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Magnetic Reconnection: �The key to Understanding Earth’s Space Environment

Yi Qi, M. Hasan Barbhuiya, Chen Shi, John Dorelli, Katy Goodrich, Krishna Khanal

GEM new FG introduction

Jun 24, 2025 �Des Moines, IA

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FG Organizers

Yi Qi

University of Colorado, LASP

Chen Shi

UCLA

M. Hasan Barbhuiya�West Virginia University

Katherine Goodrich

West Virginia University�

John Dorelli

NASA

Krishna Khanal

University of Alabama in Huntsville

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FG Organizers

Yi Qi

University of Colorado, LASP

Chen Shi

UCLA

M. Hasan Barbhuiya�West Virginia University

Katherine Goodrich

West Virginia University�

John Dorelli

NASA

Krishna Khanal

University of Alabama in Huntsville

In-situ observations,

MMS

MHD theory and simulations, dynamics of solar wind

Theory and kinetic simulations,

Energy Conversion processes

Global modeling of Earth’s magnetosphere

Electric field instrument calibration and data analysis, MMS, TRACERS Co-I

In-situ and ionospheric observations,

spatiotemporal variability of reconnection

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FG Organizers

Yi Qi

University of Colorado, LASP

Chen Shi

UCLA

M. Hasan Barbhuiya�West Virginia University

Katherine Goodrich

West Virginia University�

John Dorelli

NASA

Krishna Khanal

University of Alabama in Huntsville

In-situ observations,

MMS

MHD theory and simulations, dynamics of solar wind

Theory and kinetic simulations,

Energy Conversion processes

Global modeling of Earth’s magnetosphere

Electric field instrument calibration and data analysis, MMS, TRACERS Co-I

In-situ and ionospheric observations,

spatiotemporal variability of reconnection

We are looking for new student representative!

Contact Krishna for more info (kk0099@uah.edu)

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Background

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How does reconnection occur

Magnetic field annihilation

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B

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The frozen-in condition

One of the first concepts in plasma physics is that charged particles in a magnetic field orbit in a helical path.
With infinite conductivity, magnetic field and the plasma move together with each other.

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[Credit: Baumjohann and Treumann 1997]

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How does reconnection occur?

Magnetic field annihilation

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Classic reconnection picture

B

The violation of the frozen-in condition

Diffusion Region

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Evolving reconnection models – ideal MHD (with resistivity)

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[Ponti et al., 2020]

Sweet-Parker model

Petschek’s model

The energy conversion:

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Evolving reconnection models – Hall MHD

Consider collisionless plasma, i.e. 𝜼 = 0
Current arises from the separation between the ions and electrons

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[Burch et al., 2015]

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Evolving reconnection models – electron scale

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Hall MHD was a large step forward. However, electrons do not decouple via the Hall term.
And since energy conversion: �Hall MHD cannot account for magnetic energy conversion.
Consider physics at electron scale:

Electron pressure tensor

isotropic

gyrotropic

Non-gyrotropic

0

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Evolving reconnection models – electron scale

Hall MHD was a large step forward. However, electrons do not decouple via the Hall term.
And since energy conversion: �Hall MHD cannot account for magnetic energy conversion.
Consider physics at electron scale:

[Hesse et al., 2016]

[Burch et al., 2016]

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Evolving reconnection models – electron scale

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A number of advances came from PIC (Particle-In-Cell; kinetic) simulations:

Energy dissipation into electrons was quantified.

[L. C. Lee & K. H. Lee, 2020]

[Hesse et al., 2016]

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Topic descriptions:

While we are learning more, we discover more open questions

1. How to connect the kinetic and global-scale magnetic reconnection?

Moore et al., 2012

Kivelson and Russell , 1995

The scale of magnetic reconnection is global (e.g. Dungey Cycle), but diffusion regions at the center of reconnection are much smaller, with an electron diffusion region embedded within a larger ion diffusion region.
Over the last decade, MMS has provided the community with a tremendous opportunity to explore magnetic reconnection via multipoint measurements of species-specific 𝑱 ∙ 𝑬, electromagnetic energy and plasma kinetic energy at kinetic scales. The Tandem Reconnection and Cusp Reconnaissance Satellites (TRACERS), to be launched in 2025, aims to observe the spatiotemporal variance of magnetic reconnection at a larger scale.
We will invite the community to advocate for and make use of data from both MMS and TRACERS, as well as other satellites within the HSO in order to probe the upstream solar wind, magnetopause and magnetotail reconnection, and low-altitude cusp responses at the same time, thus providing a truly global view of the magnetopause topology under a wide range of solar wind conditions.

