HAARP

The chart normally shows several bands of bright colors corresponding to strong international broadcast stations operating in various frequency ranges, such as the 41 meter or the 25 meter band. On days when these bands are missing or when the bands contain "cooler colors" ionospheric propagation conditions are poor, possibly due to a geomagnetic storm. The onset of such a storm can often be seen in the chart as the abrupt termination of a color band into the blue background. An example of a minor absorption event (or fade-out) is seen in the chart at approximately 1100 UTC. The fade-out lasts only for a short time and propagation returns to normal after about 1130 UTC. On such occasions, it is interesting to compare the HF waterfall chart with other data such as the HAARP Riometer and Magnetometer charts.

The higher frequencies (in the upper part of the chart) are usually devoid of signals during the low part of the sunspot cycle since higher frequencies need a higher degree of ionization to propagate. When frequencies above 20 Mhz are present in the chart, it is indicative of increased solar activity.

Other interesting aspects of the chart are explained in the following notes from the chart above:

1. Higher frequencies require greater ionization. As solar activity increases, additional signal should appear in this region.
2. There are superfluous, constant signals present in the data. They are due to local sources at or near the HAARP site, such as computer clock oscillators.
3. Vertical white space results from gaps in the data, usually caused by power failures.
4. The white line drawn on the chart shows the trend for strong signals to move toward shorter time intervals as the frequency decreases. This is a consequence of the effect of the "D" layer which absorbs or attenuates lower frequencies. The "D" layer disappears during the evening hours and, in the chart above (for May 29, 1997), the sun is below the horizon for only a brief period of time.
5. Strong signals are observed in the upper part of the standard AM broadcast band (up to 1600 kHz). These signals originate, for the most part, in the northwestern US and reach the HAARP site through multiple sky wave reflections. The effect of the "D" layer on these signals is quite pronounced.