SUN'S SHIFTING GEARS : SCIENCE

SUN shifts gears, but it's unlikely to let loose. But as a solar cycle begins, scientists aren't expecting any disruptive explosions.

The sun is beginning to perk up again. An international panel of scientists announced this month that the sun had emerged from the quietest part of of its 11year sunspot cycle and had entered the 25th numbered cycle. [The numbering of sunspot cycles goes back to 1755]

The researchers predicted that the forthcoming cycle would be a pretty quiet one.

Solar scientists track the cycle through the ebb and flow in the number of sunspots, which reflects the level of ferocity in the sun's magnetic fields.

Sunspots can shoot out bursts of radiation called solar flares , as well as giant eruptions of particles known as  coronal mass ejections. If a giant coronal mass ejection hit Earth, it could upend modern civilization, knocking out satellites and inflicting continent wide blackouts.

Such a solar explosion in 1850, known as the Carrington event, disrupted telegraph systems. Today, the world is more electrically interconnected, and giant transformers that are part of power power grids are thought to be particularly vulnerable.

Just as economists wait months to declare the start or end of a recession, scientists delay such pronouncements for solar cycles, because they average the sunspot numbers over 13 months to avoid being fooled by short-term fluctuations in the sun's activity.

Nine months ago, in December, the sunspot cycle reached its calmest state. ''Since then it's been slowly but steadily increasing,'' said Lisa Upton, a solar scientist at the Space Systems Research Corporation and one of the leaders of Solar Cycle 25 Prediction Panel, which is sponsored by NASA and the National Oceanic and Atmospheric Administration.

Over the past half century, the solar cycles have become progressively weaker, leading some scientists to to speculate that the sun might be on the cusp of an extended quiet period.

The last solar maximum, with an average sunspot number of 114, was the weakest since 1928 and the fourth weakest over all.

The prediction panel expects that activity during this solar cycle will be well below average, with a peak of 115 in the suspect number, give or take 10. That would be about the same as the last cycle.

The maximum is predicted to occur in July 2025.

The World Students Society thanks author Kenneth Chang.