Kevin J. Genestreti

Southwest Research Institute - Earth Oceans and Space

A statistical characterization of the location and rate of occurrence of magnetic reconnection in the near-Earth magnetotail is performed by analyzing the set of ion diffusion region (DR) observations made by the Cluster and Geotail spacecraft during solar maximum and the declining phase. The occurrence rate is analyzed in terms of its dependence o...

We investigate the accuracy with which the reconnection electric field EM can be determined from in‐situ plasma data. We study the magnetotail electron diffusion region observed by NASA's Magnetospheric Multiscale (MMS) on 2017‐07‐11 at 22:34 UT and focus on the very large errors in EM that result from errors in an LMN boundary‐normal coordinate sy...

We compare case studies of Magnetospheric Multiscale (MMS)-observed magnetopause electron diffusion regions (EDRs) to determine how the rate of work done by the non-ideal electric field, J.E'=J.(E+vexB), and electron dynamics vary with magnetic shear angle. We provide an in-depth analysis of an MMS-observed EDR event with a guide field approximatel...

We identify the electron diffusion region (EDR) of a guide-field dayside reconnection site encountered by the Magnetospheric Multiscale (MMS) mission and estimate the terms in generalized Ohm's law that controlled energy conversion near the X-point. MMS crossed the moderate-shear (∼130∘) magnetopause southward of the exact X-point. MMS likely enter...

We analyze a magnetotail reconnection onset event on 3 July 2017 that was observed under otherwise quiescent magnetospheric conditions by a fortuitous conjunction of six space and ground‐based observatories. The study investigates the large‐scale coupling of the solar wind–magnetosphere system that precipitated the onset of the magnetotail reconnec...

We analyze the local dynamics of magnetotail reconnection onset using Magnetospheric Multiscale (MMS) data. In conjunction with MMS, the macroscopic dynamics of this event were captured by a number of other ground and space‐based observatories, as is reported in a companion paper. We find that the local dynamics of the onset were characterized by t...

An $LMN$ coordinate system for magnetic reconnection events is sometimes determined by defining $N$ as the direction of the gradient across the current sheet and $L$ as the direction of maximum variance of the magnetic field. The third direction, $M$, is often assumed to be the direction of zero gradient, and thus the orientation of the X line. But...

Reconnection electric fields and normalized reconnection rates were determined with the four Magnetospheric Multiscale (MMS) spacecraft for fourteen reconnection events on the day side of the Earth's magnetosphere. Half of the events occurred at the magnetopause and the other half in the magnetosheath. The reconnection rates were determined by meas...

The four Magnetospheric Multiscale spacecraft encountered a reconnection region in the Earth's magnetospheric tail on 11 July 2017. Previous publications have reported characteristics of the electron diffusion region, including its aspect ratio, the reconnection electric field, plasma wave generation from electron beams in its vicinity, and energet...

Plain Language Summary Measuring spatial and temporal variations of space plasmas usually requires choosing between the following two approaches: (a) measure how the quantity of interest changes in time as the plasma flows past a single spacecraft, or (b) compare measurements of the quantity gathered from multiple, spatially separated spacecraft. T...

NASA's Magnetospheric Multiscale (MMS) mission is a four-spacecraft formation of Earth orbiting satellites that have been providing unparalleled measurements of the local kinetic-scale plasma dynamics in near-Earth space for the past 8 years. The spacecraft carry a full complement of space plasma instrumentation capable of measuring the 3D electrom...

Reconnection in the magnetotail occurs along so‐called X‐lines, where magnetic field lines tear and detach from plasma on microscopic spatial scales (comparable to particle gyroradii). In 2017–2020, the Magnetospheric MultiScale (MMS) mission detected X‐lines in the magnetotail enabling their investigation on local scales. However, the global struc...

In the Earth's magnetosphere, there are fewer than a dozen dedicated probes beyond low-Earth orbit making in-situ observations at any given time. As a result, we poorly understand its global structure and evolution, the mechanisms of its main activity processes, magnetic storms, and substorms. New Artificial Intelligence (AI) methods, including mac...

The properties and acceleration mechanisms of electrons (<200 keV) associated with a pair of tailward traveling flux ropes and accompanied reconnection X‐lines in Earth's plasma sheet are investigated with MMS measurements. Energetic electrons are enhanced on both boundaries and core of the flux ropes. The power‐law spectra of energetic electrons n...

We present observations that suggest the X-line of guide-field magnetic reconnection is not necessarily orthogonal to the plane in which magnetic reconnection is occurring. The plane of magnetic reconnection is often referred to as the L–N plane, where L is the direction of the reversing and reconnecting magnetic field and N is normal to the curren...

