[TangerineSDR] [HamSCI] Lightning Stroke/TLE Analysis with VLF Receiver (Post with Missing Images)

Sun Jan 29 10:20:05 EST 2023

Where in Maryland would you locate one?

Bob
N4HY

On Fri, Jan 27, 2023 at 12:41 PM Jonathan <emuman100 at gmail.com> wrote:

> Kerry,
>
> ELVES and sprites occur in the mesosphere above thunderstorms.
>
> Gerry,
>
> I'm still looking to create a network of VLF receivers and one of the
> functions would be lightning location. Other than impulse duration, what
> are the characteristics of a CG and intracloud stroke at VLF and how would
> distance from the receiver affect that? The vlfrx-tools software I use is
> very versatile in terms of signal processing, so what were you looking to
> do?
>
> Jonathan
> KC3EEY
>
> On Fri, Jan 27, 2023 at 10:35 AM Gerald Creager <gcreager at cap.gov> wrote:
>
>> Jonathon,
>>
>> Your network of receivers is similar in concept to the network I
>> presented several years ago at the TAPR DCC. Let's talk. Your ELF tail and
>> EVLE work suggest some things to me. A lot of work has been done in other
>> spectral ranges than VLF, and there are data to capture at higher
>> frequencies. Think "Citizen Weather Observer Network" but for lightning.
>> I've also got some ideas on central processing for geolocation for GC and
>> CC/IC impulses.
>>
>> 73
>> Gerry N5JXS
>>
>> Maj Gerry CreagerNational Health Services Advisory TeamCivil Air Patrol, U.S. Air Force Auxiliary
>>
>> (M) 979.229.5301
>>
>> GoCivilAirPatrol.com <https://www.gocivilairpatrol.com/>
>>  <https://www.gocivilairpatrol.com/>
>>
>> Volunteers serving America's communities, saving lives, and shaping futures.
>>
>>
>>
>> On Fri, Jan 27, 2023 at 7:35 AM Jonathan <emuman100 at gmail.com> wrote:
>>
>>> Sometimes lightning strokes produce what are called transient luminous
>>> events, or TLEs. They are commonly known as sprites and jets. Not much is
>>> known about them but they are continuously studied. Columns and regions of
>>> atmosphere are ionized so much by the electric potentials caused by the
>>> lightning stroke that the air glows red. It’s present for a split second
>>> when the stroke occurs, so you need a quick eye and a camera to capture an
>>> image. Many enthusiasts who capture these beautiful events often use timed
>>> video and photography and use lightning stroke data to identify the
>>> specific lightning stroke, its channel current, and polarity. The "channel"
>>> is the conductive channel of ionized air where lightning current either
>>> flows upwards or downwards. VLF receivers detect the radio emissions from
>>> lightning strokes, called sferics. The sferic signal characteristics are
>>> fed into models that calculate stroke polarity and channel current.
>>>
>>> An enthusiast and photographer, Paul, captured a double TLE, showing
>>> both a sprite (the dendritic structure) and an ELVE (the upper dim region
>>> of red glowing air above the sprite). ELVEs are often, but not always,
>>> indicative of what is called a "continuing current", or a residual current
>>> flowing through the channel with ELF frequency components.
>>> [image: thumbnail1.png]
>>>
>>> Using a VLF receiver connected to a soundcard and vlfrx-tools software,
>>> it is possible to look at the sferic's impulse in a time domain plot. A
>>> continuing current will often show up as an "ELF tail" right after the
>>> initial impulse. This tail has ELF frequency components and is indicative
>>> of that "little wavy line" after the sferic's impulse. The plot below shows
>>> the sferic from the stroke that created the TLE above. The ELF tail is hard
>>> to see because it has some high frequency components on it, but it is
>>> there. Running the following signal processing chain in vlfrx-tools
>>> software produced the plot below:
>>>
>>> vtread -T2022-12-14_02:09:20,+30s /data/vlf_96k | vtfilter -a th=5 |
>>> vtresample -r32000 | vtcat -T2022-12-14_02:09:38.2,+0.1 | vtplot -t "+266kA
>>> Stroke Nice Sprite/ELVE Combo"
>>>
>>> [image: thumbnail2.png]
>>>
>>> The farther the VLF receiver is from the lightning stroke, the longer
>>> the ELF tail is. If this stroke occurred in Europe, it would be much
>>> longer, but it was captured in the US, closer to the VLF receiver. Here is
>>> another example of an ELVE:
>>> [image: thumbnail5.png]
>>>
