The Coronal Solar Magnetism Observatory

Magnetism is the dominant force in the solar corona. It plays a key role in structuring the corona on all spatial scales, in heating the corona, and accelerating the solar wind. The storage and release of magnetic free energy in the corona powers solar eruptions that are responsible for space weather with serious consequences for our technological society. Daily synoptic measurements of the magnetic structure of the global solar corona are needed to advance our understanding of these critical physical processes and to enable a predictive capability of solar eruptive events. The lack of synoptic measurements of global coronal magnetism is due to a technology gap in our current capabilities. One pathway to bridge this gap is to observe the Zeeman and saturated Hanle effects of forbidden emission lines in the visible and IR portions of the coronal spectrum with a ground-based coronagraph. The IR has the advantage that the Zeeman splitting scales as the wavelength squared. A dedicated, high-throughput coronagraph/imaging spectro-polarimeter that combines a large aperture with a large field of view is needed to observe the weak circular polarization signals and monitor the evolution of coronal magnetism over a wide range of spatial and temporal scales. The Coronal Solar Magnetism Observatory (COSMO) 1.5-m aperture Large Coronagraph represents a proposed instrument able to meet this technological challenge, complementing the recently built Daniel K. Inouye Solar Telescope that has a large aperture and high spatial resolution, but is limited in FOV and is not a dedicated coronal facility. Other COSMO instruments include the COSMO K-Coronagraph (K-Cor), currently operating at Mauna Loa, which observes the low corona in broad band light, ideal for tracking CMEs and for providing information on coronal density, and the Chromospheric and prominence Magnetometer (ChroMag), which measures magnetic field and plasma conditions below the corona using polarized light from emission lines of the chromosphere and photosphere. COSMO will provide a unique combination of magnetic field, density, temperature, and velocity observations in the corona and chromosphere that will complement current and future ground- and space-based instruments, and provide a new avenue for understanding the processes that govern the storage and explosive release of magnetic free energy in the corona and enable us to protect our critical infrastructures.