In the photograph, the aurora australis is seen in a distinctly circular pattern as it appears from space over Antarctica.  The same pattern is observed over the arctic region.  The circular pattern is related to the fact that the magnetic field exits and enters Earth near the geographical poles.  These regions have a significant magnetic field passing vertically through the ionosphere.  The magnetic field at these locations is also perpendicular to the motion of the charged particles in the solar wind.
Image courtesy NASA


Watch and Listen

Watch the video Lorentz Force to learn how Earth's magnetic field exerts a magnetic force on charged particles to create the aurora.

Cathode ray tubes played a very important role in the process of scientific discovery. They were instrumental in determining the charge-to-mass ratio of an electron and, ultimately, the mass of an electron.  Cathode ray tubes also continue to be used for the demonstration of electromagnetism, revealing the relationship between magnetism and electricity.

 After the work of Thomson, the CRT went on to be used in all kinds of applications such as the tube TV and computer monitor.

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