The Breathing Plasmasphere: Erosion and Refilling

Abstract

Global observations of helium ions from the Imager forMagnetopause-to-Aurora Global Exploration mission Extreme Ultraviolet Imager are used to examine the dynamics of inner plasmasphere content using integrated mass through times of erosion and refilling. Perhaps the most basic and important attributes of the plasmasphere are its mass and spatial distribution. However, our understanding is often constrained by the method of measurement. Storm-time loss of plasmasphere content is a kind of exhalation where plasma is lost. Refilling or inhalation into the body of the plasmasphere occurs during the following calm. Plasma lost inside the average eroded plasmapause boundary ranges from 22% to 42% and outside from 35% to 72%. Following the start of refilling, the innermost region shows the lowest observed refilling rates. Mass refilling rates further away from Earth rise to a maximum ∼6,000 kg per day that falls with increasing distance from Earth. More variability and higher refilling rates are found during lower solar activity. The mass content of the innermost plasmasphere was also followed for 54 days when it exhibited eight "breathes." Using this analogy only the first inhale/exhale is "deep." The remaining carry forward the consequences of past and continued activity that prevents full recovery. GALLAGHER ET AL.

Magnetospheric Mass Density as Determined by ULF Wave Analysis

“…A major goal of magnetoseismology is to develop a global model of ρ. Ideally, the model will reach a degree of maturity similar to that of existing models of the magnetic field (e.g., Sitnov et al, 2008), the electron density (e.g., Carpenter and Anderson, 1992;O'Brien and Moldwin, 2003;Archer et al, 2015;Liu et al, 2015), the He + density (e.g., Gallagher et al, 2021), and the density of low energy (but excluding cold) ions (e.g., Kistler and Mouikis, 2016). Magnetoseismic studies using ground magnetometer data have made significant progress in this regard.…”

The Effect of the Thermosphere on Ionosphere Outflows

“…Because the solar cycle so strongly affects thermosphere and exosphere composition, the variation of cold H + refilling outflows with the solar cycle, specifically with the F 10.7 extreme ultraviolet (EUV) index, is quite counter-intuitive. At high F 10.7 , when the ionosphere F layer is relatively strong, observed plasmasphere refilling rates at geosynchronous altitudes are relatively weak (Lawrence et al, 1999;Gallagher et al, 2021). As shown graphically in Figure 1D, and described by Richards and Torr (1985), the limiting H + outflow flux is proportional to the supply of O + ions and H atoms at outflow source height Z 0 (700-1,100 km):…”

Charge-Exchange Byproduct Cold Protons in the Earth’s Magnetosphere

“…On the dayside, the sunlit ionosphere has cold-proton outflows that can build up to refill the outer plasmasphere in the dipolar magnetosphere. It is argued that there are two different timescales for the refilling (Wilson et al, 1992;Lawrence et al, 1999;Su et al, 2001;Gallagher et al, 2021): a slow refilling at early times and a faster refilling at late times. (But see Denton and Borovsky (2014) for evidence against a two-timescale picture.…”