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Topic descriptions:

1. How to connect the kinetic and global-scale magnetic reconnection?

While we are learning more, we discover more open questions

In-situ Plasma Measurements

Two Identical Spacecraft

LEO around the Cusp

Launches 2025

Ground-based Observations

SuperDARN & EISCAT

Credit: superDARN

Y. Lin et al., 2021

Global Hybrid Simulations

ANGIE3D-CIMI

Local LEO observations can provide us with global information about the structure and dynamics of reconnection
---------
The scale of magnetic reconnection is global (e.g. Dungey Cycle), but diffusion regions at the center of reconnection are much smaller, with an electron diffusion region embedded within a larger ion diffusion region.
Over the last decade, MMS has provided the community with a tremendous opportunity to explore magnetic reconnection via multipoint measurements of species-specific 𝑱 ∙ 𝑬, electromagnetic energy and plasma kinetic energy at kinetic scales. The Tandem Reconnection and Cusp Reconnaissance Satellites (TRACERS), to be launched in 2025, aims to observe the spatiotemporal variance of magnetic reconnection at a larger scale.
We will invite the community to advocate for and make use of data from both MMS and TRACERS, as well as other satellites within the HSO in order to probe the upstream solar wind, magnetopause and magnetotail reconnection, and low-altitude cusp responses at the same time, thus providing a truly global view of the magnetopause topology under a wide range of solar wind conditions.

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Topic descriptions:

While we are learning more, we discover more open questions

Local connection between EM forces and particle energy densities

EM fields affect bulk kinetic energy density directly but not internal energy density that is related to temperature

??

Partial conversion through pressure-strain interaction

Global connection between EM forces and particle energies

Neglecting fluxes at boundaries

EM fields affect bulk kinetic energy directly and then through pressure-strain interaction affect internal energy

Yang et al., 2017

The scale of magnetic reconnection is global (e.g. Dungey Cycle), but diffusion regions at the center of reconnection are much smaller, with an electron diffusion region embedded within a larger ion diffusion region.
Over the last decade, MMS has provided the community with a tremendous opportunity to explore magnetic reconnection via multipoint measurements of species-specific 𝑱 ∙ 𝑬, electromagnetic energy and plasma kinetic energy at kinetic scales. The Tandem Reconnection and Cusp Reconnaissance Satellites (TRACERS), to be launched in 2025, aims to observe the spatiotemporal variance of magnetic reconnection at a larger scale.
We will invite the community to advocate for and make use of data from both MMS and TRACERS, as well as other satellites within the HSO in order to probe the upstream solar wind, magnetopause and magnetotail reconnection, and low-altitude cusp responses at the same time, thus providing a truly global view of the magnetopause topology under a wide range of solar wind conditions.

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Topic descriptions:

2. What is the magnetic reconnection like in more realistic three-dimensional space?

While we are learning more, we discover more open questions

Yamada et al., 1997

Pathak et al., 2022

Arencibia et al., 2021

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Topic descriptions:

While we are learning more, we discover more open questions

2. What is the magnetic reconnection like in more realistic three-dimensional space?

Lu et al., 2022

Phan et al., 2018

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Topic descriptions:

While we are learning more, we discover more open questions

3. What are the temporal variations of magnetic reconnection?

how can we develop more reliable observational tools to distinguish the different phases of reconnection during satellite crossings?

Spacecraft measurements are line plots:�snapshots for time-varying 3D systems!

Reconnection typically evolves through distinct phases. Including a slow linearly growing phase, an explosive phase where the reconnection rate increases rapidly, and steady phase where the reconnection rate saturates around ~ 0.1in normalized units as found in simulations and observations.
It remains challenging to determine what phase of reconnection is being observed during in-situ satellite measurements, unlike in 2D numerical simulations.

