Study On Global Auroral Characteristics Extraction And Auroral Substorm

Aurora is caused by interaction between the solar wind and the Earth’s magneticfield. It has been studied by the use of many kinds of instruments, such asmagnetometers, all sky imager based on the ground, etc.. The observations based on theground can just obtain the local auroral information, which doesn’t benefit the researchon global aurora activities. With the rapid development of science and technology, theauroral images acquired by the space-borne imager make it possible to study the auroralmechanism and solar-terrestrial interactions from the view of global auroral luminosity.In this paper, the global auroral images are provided by the Polar UltravioletImager (UVI) instrument. This paper mainly includes three major parts. Firstly, analgorithm extracting auroral oval region from one UVI image is presented based on thefuzzy local information c-means clustering. Evaluated by comparing with the standardauroral boundaries, the presented algorithm shows more accurate. And then, themethods determining several morphologic features such as the area of polar cap aregiven based on the auroral region extracted. Secondly, the relationships betweenLyman-Birge-Hopfield auroral emissions and precipitating particle energies arediscussed, and it is proposed that global maps of energy input into the aurora could bederived empirically just from the UVI images. Experiments on two samples show it iseffective. Last but not the least, the global morphologic characteristics of auroral regionare described based on the UVI image sequences during the development of auroralsubstorm, and a possible scheme on the automatic detection of substorm onsets ispresented.