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

Solar Cycle 24 is different from recent cycles

l follows longest/deepest minimum in 100 years

l weakest cycle of the space age

l interesting N/S asymmetry (also seen at the poles)

SDO/HMI MagnetogramMar 15 2013

USAF/NOAA data

cycle 22cycle 21

l north/south asymmetry started in 2005

current spot latitudeN = 14degS = -18deg~ 2-year time lag

The two hemispheres have been out of phase for an unusually long timeSouth activity has increased recently

The differences started in the cycle 23

USAF/NOAA data

l significant decrease of very large spots in cycle 23

The differences started in cycle 23

~1400

SDO/AIA May 11 2012

l significant decrease of very large spots in cycle 23

The differences started in cycle 23

l spots of all sizes have decreased in cycle 24, especially the large ones

~1400

AIA May 11 2012

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

Sunspots are not fainter

l spots have the expected brightness for a given area

SFO/CFDT1 1986-presentlongest record of full-disk photometric measurements

sunspots are not fainterthere are just fewer of them……which is normal for weak cyclesthis is why weakcycles are weak!

San Fernando Observatory/CFDT1

cycle 22cycle 23

McMath-Pierce spot observations…..…. a lively debate

Courtesy of L. Svalgaard

brightness increasemagnetic field decline

if trend continues almost no spots in cycle 25 !!Livingston, Penn, & Svalgaard 2012

but is this trend real?

spot brightness

magnetic field

McMath-Pierce spot observations…..…. a lively debate

brightness increasemagnetic field decline

spot brightness

CFDT1

San Fernando Observatory/CFDT1

San Fernando Observatory/CFDT2

SOHO/MDI

find spot brightness stable in time

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

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

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

There is one instrument that can resolve the ongoingcontroversy:

MLSO/PSPT

1” spatial resolution0.1% photometric precision1998-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

McMPrestoredimage0.2”

AIA full res0.6”

AIAreduced to 2.4”

CFDT15.0”

AIA Aug 27 2012

CFDT1 low spatial resolutionbut 1% photometric precision

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 ishidden

If 3.5-year rotational Mean is subtractedpolarward branch reappears!R. Howe et al. (ApJ 2013)