Last week at the Space Weather Workshop in Boulder, Colorado, NASA released a 4D live model of the Earth's ionosphere. Without leaving home, anyone can fly through the layer of ionized gas that encircles Earth at the edge of space itself. All that is required is an Internet connection and a free copy of Google Earth. NASA calls the ionosphere the "last wisp of Earth's atmosphere that astronauts leave behind when they enter space.

The realm of the ionosphere stretches from 50 to 500 miles above Earth's surface where the atmosphere thins to near-vacuum and exposes itself to the fury of the sun. Solar ultraviolet radiation breaks apart molecules and atoms creating a globe-straddling haze of electrons and ions."

Using a Google Earth interface, users can fly above, around and through these regions getting a true 4D view of the situation. "The fourth dimension is time. This is a real-time system updated every 10 minutes," said W. Kent Tobiska, president of Space Environment Technologies and chief scientist of its Space Weather Division.

The proper name of the system is CAPS, short for Communication Alert and Prediction System. Earth-orbiting satellites feed the system up-to-the-minute information on solar activity; the measurements are then converted to electron densities by physics-based computer codes. It is important to note, Tobiska said, that CAPS reveals the ionosphere not only as it is now, but also as it is going to be the near future.

According to propagation specialist Carl Luetzelschwab, K9LA, this model "can provide Amateur Radio operators a broad view of what the ionosphere is doing 'now.' This broad view is due to the fact that the resolution in the color coding schemes only gives coarse estimates of the six parameters available." Luetzelschwab, former editor of National Contest Journal (NCJ), writes a propagation column in NCJ and other publications

"This is an exciting development," said NASA solar physicist Lika Guhathakurta. "The ionosphere is important to pilots, ham radio operators, earth scientists and even soldiers. Using this new 4D tool, they can monitor and study the ionosphere as if they're actually inside it." Guhathakurta made his comments on the NASA Web site.

NASA understands that "[h]am radio operators know the ionosphere well. They can communicate over the horizon by bouncing their signals off of the ionosphere -- or communicate not at all when a solar flare blasts the ionosphere with X-rays and triggers a radio blackout." As radio amateurs, we use -- and depend on -- the ionosphere to make contacts.

Tobiska agrees: "For ham radio operators, this is a great application because it enables them to figure out what frequencies that are going to be available for communicating with any part of the world they want to communicate with at that moment in time. So ham radio operators who are in South Carolina want to talk to someone in Europe or Africa, they can know exactly what frequencies to turn to on their dial."

Luetzelschwab explained that this figure shows the six parameters that can be superimposed on the Google Earth image.

They are foF2 (the F2 region ordinary wave critical frequency), MUF (maximum usable frequency of the F2 region, which is approximately three times foF2), MUF animation (you can select any time in the 24-hour period), RA (radio availability), TEC (total electron content, which is the total number of electrons in a vertical column going up through the ionosphere) and TEC animation (also selectable for any time in the 24-hour period).

All six parameters in the figure are for a time around 2300 UTC (7 PM local in the Eastern Daylight Time zone) on May 2, and depict the ionosphere in the North American and South American sector.

"Looking at the MUF image (the middle image in the top row) indicates the MUF on a path from the East Coast of North America to Europe at the indicated time is anywhere from 8-15 MHz (green) on the North America end and from 3-8 MHz (blue) on the Europe end," he said.

"That certainly doesn't pin it down too well, but it does give a broad view of the ionospheric conditions along that path. Also note that the robust equatorial ionosphere, with its concentrated areas of high electron density on either side of the geomagnetic equator, is readily seen."

Luetzelschwab said he personally believes that "The importance of this new product is the fact that this is likely the first physical model of the ionosphere available to the widespread Amateur Radio community.

This is in contrast to the model in our current propagation predictions -- such as VOACAP, W6ELProp and the like -- that is based on years of measured ionospheric data correlated to a proxy for the true solar ionizing radiation (the proxies being sunspots and 10.7 cm solar flux)."

NASA explained that it appears that this new physical model takes satellite measurements of solar radiation at extreme ultraviolet (EUV) wavelengths (the true ionizing radiation) and inputs this data, along with a geomagnetic field activity index, into a model of the atmosphere to determine electron densities. Luetzelschwab said "Yes, it only offers a broad view now -- but I think it is a sign of things to come."