Related Experiment Video
Updated: Apr 16, 2026
06:42
Magnetically Induced Rotating Rayleigh-Taylor Instability
Published on: March 3, 2017
10.2K
Universal instability for wavelengths below the ion Larmor scale.
Matt Landreman1, Thomas M Antonsen1, William Dorland1
1Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742, USA.
Physical Review Letters
|March 21, 2015
Summary
Plasma drift waves can be unstable even with magnetic shear. A new gyrokinetic approach shows absolute instability for universal modes, challenging older models limited by ion Larmor radius assumptions.
Area of Science:
- Plasma Physics
- Magnetohydrodynamics
- Instability Theory
Background:
- Previous studies (1970s) suggested universal modes in plasma slabs are stable with magnetic shear.
- These earlier conclusions were based on eigenmode equations with limitations (Lx >> ρi).
Purpose of the Study:
- To investigate the stability of universal modes in plasma slabs under magnetic shear using a more advanced approach.
- To challenge and refine the understanding of plasma drift wave stability.
Main Methods:
- Employed a gyrokinetic approach, overcoming limitations of previous eigenmode equations.
- Analyzed instability conditions concerning perpendicular wave numbers (kyρi) and magnetic shear (Ls/Ln).
Main Results:
- Demonstrated that universal modes can be absolutely unstable even with significant magnetic shear.
- Identified instability for 0.7≲kyρi≲100 and Ls/Ln≳17.
- Showed instability occurs without temperature gradients, trapped particles, or magnetic curvature.
Conclusions:
- The universal mode driven by density gradients is not necessarily stable in sheared magnetic fields.
- Gyrokinetic theory provides a more accurate description of plasma drift wave stability.
- Findings have implications for understanding plasma behavior in fusion devices and astrophysical plasmas.
Related Concept Videos
02:32The de Broglie Wavelength
34.8K
In the macroscopic world, objects that are large enough to be seen by the naked eye follow the rules of classical physics. A billiard ball moving on a table will behave like a particle; it will continue traveling in a straight line unless it collides with another ball, or it is acted on by some other force, such as friction. The ball has a well-defined position and velocity or well-defined momentum, p = mv, which is defined by mass m and velocity v at any given moment. This is the typical...
34.8K
01:11Atomic Nuclei: Larmor Precession Frequency
3.8K
The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession,...
3.8K
02:18The Bohr Model
84.3K
Following the work of Ernest Rutherford and his colleagues in the early twentieth century, the picture of atoms consisting of tiny dense nuclei surrounded by lighter and even tinier electrons continually moving about the nucleus was well established. This picture was called the planetary model since it pictured the atom as a miniature “solar system” with the electrons orbiting the nucleus like planets orbiting the sun. The simplest atom is hydrogen, consisting of a single proton as...
84.3K
01:04Oscillations about an Equilibrium Position
7.3K
Stability is an important concept in oscillation. If an equilibrium point is stable, a slight disturbance of an object that is initially at the stable equilibrium point will cause the object to oscillate around that point. For an unstable equilibrium point, if the object is disturbed slightly, it will not return to the equilibrium point. There are three conditions for equilibrium points—stable, unstable, and half-stable. A half-stable equilibrium point is also unstable, but is named so...
7.3K
01:30Plane Electromagnetic Waves I
5.4K
The existence of combined electric and magnetic fields that propagate through space as electromagnetic (EM) waves is the most significant prediction of Maxwell's equations. As Maxwell's equations hold in free space, the predicted electromagnetic waves do not require a medium for their propagation. An EM wave comprises an electric field, defined as the force per charge on a stationary charge, and a magnetic field, which is the force per charge on a moving charge.
The EM field is assumed to be a...
The EM field is assumed to be a...
5.4K
01:23Atomic Nuclei: Nuclear Relaxation Processes
1.4K
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis.
1.4K