>>> This is the time domain plot with the ELF tail easier to see because
>>> there are much less high frequency components:
>>> [image: thumbnail3.png]
>>>
>>> In recording these millisecond events, it is essential to use precision
>>> timing, which is why I use a GPS receiver to enable accurate and precision
>>> timestamping. I used the signal processing chain above to pull the spectrum
>>> data from the data store, filter out mains hum, resample to 32k to remove a
>>> lot of high frequency components, then feed the specific spectrum chunk
>>> into the plotting program.
>>>
>>> With vlfrx-tools software and a network of VLF receivers, you can do
>>> lightning location as well. Here is a lightning map from a network of VLF
>>> receivers in India:
>>> [image: pn221206a.png]
>>>
>>> The red dots indicate the location of a stroke and the circles indicate
>>> VLF receiver locations.
>>>
>>> Eventually, I would like to have a network of VLF receivers collecting
>>> sferic data for lightning location.
>>>
>>> Jonathan
>>> KC3EEY
>>>
>>> --
>>> Please follow the HamSCI Community Participation Guidelines at
>>> http://hamsci.org/hamsci-community-participation-guidelines.
>>> ---
>>> You received this message because you are subscribed to the Google
>>> Groups "HamSCI" group.
>>> To unsubscribe from this group and stop receiving emails from it, send
>>> an email to hamsci+unsubscribe at googlegroups.com.
>>> To view this discussion on the web visit
>>> https://groups.google.com/d/msgid/hamsci/CAOY0kB1ObgqciLJcBmJKJuq2VpxdJ7n-C%2BQeQbCx-pSMOXa4qA%40mail.gmail.com
>>> <https://groups.google.com/d/msgid/hamsci/CAOY0kB1ObgqciLJcBmJKJuq2VpxdJ7n-C%2BQeQbCx-pSMOXa4qA%40mail.gmail.com?utm_medium=email&utm_source=footer>
>>> .
>>>
>> --
>> Please follow the HamSCI Community Participation Guidelines at
>> http://hamsci.org/hamsci-community-participation-guidelines.
>> ---
>> You received this message because you are subscribed to the Google Groups
>> "HamSCI" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to hamsci+unsubscribe at googlegroups.com.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/hamsci/CAG3zga4uy-pmvv_K2BhxxDF9OAijw1VRdehqi0YaLsVAW4XueA%40mail.gmail.com
>> <https://groups.google.com/d/msgid/hamsci/CAG3zga4uy-pmvv_K2BhxxDF9OAijw1VRdehqi0YaLsVAW4XueA%40mail.gmail.com?utm_medium=email&utm_source=footer>
>> .
>>
> --
> Please follow the HamSCI Community Participation Guidelines at
> http://hamsci.org/hamsci-community-participation-guidelines.
> ---
> You received this message because you are subscribed to the Google Groups
> "HamSCI" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to hamsci+unsubscribe at googlegroups.com.
> To view this discussion on the web visit
> https://groups.google.com/d/msgid/hamsci/CAOY0kB2HPk9jxq7Gc-9J9CFPjS1mFLeVQEsc-jSFtFJFi5jKXg%40mail.gmail.com
> <https://groups.google.com/d/msgid/hamsci/CAOY0kB2HPk9jxq7Gc-9J9CFPjS1mFLeVQEsc-jSFtFJFi5jKXg%40mail.gmail.com?utm_medium=email&utm_source=footer>
> .
>
-- 
Dr. Robert W McGwier, Ph.D.
Adjunct Faculty, Virginia Tech
Affiliated Faculty, University of Scranton
ARDC Member of Board
N4HY: ARRL, TAPR, AMSAT, EARC, CSVHFS
Sky: AAVSO, Sky360, explorescu.org, Skyscrapers
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20230129/0f2ceff1/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: thumbnail1.png
Type: image/png
Size: 404684 bytes
Desc: not available
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20230129/0f2ceff1/attachment-0005.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: thumbnail5.png
Type: image/png
Size: 234514 bytes
Desc: not available
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20230129/0f2ceff1/attachment-0006.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: thumbnail2.png
Type: image/png
Size: 10735 bytes
Desc: not available
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20230129/0f2ceff1/attachment-0007.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: pn221206a.png
Type: image/png
Size: 63772 bytes
Desc: not available
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20230129/0f2ceff1/attachment-0008.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: thumbnail3.png
Type: image/png
Size: 8457 bytes
Desc: not available
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20230129/0f2ceff1/attachment-0009.png>