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Schlagwörter:
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Zusammenfassung:
The nature of the turbulent energy cascade around the proton characteristic scales has been intensely investigated in the last decades. At these scales, i.e., the proton inertial length and proton thermal gyroradius, the character of the fluctuations is significantly different with respect to those in the inertial range. For example, intermittency increases, the magnetic field power spectrum steepens, the absolute value of the magnetic helicity gradually increases. Although different explanations for this change of behavior at the proton scales have been suggested (e.g., stochastic heating, proton cyclotron damping, cross-helicity barrier), a full understanding of the dynamical processes that govern the physics of the ion kinetic range is still lacking. In this work, we employ an extensive set of high-cadence measurements of magnetic field from the MFI instrument on board the Wind spacecraft. We estimate the magnetic field power spectra and we analyze them in the framework of the recently-developed technique of Pitna et al. (2021), which corrects for the MFI noise around the Nyquist frequency. We analyze the dependency of the slope below the proton scales on the turbulence power within the inertial range, cross-helicity, and proton plasma beta. We discuss our results with regard to (a) the above-mentioned mechanisms for the origin of the kinetic range, (2) recent observations of the young solar wind by Parker Solar Probe, and (3) tailored 2D hybrid-kinetic simulations of solar wind plasma.
