Quiet time solar illumination effects on the fluxes and characteristic energies of ionospheric outflow

Abstract

[1] We report on the characteristic energy, intensity, and flow rate of escaping ionospheric ions as a function of solar illumination. The data presented here were acquired with the Toroidal Ion Mass-Angle Spectrograph (TIMAS) instrument on the Polar satellite at altitudes of 6000 to 9000 km, during solar minimum. To obtain uniform coverage under various solar illumination conditions, data were restricted to geomagnetically quiet intervals when the Dst index was above À50 nT. We explicitly report data for four magnetic local time ranges. Our investigation confirms many of the characteristics of ion outflows deduced from earlier episodic studies and identifies an anticorrelation in the dependence of beam and conic fluxes on solar illumination, which we attribute to variations in the altitude at which auroral acceleration processes occur. We find that the cusp is an important but not dominant source of ionospheric plasma for the magnetosphere. We conclude that significantly different plasma energization and/or transport mechanisms are dominant in the cusp and the midnight sectors. In addition, we conclude that variations in the solar EUV and geomagnetic energy inputs into the ionosphere, rather than the longer timescale seasonal and annual variations in solar illumination, determine the global rates of H + and O + outflow. The data presented here provide comprehensive and realistic boundary conditions for large-scale magnetospheric models during nonstorm times.

Survey of cold ionospheric outflows in the magnetotail

“…As was mentioned in the introductory section, there have been a large number of studies on ion outflow from the polar caps at low altitudes using different spacecraft: DE-1 (Nagai et al, 1984;Chandler et al, 1991), Akebono (Abe et al, 1993(Abe et al, , 1996(Abe et al, , 2004Cully et al, 2003a), and Polar (Moore et al, 1997;Su et al, 1998;Chappell et al, 2000;Lennartsson et al, 2004;Liemohn et al, 2005;Huddleston et al, 2005;Peterson et al, 2006Peterson et al, , 2008. The study at highest altitude so far was conducted by Su et al (1998) using Polar data at apogee altitude at 8 R E above the polar caps.…”

“…Peterson et al (2006Peterson et al ( , 2008 has put much effort in comparing measurements from spacecraft at different altitudes. The tables included in Peterson et al (2008) and show that the cold ion flow is higher than the ion flow with higher energy.…”

“…The current understanding of the high-latitude ion outflows, including the polar wind, can mainly be attributed to a wealth of studies from Akebono (Abe et al, 1993(Abe et al, , 1996(Abe et al, , 2004Cully et al, 2003a) and Polar (e.g. Moore et al, 1997;Su et al, 1998;Chappell et al, 2000;Lennartsson et al, 2004;Liemohn et al, 2005;Huddleston et al, 2005;Peterson et al, 2006). More details on the previous measurements of the high-latitude ion outflows can be found in the recent review articles by Yau et al (2007) and Moore and Horwitz (2007).…”

Energy conversion through mass loading of escaping ionospheric ions for different Kp values

“…The second possible factor to add a nonlinear effect in Eq. (7) is the significant enhancement of ion outflow during periods when the solar extreme ultraviolet (EUV) flux is enhanced (Cully et al, 2003;Peterson et al, 2006). This additional effect activates the nonlinear feedback between the ion escaping rate F load and energy extraction rate K. This would cause much higher geomagnetic activities, causing extremely high F load .…”

“…Due to a strong dependence on Kp and solar EUV of the ion outflow rate in the cusp and its vicinity (Norqvist et al, 1996;Cully et al, 2003;Peterson et al, 2006;Slapak et al, 2017), the expected current system should have a stronger dependence on Kp and EUV than what the current system relevant to the global electrodynamics has (e.g. Fujii and Iijima, 1987;Thomsen, 2004, and references therein).…”