Solar atmospheric model with spicules applied to radio observation

¹ CRAAM, Instituto Nacional de Pesquisas Espaciais, São José dos Campos, SP 12201-970, Brazil e-mail: caius@craam.mackenzie.br
² CRAAM, Universidade Presbiteriana Mackenzie, São Paulo, SP 01302-907, Brazil

Received: 21 September 2004
Accepted: 30 November 2004

Abstract

An atmospheric model was constructed in order to reproduce quantitatively the observations at 17 GHz from Nobeyama Radio Heliograph, namely the brightness temperature at disk center (from 1.4 to 400 GHz), center-to-limb brightening distribution, and radius derived from 17 GHz solar maps. The two dimensional solar atmospheric model, that takes into account the curvature of the Sun, includes spicules, which physical characteristics (such as size, temperature, density, position, and inclination angle) were randomly attributed. After the interferometer instrumental response is taken into account, the results showed than an atmospheric model without spicules produces 36% of limb brightening, approximately the value observed at the solar poles. However, the inferred solar radius from the model (970'') was 6'' smaller than the mean value derived from the solar maps. An improvement of the model is made by including spicules. Results from this upgraded model showed that depending on their physical parameters, limb brightening and solar radius values are obtained in agreement with the radio observations (except for polar regions).