Figure 1. ALMA 1.3 mm distinction image of the flare with its shapes overlaid on SDO/HMI magnetogram, GONG Hα and SDO/AIA 304, 171 and 94 Å images. A number of solar features are indicated that are related to the millimeter emission (adjusted from Skokić et al. 2022).
Spatial equivalents of the millimeter flare emission
One flare was observed in ALMA band 6 (λ ≈ 1.3 mm), while the rest were discovered in band 3 (λ ≈ 3 mm). In both ALMA bands 3 and 6, the ALMA flare emission occurs generally above the neutral line observed in HMI magnetograms.
Strength profiles of the millimeter flare emission
One flare does not have a corresponding soft X-ray improvement but does reveal up in the EUV channels. The strength profiles suggest millimeter flares to be mainly steady phase phenomena with occasional spontaneous stage emission.
Intensity profiles of five flares observed by ALMA and compared with 94, 171 and 304 Å SDO/AIA EUV channels and GOES-15 XRSB fluxes. Intensities revealed are averages over the circular area around the flaring region (adapted from Skokić et al. 2022).
Conclusions
A lot of surprising is the fact that different phenomena in both hot and cold plasma cause boosted brightness in millimeter waves. Although there is no proof contradicting the assumption that the emission process is thermal free-free emission, it appears that the previous circumstance of a chromospheric hot spot heated by a precipitating electron beam is too simplified. In addition to footpoints of hot loops, millimeter flare emission was discovered to be related to triggered Hα filaments, impact points of plasma motions, post-flare loops, and hot loop tops. Remarkably, we discovered cases where no feature in Hα, 304 Å, 171 Å, and 94 Å was visible at the position of the millimeter wave emission peak.
Based upon a current paper by I. Skokić, A. O. Benz, R. Brajša, D. Sudar, F. Matković, M. Bárta, 2022, A&A, in press (https://doi.org/10.1051/0004-6361/202244532).
References:.
Krucker, S., Giménez de Castro, C. G., Hudson, H. S., et al. 2013, A&A Rev., 21, 58.
Shimizu, T., Shimojo, M., & & Abe, M. 2021, ApJ, 922, 113
Utilized as an interferometer, the ALMA field of view is small, and ALMA can not observe on demand when a flare takes place because of scheduling restraints. We utilized easily available large scale full disk single-dish observations for very first detections of full-scale ALMA flares. We browsed for flares in archive ALMA single-dish images in times noted in the solar flare brochure (HEK).
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Used as an interferometer, the ALMA field of view is small, and ALMA can not observe on need when a flare takes place since of scheduling constraints. We used easily available large scale full disk single-dish observations for first detections of full-scale ALMA flares. We browsed for flares in archive ALMA single-dish images in times noted in the solar flare brochure (HEK). In both ALMA bands 3 and 6, the ALMA flare emission takes place generally above the neutral line observed in HMI magnetograms. Intensity profiles of five flares observed by ALMA and compared with 94, 171 and 304 Å SDO/AIA EUV channels and GOES-15 XRSB fluxes.