The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Overview and Performance

By J. Todd Hoeksema, Yang Liu, K. Hayashi, Xudong Sun, J. Schou, S. Couvidat, A. Norton, Monica G. Bobra, R. Centeno, K. Leka and 2 more. 2014

541 citations recorded by the source corpus.

The Helioseismic and Magnetic Imager (HMI) began near-continuous full-disk solar measurements on 1 May 2010 from the Solar Dynamics Observatory (SDO). An automated processing pipeline keeps pace with observations to produce observable quantities, including the photospheric vector magnetic field, from sequences of filtergrams. The basic vector-field frame list cadence is 135 seconds, but to reduce noise the filtergrams are combined to derive data products every 720 seconds. The primary 720 s observables were released in mid-2010, including Stokes polarization parameters measured at six wavelengths, as well as intensity, Doppler velocity, and the line-of-sight magnetic field. More advanced products, including the full vector magnetic field, are now available. Automatically identified HMI Active Region Patches (HARPs) track the location and shape of magnetic regions throughout their lifetime.The vector field is computed using the Very Fast Inversion of the Stokes Vector (VFISV) code optimized for the HMI pipeline; the remaining 180∘ azimuth ambiguity is resolved with the Minimum Energy (ME0) code. The Milne–Eddington inversion is performed on all full-disk HMI observations. The disambiguation, until recently run only on HARP regions, is now implemented for the full disk. Vector and scalar quantities in the patches are used to derive active region indices potentially useful for forecasting; the data maps and indices are collected in the SHARP data series, hmi.sharp_720s. Definitive SHARP processing is completed only after the region rotates off the visible disk; quick-look products are produced in near real time. Patches are provided in both CCD and heliographic coordinates.HMI provides continuous coverage of the vector field, but has modest spatial, spectral, and temporal resolution. Coupled with limitations of the analysis and interpretation techniques, effects of the orbital velocity, and instrument performance, the resulting measurements have a certain dynamic range and sensitivity and are subject to systematic errors and uncertainties that are characterized in this report.

Subfields: Astronomy and Astrophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/a93639aa19c6a8c81ad87d00902db2d4eb5825ed

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Citations in the corpus

WHY IS THE GREAT SOLAR ACTIVE REGION 12192 FLARE-RICH BUT CME-POOR? (2015, methodology): “Each magnetogram is made from filtergrams taken within a ∼22.5 minute averaging window, which has a uniform weight for the center of ∼7 minutes and less contribution from the edges (Hoeksema et al. 2014).”
Solar Force-free Magnetic Fields (2012, methodology): “The SDO/HMI-vector magnetic field pipeline (see Hoeksema et al. 2014, for details) uses the minimum energy method for the disambiguation in active regions.”
The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs – Space-Weather HMI Active Region Patches (2014, methodology): “For a detailed summary of calibration procedures and the differences between the NRT and definitive input data, see Hoeksema et al. (2014). ii) NRT HARP geometry is determined as soon as possible, before the full life cycle of the region is known.”
SOLAR FLARE PREDICTION USING SDO/HMI VECTOR MAGNETIC FIELD DATA WITH A MACHINE-LEARNING ALGORITHM (2014, background): “These pixels are defined as both those that (i) reside within the orange-colored magnetic structure identified in panel five and (ii) satisfy a high-confidence disambiguation threshold (indicated by the white pixels in panel six; see Hoeksema et al. (2014) for more details).”