K-Coronagraph (K-Cor)

Instrument

The K-coronagraph (K-Cor) is specifically designed to study the formation and dynamics of coronal mass ejections and the evolution of the density structure of the low corona. The K-Cor records the polarization brightness (pB) formed by Thomson scattering of photospheric light by coronal free electrons.

The National Center for Atmospheric Research (NCAR), via the National Science Foundation (NSF), provided full funding for the COSMO K-Cor, which was deployed to the Mauna Loa Solar Observatory (MLSO) in Hawaii in September 2013, replacing the aging MLSO Mk4 K-coronameter. Here it is shown installed on the MLSO spar.

Coronal Mass Ejections

CMEs are large eruptions of plasma from the Sun that can cause major space weather events such as radiation storms in space and geomagnetic storms at the Earth. They are observed by the K-Cor coronagraph on the ground well before space-based coronagraphs because K-cor can observe down to almost the surface of the Sun (1.15 solar radii) whereas the space-based coronagraphs can only observe CMEs once they appear behind their large occulting disks (approximately 3 solar radii). K-cor can thus measure the acceleration of CMEs in the critical region where the kinetic and gravitational potential energy content and expansion rate of CMEs change in the region where the Lorentz force dominates the dynamics. The solar magnetic eruptions that are the root cause of CMEs are visible in Extreme Ultraviolet (EUV) imaging instruments such as the Atmospheric Imaging Assembly (AIA) on the NASA Solar Dynamics Observatory (SDO) and the Solar Ultraviolet Imaging (SUVI) telescopes on the NOAA GOES weather satellites. Combined with the critical low-coronal imaging of K-Cor and its very low 2.5-minute data latency, these instruments can be used by space weather forecasters to issue warnings and alerts of impending radiation storms, geomagnetic storms, and other impacts of the Sun on manned space flight mission and critical infrastructure systems here on Earth.