Probing the Terrestrial Ionosphere

Hello fellow physics buff and web surfer!  Every day our planet is bombarded by energetic debris which was once part of the Mass of our Sun.  As the Sun 'burns' it sends particles of  'solar ash' streaming out spherically in all directions.  These particles move out into our solar system and the Earth's orbit sweeps through this path of debris.  Due to giant solar flares and sunspots this 'dust stream' is constantly changing and moves with a varying velocity of less than 200 to over 600 kilometers per second, with densities ranging from under 2 to over 8 protons/cm3.  As the Earth passes through this solar windstorm, our planets' natural magnetic poles deflect the paths of some of this debris; (concentrated by the Earths' magnetic flux fields) some streams in close enough to interact with our protective atmosphere and causes the phenomenon that we call the
 Aurora Borealis
 
 

copyright 1995 jancurtis

 For an up to the minute summary of the solar winds, geomagnetic flux field changes, space weather storms forecasts, and an aurora report I enjoy the HAM radio based:   http://dx.qsl.net/propagation/index.html    These folks say they have "A dynamic collection of propagation information gathered from many different sources".  Be sure to examine the photos of the Sun exposed at differing light frequencies!

Some of the earliest radio pioneers realized that the propagation of their signals depended on electromagneticly reflective layers in the atmosphere.  It was determined experimentally that various frequencies are reflected at different angles throughout the ionosphere, and these signals will  travel to different locations around the earth. It was not long until the connection was made between varying propagation anomalies and the various cycles that our sun was known to go through.  We now not only study the ionosphere with amateur radio operators, but universities and  governments worldwide have committed resources to study propagation to enhance 'cave' radio, underwater communications with submarines, and of course orbiting data relay and 'spy' satellites.

The first continuous radio beacons gave birth to what is called the vertical ionosode.  Radio energy is beamed vertically and monitored for reflecting and scattering effects.  The equipment used has developed  into higher frequency components  with the advent of newer technologies.  Today frequencies are used up into, and even over, the visible light  frequencies.   Check out the LIDAR information right here at Poker Flats research range outside of Fairbanks. http://www.pfrr.alaska.edu/

 Ionospheric Heating is a technique where radio waves are concentrated on a specific point in the sky, and the RF energy tends to 'Heat' the area and increase the energy level of the ionosphere.  This changes the ionosphere much like a sunspot or solar flare.  Experiments are continuing "with particular emphasis on being able to understand and use it to enhance communications and surveillance systems for both civilian and defense purposes." ( http://www.haarp.alaska.edu/  )   The HAARP site has an excellent virtual tour , with lots of background information (see the general info section).  In addition you can access their data online in real time as they perform heating experiments, and most of the receivers are operated continuously monitoring the natural background radiation.

 Another technique is called 'Incoherent Scatter Radar'.  This method of ionospheric study came out of the cold war between the United States and the U.S.S.R.  Long range over the horizon RADAR sites originally used to monitor for incoming ICBMs are still transmitting,( http://superdarn.jhuapl.edu/) and the reflected signals are monitored for atmosphereic changes at the transmission site and several receiving stations throughout the world.  Some of this equipment is functioning so well that even gravitational changes can be detected. 
In addition to ground based methods, many hundreds of satellites are now orbiting our planet.  The very first manmade satellite, Sputnik I, was simply a beep- beep- beep radio transmitter used to study radio propagation down to earth from above.   These signals  were received by american ham radio operators  before our military  knew Sputnik was airborne.  The success of this flight paved the way for the systems of  GPS, television, and communications satellites that we use today.  To check the location of your favorite satellite, including the International Space Station  and Shuttle  ( when in orbit)  I like :    http://science.nasa.gov/realtime/JTrack/Spacecraft.html 
This site offers both a two dimensional 'customizable' satellite display, and a 3-D option that lets you view the entire earth and satellite orbits in real time.  By clicking on any of the 'dots' the satellite information will be displayed.

You may e-mail me:  fsrwj@uaf.edu