Wednesday, February 18, 2015

Get A Look At Our Sun In A Time-Lapse Movie: Celebrating the Solar Dynamics Observatory

It's past time to celebrate the Solar Dynamics Observatory which saw it's five year anniversary on Feb. 11th. Over 200 million images have been taken (at the rate of just over 1 per second) and actually compiled into a compressed time lapse movie which you can view here:

Pay attention especially to the magnificent loops of plasma: the coronal loops which are structured such as shown in the detailed diagram below, and occur in solar active regions,

And also the bursting loops associated with solar prominences, which are some of the most energetic and stupendous sights visible on the Sun.

One such giant prominence which exploded some years ago is shown in the image below:

The physical basis for these prominences has been known for some time and can best be explained by reference to the diagram shown below:

This shows the motion - tied to the plasma flow - relative to the local magnetic or B-field.  The key point to note is that the flow's cutting action on the field line triggers a change in the magnetic flux and an induced current.  The only way for the plasma to avoid the unrealistic situation we call "infinite conductivity" is for it to be constrained to follow the B-field lines rather than to cross them. This is what is meant by "field freezing" and if you look carefully at the SDO movie you will spot a number of instances where this occurs!

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