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An instrument for measuring quantities of heat

The California Institute of Technology in Pasadena, California.

Charge exchange
The loss of an electron by an atomic particle to an ionized atom. This can occur when neutral interstellar material leaks into the heliosphere and runs into ionized solar wind to create pick-up ions.

The part of the Sun just above the photosphere. Thousands of miles thick, it is mostly hydrogen gas. It looks like a red ring during an eclipse. The corona is just above the chromosphere.

A part of an instrument that selects the arrival direction of incoming particles or energy. Three collimators are in SEPICA, an instrument on the ACE spacecraft.

Comet Hale-Bopp A small body, of mostly ice and dust, in orbit around the Sun or passing through the solar system in large orbits. While passing near the Sun, the comet's vaporized ice becomes its two tails, a bright white one composed of dust, and a blue one made up of ionized gas.

More about comets...

What an object is made of

More about composition...

The outer part of the Sun's "atmosphere". In the outer region of the corona, particles travel away from the Sun and stretch far out into space. The corona can only be seen during total solar eclipses, appearing as a halo around the moon.

SOHO/LASCO coronagraph image of the SunAn instrument that makes it possible to observe the corona at times other than during an eclipse. A simple lens focuses the Sun onto a disk that blocks the light from the solar disk, providing an artificial eclipse. This image of the Sun is from the SOHO/LASCO coronagraph instrument.

Coronal holes
Large regions in the corona that are less dense and cooler than surrounding areas. There is a constant flow of low density plasma escaping from the holes.

More about coronal holes...

Coronal mass ejections (CMEs)
Huge bursts of solar wind rising above the Sun's corona. One of the biggest explosions in our solar system.

More about CMEs...

Sharing the rotation of a planetary magnetic field, as in Corotating Interaction Regions.

Corotating Interaction Regions (CIRs)
The area in the heliosphere where there is an interaction between high and low speed streams of solar wind that causes a shock wave of high density, pressure and magnetic field strength.

More about CIRs...

Cosmic rays
A stream of particles that have been accelerated to almost the speed of light in space. Some enter the Earth's atmosphere and bombard atmospheric atoms.

More about cosmic rays...


Data analysis
Processing, checking over, and trying to understanding information (data).

Delta II rocket
Delta II launch
The Delta II is the latest generation of Delta medium-launch vehicle. It was used to launch the ACE spacecraft, among others.

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TRACE sun mosaic Supernova 1006 (ASCA) 30
Doradus ACE
spacecraft TRACE solar flare IMAGE magnetosphere
Click on images above to learn more about them

A service of the Heliophysics Science Division at NASA's GSFC

Questions and comments to:
Curator: Dr Eric R. Christian, NASA
Responsible NASA Official: Dr Eric R. Christian

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This file was last modified: December 29, 2006