posted on Jul, 7 2009 @ 04:56 PM
There is a lot of interest in the Real-time Magnetosphere Simulator located here
It provides data from the ACE satellite and pretty pictures of a computer simulation which calculates the effects of the data on our magnetosphere.
Unfortunately, it provides very little indication of what any of it means.
It's helpful to look at the actual data used for the simulation. The pressure on the magnetosphere is a function of two things; the speed of the
solar wind and the density of the solar wind. These factors can be seen on the graphs below the pressure representation. Right now the speed of the
wind is quite low (~350kps), indicating low energy levels. The density, the number of particles in the wind, is reasonably high. Notice that the speed
is quite steady but the density fluctuates quite a bit. Those fluctuations are what is causing the simulator to show fluctuations in pressure. Imagine
it like someone gently throwing handfuls of sand at a balloon. A small handful of sand doesn't do much to the balloon but a large handful, thrown at
the same speed will have a larger effect.
In itself, pressure has little to do with geomagnetic activity. The shape of the bow wave and the pressure on it don't tell us much. A geomagnetic
storm is a complicated affair, involving a number of factors one of them being the polarity of the solar wind and its relationship to the polarity of
the Earth's magnetic field. To find out more about this we need to look at more of the raw data. The Magnetic Field Vectors tell us about the
North-South alignment of the solar wind. These are the Bz and By data streams. Under "normal" conditions these vectors are quite stable, gently
fluctuating a bit and occasionally switching polarity. It is when these changes get wild take on a southern orientation and the solar wind increases
in both speed and density that it is likely we will experience a geomagnetic storm.
On June 24 of this year, we experienced a minor geomagnetic storm (didn't hear much about it did you?) Here is an animation from the simulator for
that day. Notice that when the storm hits at about 15:00GMT the speed and density suddenly increase. Notice also that the Bz and By values go wild.
Again, to put things into perspective, this was a minor event. In a major storm all of these data streams are going to be doing a lot more than what
we see here.
Another thing to remember is that this is a real time
simulation. It tells us what is happening now, it is not a forecast. As you can see in
the movie above, the onset of a solar storm is quite sudden. When it happens, it happens. There really aren't any precursors. In a destructive
geomagnetic storm, we'll lose power at the same time the simulator is saying "uh,oh".
[edit on 7/7/2009 by Phage]