Collisionless Magnetic Reconnection in an Asymmetric Oxygen Density Configuration

Kolstø, Håkon Midthun; Hesse, M.; Norgren, Cecilia; Tenfjord, P.; Spinnangr, Susanne Flø; Kwagala, Norah Kaggwa

doi:10.1029/2019gl085359

Cited by 16 publications

(14 citation statements)

References 22 publications

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“…They found that O + , as a consequence of being demagnetized, was ballistically accelerated, primarily by the Hall electric field. Simulations by Tenfjord et al (2019) and Kolstø et al (2020) show that for both symmetrically and asymmetrically distributed O + , the reconnection rate is significantly reduced, but not as much as predicted by mass-loading. The authors describe a mechanism where the O + population (and the accompanying electrons) acts as an energy sink on the system, altering the energy partitioning.…”

Section: Heavy Ions and Reconnection Ratementioning

confidence: 87%

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

Toledo‐Redondo

André

Aunai

et al. 2021

Reviews of Geophysics

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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...

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Section: Heavy Ions and Reconnection Ratementioning

confidence: 87%

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

Toledo‐Redondo

André

Aunai

et al. 2021

Reviews of Geophysics

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“…Beyond this, we speculate that asymmetric lobe filling can be expected to create asymmetric O + density conditions near the nightside reconnection site. Recent work by Kolstø et al (2020) using PIC simulations indicate that such conditions can cause asymmetries in the diffusion region and motion of the reconnection site.…”

Section: Discussionmentioning

confidence: 99%

A Case Study on the Origin of Near‐Earth Plasma

Glocer¹,

Welling

Chappell

et al. 2020

JGR Space Physics

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This study presents simulations of the coupled space environment during a geomagnetic storm that separates the different sources of near-Earth plasma. These simulations include separate fluids for solar wind and ionospheric protons, ionospheric oxygen, and the plasmasphere. Additionally, they include the effects of both a hot ring current population and a cold plasmaspheric population simultaneously for a geomagnetic storm. The modeled ring current population represents the solution of bounce-averaged kinetic solution; the core plasmaspheric model assumes a fixed temperature of 1 eV and constant pressure along the field line. We find that during the storm, ionospheric protons can be a major contributor to the plasmasheet and ring current and that ionospheric plasma can largely displace solar wind protons in much of the magnetosphere under certain conditions. Indeed, the ionospheric source of plasma cannot be ignored. Significant hemispheric asymmetry is found between the outflow calculated in the summer and winter hemispheres, consistent with past observations. That asymmetric outflow is found to lead to asymmetric filling of the lobes, with the northern (summer) lobe receiving more outflow that has a higher proportion of O + and the southern (winter) lobe receiving less outflow with a higher proportion of H +. We moreover find that the inclusion of the plasmasphere can have a system-wide impact. Specifically, when the plasmasphere drainage plume reaches the magnetopause, it can reduce the reconnection rate, suppress ionospheric outflow and change its composition, change the composition in the magnetosphere, and reduce the ring current intensity.

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“…Cassak and Shay (2007) proposed a MHD scaling law of the asymmetric magnetic reconnection rate R in steady state depending only on the inflowing plasma density n and magnetic field B values: (Zhang et al, 2016). As a MHD model, Cassak and Shay (2007) neglect all kinetic processes potentially impacting magnetic reconnection (Dargent et al, 2017;Hesse et al, 2013;Kolstø et al, 2020;Tenfjord et al, 2019). Finally, due to the steady state assumption, one can wonder if this model is still applicable in during variations of the external environment, such as during the impact of a plasmaspheric plume.…”

Section: Introductionmentioning

confidence: 99%

Simulation of plasmaspheric plume impact on dayside magnetic reconnection

Dargent

Aunai

Lavraud

et al. 2020

Preprint

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During periods of strong magnetic activity, cold dense plasma from the plasmasphere typically forms a plume extending toward the dayside magnetopause, eventually reaching it. In this work, we present a large-scale two-dimensional fully kinetic particle-in-cell simulation of a reconnecting magnetopause hit by a propagating plasmaspheric plume. The simulation is designed so that it undergoes four distinct phases: initial unsteady state, steady state prior to plume arrival at the magnetospause, plume interaction, and steady state once the plume is well engulfed in the reconnection site. We show the evolution of the magnetopause's dynamics subjected to the modification of the inflowing plasma. Our main result is that the change in the plasma temperature (cold protons in the plume) has no effects on the magnetic reconnection rate, which on average depends only on the inflowing magnetic field and total ion density, before, during, and after the impact.where the subscripts 1 and 2 refer to the two sides of the layer and ∕L is the aspect ratio of the diffusion region. This model proved to be quite accurate (Birn et al., 2008;Borovsky et al., 2008). However, the domain of validity of this model is limited. It only gives the local reconnection rate calculated with parameters near RESEARCH LETTER

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Collisionless Magnetic Reconnection in an Asymmetric Oxygen Density Configuration

Cited by 16 publications

References 22 publications

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

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

A Case Study on the Origin of Near‐Earth Plasma

Simulation of plasmaspheric plume impact on dayside magnetic reconnection

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