Another Maunder Minimum?

Transcription

1 Another Maunder Minimum? Leif Svalgaard Stanford University Nobeyama, 27 November,

2 Indicators of Solar Activity Sunspot Number (and Area, Magnetic Flux) Solar Radiation (TSI, UV,, F10.7) Cosmic Ray Modulation Solar Wind Geomagnetic Variations Aurorae Ionospheric Parameters Climate? More Longest direct observations Rudolf Wolf After Eddy, 1976 Solar Activity is Magnetic Activity 2

3 How Well was the Maunder Minimum Observed? Hoyt &Schatten: 27 It is not credible that for many years there were not a single day without observations Number of days per year with observations 3

4 Unrealistic Coverage during MM: More Realistic Assessment: H&S Even after eliminating the spurious years with no missing data there are enough left to establish that the Maunder Minimum had very few visible sunspots and was not due to general lack of observations 4

5 Unfortunately Two Data Series Ken Schatten Maunder Minimum Hoyt & Schatten, GRL 21,

6 The Ratio Group/Zurich SSN has Two Significant Discontinuities At ~1945 (after Max Waldmeier took over) and at ~1885 6

7 Sergio Cortesi Locarno Locarno is today the reference station of the official SIDC SSN In the 1940s the observers in Zürich [and Locarno] began to Weight spots. The net result is a ~20% inflation of the official Zürich SSN since ~1945 Effect of Weighting of Sunspots Unweighted count red SSN = 10*G+S 26% inflated

8 Compared with Sunspot Area (obs) 1000 Rz SA 0.1 Not linear relation, but a nice power law with slope Use relation for pre-1945 to compute Rz from Area, and note that the observed Rz after 1945 is too high [by 21%] 8

9 What to do about all this? Sunspot, NM, Sept The implications of this re-assessment of the sunspot record are so wide-ranging that the SSN community has decided on a series of Workshops to solidify this. Brussels, Belgium, May 2012 Tucson, AZ, Jan We have a Wiki giving details and presentations: wikia.com/wiki/home The goal is to arrive at a single, vetted series that we all agree on. Switzerland, Sept The SSN workshops are sponsored by the National Solar Observatory (NSO), the Royal Observatory of Belgium (ROB), and the Air Force Research Laboratory (AFRL). 9

10 Correcting for the 20% Inflation Sunspot Number (Official SIDC View) GSN Modern Grand Max? Rcorr = Rofficial * 1.2 before ~1946 This issue is so important that the official agencies responsible for producing sunspot number series have instituted a series of now ongoing Workshops to, if at all possible, converge to an agreed upon, common, corrected series. The inflation due to weighting is now an established and accepted fact That the corrected sunspot number is so very different from the Group Sunspot Number is a problem for assessing past solar activity and for predicting future activity. This problem must be resolved. 10

11 Removing the discontinuity in ~1945, by multiplying Rz before 1946 by 1.20, yields Leaving one significant discrepancy ~

12 9 Number of Groups: Wolfer vs. Wolf Wolf-Wolfer Groups 8 Wolfer Yearly Means Wolfer = 1.653±0.047 Wolf R 2 = Wolfer 2 1 Wolf mm 64X 12 Number of Groups 10 Wolf* Wolfer Wolf 4 2 Wolf 37mm 20X

13 Why are these so different? K-Factors This is the main reason for the discrepancy Observer H&S RGO to Wolfer Begin End Wolfer, A., Zurich Wolf, R., Zurich 2% diff Schmidt, Athens Weber, Peckeloh Spoerer, G., Anclam Tacchini, Rome Moncalieri Leppig, Leibzig Bernaerts, G. L., England Dawson, W. M., Spiceland, Ind Ricco, Palermo Winkler, Jena Merino, Madrid Konkoly, Ogylla Quimby, Philadelphia Catania Broger, M, Zurich Woinoff, Moscow Guillaume, Lyon Mt Holyoke College This analysis K-factors H&S Zürich Classification: A still unresolved question is how Hoyt & Schatten got the K-factors so wrong a b ½ of all groups Wolf couldn t see most a & b groups with his small telescope 13

14 Constructing a Composite Comparing 22 observers that overlap with each other one can construct a composite group number successively back to Schwabe and up to Brunner: 14 Comparison Composite Groups and Scaled Zurich SSN 12 Zurich Composite There is now no systematic difference between the Zürich SSN and a Group SSN reconstructed here by using correct K-factors relative to Wolfer. 14

15 Removing the discontinuity in ~1885 by multiplying Rg by 1.47, yields Only two adjustments remove most of the disagreement and also the evidence for a recent grand maximum ( ) 15

16 Wolf s Original Geomagnetic Data dd' Wolf and Wolfer's Diurnal Ranges of Declination for their Long-running Stations Praha (Prague) - Christiania (Oslo) - Milano (Milan) - Wien (Vienna) ry (nt) Diurnal Range Compared to Scaled International Sunspot Number Today we know that the relevant parameter is the East Component, Y, rather than the Declination, D. Converting D to Y restores the stable correlation, especially around the critical time near 1885 where the GSN begins to deviate R I * Wolf found a very strong correlation between his Wolf number and the daily range of the Declination. Wolfer found the original correlation was not stable, but was drifting with time and gave up on it in

17 Correcting for the 20% Inflation Sunspot Number (Official SIDC View) Rcorr = Rofficial * 1.2 before ~1946 This issue is so important that the official agencies responsible for producing sunspot number series have instituted a series of now ongoing Workshops to, if at all possible, converge to an agreed upon, common, corrected series: The inflation due to weighting is now an established and accepted fact GSN Modern Grand Max? That the corrected sunspot number is so very different from the Group Sunspot Number is a problem for assessing past solar activity. This problem is now resolved: The Group Sunspot Number 17 should not be used anymore.

