New cycle of solar-terrestrial activity

The onset was expected by 2009, but the Sun remained surprisingly quiet.

Washington: Scientists from Boston University`s Center for Space Physics (CSP) believe that there’s new evidence to suggest the onset of a new cycle of solar-terrestrial activity.

The team observed recent aurora displays at high latitudes (ones visible to the naked eye), accompanied by far less luminous glows in the atmosphere at lower latitudes.

Typically, the Sun has an activity cycle of about 11 years, during which it ejects electrically charged particles that cause changes in the Earth`s magnetic field.

These changes produce luminous emissions in the atmosphere, which are subdued during so-called solar minimum years (e.g., in 1996-1997) and very prominent in solar maximum years (e.g., 2001-2002).

The onset was expected by 2009, but the Sun remained surprisingly quiet. Now, in 2010 there are finally signs of the cycle re-appearing.

"The emissions we study come from regions ranging from 200-400 km (125-250 miles) above the surface. These gases are caused to glow by energy input from above, energy that flows downward along the Earth`s magnetic field lines," said Dr. Steve Smith, Senior Research Scientist.

"This image of a SAR (Stable Auroral Red) arc from New Zealand is perhaps the first-ever case of imaging an unambiguous SAR arc in the southern hemisphere," said Michael Mendillo, Professor of Astronomy at BU.

"We hope in the years ahead to have many cases of SAR arcs in our data from both hemispheres, and then examine the full global distribution of such effects," he added.


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