Friends in Top Band Land,
I now have a response from Dr. David S. Evans of NOAA (on leave now at
NASA) in regard to satellite observations during the period of interest on
March 20. These observations were made by the electron detectors on the
NOAA/TIROS satellites that are also responsible for the auroral activity
displays you see on the NOAA Web page on the Internet. The orbits are in
the 90 minute range and two satellites provide the data.
The data is in the form of hemispheric power input of electron fluxes in
the energy range from 0.3 keV to 17.5 keV. The power inputs range from
less than 2.5 Gigawatts (GW) for K-values less than 1 to over 500 GW for
severe storm conditions (K=8-9).
For the period of interest, around 1000Z-1100Z on March 20, there was one
observation, 17.8 GW at 1041Z. For the two-day period, March 20 through
March 21, hemispheric power input ranged from a low of 5.7 at 0537Z on
March 20 to a high of 202.7 at 1611Z on March 21.
For the period of March 20 up to the time of the signal echoes noted
by K1ZM, the hemispheric power input averaged 24.1 GW. That is comparable
to the average power input of 16.8 GW during the entire VK0IR DXpedition
when the average Ap was 6.4 for a time of relative magnetic quiet.
On that basis, there would seem to be no extreme conditions with regard
to auroral energy influx for the period of interest. On the other hand,
the next day, March 21, was one of magnetic and auroral activity, with high
hemispheric power inputs, as noted above.
Beyond these numerical results, Dr. Evans gave the following comments
in response to my request for a review:
"The oscillation between high and low powers early on 3/21 were cases
where the particle precipitation on the day-side of the polar regions
(northern hemisphere) was unusually intense and the night-side auroral
activity (southern hemisphere) had not responded to the extent one
would normally expect. The estimated powers during the midday period
on 3/20 are above the long-term averages but not so high that you would
write home about them. The period post-noon on 3/21 is a storm time
(although late morning in the central US) but still well below my
record power estimate of 600+ GW."
"I looked at the 30 keV and 300 keV electrons throughout the orbits on
3/20 and 3/21. There was nothing of note on 3/20. 3/21 was a
different story. Later (after 1800) on 3/21 there were elevated fluxes
of >30 keV electrons - by a factor of 10 or more over normal - at
geographic latitudes down to the central US."
Those remarks indicate that the detectors were capable of picking up any
unusual conditions in the central US on March 20 and none were found. So
that would seem to lay to rest the idea of auroral ionization south and/or
west of K1ZM. Sporadic E ionization is another matter and that remains to
be examined. But the satellite observations would seem to close out one of
the remaining options in trying to explain the observations of anomalous
echoes on 1.8 MHz.
73,
Bob, NM7M
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