Lightning detection and mapping in real time wwlln.net blitzortung.org Björn Pehrson <bjorn@pehrson.se> SA0BXI Systems, Makerere University 2016-09-02

Sferics Wide spectrum EM-pulse created by lightning VLF energy focus 3-30kHz Stations receiving pulses stamp and report time of arrival (toa) and own location, using gps clock and position, to regional servers Regional servers compute pairwise toa differences defining a hyperbolic curve. Lightning position is where these curves intersect

The sferic pulse The main challenge is to identify the pulse to assign a time of arrival. Not to destroy the pulse character, there should be no resonance under 30kHz in the VLF receiver.

Calculating lightning position You need at least four stations to define the three curves required to get a unique intersection point Provided that the resolution and accurrace in the time stamps are high enough. With more stations you can deal with lower accuracy

E and H antennas Lightning striking between cloud and ground creates an EM pulse wih a vertical electric component (E) and a horisontal magnetic component (H) A vertical metal rod antenna is used to capture the E-component A shielded loop or coiled ferrite rod antenna is used to capture the H-component

References wwlln publication list http://wwlln.net/publications/ "Long-range tracking of thunderstorms using sferic measurements," T. G. Wood and U. S. Inan, Stanford University STAR Laboratory, Stanford, California, USA, published in JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 107, NO. D21, 4553, doi:10.1029/2001JD002008, 2002, available at http://nova.stanford.edu/~vlf/publications/526.pdf Wavelet analysis of sferics http://vlf.stanford.edu/research/wavelet-analysis-sferics wwlln.net Blitzortung.org