A influência dos parâmetros do vento solar na emissão de AKR durante tempestades magnéticas / The influence of the solar wind parameters on the AKR emission during magnetic storms

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Several phenomena could be better studied and even disclosed after the development of the satellites and spacecrafts. Auroral Kilometric Radiation (AKR) is one of these phenomena. AKR was first detected only about thirty years ago; its typical frequencies are too low to penetrate earthward across the ionosphere. This radiation is generated through wave-particle interactions, in the nightside region above the auroral ionosphere. It grows at the expense of free energy from the precipitating auroral electron beam. It is generated mainly in the extraordinary (X) mode, in the frequency range of 20-800 kHz, near the local electron cyclotron frequency. Nowadays, it is well known that AKR is intensified during magnetic substorms and has a good correlation with the AE magnetic index. However, recent studies showed that the radiation disappears in the initial and main phases of some magnetic storms, in spite of the large enhancement of the AE index and field aligned currents. The radiation activates strongly in the recovery phase. This behavior suggests that the field-aligned electric field, which accelerates precipitating electrons and drives fieldaligned currents, is not formed in the initial and main phases of some magnetic storms. In this work, we are interested in quantify the AKR emission and study the influence of the solar wind parameters on AKR during magnetic storms. In order to do this, a numerical AKR index was developed, based on the intensity of the auroral radiation shown by AKR dynamical spectra. This numerical AKR index represents the intensity of AKR and we called it AKR index. We selected a few events for which we have available the AKR spectrum along with the interplanetary plasma parameters and the geomagnetic indices Dst and AE. Among the selected events we found some where AKR is present all the way during a magnetic storm, but others where AKR is suppressed during the initial and main phases of the storms. By analyzing the events we observe that the main parameter to determine the presence or absence of AKR is the plasma density of the plasma sheet. However, the parameter that best correlates to AKR was found to be the solar wind velocity.

ASSUNTO(S)

radiação quilométrica auroral (akr) interações sol space geophysics magnetic storms plasmas espaciais solar terrestrial interaction electromagnetic radiation geofÍsica espacial auroral kilometric radiation (akr) solar wind terra space plasmas tempestades magnéticas radiação eletromagnética vento solar atividade auroral auroral activity

ACESSO AO ARTIGO

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