Flows and the Photospheric Magnetic Field Dynamics at Interior – Corona Interface

1. Flows and the Photospheric Magnetic FieldDynamics at Interior – Corona Interface Brian Welsch, George Fisher, Yan Li, & the UCB/SSL MURI & CISM Teams HMI Team Mtg., 2006 M1-H2: Mag. Activity

2. The ‘Store and Release Paradigm’ (cf., earthquakes) motivates studying photospheric flows. • Slow photospheric motions (v ~ 1 km/s) add magnetic energy to the coronal field, as Poynting flux. -- E x B  -(v x B) x B • The “frozen-in flux” condition prevents relaxation BB(P), so free energy is stored in the corona – “latency.” • With enough free energy, the corona reaches an unstable configuration (??) and “spontaneously” relaxes toward B(P). Most CME models – flux cancellation, breakout, tether cutting, kink instability – accord with this picture. (But even Chen’s [1996] “energy injection” paradigm also invokes photospheric flows!) HMI+AIA, M1-H2: Mag. Activity

3. Velocity inversions generate a 2D map v(x1,x2)from some 2D image, f1(x1,x2), to another, f2(x1,x2). The map depends upon: • the difference f(x1,x2) = f2(x1,x2) – f1(x1,x2) • assumption(s) relating v(x1,x2) to f/t, e.g.: • continuity equation, f/t + t(vtf) = 0, or • advection equation, f/t + (vtt)f = 0, etc. We apply Fourier Local Correlation Tracking (FLCT, Welsch et al. 2004), which assumes advection, to magnetograms. (More on FLCT in M3: Mag. Data Products, Thurs.)

4. Demoulin & Berger (2003) argued that LCT applied to magnetograms does not necessarily give plasma velocities. Motion of flux across photosphere, uf, can be a combination of horizontal & vertical flows acting on non-vertical fields. uf vnBh-vhBn is the flux transport velocity • uf is the apparent velocity (2 components) • v is the actual plasma velocity (3 comps)

5. Ishii et al. (1998) explained complicated photospheric evolution in AR 5395 in terms of a complex, 3D flux system. (a) schematic magnetogram; (b) sketch of 3D structure HMI+AIA, M1-H2: Mag. Activity

6. We have implemented a preliminary, automated “Magnetic Evolution Pipeline” (MEP). http://solarmuri.ssl.berkeley.edu/~welsch/public/data/Pipeline/ • cron checks for new magnetograms with wget • New MDI magnetograms are downloaded, deprojected, and tracked using FLCT. • The output stream includes deprojected m-grams, FLCT flows (.png graphics files & ASCII data files), and tracking parameters. • Full documentation & all codes (and bugs!) are on line. HMI+AIA, M1-H2: Mag. Activity

7. Electric fields derived from pipelined velocities will be used as inputs for MHD models of the solar corona. • HMIs vector magnetogram coverage will improve accuracy of MHD boundary condition. • Hoped-for near term (1-2 years) improvements: • Extension of disk-side pipeline to global pipeline, via estimation of far-side magnetic evolution. • Feature tracking, for estimation of flux cancellation rates. • Coronal models, e.g., magnetic charge topology (MCT). HMI+AIA, M1-H2: Mag. Activity

8. References • Démoulin & Berger, 2003: Magnetic Energy and Helicity Fluxes at the Photospheric Level, Démoulin, P., and Berger, M. A. Sol. Phys., v. 215, # 2, p. 203-215. • Ishii et al, 1998:Emergence of a Twisted Magnetic Flux Bundle as a Source of Strong Flare Activity,Ishii, T.T., Kurokawa, H., & Takeuchi, T.T., ApJ, v. 499, 898. • Schuck, 2005:Local Correlation Tracking and the Magnetic Induction Equation,Schuck, P.,ApJ, v. 632, L53. • Welsch et al., 2004:ILCT: Recovering Photospheric Velocities from Magnetograms by Combining the Induction Equation with Local Correlation Tracking, Welsch, B. T., Fisher, G. H., Abbett, W.P., and Regnier, S., ApJ, v. 610, #2, p. 1148-1156. HMI+AIA, M1-H2: Mag. Activity