Synopsis: Asymmetric Reconnections

Satellite observations of the Earth’s magnetosphere reveal how electrons are heated when plasmas with different densities, temperatures, and magnetic field strengths collide.
Synopsis figure
European Space Agency

When two domains of a magnetized plasma meet, magnetic field lines can snap and reconnect, changing the magnetic topology and thereby releasing energy. Researchers believe that such “magnetic reconnection” partly powers solar flares and can cause failures of plasma confinement in tokamaks. It is also one of the causes of auroras in the Earth’s magnetosphere.

If the colliding magnetic plasmas have the same temperature, density, and magnetic field strength, such reconnection is symmetric, and it is understood for the most part. But when the plasmas have dissimilar properties, as in regions of the magnetosphere that deflect the solar wind, reconnection is asymmetric, and the mechanisms involved in energy transfer are much less well known. In Physical Review Letters, Daniel Graham of the Swedish Institute of Space Physics and colleagues report observational data that give a detailed picture of how asymmetric reconnection works.

The authors used data from the Cluster II mission, a set of four satellites orbiting the Earth in a tetrahedral formation. As the spacecraft crossed the magnetopause (the boundary between the planetary magnetic field and the solar wind), onboard instruments collected magnetic field and electron data in the plasma. An abrupt reversal in magnetic field direction indicated when the instruments were passing through the reconnection region, and the electron data gave clues on the energy exchange mechanisms. The data provided the evidence of reconnection and revealed some of its key features. In particular, most of the action happens where electrons from the magnetosphere are trapped along the magnetic field lines, where they are accelerated by the electric field. The results should help researchers produce better models of asymmetric reconnection and particle heating in the magnetosphere. – David Voss


Features

More Features »

Announcements

More Announcements »

Subject Areas

AstrophysicsPlasma Physics

Previous Synopsis

Atomic and Molecular Physics

Free Falling Matter Waves

Read More »

Next Synopsis

Related Articles

Viewpoint: Spinning Black Holes May Grow Hair
Gravitation

Viewpoint: Spinning Black Holes May Grow Hair

A spinning black hole may lose up to 9% of its mass by spontaneously growing “hair” in the form of excitations of a hypothetical particle field with a tiny mass. Read More »

Synopsis: A Reionization Filter for the Cosmic Microwave Background
Cosmology

Synopsis: A Reionization Filter for the Cosmic Microwave Background

A new method of analyzing cosmic microwave background data could isolate signatures from the so-called reionization period that occurred a few hundred million years after the big bang. Read More »

Synopsis: LIGO’s Black Hole Got the Boot
Astrophysics

Synopsis: LIGO’s Black Hole Got the Boot

An analysis of data from LIGO’s second gravitational-wave event indicates that a supernova can impart a strong kick to the black hole it creates. Read More »

More Articles