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
Feb 24, 2016
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)