Evolution of plasma turbulent processes at comet 67P: Rosetta Observations

Abstract:

We characterized plasma turbulent processes at comet 67P/Churyumov-Gerasimenko and discovered that different processes became prominent during different times in the plasma environment of the comet as it orbited the Sun. For this characterization, we analyzed Rosetta’s magnetometer data and interpreted the magnetic field power spectral signatures in terms of plasma turbulent processes. As the comet 67P orbited the Sun, depending on the water outgassing rate, it attained three active phases: weak, intermediate, and strong. During the weakly active phase of the comet, dominant injection and uniform injection were prominent at low frequencies near 10^-2 Hz, while partial energy cascade or dispersion was prominent at high frequencies near 0.5 Hz. During the intermediately active phase, uniform injection was prominent at low frequencies, while partial energy cascade or dispersion was prominent at high frequencies. During the strongly active phase of the comet, we find that partial energy cascade or dissipation was dominant at low frequencies, while partial energy cascade, dissipation, or dispersion was dominant at high frequencies. We infer that the temporal variations of the turbulent processes occurred due to the evolution of the plasma environment of the comet as it orbited the Sun.