Re: flare droughts

Bjoern Gimle (bjorn@tt-tech.se)
Fri, 20 Feb 1998 15:58:59 +0100

These were my comments to Don Baker.
The test with a "full" 66-constellation was done later :

Yesterday, a typing error made me start a 1700 day (4.5 year) long
IridFlar prediction. When I returned to the computer a few minutes
later and terminated, I had almost complete predictions for Ir8+7.
I decided to keep them for statistical analysis. By another typing
error, they were for latitude 57.22, not my own 59.22.

Later, I picked six Iridiums from the five planes now at RAAN 106,
75, 42, 12 and 342 (two from the last, since there seems to be one
plane still missing), and set the latitude to 49 N, and Sun Constraint
to 6 degrees below horizon, and 365 days duration. In both runs I had
the magnitude limit at 3.0, and Flare Angle at 6.0 degrees.

I may write a program to tabulate and/or graph the distribution of
flare counts over the months, the three MMAs, max.predicted magnitude,
the orbit planes etc.

Since the planes precess by 1.5 deg/day relative to the Sun, the five
planes over a year, and the single one over 4.5 years, should cancel out,
but the others, and the difference over latitudes could be interesting.

I realize that you probably can't add any numbers to your article,
but the totals might be interesting to know. 
Normalizing to one year*66 satellites, I get :

At 49 deg.N latitude 1276 flares at night.
At 57 deg.N latitude 1867 flares at night, 435 in twilight, 1500 daytime.

In http://www2.plasma.mpe-garching.mpg.de/sat/seesat/Oct-1997/0357.html
I wrote some comments on the frequency over latitudes.
Using only the 1/cos(Lat) factor, 1276 would extrapolate to 1546 for 57 deg.,
837 at the equator. But my second factor, caused by the orbit turning to W-E
closer to the apex at 86N, and the larger effect of twilight visibility
over the entire night for most of the Summer season at my latitudes,
add considerably to the flare count. I would expect maxima somewhere
between 60 and 80 degrees, N and S.

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