The image below is a time-frequency spectrogram, which shows the frequency
content of signals recorded by the
HAARP Induction Magnetometer.
This instrument, provided by the University of Tokyo, measures temporal variations
in the geomagnetic field in the ULF (ultra-low frequency) range of 0-5 Hz. The
spectrogram images are produced by computing the PSD (power spectral density) of
successive 102.4-second segments of timeseries data, and plotting these spectra as
color/intensity slices along a 24-hour scale.
If the images below is not too interesting, you might want to look at
02 Sep 2004 for an example of
narrowband PC1 pulsations, or
27 Jul 2004 for an example of
wideband ULF noise during a magnetic substorm.
Expanded plots of the
last 12 hours,
last 6 hours,
last 3 hours, and
last 1 hour are also available.
Questions of a technical nature may be submitted
via e-mail to:
