided field in general: the single-eruption dimming correlation between area and flux imbalance significantly exceeds the quiet-Sun baseline, whereas active regions (ARs)—despite their far larger static imbalance—do not track area at all. We interpret the coherent growth and decay of the dimming footpoint magnetic flux imbalance as consistent with interchange reconnection contributing to the dimming’s evolution.
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BibTeX
@article{krista2026evolution,
title = {{The Evolution of Coronal Dimmings. I. The Photospheric Footpoint Flux Imbalance}},
author = {Larisza D. Krista},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea209},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea209},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The Evolution of Coronal Dimmings. I. The Photospheric Footpoint Flux Imbalance
AU - Larisza D. Krista
PY - 2026
DA - 2026/10/21
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea209
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea209
AB - Coronal dimmings mark the footpoint regions of coronal mass ejections (CMEs). Measuring the photospheric magnetic field within dimmings offers a direct view of how the eruption’s footpoints evolve. We track the footpoint magnetic flux imbalance across the lifetime of 48 coronal dimmings observed on disk. In contrast to studies based on difference imaging—which measure a blend of the evacuated footpoint cavity and the projected CME plasma cloud—we detect dimmings directly in Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) 193 Å images as transient coronal holes (CHs) with the COronal DImming Tracker (CoDiT), isolating the footpoint cavity and its Helioseismic and Magnetic Imager (HMI) magnetic properties within an evolving boundary. In simple cases, we observe the footpoint flux imbalance growing as the dimming expands, reaching a peak at maximum area, and gradually relaxing as the dimming fades. However, the observation of this coherent rise-and-relax process depends on eruption number: when separating the sample by the number of associated ≥C-class flares, we observe it in single-eruption dimmings, but find it washed out in multieruption dimmings, where several eruptions overprint the same region. A displaced-region null test confirms that the effect is specific to the erupting footpoints and not a property of one-sided field in general: the single-eruption dimming correlation between area and flux imbalance significantly exceeds the quiet-Sun baseline, whereas active regions (ARs)—despite their far larger static imbalance—do not track area at all. We interpret the coherent growth and decay of the dimming footpoint magnetic flux imbalance as consistent with interchange reconnection contributing to the dimming’s evolution.
SN - 0004-637X
SN - 1538-4357
ER -