Center for Radio Astronomy and Astrophysics at Mackenzie

CRAAM

Projects in Progress

POEMAS Radio polarimeters - FAPESP Project (2009 / 50637-0)

(POlarization Emission of Millimeter Activity at the Sun) at 45 and 90 GHz

The POEMAS system consists of two telescopes, which monitors the Sun daily, operating in two bands of millimeter wavelengths, 45 and 90 GHz, with circular polarization measurements. POEMAS detected the solar emission that is automatically calibrated for brightness temperature and stored. Their routine also includes  measuring the opacity of the Earth's atmosphere at certain times during daily observations.

Researcher in charge: Adriana Valio (avalio@craam.mackenzie.br)

The POEMAS database consists of observations from November 2011 through December 2013. These data are available and can be requested via the email above.

Justification

The spectrum of solar flares contains important information about the physics involved in the process. Currently, however, there is a large data gap in frequency from 20 to 200 GHz. Unfortunately this frequency gap prevents the determination of several parameters of solar flares such as:

(i) the frequency of the spectral peak, from which the intensity of the magnetic field of the emitting source and the density of emitting electrons can be deduced;

(ii) the spectral index of the optically thin source, directly related to the energy spectrum of the accelerated electrons, which spectrum depends on the acceleration mechanism acting during flares; and

(iii) other physical parameters such as source size, presence of inhomogeneities that can also be inferred from a spectrum with complete spectral resolution.

Recently, a new high-frequency spectral component above 200 GHz with increasing frequency flux has been discovered. This component is distinct from the traditional microwave component, which peaks around 10 GHz. To figure out the nature of the two components (microwave and submillimeter) and determine the physical parameters that characterize solar flares, it is essential to observe the intermediate frequencies of 45 and 90 GHz.

Location

The Telescopes were installed in the Complexo Astronômico El Leoncito Observatory (CASLEO), in Argentina at 2550 m of altitude, a place ideal for solar observation at these high radio frequencies. At the same site is located since 1999, the Solar Submillimeter Telescope (SST), which monitors the Sun daily at 212 and 405 GHz.

Especifications

The instrument has two receivers for solar monitoring at 45 and 90 GHz, with right and left circular polarization measurements and temporal resolution of 10 ms. The 45 GHz telescope consists of a 44 cm diameter reflector and the 90 GHz of a lens with 16.5 cm diameter. Designed to observe the entire disk of the Sun, it has a beam width at half power of 1.4 °. The telescope sensitivity is 2 and 4 K corresponding to 4 and 20 Solar Flux Units (1 SFU = 10 4 Jy) and an aperture efficiency of (50 + 5)% and (75 + 8)% at 45 and 90 GHz, respectively (Valio et al. al. 2013, Solar Physics, 283: 651: 665).

 

 

45 (GHz)

90 (GHz)

FWHM

1,4o

1,4o

Sensitivity(K)

2

4

Sensitivity(SFU)