Determining lightning polarity (positive or negative) by raw signal processing?

[RichoAnd]

Good idea Tobi 

[readbueno]

Hi All, I agree with Richo. They are selling their system and using semi-technical "explanations" to sell this to people that have even less knowledge.

"Though the antenna shows receiving capability up to about 1 MHz, an upper limit is
set to 400 kHz in order to serve anti-alias properties, and a digital filter can be adjusted
in the range 100-400 kHz in order to reduce influence of radio signals; the wave form
distortion due to the actually chosen band-width limitation remains acceptable for the
present purposes.
Signal timing is achieved by means of a separately mounted commercial GPS clock
with an accuracy of 100 ns (initially 300 ns, module 2). Special measures are taken
to transport this level of basic accuracy as far as possible to the actual event timing.
Signal amplification, filtering, AD-conversion and data processing are performed with
a single plug-in card (module 3) in a remotely positioned standard PC (module 4).
The effective sampling rate was set to 1 MHz and incoming signals are recorded with
14 bit resolution in a continuous mode. Triggered events are transferred to and processed
in a parallel unit so that no data loss occurs and no allowance for rearm time
must be provided (zero deadtime). Signal rates of up to approximately 1 kHz can be
handled. Each station collects data and transmits packets of condensed information
to the central station at Garching. Depending on the type of chosen line-connection
this transmission can take place immediately after completion of an individual signal
analysis, or within pre-selected time intervals for a group of signals which has been
accumulated within this interval. Due to transmission line band width the transfer is
presently limited to some 100 signals/s which is plenty even during strong thunderstorm
activity."
(Geophysical Research Abstracts, Vol. 7, 00685, 2005
SRef-ID: 1607-7962/gra/EGU05-A-00685
© European Geosciences Union 2005
Modern Lightning Detection and Implementation of a
New Network in Germany
H.-D. Betz, W. P. Oettinger, K. Schmidt, and M. Wirz
Physics Department, University of Munich, D-85748 Garching, Germany)

We are actually doing things far better, our timing is order of magnitude better, 10ns, and our reduced bandwidth does not have to deal with broadcast and military stations and other sources of interferrence that exist in the LF/VLF band that they profess to be using (Up to 1 MHz?)
I am also not certain that the vertical radiation pattern of a loop type antenna is sufficient to deal accurately with the difference in height between C to C and C to G type lightning.
A multi-antenna system is better.
For Europe especially Germany we have a better network density with more stations used in the detection and location of strokes, in another part of this document they talk of a delay time between being able to calculate individual strokes, therefore they are not actually recording all the strokes.
The internet speed and the computing power and timing accuracy has also increased and we are constantly updating our algorithm.
We do not suffer from commercial inertia, therefore if we have not already done so, eventually we we will overtake them and our system will be better.
Analyzing data is always the bottleneck, I read that NASA has accumulated data from the various space probe missions that even if it stopped now would take over 15 years to be reviewed and analyzed.

Brian.

[ThunderStorm]

It will pass some time until I can mount a E-field antenna on my system red in Romania, but I just started deploying a linux-based virtual machine where I can do some tests.

For now, I started downloading the signals from all red and blue stations in Germany (to record at least 2-3 days of signals and strikes) and will start analyzing the strikes/signals with Tobi recommendations.

[pasense]

I have received a signal from a lightning which saturated one of the H channels. Data from the european lightning detection network EUKLID could be correlated with this ligthning, it was a very strong negative lightning with -144 kA strength. The E field channel (magenta trace) goes POSITIVE in the first peak of the signal, so this is the signature for negative CG lightning. Positive CG lightning will first go negative in the E field channel.

[cutty]

I have received a signal from a lightning which saturated one of the H channels. Data from the european lightning detection network EUKLID could be correlated with this ligthning, it was a very strong negative lightning with -144 kA strength. The E field channel (magenta trace) goes POSITIVE in the first peak of the signal, so this is the signature for negative CG lightning. Positive CG lightning will first go negative in the E field channel.

That would be an interesting observation... if it proves consistent. Using the attached correlation E with Channel C ...(E signal in phase with A and B, trust me,)  which of the following random "sferics" might be "Positive" sferics? Why?  (Just assume they're all strokes, not junk)...

[RichoAnd]

Observations from long distance are not relevant, as they can be reflections :-)

/Richo

[cutty]

Observations from long distance are not relevant, as they can be reflections  :-)

/Richo

Exactly.... and which channel is referenced for phasing?

http://onlinelibrary.wiley.com/doi/10.10...10294/full

Positive Ground strokes tend to single discharge events... negative tends to multiple discharges. even tthat rule of thumb isn't always valid....

https://www.ikhebeenvraag.be/mediastorag...liksem.pdf

[pasense]

Richo, 
I used the very beginning of the signal, so this cannot be a reflection which is contributing only later to the signal. The line of sight from the station to the stroke was only over the sea, so the ground wave had little attenuation. I will try to get the opinion of lightning location specialists on this topic (identification of polarity for distant strokes).
Cutty, there was another stroke only 40 msec later at the same postition, so this is consistent with a negative stroke. Positive CG has only very rarely a second stroke at exactly the same position. A problem with +CG is that these waveforms are more complicated than -CG because very often there is significant cloud discharges before the return stroke. Sometimes this even leads to strong +CG not being identified correctly, instead a cloud discharge is assumed by the system.
What do the colors in your attachments stand for?

[pasense]

Assuming  the magenta channel is the E field and the yellow one the H field, this is my tentative identification:

Positive query huh
unclear -CG
unclear -CG
+CG     -CG
-CG ??  -CG
unclear +CG
-CG      -CG

positive query huh2
+CG    +CG
unclear -CG
+CG    +CG
-CG     +CG
unclear unclear
unclear +CG

I used the polarity of the first part of the E field signal, when I could identify the start. When the first pulse of the E field is positive I identify it as -CG, when it goes negative as +CG. This is then in line with the signal I presented above.
I would have prefered to see the horizontal H signals as well to get a better idea of the start, the signal of the  C channel is a bit weak.

[cutty]

Assuming  the magenta channel is the E field and the yellow one the H field, this is my tentative identification:

Positive query huh
unclear -CG
unclear -CG
+CG     -CG
-CG ??  -CG
unclear +CG
-CG      -CG

positive query huh2
+CG    +CG
unclear -CG
+CG    +CG
-CG     +CG
unclear unclear
unclear +CG

I used the polarity of the first part of the E field signal, when I could identify the start. When the first pulse of the E field is positive I identify it as -CG, when it goes negative as +CG. This is then in line with the signal I presented above.
I would have prefered to see the horizontal H signals as well to get a better idea of the start, the signal of the  C channel is a bit weak.

Correct on Yellow being H C, and Magenta is E... this should be the standard...
I threw a curve, "Huh2" is simply 'Huh" inverted and mirrored.,... same signals... just diddled. Done to illustrate the possible difficulty of the premise....and if we only 'compare' one H channel,  than the 'missing' A and B channels are irrelevant for this illustration of channel vs channel... My experience with both RED and BLUE indicates that E is almost always In phase with one or more channels...

Sol, if we're looking for the 'out of phase' H vs E.... which H channel should we use as H ref?