Solar Flare Monitor

Paul Mortfield

This homebrew device can detect solar flares and CME's by their impact on the Earth's ionosphere by measuring a SID or Sudden Ionospheric Disturbance in the D-layer of the ionosphere. The device is tuned to monitor a distance VLF (Very Low Frequency) radio station run by the US Navy for talking to submarines. My unit is tuned to 24.8 KHz which is station NLK in Washington State. During a solar event a change in the signal is detected with a unique signature of a sudden rise with a slow decay and looks more like a shark fin on the output graph. The size of this shape is dependent on intensity of the flare and position of the sun in the sky.

You'll also notice a unique sunrise pattern when the D-layer gets formed during the daylight hours. Because of the very low frequency of this detector, is susceptible to electrical interference. It can easily pick up spark type noises like local lightning storms or dimmer switches or the neighbor's TV set. Fortunately those have different signatures than the flares. Times are in UT.

The antenna currently is a 1.5 meter diameter loop of 14 gauge household wire from Home Depot wound around a simple PVC frame. The antenna is then fed into a small set of electronics then an A/D converter to an old PC running 24/7 dedicated to this task. The antenna is pointed towards the transmitter which in my case is north along a wall in the house.

Here are some traces of activity from last week (May 27-June2, 2003) which produced some pretty intense events. The previous two weeks were pretty quiet until this active region popped around onto the solar disk. Notice all the activity on May 28. (click on the traces for even larger version).