FG: Magnetic Reconnection in the Age of the Heliophysics System Observatory

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Contents


Chairs

Rick Wilder (frederick.wilder@lasp.colorado.edu)
Shan Wang (swang90@umd.edu)
Anton Artemyev (aartemyev@igpp.ucla.edu)
Mike Shay (shay@udel.edu)

2018 Workshop Agenda

We are pleased to announce the first GEM Summer Workshop sessions for this focus group.

We will have three sessions, one of which is joint with the Dayside Kinetics focus group.

Tuesday 19 June 2018, 10:30 AM - 12:00 PM: Local Physics of Magnetic Reconnection

This session focuses on the local physics of magnetic reconnection. This includes understanding energy conversion on the electron and ion scales, as well as understanding the overall kinetic physics on these scales. The relationship between magnetic reconeciton and turbulence are also covered. Talks are below.

10:30-10:35, Rick Wilder, introduction and opening remarks

1. 10:35 – 10:45, Blake Alastair Wetherton, “Equations of state applied to MMS data”
2. 10:45 – 10:55, Misha Sitnov, “New kinetic dissipation parameters”
3. 10:55-11:05, Tetsuo Motoba, “Calculation of kinetic dissipation using MMS data”
4. 11:05-11:15, Rick Wilder, “Parallel electric fields and dissipation in the outer electron diffusion region.”
5. 11:15-11:25, Prayash Sharma Pyakurel, “Electron-only reconnection”
6. 11:25-11:35, Haoming Liang, “Boltzmann entropy in PIC simulations”
7. 11:35-11:45, Kyunghwan Dogko, "Upper hybrid waves near the EDR"

11:45 – 12:00 – Open discussion, walk-on presentations.

Wednesday 20 June 2018, 10:30 AM - 12:00 PM: Global Consequences of Magnetic Reconnection

This session focuses on the global drivers and consequences on magnetic reconnection. Talks focused on reconnection physics specific to the magnetotail are also welcome in this session.

1. 10:30-10:40, Chih-Ping Wang, “Distant tail plasma flows originated from magnetic reconnection.”
2. 10:40-10:50, Anton Artemyev, “MMS/Artemis conjugate observations of middle-tail reconnection.”
3. 10:50-11:00, Andrei Runov, “Probing electron ejecta in the near tail and at lunar distances.”
4. 11:00-11:10, Chris Bard, “GPU-Accelerated global Hall MHD simulations.”
5. 11:10-11:20, Chris Mouikis, "The role of O+ on local and global changes during reconnection in the magnetotail"
6. 11:20-11:30, Joo Hwang, “Magnetotail reconnection with a guide field following the flapping motion of the magnetotail current sheet”
7. 11:30-11:40, Joo Hwang, "MMS observations of a flux rope in the magnetotail."

11:40-12:00 – Open discussion, walk-on presentations.

Wednesday 20 June 2018, 3:30 PM - 5:00 PM: Joint With Dayside Kinetic Processes Focus Group

This session is joint with the Dayside Kinetic Processes focus group, and therefore focuses on magnetic reconnection that is specifically relevant to the dayside magnetopause, magnetosheath or bow shock.

1. 3:30-3:40, Brian Walsh, “Maximum reconnection spreading speed at the dayside magnetopause.”
2. 3:40-3:50, Mike Shay, “Heating due to magnetic reconnection occurring in turbulence.”
3. 3:50-4:00, Sarah Vines, “Comparing dayside reconnection with inferred system measurements.”
4. 4:00-4:10, Allison Jaynes, “Whistlers and energetic electrons in the LLBL during reconnection events.”
5. 4:10-4:20, Jason Shuster, “Thin magnetosheath current sheet observations: resolving vlasov equations with MMS”
6. 4:20-4:30, Hyunju Connor, “Modeling of dayside magnetic reconnection and magnetopause movement.”
7. 4:30-4:40, Ari Le, "3D PIC simulations of magnetopause reconnection."

4:40-5:00 – Open discussion, walk-on presentations.

Archive: Original Proposal

Abstract

Magnetic reconnection is a fundamental plasma process that is important to the dynamics of the magnetospheric system. This process can impact dynamics studied by many of the GEM focus groups, however, the focus group specifically to study magnetic reconnection ended in 2017. We propose a new focus group that will study the local physics of magnetic reconnection, especially with regards to new discoveries by the Magnetospheric Multiscale (MMS) mission, and then study how these local physics impact the broader magnetospheric system as a whole. The proposed focus group is timely because of new and forthcoming discoveries by MMS and a unique constellation of spacecraft providing the global context for local MMS measurements, as well as enhanced modeling capabilities that have been developed over the past several years. Because reconnection has applications to many geospace phenomena, we anticipate many opportunities to collaborate with other focus groups. The proposed focus group will last for five years, and we expect important results relevant to the goals of GEM.

