Gravity Wave?
November 24, 2002
July 1, 2002

On July 1st, 2002, the ELFRAD detection system recorded an anomaly whose amplitude reached a peak at 1319 UTC time. A scan of various magnetometers around the world did not record anything unusual. solar X-ray intensity was normal and no unusual ionospheric effects were noted. A highly unusual solar prominence was detected  however at this time and photographed by the SOHO satellite. The solar eruption, was more than 240,000 miles long, and burst from the surface of the sun as the satellite had its cameras trained on the sun. 

The explosion was what astronomers call an eruptive prominence, a loop of magnetic fields that trap hot gas inside. As the trapped gas becomes unstable it erupts violently into space. If eruptions like these are aimed at Earth, they can disturb the magnetosphere, the planet's magnetic field, with dramatic consequences. Past eruptions have knocked out satellites, wrecked television reception and caused power surges and blackouts, but this one was fortunately not aimed at us. 

prominence.jpg (39241 bytes)
Click to enlarge

Todd Hoeksema, solar astronomer at Nasa, said: "This was quite a large eruption and they are pretty spectacular. The material goes out into space, and if it is heading towards Earth it will hit our atmosphere and disturb the magnetic field. "It can damage satellites and sometimes means planes flying over the poles have to be re-routed, because it interferes with communications equipment."

Researchers worldwide have been searching for evidence of gravity waves for years. For instance, scientists and students at Caltech are in the process of building a Laser Interferometer Gravitational Wave Observatory to try to detect the existence of these waves.

It has been discovered the ELFRAD detection system may be capable of recording Gravitational Waves. The antenna array is constructed is such a way that the earth itself is used as the antenna. The detectors electrically record ultra small voltage and current variances at extreme ULF frequencies.  Wavelengths many millions of miles long with periods measuring 8 to 10 hours have been recorded and analyzed. During the July 1st incident, a ULF wave at a frequency of .016 hertz was recorded by our system.  It is theorized that a gravity wave was generated by the July 1st event and detected by ELFRAD. The mechanism of propagation is not known,  however this eruption was recorded at the same instant as the SOHO camera which photographed the prominence.

solarfft.gif (17516 bytes)
Click to enlarge

The graph above indicates the amplitude of the signal which was low pass filtered at .018 hertz. It clearly shows the extreme influence of the passing wave and the maximum peak beginning at 13:16:44 and ending at 13:20:34 for a duration of 3.49 minutes. 

It is believed the mechanism of detection consisted of the detection of voltages and currents generated when the gravity wave passed through crystalline material of the earth,  causing a piezoelectric effect. The antenna array is coupled directly to  earth between two distant points which measured 1000 feet, or approx. 300 meters. Small current changes which are propagated through the earth are then measured and recorded.

The three graphs below indicate first, an analysis of the wave using an infinite impulse filter (IIR) with a bandwidth from .015 to .018 hertz.  Secondly, an FFT analysis showing the main frequency to be at .016 hertz. The third chart indicates the magnetic conditions which existed at the time. This chart was obtained from Kiruna, Sweden.

solariir.gif (19048 bytes)

freqfft.gif (6846 bytes)

july1ast.gif (8511 bytes)
Click on pics to enlarge

If gravitational waves prove to exist, then we at ELFRAD may be the first to detect and record this phenomenon. Now that we know of a possible condition when these waves may be generated, we should be able to record others.

Charlie Plyler