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This week we had a double dose of good news. Right at the time of
the Autumnal Equinox, on Tuesday, September 22, sunspot 1026, a new
Cycle 24 sunspot, came into view over the Suns eastern horizon. We
watched this emerge a week ago on the Suns far side via the STEREO
project. STEREO is a fantastic tool, because it gives us all a live
view of nearly the whole Sun, and it displays very recent images.
It turns out that images from each craft, the ahead, leading earth
in its orbit, and the behind, trailing earth in its orbit,
satellite, are updated approximately every 15 minutes. No more
guessing about activity on the other side of the Sun, because we can
see it live in animated form based on real time data. On that
animated Sun display you can see there are longitude lines every 30
degrees. Since there are twelve of them, and a rotation of the Sun
takes approximately 27R5 days, it varies by latitude, then on
average it takes about R0764 days, or 1 hour, 50 minutes, for the
Suns rotation to progress one degree longitude. Therefore, when we
saw the sunspot at minus 120 degrees longitude, we could estimate
that it would take about 2R2917 days, which is 2 days and 7 hours,
for the spot to reach the Suns eastern horizon, at minus 90 degrees,
and first become visible. On Monday the daily sunspot number was
11, then on Tuesday and Wednesday a second Cycle 24 spot, number
1027, emerged in the Suns Northern Hemisphere. Tuesdays daily
sunspot number rose to 26, then on Wednesday it was 31 as the area
of the spots grew. On Thursday the sunspot number was 32. From
Monday to Tuesday the total sunspot area increased by seven times,
then on Wednesday it doubled, then on Thursday rose about twenty
nine percent over Wednesdays area. You can see the sunspot numbers,
solar flux and sunspot area for each day at www.swpc.noaa.gov.
Checking www.swpc.noaa.gov/ftpdir/indices shows us that geomagnetic
indices are extremely quiet and stable, so I suppose there are three
pieces of great propagation news this week. Both sunspots have
moved into their maximum geo effective position, around zero degrees
longitude, in the center of the solar disc as viewed from Earth, led
by sunspot 1027. The current prediction from NOAA/USAF is for
continued quiet conditions today with a planetary A index of 5, then
on Saturday some unsettled conditions and a planetary A index of 12.
It drops to 8 on Sunday, then back to 5 for the foreseeable future.
Solar flux is expected to continue at about the same level through
the first few days of October. Sunspot numbers were 0, 0, 0, 0, 11,
26, and 31 with a mean of 9R7. 10R7 cm flux was 69R1, 69, 70R5,
71R3, 71R9, 74R7, and 76R1 with a mean of 71R8. Estimated planetary
A indices were 8, 3, 2, 4, 7, 4 and 2 with a mean of 4R3. Estimated
mid latitude A indices were 6, 2, 1, 3, 5, 2 and 1 with a mean of
2R9‚
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