Solar grand minimum

Discussion in 'Environmental Discussion' started by bwilson4web, Feb 8, 2018.

  1. bwilson4web

    bwilson4web i3 and Prime

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    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 [​IMG], and eight stars have log [​IMG]. 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 [​IMG] (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
     
  2. tochatihu

    tochatihu Senior Member

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    I've not read it and you have. Do authors predict sunspot numbers over next 3 cycles?
     
  3. bwilson4web

    bwilson4web i3 and Prime

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    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
     
  4. tochatihu

    tochatihu Senior Member

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    About 3 groups have predicted about 3 low solar cycles going forward. A larger number of researchers are not predicting one way or the other.

    Solar UV varies much more than visible light over a cycle. This is old news but these authors may have put tighter limits on that.
     
  5. tochatihu

    tochatihu Senior Member

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  6. tochatihu

    tochatihu Senior Member

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    Newsweek may not be a leading source for science in media but they mention:

    Sun's Solar Cycle Is Governed by the Alignment of the Planets, Scientists Discover

    This is related to a topic we discussed here earlier. That other planets by way of gravitational interactions have cyclic effects on earth's climate. Publications by Nicola Scafetta. This one is different in only addressing solar (magnetic) cycle.

    It does, apparently, support most recent NASA @5. That upcoming solar cycle will be similar to current one, and after that, ???
     
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