In Astronomy & Astrophysics this week is an article of interest to some Talkshop readers. The authors are looking at the little understood variation is solar rotation in the context of peculiar change in recent years. Article has been amended with a new figure kindly provided by L. Zhang showing more detail.
Letter to the Editor
Solar surface rotation: N-S asymmetry and recent speed-up
L. Zhang, K. Mursula and I. Usoskin
A&A 575 L2 (2015)
I quote from the abstract
Conclusions. The rotation of both hemispheres has been speeding up at roughly the same rate since the late 1990s, with the southern hemisphere rotating slightly faster than the northern hemisphere. This period coincides with the start of a significant weakening of the solar activity, as observed in sunspots and several other solar, interplanetary, and geomagnetic parameters.
My interest continues in hemispheric variation. As a reminder I unearthed a very strange functional effect from asymmetric treatment the Greenwich/Hathaway sunspot data where the circa 11 year sunspot cycle dropped out leaving circa 45 y and 9 y. Neither is going to be what many call static, curiously though the 45 y shape correlates with some terrestrial data. Whether this means anything is an open question. Done nothing on this recently although Semi did some work with flares, something I’ve never found time to do.
I’m also mindful of reports saying the sun became unipolar during the Maunder minimum.
Both have been mentioned on the Talkshop, not that a quick search finds what I have in mind (I have about 600 articles here). One I had long forgotten did turn up not that it reveal much, from 2010 tallbloke.wordpress.com/2010/08/24/solar-rotation-speed-and-sunspot-asymmetry/
or this one from 2011 tallbloke.wordpress.com/2011/08/02/hemispheric-sunspot-leadlag-zolotova-et-al/
The monopole but not the paper I had in mind
I expect there is more.
Why this is taking place, ah well.
1. difference of hemispheric sine() sunspot area
Original head image. L. Zhang provided an enhanced image via email: Tim
Post by Tim