SOHO: the new solar cycle starts with a bang

The appearance of a very special solar spot on the sun surface a few days ago, signalled to scientists around the world that a new solar cycle had begun. This solar spot also produced two solar blasts.

Each solar cycle lasts an average of 11.1 years. The new solar cycle, called 'Cycle 24,' started on 4 January this year, when SOHO observed an event scientists have been anticipating for about a year.

A fairly small and, at first sight, inconspicuous sunspot on the Sun's northern hemisphere showed a reversed magnetic polarity compared to sunspots of previous years. A sunspot is an area of highly organised magnetic activity on the surface of the Sun. This sunspot convinced scientists that a new solar cycle had begun. Later that day, this finding was made official when the sunspot was catalogued by the US National Oceanic and Atmospheric Administration (NOAA).

SOHO was not only first in spotting this harbinger of the new solar cycle, it also observed two associated 'EIT waves,' blast waves that spread out from active regions on the Sun like ripples from a pebble dropped into water. The new cycle started with a 'bang'!

This is just the beginning, and scientists are now eagerly awaiting the activity to follow. Solar Cycle 24 is expected to build gradually, with the number of sunspots and solar storms reaching a maximum by 2011 or 2012, although intense solar activity can occur at any time.

The Solar and Heliospheric Observatory (SOHO) celebrated the twelfth anniversary of its launch on 2 December 2007. The satellite has witnessed the Sun change through almost a complete solar cycle, from quiet to stormy, and back.

SOHO is a project of international collaboration between ESA and NASA.