A solar burst with a spectral component observed only above 100 GHz during an M class flare
Context: Since the installation of submillimeter solar radio telescopes, a new spectral burst component was discovered at frequencies above 100 GHz, creating the THz burst category. In all the reported cases, the events were X-class flares and the THz component was increasing. Aims: We report for th...
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todo:paper_00046361_v492_n1_p215_Cristiani2023-10-03T14:00:24Z A solar burst with a spectral component observed only above 100 GHz during an M class flare Cristiani, G. Giménez De Castro, C.G. Mandrini, C.H. MacHado, M.E. De Benedetto E Silva, I. Kaufmann, P. Rovira, M.G. Sun: flares Sun: radio radiation Arches Magnetic fields Radio telescopes Topology Extreme ultraviolet imaging telescopes Magnetic configuration Magnetic-field intensity Michelson Doppler Imager Relativistic electron Solar and heliospheric observatories Sun: flares Sun: radio radiation X rays Context: Since the installation of submillimeter solar radio telescopes, a new spectral burst component was discovered at frequencies above 100 GHz, creating the THz burst category. In all the reported cases, the events were X-class flares and the THz component was increasing. Aims: We report for the first time an M class flare that shows a different submillimeter radio spectral component from the microwave classical burst. Two successive bursts of 2 min duration and separated by 2 min occurred in active region NOAA 10226, starting around 13:15 UT and having an M 6.8 maximum intensity in soft X-rays.Methods. Submillimeter flux density measured by the Solar Submillimeter Telescope (SST) is used, in addition to microwave total Sun patrol telescope observations. Images with Hα filters, from the Hα Solar Telescope for Argentina (HASTA), and extreme UV observations, from the Extreme-ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SoHO), are used to characterize the flaring region. An extensive analysis of the magnetic topology evolution is derived from the Michelson Doppler Imager (SoHO, MDI) magnetograms and used to constrain the solution space of the possible emission mechanisms. Results: The submillimeter component is only observed at 212 GHz. We have upper limits for the emission at 89.4 and 405 GHz, which are less than the observed flux density at 212 GHz. The analysis of the magnetic topology reveals a very compact and complex system of arches that reconnects at low heights, while from the soft X-ray observations we deduce that the flaring area is dense (n ∼ 1012 cm -3). The reconnected arches are anchored in regions with magnetic field intensity differing by an order of magnitude. Accordingly, we conclude that the microwave emission comes from mildly relativistic electrons spiraling down along the reconnected loops. A very small portion of the accelerated electrons can reach the footpoint with the stronger magnetic field (2000 G) and produce synchrotron emission, which is observed at submillimeter frequencies.Conclusions. The finding of a submillimeter burst component in a medium-size flare indicates that the phenomenon is more universal than shown until now. The multiwavelength analysis reveals that neither positron synchrotron nor free-free emission could produce the submillimeter component, which is explained here by synchrotron of accelerated electrons in a rather complex and compact magnetic configuration. © 2008 ESO. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00046361_v492_n1_p215_Cristiani |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Sun: flares Sun: radio radiation Arches Magnetic fields Radio telescopes Topology Extreme ultraviolet imaging telescopes Magnetic configuration Magnetic-field intensity Michelson Doppler Imager Relativistic electron Solar and heliospheric observatories Sun: flares Sun: radio radiation X rays |
| spellingShingle |
Sun: flares Sun: radio radiation Arches Magnetic fields Radio telescopes Topology Extreme ultraviolet imaging telescopes Magnetic configuration Magnetic-field intensity Michelson Doppler Imager Relativistic electron Solar and heliospheric observatories Sun: flares Sun: radio radiation X rays Cristiani, G. Giménez De Castro, C.G. Mandrini, C.H. MacHado, M.E. De Benedetto E Silva, I. Kaufmann, P. Rovira, M.G. A solar burst with a spectral component observed only above 100 GHz during an M class flare |
| topic_facet |
Sun: flares Sun: radio radiation Arches Magnetic fields Radio telescopes Topology Extreme ultraviolet imaging telescopes Magnetic configuration Magnetic-field intensity Michelson Doppler Imager Relativistic electron Solar and heliospheric observatories Sun: flares Sun: radio radiation X rays |
| description |
Context: Since the installation of submillimeter solar radio telescopes, a new spectral burst component was discovered at frequencies above 100 GHz, creating the THz burst category. In all the reported cases, the events were X-class flares and the THz component was increasing. Aims: We report for the first time an M class flare that shows a different submillimeter radio spectral component from the microwave classical burst. Two successive bursts of 2 min duration and separated by 2 min occurred in active region NOAA 10226, starting around 13:15 UT and having an M 6.8 maximum intensity in soft X-rays.Methods. Submillimeter flux density measured by the Solar Submillimeter Telescope (SST) is used, in addition to microwave total Sun patrol telescope observations. Images with Hα filters, from the Hα Solar Telescope for Argentina (HASTA), and extreme UV observations, from the Extreme-ultraviolet Imaging Telescope (EIT) aboard the Solar and Heliospheric Observatory (SoHO), are used to characterize the flaring region. An extensive analysis of the magnetic topology evolution is derived from the Michelson Doppler Imager (SoHO, MDI) magnetograms and used to constrain the solution space of the possible emission mechanisms. Results: The submillimeter component is only observed at 212 GHz. We have upper limits for the emission at 89.4 and 405 GHz, which are less than the observed flux density at 212 GHz. The analysis of the magnetic topology reveals a very compact and complex system of arches that reconnects at low heights, while from the soft X-ray observations we deduce that the flaring area is dense (n ∼ 1012 cm -3). The reconnected arches are anchored in regions with magnetic field intensity differing by an order of magnitude. Accordingly, we conclude that the microwave emission comes from mildly relativistic electrons spiraling down along the reconnected loops. A very small portion of the accelerated electrons can reach the footpoint with the stronger magnetic field (2000 G) and produce synchrotron emission, which is observed at submillimeter frequencies.Conclusions. The finding of a submillimeter burst component in a medium-size flare indicates that the phenomenon is more universal than shown until now. The multiwavelength analysis reveals that neither positron synchrotron nor free-free emission could produce the submillimeter component, which is explained here by synchrotron of accelerated electrons in a rather complex and compact magnetic configuration. © 2008 ESO. |
| format |
JOUR |
| author |
Cristiani, G. Giménez De Castro, C.G. Mandrini, C.H. MacHado, M.E. De Benedetto E Silva, I. Kaufmann, P. Rovira, M.G. |
| author_facet |
Cristiani, G. Giménez De Castro, C.G. Mandrini, C.H. MacHado, M.E. De Benedetto E Silva, I. Kaufmann, P. Rovira, M.G. |
| author_sort |
Cristiani, G. |
| title |
A solar burst with a spectral component observed only above 100 GHz during an M class flare |
| title_short |
A solar burst with a spectral component observed only above 100 GHz during an M class flare |
| title_full |
A solar burst with a spectral component observed only above 100 GHz during an M class flare |
| title_fullStr |
A solar burst with a spectral component observed only above 100 GHz during an M class flare |
| title_full_unstemmed |
A solar burst with a spectral component observed only above 100 GHz during an M class flare |
| title_sort |
solar burst with a spectral component observed only above 100 ghz during an m class flare |
| url |
http://hdl.handle.net/20.500.12110/paper_00046361_v492_n1_p215_Cristiani |
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