Preemergence Signatures of Horizontal Divergent Flows in Solar Active Regions

Solar active regions (ARs) play a fundamental role in driving many of the geo-effective eruptions which propagate into System. However, we are still unable to consistently predict where and when ARs will occur across solar disk by identifying pre-emergence signatures observables such as Doppler velocity (without using Helioseismic methods). Here aim determine earliest time at signatures, specifically Horizontal Divergent Flow (HDF), can be confidently detected data from Dynamics Observatory's Magnetic Imager (SDO/HMI). Initially, follow previous studies thresholding method, searches for significant increases number pixels that display specific line-of-sight velocity. We expand this method more windows conduct basic parameter study investigating effect cadence on inferred results. Our findings agree with $37.5$% displaying HDF, average lead times between HDF flux emergence $58$ minutes. present new potential signature manifests cadence-independent transient disruptions amplitudes multiple recover 10 16 studied, 60-156 Several effects influence both estimated suggesting one may need combine magnetic field get reliable indicator continued emergence.