Torbert et al., 2018

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Topic descriptions:

While we are learning more, we discover more open questions

3. What are the temporal variations of magnetic reconnection?

Payne et al. 2024 proposed following the evolution of the non-ideal reconnection electric field and the divergence of the Poynting flux to identify growth phase

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Topic descriptions:

While we are learning more, we discover more open questions

3. What are the temporal variations of magnetic reconnection?

Recent work by Genestreti et al. 2024a,b, utilized MMS to possibly detect reconnection onset, marked by rapid thinning of the cross-tail current sheet and the subsequent onset of the electron tearing mode

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Relation to current FGs

Multiscale Dayside Transients and their Effect on Earth's Magnetosphere (MDT) (2025-2029)

Understanding the causes of geomagnetic disturbances in geospace for hazard analysis on geomagnetically induced currents

(2022-2026)

Mesoscale drivers of the nightside transition region: ionospheric and magnetotail evaluations (MESO)

(2022-2026)

Magnetospheric Sources of Particle Precipitation and Their Role on Electrodynamic Coupling of Magnetosphere-Ionosphere-Thermosphere System (2022-2026)

Comparative Planetary Magnetospheric Processes (COMP)

(2023-2027)

Kinetic Plasma Processes in the Magnetotail during Substorm Dynamics (KiTS)

(2024-2028)

Magnetic reconnetion: The key to Understanding Earth’s Space Environment

The Impact of the Cold Plasma in Magnetospheric Physics (2020-2025)�One of the goals of this FG is: “bring together theoretical and observational knowledge to assess the most important impacts associated with the cold plasma in the magnetospheric system”. Reconnection is a crucial process that impacts the whole magnetospheric system. The mass loading effect due to the cold ions impacts the dayside reconnection. We can collaborate and better understand this process.

Understanding the causes of geomagnetic disturbances in geospace for hazard analysis on geomagnetically induced currents (2022-2026)�As mentioned on the FG’s wiki page, the common sources and driving mechanisms of GMDs are associated with large-scale geomagnetic activity, including storms and substorms. Since magnetic reconnection is the dominant driver of geomagnetic disturbances, its better understanding will also shed light on the analysis of GMDs and GICs.

Mesoscale drivers of the nightside transition region: ionospheric and magnetotail evaluations (MESO) (2022-2026): �Plasma dynamics in the Nightside Transition Region (NTR) is essential to the M-I coupling. As a major driver for the geomagnetic disturbances, magnetic reconnections are directly related to bursty bulk flows, dipolarization fronts, etc., that feed into the NTR.

Magnetospheric Sources of Particle Precipitation and Their Role on Electrodynamic Coupling of Magnetosphere-Ionosphere-Thermosphere System (2022-2026): �Magnetic reconnection relates to this FG as it is a fundamental process that leads to enormous dayside and nightside disturbances, flux convections, and wave generations, which can cause particle precipitation.

Comparative Planetary Magnetospheric Processes (2023-2027): �The key comparative topics for the COMP FG include magnetotail dynamics and M-I coupling mechanisms. Magnetic reconnection in the planetary magnetosphere can be essential in particle acceleration, heating, and precipitation. Knowledge gained about reconnection on Earth is crucial for comparative studies.

Kinetic Plasma Processes in the Magnetotail during Substorm Dynamics (2024-2028): �During the substorm expansion phase, reconnection releases the magnetic energy stored in the magnetotail during the previous substorm growth phase. The kinetic plasma processes in the magnetotail during the substorm is closely related to magnetic reconnection.

———

Note:

Depending on where the ions enter the exhaust, and how long time they have spent there, they are accelerated to different energies. (Norgren et al., 2020)

———

The Impact of the Cold Plasma in Magnetospheric Physics (2020-2025)�One of the goals of this FG is: “bring together theoretical and observational knowledge to assess the most important impacts associated with the cold plasma in the magnetospheric system”. Reconnection is a crucial process that impacts the whole magnetospheric system. The mass loading effect due to the cold ions impacts the dayside reconnection. We can collaborate and better understand this process.

Understanding the causes of geomagnetic disturbances in geospace for hazard analysis on geomagnetically induced currents (2022-2026)
As mentioned on the FG’s wiki page, the common sources and driving mechanisms of GMDs are associated with large-scale geomagnetic activity, including storms and substorms. Since magnetic reconnection is the dominant driver of geomagnetic disturbances, its better understanding will also shed light on the analysis of GMDs and GICs.

