[SADXA] Safe to renew your license for a couple more times anyway!

[Larry]

Copied from the ARRL Leter.


Our Sun's 11-Year Magnetic Cycle Destined to Disappear

The Sun's 11-year magnetic cycle appears to be ending, but that won't 
happen anytime soon. In a paper <https://arxiv.org/pdf/1705.09668.pdf> 
submitted on May 26 to the journal /Solar Physics/, two solar scientists 
are reinterpreting earlier evidence to hypothesize that the Sun's 
rotation rate and magnetic field are in a transitional phase that could 
lead to lengthening solar cycles, with the cycle ultimately disappearing 
altogether between 800 million and 2.4 billion years from now. Travis S. 
Metcalfe and Jennifer van Saders propose the scenario in their paper 
"Magnetic Evolution and the Disappearance of Sun-like Activity Cycles."

"After decades of effort, the solar activity cycle is exceptionally well 
characterized, but it remains poorly understood," the authors say in the 
paper's abstract. "Pioneering work at the Mount Wilson Observatory 
demonstrated that other Sun-like stars also show regular activity cycles 
and suggested two possible relationships between the rotation rate and 
the length of the cycle. Neither of these relationships correctly 
describe the properties of the Sun, a peculiarity that demands explanation."

The authors cite stellar evidence for the shutdown of "magnetic braking" 
in stars similar to our Sun. "The new picture of rotational and magnetic 
evolution provides a framework for understanding some observational 
features of stellar activity cycles that have until now been 
mysterious," they said.

*Solar researcher Travis Metcalfe.*

Metcalfe explained their observations through a recent Forbes magazine 
article 
<http://www.forbes.com/sites/brucedorminey/2017/05/27/the-suns-magnetic-dynamo-is-weakening/#3dcdc2df4fee>. 
"Our previous discoveries identified an unexpected transition in the 
rotation and magnetism of middle-aged stars," Metcalfe is quoted in the 
article, "The Sun's Magnetic Dynamo Is Weakening" by Bruce Dorminey. "We 
now have direct evidence that the stellar dynamo -- the mechanism inside 
stars that sustains their magnetic fields -- actually shuts down during 
this transition."

In their paper, the authors said that future observations with the Las 
Cumbres Observatory global telescope network "promise to probe the onset 
and duration of the magnetic transition that drives the evolution and 
eventual disappearance of Sun-like activity cycles."

*Jennifer van Saders at a Carnegie Observatories seminar earlier this year.*

A 2016 paper Travis co-authored -- "Stellar Evidence that the Solar 
Dynamo May Be in Transition," published in /The Astrophysical Journal 
Letters/, concluded, "The Sun still exhibits a dipole component to its 
global field, particularly near magnetic minimum, but the solar analogs 
also suggest a gradual concentration of the field into smaller spatial 
scales, leading to weakened magnetic braking,"

Metcalfe is listed on the paper as being associated with the Space 
Science Institute and the White Dwarf Research Corp, both in Boulder, 
Colorado. Van Saders is listed as being associated with the 
Observatories of the Carnegie Institution for Science in Pasadena, 
California, and the Department of Astrophysical Sciences at Princeton 
University in New Jersey.