Solar grand minimum

Source: http://iopscience.iop.org/article/10.3847/2041-8213/aaa124/meta

We have identified a sample of 33 Sun-like stars observed by the International Ultraviolet Explorer (IUE) with the short-wavelength spectrographs that have ground-based detections of chromospheric Ca ii H+K activity. Our objective is to determine if these observations can provide an estimate of the decrease in ultraviolet (UV) surface flux associated with a transition from a normal stellar cycle to a grand-minimum state. The activity detections, corrected to solar metallicity, span the range , and eight stars have log . The IUE-observed flux spectra are integrated over the wavelength range 1250–1910 Å, transformed to surface fluxes, and then normalized to solar B − V. These normalized surface fluxes show a strong linear relationship with activity (R 2 = 0.857 after three outliers are omitted). From this linear regression we estimate a range in UV flux of 9.3% over solar cycle 22 and a reduction of 6.9% below solar cycle minimum under a grand minimum. The 95% confidence interval in this grand-minimum estimate is 5.5%–8.4%. An alternative estimate is provided by the IUEobservations of τ Cet (HD 10700), a star having strong evidence of being in a grand-minimum state, and this star's normalized surface flux is 23.0 ± 5.7% lower than solar cycle minimum.​

An interesting methodology, I think we are going to see 2050 - 2018 = 32 years or roughly 3, 11 year Sun cycles. It will be interesting if past spectral observations of solar output across the spectrum is consistent with their astronomical observations.

Bob Wilson

 

The Russian/Ukrainians did several years ago based on a statistical analysis and proposed solar mechanics model. I remain in a wait-and-see attitude. What this paper brings is astronomy observations.

I haven’t gotten the paper, yet. But earth has an atmosphere and the proposed UV irradiance has me wondering.

Bob Wilson