Abstract
Several strong eruptive events that occurred near the solar limb were reported generating off-limb features detectable in the SDO/HMI’s continuum intensity. These observations offer new insights into the emission mechanisms of off-limb flaring loops, magnetic strength in the loops, and electron density distributions, among others. However, only a limited number of such events were reported, and it is unclear whether off-limb white-light features are popular or only associated with specific eruptions. In this study, we surveyed all the flaring events that occurred between May 2010 and August 2023 with a magnitude stronger than M2.0 and a heliographic longitude larger than \(65^{\circ }\). We found that among the 189 flares that met our selection criteria, 78 (41.3%) had off-limb features associated with them. Further statistical analysis showed, unsurprisingly, that the stronger the flare, the more likely it has an off-limb white-light feature, and the closer the flare is to the limb, the more likely an off-limb feature is detectable. We then categorized these off-limb white-light events into four types, closed-loop eruptions, open-loop eruptions, fast ejection, and flare arcades, and identified the events with visible flare ribbons. Coupling two examples of the white-light observations with simultaneous UV/EUV observations, we demonstrate the usefulness of the former in studying the flare dynamics and emission mechanisms. Our catalogue provides a rather complete list of the off-limb white-light events, which will benefit the community interested in studying such events.
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Data Availability
The SDO/HMI \(I_{\mathrm{c}}\) data used in this analysis are available at jsoc.stanford.edu. The flare catalogue from which the candidate events were chosen is located at www.lmsal.com/solarsoft/latest_events_archive.html.
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Acknowledgments
We thank the reviewer for constructive comments that helped to improve the quality of this paper. J. Z. thanks Prof. J. T. Hoeksema for offering her an opportunity of summer internship in the solar physics group at Stanford University. SDO is a NASA mission, and SDO/HMI is a NASA project contracted to Stanford University.
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This work was partly sponsored by NASA contract NAS5-02139 to Stanford University.
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Y.L. conceived the idea of the work and J.Z. carried out most of the data analysis. J.Z. prepared all the figures and both tables. Both authors shared the writing of the manuscript text, and both authors reviewed the manuscript.
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Zhao, J.S., Liu, Y. A Survey and Statistical Study of Off-Limb Events Observed in SDO/HMI Continuum Intensity. Sol Phys 298, 148 (2023). https://doi.org/10.1007/s11207-023-02240-4
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DOI: https://doi.org/10.1007/s11207-023-02240-4