[time-nuts] Re: BOAT ionospheric effects

[Bob kb8tq]

Hi

Thanks !!!!!

There are a lot of devices that do “single band” GNSS for timing. 
The reason is pretty simple: cost. On those devices, you don’t get
the internal correction for atmosphere that you do on a multi band
device. 

So, the rephrased / corrected / enhanced question becomes: Are
single band issues likely in this case / did anybody see them?

Thanks again,

Bob

> On Oct 22, 2022, at 6:58 AM, Phil Erickson via time-nuts <time-nuts at lists.febo.com> wrote:
> 
> Hi all,
> 
>  John Ackermann mentioned this thread.  I'm an ionospheric observational
> physics person.
> 
>  The disturbance from a gamma ray flare is primarily on VLF propagation
> (10s of kHz) because it penetrates so low in the atmosphere and enhances
> the "sub-D region" between 40 and 80 km or so.  D region is highly
> absorptive due to strong ion-neutral collisions in events where it gets
> enhanced.
> 
>  VLF ionospheric propagation effects from gamma ray bursts weren't really
> confirmed until this 1988 Nature paper by Fishman and Inan on a strong 1983
> burst:
> 
> Fishman, G. J., and U. S. Inan. "Observation of an ionospheric disturbance
> caused by a gamma-ray burst." Nature 331, no. 6155 (1988): 418-420.
> https://www.nature.com/articles/331418a0.pdf?origin=ppub
> 
>  There are a number of publications since that one.  Because VLF paths are
> inherently transcontinental and interhemispheric in the earth-Ionosphere
> waveguide (ground to bottom of the D region), this was seen only on a very
> long path reception.  Check out Figure 2 - I think that's one of the
> reasons why it took so long to conclusively identify it - as they say:
> 
> "Figure 2 shows a portion of the record from the three stations between
> 21:40 UT and 23:00 UT on 1 August 1983. A clear indication of a disturbance
> beginning at 22:14:10±10UT is seen in the radio station GBR signal. Weaker,
> barely detectable decreases in amplitude are seen simultaneously in the two
> other signals. Without the GBR signal, these other two signals alone would
> have been considered uneventful as similar weak fluctu- ations are seen in
> their records near the time of the burst. The disturbance in the GBR signal
> differs in its rise-and-fall time from any other disturbances seen within
> 60 h of the burst."
> 
>  So identifying the spike using multiple simultaneous receptions was
> needed to disambiguate it from something like whistlers (lightning), flares
> (SIDs), etc.  The SpaceWeather article that Bob KB8TQ mentioned shows a
> similar type of detection of the recent super-GRB.
> 
>  Back to the topic though: the ionization deposit would be very wide
> spread (not localized) and would however I think contribute not very much
> to the total electron content (TEC), which is of course the critical thing
> for dual frequency GNSS measurements at L band.  The way I could see
> something occurring is if irregularities were created in the region of
> enhanced ionization, but they wouldn't last too long.
> 
>  Consider also that the ionosphere's natural electron density variability
> is 1 to a few % on any day of the year, and you can see this clearly in
> differential TEC from things like traveling ionospheric disturbance (TID)
> waves and the like (many many studies).  Those don't significantly impact
> timing solutions due to the dual frequency nature of the GNSS system which
> subtracts out ionospheric delay, so I can't imagine this event would change
> those either.
> 
>  Of course, I could be wrong - please correct!
> 
> 73
> Phil W1PJE
> MIT Haystack Observatory
> Westford, MA
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