Cosmicopia title
BASICS .. COSMIC RAYS .. SUN .. SPACE WEATHER

Glossary:
G and H

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



G

Galactic
Having to do with the galaxy.

Galactic Cosmic Rays (GCRs)
These cosmic ray particles come from outside our solar system, but from within our galaxy. They have lost all of their electrons during their trip through the galaxy.

More about GCRs...

Galaxy
galaxy
One of billions of large systems of stars and gas, held together by gravity, that make up the universe.

Gamma rays
Gamma ray skyHigh energy electromagnetic radiation (in excess of 100 keV) which can be generated by nuclear reactions in space. This is an image of the EGRET gamma ray all-sky survey - above 100 MeV.

More about gamma rays in "Imagine the Universe!"...

Gas
A low number of atoms or molecules in a relatively large volume of space. Atoms or molecules are spread apart relative to each other.

Gas-proportional counter
An instrument that measures the point of impact of a particle and the energy loss of the particle through a gas inside the counter. There are gas-proportional counters are on the SEPICA instrument onboard the ACE spacecraft.

Geocentric
Based on the Earth as center; as, the geocentric theory of the universe.

Geomagnetic storm
A magnetic storm on Earth.

GMT (Greenwich Mean Time)
The local time at the 0 meridian passing through Greenwich, England; it is the same everywhere. Same as UT (Universal Time).

Gradual flares
One of two general types of solar flares. Gradual flares accelerate mostly protons and last for several days. They occur mainly near the poles of the Sun and happen, on average, about 100 times per year.

Gravity
A physical force attracting one object to another object.

Ground station
Ground stations are the link between the control system and a satellite in orbit. They track a satellite's signal to find it's location, and the status of equipment onboard and distribute that information to interested parties. They are also used to transmit operational signals back to the satellite to help control it.

GSFC
GSFC logo
The NASA/Goddard Space Flight Center in Greenbelt, MD.




H

Helio-
Prefix referring to the Sun.

Heliocentric
With the Sun at the center.

Heliopause
The gradual boundary between the heliosphere and the interstellar gas outside our solar system. See the diagram with the definition of "heliosphere" below.

Heliosphere
The Heliosphere
The area in space that contains our solar system, solar wind, and the entire solar magnetic field. It extends well beyond the orbit of Pluto, out to the heliopause.

More about the heliosphere...


Helium
The gas made from hydrogen in the core of stars by nucleosynthesis. Each atom of helium contains two protons.

Hemisphere
One half of a sphere or globe. The northern hemisphere on Earth is divided from the southern hemisphere by the equator.

Hodoscope
An instrument that determines the three-dimensional path of a particle through it. Hodoscopes are used in both the SIS and CRIS instruments on the ACE spacecraft.

Hydrogen
The most common gas in the universe. Each atom of hydrogen contains one proton.


A.. B.. C.. D.. E.. F.. G.. H.. I.. J.. K.. L.. M..

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


BASICS .. COSMIC RAYS .. SUN .. SPACE WEATHER

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: cosmicopia@cosmicra.gsfc.nasa.gov
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