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Magnetic Field Lines

Magnetic Field Lines

The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the magnetic field lines forms a closed loop. The field lines emerge from the north pole (N), loop around to the south pole (S), and continue through the bar magnet back to the north pole.
Magnetic field lines follow several hard-and-fast rules:

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.

Magnetic Declination

Magnetic Declination

Magnetic declination is the angle between true north, which aligns with the Earth's rotational axis, and magnetic north, which follows the direction of the Earth's magnetic field. This discrepancy exists because the magnetic poles do not coincide with the geographic poles. The value of magnetic declination depends on the observer's location on Earth and is subject to changes over time due to the dynamic nature of the Earth's magnetic field.The declination is called eastern when magnetic north...

Atomic Nuclei: Larmor Precession Frequency

Atomic Nuclei: Larmor Precession Frequency

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, and the angular frequency...

Torque On A Current Loop In A Magnetic Field

Torque On A Current Loop In A Magnetic Field

The most common application of magnetic force on current-carrying wires is in electric motors. These consist of loops of wire, which are placed between the magnets with a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate, thus converting electrical energy to mechanical energy.
Consider a rectangular current-carrying loop containing N turns of wire, placed in a uniform magnetic field. The net force on a current-carrying loop...

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...

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Related Experiment Video

Updated: Jun 8, 2026

Applying X-ray Imaging Crystal Spectroscopy for Use as a High Temperature Plasma Diagnostic

Applying X-ray Imaging Crystal Spectroscopy for Use as a High Temperature Plasma Diagnostic

Published on: August 25, 2016

Identifying the driver of pulsating aurora.

Y Nishimura¹, J Bortnik, W Li

¹Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA 90095, USA. toshi@atmos.ucla.edu

Science (New York, N.Y.)

|October 9, 2010

Summary

This summary is machine-generated.

Scientists identified the cause of pulsating aurora, a phenomenon in Earth's polar regions. Lower-band chorus waves were found to drive the electron precipitation responsible for the shimmering auroral displays.

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Last Updated: Jun 8, 2026

Applying X-ray Imaging Crystal Spectroscopy for Use as a High Temperature Plasma Diagnostic

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Published on: February 4, 2017

Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

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Published on: July 2, 2012

Area of Science:

Space Physics
Atmospheric Science
Plasma Physics

Background:

Pulsating aurora, characterized by blinking emissions in polar regions, is caused by modulated electron precipitation.
The specific driver of this electron precipitation has remained unidentified, posing a long-standing challenge in space physics.

Purpose of the Study:

To identify the natural driver of electron precipitation responsible for pulsating aurora.
To establish a direct link between specific electromagnetic waves and pulsating auroral events.

Main Methods:

Coordinated observations using satellite data from the THEMIS mission.
Simultaneous ground-based all-sky imager observations.
Correlation analysis between equatorial wave activity and auroral patch dynamics.

Main Results:

Direct evidence was found linking naturally occurring lower-band chorus waves to the excitation of pulsating aurora.
A one-to-one correlation was observed between specific equatorial wave locations and individual pulsating auroral patches.

Conclusions:

Lower-band chorus waves are confirmed as the driver of pulsating aurora.
These findings enable more accurate magnetic field model constraints by precisely linking space-based wave observations to atmospheric phenomena.