Slashdot Mirror
Sun's Activity Levels Reconstructed
neutron_p writes "An international team of scientists has reconstructed the Sun's activity over the last 11 millennia and forecasts decreased activity within a few decades. The activity of the Sun over the last 11,400 years, i.e., back to the end of the last ice age on Earth, has now for the first time been reconstructed quantitatively. The scientists have analyzed the radioactive isotopes in trees that lived thousands of years ago. As scientists report in the current issue of the science journal Nature, one needs to go back over 8,000 years in order to find a time when the Sun was, on average, as active as in the last 60 years."
I'm not sure I trust their error bars (they appear on the second plot). Since they're using 10-year averages, they should be removing the effects of the solar cycle. But their sunspot number curves drop below 0 sunspots in several places. A negative number of sunspots is, obviously, unphysical. Also, their data is pretty wildly varying over short timescales (again, solar cycle should be removed) and doesn't match the actual sunspot records from 1610 on very well, either.
One thing I'm curious about is what effect that the Sun's activity has on climate change. There have been spacecraft studying the sun and more spacecraft studying the magnetosphere and it's interaction with the solar wind. However, it seems that we only have understanding of individual events and the immediate effects of those events. It will be really interesting when some people get a good idea of what long term effects CMEs (coronal mass ejections) and other Sun activity has on our little blue world.
I wonder if instead of just examining the historical record, they also took one additional factor into account.
Physicists modelling the history of the Sun say that its overall brightness (read: activity level) has increased by about 30% since being born. This is related to the buildup of helium "ash" (from fusion of hydrogen) in its core. Furthermore, the trend is expected to continue -- quite slowly, of course. Nevertheless, any forcast that the current activity can be expected to decrease in the next few years -- or even decades -- might be rather "off" if that factor is not taken into account....