Impacts of Ionospheric Ions on Magnetic Reconnection and Earth's Magnetosphere Dynamics

Abstract

Ionospheric ions (mainly H + , He + , and O + ) escape from the ionosphere and populate the Earth's magnetosphere. Their thermal energies are usually low when they first escape the ionosphere, typically a few electron volt to tens of electron volt, but they are energized in their journey through the magnetosphere. The ionospheric population is variable, and it makes significant contributions to the magnetospheric mass density in key regions where magnetic reconnection is at work. Solar windmagnetosphere coupling occurs primarily via magnetic reconnection, a key plasma process that enables transfer of mass and energy into the near-Earth space environment. Reconnection leads to the triggering of magnetospheric storms, auroras, energetic particle precipitation and a host of other magnetospheric phenomena. Several works in the last decades have attempted to statistically quantify the amount of ionospheric plasma supplied to the magnetosphere, including the two key regions where magnetic reconnection occurs: the dayside magnetopause and the magnetotail. Recent in situ observations by the Magnetospheric Multiscale spacecraft and associated modeling have advanced our current understanding of how ionospheric ions alter the magnetic reconnection process, including its onset and efficiency. This article compiles the current understanding of the ionospheric plasma supply to the magnetosphere. It reviews both the quantification of these sources and their effects on the process of magnetic reconnection. It also provides a global description of how the ionospheric ion contribution modifies the way the solar wind couples to the Earth's magnetosphere and how these ions modify the global dynamics of the near-Earth space environment.Plain Language Summary Above the neutral atmosphere, space is filled with charged particles, which are tied to the Earth's magnetic field. The particles come from two sources, the solar wind and the Earth's upper atmosphere. Most of the solar wind particles are deflected by the Earth´s magnetic field, but some can penetrate into near-Earth space. The ionized layer of the upper atmosphere is continuously ejecting particles into space, which have low energies and are difficult to measure. We investigate the relative importance of the two charged particle sources for the dynamics of plasma processes in near-Earth space. In particular, we consider the effects of these sources in magnetic reconnection. Magnetic reconnection allows initially separated plasma regions to become magnetically connected and mix, and converts magnetic energy to kinetic energy of charged particles. Magnetic reconnection is the main driver of geomagnetic activity in the near-Earth space, and is responsible for the release of energy that drives a variety of space weather effects. We highlight the fact that plasma from the ionized upper atmosphere contributes a significant part of the density in the key regions where magnetic reconnection is at work, and that this contribution is larger when the geomagnetic activity is high. TOLEDO-RE...

Solar Wind—Magnetosphere Coupling During Radial Interplanetary Magnetic Field Conditions: Simultaneous Multi‐Point Observations

“…The eLLBL in Figure 4j cannot be distinguished at the time scale of the plot, please refer to Figure S7 in Supporting Information S1 of the supplemental material for a detailed observation of the eLLBL, which is not obvious for this event. The low energy electrons observed in Figure 4j after 17:49 UT are associated to cold ions of ionospheric origin (Figure 4j) and do not correspond to the eLLBL (e.g., Toledo-Redondo et al, 2021). We also search for jets in ion velocity (black lines in Figures 4c and 4h) of the order of the Alfvén velocity (listed in Table 3), which would indicate ongoing reconnection.…”

On the Presence and Thermalization of Cold Ions in the Exhaust of Antiparallel Symmetric Reconnection

“…Magnetic reconnection is a fundamental plasma process that converts energy stored in the magnetic fields to plasma energy by enabling the reconfiguration of the magnetic field topology. Cold plasma can be abundant in regions of magnetic reconnection, and impact the reconnection process in several ways (for a recent review, see Toledo-Redondo et al, 2021). Examples include, but are not limited to, mass loading (Fuselier et al, 2017;Dargent et al, 2020;Tenfjord et al, 2020), introduction of an extra cold ion diffusion region (Toledo-Redondo et al, 2016a;Divin et al, 2016), modifications to the Hall physics (Toledo-Redondo et al, 2015;André et al, 2016;Toledo-Redondo et al, 2018), and plasma heating (Toledo-Redondo et al, 2016b;Toledo-Redondo et al, 2017).…”

The Key Role of Cold Ionospheric Ions As a Source of Hot Magnetospheric Plasma and As a Driver of the Dynamics of Substorms and Storms

“…Both the dayside solar windmagnetosphere and nightside magnetotail reconnection regions become populated with ionospheric plasma. The ionospheric ions, both from the duskside plumes and detached regions that come off the plasmasphere and the warm plasma cloak bring particles to the nose of the magnetosphere and affect the reconnection process there (Fuselier et al, 2019), while high latitude outflow of the polar wind and polar cusp affects magnetotail reconnection (Toledo-Redondo et al, 2021). These initially polar wind ions are very difficult to measure in the lobes because of their low energies and densities and the effects of positive spacecraft potential, which means that they are often unseen.…”