The Chromosphere and Prominence Magnetometer (ChroMag) is part of the COSMO suite of instruments at the Mauna Loa Solar Observatory (MLSO), designed to infer the magnetic field within and at the base of the Solar Corona.

ChroMag consists of a 13cm refractive telescope that feeds a narrow-band Lyot filter imaging polarimeter. It was designed to obtain relatively-high cadence synoptic full disk measurements of the four Stokes parameters in a number of Photospheric and Chromospheric spectral lines. The tunable Lyot filter system coupled with the narrow-band pre-filters, enable a spectral resolution between 23500 and 32000. ChroMag images have a field-of-view of 2.5 solar radii with a spatial resolution of 2.5”. The default targeted spectral lines comprise a suite of Chromospheric diagnostics (He I 587.6 nm, He I 1083.0 nm, Hα 656.3 nm, Ca II 854.2 nm) as well as the Photospheric Fe I 617.3 nm line used by the SDO/HMI instrument. The instrument allows the flexibility to include three more spectral diagnostics anywhere in the range between 587.6 and 1083.0 nm.

The different Chromospheric lines are complementary in the sense that some enable on disk dynamics and magnetic field diagnostics whilst others are more suited for off-limb measurements of prominences and spicules. The Fe I line will provide the Photospheric magnetic context as well as a means to easily co-register with data from other instruments.

Current status — We are currently looking at a 2022 deployment to the Mauna Loa Solar Observatory.

Data products — The ChroMag team will put out a number of low- and high-level data products that will become available as the calibration and interpretation tools are developed. They are listed here, in order of increasing complexity:

  • Calibrated full Stokes spectral scans of all of the measured spectral lines.
  • Photospheric Dopplergrams and vector-magnetograms
  • Chromospheric H-alpha and Ca II 8542 Dopplergrams
  • Chromospheric vector-magnetograms of on disk active regions and filaments, and off limb prominences.
Ca II 8542 Å image taken with ChroMag

Ca II 8542 Å image taken with ChroMag during its first test campaign at NCAR's Mesa Lab (Boulder, CO) in the Summer of 2013.

Stay tuned for upcoming ChroMag data in 2022!