Friday, June 22, 2012

Day 1: I Cheat, Still Lose

.....For the first object on my Big Year (at least pass one of it), I decided to pick the Sun, which is fair - it's in the sky!  I won't spend much time talking about how to find this particular object, as it is usually pretty easy to find.  In any observation of the Sun, as I did with my post on the Transit of Venus, it is pretty much required to say *DO NOT OBSERVE OBSERVE THE SUN WITH MATERIAL THAT IS SPECIFICALLY BUILT FOR LOOKING AT THE SUN!*  It is not possible to stress that enough!
.....So I used a filter that blocks out the vast majority of the light, and all of the UV light.  As before, I found the Sun by minimizing the shadow of the telescope, and then moving back and forth until the disk comes into sight, only to see ...
 .....Boring!  The sunspots that were visible in the images I took of the Transit of Venus have rotated out of our view, and they have not been replaced by new ones.  (The blurs that look like clouds moving across the Sun are on Earth, and perhaps just on the interface between the camera and the telescope.)

 .....See?  Sunspots then, but not now.  Even the image taken from NASA's Solar Dynamics Observatory show very little, just one of the last sunspots slipping off of the edge.
Source
.....Sunspots are caused because the Sun has a powerful magnetic field, and that the Sun is not solid.  Let us start by assuming that at some instant, the Sun has a magnetic field similar to the Earth.  There is a north magnetic pole, and a south magnetic field, and there are field lines that connect one to the other.  Magnetic fields are generated by moving charge, and the orbit of each electron around each hydrogen atom (hydrogen makes up the overwhelming majority of the Sun and other stars) is itself a moving charge, and so each atom has a magnetic field, and these tiny, tiny magnetic fields are forced to line up by the Sun's overarching magnetic field.  

.....The Sun rotates a little faster at the equator than it does at the poles, unlike the Earth (although it would be nice to have a little more variety to the south of Minnesota than just Iowa), and as the gas at the equator is moved forward, it actually carries that magnetic field forward, distorting the field lines.  The Sun keeps rotating, and the field lines start getting twisted more and more until the magnetic field lines are actually forced to branch off of the Sun's surface.  When the Sun's magnetic field gets too wrapped up in itself, it does clear itself out, and start over (with the poles reversed).
This NASA site also has an animation.

.....When this happens, the gas at the kinks, where the magnetic field leaves and rejoins the Sun's surface, gets locked in place.  This gas cannot be replaced by the hot gas below it, as is usual in stars, and that gas cools off to a paltry 7100 Fahrenheit, as opposed to the 10,000 Fahrenheit of the rest of the surface.

.....This does have an effect on the Earth.  When those loops leave the Sun's surface, some material does travel along that path, and when the loop breaks down, that material is ejected into space.  Since a moving charge creates a magnetic field, this mass of moving charged particles carries a magnetic field with it.  If this eruption hits the Earth, then it could give rise to spectacular displays of Northern/Southern Lights (the aurora), but it could also damage satellites or more.  In 1989, an ejection of this charged mass hit the Earth, and from space the Earth's power grid looks like one big ol' antenna.  This "antenna" caught the charge, and the overload knocked out power to the northeast US and southeast Canada.

.....There is also an effect of the Sun's sunspots on the Earth's climate, although this is imprecisely understood.  Times of low sunspot activity have corresponded to periods of lesser temperatures on Earth, with a multi-year lack of any sunspots at all corresponding to the "Little Ice Age".
Source, and more detail on its impact on climate.

.....Closer to the present, after 1998 (for several years, the hottest year on record), there was a period of several years with few to no sunspots; this would be expected to have a cooling effect on the Earth.  Indeed, for a few years after this (also impacted by the behavior of El Nino / La Nina systems), the temperature did decrease slightly, but solar activity picked back up, and we are back to setting records for "hottest year ever".  (So far, this spring was the hottest ever recorded in the US.)  There have been arguments that solar effects are what drives climate change, but close examination shows that solar variation correlates well to Earth's average temperature variation ... until about 1950.  Then something else (interpreted by pretty much everybody outside the fossil fuel industry as "human effects") dominates.

   

NASA
 


No comments:

Post a Comment