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Explanation of the Moon Phases |
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The phases of
the moon are caused by the relative positions
of the earth, sun, and moon. The moon goes around
the earth, on average, in 27 days 7 hours 43 minutes.
The sun always
illuminates the half of the moon facing the sun
(except during lunar eclipses, when the moon passes
thru the earth's shadow). When the sun and moon
are on opposite sides of the earth, the moon appears
"full" to us, a bright, round disk.
When the moon is between the earth and the sun,
it appears dark, a "new" moon. In between,
the moon's illuminated surface appears to grow
(wax) to full, then decreases (wanes) to the next
new moon.
The
edge of the shadow (the terminator) is always
curved, being an oblique view of a circle, giving
the moon its familiar crescent shape. Because
the "horns" of the moon at the ends
of the crescent are always facing away from the
setting or rising sun, they always point upward
in the sky. It is fun to watch for paintings and
pictures which show an "impossible moon"
with the horns pointed downwards. |
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Geomagnetic
Field |
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| Solar
X-rays: |
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| Geomagnetic |
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The X-ray Solar status monitor
downloads data periodically from the NOAA Space
Environment Center FTP server. The previous 24
hours of 5 minute Long-wavelength X-ray data from
each satellite (GOES 8 and GOES 10) is analyzed,
and an appropriate level of activity for the past
24 hours is assigned as follows:
Normal: Solar X-ray flux is quiet (< 1.00e-6
W/m^2)
Active: Solar X-ray flux is active (>= 1.00e-6
W/m^2)
M Class Flare: An M Class flare has occurred (X-ray
flux >= 1.00e-5 W/m^2)
X Class Flare: An X Class flare has occurred (X-ray
flux >= 1.00e-4 W/m^2)
Mega Flare: An unprecedented X-ray event has occurred
(X-ray flux >= 1.00e-3 W/m^2)
The designation "Mega Flare" was chosen
by Kevin Loch when the status monitor was created
on March 4, 1999.
There is no "official" designation for
flares in this range. |
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