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First High Resolution Interferometric Observation of a Solar Prominence With ALMA

We present the first observation of a solar prominence at $84-116$ GHz using the high resolution interferometric imaging of ALMA. Simultaneous observations in H$α$ from Białkaw Observatory and with SDO/AIA reveal similar prominence morphology to the ALMA observation. The contribution functions of 3 mm and H$α$ emission are shown to have significant overlap across a range of gas pressures. We estimate the maximum millimetre-continuum optical thickness to be $τ_\mathrm{3mm}\approx 2$, and the brightness temperature from the observed H$α$ intensity. The brightness temperature measured by ALMA is $\sim 6000-7000$ K in the prominence spine, which correlates well with the estimated brightness temperature for a gas temperature of 8000 K.