Microwave study of trap and precipitation of electrons in solar burst / Estudo em microondas do aprisionamento e precipitação de elétrons em explosões solares

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

We have studied the process of particle number density evolution during solar flares from the microwave emission point of view. In order to do this, we have used the database of Nobeyama Radio Observatory (NRO), with approximately 100 events that occurred between 1998 and 2000 that were observed in seven frequencies (1, 2, 3.8, 9.4, 17, 35, and 80 GHz), in two polarization modes. Since the trap-plus-precipitation models of solar bursts present different characteristic time scales for both particle populations, we have made the separation of the observed emissions by filtering the total fluxes. We have used a simplified magnetic field configuration (dipolar magnetic field) as an ?effective? configuration for the real geometry of the trap-plus-precipitation model. Thus, we analyzed their respective gyrosynchrotron spectra and obtained typical parameters, such as the spectral index of the electrons: loop-top ~3.4, footpoints ~3.8; intensity of the magnetic field: loop-top ~480G, footpoints ~860G; loss cone angle ~48o and the fraction of particles in precipitation in relation to the total number of ~33%. These values indicate that the microwave signatures of the solar burst are consistent with the hypothesis of weak pitch angle diffusion with Coulomb collisions. We also analyzed through the spectral broadening of these bursts, the spatial anisotropy of the existent magnetic field. The result of this work suggests that the magnetic field presents higher anisotropy at the loop footpoints than the loop-top and higher spatial resolution is necessary to better understand the magnetic field anisotropy.

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