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Tuesday, November 25, 2014         

FACTS OF THE MATTER


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Complexities of the sun yield clues for forecasts

By Richard Brill

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The sun is the source of all life and almost all energy on Earth, and we live within its extended atmosphere, protected only somewhat against its variable and harmful output of streams of high-energy particles and radiation by a weak magnetic field and our own thin atmosphere.

The sun is the subject of much current research using geophysical methods similar to those that reveal secrets about our planet's interior to examine features within the fluid body of the sun. Some of these appear to be related to sunspot activity.

The sun is a sphere of fluidlike plasma of hydrogen and helium ions with currents that are driven by thermonuclear temperatures of millions of degrees at its center. Plasma is the fourth, high-temperature state of matter in which the internal energy is so high that electrical forces cannot hold electrons and atomic nuclei together as atoms. At the atomic scale it would resemble a soup of electrons with chunky hydrogen and helium ions drifting in it like peas in a thick broth.

Motion of the electrically charged plasma in intense convection currents creates magnetic effects that interact with the sun's magnetic field. The rapid rotation of the sun on its axis twists the viscous plasma like taffy, causing magnetic fields that emerge from the surface to coil like springs. Every 11 years or so after becoming increasingly chaotic with sunspot activity, the magnetic fields realign and the activity gradually decreases until reaching solar minimum, followed soon by another cycle.

The solar minimum of 2008 is the lowest activity on record. Heliophysicists would like to know why this cycle was both low and prolonged. Each bit of data adds to the understanding of the sun's climate, which heliophysicists hope will lead to better forecasts of solar weather events.

These events, which increase in frequency and intensify during solar maxima, can interfere with electronic circuits in Earth satellites and on the surface, causing disruptions, power outages and billions of dollars of damage.

Although we cannot prevent solar weather events, as with Earth weather the longer the forecast time the greater the opportunity to prepare.

New technology and techniques reveal plasma circulation patterns at and near the sun's surface on a global scale that show some connection with the solar cycle. One is a meridional flow that changes speed as it travels across the surface from equator to poles but which moved anomalously slow during the 2008 minimum.

Heliophysicists have followed the development of a solar jet stream from thousands of miles below the surface that seems to correspond in periodicity with the solar cycle. Others have detected acoustic oscillations that change with the solar cycle.

All of these are only preliminary findings and caution is due against drawing any sweeping conclusions or harboring false expectations of accurate solar weather forecasts in the near future. Every step in understanding space climate is one step in averting a major disaster given the inevitable 200-year solar storm.

Richard Brill is a professor of science at Honolulu Community College. E-mail questions and comments to rickb@hcc.hawaii.edu.

 






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