why there is no evidence for a new maunder minimum
TRANSCRIPT
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Why there is no evidence for a new Maunder Minimum
Doug Biesecker
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Appearance of Jet Streamsaka Torsional Oscillations
Solar Min
Start of Poleward Branch
Solar Min
Weak and patchy
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Comments on ‘jet stream’• Press release says expected to form by 2008. – Formation of pole-ward jet last cycle started ~8 months
after solar minimum.– Poleward jet was weak and patchy at start of last cycle for
anywhere from 18-30 months– The recent solar minimum wasn’t until December, 2008,
so assuming the same delay as last cycle, we wouldn’t expect it before mid-2009.• Don’t I see a hint of something at almost the exact same delay?• This cycle is weaker than the last, so why not expect a weaker
signal than last time?• We only have a 1-cycle history. What makes us think that one
cycle is normal? There is no way of knowing what the natural variability is.
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The slowing ‘rush to the poles’Cycle 21(10.3 yrs)
Cycle 22(10.0 yrs)
Cycle 23(12.2 yrs)
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Comments on ‘rush to the poles’
• Press release says Cycle 24 started out late and has a slow rush to the poles– Yes, cycle 24 started ‘late.’ Cycle 23 was 12 years
long, 2 years longer than the previous two cycles. However, I see the iron emission appearing right as expected, 12 years after the last one
– Why is the cycle 24 rush to the poles drawn to include a segment of the equatorward branch. • There is no physical reason to connect both• This results in a misleading slope
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Weakening Magnetic Fields in Sunspots
What was in the press releaseThe raw data presented at Space Weather Workshop 2010
Solar Max Solar Min
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Comments on weakening magnetic field in sunspots
• Press release says that >13 years of data show 50 Gauss per year drop in magnetic field– The figure used in the press release, available at
http://www.boulder.swri.edu/~deforest/SPD-sunspot-release/ is somewhat misleading (I know, it does have error bars), but the reality is the data before and at solar max is incredibly sparse.
– There is no obvious reason that a straight line is the appropriate fit to these data. A curve that follows the solar cycle may in fact provide a better reduced chi square.• That is, an increase in the magnetic field strength before solar
maximum and also an increase after solar minimum looks completely consistent with the data