Connecting Energy Input With Ionospheric Upflow and Outflow

Abstract

The transport of ions from the ionosphere and into the magnetosphere, known as "ionospheric outflow" or "ion outflow," has many implications for Earth's magnetospheric composition and dynamics. Plasma in the magnetosphere resulting from ionospheric outflow is found to alter magnetic reconnection (e.g., Karimabadi et al., 2011;Shay et al., 2004), change the flows in the magnetotail (e.g., Brambles et al., 2011;Garcia et al., 2010), and impact the inner magnetosphere (e.g., Moore et al., 2005;Welling et al., 2011). Moreover, the ionosphere is at times found to be a dominant source of magnetospheric plasma, particularly during geomagnetic storms (Lennartsson et al., 1981) and is arguably a fully adequate source of near-Earth plasma (Chappell et al., 1987;Huddleston et al., 2005). Given the importance of ion outflow to the magnetosphere, it is critical to understand how energy input to the ionosphere drives ionospheric outflow.Energy input in the form of electromagnetic energy and particle precipitation has been shown in observations to be associated with the generation of ion outflows. In particular, statistical studies using data from the POLAR spacecraft (Zheng et al., 2005) and the Fast Auroral SnapshoT (FAST) spacecraft (Strangeway et al., 2005) found a strong correlation between ion outflow flux, Poynting flux, and soft electron precipitation. In these studies, energy inputs and ion outflows were compared at high attitudes, far above the source region of the ion escape. Earlier observations from the Dynamics Explorer (DE) 2 spacecraft also found a connection between soft electron precipitation and ion upflows above the aurora (Seo et al., 1997). Interestingly, the studies of Zheng et al. (2005) and Strangeway et al. (2005) focus on the DC, or quasi-static, Poynting flux. The DC Poynting flux is associated with the large scale convection which can influence ion outflow by generating ion upwelling driven by frictional heating of the ion gas. While much of this heating occurs in the E-region, large amounts are also possible in the F-region (Killeen & Roble, 1984) which can then generate significant transient ion upwelling in the cusp and auroral regions (Gombosi & Killeen, 1987). Similarly, soft electron precipitation can heat the thermal electron population and generate secondary electrons which can enhance the ambipolar electric field and thus lift ionospheric plasma to higher altitudes (Su et al., 1999). The upwelling of plasma caused by either of these processes was speculated by Strangeway et al. (2005) as the first step of the causal chain explaining ion outflow with subsequent wave-particle interactions (WPI) being required to further accelerate the ions to create the energized outflow observed by FAST and POLAR. The online supplemental materials for Brambles et al. ( 2011) expands

Nightside Auroral H+ and O+ Outflows Versus Energy Inputs During a Geomagnetic Storm

“…More recently, Glocer and Daldorff (2022) has modeled the outflow for both H + and O + . They evaluated the responses to different inputs separately, but also modeled responses with combined inputs.…”

“…The fact that H + flux does show some dependence on the wave energy input on the dayside may just be due to differences in the time dependence of the outflow for flux tubes in the different region. Glocer and Daldorff (2022) showed that after the flux tube is exposed to the auroral input and before it has reached steady state, the flux can exceed the limiting flux, and H + does show some response to wave power. It could be that the fast convection over the cusp region leads to a bigger time dependence affect.…”

Reconstruction Analysis of Global Ionospheric Outflow Patterns

“…Observation of enhanced N + fluxes outside the auroral region would reveal new insight into latitudinal transport of heavy ions and consequently the overall ionospheric dynamics. Because the mass distribution of accelerated ionospheric ions reflects the source region of the low altitude ion composition, any measurement of a minor ion constituent of the accelerated plasma serves as a tracer of ionospheric and energization processes (e.g., Glocer & Daldorff, 2022; Winningham & Gurgiolo, 1982). Ion velocity space measurements alone reveal the basic breakdown of these processes, separating classic polar wind (heating only, allowing the high‐energy tail to escape) from potential‐driven outflow (various E || contributions) and wave heating (transversely accelerated ions and conics).…”

Science Case for a Global Ionospheric Outflow Mission

“…Observation of enhanced N + fluxes outside this region would reveal new insight into latitudinal transport of heavy ions and therefore the overall ionospheric dynamics. Because the mass distribution of accelerated ionospheric ions reflects the source region of the low altitude ion composition, the minor ion component of the accelerated plasma serves as a tracer of ionospheric and energization processes (e.g., Winningham & Gurgiolo, 1982;Glocer & Daldorff, 2022). Ion velocity space measurements alone reveal the basic breakdown of these processes, separating class polar wind (heating only) from potentialdriven outflow (various E|| contributions) to wave heating (transversely accelerated ions and conics).…”