Navegando Centro de Rádio Astronomia e Astrofísica Mackenzie (CRAAM) por Autor "Hidalgo Ramírez, Ray Fernando"
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- TesePolarização das emissões solares em comprimentos de onda milimétricosHidalgo Ramírez, Ray Fernando (2019-08-26)
Escola de Engenharia Mackenzie (EE)Polarization of radio emissions from solar bursts provides essential information about conﬁned plasma regimes submitted to magnetic ﬁeld in quiescent, pre-explosion, sudden energy release and decay phases. Investigations at microwaves and longer wavelengths have widely been carried out. Observations of polarization are carried out continuously by the ﬁrst time at two millimeter wavelengths by two solar radio polarimeters named POEMAS at 45 and 90 GHz (6.6 and 3.3 mm, respectively) operating at El Leoncito Observatory, Argentina Andes. The present research is divided in two parts. First, the center-to-limb variation of polarization of solar bursts is investigated. A total of 30 bursts observed by the radio polarimeters, between 2012 and 2013, were analyzed. We show increasing degreeofpolarizationwithheliocentricangle,butatapproximately50∘ aturnover isobservedwiththedegreeofpolarizationbeginningtodecreaseforlargerangles. We also found a weak correlation between bursts ﬂux density and their heliocentricangle,i.e.solarburstswithhigherﬂuxdensitytendtooccurclosertothelimb. To interpret the observational results, a numerical simulation of the polarization degree spectra for gyro-synchrotron emission was performed. As for the second part of this research, the S-component time evolution at millimeter wavelengths of a active region throughout the solar disk is studied. We observe ﬂux enhancementswiththepassageoftheactiveregionwithaspectralindex,atthemaximum, between 2-6 taking into account the measurement of errors. This double spectrum of active region emission at radio wavelengths can favor a core-halo distribution ofradiobrightnessoveractiveregions.Anenhancementinthedegreeofpolarization of about 40 % is observed in the second half of the active region transit at 45 GHz, however, it is disregarded due to the error propagation. Also, no signiﬁcant enhancement in the degree of polarization is observed at 90 GHz.