The Earths magnetosphere can go through international compression due to solar wind. This compression creates thin and non-ideal current sheets in the magnetotail. NASAs MMS spacecraft fly through this compressed, thin present sheet, and reveal that a small electric field kinds (blue line on plot) which generates an extremely sheared electron flow that drives lower hybrid waves (intense areas in plot) while the plasma density is fairly flat (orange dashed line on plot). Comprehending the formation of these present sheets and the small-scale structures and characteristics within is very important because they are thought to be necessary while doing sos that start magnetic reconnection, which can drive intense area weather in the Earths magnetosphere. Credit: Dr. Bill Amatucci, NRL
Micro-Scale Current Sheets Unleash Macro-Scale Space Weather
NRL scientists discover new physics missing out on from existing designs of magnetic reconnection.
While films show Earth as existing in a calm, beautiful corner of the universe, in reality the near-Earth area environment is dynamic and harmful. On any provided day, hot charged particles and blobs of plasma, called the solar wind, travel from the sun and are deflected by the Earths electromagnetic field, causing gorgeous aurora around north and south poles. Throughout solar storms, however, the solar wind can compress the Earths magnetic field, triggering the magnetic field lines to reorganize and reconnect (likewise referred to as magnetic reconnection), shooting hot, dense plasma back toward the Earth. Procedures like these are typically described as space weather condition. Because of the effect that these space-based disruptions can have on crucial elements of our contemporary society, such as telecommunication systems and power grids, obtaining a mutual understanding of these processes is simply as vital as understanding ground-based weather condition.
A significant difficulty in understanding magnetic reconnection in the Earths magnetosphere has actually been the problem in solving the smaller sized kinetic-scale processes in satellite observations. NASAs Magnetospheric Multi-Scale (MMS) spacecraft, however, recently made it possible to make in-depth studies of this previously hidden micro-scale physics.
NASAs MMS spacecraft fly through this compressed, thin present sheet, and expose that a small electrical field forms (blue line on plot) which creates an extremely sheared electron flow that drives lower hybrid waves (bright areas in plot) while the plasma density is relatively flat (orange dashed line on plot). Understanding the development of these existing sheets and the small-scale structures and dynamics within is crucial because they are thought to be essential in the processes that start magnetic reconnection, which can drive intense area weather in the Earths magnetosphere. The velocity shear is produced in the current sheet when a localized electric field oriented perpendicular to the background magnetic field arises as the present sheet is compressed. NRL scientists likewise used these observations to find a key element missing from existing theoretical designs of thin current sheets and magnetic reconnection– an ambipolar electrical field that forms perpendicular to the present sheet and intensifies as the current sheet undergoes strong compression. The existing driven by the electron circulation likewise changes the magnetic field profiles and allows for the formation of present sheets that are both thin and non-ideal, functions which can not simultaneously be discussed by the standard designs.
Researchers at the U.S. Naval Research Laboratory (NRL) in Washington, D.C. have been using MMS information to study the micro-scale physics that occurs in the Earths magnetotail, a thin portion of the magnetosphere that is highlighted in Figure 1. The magnetotail is formed when the Earths magnetosphere is compressed by the solar wind into a thin present sheet, creating an ideal area to study magnetic reconnection.
NRL scientists recently made the very first observation of plasma waves driven by highly sheared electron flows (velocity shear) in one of these compressed present sheets. When a localized electric field oriented perpendicular to the background magnetic field emerges as the present sheet is compressed, the speed shear is produced in the existing sheet. These waves are an abundant source of local improved diffusivities, which can set off the magnetic reconnection procedure.
NRL researchers likewise utilized these observations to discover an essential component missing from existing theoretical models of thin current sheets and magnetic reconnection– an ambipolar electric field that forms perpendicular to the current sheet and heightens as the present sheet undergoes strong compression. A brand-new theoretical design has actually because been established and suggests that the ambipolar electrical field can self-consistently establish in response to worldwide compression of the plasma. This in turn produces the speed shear that can drive the waves observed in the spacecraft information. The current driven by the electron flow also changes the magnetic field profiles and permits for the development of existing sheets that are both thin and non-ideal, features which can not concurrently be described by the basic models. The theoretical design results shine a new light on the essential connection between the micro-scale and macro-scale physics.
These findings challenge the existing understanding of the physics of thin current sheets, and the recognition of the shear-driven plasma waves likewise establishes the significance of the localized ambipolar electrical field and the extremely inhomogeneous conditions that drive the physics. This much deeper understanding of the physics at small scales, when combined with the bigger scale models, will cause a more total understanding of the worldwide dynamics and especially the energy flux in the heliosphere from the sun into the Earths immediate neighborhood that impacts near-Earth area weather.
Fulfilling: 63rd Annual Meeting of the APS Division of Plasma Physics
GI01.00002: Structure and Dynamics of a Compressed Current Sheet in the Earths Magnetotail
This work is supported by the NRL base funds.
