Electric air-earth vertical current pulsations at Hornsund during polar substorms: Case study
The long-period pulsations (f2-5 mHz) in the air-earth vertical electric current (Jz) were observed at polar latitudes (obs. Hornsund, Svalbard, Φ =74°) during polar substorms. Two substorms on February 04, 2004 in the time-interval of 18-24 UT have been analyzed. The first substorm (18-20 UT) was observed only at polar latitudes and the second one (22-24 UT) started at auroral zone and then very quickly propagated to polar latitude. Both substorms were accompanied by impulsive Jz variations. For the first time, a simultaneous occurrence of pulsating riometer absorption enhancement as well as Pi2-Pi3 geomagnetic pulsations was found. There were very large similarities in the wavelet structure of Jz, geomagnetic, and riometer pulsations during these substorms in spite of difference in their nature. Each peak in riometer absorption was coincided with the Jz peak. It is known that the air-earth current density is determined by the potential difference between the ground and the ionosphere and the local profile of the atmospheric conductivity. The pulsating energetic particle precipitation (riometer absorption) may modulate the ionospheric conductivity, electric fields and currents and modify the local atmospheric circuit. This might be seen in Jz variations. We assume that the ground based long-period geomagnetic pulsations could be originated at ionosphere altitudes by the quasi-periodical variations in the ionosphere currents and conductivity. The riometer absorption bursts reporting here are most likely associated with the cyclotron instability of the trapped energetic electrons. Another possible source of the acceleration of the energetic electrons during the polar substorm could be the influence of the quasi-periodic impulsive variations of the inductive electric field near neutral line region in the magnetotail.
O.V. Kozyreva N.N. Nikiforova N.G. Kleimenova S. Michnowski M. Kubicki
Institute of the Earth Physics RAS, Moscow, Russia Institute of Geophysics PAS, Warsaw, Poland
国际会议
第13届国际大气电学会议(The 13th International Conference on Atmospheric Electricity)
北京
英文
2007-08-13（万方平台首次上网日期，不代表论文的发表时间）