Abstract:
We report rare events, above 1000 MHz, in which emission at the fundamental and at second harmonic frequencies show nearly identical fine structures. These high resolution observations are obtained from the Brazilian Solar Radio Spectrograph operating in the frequency range (2150 ± 100) MHz, and the Ondrejov observatory Solar Radio Spectrograph operating in the frequency range of (800–2000) MHz. These bursts have flux values of about 300 s.f.u. and total duration between 100 and 500 ms. The frequency and flux ratios of the harmonically related narrow band bursts varied from 1.76 to 2.29 and 1.28 to 3.57, respectively. The lower observed flux of the fundamental component in comparison to the second harmonic could be due to its higher collisional absorption assuming that the generation mechanism of these bursts is due to the beam plasma interaction. The heights of the acceleration regions estimated from the starting frequencies of the decimetric fine structures are less-than-or-equals, slant104 km.
