Braun AIA/HMI Feb Helioseismic holography of Solar Subsurface Flows : progress & prospects NorthWest Research Associates Colorado Research Associates Division Doug Braun NWRA / CoRA

Braun AIA/HMI Feb A. Birch C. Lindsey NWRA / CoRA with input from:

3Braun AIA/HMI Feb 2006 outline “calibrated” (near-surface) flows CR1988 “calibrated” (near-surface) flows CR1988 supergranulation supergranulation AR flows AR flows AR flows vs. depth: travel-time asymmetries AR flows vs. depth: travel-time asymmetries inversions inversions zonal and meridional flows zonal and meridional flows what’s next? what’s next?

4Braun AIA/HMI Feb 2006 H - = ingressionH + = egression helioseismic holography

5Braun AIA/HMI Feb 2006 phase-correlation holography egression, ingression: correlation: travel-time perturbation: correlation phase: (space-frequency domain) sensitive to refractive perturbations at focus

6Braun AIA/HMI Feb 2006 phase-sensitive holography of flows egressions and ingressions in 4 quadrants: e.g. E-W correlation phase: velocity: WE N S

7Braun AIA/HMI Feb 2006 “calibrated” near surface flows holography phase signatures for focus=3Mm, calibrated from difference between two tracking rates holography phase signatures for focus=3Mm, calibrated from difference between two tracking rates nearly equivalent to inversion for 3Mm with following averaging kernel nearly equivalent to inversion for 3Mm with following averaging kernel

8Braun AIA/HMI Feb 2006 supergranulation: horizontal divergence vertical vorticity 27-hr time averages

9Braun AIA/HMI Feb 2006 vertical vorticity of SG as a result of Coriolis force on divergence: confirms time-distance f- mode results of Duvall & Gizon (2000)

10Braun AIA/HMI Feb 2006 power spectra of supergranulation (divergence) 10° latitude B=0 B = 45° in the fashion of Gizon, Duvall & Schou (2003)

11Braun AIA/HMI Feb 2006 Carrington rotation 1988

12Braun AIA/HMI Feb 2006 vertical vorticity (smeared to 7.5°) vort v h = (1/cosB)  ( cosB v B ) /  L – (1/cosB)  v L /  B

13Braun AIA/HMI Feb 2006 (5.8 day-averaged) flow properties of ARs in CR1988 For near-surface (e.g. 3Mm): ARs rotate faster than quiet Sun (this shear can give rise to “bipolar” vorticity signature) Inflows in plage; outflows in spots No net vorticity signatures in ARs (but small number statistics?)

14Braun AIA/HMI Feb 2006 horizonal divergence with depth horizonal divergence with depth (smeared to 1.0 deg) focus = Mm At all depths, “outflow” signatures from sunspots dominate: are these actual deep outflows?

15Braun AIA/HMI Feb 2006 the showerglass FAQ what is it? it’s a hypothesis about possible strong, even dominant, contribution to helioseismic signatures (e.g. amplitude or phases) from surface magnetic fields why do you call it a showerglass? the phase and amplitude perturbations hypothesized vary significantly over small spatial scales, and may have consequences for imaging fine structure below the surface in a fashion similar to looking through a showerglass (see Lindsey & Braun 2005a,b). what’s this business about “correcting” it? the “correction” is an experiment, deriving from optical terminology. we are devising ways to assess the existence, and properties, of the hypothesized showerglass. measuring and removing a surface phase, derived from a magnetogram, is one such test. it is not a requirement for local helioseismology, or a suggested pipeline procedure. doesn’t this phase subtraction just take out everything? or mostly everything? this is the subject of ongoing research. it’s designed to take out surface phases from the surrounding pupil (and not at the subsurface “focus”). if “subsurface” structure disappears when this is done, this may lead to a “uniqueness” problem: how do we distinguish between a showerglass-caused feature and a real subsurface one? why should we care? if it exists, it’s probably telling us interesting physics about magnetic fields, it may have important diagnostic potential, we may also figure out how to detect weaker perturbations below it.

16Braun AIA/HMI Feb 2006 assessing showerglass phase Correlate surface signal with ingression or egression (full pupil) focused at surface Correlate ingression (a quadrant) with egression (opposite quadrant) focused at some depth making subsurface measurements

17Braun AIA/HMI Feb 2006 focus depth = 3 Mm 5 Mm 7 Mm raw data showerglass phases removed horizontal flow signatures: horizontal flow signatures: removing the phase asymmetry

18Braun AIA/HMI Feb 2006 horizontal flow inversions for now, not taking out phase asymmetries from the horizontal flow signatures for now, not taking out phase asymmetries from the horizontal flow signatures will retain flexibility of whether or not this is done to assess the impact a full inversion taking into account horizontal, vertical flows, and magnetic effects will probably not be in place by HMI launch inversions have been explored for small-scale (supergranulation) and longitudinal averaged flows inversions have been explored for small-scale (supergranulation) and longitudinal averaged flows the latter is illustrated next the latter is illustrated next

19Braun AIA/HMI Feb 2006 zonal and meridional flows

20Braun AIA/HMI Feb 2006 inversions multi-channel deconvolution algorithm (for 3D case) these rotation and meridional inversions are only 1D (depth) averaging kernels (from Green’s functions under Born approx.) OLA method regularization by hand solutions for two depths are shown (3Mm and 14 Mm)

21Braun AIA/HMI Feb 2006 zonal data and inversions 3 Mm14 Mm

22Braun AIA/HMI Feb 2006 zonal and meridional inversions

23Braun AIA/HMI Feb 2006 HH code development needed for HMI fix astigmatism problem move to spherical coordinates inversions f mode higher frequencies

24Braun AIA/HMI Feb 2006 larger (science-related) issues to address: is there anything else other than AR divergence sigs., SG, zonal and meridional flows? (as if these weren’t enough!) travel-time asymmetries in magnetic regions understanding physics extracting flow signatures from other (interesting) effects vertical flows? directly? assume mass-conservation? combining or using surface flows in inversions, models

25Braun AIA/HMI Feb 2006 further information: NASA (LWS and SR&T programs) NSF (Stellar Astronomy and Astrophysics program) support: