S/N and Polarimetry With HMI Bruce W. Lites High Altitude Observatory National Center for Atmospheric Research HMI Team Meeting, Palo Alto, 1-2 May 2003 2 May 2003

Significant Considerations for S/N and Accuracy of Vector Magnetic Field Inversions Results are compromised by: Spectral resolution Spectral sampling Noise level Detector full-well issues: non-linearity, intensity margin Duty cycle of instrument Accuracy of measured instrument spectral profile Bruce Lites, HMI Team Mtg., 2 May 2003

Noise Simulations with ASP Data

Realistic Simulations? HMI Vector field tests so far only indicate the best case: inversions are initialized from the solution, or very close to it Realistic simulations must account for the issue of initialization New pattern recognition techniques (principal components analysis, neural network, support vector machine) do not rely on initial guess, but also may substantially “miss” the solution if the data are too noisy

Recommendation With the HMI CCD source now in question, an opportunity exists to examine the choices for detectors with a view of larger full-well capacity, or With Solar-B, the technology exists for space instrumentation to do rapid readout/summing of images