Azimuthal-drift streaming instabilities in accreting protoplanetary disks

The streaming instability (SI) is one of the key mechanism to form km-sized planetesimals from dust grains or pebbles, which is a critical step in the standard core accretion scenario of planet formation. By enhancing the local dust-to-gas ratio to the point of gravitational collapse, the SI can overcome the collisional and radial drift barriers to grain growth. Recent study finds that there is a new form of SI driven by the azimuthal velocity difference between dust and gas, which results from the gas undergoing accretion due to magnetic torques. This azimuthal-drift SI (AdSI) can remain effective even without a radial pressure gradient, unlike the classical SI. In this work, we extend previous simulations of the AdSI by carrying out a large parameter survey, varying the initial dust-to-gas ratios, magnetic stresses,, and grain sizes by using axisymmetric, unstratified shearing box simulations. We constrain the initial dust-to-gas ratios and magnetic stresses required to make the AdSI efficient. Our study shed light on whether or not the AdSI can induce strong clumping or trigger the classical SI, which can then facilitate planetesimal formations.