Topic Description

Magnetic reconnection is a fundamental process in plasma physics that changes the topological configuration of a magnetic field, and converts stored magnetic energy into kinetic energy and heat. It is an important driver of magnetospheric activity. Two important regions of study include the dayside magnetopause and the magnetospheric tail. At the dayside, the interplanetary magnetic field (IMF) frozen into the solar wind bulk flow can reconnect with the geomagnetic field, which drives large-scale plasma convection in the magnetosphere and ionosphere. In the geomagnetic tail, lobe magnetic field lines reconnect and release stored magnetic energy, which drives activity in the inner magnetosphere as well as the auroral ionosphere. Magnetic reconnection has also been observed at high latitudes during non-southward IMF, and within Kelvin-Helmholtz vortices on the magnetospheric flanks. It is therefore highly important to understand and model this fundamental process in order to model geospace as a whole. The proposed focus group will investigate magnetic reconnection in the Earth’s magnetosphere, with special focus on the synergy of increased modeling and observational capabilities that have only become available in the past few years, and were only beginning to be included in discussions in the magnetic reconnection focus group that ends this year (2017). The broad goals of the focus group are to understand (1) The role of turbulence in magnetic reconnection, (2) how reconnection behaves when expanded beyond 2-D laminar models, (3) where the energy dissipation in reconnection occurs, and (4) how local physics of magnetic reconnection depends on and determine the global global plasma and magnetic field configurations. We anticipate having strong ties with other focus groups that study phenomena closely associated with magnetic reconnection.

Timeliness of the Focus Group

In the past few years, there have been increased modeling and observational capabilities. New models include global simulations that are merged with kinetic simulations near reconnection regions and enhanced PIC simulation capabilities. New observational capabilities include the expanded Heliophysics System Observatory (HSO), made up of a variety of missions (THEMIS/ARTEMIS, MMS, the Van Allen Probes, etc) as well as expanded coverage by ground and ionospheric instrumentation. This allows global study of the solar wind-magnetosphere-ionosphere system for individual events and provides detailed information for numerical simulations of realistic plasma systems. Additionally, the MMS mission, launched in 2015, has provided new insights on the local and kinetic scale physics of magnetic reconnection, with the tail season taking place after the previous focus group ended. The implications of these results have not been adequately studied in the context of the geospace system as a whole. The proposed focus group will foster interaction between observations by the HSO and both global and kinetic simulations. While this began with the previous reconnection focus group, these new capabilities have not been used yet to their fullest extent when studying magnetic reconnection and its impact on the overall magnetosphere system.

Fit - Relation to Existing GEM Focus Groups

1. Geospace System Science: One of the goals of the proposed focused group is to reconcile the local vs. global observations and understanding of magnetic reconnection. This can have an impact on magnetospheric properties such as the cross polar cap potential, ionospheric field-aligned currents, auroral energy input, and the location/position of the auroral oval and polar cap boundary. Therefore, there are many opportunities to overlap with this focus group. This group will end the first year of the proposed focus group, so we would have to organize a joint session early.
2. Tail Environment and Dynamics at Lunar Distances: Depending on geomagnetic conditions, magnetic reconnection can occur at various positions along the magnetotail, including at lunar distances. Therefore, observations by spacecraft such as ARTEMIS are important to compare simulations of magnetic reconnection with observations. Moreover, observations in the distant magnetotail provide important information about tail configuration before and after near-Earth reconnection.
3. Modeling Methods and Validations: Being able to model and predict magnetic reconnection, as well as the insertion of kinetic models of magnetic reconnection in global simulations, are major challenges in the modeling of the geospace environment. Challenges to determine which models best capture both the local and global physics associated with magnetic reconnection are anticipated in the proposed focus group.
4. Dayside Kinetic Processes in Global Solar Wind-Magnetosphere Interactions: Magnetic reconnection is associated with many dayside kinetic processes, including waves and turbulence. Additionally, phenomena at the foreshock and in the magnetosheath can impact the structure and dynamics of the magnetopause, which in turn can impact magnetic reconnection at the magnetopause. There are therefore ample opportunities for joint sessions with this focus group.
5. Magnetotail Dipolarization and Its Effects on the Inner Magnetosphere: Dipolarization fronts and plasma flows in the magnetotail are driven by magnetic reconnection and transport some of the large scale energy associated with reconnection to the braking region near the inner magnetosphere, where this energy dissipates. Since one of the goals of the proposed focus group is to understand dissipation associated with reconnection, we expect that there will be opportunities to collaborate with the Magnetotail Dipolarization focus group.