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Goals and deliverables:

We aim to deepen our understanding in magnetic reconnection, and to contribute to the community

1. The multiscale coupling between kinetic and global processes, particularly the impact of small-scale dynamics on large-scale structures.

2. The three-dimensional nature of magnetic reconnection, including the spreading of the x-line and the interplay between magnetic reconnection and turbulence.

3. The temporal evolution of magnetic reconnection, and the development of reliable observational tools for distinguishing various phases of reconnection.

Science deliverables:

Multiscale Coupling Analysis: Provide new insights into the coupling between small kinetic and global scales in reconnection, using conjunction data from MMS, TRACERS, and other satellites to investigate how small-scale processes impact larger-scale magnetic topologies.
3D Reconnection Characterization: Develop a detailed understanding of x-line spreading, and �how reconnection interacts with and generates turbulence, by quantifying the impact of reconnection has in turbulent plasma environments on particle energization and energy dissipation.
Reconnection Phases Identification: Refine and develop new methods to observationally identify the distinct phases of magnetic reconnection, improving our ability to detect these phases using in-situ satellite data under varying solar wind conditions.
Energy Conversion Formalism: Advance the theoretical framework for understanding energy conversion in reconnection, in particular focusing on the conversion between internal energy of the particles and electromagnetic energy of the fields.

Primary Science Goal: �To address fundamental questions about magnetic reconnection by investigating:

https://gem.epss.ucla.edu/mediawiki/index.php/FG:_Magnetic_Reconnection:_The_Key_to_Understanding_Earth's_Space_Environment

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Goals and deliverables:

We aim to deepen our understanding in magnetic reconnection, and to contribute to the community

Primary Community Goal:

To foster collaborative research and interdisciplinary dialogue within the space physics and plasma physics communities, aiming to advance understanding of magnetic reconnection.

The focus group will promote community-driven efforts to interpret in-situ observations, support the development of advanced observational tools, and encourage a global understanding of reconnection dynamics in planetary magnetospheres through joint sessions with other focus groups.

Community deliverables:

Collaborative Data Analysis Initiatives: Establish a framework for joint analysis of data from missions like MMS, TRACERS, and other HSO satellites, facilitating conjunction studies and multiscale investigations, and thus providing a global view of reconnection events under varying solar wind conditions.
Shared Tools and Methodologies: Develop and share observational and analytical tools that can help the community reliably identify different phases of reconnection from satellite data, using various scalar quantities and new diagnostics.
Educational and Outreach Materials: Create educational resources that facilitate a broader understanding of magnetic reconnection’s impact on heliophysics and planetary magnetospheres, contributing to the training of the next generation of researchers.

https://gem.epss.ucla.edu/mediawiki/index.php/FG:_Magnetic_Reconnection:_The_Key_to_Understanding_Earth's_Space_Environment

Community deliverables:

Collaborative Data Analysis Initiatives: Establish a framework for joint analysis of data from missions like MMS, TRACERS, and other HSO satellites, facilitating conjunction studies and multiscale investigations, and thus providing a global view of reconnection events under varying solar wind conditions.
Shared Tools and Methodologies: Develop and share observational and analytical tools that can help the community reliably identify different phases of reconnection from satellite data, using various scalar quantities and new diagnostics.
Educational and Outreach Materials: Create educational resources that facilitate a broader understanding of magnetic reconnection’s impact on heliophysics and planetary magnetospheres, contributing to the training of the next generation of researchers.

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Expected activities

Initial workshop-style meeting focusing on establishing collaboration between missions and individual groups. We will identify key observational challenges in multiscale coupling, the 3D nature of reconnection, the interplay between reconnection and turbulence, reconnection phases, and energy conversion mechanisms in reconnection, setting the stage for workshops in future years. �

Year 1

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Expected activities

Initial workshop-style meeting focusing on establishing collaboration between missions and individual groups. We will identify key observational challenges in multiscale coupling, the 3D nature of reconnection, the interplay between reconnection and turbulence, reconnection phases, and energy conversion mechanisms in reconnection, setting the stage for workshops in future years.

A review highlighting the findings in the past year. We will solicit state-of-the-art methods and technologies to tackle the previously identified challenges, and decide on the list of events (magnetopause and magnetotail) for different groups to work together. Comparative analysis of different reconnection regions with a focus on the temporal phases of reconnection and the influence of EM forces and particle energy.

