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STEREO Spies First Major Activity of Solar Cycle 24
May 15, 2009


Caption: STEREO (Behind) spacecraft observed a coronal mass ejection (CME) that erupted on the sun on May 5. Shocks accelerated by the CME produced a large Type II radio burst. The source of the CME is an active region (seen as a bright area in the green EUV 195 still) just rotating into view from STEREO Behind, and it is being followed by another.
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NASA′s Solar Terrestrial Relations Observatory (STEREO) spacecraft has spotted the first major activity of the new solar cycle. On May 5 STEREO-B observed a Type II radio burst and a bright, fast coronal mass ejection (CME) emanating from the far side of the sun. The activity originated in a solar active region that rotated into view from Earth on May 8.

A Type II radio burst is a discharge of radio waves that are emitted when shocks are accelerated by a CME—the sudden eruption of energy and solar material.

The active region appears well above the sun′s equator, at about 30 degrees latitude, which indicates it is part of the new solar cycle. Activity from the previous solar cycle would appear nearer to the sun′s equator. These regions also have a distinct magnetic organization characteristic of new cycle regions.

″This is a really exciting opportunity to observe the first major outbreak of solar activity in Solar Cycle 24,″ says Joseph Gurman, the newly named project scientist for STEREO at Goddard Space Flight Center. Gurman officially takes the helm from current project scientist Michael Kaiser on June 1.

[image-69]The last years of Solar Cycle 23 marked the longest and deepest solar minimum in 100 years. Its unusually small number of active regions and sunspots have led some impatient space-weather watchers to wonder if we were entering another ″Maunder minimum.″ That period, in the late 17th and early 18th centuries, saw few, if any, sunspot regions, and coincided with the deepest part of the ″Little Ice Age″ of global cooling.

The twin STEREO spacecraft each carry two instruments and two instrument suites, including the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI). SECCHI consists of an extreme ultraviolet imager (EUVI), two visible-light coronagraphs (COR-1 and COR-2), and a heliospheric imager (HI). The radio bursts were observed by the SWAVES instrument, also included in the STEREO payload. The solar activity on May 5 was detected with the EUVI instrument aboard STEREO-B, the spacecraft that trails behind Earth in its orbit around the sun.

STEREO, the third mission in NASA′s Solar Terrestrial Probes series, launched on October 26, 2006. STEREO′s mission, now in the extended phase, is to provide the first-ever stereoscopic measurements to study the sun.

For more information about NASA’s STEREO mission, visit:

For more information about the solar cycle, visit:

For more SOHO solar images, visit:

Laura Layton
Heliophysics News Team

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Screen capture from video shows CME.
The COR-2 coronagraph video clip captured the CME in frames taken about every 30 minutes over about one day.
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