Change of Spectral Properties of Magnetic Field Fluctuations across Different Types of Interplanetary Shocks

Abstract

The interaction between interplanetary (IP) shocks and the solar wind has been studied in the past for the understanding of energy dissipation mechanisms within collisionless plasmas. Compared to the study of fast shocks, other types of IP shocks, including slow mode shocks (i.e., fast forward, fast reverse, slow forward, and slow reverse shocks) remained largely unnoticed. We analyze magnetic field fluctuations observed by the Wind spacecraft from 1995 to 2021 upstream and downstream of the IP shocks using a continuous wavelet transform. The evolution of spectral indices in the ion inertial and transition ranges and the changes in distributions of characteristic ion length scales with respect to the spectral break and proton beta are presented. We found that spectral indices in both inertial and transition ranges and the characteristic length scale distributions are statistically conserved across three types of IP shocks, suggesting that mechanisms associated with the energy dissipation are unaffected by the shocks. The results obtained for the transition range of fast reverse shocks show a larger difference between upstream and downstream plasmas and this will be further studied.

Properties of an Interplanetary Shock Observed at 0.07 and 0.7 au by Parker Solar Probe and Solar Orbiter

“…However, because the downstream flow speed is much larger than the upstream, and the shock changes the plasma parameters abruptly, the level of fluctuations may be overestimated. While the increase in the level of the frequency spectrum has been documented in previous literature (Zhao et al 2021;Park et al 2023), it remains to be understood whether IP shocks inject new turbulence or they simply modify the background plasma properties. However, preliminary analysis shows that the spectral break happens around the ion skin depth d i , compatible with statistical work carried out by Park et al (2023).…”

“…While the increase in the level of the frequency spectrum has been documented in previous literature (Zhao et al 2021;Park et al 2023), it remains to be understood whether IP shocks inject new turbulence or they simply modify the background plasma properties. However, preliminary analysis shows that the spectral break happens around the ion skin depth d i , compatible with statistical work carried out by Park et al (2023). Further studies on the matter, relevant also for understanding the behavior of turbulence at very low heliocentric distances (Zank et al 2020), are further complicated by the geometrical constraints imposed by the singlespacecraft nature of the observations.…”

Modeling Ion Acceleration and Transport in Corotating Interaction Regions: The Mass-to-charge Ratio Dependence of the Particle Spectrum

“…Clearly, κ ⊥ has a weaker A/Q dependence than κ ∥ . A recent statistical study by Park et al (2023) found that β ranges from −1.4 to −2.0, both downstream and upstream of the fast forward and fast reverse interplanetary shock, with a mean value around −1.7. In this work, we assume β to be −5/3 when considering the transport of energetic ions in the solar wind, away from the reverse shock.…”

“…A case study of the large 2003 October 29 event (Li et al 2005a) showed an enhancement of more than a factor of 10. Recent work by Park et al (2023) suggested that the turbulence level across fast shocks can increase, on average, by 3-5 times. From the rarefaction region, the spectral index β does not differ much from the Kolmogorov value.…”

Turbulent Heating of Solar Wind Plasma Downstream of Magnetohydrodynamic Shocks

“…Recently, a number of studies focused on the interaction of turbulent fluctuations and MHD shocks from both theoretical and observational perspectives (Adhikari et al 2016;Pitňa et al 2017Pitňa et al , 2021Borovsky 2020;Zank et al 2021;Trotta et al 2022a;Park et al 2023). In particular, Zank et al (2021, hereafter Zank21) introduced a theoretical framework for the transmission of magnetic field fluctuations across highly perpendicular shocks with high upstream plasma beta values (β > 1).…”