Year 1

Year 2

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Expected activities

Initial workshop-style meeting focusing on establishing collaboration between missions and individual groups. We will identify key observational challenges in multiscale coupling, the 3D nature of reconnection, the interplay between reconnection and turbulence, reconnection phases, and energy conversion mechanisms in reconnection, setting the stage for workshops in future years.

A review highlighting the findings in the past year. We will solicit state-of-the-art methods and technologies to tackle the previously identified challenges, and decide on the list of events (magnetopause and magnetotail) for different groups to work together. Comparative analysis of different reconnection regions with a focus on the temporal phases of reconnection and the influence of EM forces and particle energy.

A review highlighting the findings in the past year. We will investigate the 3D aspects of reconnection, focusing on the x-line spreading and the interplay between reconnection and turbulence through joint simulation-observation workshops.

Year 1

Year 2

Year 3

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Expected activities

Initial workshop-style meeting focusing on establishing collaboration between missions and individual groups. We will identify key observational challenges in multiscale coupling, the 3D nature of reconnection, the interplay between reconnection and turbulence, reconnection phases, and energy conversion mechanisms in reconnection, setting the stage for workshops in future years.

A review highlighting the findings in the past year. We will solicit state-of-the-art methods and technologies to tackle the previously identified challenges, and decide on the list of events (magnetopause and magnetotail) for different groups to work together. Comparative analysis of different reconnection regions with a focus on the temporal phases of reconnection and the influence of EM forces and particle energy.

A review highlighting the findings in the past year. We will investigate the 3D aspects of reconnection, focusing on the x-line spreading and the interplay between reconnection and turbulence through joint simulation-observation workshops.

A review highlighting findings from the past 3 years and we will present our current understandings and deficiencies/gaps. We will isolate the challenges and possible remedies.

Year 1

Year 2

Year 3

Year 4

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What are we having this year

Joint sessions with KiTS, MESO, and CEDAR (Monday PM, Room A)

Scene-setting talks by four panelists:�Larry Lyons, Jesper Gjerloev, Tuija Pulkkinen, Mikhail Sitnov
Short presentations with open discussions

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What are the onset mechanisms that triggers the explosive expansion phase?

2. What are the role of preconditioning during the growth phase that determine the properties of the pre-onset magnetotail current sheet

Substorms are one of the main processes in which Earth’s magnetosphere-ionosphere system responds to driving from the solar wind. During the substorm growth phase energy is stored in the magnetotail lobes before releasing during the expansion phase. However, the onset mechanism that triggers the explosive expansion phase is not well understood. While magnetic reconnection is known to play a role in the explosive release of energy, there may be a separate mechanism for onset (e.g. current disruption or ballooning/interchange instability). Other questions include the role of preconditioning during the growth phase that determine the properties of the pre-onset magnetotail current sheet. To complicate matters further, observations of the aurora mapped to the magnetotail can have large errors in their location.

In this joint session we hope to bring together researchers from both GEM and CEDAR communities to share their expertise on this topic. Linking dynamics between the ionosphere and magnetotail is a key part of understanding the magnetospheric system-of-systems response to solar wind driving. We will invite four panelists to give presentations to set the stage for a discussion on the topic of substorm onset, the mechanisms involved, their location, and the importance of the pre-onset magnetotail configuration.

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What are we having this year

Joint sessions with MDT (Tuesday AM, room 309-310)

This session will bring together the RX and MDT communities to explore how transient phenomena—such as foreshock transients, FTEs, high-speed jets, and shock-induced structures—initiate, drive, or modify magnetic reconnection across the dayside magnetosphere and upstream regions. Topics of interest include but not limit to:

Reconnection at the magnetopause driven by dayside transients
Reconnection in the solar wind, foreshock, shock, and magnetosheath
Observational and modeling studies linking reconnection and transient dynamics
Multiscale coupling across spatial and temporal domains

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What are we having this year

Stand-alone session 1 (Wed PM, room 307) �Reconnection Physics and Turbulence�
This session focuses on the fundamental physics of magnetic reconnection and turbulence, including:

Energy conversion mechanisms in collisionless plasmas
The coupling between reconnection and plasma turbulence
Novel simulation or data analysis techniques that advance reconnection research

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What are we having this year

