Multiscale Magnetospheric Processes

The Magnetospheric Multiscale (MMS) mission is a multiple-spacecraft Solar-Terrestrial Probe designed to study the microphysics of magnetic reconnection, charged particle acceleration, and turbulence in key boundary regions of Earth's magnetosphere. These three processes, which control the flow of energy, mass, and momentum within and across plasma boundaries, occur throughout the universe and are fundamental to our understanding of astrophysical and solar system plasmas.

NASA’s Magnetospheric Multiscale (MMS) mission is a four-spacecraft Solar Terrestrial Probe mission to study magnetic reconnection, a fundamental plasma physical process in which energy stored in a magnetic field is converted into the kinetic energy of charged particles and heat. The driver of eruptive solar events such as flares and coronal mass ejections, magnetic reconnection is also the process by which energy is transferred from the solar wind to Earth’s magnetosphere. Flying in a tetrahedral formation, the four identically instrumented MMS spacecraft measure the plasma, electric and magnetic fields, and energetic particles in the regions of geospace where magnetic reconnection is expected to occur. With interspacecraft distances varying from 400 km to 10 km and instruments capable of making extremely fast measurements (30 ms for electrons), MMS has the spatial and temporal resolution needed to resolve for the first time the microphysics of the electron diffusion region. Here, the magnetic field and the plasma become decoupled, allowing reconnection to occur. During the first of its two mission phases, MMS targets the dayside magnetopause, where the interplanetary and terrestrial magnetic fields reconnect. In the second phase, MMS increases its apogee from 12 RE to 25 RE and probes the nightside magnetosphere, where energy stored in the stretched field lines of the magnetotail is explosively released in magnetospheric substorms. Launched in March 2015 into a low-inclination elliptical orbit, MMS is now in Phase 1 of science operations. This volume, which describes the MMS mission design, observatories, instrumentation, and operations, is aimed at researchers and graduate students in magnetospheric physics and plasma physics. Researchers using the publicly available MMS data will find it particularly useful. Previously published in Space Science Reviews, Volume 199, Nos. 1-4, 2016.

The Magnetospheric Multiscale (MMS) mission is a multiple-spacecraft Solar-Terrestrial Probe designed to study the microphysics of magnetic reconnection, charged particle acceleration, and turbulence in key boundary regions of Earth's magnetosphere. These three processes, which control the flow of energy, mass, and momentum within and across plasma boundaries, occur throughout the universe and are fundamental to our understanding of astrophysical and solar system plasmas. Only in Earth's magnetosphere, however, are they readily accessible for sustained study through in-situ measurement. MMS will employ five co-orbiting spacecraft identically instrumented to measure electric and magnetic fields, plasmas, and energetic particles. The initial parameters of the individual spacecraft orbits will be designed so that the spacecraft formation will evolve into a three-dimensional configuration near apogee, allowing MMS to differentiate between spatial and temporal effects and to determine the three dimensional geometry of plasma, field, and current structures. In order to sample all of the magnetospheric boundary regions, MMS will employ a unique four-phase orbital strategy involving carefully sequenced changes in the local time and radial distance of apogee and, in the third phase, a change in orbit inclination from 10 degrees to 90 degrees. The nominal mission operational lifetime is two years. Launch is currently scheduled for 2006.Curtis, S.Goddard Space Flight CenterEARTH MAGNETOSPHERE; SPACE PLASMAS; SPACE PROBES; CHARGED PARTICLES; MAGNETIC FIELD RECONNECTION; SOLAR SYSTEM; MAGNETOPAUSE; BOUNDARY LAYERS; SPACECRAFT CONFIGURATIONS; SPACECRAFT ORBITS; PARTICLE ACCELERATION

The past forty years of space research have seen a substantial improvement in our understanding of the Earth’s magnetosphere and its coupling with the solar wind and interplanetary magnetic ?eld (IMF). The magnetospheric str- ture has been mapped and major processes determining this structure have been de?ned. However, the picture obtained is too often static. We know how the magnetosphere forms via the interaction of the solar wind and IMF with the Earth’s magnetic ?eld. We can describe the steady state for various upstream conditions but do not really understand the dynamic processes leading from one state to another. The main dif?culty is that the magnetosphere is a comp- cated system with many time constants ranging from fractions of a second to days and the system rarely attains a steady state. Two decades ago, it became clear that further progress would require multi-point measurements. Since then, two multi-spacecraft missions have been launched — INTERBALL in 1995/96 and CLUSTER II in 2000. The objectives of these missions d- fered but were complementary: While CLUSTER is adapted to meso-scale processes, INTERBALL observed larger spatial and temporal scales. However, the number of papers taking advantage of both missions simul- neously is rather small.

The past forty years of space research have seen a substantial improvement in our understanding of the Earth’s magnetosphere and its coupling with the solar wind and interplanetary magnetic ?eld (IMF). The magnetospheric str- ture has been mapped and major processes determining this structure have been de?ned. However, the picture obtained is too often static. We know how the magnetosphere forms via the interaction of the solar wind and IMF with the Earth’s magnetic ?eld. We can describe the steady state for various upstream conditions but do not really understand the dynamic processes leading from one state to another. The main dif?culty is that the magnetosphere is a comp- cated system with many time constants ranging from fractions of a second to days and the system rarely attains a steady state. Two decades ago, it became clear that further progress would require multi-point measurements. Since then, two multi-spacecraft missions have been launched — INTERBALL in 1995/96 and CLUSTER II in 2000. The objectives of these missions d- fered but were complementary: While CLUSTER is adapted to meso-scale processes, INTERBALL observed larger spatial and temporal scales. However, the number of papers taking advantage of both missions simul- neously is rather small.

Magnetic reconnection is a process that converts magnetic energy into kinetic energy in a plasma system through a change in topology of the magnetic field lines, and it allows explosive events such as coronal mass ejections and sawtooth crashes in magnetically-confined nuclear fusion experiments to occur. Reconnection mediates the transfer of solar wind plasma into Earth's magnetosphere. To learn more about the process of magnetic reconnection, NASA launched its Magnetospheric Multiscale (MMS) mission in 2015. In this thesis, we consider aspects of magnetic reconnection in relation to MMS observations and goals. We begin by further examining anisotropic equations of state (EoS) previously developed to describe the pressure parallel to and perpendicular to the local magnetic field. We find that the EoS holds near the x-line for an MMS event in the guide-field regime, and hybrid simulations (kinetic ions, fluid electrons with the EoS as a closure) are able to properly reproduce the MMS observations. We then apply the EoS to derive scalings of the electron bulk heating in the exhaust with upstream parameters. Afterwords, we examine another MMS event in the guide-field regime, this time much farther from the x-line, and show that the EoS also hold here. This event took place in a region of active compression, and we extend the model of the EoS to account for the energy gains from compression, showing that local electron trapping plays a role in additional perpendicular heating of the electrons. Finally, we present a drift-kinetic method that links agyrotropy, the lack of symmetry in the velocity space plane perpendicular to the magnetic field, to gradients in plasma properties. The method can predict gradients in fluid properties of the plasma based on a distribution function measured at a single spatial point, and could add significant utility to MMS observations.

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