Transcript Livingston & Penn Data and Findings so Far (and some random reflections) Leif Svalgaard Stanford, July 2011

Livingston & Penn Data and
Findings so Far
(and some random reflections)
Leif Svalgaard
Stanford, July 2011
1
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.
2
(Simultaneous) Drawings of Sunspot Group at Different Observatories
Livingston
Livingston makes a ‘finding chart’ of the spots
he observes directly from the projected image.
3
Using the
Finding Chart
we can identify
the spots on
HMI (and other)
magnetograms
4
And compare the measured
magnetic fields
Comparison HMI with Livingston
3000
HMI Gauss
Bobs /cos(h)
y = 0.6337x
Jun 2010 - Apr 2011, 196 spots
2
Bobs LOS
2500
R = 0.5106
2000
1500
1000
500
Livingston Gauss
0
1400
1600
1800
2000
2200
2400
2600
2800
3000
3200
3400
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.
5
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.
Intensity
1
cycle 24
0.8
0.6
B
Gauss
cycle 23
0.4
1000
1500
2000
2500
3000
3500
4000
6
The Distribution of Field Strengths
has Shifted with Time
Distribution of Sunspot Magnetic Field Strengths
2005-2008
2009-2011
1000
1250
1500
1750
2001-2004
2000
2250
2500
2750
3000
3250
3500
3750
Gauss
Is this just a sunspot cycle dependence?
7
We can also compare with MDI to
extend the time base
2011-3-31; 2011-4-1
2500
MDI
y = 0.7934x
R2 = 0.7862
2000
1500
1000
B(Liv) = 1.26 B(MDI,LOS)/cos(h)
500
Livingston
0
1500
1700
1900
2100
2300
2500
2700
2900
2000
HMI
y = 0.8313x
R2 = 0.6183
1800
3/31/2011
4/1/2011
1600
1400
MDI = 1.2 HMI
1200
MDI lvl1.8
B(HMI) =1/(1.2*1.26)~ = 0.6614 B(Liv)
1000
1000
1200
1400
1600
1800
2000
2200
2400
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Some people have already done that
(using automatic detection of sunspots)
Umbral Magnetic Field
4000
3500
B
Gauss
3000
2500
2000
1500
1000
2000
2005
2010
F. T. Watson, L. Fletcher, and S. Marshall, A&A 2011
Year
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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?
11
Other indications of fewer spots
Sunspot Number vs. F10.7 Flux Monthly Averages
250
R
y = -1.4940E-11x 6 + 1.6779E-08x 5 - 7.4743E-06x 4 + 1.7030E-03x 3 - 2.1083E-01x 2 + 1.4616E+01x - 4.1029E+02
2
R = 0.9759
200
150
1951-1990
100
1996-2011
50
F10.7 sfu
0
0
50
100
150
200
250
300
Since ~1996 there have been fewer visible sunspots for a given F10.7 flux
12
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?
13
Similar effect seen in SSN
compared to sunspot areas
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Where is the Extended Cycle?
Altrock, 2011
CYCLE 18
CYCLE 19
CYCLE 20
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.
CYCLE 24
TO: Hill, 2011 15
Fold South
unto North
Sunspot, NM
The Extended
Cycle [if any] is
not very clear
Arosa, Switzerland
16
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)
17
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 18
The Polar Fields are as Mysterious
as Ever, perhaps Reversing Early
2011.7163
2011.7423
150
2011.7683
uT
2011.7943
2011.8203
100
2011.8463
2011.8723
50
2011.8983
2011.9243
2011.9503
0
2011.9763
2012.0023
-50
2012.0283
2012.0543
-100
2012.0803
2012.1063
2012.1323
-150
2012.1583
2003.0
2012.1843
2012.2103
WSO Polar Fields
Bad Filter
S
model
N+S
WF
N
N-S
2004.0
2005.0
2006.0
2007.0
2008.0
Year
2009.0
2010.0
2011.0
2012.0
19
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)
21