2289Re: Solar Activity Report for 8/4/04
- Aug 6, 2004--- In email@example.com, "XK SAZ" <swezlex1@y...> wrote:
> How do you tell it is holding together on the back side of the sun??I just look at the SOHO satellite images on SPACEWEATHER.COM! Ohh,
I'll bet you meant how can anybody tell, didn't you? ;-)
The Solar and Heliospheric Observatory (SOHO) spacecraft has an
instrument on board called the Michelson-Doppler Imager (MDI). The
MDI can detect movements in the "surface" of the sun. Now obviously,
the sun doesn't have a solid surface. When I say "surface," I really
mean what we see as the visible surface, or the photosphere. Hold
Did you know the sun makes noise? It does. The sun is a vibrating
ball of sound waves. It isn't sound you could hear, though. The
sound waves that travel though the sun have a period of around 5
minutes. The sound we humans hear have a period much, much shorter
than that. Still, though, it is sound, albeit it as very low
frequency. Enter the field of study known as helioseismology. In
much the same way that terrestrial scientists use the vibrations of
earthquakes to probe the Earth's interior, solar scientists can do the
same thing for the sun.
Now obviously, you can't put any detection equipment on the sun, so
how do they do that? By analyzing the movements in the photospere
that the sound waves cause. Remember the MDI?
Now for the sunspot part. It is known that intense magnetic fields on
the sun, such as those associated with sunspots, cause variations in
the way that sound waves travel through the sun. By analyzing
photosphere movements with SOHO's MDI instrument, scientists can tell
where the intense magnetic fields are on the other side of the sun.
Where you find strong magnetic fields, you'll find sunspots.
The technology isn't perfect, but it does a pretty good job of
detecting large sunspots with strong magnetic fields. See this link
for more info : http://www.spaceweather.com/glossary/farside.html
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