Plain Language Summary Magnetic reconnection is a plasma process which occurs throughout the universe. It accelerates and heats nearby particles, and can redistribute energy over vast scales. The rate at which it occurs, the reconnection rate, is one of the most important quantities describing reconnection. Reconnection occurs within an electron‐sc...

Whistler waves are often observed in magnetopause reconnection associated with electron beams. We analyze seven MMS crossings surrounding the electron diffusion region (EDR) to study the role of electron beams in whistler excitation. Waves have two major types: (a) Narrow‐band waves with high ellipticities and (b) broad‐band waves that are more ele...

During magnetic reconnection, field lines interconnect in electron diffusion regions (EDRs). In some EDRs, the reconnection and energy conversion rates are controlled by a steady out-of-plane electric field. In other EDRs, the energy conversion rate [Formula: see text] is “patchy,” with electron-scale large-amplitude positive and negative peaks. We...

We present observations in Earth's magnetotail by the Magnetospheric Multiscale spacecraft that are consistent with magnetic field annihilation, rather than magnetic topology change, causing fast magnetic‐to‐electron energy conversion in an electron‐scale current sheet. Multi‐spacecraft analysis for the magnetic field reconstruction shows that an e...

On 6 July 2017, the four Magnetospheric Multiscale spacecrafts were positioned within an electron diffusion region (EDR) just northward of a reconnection X line. The EDR was identified by electron crescent distributions, out-of-plane current, and energy conversion. From this position, the three spacecrafts closest to the X line (within about three...

The rate of magnetic reconnection is of the utmost importance in a variety of processes because it controls, for example, the rate energy is released in solar flares, the speed of the Dungey convection cycle in Earth’s magnetosphere, and the energy release rate in harmful geomagnetic substorms. It is known from numerical simulations and satellite o...

The rate of magnetic reconnection is of the utmost importance in a variety of processes because it controls, for example, the rate energy is released in solar flares, the speed of the Dungey convection cycle in Earth's magnetosphere, and the energy release rate in harmful geomagnetic substorms. It is known from numerical simulations and satellite o...

During magnetic reconnection, field lines interconnect in electron diffusion regions (EDRs). In some EDRs the reconnection and energy conversion rates are controlled by a steady out-of-plane electric field. In other EDRs the energy conversion rate $\vec{J}\cdot\vec{E}'$ is "patchy", with electron-scale large-amplitude positive and negative peaks. W...

We report Magnetospheric Multiscale four-spacecraft observations of a thin reconnecting current sheet with weakly asymmetric inflow conditions and a guide field of approximately twice the reconnecting magnetic field. The event was observed at the interface of interlinked magnetic field lines at the flank magnetopause when the maximum spacecraft sep...

Observations from the magnetospheric multiscale mission in or near electron diffusion regions (EDRs) at the Earth's magnetopause are used to determine the orientation of reconnection X‐lines. The results highlight cross‐scale coupling of magnetic reconnection and the differences between component and anti‐parallel reconnection. These observations a...

In‐situ spacecraft missions are powerful assets to study processes that occur in space plasmas. One of their main limitations, however, is extrapolating such local measurements to the global scales of the system. To overcome this problem at least partially, multi‐point measurements can be used. There are several multi‐spacecraft missions currently...

Plain Language Summary Space above the Earth’s atmosphere is broadly filled with ionized gas, called plasma. Since the density of the space plasma is mostly small enough to neglect the viscosity, the behavior of it is essentially different from neutral viscous fluids. In such a collisionless plasma system, the boundary layer between regions with di...

In order to determine particle velocities and electric field in the frame of the magnetic structure, one first needs to determine the velocity of the magnetic structure in the frame of the spacecraft observations. Here, we demonstrate two methods to determine a two‐dimensional magnetic structure velocity for the magnetic reconnection event observed...

We analyze data returned by the Magnetospheric Multiscale mission (MMS) constellation during a rapid (∼1.5 s) traversal of a flapping and reconnecting current sheet (CS) in the near-Earth magnetotail (X ∼−20 RE). The CS was highly tilted, with its normal pointing strongly duskward. Its extreme thinness was confirmed by a curvature analysis of the m...

We examine the 11 July 2017 electron diffusion region (EDR)observed by the MagnetosphericMultiscale (MMS) mission using Poynting's theorem. The terms in Poynting's theorem are determined using a linear gradient approximation to obtain barycentric averages within the MMS tetrahedron. We find that Poynting's theorem is approximately balanced in the E...

Magnetospheric multiscale (MMS) encountered the primary low‐latitude magnetopause reconnection site when the interspacecraft separation exceeded the upstream ion inertial length. Classical signatures of the ion diffusion region (IDR), including a subion‐Alfvénic demagnetized ion exhaust, a superion‐Alfvénic magnetized electron exhaust, and Hall ele...

