Statistical properties of dayside subauroral proton flashes observed with IMAGE-FUV

Abstract

The SI12 instrument of the FUV experiment onboard the IMAGE satellite is specifically devoted to the observation of the proton aurora. Transient subauroral proton aurora was detected with SIl2 in response to a solar wind dynamic pressure increase. These Dayside Subauroral Proton Flashes (DSPF's) take place on field lines of L-Shell as low as 4, and possibly result of an increase of EMIC growth rate instability due to the compression of the dayside magnetosphere by the increased solar wind dynamic pressure. In this study, a set of 75 DSPF's observed with SI12 related with a solar wind dynamic pressure increase is studied. Statistical distributions of relevant quantitative and morphologic indicators of the DSPF's properties are computed. Correlations between these indicators and the solar wind properties are also studied. It is found that the solar wind dynamic pressure is the key parameter controlling the DSPF maximum power, maximum flux, magnetic latitude and extent in MLT. Also, DSPF's occur preferentially in the afternoon sector, where the plasma temperature anisotropy is higher, so that the EMIC instability threshold is more easily exceeded. Moreover, no correlation is found between the DSPF's characteristic decay time and the solar wind properties, suggesting that this parameter is internally controlled by the properties of the magnetospheric plasma. In this dataset, no correlation is found relating the IMF and the DSPF properties.