Pi2 magnetic pulsations as response on spatio-temporal oscillations of auroral arc current system

Abstract

Pi2 magnetic pulsations in the period range from 40 to 150 s are excited both at the magnetospheric substorm onset and during pseudobreakups. Using observations at the 190-210° MM we study the association between the characteristics of high-latitude Pi2 pulsations and parameters of wave-like and vortex auroral structures of 50-200 km scale in the brightening auroral arc during short-term (˜5-10 min) activations. We found that the maximum Pi2 amplitude is observed at the same latitude where the auroral arc is located. The period of high-latitude Pi2 pulsations is found to be consistent with the ratio of the luminosity wavelength to their propagation velocity and/or coincides with the lifetime of luminosity bright spots. The Pi2 polarization patterns are defined by the direction of luminosity bright spot rotation. These findings indicate that high-latitude Pi2 pulsations are the response of spatio-temporal current system oscillations of the auroral arc.