Large Scale flows from Large Scale flows from local helioseismologylocal helioseismology

Irene González HernándezIrene González HernándezNational Solar Observatory (Tucson, AZ)National Solar Observatory (Tucson, AZ)

ContentsContents Solar Rotation Meridional Circulation

OverviewSolar Cycle variationCountercellExtra circulation in the active beltsDeep meridional circulation

“Banana” cells and supergranulation

Ring-diagrams technique Ring-diagrams technique

Hill, F; 1988, ApJ,333,996

Patrón, J.; Hill, F.;Rhodes, E.J.,Jr.;Korzennik,S. G. and Cacciani,A., 1995, ApJ, 455,74

Giles et al., 1997 Nature, 390, 52

Giles, P. PhD thesis

González Hernández et al,.,2000, ApJ

16o 1664

min

Flows from rings: synoptic Flows from rings: synoptic mapsmaps

Courtesy of R. Komm

Courtesy of Rudi Komm

Differential Rotation Differential Rotation

Radial variation of the mean rotation rate, Radial variation of the mean rotation rate, shifted to give a zero rate at the surface, shifted to give a zero rate at the surface, for global inversions (curves mark error for global inversions (curves mark error bounds) of MDI data and local inversions of bounds) of MDI data and local inversions of MDI (filled circles) and GONG (open MDI (filled circles) and GONG (open diamonds) data at latitudes 0(top left), diamonds) data at latitudes 0(top left), 15(top right), 30 (bottom left) and 45 15(top right), 30 (bottom left) and 45 (bottom right).(bottom right).

Howe, R. et al., 2006, Solar Physics ,235,1.Howe, R. et al., 2006, Solar Physics ,235,1.

15 degree patches

30-degree patches

North-South asymmetryNorth-South asymmetry

The latitudinal variation is The latitudinal variation is most likely a consequence of most likely a consequence of the solar-cycle variation of the the solar-cycle variation of the zonal flow, the torsional zonal flow, the torsional oscillation pattern. oscillation pattern.

The zonal flow is The zonal flow is predominantly faster in the predominantly faster in the southern hemisphere that in southern hemisphere that in the northern one. This the northern one. This differences increase with differences increase with latitude about 25-degrees, and latitude about 25-degrees, and with depth.with depth.

Zaatri, A. et al, 2006, Solar Zaatri, A. et al, 2006, Solar Physics, 236,227Physics, 236,227

Temporal variation of the zonal flow in the Northern (dark grey) and Southern (light grey) hemisphere at four

latitudes and four depths. The surface rotation rate has been subtracted (Snodgrass, 1984). The line thickness represents about two standard deviations of the formal undertainty. The top row shows, for comparison, the time

scale in Carrington Rotations.

Torsional Oscillation Torsional Oscillation (local helioseismology)(local helioseismology)

Torsional oscillation from ring-diagram analysis: MDI-GONG combo that I showed at the AGU meeting. MDI before mid-2001, GONG after. The flows are averaged in depth over 4-10 Mm. Bands of faster (or slower) rotation move toward the equator. The fast band of cycle 24 appears before there is any surface activity present. The new fast band is stronger in the northern hemisphere indicating that the activity will be stronger in this hemisphere.

Courtesy of R. Komm

Meridional circulation: Meridional circulation: Surface ObservationsSurface Observations

Komm, Horward & Harvey 1993, Solar Physics, 147, 207

Meridional circulation derived from the motion of small magnetic features

Surface ObservationsSurface Observations

Komm, Horward & Harvey 1993, Solar Physics, 147, 207

Cycle variations of the meridional flows from surface observations of small magnetic features

“..kinematic dynamo simulations which demonstrate that a fast meridional flow in the first half of a cycle, followed by a slower flow in the second half, reproduces both characteristics of the minimum of sunspot cycle 23. Our model predicts that, in general, very deep minima are associated with weak polar fields. Sunspots govern the solar radiative energy and radio flux, and, in conjunction with the

polar field, modulate the solar wind, the heliospheric open flux and, consequently, the cosmic ray flux at Earth.”

Nandy, D., Muñoz-Jaramillo, A., Martens, P. C. H. 2011, Nature

Meridional CirculationMeridional Circulation

Hathaway and Rightmire, 2010

Meridional circulation variation Meridional circulation variation with the solar cyclewith the solar cycle

Meridional flows obtained

from 34.5 Mm (solid curves) and 69 Mm (dash-dotted curves) for different Carrington rotations. (b) Residual meridional flows after the flows of CR1911 have been subtracted from each rotation. Shaded regions are the same as Fig. 2. The error bars may be underestimated, because the errors from flows of CR

1911 are not included.

Zhao and Kosovichev, ApJ, 2004

Meridional Circulation variation Meridional Circulation variation with the solar cyclewith the solar cycle

Temporal variation of the fitted polynomial to the meridional circulation observations at a depth of 5.8 Mm. A symmetrical plot averaging ring-diagram analysis of GONG data for both hemispheres is shown. Positive velocities are taken toward each respective pole. The B0 effect is clearly seen superimposed in the results, however the long term trend of the amplitude increase is not associated with this artifact [7].

González Hernández et al., 2010, ApJ

Comparison between the last Comparison between the last two minimatwo minima

Courtesy of R. Komm

Meridional flow averaged over Carrington rotation 1909-1911 from MDI data (top) and CR 2076-2080 (bottom) from GONG data.

TOP: minimum of cycle 22-23

BOTTOM: minimum of cycle 23-24

Flows appear stronger during the recent minimum than in the previous one.

