Kane, "Prediction of the sunspot maximum
of solar cycle 23 by extrapolation of spectral components," Solar Physics, vol.
Indeed, it was on the basis of the annual number of spotless days (NSD) and number of newly appearing 'clusters of spots' that Samuel Heinrich Schwabe (1844) first showed that the Sun's activity varies from a sunspot minimum (SSN min) to a sunspot maximum
(SSN max) and then to another minimum over a period of about a decade.
The peak of North Dakotan auroral activity appears to take place after sunspot maximum
and when the spots are declining.
Scientists currently predict that Cycle 24 will peak in the summer of 2013, with a smoothed sunspot maximum
of about 60 with fluctuations that may be as high as 90.
As for those fierce solar storms, the next sunspot maximum
will not happen until 2013, and will be on the mild side, astronomers now say.
The last sunspot maximum
(peak of activity) was in 2000, and the next one is expected in 2011.
Likewise, because of the observed two orders of magnitude increase in the X-ray background flux from sunspot minimum to sunspot maximum
, essentially all lesser soft X-ray events near solar maximum go unrecorded, this also contributing to the overall undercount.
The comparatively low level of solar activity this close to the predicted sunspot maximum
next year, seems to confirm that we are indeed experiencing a low activity solar cycle.
In 1991, when the Yohkoh spacecraft took the image of the Sun on page 48 of the January issue, the Sun was just past sunspot maximum
, not at minimum.
With sunspot maximum
coming soon, we tested five leading telescopic solar filters for their sharpness and clarity of view.
During sunspot maximum
, patches of bright calcium emission dapple the surface; at low activity levels this emission is sparse.
At sunspot maximum
the magnetic field is more jumbled, and coronal streamers jut outward in all directions like the spines of a sea urchin, making the corona look round overall.