POlarization Emission of Millimeter Activity at the Sun
November 18, 2023
The POlarization Emission of Millimeter Activity at the Sun (POEMAS) is a solar patrol system composed of two radio telescopes with superheterodynecircular polarization receivers at 45 and 90 GHz. Since their half power beam width is around 1.4°, they observe the full sun. The acquisition system allows to gather 100 values per second at both frequencies and polarizations, with a sensitivity of around 20 solar flux units (SFU) (1 SFU ≡ 104Jy). The telescope saw first light in November 2011, and showed excellent performance during two years, when it observed many flares.[1] Since November 2013 is stopped for repairing. The main interest of POEMAS is the observation of solar flares in a frequency range where there are very few detectors and fill the gap between microwaves observed with the Radio Solar Telescope Network (1 to 15.4 GHz) and submillimeter observations of the Solar Submillimeter Telescope (212 and 405 GHz). Moreover, POEMAS is the only current telescope capable of carrying on circular polarization solar flare observations at 90 GHz. (Although, in principle, ALMA band 3 may also observe at 90 GHz with circular polarization[2]).
Polarization Emission of Millimeter Activity at the Sun
POEMAS was designed to fill the gap between microwaves and submillimeter (less than 1 mm) wavelength observations of the solar activity. There are a number of different instruments around the world that monitors the sun at microwaves. The Nobeyama Radio Heliograph (NoRH)[3][4] (Nobeyama, Japan) makes daily maps at 17 GHz (1.7 cm) with circular left and right polarizations and 34 GHz (8.8 mm), total intensity. The Nobeyama Radio Polarimeters (NoRP),[5] (Nobeyama, Japan) is a set of patrol telescopes with receivers from 1 GHz (λ≈30 cm) to 80 GHz (λ≈3.7 mm) at selected frequencies and circular polarization detection (except at 80 GHz) with full sun disk spatial resolution. The Radio Solar Telescope Network (RSTN) is worldwide network of telescopes with receivers at selected bands from few hundred MHz (λ≈75 cm) to 15.4 GHz (λ≈2 cm). At the other end of the band, the Solar Submillimeter Telescope (SST) installed at Complejo Astronomico El Leoncito in San Juan Province, Argentina observes the sun at 212 GHz (λ≈1.4 mm) and 405 GHz (λ≈0.7 mm). Since there is no observational time overlap between Japan and Argentina, the NoRH and NoRP cannot be used together with SST, and only data from some RSTN observatories have times in common with the SST.
The relevance of observing at 45 and 90 GHz comes from the necessity to determine the upturn frequency in the so-called THz events: if the main radiation mechanism is synchrotron radiation from accelerated electrons emitting at chromospheric or coronal heights, it is expected a spectrum with a long and descending logarithmic tail towards millimeter wavelengths. In some cases this classical (textbook) shape is broken and an upturn or spectral reversion is observed.[6][7][8][9] Since the reversion or upturn frequency has been estimated around 50 to 100 GHz for the observed cases, the importance of POEMAS is justified.
^Válio, A., Kaufmann, P., Giménez de Castro, C.G., Raulin, J.-P., Fernández, L.O.T., Marún, A., POlarization Emission of Millimeter Activity at the Sun (POEMAS): New Circular Polarization Solar Telescopes at Two Millimeter Wavelength Ranges, Solar Phys., 283(2), 651, DOI:10.1007/s11207-013-0237-4
^Nakajima, H., et al., Proc. IEEE, 82(5),705, 1994
^Takano, T., et al., An Upgrade of Nobeyama Radioheliograph to a Dual-Frequency (17 and 34 GHz) System, in Coronal Physics from Radio and Space Observations; Proceedings of the CESRA Workshop held in Nouan le Fuzelier, France 3–7 June 1996, edited by Gerard Trottet, Published by Springer, p.183,(1997)
^Kaufmann, P., et al., A New Solar Burst Spectral Component Emitting Only in the Terahertz Range, Astrophys. Jour, 603, L121 (2004)
^Lüthi, T., Lüdi, A., Magun, A., Astron. & Astrophys., 420, 361 (2004)
^Silva, A.V.R., et al., Evidence that Synchrotron Emission from Nonthermal Electrons Produces the Increasing Submillimeter Spectral Component in Solar Flares, Sol. Phys, 241(2),311 (2007)
^Kaufmann, P. et al. Sub-terahertz, Microwaves and High Energy Emissions During the 6 December 2006 Flare, at 18:40 UT, Sol. Phys., 255(1),131 (2009)