Goals and Deliverables

1. What is the relationship between magnetic reconnection and turbulence? Recent observational studies and simulations have shown turbulence develop near the x-line during magnetic reconnection, which are thought to be driven by drift waves. This can have a significant impact on the energy budget of reconnection, and can generate large amplitude parallel electric fields. Additionally, simulations show as a turbulent cascade develops, intermittent current sheets can form, and one method by which these currents can dissipate is magnetic reconnection. This could be important to regions such as the turbulent magnetosheath, the flank magnetopause and the bursty bulk flow braking region where turbulence is known to occur. We will invite experts from the community on both the simulations and observations of turbulence to investigate these phenomena, as well as experts in magnetospheric system science to discuss the impact of local turbulent phenomena on the global system.
2. How does reconnection evolve beyond simple 2-D laminar models: waves, parallel electric fields, dissipation. In the past, magnetic reconnection was largely studied using 2-D pic simulations, often with laminar inflow conditions and an extremely simplified initial background plasma configuration. At present, the capabilities of PIC simulations have expanded to 3 dimensions, as well as increased processing power to have more realistic mass ratios, number of particles per cell, and initial plasma states. Community experts on 3-D pic simulations as well as observations from spacecraft such as MMS and THEMIS/ARTEMIS will be invited to participate and compare results and observations to better understand topics such as the development of parallel electric fields and their role in particle acceleration, role of initial magnetic field and plasma spatial distributions in magnetic reconnection, how dissipation changes in the presence of a guide magnetic field, and how various wave modes develop during both symmetric and asymmetric magnetic reconnection.
3. How is the energy associated with magnetic reconnection dissipated? This is a topic of special importance when it comes to magnetic reconnection and its relation to the rest of geospace. Recent observations by MMS have shown enhanced dissipation occurring in various places near the x-line, as well as in the exhausts. Additionally, turbulence can develop in the braking region of bursty bulk flows, which can also dissipate some of the stored energy in the exhaust flows. Deliverables of this study include comparisons of local simulations and observations at different points with respect to the x-line (e.g. exhausts, separatrix, electron and ion diffusion regions, neutral line, and stagnation point) to determine where dissipation is most likely to occur. Global simulations at high enough resolution to capture the cascade can inform the role of turbulence.
4. How can we reconcile our local and global understanding of magnetic reconnection? Magnetic reconnection and its effects on different scales are often observed and studied separately. For example, the reconnection electric fields observed at the dayside by MMS, when integrated along the dayside, would often lead to a cross-polar cap potential that is far too large for what is measured in the ionosphere. To reconcile this and other discrepancies between local and global observations, we will need to make use of the entire HSO, and we will therefore be inviting the entire community to participate in these challenges. We anticipate that new capabilities to merge local and global models will also help in investigating this. Other investigations will be local vs. global closure of field-aligned currents associated with magnetic reconnection, energy transport from the reconnection region by plasma flows and waves, as well as the dissipation of Poynting flux, and how fast reconnection and the magnetospheric system responds to changes of solar wind conditions.

Co-chairs

• Rick Wilder, University of Colorado, Frederick.wilder@lasp.colorado.edu (Expertise – reconnection at the dayside magnetopause, waves associated with magnetic reconnection, dayside magnetosphere-ionosphere system science).
• Shan Wang, University of Maryland, College Park (Expertise – analysis of local reconnection physics at the dayside magnetopause and magnetotail)
• Michael Shay, University of Delaware (Expertise – theory and simulations of magnetic reconnection and turbulence, kinetic simulations, MHD simulations)
• Anton Artemyev, University of California, Los Angeles (Expertise – magnetotail configuration and dynamics, particle acceleration in plasma flows, energy dissipation via wave-particle interaction)

Term of Focus Group

5 years

Research Area

Geospace Space System Modeling

Expected Activities, Session Topics and Challenges

There are several possible activities and session topics for the duration of the proposed focus group, and these could act as a general guide for the five-year term.

Year 1 – Workshop-style session on the unsolved issues in reconnection in the magnetosphere. Additionally, we can have a session on magnetic reconnection and turbulence, and we can compare the results with recent MMS observations, especially since in extended mission, reconnection in quasi-parallel magnetosheath turbulence is a goal.
Year 2 – We will focus on 3-D effects of magnetic reconnection. This was a goal of the previous focus group, however, more work should be done to compare the predictions by simulations with observations by MMS.
Year 3 – Energy budget and dissipation in magnetic reconnection – this can also provide an opportunity for a modeling challenge, whereby we investigate the locations where dissipation occurs.
Year 4 – Reconciling local and global observations of magnetic reconnection, Part 1. We will have two workshop-style sessions where we will invite people from multiple communities (space, ground, modeling, etc) to discuss the major issues in local versus global observations and models, as well as how we can reconcile these. We can also identify challenge events with adequate observations by the HSO that can be modeled by the community.
Year 5 – Reconciling local and global observations of magnetic reconnection, Part 2. We will encourage the community to present results from selected challenge events, including observations and simulations.

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