The ionosphere is an ionized layer in the atmosphere roughly 50- 600 km above the Earth’s surface. Its ionization is caused by incoming UV and X-ray radiation from the sun. The degree of ionization increases with the amount of solar radiation received, and therefore tends to depend on the latitude, the season, and the time of day. Ionization is also dramatically affected by exceptional events such as solar flares and coronal mass ejections. The ionosphere is excellent propagator of radio waves.
Short wave communications such the BBC World Service are broadcast across the globe thanks to the ability of the ionosphere to carry radio waves beyond the transmitter‟s line of sight. , but the essential point is that short terms changes in the degree of ionization can be detected by monitoring the changing power of a distant radio signal that is being carried through the ionosphere, thus indicating the occurrence of solar storms. The kind of radio signal that we would like to monitor is ideally available all over the world, receivable at long range, and transmitted at constant power. Fortunately such a system exists. It is the Very Low Frequency (VLF) submarine communications network.
The VLF band at 3-30 kHz is used for submarine communications because only such low frequencies can penetrate through sea water to be picked up by submerged submarines. There are several dozen naval transmitters in use different degrees of ionization in the ionosphere above the Earth shows the dependence on incoming solar radiation.
One of the most powerful is the 24 kHz transmitter at Cultler, Maine, USA. Another powerful transmitter is the 22.2 khz transmitter at Ebino, Kuyshu. There are several more in Europe .
So our key goal is to build a mechanism to monitor this ionospheric disturbances on a specific VLF signal using just a VLF Antenna a signal amplifier, and a laptop with a 96kHz (Resampling audio 96000 -> 48000) sample rate sound card.
Projects details and results coming soon.