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This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources POlarization Emission of Millimeter Activity at the Sun news newspapers books scholar JSTOR August 2014 Learn how and when to remove this template message The POlarization Emission of Millimeter Activity at the Sun POEMAS is a solar patrol system composed of two radio telescopes with superheterodyne circular polarization receivers at 45 and 90 GHz Since their half power beam width is around 1 4 they observe the full sun The acquisition system allows to gather 100 values per second at both frequencies and polarizations with a sensitivity of around 20 solar flux units SFU 1 SFU 104 Jy The telescope saw first light in November 2011 and showed excellent performance during two years when it observed many flares 1 Since November 2013 is stopped for repairing The main interest of POEMAS is the observation of solar flares in a frequency range where there are very few detectors and fill the gap between microwaves observed with the Radio Solar Telescope Network 1 to 15 4 GHz and submillimeter observations of the Solar Submillimeter Telescope 212 and 405 GHz Moreover POEMAS is the only current telescope capable of carrying on circular polarization solar flare observations at 90 GHz Although in principle ALMA band 3 may also observe at 90 GHz with circular polarization 2 Polarization Emission of Millimeter Activity at the SunPOEMAS system installed at CASLEOAlternative namesPOEMASPart ofLeoncito Astronomical Complex Location s San Juan Province ArgentinaCoordinates31 47 56 S 69 17 48 W 31 79897 S 69 29669 W 31 79897 69 29669Altitude2 491 m 8 173 ft Wavelength45 90 GHz 6 7 3 3 mm First lightNovember 2011 Telescope styleradio telescopesolar telescope Location of POlarization Emission of Millimeter Activity at the Sun Related media on Commons edit on Wikidata Contents 1 Science 2 See also 3 References 4 External linksScience editPOEMAS was designed to fill the gap between microwaves and submillimeter less than 1 mm wavelength observations of the solar activity There are a number of different instruments around the world that monitors the sun at microwaves The Nobeyama Radio Heliograph NoRH 3 4 Nobeyama Japan makes daily maps at 17 GHz 1 7 cm with circular left and right polarizations and 34 GHz 8 8 mm total intensity The Nobeyama Radio Polarimeters NoRP 5 Nobeyama Japan is a set of patrol telescopes with receivers from 1 GHz l 30 cm to 80 GHz l 3 7 mm at selected frequencies and circular polarization detection except at 80 GHz with full sun disk spatial resolution The Radio Solar Telescope Network RSTN is worldwide network of telescopes with receivers at selected bands from few hundred MHz l 75 cm to 15 4 GHz l 2 cm At the other end of the band the Solar Submillimeter Telescope SST installed at Complejo Astronomico El Leoncito in San Juan Province Argentina observes the sun at 212 GHz l 1 4 mm and 405 GHz l 0 7 mm Since there is no observational time overlap between Japan and Argentina the NoRH and NoRP cannot be used together with SST and only data from some RSTN observatories have times in common with the SST The relevance of observing at 45 and 90 GHz comes from the necessity to determine the upturn frequency in the so called THz events if the main radiation mechanism is synchrotron radiation from accelerated electrons emitting at chromospheric or coronal heights it is expected a spectrum with a long and descending logarithmic tail towards millimeter wavelengths In some cases this classical textbook shape is broken and an upturn or spectral reversion is observed 6 7 8 9 Since the reversion or upturn frequency has been estimated around 50 to 100 GHz for the observed cases the importance of POEMAS is justified See also editSun Chromosphere Corona Solar Flares Radio astronomy List of radio telescopes Synchrotron radiationReferences edit Valio A Kaufmann P Gimenez de Castro C G Raulin J P Fernandez L O T Marun A POlarization Emission of Millimeter Activity at the Sun POEMAS New Circular Polarization Solar Telescopes at Two Millimeter Wavelength Ranges Solar Phys 283 2 651 DOI 10 1007 s11207 013 0237 4 ALMA Front End Nakajima H et al Proc IEEE 82 5 705 1994 Takano T et al An Upgrade of Nobeyama Radioheliograph to a Dual Frequency 17 and 34 GHz System in Coronal Physics from Radio and Space Observations Proceedings of the CESRA Workshop held in Nouan le Fuzelier France 3 7 June 1996 edited by Gerard Trottet Published by Springer p 183 1997 NoRP Official Site Kaufmann P et al A New Solar Burst Spectral Component Emitting Only in the Terahertz Range Astrophys Jour 603 L121 2004 Luthi T Ludi A Magun A Astron amp Astrophys 420 361 2004 Silva A V R et al Evidence that Synchrotron Emission from Nonthermal Electrons Produces the Increasing Submillimeter Spectral Component in Solar Flares Sol Phys 241 2 311 2007 Kaufmann P et al Sub terahertz Microwaves and High Energy Emissions During the 6 December 2006 Flare at 18 40 UT Sol Phys 255 1 131 2009 External links editNobeyama Radio Heliograph Official Site Nobeyama Radio Polarimeters Official Site Solar Submillimeter Telescope Official SitePortals nbsp Argentina nbsp Astronomy nbsp Stars nbsp Spaceflight nbsp Outer space nbsp Solar System nbsp Education nbsp Science Retrieved from https en wikipedia org w index php title POlarization Emission of Millimeter Activity at the Sun amp oldid 1119300730, wikipedia, wiki, book, books, library,
