Properties and the origin of Almost Monoenergetic Ion (AMI) beams observed near the Earth's bow shock

Abstract. Beams of Almost Monoenergetic Ions (AMI) in the energy range from 20 to 800 keV were discovered in the DOK-2 experiment (Interball project) in the magnetosheath and upstream of the Earth's bow shock. This work summarizes the analysis results of ~730 AMI events registered in 1995–2000. Statistics of AMI properties, their nature and origin are considered. The analysis of a large array of new data confirmed our earlier suggested ideas on the AMI nature, origin, and their acceleration model. These ideas were further developed and refined. According to this model, AMI are a result of solar wind ions acceleration in small regions with a potential electric field arising due to disruptions of the bow shock current sheet filaments. It has been found that the reason of the current filaments disruptions in most cases was the Hot Flow Anomaly phenomenon (HFA) caused by an interaction of a tangential discontinuity in the solar wind with the Earth's bow shock. It is shown that the study of AMI can provide new information on large-scale properties and dynamics of the bow shock current sheet.