18 Solar Activity Sunspot Number Monthly Average Ap Index Ap Geomagnetic Index (mainly solar wind speed) B nt Heliospheric Magnetic Field Strength B (at Earth) Inferred from IDV and Observed B (IDV) Heliospheric Magnetic Field at Earth B (obs) Year Activity now is similar to what it was a century ago 18

19 Ludwig Biermann 1951 The Solar Wind Blows all the time and is the expansion of the extremely hot atmosphere into space, visible near the Sun as the Corona : Gene Parker 1958 Expansion is radially outwards Wilcox & Ness, 1964 Out In Dust Ions The pattern of the magnetic spiral rotates with the Sun once in 25 days Magnetic Field Lines are tied to the expanding atmosphere and therefore rooted in the Rotating Sun 19

20 Solar Wind Stealing a Comet Tail Sector Boundary Reconnection Fragile: Comet ion tail inside Sep 30 Oct 1 In One Day 35 Million km or 400 km/sec Oct 2 Comet Encke, 2007/04/20 Comet Morehouse, 1908 札幌 20

21 Sector Boundaries on the Sun From the measured magnetic field we can calculate where the boundary between opposite polarities is. It winds its way across the surface looking like the seam of a baseball N - in + out S Synoptic map from 27 daily strips showing the whole Sun Disk Magnetogram 21

22 Returning to Solar Wind Schulz; Svalgaard; Saito (1974) Sector boundary The Boundary through the Cycle Near the sector boundary the solar wind is denser and slower. As the Sun rotates this builds up spiraling layers of denser plasma wrapping around the Sun many times: Boundary in Perspective Jupiter Vertical cut through the sweeping boundary: 50 AU The flapping sector boundary in time. Note the changing extent 22

23 Cosmic Rays from the Milky Way Galaxy Minimum CR Maximum CR Cosmic Ray Modulation caused by solar cycle variation of current sheet extent and of solar storms Global 8 kg/yr 14 C Global 55 g/yr 10 Be About 30 [secondary] cosmic rays fly through your body every second At maximum, more Cosmic Rays are deflected out of the solar system and do not reach the Earth: Tree Rings Ice Cores When hitting the atmosphere Cosmic Rays produce radioactive Carbon14 and Beryllium10 isotopes 23

24 Drilling for Ice Cores To measure the 10Be concentration and thus the Cosmic Rays thousands of years back in time Machine to count atoms of 10Be one by one Drill to depth of 3000 m Signe Greenland Upside-Down 40,000 Bp Low Field Many CRs Annual Layers in the Ice Cosmic Ray counts are also influenced by the Earth s magnetic field. We can correct for that. 24

25 Getting to the Station on the Ice Hercules C-130 with Skis Rocket assisted Take-Off Low seismic noise, good for detection of Atomic Bombs But my job (in 1967) was to make magnetic observations Not always successful Inge Lehman Station 77.92ºN 39.23ºW, 2400 m (7900 ft),

26 GSN M.M. Cosmic Ray Proxy [Berggren et al.] 26

27 Burning Prairie => Magnetism Foukal & Eddy, Solar Phys. 2007, 245,

28 Birth of an Active Region NOAA 11158, February, 2011 Solar Dynamics Observatory (SDO) All the Sun, All the Time Sunspots grow by the accumulation of smaller spots and pores. Visible Light 28

29 Observed Sunspot Number Divided by Synthetic SSN ( ) R>10 SIDC SWPC 1.2 R> SWPC R ? R R SSN y = x x x R 2 = Observed Sunspot Number Divided by Synthetic SSN ( ) SIDC F SSN obs / SSN* SSN* = 54.7 MPSI month running average Magnetic Plage Strength Index Year ?? R 200 Something is happening with the Sun (b) B Gauss Spots per Group for Locarno Spots per Group declining Umbral Magnetic Field Livingston & Penn No visible spots form Year S/G? ? We don t know what causes this, but sunspots are becoming more difficult to see or not forming as they used to. There is speculation that this may be what a Maunder-type minimum looks like: magnetic fields still present [cosmic rays still modulated], but just not forming spots. If so, exciting times are ahead. 29

30 The Livingston & Penn Data Temp. From 2001 to 2012 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 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. 30

31 Distribution of Sunspot Magnetic Field Strengths Evolution of Distribution of Magnetic Field Strengths Sunspots form by assembly of smaller patches of magnetic flux. As more and more magnetic patches fall below 1500 G, fewer and fewer spots will form Intensity cycle cycle 23 B Gauss Gauss 31

32 Perhaps like this: Magnetic Field Visible Light

33 Working Hypothesis The Maunder Minimum was not a deficit of magnetic flux, but A lessening of the efficiency of the process that compacts magnetic fields into visible spots This may now be happening again If so, there is new solar physics to be learned I ll end with something on TSI and climate 33

34 Removing the discrepancy between the Group Number and the Wolf Number removes the background rise in reconstructed TSI I expect a strong reaction against fixing the GSN from people that explain climate change as a secular rise of TSI and other related solar variables 34

35 Kopp/LASP Some More TSI Reconstructions Crucial question: is there a slowly varying background? I think not. 35

36 TSI (PMOD) not lower at recent Solar minimum Difference PMOD - TIM(SORCE) (W/m 2 ) Degradation y = x x Schmutz,

37 Absurd Extrapolation Based on a decline that did not take place No Ice Age soon, but well in 20,000 years Sunspot Numbers The End The lower solar activity in sunspot numbers may well happen 37