The Rise of Solar Cycle 24: Magnetic Fields from the Dynamo through the Photosphere and Corona and Connecting to the Heliosphere

Part 1: Interior and Photosphere

Subsurface Flows:

Torsional Oscillation (east-west)variation from the mean differential rotation very small signalrelated to the timing of the cycle

Meridional Flow (north-south)very small signalimportant for the timing of the cycle

Frank Hill: observationsMark Miesch : modeling interpretation

Cycle 25??? 2019?-2030?Cycle 23 (1995-2008) Equatorward Branch

Cycle 24 (2008-2019?)Poleward branch Equatorward branch

Torsional oscillation at a depth of 7 Mm

No sign yet of poleward branch flow for Cycle 25.May mean that Cycle 25 will not start until at least 2023

5 m/s

-5 m/s

M. Rempel suggested that the non-appearance of the high-latitude branch may be due to a change in the differential rotation profile that arises from a reduction of the effect

Strong cycles have more rigid differential rotation(magnetic tension tends to reduce rotation shear)

Weak cycles rotate more differentially, i.e. poles slow down BUT Plot had a mean differential rotation subtracted this may mask poleward branch

This hypothesis can be tested

Stay tuned for the next NSO press release !!!

Deep meridional flow:

hard to measureissues with data inversionsseems to increase with depthcomplex cellreturn flow not detected

Meridional Flow

At the Surface: both heliosesimology and correlation trackingtechniques show it poleward + AR band modulation

hard to measure at high latitudesmultiple cells in latitudefaster (1-2 m/s) flow near surface during recent minimum

In contrast, using correlation tracking techniques : David Hathaway finds that the meridional flow decreases with depth and there is a shallow return flow

R. Komm: reliable technique but no agreement on interpretation (longer time scales do not necessarily mean longer-lived cells)data may not indicate a shallow return flow!

What is important for the dynamo model is the return flow at the bottom of the convection zone which hasnot been detected yet Consensus: We do not know much about meridional flow, especially its variation with depth

Gordon Petrie: magnetic flux emergence

first spot Jan 200830deg latitude

Cycle 21 Cycle 22 Cycle 23 Cycle 24

Number of images with fields stronger than 1 kG

strong recovery after verydeep minimum

current activity level <50% of Cycle 21-23 maxima in terms of maximum field strength

Cycle 21 Cycle 22 Cycle 23 Cycle 24

magnetic butterfly covering 37 years of NSO data !!!long minimum

hemispheric asymmetry: south more active at the end of cycle 23north more active at the start of cycle 24, still more active now not seen in the preceding cycles but cycle 20 shows noticeable asymmetry

POLAR MAGNETIC FIELDS

weak polar magnetic fields (consistent with the observed decrease in open flux in the heliosphere)

A. Munoz-Jaramillo: how important are polar fields for the dynamo?Are they a by-product or the seeds for the next cycle(s)?

This is also important for the heliosphere-dynamo connection

What was in the press releaseThe raw data presented at Space Weather Workshop 2010

Weakening Magnetic Fields in Sunspot

Doug Biesecker: challenged the observational evidence that we are entering a Maunder Minimum

Solar Max Solar Minno obvious reason that a straight line is the appropriate fit to these data. A curve that follows the solar cycle may in fact provide a better reduced chi square.

Cycle 21(10.3 yrs)

Cycle 22(10.0 yrs)

Cycle 23(12.2 yrs)

The slowing ‘rush to the poles’

Cycle 24 started ‘late.’ Cycle 23 was 12 years long, 2 years longer than the previous two cycles. Iron emission seems to appear right as expected, 12 years after the last one

The Rise of Solar Cycle 24

Part 2:

Corona & Heliosphere

9:45-11:00:polar fields (Dick Altrock)

11:30-12:45:open flux (Janet Luhmann & Nathan Schwadron)

14:00-17:00:open flux & heliosphere (cont.)

The Rise of Solar Cycle 24

Part 2:

Corona & Heliosphere

we will be in room Cabaret today

we hope you will join us!