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Livingston & Penn Data and Findings so Far

(and some random reflections)

Leif Svalgaard

Stanford, July 2011

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What is Livingston Measuring?

From 2001 to 2011 Livingston and Penn have measured field strength and brightness at the darkest position in umbrae of 1843 spots using the Zeeman splitting of the Fe 1564.8 nm line. Most observations are made in the morning [7h MST] when seeing is best. Livingston measures the absolute [true?] field strength averaged over his [small: 2.5″x2.5″] spectrograph aperture, and not the Line-of-Sight [LOS] field.

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(Simultaneous) Drawings of Sunspot Group at Different Observatories

LivingstonLivingston makes a ‘finding chart’ of the spots he observes directly from the projected image.

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Using the Finding Chart

we can identify the spots on

HMI (and other) magnetograms

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And compare the measured magnetic fields

y = 0.6337x

R2 = 0.5106

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HMI Gauss

Livingston Gauss

Bobs LOS

Bobs/cos(h)

Comparison HMI with Livingston

Jun 2010 - Apr 2011, 196 spots

HMI LOS fields [corrected for simple projection] is only 63% of Bill Livingston’s. This is our problem, not his. SOLIS and HINODE (and our Vector fields) agree with Bill.

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In spite of large scatter the magnetic field has decreased 500 G since 2001

Livingston also measures the intensity of the umbra compared to the continuum and finds that [in the infrared] that for all spots he can see [i.e. intensity < 1] the field is greater than ~1450 G. Another 500 G to go...

Hence his statement that if [when?] the decline of the field continues, spots will effectively ‘disappear’ or at least be much less visible.

0.4

0.6

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Intensity

B Gauss

cycle 24

cycle 23

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The Distribution of Field Strengths has Shifted with Time

Is this just a sunspot cycle dependence?

1000 1250 1500 1750 2000 2250 2500 2750 3000 3250 3500 3750

2009-2011

2005-2008

2001-2004

Gauss

Distribution of Sunspot Magnetic Field Strengths

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We can also compare with MDI to extend the time base

y = 0.7934x

R2 = 0.7862

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Livingston

MDI

2011-3-31; 2011-4-1

y = 0.8313x

R2 = 0.6183

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3/31/2011

4/1/2011

HMI

MDI lvl1.8

MDI = 1.2 HMI

B(Liv) = 1.26 B(MDI,LOS)/cos(h)

B(HMI) =1/(1.2*1.26)~ = 0.6614 B(Liv)

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Some people have already done that (using automatic detection of sunspots)

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B Gauss

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Umbral Magnetic Field

F. T. Watson, L. Fletcher, and S. Marshall, A&A 2011

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It is not clear what they plot [LOS or corrected for projection, how?]

Their STARA algorithm does not seem to perform very well for small spots so the data in 1996-1997 and 2008-2010 is suspect

So, unfortunately, it is hard to draw any firm conclusion one way or the other. The next year or two will be crucial.

Livingston has some scattered measurements back to 1998, so one could look at those and compare

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Livingston, Penn, and Svalgaard:

Extrapolating the behavior from the past 13 years into the next 13 years suggests the Sun may enter a new Grand Minimum.

If true, we shall learn a lot about ‘The Forgotten Sun’ that nobody alive today has ever seen, with obvious implications for the climate debate and environmental issues generally.

Are there other indications that this might happen?

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Other indications of fewer spots

y = -1.4940E-11x6 + 1.6779E-08x5 - 7.4743E-06x4 + 1.7030E-03x3 - 2.1083E-01x2 + 1.4616E+01x - 4.1029E+02

R2 = 0.9759

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F10.7 sfu

R

Sunspot Number vs. F10.7 Flux Monthly Averages

1951-1990

1996-2011

Since ~1996 there have been fewer visible sunspots for a given F10.7 flux

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The Observed Sunspot Number vs. that Calculated from the ‘old’ Relationship is too low Recently

Since the Sunspot Number is dominated by the number of small spots, the loss of visibility of small spots might be a natural explanation.

Was the Maunder Minimum just an example of an extreme L&P effect?

Is this happening again?

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Similar effect seen in SSN compared to sunspot areas

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Where is the Extended Cycle?

Measurements of the location of ‘peaks’ of Fe XIV coronal emission at 503 nm (the ‘Green Line Corona’) over 7 solar cycles. The plots show the probability of observing a ‘peak’ at a given latitude as a function of time.

Altrock, 2011

TO: Hill, 2011

CYCLE 20

CYCLE 18

CYCLE 19

CYCLE 24

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Fold South unto North

Sunspot, NM

Arosa, Switzerland

The Extended Cycle [if any] is not very clear

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Our ‘Understanding’ of the Extended Cycle

Robbrecht et al. ApJ, 2010: “We conclude that the so-called extended cycle in coronal emission is a manifestation not of early new-cycle activity, but of poleward concentration of old-cycle trailing-polarity flux by meridional flow”

The red contours computed from PFSS coronal field (MWO)

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Waldmeier also Interpreted The Green Line Emission as Marking the Boundary of the Polar Cap, ‘Rushing to the Pole’ when the

New Cycle Started

Solving the Enigma of the ‘Extended Cycle’ is a worthy Goal of SC24 Research

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The Polar Fields are as Mysterious as Ever, perhaps Reversing Early

2011.71632011.74232011.76832011.79432011.82032011.84632011.87232011.89832011.92432011.95032011.97632012.00232012.02832012.05432012.08032012.10632012.13232012.15832012.18432012.2103

-150

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2003.0 2004.0 2005.0 2006.0 2007.0 2008.0 2009.0 2010.0 2011.0 2012.0

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N

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WSO Polar Fields

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uT

N-S

model

WF

Bad Filter

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The HSC is Approaching Typical Solar ‘Maximum’ Inclinations

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And We Have to Leave it at That, because there are More Questions than Answers (what

a Wonderful Time)