The Space Plasma Environment of the Earth

J. Goldstein

The near-Earth space environment is not a perfect vacuum, but rather is filled with plasma, or ionized gas. Plasma is formed when the upper parts of the Earth's atmosphere are electrified by the Sun's ultraviolet rays. Here is a visualization of the ionization process:

MOVIE of Ionization (QuickTime movie, 2.6 MB)

This plasma leaks out into space, and fills up the Earth's nearby space environment. The plasmasphere is a doughnut-shaped region of ionized gas, or plasma. In this animation, the plasmasphere is the green region surrounding the Earth. The viewpoint of the animation varies from above the North pole to below the South pole of the Earth, and shows the 3D shape of the plasmasphere. As you can see from the animation, the outer boundary of the plasmasphere, which we call the plasmapause, mostly follows the Earth's magnetic field lines, which are drawn in gray here.
Plasmasphere ANIMATION (QuickTime movie, 2.6 MB)

How do we know what the plasmasphere looks like?
.... Image and Model of the Plasmasphere

The right panel of this slide shows a single snapshot from the animation you just saw, which was a model based on the data shown in the left panel.

The left panel shows an image of the plasmasphere obtained by the NASA satellite called IMAGE. The plasmasphere emits a glow in the ultraviolet range of the electromagnetic spectrum. Cameras onboard the IMAGE satellite are able to capture this ultraviolet glow, producing the false-color picture you see. The plasmasphere is the green-to-white region surrounding the Earth.

The process that produces the plasmasphere's very faint ultraviolet glow is called resonant scattering, in which a solar ultraviolet photon is absorbed by a plasmaspheric helium ion, and then re-emitted. By detecting these re-emitted ultraviolet photons, we are able to see the plasmasphere.

MOVIE of Resonant Scattering (QuickTime movie, 4.5 MB)

The plasmasphere is only one part of a larger space environment called the magnetosphere. The magnetosphere is the nearby space environment that is dominated by the Earth's magnetic field. Much like a bar magnet, the Earth has its own intrinsic magnetic field:

MOVIE: The Earth's Intrinsic Magnetic Field (QuickTime movie, 250 KB)

The Earth's intrinsic "bar magnet" magnetic field is distorted in space by the influence of the solar wind. The solar wind is the Sun's outflowing atmosphere. The solar wind compresses the Earth's magnetic field on the dayside, and stretches it out (into a long comet-like tail) in the nightside. An artist's conception of the magnetosphere:

Our solar system has the cosmic equivalent of winds, clouds, storms, and hurricanes; we call it space weather. Just like weather on Earth, it can be both mild and wild. It is as changeable as the everyday weather we experience outside Š but is windier than on a mountain peak and as electric as a city night.

Solar flares often result in violent explosions called Coronal Mass Ejections, or CMEs. When such CMEs are directed toward the earth, turbulent shock waves of charged gas and their accompanying magnetic fields impact our Earth's protective layer, called the magnetosphere.

These impacts in turn cause storms within our magnetosphere that can interfere with radio, television, and telephone signals, damage satellites and disrupt GPS communications. In September a class X17 solar flare created a blackout of high-frequency radio communications on the entire sunlit side of the Earth, temporarily disrupting a variety of communications, including those used by relief teams responding to Hurricane Katrina.
.... ANIMATION OF SOLAR CORONAL MASS EJECTION

For more exciting pictures of the Earth's space environment, see the following PDF file:
PDF Tutorial Pictures of Space Plasma Environment of Earth.