Upgraded COronal Multi-channel Polarimeter
The Upgraded Coronal Multi-channel Polarimeter (UCoMP) is a 20-cm aperture Lyot coronagraph with a Stokes polarimeter and a narrow-band electro-optically tuned birefringent filter. It can image the intensity, full Stokes polarization, Doppler shift and line width across coronal emission lines in the visible and near-IR. The UCoMP is an upgrade of the Coronal Multi-channel Polarimeter (CoMP) instrument (Tomczyk, Card, Darnell et al., 2008); see Table 1 for performance comparison. The expanded capabilities of UCoMP provide polarization measurements over a wide range of coronal temperatures and out to greater coronal heights to explore the magneto-thermal structure of the corona in coronal holes, ‘quiet’ corona and active regions. The evolution of CMEs from build-up to eruption can be explored and MHD wave observations can be viewed to much greater heights, and over a wide range of coronal conditions. The tunable filter allows UComp to combine the strengths of simultaneous 2-D imaging and high-resolution spectroscopy into a single instrument. UCoMP is located at the Mauna Loa Solar Observatory (MLSO) operated by HAO/NCAR. UCoMP was installed in the spring of 2021, began acquiring data May 26, 2021, and is currently completing commissioning.
The UCoMP demonstrates the technology of a large aperture (50 mm) tunable birefringent filter based on Lithium Niobate crystals and is a pathfinder instrument for the Coronal Solar Magnetism Observatory (COSMO) (Tomczyk et al., 2016) large coronagragh (LC). The LC will observe full Stokes polarimetry (intensity, linear and circular polarization) over a comparable wavelength range but with an aperture of 1.5 meters. COSMO consists of the LC, a chromospheric magnetometer (ChroMag) and the white light K-coronagraph (K-Cor). For more information on COSMO science and capabilities please see: Tomczyk et al. 2016.
|Field-of_View [Rsun]||1.05 to 1.3||1.03 to 1.95 (see figure 3)|
|Spectral Range [nm]||1074 to 1083||530 to 1083|
|Spatial Resolution [arcsec]||9 (4.5 arcsec/pixel)||6 (3 arcsec/pixel)|
Internally occulted refractive coronagraph
Aperture: 20 cm uncoated singlet objective lens
Field-of-view (FOV): 1.03 to 1.56/1.95 Rsun (see Figure 3)
Spatial resolution: 6 arcsec (3 arcsec / pixel)
Spectral Lines observed: Shown in Table 2 and Figure 5.
Spectral Resolution: Set by the birefringence of the Lithium Niobate crystals in the birefringent filter (see Figure 4)
|SPECTRAL LINE||WAVELENGTH [nm]||logTeff|
|FeXIV [corona]||530.3||6.15 to 6.49|
|FeX [corona]||637.4||5.80 to 6.24|
|ArXI [corona]||691.8||6.04 to 6.52|
|FeXV [corona]||706.2||6.20 to 6.63|
|FeXi [corona]||789.4||5.92 to 6.30|
|FeXIII [corona]||1074.7||6.08 to 6.41|
|FeXIII [corona]||1079.8||6.08 to 6.41|
|HI [chromosphere]||656.3||4.01 to 4.29|
|HeI [chromosphere]||1083||4.01 to 4.57|
Examples of some UCoMP Level 1 and Level 2 data products are shown in Figure 6 for a single spectral line (FeXIII 1074 nm). These products are created for each spectral line observed. The image below shows Stokes I (Intensity), Stokes Q/I and U/I that correspond to the percent linear polarization horizontally and at 45 degrees, respectively, and the ratio of L/I where L is the linear polarization = sqrt (Q2 + U2). The rotation of the corona is visible as the blue to red variation in the line-of-sight (LOS) Doppler velocity. The line width includes the instrumental profile. The Azimuth of the magnetic field is measured CCW from horizontal and is subject to a 180-degree ambiguity. The Radial Azimuth of the magnetic field is the azimuth measured CCW from the local radial direction. Zero-degree Radial Azimuth corresponds to magnetic field pointing in the radial direction.