Mon, Mar 07, 2011
Solar Minimum Can Effect Earth's Atmosphere, Space Debris
NASA-sponsored research has resulted in the first computer
model that could explain the recent period of decreased solar
activity during the sun's 11-year cycle.
This recent solar minimum, a period characterized by a lower
frequency of sunspots and solar storms, was the deepest observed in
almost 100 years. The solar minimum has repercussions on the safety
of space travel and the amount of orbital debris our planet
accumulates. Solar scientists around the world were puzzled by the
extended disappearance of sunspots in 2008-2009. Results published
in Thursday's edition of Nature indicate the mystery may be
solved.
"Plasma currents deep inside the sun interfered with the
formation of sunspots and prolonged the solar minimum," says lead
author Dibyendu Nandi of the Indian Institute of Science Education
and Research in Kolkata.
During this deep solar minimum, the sun's magnetic field
weakened, allowing cosmic rays to penetrate the solar system in
record numbers making space a more dangerous place to travel. At
the same time, the decrease in ultraviolet radiation caused Earth's
upper atmosphere to cool and collapse. As a consequence space
debris stopped decaying and started accumulating in Earth orbit due
to increased atmospheric drag. These effects demonstrate the
importance of understanding the entire solar cycle, during both
minimum and maximum.
Observations from NASA's Solar Dynamics Observatory (SDO) will
eventually provide measurements that could validate the current
model and provide the basis for future solar cycle prediction.
"This research demonstrates how observations from Heliophysics
System Observatory missions stimulate new theories and advance
modeling techniques," says Richard Fisher, director of the
Heliophysics Division in NASA's Science Mission Directorate at the
agency's headquarters in Washington.
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