Modification of the Power Spectral Density of Magnetic Field Fluctuations by Quasi-perpendicular Interplanetary Shocks

Abstract

We investigate the role of interplanetary (IP) shocks in solar wind turbulence using observations of Solar Orbiter, Parker Solar Probe, and Wind. Employing statistical analysis of quasi-perpendicular fast forward (FF) and fast reverse (FR) shocks, we revisit evolution of magnetic field turbulence across IP shocks. Our previous work indicates that the spectral properties of magnetic fluctuations are statistically conserved across different types of IP shocks, except FR shocks in the transition range of frequencies. We focus on the spectral index in the transition range ( ) using 1 minute sliding windows at 10 s intervals to probe the turbulent dissipation near shocks. We address the influence of key turbulence parameters, particularly cross helicity (σc) and fluctuation amplitude (σB), on . Our results demonstrate (1) an immediate change in across the shock with no evidence for further gradual or asymptotic evolution over extended intervals, and this implies that shock universally serves as a thin boundary separating two turbulence states; (2) the dominant factor forming the steepness of is σc, rather than σB; and (3) the statistically shallower downstream of FR shocks results from a systematic reduction in σc across shocks. These findings suggest that the observed spectral modification is primarily governed by changes in turbulence Alfvénicity, not directly by dissipation processes related to the shock, and can be commonly observed toward extensive heliospheric distances.