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Magnetostatic Boundary Conditions

Magnetostatic Boundary Conditions

An electric field suffers a discontinuity at a surface charge. Similarly, a magnetic field is discontinuous at a surface current. The perpendicular component of a magnetic field is continuous across the interface of two magnetic mediums. In contrast, its parallel component, perpendicular to the current, is discontinuous by the amount equal to the product of the vacuum permeability and the surface current. Like the scalar potential in electrostatics, the vector potential is also continuous...

Electrostatic Boundary Conditions

Electrostatic Boundary Conditions

Consider an external electric field propagating through a homogeneous medium. When the electric field crosses the surface boundary of the medium, it undergoes a discontinuity. The electric field can be resolved into normal and tangential components. The amount by which the field changes at any boundary is given by the difference between the field components above and below the surface boundary.
The surface integral of an electric field is given by Gauss's law in integral form and is related to...

Magnetic Field due to Moving Charges

Magnetic Field due to Moving Charges

A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...

Magnetic Field Of A Current Loop

Magnetic Field Of A Current Loop

Consider a circular loop with a radius a, that carries a current I. The magnetic field due to the current at an arbitrary point P along the axis of the loop can be calculated using the Biot-Savart law.

Electrostatic Boundary Conditions in Dielectrics

Electrostatic Boundary Conditions in Dielectrics

When an electric field passes from one homogeneous medium to another, crossing the boundary between the two mediums imparts a discontinuity in the electric field. This results in electrostatic boundary conditions that depend on the type of mediums the field propagates through.
Consider a case where both the mediums across a boundary are two different dielectric materials. Recall that the electric field and electric displacement are proportional and related through the material's permittivity....

Boundary Conditions for Current Density

Boundary Conditions for Current Density

Current density becomes discontinuous across an interface of materials with different electrical conductivities. The normal component of the current density is continuous across the boundary.

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Transient, small-scale field-aligned currents in the plasma sheet boundary layer during storm time substorms.

R Nakamura¹, V A Sergeev², W Baumjohann¹

¹Space Research Institute Austrian Academy of Sciences Graz Austria.

Geophysical Research Letters

|November 22, 2016

Summary

Magnetotail reconnection generates small-scale field-aligned currents within plasma sheet boundary layer flux tubes. These currents, below the ion scale, coincide with upward electron beams, revealing multiscale process coupling during substorms.

Keywords:

MMS PSBL electron beam field‐aligned currents

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Area of Science:

Space Physics
Plasma Physics
Magnetospheric Physics

Background:

The plasma sheet boundary layer (PSBL) is a critical region for understanding energy transfer in Earth's magnetosphere.
Magnetotail reconnection is a primary driver of substorm dynamics and associated phenomena.

Purpose of the Study:

To investigate small-scale field-aligned currents within the PSBL during substorm events.
To characterize the properties and origins of these currents and associated electron beams.

Main Methods:

Utilized in-situ observations from the four Magnetospheric Multiscale (MMS) spacecraft.
Analyzed field-aligned current densities and electron beam characteristics near the PSBL separatrix region.

Main Results:

Resolved short-lived, intense field-aligned current sheets with thicknesses below the ion scale.
Observed these currents on flux tubes moving equatorward/earthward during plasma sheet expansion.
Found coincident upward field-aligned electron beams with energies of a few hundred eV.

Conclusions:

These findings highlight the coupling of multiscale processes in the PSBL.
The observed phenomena are a consequence of magnetotail reconnection and associated jet or beam disturbances.