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Here Comes The Sun (spots)



It is the approach of summer, and the Sun is emerging from a deep sleep.  Parts of Canterbury may reach maximums of over 30C as early as 19 December.  But something else is also stirring into life - the tide of increased electromagnetic intensity on the Sun.  Black mole-like marks called ‘sunspots’, in reality regions of strong magnetic field, are re-gathering on the Sun's surface after a long absence.


Counting the black dots was once the practice of Chinese and Indian astronomers, using rock-crystal lenses, and by Galileo, who ground his own lenses from glass.  Modern day counting of sunspot regularity began with Solar Cycle 1 which peaked around 1761.  Solar Cycle 23 has recently finished and scientists have been waiting for a while for signs that SC24 is about to get underway.


The spots can be up to 50,000 km in diameter and the activity cycle is 9-13 years.  For convenience we identify 11 and 22 year turnarounds.  2007 is now considered to be the nadir of the last SC; the end of a low point in sunspot mins.  Low sunspot activity brings drought conditions, because less heat causes less evaporation which serves less rain.  High sunspot activity equates to drought conditions too, because despite higher evaporation greater ground heat keeps clouds elevated delaying rain, and although more rain is generated it falls out at sea.  It is in the period between solar mins and max's that we get the greatest chances of La Nina rain conditions.


Let us look back in time.  Other min years have been 1843, 1856, 1867, 1879, 1890, 1901, 1913, 1924, 1933, 1944, 1954, 1964, 1976, 1985, 1996, and 2008.  Because SC23 in size resembles SC19 which peaked in 1957 and was followed by 20 cooler years, even when SC24 revs up it will likewise begin two decades of cooler temperatures.  1972/3 was a big El Nino year, with a severe drought in Canterbury.  It is no surprise that 1972 was a solar max year.  Droughts reoccur in the same place about every 9 years.  From 1972 add 9 and get 1981/82.  1982/3 was the year of the next solar max and also brought drought.  Nine further years to 1991/92 - another solar max and very dry year.  Nine more years to the next solar max in 2001/02, and another drought.  It does not take a genius to work out the pattern. 


In solar max years huge sunspots and intense solar flares become a daily occurrence.  Auroras appear in Florida.  Radiation storms knock out satellites.  Radio blackouts frustrate hams.  The last such episode took place around 2000-2001.  During solar min the opposite occurs.  Solar flares are almost nonexistent while whole weeks go by without a single, tiny sunspot to break the monotony of the blank Sun.  That is what we have been experiencing for the past two years.


The average solar cycle is 131 months with a standard deviation of 14 months.  SC23 (the one we are experiencing now) has lasted 142 months-- not abnormal, so the current minimum has not been unusual.  The longest minimum on record, the Maunder Minimum of 1645-1715, lasted an incredible 70 years.  The solar cycle seemed to break down completely.  During that time came the Little Ice Age, a series of extraordinarily bitter winters in Earth's northern hemisphere.  The sunspot cycle revived itself in the early 18th century.


Now, after two years of eerie calm, sunspots are returning.  Last month there were five sunspot groups; a real increase in solar activity.   Four of the five belonged to the new SC24.  2008 is emerging as a year of overlap with both cycles weakly active at the same time.  From January to September, the Sun produced 22 sunspot groups; 82% of them belonging to spent SC23.  October added five more; but this time 80% belonged to SC24. The tables have turned.


At first glance, old- and new-cycle sunspots look the same, but they are not.  To tell the difference, solar physicists check two things: a spot's latitude on the Sun and its magnetic polarity.  New-cycle sunspots appear at high latitude, while old-cycle spots cluster around the Sun's equator, and the magnetic polarity of new-cycle spots is reversed compared to old-cycle spots.  Four of October's five sunspot groups satisfied these two criteria for membership in SC24.  On Nov. 3rd and 4th, a flurry of solar flares made themselves felt on Earth.  X-rays bathed the dayside of our planet and sent waves of ionization rippling through the atmosphere over Europe.  Hams monitoring VLF radio beacons noticed strange "fades" and "surges" caused by the sudden ionospheric disturbances.


So it's a start.  Stay tuned for solar activity.  SC24 should pick up speed halfway through next year and will determine the temperatures in the next decade.  Parched parts of Australia should receive drought-relieving rain around next June.  Warmer world temperatures should come around 2013, about the time SC24 will be at peak.  This correlates well to the El Nino Southern Oscillation Index which indicates the next drought for NZ and Australia to be between 2011-13.


© Ken Ring 2008

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