A Survey of Dense Low Energy Ions in Earth's Outer Magnetosphere: Relation to Solar Wind Dynamic Pressure, IMF, and Magnetospheric Activity. Issue 9 (3rd September 2021)

• Record Type: Journal Article
• Authors: Hull, Arthur J.; Agapitov, Oleksiy; Mozer, Forrest S.; McFadden, James P.; Angelopoulos, Vassilis
• Is Part Of: Journal of geophysical research. Volume 126:Issue 9(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-03
• Subjects: plasmaspheric plumes -- warm plasma cloak -- ion outflow -- cold dense magnetospheric plasma -- low energy ions -- outer magnetosphere; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2021JA029208
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The properties of cold, dense, low energy ( < 150 eV) ions within Earth's magnetosphere between 6 and 14 R E distance are examined using data sampled by Time History of Events and Macroscale Interactions during Substorms spacecraft during a new low‐energy plasma mode that operated from June 2016 to July 2017. These ions are a persistent feature of the magnetosphere during enhanced solar wind dynamic pressure and/or magnetospheric activity. These ions have densities ranging from 0.5 to tens of c m − 3, with a mean of ∼ 1 c m − 3 and temperatures of a few to tens of eV, with a mean of ∼ 13 eV. These yield cold to hot ion density and temperature ratios that are 4.4 and 4 × 1 0 − 3, respectively. Comparisons reveal that the cold ion densities are positively correlated with solar wind dynamic pressure. These ions are organizable, according to their pitch‐angle distribution, as being transverse/convection dominated (interpreted as plume plasma) or magnetic field‐aligned (FAL) (uni‐ or bi‐directional characteristic of ion outflow or cloak plasma). Transverse ions preferentially occur in the prenoon to dusk sectors during sustained active magnetospheric conditions driven by enhanced solar wind dynamic pressure under southward B z and westward B y IMF orientations. Transverse ion velocities (reaching several tens of km/s) have a westward directed tendency with a slight radially outward preference. In contrast FAL ions preferentially occur from morning to noon during northward IMF orientations, enhanced solar wind dynamic pressure, and quiet magnetospheric conditions within several hours after moderate to strong activity. The FAL ions also have bulk velocities ≲ 30 km/s, with an eastward and radially outward tendency. Key Points: Dense low energy ions are a persistent feature of the magnetosphere during enhanced solar wind dynamic pressure and/or Kp Low energy transverse ions tend to occur in duskside magnetosphere under southward B z and westward B y IMF conditions, with westward flow Low energy magnetic field‐aligned (uni‐ or bi‐directional) ions tend to occur in the dawnside under northward IMF, with an eastward flow