Probing Neutrino Production in Blazars by Millimeter VLBI

The advancement of neutrino observatories has sparked a surge in multi-messenger astronomy. Multiple associations among blazars are reported while production sites located within their central (sub)parsecs. Yet, many questions remain on the nature those processes. next generation Event Horizon Telescope (ngEHT) is uniquely positioned for these studies, as its high frequency and resolution can probe both accretion disk region parsec-scale jet. This opens up new opportunities connecting two regions unraveling proton acceleration blazars. We outline observational strategies ngEHT highlight what it contribute to study