atural radio emissions in the frequencies between the very
low frequency (VLF) and extremely low frequency (ELF) regions have been given
evocative names such as "whistlers", "dawn chorus", "geese", "trains", and
"cows", that describe the sound made when the signal is heard through a speaker.
These sounds are produced by lightning bolts and other natural electromagnetic
impulses as they propagate over long distances with differential velocities at
different frequencies, a phenomenon known as dispersion. Whistlers and chorus
have not only been heard on Earth; similar atmospheric electromagnetic signals
have been detected on Jupiter,
Saturn , Neptune, and Uranus as well. These signals can give important
information about the magnetosphere and upper ionosphere. This book, based
on a scientific conference on the subject held in India, describes the
geomagnetic phenomena responsible for these fascinating radio phenomena,
concentrating mainly on whistlers.
Very Low Frequency Phenomena
A.R.W. Hughes, C. Ferencz, and A.K. Gwal, eds.
Narosa Publishing House, 2003, 367 pages
Unfortunately, the publishing quality of this book is extremely poor. Many
of the figures are completely illegible, and most of the spectrograms
have lost most of their original information by having been reduced from
color to low-resolution newsprint-quality grayscale. On some pages, part of
the printing is too light or smudged. The equations are badly typeset. There
is no index. Some of the figures are printed crooked. More importantly, many
of the articles in the book are uninspired, scientifically unconvincing, and
in serious need of checking by a native speaker of English.
To get a much better idea of the excitement of this field, you would be better
off visiting the Italian VLF website at www.vlf.it.
VLF phenomena are a great topic for a book; hopefully in the future there will
be one that does better justice to this fascinating subject.
September 11, 2005