But there was a bigger one

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Nugget
Number: 139
1st Author: Hugh Hudson
2nd Author: Lindsey Glesener
Published: 8 November 2010
Next Nugget: Black Light Flare - Not
Previous Nugget: SDO EVE Flare Observations
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Contents

Introduction

The Nuggets have been watching the current solar cycle as it begins (see Nuggets [A], [B], [C], [D], [E]); the amazing thing about these Nuggets is that they began in December 2008, when we already were baffled by the lengthy [sunspot] minimum period. It has taken almost two years now for us to reach a level of activity where we might have a major flare, as described below, but not yet.

It has been amazingly slow to set in, but we are beginning to get scientific results on flares from the new cycle. We discuss one of them in this Nugget, and another in the next Nugget.

The Spots Return!

Solar physicists interested in flares are eagerly awaiting the powerful ones of this cycle, since there is amazingly good new observational capability such as the powerful SDO satellite. Success here is measured in flares of [GOES X] category, none of which have yet occurred. We have had eight M-class flares (a factor of ten weaker) since SDO "first light", and we will discuss one of the more interesting ones in the next section. Meanwhile, Figure 1 shows that indeed the areas of [sunspots] are steadily increasing, as expected even if a couple of years late.

Spot areas since [HMI] "first light".

This spate of solar activity inspired the Max Millennium Chief Observer to declare a Major Flare Watch condition on November 5. Sure enough, the Sun cooperated and produced forthwith the most powerful flare yet this cycle, an M5.4 event, the very next day, November 6. In keeping with the smooth operation of this alert system, the Chief Observer ended the flare watch on November 7 and no important flares have happened since then.

But this Nugget announces to the world that the barn door in fact was closed too late. A more powerful flare probably occurred way back on November 3; it was listed as merely a C4.9 class, but at that time the active region (which later produced the Number 6 event, and several others) was well behind the west limb of the Sun. This means that its importance could not be easily recognized from front-side observations. We have STEREO, to be sure, but its instrumentation is not complete enough to characterize the magnitude of a flare.

A Powerful Occulted Flare

Conclusions

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