PROBING OORT CLOUD AND LOCAL INTERSTELLAR MEDIUM PROPERTIES VIA DUST PRODUCED IN COMETARY COLLISIONS

The Oort cloud remains one of the most poorly explored regions of the solar system. We propose that its properties can be constrained by studying a population of dust grains produced in collisions of comets in the outer solar system. We explore the dynamics of mu m-sized grains outside the heliosphere (beyond similar to 250 AU), which are predominantly affected by the magnetic field of the interstellar medium (ISM) flow past the Sun. We derive analytic models for the production and motion of small particles as a function of their birth location in the cloud and calculate the particle flux and velocity distribution in the inner solar system. These models are verified by direct numerical simulations. We show that grains originating in the Oort cloud have a unique distribution of arrival directions, which should easily distinguish them from both interplanetary and interstellar dust populations. We also demonstrate that the distribution of particle arrival velocities is uniquely determined by the mass distribution and dust production rate in the cloud. Cometary collisions within the cloud produce a flux of mu m-sized grains in the inner solar system of up to several m(-2) yr(-1). The next generation dust detectors may be sensitive enough to detect and constrain this dust population, which will illuminate the Oort cloud's properties. We also show that the recently detected mysterious population of large (mu m-sized) unbound particles, which seems to arrive with the ISM flow, is unlikely to be generated by collisions of comets in the Oort cloud.