1. Update on Cycle 24 Giuliana de Toma collaborators: Gary Chapman, Angie Cookson, Dora Preminger data sources: CSUN/SFO, USAF/SOON, McMath, SOHO/MDI, SDO/AIA SPD 2013 Press Conference

2. Solar Cycle 24 is different from recent cycles follows longest/deepest minimum in 100 years weakest cycle of the space age interesting N/S asymmetry (also seen at the poles) SDO/HMI Magnetogram Mar 15 2013 USAF/NOAA data cycle 22cycle 21

3. north/south asymmetry started in 2005 current spot latitude N = 14deg S = -18deg ~ 2-year time lag The two hemispheres have been out of phase for an unusually long time South activity has increased recently The differences started in the cycle 23 USAF/NOAA data

4. significant decrease of very large spots in cycle 23 The differences started in cycle 23 ~1400 SDO/AIA May 11 2012

5. significant decrease of very large spots in cycle 23 The differences started in cycle 23 spots of all sizes have decreased in cycle 24, especially the large ones ~1400 AIA May 11 2012

6. Hevelius drawing in 1644 (one year before the Maunder Minimum started) There were large spots on the Sun before the Maunder Minimum We still do not know how and why the Maunder Minimum started We had small cycles before and the Sun did not go into a Maunder Minimum

7. Sunspots are not fainter spots have the expected brightness for a given area SFO/CFDT1 1986-present longest record of full-disk photometric measurements sunspots are not fainter there are just fewer of them… …which is normal for weak cycles this is why weak cycles are weak! San Fernando Observatory/CFDT1 cycle 22 cycle 23

8. McMath-Pierce spot observations….. …. a lively debate Courtesy of L. Svalgaard brightness increase magnetic field decline if trend continues almost no spots in cycle 25 !! Livingston, Penn, & Svalgaard 2012 but is this trend real? spot brightness magnetic field

9. McMath-Pierce spot observations….. …. a lively debate brightness increase magnetic field decline spot brightness CFDT1 San Fernando Observatory/CFDT1 San Fernando Observatory/CFDT2 SOHO/MDI find spot brightness stable in time

10. another explanation for this trend McMath-Pierce dataset is not homogeneous - fewer data early on - no small spots included in early data this introduces a bias no trend in the most recent data that do not include small spots spot brightness magnetic field

11. another explanation for this trend McMath-Pierce dataset is not homogeneous - fewer data early on - no small spots included in early data this introduces a bias no trend in recent data that include small spots spot brightness CFDT1: all spots

12. another explanation for this trend McMath-Pierce dataset is not homogeneous - fewer data early on - no small spots included in early data this introduces a bias The trend is not caused by a real change in the Sun but by selection effects spot brightness CFDT1: with small spots removed in early years

13. There is one instrument that can resolve the ongoing controversy: MLSO/PSPT 1” spatial resolution 0.1% photometric precision 1998-present most accurate record of spots and faculae Collaboration with Gary Chapman (CSUN/SFO) & Mark Rast (CU/LASP) Stay tuned for more news on this! Blue cont. 409.4nm Mauna Loa Solar Observatory

15. McMP restored image 0.2” AIA full res 0.6” AIA reduced to 2.4” CFDT1 5.0” AIA Aug 27 2012 CFDT1 low spatial resolution but 1% photometric precision

16. M. Rempel (ApJ Lett 2012) proposed the non-appearance of the high-latitude branch was be due to a change in the differential rotation profile (caused by the decrease in cycle amplitude) Strong cycles have more rigid differential rotation (magnetic tension tends to reduce rotation shear) Weak cycles rotate more differentially, i.e. poles slow down If a mean differential rotation profile is subtracted the polarward branch is hidden If 3.5-year rotational Mean is subtracted polarward branch reappears! R. Howe et al. (ApJ 2013)