Junwei Zhao
W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94035-4085

Limb flares observed in the solar limb are extremely rare, but SDO/HMI’s continuous observations of the Sun are changing that. A few limb flares have been observed in the HMI’s FeI 6173Å, resulting in few interesting publications that studied different aspects of the white-light flares. For example, Martínez Oliveros et al.^[1] compared the WL brightening sources with those observed in extreme ultraviolet (EUV) and soft X-ray, Saint-Hilaire et al.^[2] analyzed the linear polarization observed in the WL flare loops, Heinzel et al.^[3] studied emission mechanisms of the WL off the solar limb, and Zhao et al.^[4] reported the quasi-periodic brightening in the off-limb post-flare arcade.

Figure 1| (A) White flare right on the Sun’s east limb; (B) Materials were observed ejected from the Sun; (C) Materials falling back and hanging there for a few minutes; (D) Post-flare arcade formed near the limb.

On 2022 May 3, SDO/HMI captured another limb flare, which was also associated with a filament eruption. The X1.1-class flare, SOL2022-05-03, started on 13:09UT. From the near-limb and off-limb movies below, one can see that the off-limb brightening occurred a few minutes after the onset of the flare right on the limb. Materials are clearly seen ejected from the Sun, but a large fraction of the ejected mass fell back. The falling back materials seemed to reach a balance high above the photosphere, and remained in that position until became invisible in the HMI’s continuum images. Interestingly, a post-flare arcade, although weak in intensity and low in altitude, appeared off the limb above the flaring location.

This event is a case of failed, or partially failed, filament eruption that was captured in white light. We look forward to seeing interesting science that will be done from this event.

References

[1] Martínez Oliveros J.-C., Krucker S., Hudson H. S. et al. 2014, ApJL, 780, L28
[2] Saint-Hilaire P., Schou J., Martínez Oliveros J.-C. et al. 2014, ApJL, 786, L19
[3] Heinzel P., Kleint L., Kašparová J. & Krucker S. 2017, ApJ, 847, 48
[4] Zhao, J., Liu, W., & Vial, J.-C., 2021 ApJL, 921, L26