[TangerineSDR] Possible Lightning ELVES Detection

[Jonathan]

Hi All,

I wanted to clarify, this exercise is to analyze the sferic that contains
an "ELF tail". The VLF components of the sferic are cut off by the earth
ionospheric waveguide, but the ELF component can propagate, but it exhibits
some frequency dispersion.

I've used the sferics time of group arrival to extract some really
interesting information. I was able to determine the TOGA, but it's not
entirely accurate due to the GPS not functioning, however, some information
can be extracted. Here is a stacked plot of the data extracted from the
TOGA:

[image: 2022-05-31_07-43-28.73p0.04_sferic_ELF_tail_rerun.png]

Keep in mind, the VLF data was resampled to 32k, meaning frequency content
of up to 16 kHz is present in the data. Credit to the author of
vlfrx-tools for this amazing script that generated the stacked plots.

Jonathan
KC3EEY

On Fri, Jun 3, 2022 at 10:08 AM Jonathan <emuman100 at gmail.com> wrote:

> Hi All,
>
> A lightning ELVES event was visually observed in Kansas on May 31st, 2022
> and posted in a Facebook group:
> [image: ELVES 2.png]
>
> A negative 333kA stroke occurred which generated it. I believe I captured
> the sferic from that stroke based on the time indicated:
> [image: ELVES 1.png]
> Due to the VLF system having a malfunctioning GPS, the best I can do is
> NTP time, but the offset from actual UT is still pretty minimal. A
> characteristic of an ELVES if it has a "continuing current" is the ELF tail
> observed directly after the sferic, as seen in the plot I captured. The ELF
> tail is described in this paper
> <https://www.researchgate.net/publication/251436491_Evidence_for_continuing_current_in_sprite-producing_cloud-to-ground_lightning>.
> From what I understand, not all ELVES events have a continuing current. I
> have observed that these ELF tails ring out longer the longer the
> propagation distance. This can be seen in these plots
> <http://abelian.org/vlf/retrieve.php?ts=2022-05-31+07%3A43%3A28.7&len=.1&vlf1=on&vlf15=on&vlf34=on&vlf35=on&vlf38=on&vlf41=on&vlf44=on&format=td&submit=+Proceed+>
> of worldwide VLF receivers. The top two plots are VLF receivers in England
> and Italy, respectively. The receivers in Europe (top two plots) seem to
> have bigger ELF tails, which is expected.
>
> What do you all think? A possible ELVES detection?
>
> Jonathan
> KC3EEY
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20220613/ae4e9b03/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ELVES 2.png
Type: image/png
Size: 207977 bytes
Desc: not available
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20220613/ae4e9b03/attachment-0003.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: ELVES 1.png
Type: image/png
Size: 16513 bytes
Desc: not available
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20220613/ae4e9b03/attachment-0004.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: 2022-05-31_07-43-28.73p0.04_sferic_ELF_tail_rerun.png
Type: image/png
Size: 16052 bytes
Desc: not available
URL: <http://lists.tapr.org/pipermail/tangerinesdr_lists.tapr.org/attachments/20220613/ae4e9b03/attachment-0005.png>