Response of morning auroras and cosmic noise absorption to the negative solar wind pressure pulse: A case study

A case study of response of particle precipitation to negative impulse of solar wind dynamic pressure is presented. The study was performed using the data of PGI all-sky camera at Barentsburg observatory (arch. Spitsbergen) and imaging riometer IRIS located in Northern Finland. Two stages of the response were found. At first, the reduction of cosmic noise absorption (CNA) in the center of the auroral zone and the decay of the auroras near the pole boundary of the auroral oval were observed. The second stage was started in 10 minutes and characterized by the appearance of new bright forms near the pole boundary of the auroral oval. No significant changes in the CNA were observed at this time. We connect such reaction of the auroras and CNA during the first stage with propagation of the front of MHD disturbance through the source of precipitating particles in the magnetosphere. We explain the changes in the aurora dynamics at the second stage by the largescale reconfiguration of the magnetosphere which was manifested in the ionosphere as a change of position of dawn vortex of ionosphere convection in the region of the optical observations.