Presentation #123.02 in the session Investigating the Solar Chromosphere at Millimeter Wavelenghts — Poster Session.
The millimeter continuum is a powerful solar diagnostic, providing a direct measurement of chromospheric temperature where many other spectral diagnostics are complicated by non-LTE radiative transfer effects. Previous observations of the solar chromosphere in the 3 mm and 1.25 mm continua by the Atacama Large Millimeter Array (ALMA) have revealed extended regions of cool brightness temperatures, termed “Chromospheric ALMA Holes” (ChAH’s). These features have been speculated to arise from cool clouds of gas in the chromosphere, like those inferred from observations of the infrared spectrum of carbon monoxide (CO). To study the occurrence rates of these ChAH’s in different regions of the chromosphere, we present mosaicked observations of several regions in the 1.25 (ALMA Band 6) and, for the first time, 0.9 (Band 7) mm continuum. Additionally, we compare the brightness temperatures in these bands with observations of the fundamental ro-vibrational band of CO at 4.7 um (taken by the Cryogenic Spectrograph (CYRA) at the Goode Solar Telescope) to determine whether ChAH’s are related to the high-altitude, CO-rich gas implied by historical CO limb observations.