The word riometer stands for Relative Ionospheric Opacity Meter
http://137.229.36.30/cgi-bin/riometer/riom2_sel.cgi?endTime=20110825&pwidth=36H&absorb=on&meas=on&qdc=on&pstyle=log
http://137.229.36.30/cgi-bin/riometer/riom2_sel.cgi?endTime=20110825&pwidth=36H&absorb=on&meas=on&qdc=on&pstyle=log
HAARP VHF RIOMETER
The chart below is a plot of the readings taken using the HAARP VHF Riometer. This instrument is a sensitive receiver tuned to a frequency of 30 MHz. The antenna is an array of 4 element "yagi" type elements pointed directly upward to listen to the background or galactic noise. This noise varies from one hour to the next as the Earth rotates and, in the absence of ionospheric absorption, is a constant, repeatable function of Local Siderial Time. Over many observations, it is possible to develop a "quiet day" curve which represents the greatest noise that would be heard for any given hour of the day. By comparing the current noise measurement with the quiet day level, the current 30 MHz ionospheric absorption level can be derived and this number is shown in the figure. Solar-terrestrial events, such as geomagnetic storms are usually indicated by increases in the absorption level. The absorption at lower frequencies in the HF band is usually much higher than the level observed at 30 MHz. Occasional spikes in the received signal that go above the quiet day curve are caused by interference from broadcast signals in the 30 MHz band. Click here for a larger plot without this text.
