Sunday, March 13, 2011

What is Up With The Sun?

Have you noticed the Sun has been in the news a lot lately? The reason is the current cycle is finally starting to wake up and send out more flares and solar storms. I am happy about it and my solar filter is happy as well.  It finally gets to come out of the box and play! Its recent turmoil is particularly newsworthy because the Sun was very quiet for a super long time. Astronomers had a tough time explaining the extended solar minimum. New computer simulations imply that the Sun's long quiet spell resulted from changing flows of hot plasma within it.

The Sun is made of  plasma,  not liquid solid or gas. Plasma contains negative electrons and positive ions which flow freely. Flowing plasma creates magnetic fields, which lie at the core of solar activity like flares, eruptions, and sunspots. The Sun contains huge streams of plasma kind of like our Earth's ocean currents. Those plasma currents affect solar activity. 

The Sun also operates in cycles... many cycles. In one of the cycles the Sun's activity rises and falls on 11 year increments. At its most active, called solar maximum, dark sunspots are scattered on the Sun's surface and frequent eruptions, explosions you name it send billions of tons of hot plasma into space. If the plasma collides with Earth, it can disrupt communications and electrical grids and short out satellites.

During solar minimum, the Sun calms down and both sunspots and eruptions are rare. The effects on Earth, while less dramatic, are still significant.  the solar wind that blows through the solar system  weakens,  and add to that the Sun's magnetic field weakening and more cosmic rays reach us from interstellar space. This is not a good thing.
The most recent solar minimum had an unusually long number of quiet and spotless days: 780 days during 2008-2010. Can you say wow? In a typical solar minimum, the Sun goes spot-free for about 300 days, making the last minimum the longest since 1913.
The last solar minimum had two major characteristics, one being no sunspots and  the other a weak polar magnetic field.
The team studying this phenomena used computer simulations to model the Sun's behavior over 210 activity cycles spanning some 2,000 years. He specifically looked at the role of the plasma rivers that circulate from the Sun's equator to higher latitudes. These currents flow much like Earth's ocean currents: rising at the equator, streaming toward the poles, then sinking and flowing back to the equator. At a typical speed of 40 miles per hour, it takes about 11 years to make one loop.
A team of scientists discovered that the Sun's plasma rivers speed up and slow down like a malfunctioning conveyor belt. They find that a faster flow during the first half of the solar cycle, followed by a slower flow in the second half of the cycle, can lead to an extended solar minimum. The cause of the speed-up and slowdown likely involves a complicated feedback between the plasma flow and solar magnetic fields. 
  
This study  is trying to make sense of this wandering current of plasma flow."It's like a production line - a slowdown puts 'distance' between the end of the last solar cycle and the start of the new one," says Team member Munoz-Jaramillo.

The ultimate goal of studies like this is to predict upcoming solar maxima and minima - both their strength and timing. At the moment predicting minimums is still not a reality. The sun has an endless multiple feed back system,  so making predictions will take some time get right. Watching these plasma flows and measuring  strength of poles etc will allow science to get a better picture of when these cycles might begin and end. Until then, we are using the 11 year plan give or take a couple of years!
Until next time,

Keep looking up!

Steve T

3 comments:

  1. Hello and thanks for blogging.
    I have been monitoring reports from
    http://www.youtube.com/user/SolarWatcher#g/u
    and am curious to see if your studies match his.

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  2. Hi, can you please tell me if the sun is wet in any way please? thanks

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  3. Torbjörn Larsson, OMMarch 21, 2011 at 10:11 AM

    Wet?

    There is surely water molecules in parts of the stellar atmosphere, since you have hydrogen and oxygen in our star. Probably ionized, but still molecules FWIW.

    But at a surface temp of ~ 10^4 K, and a core temperature of ~ 10*10^8 K (IIRC), the liquid water region at ~ 10^2 K (depending on pressure) ain't exactly "a stellar opportunity". :-D

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