Variation and modeling of ultraviolet auroral oval boundaries associated with interplanetary and geomagnetic parameters

Abstract

AbstractA large data set of auroral poleward/equatorward boundary, which are automatically identified from more than 60,000 images acquired by Polar ultraviolet imager, is used to study the variation of auroral boundaries associated with the interplanetary/geomagnetic environments and dynamic parameters of the magnetosphere. A total number of 3,805,000/1,215,000 points for poleward/equatorward boundary were identified from the data set. It is found that the poleward/equatorward boundaries show an equatorward movement with the increase of Kan‐Lee electric field. The poleward/equatorward boundaries in the nightside sector (1800–0600 magnetic local time (MLT)) show an equatorward motion with the increase of the value of IMF By and the north‐south electric field. The equatorward boundary (1800–0300 MLT) shows a quasi‐linear equatorward displacement with the increase of solar wind dynamic pressure and speed. The poleward boundary (excluding midday sector) and equatorward boundary expand equatorward with the increase of AE index. The auroral oval boundary model with input parameters of the three components of IMF, solar wind speed and density, and AE is developed by using multivariate regression method. Evaluation of the model shows that the mean absolute deviation of the model in every MLT sector is 1.3–2.1° magnetic latitude (MLAT) for the poleward boundary and 1.3–2.5° MLAT for the equatorward boundary, respectively, when input parameters are within valid value coverage (three components of IMF are each from −8 to +8 nT, and the values of solar wind speed and density, and AE are not more than 550 km/s, 20/cm−3, and 520 nT, respectively).