Meridional circulation countercellMeridional circulation countercell

Haber et al., 2002, ApJ

McDonald & Dikpati (2003)

(Figure from Dikpati et al., 2010, Geophys. Research.)

Meridional circulation countercellMeridional circulation countercell

González Hernández et al, 2006

Gonzalez Hernandez et al., 2006, ApJ.

Meridional circulation countercellMeridional circulation countercell

González Hernández et al, 2006

Gonzalez Hernandez et al., 2006, ApJ.

Meridional circulation countercellMeridional circulation countercell

González Hernández et al, 2006

Dikpati, M. et al. 2010, GeoRL

Ulrich, R. 2010. ApJ

Motivation: Solar DynamoMotivation: Solar DynamoYearly results for the meridional circulation function. Each day throughout each year is treated independently with the averages and standard deviations being calculated from the set of daily results. The lines connect the average values while the error bars give the error of the mean based on the number of days in the annual set.

Meridional Circulation with HMI (the B0 effect!)

Results obtained by applying ring-diagram analysis technique to the HMI data averaged over Carrington rotation 2101 (HMI rings team)

Results obtained by applying ring-diagram analysis technique to the HMI data averaged over Carrington rotation 2106 (HMI rings team)

Meridional circulation at high Meridional circulation at high latitudeslatitudes

Extra circulation in the Extra circulation in the active beltsactive belts

Yearly averages of the meridional flow obtained by ring-diagram analysis of continuous GONG data at four different depths. The variation with the solar cycle clearly observed at the superficial layers is less pronounced at deeper layers. The extra circulation (bumps) is also clearly visible in the shallow layers.

González Hernández, et al.. 2010, ApJ Left: Longitudinal averages of

surface horizonal flows. Solid lines: before excluding active region areas, dashed lines: after excluding active regions.Right: Sketch of surface flows around active regionsGizon, L. 2004, Solar Physics, 224, 217

Extra circulation in the active Extra circulation in the active belts: another component of the belts: another component of the

torsional oscillation?torsional oscillation?Temporal variation of the meridional circulation residuals (or jets) at a depth of 5.8 Mm (bottom panel). Positive velocities are directed towards the poles. A symmetrical plot averaging both hemispheres is shown in the bottom panel [7]. The top panel shows the location and magnetic strength of the activity during the same period (calculated from MDI synoptic magnetograms). The existence of the residuals, or extra circulation, at medium-high latitudes before the onset of activity of solar cycle 24 confirmed previous results showing the persistence of such residuals after removing the contribution from active regions [6].

González Hernández et al., 2008, 2010

Solar Cycle 23 meridional Solar Cycle 23 meridional circulation residuals from MDIcirculation residuals from MDI

Basu & Antia, 2010, ApJ, 717, 488

Speed of the antisymmetric component of the meridional flows plotted as a function of latitude and time at four depths. To make the plot symmetric, the sign of the flow has been reversed in the southern hemisphere. Thus, positive velocity points toward the poles in both hemispheres. Each data point is assumed to represent the time interval between the mid-points with neighboring sets. The actual time covered by each set (which is typically one Carrington rotation) is usually much smaller than the interval between the sets.

Prospects for Detection of the Prospects for Detection of the Deep Solar Meridional Deep Solar Meridional

CirculationCirculation

Courtesy of S. Kholikov

Meridional travel time differences as a function of latitude and propagation depth (top). Measurements are averaged over the period 1995-2009. The increase of time differences at a depth of about 0.77RSun can be an indication of large perturbations of the meridional flow or some other properties of the deep convective zone. Inversions of these travel time differences are needed in order to get realistic estimations of the actual flows. The lower panel shows the precision of measurements. In this figure, the horizontal axis correspond to the same depths as the top panel, but has been labeled in units of separation distance for cross-correlation analysis. It should be noted that error bars for most measurements are smaller than 0.02 seconds [8].

Long-term surface observationsLong-term surface observations

Hathaway and Rightmire 2010, Science, 327, 1350

Recent Surface ObservationsRecent Surface Observations

Ulrich, R. 2010, ApJ, 725, 658

“…that the differences in surface meridional flow speed between the solar plasma and magnetic patterns can be explained as due to the effects of surface turbulent magnetic diffusion.”Dikpati, M., Gilman, P. and Ulrich, R. 2010, AstroPh

Multiwavelength helioseismology:Multiwavelength helioseismology:HMI/AIAHMI/AIA

GONG/MOTH Subsurface flow maps for Jan 18, 2003(left) and Jan 19, 2003 (right). Blue arrows show flows obtained from the Ni line (~200km from base of photosphere) and red from the K line (~420 Km from base of photosphere).DifferencesJain, K. et al, 2006

Supergranulation and “banana” Supergranulation and “banana” cellscells

Nagashima, K. et al. 2011, ApJ, 726L, 17: Noth-South aligment of the supergranulation in the polar regions using time-distance analysis (SOT/Hinode).

Differences

Featherstone, N. A. et al, 2006/2007 (SPD/AAS): Helioseismic Searches for the Elusive Giant Cells of Convection

Rudi Komm (private communication): Long term giant “banana” cell like structures in the subsurface layers

Conclusions and future workConclusions and future work1. Solar cycle variation

2. Depth profile /deep meridional circulation

3. High latitudes Meridional circulation countercells? Polar branch of the torsional oscillation

4. Large cells and supergranulation (lot of work to be done!)

Understand the systematics in the different analysis methods Global helioseismology inferences (Gough & Hindman)of mc SDO: HMI/AIA Different vantage points