A Survey of Dense Low Energy Ions in Earth's Outer Magnetosphere: Relation to Solar Wind Dynamic Pressure, IMF, and Magnetospheric Activity.

Autor: Hull AJ; Space Sciences Laboratory University of California, Berkeley Berkeley CA USA., Agapitov O; Space Sciences Laboratory University of California, Berkeley Berkeley CA USA., Mozer FS; Space Sciences Laboratory University of California, Berkeley Berkeley CA USA., McFadden JP; Space Sciences Laboratory University of California, Berkeley Berkeley CA USA., Angelopoulos V; Earth, Planetary and Space Sciences Institute of Geophysics and Space Physics University of California, Los Angeles Los Angeles CA USA.
Jazyk: angličtina
Zdroj: Journal of geophysical research. Space physics [J Geophys Res Space Phys] 2021 Sep; Vol. 126 (9), pp. e2021JA029208. Date of Electronic Publication: 2021 Sep 03.
DOI: 10.1029/2021JA029208
Abstrakt: 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.
(© 2021. The Authors.)
Databáze: MEDLINE
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