POlarization Emission of Millimeter Activity at the Sun
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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 A flare, also sometimes called a fusée, fusee, or bengala in some Latin-speaking countries, is a type of pyrotechnic that produces a bright light or intense heat without an explosion. Flares are used for distress signaling, illumination, o ...
. 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 The Solar Submillimeter Telescope (SST) is a solar dedicated instrument with the aim to study the radiation produced by high-energy particles during solar flares. Observing at 212 and 405 GHz with a focal array since 2001, it is a unique inst ...
(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 Alma or ALMA may refer to: Arts and entertainment * ''Alma'' (film), a 2009 Spanish short animated film * ''Alma'' (Oswald de Andrade novel), 1922 * ''Alma'' (Le Clézio novel), 2017 * ''Alma'' (play), a 1996 drama by Joshua Sobol about Alma ...
band 3 may also observe at 90 GHz with circular polarization).


Science

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) ( Nobeyama,
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
) 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), ( Nobeyama,
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
) 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 The El Leoncito Astronomical Complex (Spanish: Complejo Astronómico El Leoncito - CASLEO) is an astronomical observatory in the San Juan Province of Argentina. CASLEO is one of two observatories located within El Leoncito National Park, which ...
in
San Juan Province, Argentina San Juan Province () is a province of Argentina, located in the western part of the country. Neighbouring provinces are, moving clockwise from the north, La Rioja, San Luis and Mendoza. It borders with Chile to the west. The province has an a ...
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 Synchrotron radiation (also known as magnetobremsstrahlung radiation) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (). It is produced artificially in ...
from accelerated electrons emitting at
chromospheric A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the S ...
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.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)
/ref> 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

* Sun *
Chromosphere A chromosphere ("sphere of color") is the second layer of a star's atmosphere, located above the photosphere and below the solar transition region and corona. The term usually refers to the Sun's chromosphere, but not exclusively. In the Su ...
* Corona *
Solar Flares A solar flare is an intense localized eruption of electromagnetic radiation in the Sun's atmosphere. Flares occur in active regions and are often, but not always, accompanied by coronal mass ejections, solar particle events, and other solar phe ...
* Radio astronomy * List of radio telescopes *
Synchrotron radiation Synchrotron radiation (also known as magnetobremsstrahlung radiation) is the electromagnetic radiation emitted when relativistic charged particles are subject to an acceleration perpendicular to their velocity (). It is produced artificially in ...


References


External links


Nobeyama Radio Heliograph Official Site

Nobeyama Radio Polarimeters Official Site

Solar Submillimeter Telescope Official Site
{{Portal bar, Argentina, Astronomy, Stars, Spaceflight, Outer space, Solar System, Education, Science Astronomical instruments Radio telescopes Submillimetre telescopes Astronomical observatories in Argentina