Planning for Helioseismology with SO/PHI Birch, Gizon, & Hirzberger Max Planck Institute for Solar System Physics

Outline Motivation Synthetic data for helioseismology with PHI Forward modeling Some potential targets

Motivation Which helioseismology observations would most efficiently provide new science? How to model new approaches to helioseismology (e.g. stereoscopic imaging of base of convection zone)?

The two ingredients Synthetic data – Predict noise levels and systematic effects Forward models – Predict signal that would be expected for particular targets of interest – Enables estimates of required observation duration T (S/N goes as T 1/2 for steady signal)

Synthetic data: an example (see Loeptien poster) Begin from Stein & Nordlund simulation of solar convection Simulation domain 96x96x20 Mm 3 We have about three hours of data (one minute cadence) now at MPS Compute line profiles (Spinor) Simulate instrument effects (SOPHISM, poster #57)

Synthetic data: example results See poster by Loeptien, and poster #57 for SOPHISM code

Synthetic data: power spectra See poster by Loeptien

Forward models: approaches First Born approximation (single scattering) – Useful for weak perturbations – Can apply adjoint method (e.g., Hanasoge et al & 2012) to include systematic effects Numerical wave propagation – Generate forward models for arbitrarily strong perturbations (e.g., sunspots: Cameron et al. 2011) Realistic simulations – Directly simulate feature of interest (e.g, Rempel et al. 2009)

Forward models: wave propagation Gizon et al Cameron et al. 2008

A few potential targets Near-surface shear layer in rotation Radial shear reverses sign around 50° latitude Flows of order 10 m/s, global scale Use FDT Polar convective flows (at supergranulation scale) Flows of about 150 m/s, length scale 30 Mm Use HRT Active longitudes at base of convection zone Stereoscopic helioseismology Use FDT plus another helioseismology instrument Test of concept and exploration

Future work Continue working with convection simulations – Noise levels for local helioseismology – Data compression – How does PHI see solar oscillations? Develop simulations for FDT – Global-mode summation + Spinor Forward models for interesting targets Ideally, this would be a community effort There is a lot to do!

The End