"Almost monoenergetic ions – new source of information on the dynamics of space plasma current sheets
V. N. Lutsenko (IKI)
Abstract:
It seemed generally adopted that energetic spectra of particles accelerated in different processes in space plasma have a smooth shape with a negative, as a rule, slope. Such spectra shapes were observed tens of years in multiple experiments on spacecrafts and followed from current theoretical models.
In 1995-2000 in DOK-2 experiment (Interball project), were an instrumentation with a very high energy resolution was used, beams of almost monoenergetic ions (AMI) with energies from 30 to 800 keV were discovered. One – two minute bursts of such ions were observed in several regions of the Earth’s magnetosphere: in the geotail plasma sheet, in the magnetosheath and upstream of the bow shock. The ion spectra consist of one, two or three lines with the relative FWHM of 17-25 %. In the same time no lines were observed in electron spectra. The total number of AMI events exceeds 200.
We propose a hypothesis on the nature and origin of AMI according to which they are solar wind ions accelerated in bursts of strong, potential, electric field arising by disruption of filaments of current sheets forming the borders of different regions of the magnetosphere. This hypothesis explained all main observed AMI features. The current is here an agent concentrating in a small region (~1000 km) an energy distributed previously in a large space. Observation of AMI may give information on processes with current sheets on a large distance from them. The AMI discovery gives a new support of H. Alfvén ideas on a great role of electric currents in a space plasma.