ИСТИНА

Our recent study (Yagova et al, 2017) of auroral substorms shows, that ULF pulsations are seen in ground-based magnetic and luminosity data for a few hours preceding isolated non-triggered substorms. Two possible origins of these pulsations are seemed to be discussable: ULF disturbances in the solar wind (which should be counted as an external substorm trigger in this case) or processes inside the magnetosphere which lead to a substorm generation. The present investigation is aimed on a detailed case study of pre-substorm variations in both the interplanetary and magnetotail magnetic field, in addition to simultaneous electron concentration and particle flux parameters.