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E and F

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N.. O.. P.. Q.. R.. S.. T.. U.. V.. W.. X.. Y.. Z..


The third planet from the Sun.

The blocking of some or all of the light from one object by another. This eclipse image is courtesy of NASA DFRC.

Electric charge
A physical state based on the amount and location of electrons and protons in matter. Matter with more electrons than protons is negatively charged. Matter that attracts free electrons is positively charged.

The negatively charged part of an atom. It orbits the atom's nucleus. Electrons are very light compared to protons and neutrons.

More about electrons...

Electron volt (eV)
The unit used to describe the total energy carried by a particle. It is the energy gained by an electron (or proton, same size of electric charge) moving through a voltage difference of one volt.
  • A keV (or kilo-electron volt) is equal to one thousand electron volts.
  • An MeV (mega-electron volt) is equal to one million electron volts.
  • A GeV (giga-electron volt) is equal to one billion (109) electron volts.

    More about electron volts...

Electrostatic analyzer
An instrument that identifies particles by measuring the electrostatic deflection in the system. This instrument is in both the SWEPAM and SWICS instruments on the ACE spacecraft.

Electrostatic deflection
The amount of bending of a particle's flight path in a constant electric field. This property is used in an electrostatic analyzer.

A material consisting of atoms, all with the same atomic number. Approximately 90 different elements are known to exist in nature and several others have been created in nuclear reactions. For more information about the elements, see the Periodic Table of the Elements.

The ability to do work. There are many types of energy including light, electricity, heat, and nuclear energy.

Energy-loss stack
The arrangement in an instrument of a stack of detectors, each of which measures the energy loss of particles as they slow and stop in the stack. Energy-loss stacks are used in both the SIS and CRIS instruments on the ACE spacecraft.

An imaginary line around the center of a body where every point on the line is an equal distance from the poles. The equator defines the boundary between the northern and southern hemispheres.

Outside our galaxy.


The rate of particle flow over time.

A type of nuclear reaction in which two atomic nuclei combine to form a heavier nucleus, releasing energy.

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 14, 2004