Index of Information about the Ionosphere
A concise introduction to the ionosphere and ionospheric research provided by the High Frequency Active Auroral Research Program (HAARP), a joint Navy-Air Force ionospheric research project being conducted in Alaska. A resources page gives links to Web sites with other tutorial-type information about the ionosphere and magnetosphere, solar-terrestrial data sites, the Web sites of other ionospheric research facilities, and more. http://www.haarp.alaska.edu/haarp/ionindex.html

Ionospheric Data at the NGDC
This site is maintained by the Ionospheric Physics Group of NOAA's National Geophysical Data Center and offers a brief introduction to the ionosphere, with a description of the ionospheric layers, and to the history and use of ionosondes to study the ionosphere. http://www.ngdc.noaa.gov/stp/IONO/ionohome.html

INSPIRE Web Site
The INSPIRE (Interactive NASA Space Physics Ionosphere Radio Experiments) project offers students entry into the field of ionospheric physics through the study of VLF radio emissions. Instructions for the construction of radio receivers and data analysis are provided. http://image.gsfc.nasa.gov/poetry/inspire/

Oulu Space Physics Textbook
The ionosphere page of the Oulu Textbook provides a helpful overview of the ionosphere, with hyperlinked definitions of key terms: http://www.oulu.fi/~spaceweb/textbook/ionosphere.html. (See comprehensive sites for a description of the Oulu Textbook.)