Solar cycle

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After observing the three stars every six months for more than a decade, astronomers measured the ups and downs in X-ray radiation emanating from them, just like our Sun's 11-year long sunspot cycles. X-ray bombardment is considered a major hazard to the possibility of life, as high doses of intense radiation can strip away planetary atmospheres - a fate thought to have been suffered by Mars - and destroy any life existing there.
(2) I show that this equilibrium is always locally indeterminate and hence permits the existence of sunspot cycles fluctuating around the stationary equilibrium (Result 4).
We researched sunspot cycles, recessions and major financial crises as far back [as possible], and 11 out of 11 happened in a down sunspot cycle.
Monthly number of spotless days (NSD) for elapsed time from months (t) = -36 to t = +24 months relative to the epoch of sunspot minimum (SSN min) (Em) for sunspot cycles SC10-SC24 (Continued).
This is because the identified fluctuations in the intensity of solar irradiance are unusual at present: whereas the so-called sunspot cycles each lasted eleven years in the past, for unknown reasons the last period of weak solar irradiance lasted 13 years.
But I've never considered the effect of sunspot cycles, which can dramatically disturb the earth's geomagnetic field.
If one looks at the sunspot cycles, the conclusion has to be that the world has entered a cooling cycle.
The BAA Aurora Section monitors auroral activity and the records show how it varies with the sunspot cycles.
At issue is whether such changes can be driven by human activity--as opposed to, say, sunspot cycles or other natural factors.
Powerful support for this idea came in 1991 when Eigil Friis-Christensen, director of the Danish National Space Centre, published a study showing a remarkable correlation between global warming and the length of sunspot cycles.
I found, as he suspected, that these cycles were in phase with sunspot cycles. A portion of his cycle is reproduced in Figure 1.