Stand-alone session 1 (Wed PM, room 307) �Reconnection Physics and Turbulence�

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[University of Iowa/Andy Kale]

TRACERS updates and modeling

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What are we having this year

Stand-alone session 2 (Thur AM, room 307) �Electron-Only Reconnection�
This session will explore electron-only reconnection in collisionless space plasmas, including regimes where ions do not participate due to spatial or temporal constraints. Topics include:

Case studies of electron-only reconnection
Simulations distinguishing spatial vs. temporal constraints
Energy conversion diagnostics at electron scales
Links between electron-only reconnection and turbulence
Terminology clarification and framework-building for future studies
Related ion- and electron-scale/ physics

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What are we having this year

Stand-alone session 3 (Thur PM, room 307) �A Hands-on Tutorial on Reconnection Simulations�

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This tutorial session is designed for students and early-career researchers interested in reconnection modeling. Experts will share practical guidance on simulation setup, magnetic field and plasma configurations, and physical interpretation. This session will be a valuable introduction to reconnection simulations.

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Posters

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82	Alexandra Abova-Volkova	Particle-in-Cell Study of Ion and Electron Heating in Asymmetric Magnetic Reconnection
83	Audrey Robison	Magnetic Ground Based Signatures of Poleward Moving Auroral Forms
84	Carlos Agustin Giai	The Suppression of the Outflow Speed in High Œ≤, Strong Guide Field Reconnection
85	Fekireselassie Beyene	Multiple VNERX events observed during a magnetic storm's main phase
86	George B. Hospodarsky	The Tandem Reconnection and Cusp Electrodynamics Reconnaissance Satellites (TRACERS) Mission
87	Hanieh Karimi	Energy Conversion in Turbulence Using Kinetic and Relative Entropy
88	Jonathan Ng	3D electron and ion-scale reconnection at the quasi-parallel shock
89	Krishna Khanal	Transient suppression of magnetopause reconnection in the presence of dense plasmaspheric plume
90	Matti Ala-Lahti	Determining the Magnetospheric Response to Solar Wind Magnetic Field Fluctuations
91	Nitya Agarwala	Investigating Electron Energizations in Ion-scale Flux Rope Chain in Turbulent Plasma

84	(Matheus) Henry Przygocki	Dayside Local Reconnection Rates in global hybrid simulation: Impact of IMF, Probe Methodology, and Resultant Reconnection Configuration
85	Amy Rewoldt	Reconnection potential via Null-based Extraction and Utilization System (RECONEXUS)
86	Fekireselassie Beyene	Earthward-tailward asymmetry of plasma temperature in reconnection outflow in Earth's magnetotail
87	M. Hasan Barbhuiya	Identifying the Growth Phase of Magnetic Reconnection Using Pressure‚ÄêStrain Interaction
88	Nolan Tribu	Quantifying Energy Flux across the Dayside Magnetopause using MMS Data
89	Oshina	Kelvin Helmholtz Instability in MMS observations and MAGE-MHD modelling
90	Robert Strangeway	The TRACERS Fluxgate Magnetometer (MAG) Instrument
91	Rushikesh Patil	Power Dissipation in Electron-Scale Magnetic holes
92	Talha Arshad	Exploring the onset of reconnection during substorms using AMR-PIC
93	XINMIN Li	Observation of a Knotted Electron Diffusion Region in Terrestrial Magnetotail Reconnection

Tue

Wed

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Join us!

Joint sessions with KiTS, MESO, and CEDAR�
Joint session with MDT �
Stand-alone session 1: �Reconnection Physics and Turbulence

Stand-alone session 2: �Electron-Only Reconnection�
Stand-alone session 3:�A Tutorial on Reconnection Simulations�

Monday PM, Room A

Tuesday AM, room 309-310

Wed PM, room 307

Thur AM, room 307

Thur PM, room 307

And posters :-)

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Backup slides

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Relation to current FGs

Reconnection are closely related to the topics studied by the other FGs

The Impact of the Cold Plasma in Magnetospheric Physics (2020-2025)�One of the goals of this FG is: “bring together theoretical and observational knowledge to assess the most important impacts associated with the cold plasma in the magnetospheric system”. Reconnection is a crucial process that impacts the whole magnetospheric system. The mass loading effect due to the cold ions impacts the dayside reconnection. We can collaborate and better understand this process.
Understanding the causes of geomagnetic disturbances in geospace for hazard analysis on geomagnetically induced currents (2022-2026)�As mentioned on the FG’s wiki page, the common sources and driving mechanisms of GMDs are associated with large-scale geomagnetic activity, including storms and substorms. Since magnetic reconnection is the dominant driver of geomagnetic disturbances, its better understanding will also shed light on the analysis of GMDs and GICs.

