13 research outputs found
Allen Telescope Array Multi-Frequency Observations of the Sun
We present the first observations of the Sun with the Allen Telescope Array
(ATA). We used up to six frequencies, from 1.43 to 6 GHz, and baselines from 6
to 300 m. To our knowledge, these are the first simultaneous multifrequency
full-Sun maps obtained at microwave frequencies without mosaicing. The
observations took place when the Sun was relatively quiet, although at least
one active region was present each time. We present multi-frequency flux
budgets for each sources on the Sun. Outside of active regions, assuming
optically thin bremsstrahlung (free--free) coronal emission on top of an
optically thick ~10 000 K chromosphere, the multi-frequency information can be
condensed into a single, frequency-independent, "coronal bremsstrahlung
contribution function" [EM/sqrt(T)] map. This technique allows the separation
of the physics of emission as well as a measurement of the density structure of
the corona. Deviations from this simple relationship usually indicate the
presence of an additional gyroresonance-emission component, as is typical in
active regions.Comment: 16 pages, 11 figures. Accepted for publication in Solar Physic
The Role of Quasi-Transverse Propagation in Observed Polarization of Flare Loop Microwave Radiation
Measurement of the Height of the Chromospheric Network Emission from Solar Dynamics Observatory Images
POlarization Emission of Millimeter Activity at the Sun (POEMAS): New Circular Polarization Solar Telescopes at Two Millimeter Wavelength Ranges
We present a new system of two circular polarization solar radio telescopes, POEMAS, for observations of the Sun at 45 and 90 GHz. The novel characteristic of these instruments is the capability to measure circular right- and left-hand polarizations at these high frequencies. The two frequencies were chosen so as to bridge the gap at radio frequencies between 20 and 200 GHz of solar flare spectra. The telescopes, installed at CASLEO Observatory (Argentina), observe the full disk of the Sun with a half power beam width of 1.4∘, a time resolution of 10 ms at both frequencies, a sensitivity of 2 - 4 K that corresponds to 4 and 20 solar flux unit (=104 Jy), considering aperture efficiencies of 50±5 % and 75±8 % at 45 and 90 GHz, respectively. The telescope system saw first light in November 2011 and is satisfactorily operating daily since then. A few flares were observed and are presented here. The millimeter spectra of some flares are seen to rise toward higher frequencies, indicating the presence of a new spectral component distinct from the microwave one.Fil: Valio, Adriana. Universidade Presbiteriana Mackenzie. Escola de Engenharia. Centro de Radio Astronomia e Astrofisica; Brasil;Fil: Kaufmann, P.. Universidade Presbiteriana Mackenzie. Escola de Engenharia. Centro de Radio Astronomia e Astrofisica; Brasil; Universidade Estadual de Campinas; Brasil;Fil: Giménez de Castro, Carlos Guillermo. Universidade Presbiteriana Mackenzie. Escola de Engenharia. Centro de Radio Astronomia e Astrofisica; Brasil;Fil: Raulin, J. P.. Universidade Presbiteriana Mackenzie. Escola de Engenharia. Centro de Radio Astronomia e Astrofisica; Brasil;Fil: Fernandes, L. O. T.. Universidade Presbiteriana Mackenzie. Escola de Engenharia. Centro de Radio Astronomia e Astrofisica; Brasil; Universidade Estadual de Campinas; Brasil;Fil: Marun, Adolfo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - San Juan. Complejo Astronómico