Cycle 24 - time to panic

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Will sunspots and flares ever return?
Will sunspots and flares ever return?
How unusual is this behavior?
How unusual is this behavior?
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In this Nugget we conclude that it is too soon to panic, but that certainly we're seeing an interesting diminished level of activity.
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In this Nugget we conclude that it is too soon to panic, but that certainly we're seeing an interesting diminished level of activity which most of us has not seen before.
== F10.7 and other indices ==
== F10.7 and other indices ==

Revision as of 19:33, 11 April 2009


Nugget
Number: 99
1st Author: Leif Svalgaard
2nd Author: and Hugh Hudson
Published: 13 April 2009
Next Nugget: NUGGET 100
Previous Nugget: Chree Analysis for Flares
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Contents

Introduction

We're in an extended period of minimal solar activity (see Nugget 91 for a previous look at this issue - without flares, RHESSI is missing its most important observational work, and there has not been even a C-class flare yet this year. Will sunspots and flares ever return? How unusual is this behavior? In this Nugget we conclude that it is too soon to panic, but that certainly we're seeing an interesting diminished level of activity which most of us has not seen before.

F10.7 and other indices

The 10-cm radio flux from the Sun, with its daily index F10.7, is one of the basic standard tools for gauging the level of solar activity. This index has been generated in an unbroken string since 1947. It is derived from careful photometric measurements made in Canada and pioneered by A.E. Covington.

'Figure 1: The F10.7 index for the last 24 months (red) and the average variation, month by month since the peak of the corresponding maximum, for the four previous cycles in the record.

The figure on the left might give cause for alarm if one is interested in flare observation. It shows (red line) the variation of F10.7 monthly means for the two years prior to the present time. The black line shows the mean of the four previous cycles, registered by [summed epoch analysis] on simple Gaussian fits to their preceding maxima as references.














Figure 2 below shows three indices with higher resolution (daily, rather than monthly).

'Figure 2: Three key indices of solar activity, showing the current minimum period from 2008 to the time of writing (April 11, 2009).

This plot comes from a Web page that is updated daily.









daily view

Counting the new and old spots

Historical fact

Conclusions

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