39 of 43

Relation to current FGs

Reconnection are closely related to the topics studied by the other FGs

Mesoscale drivers of the nightside transition region: ionospheric and magnetotail evaluations (MESO) (2022-2026): �Plasma dynamics in the Nightside Transition Region (NTR) is essential to the M-I coupling. As a major driver for the geomagnetic disturbances, magnetic reconnections are directly related to bursty bulk flows, dipolarization fronts, etc., that feed into the NTR.
Magnetospheric Sources of Particle Precipitation and Their Role on Electrodynamic Coupling of Magnetosphere-Ionosphere-Thermosphere System (2022-2026): �Magnetic reconnection relates to this FG as it is a fundamental process that leads to enormous dayside and nightside disturbances, flux convections, and wave generations, which can cause particle precipitation.

40 of 43

Relation to current FGs

Reconnection are closely related to the topics studied by the other FGs

Comparative Planetary Magnetospheric Processes (2023-2027): �The key comparative topics for the COMP FG include magnetotail dynamics and M-I coupling mechanisms. Magnetic reconnection in the planetary magnetosphere can be essential in particle acceleration, heating, and precipitation. Knowledge gained about reconnection on Earth is crucial for comparative studies.
Kinetic Plasma Processes in the Magnetotail during Substorm Dynamics (2024-2028): �During the substorm expansion phase, reconnection releases the magnetic energy stored in the magnetotail during the previous substorm growth phase. The kinetic plasma processes in the magnetotail during the substorm is closely related to magnetic reconnection.

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Topic descriptions:

While we are learning more, we discover more open questions

Inflow

Outflow

Diffusion region

Spacecraft Trajectory

Single/Multi-spacecraft measurements are line plots:1D data for 3D systems!

Research on magnetotail reconnection onset has largely focused on electron dynamics via analysis of electron distribution function analysis (e.g., Spinnangr et al., 2022)
Recent work by Genestreti et al. 2024a,b, utilized MMS to possibly detect reconnection onset, marked by rapid thinning of the cross-tail current sheet and the subsequent onset of the electron tearing mode
Studies such as Hubbert et al. 2022 and Lu et al. 2022 have examined current and plasma sheet properties during reconnection onset
Payne et al. 2024 proposed following the evolution of the non-ideal reconnection electric field and the divergence of the Poynting flux to identify growth phase

We want a marker that can be applied to satellite observations, is preferably scalar and reference frame and coordinate system independent and has distinct signatures for the different stages of reconnection.

Pressure-strain interaction may be useful here (Barbhuiya & Cassak, 2022; Barbhuiya et al. submitted)

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Topic descriptions:

How to connect the kinetic and global-scale magnetic reconnection?

While we are learning more, we discover more open questions

Pressure-Strain Interaction

When decomposed, pressure-strain interaction leads to isolation of heating/cooling contributions from pure converging/diverging flow and flow shear (Cassak & Barbhuiya, 2022, PoP)

(Barbhuiya & Cassak, 2022; Barbhuiya et al. submitted)

The scale of magnetic reconnection is global (e.g. Dungey Cycle), but diffusion regions at the center of reconnection are much smaller, with an electron diffusion region embedded within a larger ion diffusion region.
Over the last decade, MMS has provided the community with a tremendous opportunity to explore magnetic reconnection via multipoint measurements of species-specific 𝑱 ∙ 𝑬, electromagnetic energy and plasma kinetic energy at kinetic scales. The Tandem Reconnection and Cusp Reconnaissance Satellites (TRACERS), to be launched in 2025, aims to observe the spatiotemporal variance of magnetic reconnection at a larger scale.
We will invite the community to advocate for and make use of data from both MMS and TRACERS, as well as other satellites within the HSO in order to probe the upstream solar wind, magnetopause and magnetotail reconnection, and low-altitude cusp responses at the same time, thus providing a truly global view of the magnetopause topology under a wide range of solar wind conditions.

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