Magnetic reconnection underlies many explosive phenomena in the heliosphere and in laboratory plasmas. The new research capabilities in theory/simulations, observations, and laboratory experiments provide the opportunity to solve the grand scientific challenges summarized in this whitepaper. Success will require enhanced and sustained investments f...

Electron inflow and outflow velocities during magnetic reconnection at and near the dayside magnetopause are measured using satellites from NASA's Magnetospheric Multiscale (MMS) mission. A case study is examined in detail, and three other events with similar behavior are shown, with one of them being a recently published electron‐only reconnection...

We report measurements of lower-hybrid drift waves driving electron heating and vortical flows in an electron-scale reconnection layer under a guide field. Electrons accelerated by the electrostatic potential of the waves exhibit perpendicular and nongyrotropic heating. The vortical flows generate magnetic field perturbations comparable to the guid...

Establishing the mechanism of magnetic-to-particle energy conversion through magnetic reconnection in current sheets ¹ is the key to understanding the impact of fast release of magnetic energy in many space and astrophysical plasma systems, such as during magnetospheric substorms 2,3 . It is generally believed that an electron-scale diffusion regio...

Magnetic reconnection - the topological rearrangement of magnetic field - underlies many explosive phenomena across a wide range of natural and laboratory plasmas. It plays a pivotal role in electron and ion heating, particle acceleration to high energies, energy transport, and self-organization. Reconnection can have a complex relationship with tu...

This white paper summarizes major scientific challenges and opportunities in understanding magnetic reconnection and related explosive phenomena as a fundamental plasma process.

Magnetospheric Multiscale (MMS) encountered the primary low-latitude magnetopause reconnection site when the inter-spacecraft separation exceeded the upstream ion inertial length. Classical signatures of the ion diffusion region (IDR), including a sub-ion-Alfv\'enic demagnetized ion exhaust, a super-ion-Alfv\'enic magnetized electron exhaust, and H...

We describe methods for polynomial reconstruction of the magnetic field close to a cluster of spacecraft and apply that to reconstruction of the magnetic field observed during a magnetic reconnection event on 10 August 2017 by the Magnetospheric Multiscale spacecraft. Four different models are described, which vary in complexity between a 12‐parame...

A method is described to model the magnetic field in the vicinity of three‐dimensional constellations of satellites (at least four) using field and plasma current measurements. This quadratic model matches the measured values of the magnetic field and its curl (current) at each spacecraft, with ∇ • B zero everywhere, and thus extends the linear cur...

When the supersonic solar wind encounters the Earth's magnetosphere a shock, called bow shock, is formed and the plasma is decelerated and thermalized in the magnetosheath downstream from the shock. Sometimes, however, due to discontinuities in the solar wind, bow shock ripples or ionized dust clouds carried by the solar wind, high speed jets (HSJs...

On September 8, 2018, at nearly 14:51:30 UT, the Magnetospheric Multiscale (MMS) spacecraft encountered an electron diffusion region (EDR) near the center of a flux-rope type dipolarization front. The observed signature of the magnetic field in geocentric solar ecliptic (GSE) included a bipolar Bz coinciding with a peak in By and |B| as is typical...

Substorm‐type evolution of the Earth's magnetosphere is investigated by mining more than two decades (1995–2017) of spaceborne magnetometer data from multiple missions including the first two years (2016‐2017) of the Magnetospheric MultiScale mission. This investigation reveals interesting features of plasma evolution distinct from ideal magnetohyd...

A method is described to model the magnetic field in the vicinity of constellations of multiple satellites using field and plasma current measurements. This quadratic model has the properties that the divergence is zero everywhere and matches the measured values of the magnetic field and its curl (current) at each spacecraft, and thus extends the l...

Data are analyzed from a Magnetospheric Multiscale encounter with a dayside magnetopause reconnection region on 29 December 2016. The uniqueness of the event stems from the small (~7 km) average spacecraft separation and the sequential sampling of an electron diffusion region with electron crescent distributions. We quantitatively investigate the e...

We analyze a database of Dynamics Explorer‐1 (DE‐1) Retarding Ion Mass Spectrometer densities and temperatures to yield the first explicit measure of how cold ion concentration depends on temperature. We find that cold H⁺ and He⁺ concentrations have very weak dependence on temperature, but cold O⁺ ion concentration increases steeply as these ions b...

Plain Language Summary Magnetic reconnection plays a crucial role in the dynamics of the terrestrial magnetotail. For reconnection to occur, the plasma must decouple from the magnetic field. The bounce motion of particles in the magnetotail current sheet is regarded as a key to this decoupling for cases when the current sheet has no magnetic field...