@InProceedings{AmaroSilvCost:2022:StAsSo,
               author = "Amaro, Abimael Xavier Barbosa and Silva, Marlos Rockenbach da and 
                         Costa, Joaquim Eduardo Rezende",
          affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Instituto Nacional de 
                         Pesquisas Espaciais (INPE)}",
                title = "Study on the association of solar gyroresonance emission sources 
                         with brightness temperature intensification at 17 GHz",
            booktitle = "Proceedings...",
                 year = "2022",
         organization = "EGU General Assembly",
            publisher = "EGU",
             abstract = "Remarkable works done in the last decades by many authors on the 
                         solar gyroresonance mechanism have illuminated the way to 
                         establish the relationship between this form of emission and 
                         magnetic fields in the solar atmosphere and to know the magnetic 
                         nature of the middle and upper layers of the active regions. 
                         Despite all these advances, solar physics still needs a direct 
                         means (without magnetograms) of identifying the sources of 
                         gyroresonance emission. In search of a solution to this problem, 
                         we used solar images at 17 GHz synthesized by the Nobeyama 
                         Radioheliograph (NoRH) to map the likely sources of gyroresonance. 
                         To achieve this result, we first hypothesized that gyroresonance 
                         and bremsstrahlung mechanisms can generate a large brightness 
                         temperature intensification due to the close relationship such 
                         mechanisms have with magnetic fields and because of the role of 
                         the magnetic field in controlling the brightness of the solar 
                         atmosphere in the radiofrequency range. To test this hypothesis 
                         regarding the gyroresonance process, we selected 8 large active 
                         regions (ARs) among the HMI magnetograms generated by the Solar 
                         Dynamics Observatory (SDO) corresponding to the 1st half of the 
                         24th solar cycle. We then analyzed each AR through its magnetogram 
                         and its image at 17 GHz. Aiming to verify, in these radio maps, 
                         whether there is a correspondence between brightness bumps and 
                         parameters associated with gyroresonance emission, we constructed 
                         three categories of brightness maps for each active region, 
                         respectively presenting the field of: brightness temperature in BT 
                         maps, brightness temperature gradient in BTG maps, and brightness 
                         temperature gradient to brightness temperature ratio in BTG/BT 
                         maps. Such parameters are the characteristic circular 
                         polarization, whose modulus is greater than 30%, and 
                         characteristic magnetic field strengths, associated with the 
                         gyroresonance radiation at 17 GHz for 3rd and 4th harmonics. Such 
                         a step also aimed to verify which of these categories would best 
                         map the putative sources of gyroresonance emission. On these maps, 
                         we then plotted the contours of the characteristic parameters. For 
                         each AR, we also obtained the degree of correlation between its 
                         brightness variables and the characteristic polarization. We then 
                         observed that the contours of characteristic magnetic field 
                         strengths are predominantly enveloped by the area of the 
                         brightness bumps, while the contours of the characteristic 
                         polarization fit well to such areas, being better fitted to the 
                         relative bumps (in the BTG/BT maps). In the statistical analysis, 
                         we observe that for each active region, there is a predominance of 
                         strong correlations between the brightness variables and the 
                         modulus of the characteristic polarization. Such correlation tends 
                         to be highest for the brightness temperature. For each brightness 
                         variable, the highest correlations tend to occur for the 
                         predominant polarization direction of the active region. The data, 
                         therefore, indicate a high probability that the gyroresonance 
                         emission mechanism was at least one of the important causes of the 
                         radio bumps produced in the observed active regions.",
  conference-location = "Online",
      conference-year = "23-27 May 2022",
                  doi = "10.5194/egusphere-egu22-564",
                  url = "http://dx.doi.org/10.5194/egusphere-egu22-564",
             language = "en",
           targetfile = "EGU22-564-print.pdf",
        urlaccessdate = "19 maio 2024"
}