Source Parameters Estimated from Decimetric Type-U Solar Bursts Recorded by Brazilian Solar Spectroscope

F.C.R. Fernandes$^1$, J.R. Cecatto$^1$, H. Meszarosova$^{1,2}$, H.S. Sawant$^1$

$^1$National Institute for Space Research - INPE, San Jose dos Campos, SP, Brazil
$^2$Astronomical Institute of the Academy of Sciences of the Czech Republic, 25165 Ondrejov, Czech Republic

The Brazilian Solar Spectroscope (BSS) is dedicated to solar observations with high frequency (3-10 MHz) and high time (10-100 ms) resolutions in the frequency range of (1.0-2.5) GHz. BSS is in regular operation at National Institute for Space Research (INPE), in Brazil, since 1998. This spectrograph operates in conjunction with a 9-meter diameter polar-mounted parabolic antenna. We present the results of the analysis of three different type-U bursts recorded by BSS in the period of 2000-2001. Considering that type-U bursts are the signature of radio emission generated by the electron beam traveling along the closed magnetic loops, physical parameters of the sources were estimated from the observational parameters of the bursts. The capabilities of the BSS to record fine structures in the decimeter radio emission with high spectral and high temporal resolution enabled us to determine the turning frequency of burst and the frequency band and the drift rates of ascending and descending branches of the U-shape structures recorded. Also, the temperature of the coronal loop apex was estimated from the total length of the ascending and descending branches. The low limits for magnetic field, considering radio emission at fundamental and second harmonic, were estimated for each burst. The results of analysis will be presented and discussed in comparison with the results reported previously in the literature for the other frequency ranges.