VV(13) - Sferics

[David Morris]

http://www.ibmpcug.co.uk/~irdial/sferics.htm

Sferics are the snap, crackle, and pop of lightning-stroke electromagnetic 
impulses from lightning storms within a couple thousand miles of the 
receiver; the more powerful the lightning stroke or the closer it is to the 
VLF receiver's location, the louder the pops and crashes of sferics will 
sound in the headphones. Several million lightning strokes occur daily from 
an estimated 2000 storms worldwide, and the Earth is struck 100 times a 
second by lightning. At times the receiver's output is a cacophony of 
crackling and popping sferics from lightning strokes originating in storms 
near and far.

These huge sparks of lightning strokes are powerful sources of 
electromagnetic (radio) emission throughout the radio frequency 
spectrum--from the very lowest of radio frequencies up to the microwave 
frequency ranges and the visible light spectrum. However, most of the 
emitted electromagnetic energy from lightning is in the very lowest part of 
the radio spectrum, from 0.1 to 10 kHz. The radio pulses produced by 
lightning strokes travel enormous distances at these very-low radio 
frequencies, following the surface of the Earth as "ground waves." It is 
interesting how generally quiet and lightning sferic-free the hours are from 
just after sunrise to mid- morning, when thunderstorms tend to be at their 
minimum. Later, the crackling and popping of lightning sferic activity picks 
up as afternoon thunderstorms build in numbers and intensity. Weather 
monitoring agencies employ special receivers and direction-finding equipment 
in order to determine where lightning strikes are occurring and the 
potential for wildfire ignition, hazards, to aviation, and damage to 
electric power utilities from those lightning strikes.

http://theramp.net/sferics/

The electromagnetic radiation from severe weather formations (sferics) has 
been studied with emphasis on the relative distribution of event (pulse) 
characteristics. Factors measured include: pulse shape, pulse polarity, and 
relative timing between events of a burst (multiple pulses in a short period 
of time). All events have been analyzed with reference to 
direction-of-arrival. Several recurring patterns have been observed in the 
spectral distribution of these factors as the severity of the weather 
changes. The relative timing patterns, which have been monitored for many 
years, have shown positive correlation with severe weather. The polarity and 
pulse shape data has produced recurring patterns but correlation with severe 
weather has not been resolved at this time.

http://sfericsmusic.com/

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