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Abstract We study anisotropic magnetohydrodynamic (MHD) turbulence in the slow solar wind measured by Parker Solar Probe (PSP) and Solar Orbiter (SolO) during its first orbit from the perspective of variance anisotropy and correlation anisotropy. We use the Belcher & Davis approach (M1) and a new method (M2) that decomposes a fluctuating vector into parallel and perpendicular fluctuating vectors. M1 and M2 calculate the transverse and parallel turbulence components relative to the mean magnetic field direction. The parallel turbulence component is regarded as compressible turbulence, and the transverse turbulence component as incompressible turbulence, which can be either Alfvénic or 2D.more »Free, publiclyaccessible full text available July 1, 2023

Free, publiclyaccessible full text available June 15, 2023

Abstract During its 10th orbit around the Sun, the Parker Solar Probe sampled two intervals where the local Alfvén speed exceeded the solar wind speed, lasting more than 10 hours in total. In this paper, we analyze the turbulence and wave properties during these periods. The turbulence is observed to be Alfvénic and unbalanced, dominated by outwardpropagating modes. The power spectrum of the outwardpropagating Elsässer z + mode steepens at high frequencies while that of the inwardpropagating z − mode flattens. The observed Elsässer spectra can be explained by the nearly incompressible (NI) MHD turbulence model with both 2D andmore »Free, publiclyaccessible full text available August 1, 2023

Abstract The structure of shocks and turbulence are strongly modified during the acceleration of cosmic rays (CRs) at a shock wave. The pressure and the collisionless viscous stress decelerate the incoming thermal gas and thus modify the shock structure. A CR streaming instability ahead of the shock generates the turbulence on which CRs scatter. The turbulent magnetic field in turn determines the CR diffusion coefficient and further affects the CR energy spectrum and pressure distribution. The dissipation of turbulence contributes to heating the thermal gas. Within a multicomponent fluid framework, CRs and thermal gas are treated as fluids and aremore »Free, publiclyaccessible full text available June 1, 2023

Topological surface currents accessed through reversible hydrogenation of the threedimensional bulkFree, publiclyaccessible full text available April 28, 2023

Abstract Zank et al. developed models describing the transport of lowfrequency incompressible and nearly incompressible turbulence in inhomogeneous flows. The formalism was based on expressing the fluctuating variables in terms of the Elsässar variables and then taking “moments” subject to various closure hypotheses. The turbulence transport models are different according to whether the plasma beta regime is large, of order unity, or small. Here, we show explicitly that the three sets of turbulence transport models admit a conservation representation that resembles the wellknown WKB transport equation for Alfvén wave energy density after introducing appropriate definitions of the “pressure” associated withmore »Free, publiclyaccessible full text available April 1, 2023

Abstract We investigate the interaction of turbulence with shock waves by performing 2D hybrid kinetic simulations. We inject forcefree magnetic fields upstream that are unstable to the tearingmode instability. The magnetic fields evolve into turbulence and interact with a shock wave whose sonic Mach number is 2.4. Turbulence properties, the total and normalized residual energy and the normalized cross helicity, change across the shock wave. While the energy of velocity and magnetic fluctuations is mostly distributed equally upstream, the velocity fluctuations are amplified dominantly downstream of the shock wave. The amplitude of turbulence spectra for magnetic, velocity, and density fluctuationsmore »Free, publiclyaccessible full text available February 1, 2023

Free, publiclyaccessible full text available May 1, 2023

Inertialrange Magneticfluctuation Anisotropy Observed from Parker Solar Probe’s First Seven OrbitsSolar wind turbulence is anisotropic with respect to the mean magnetic field. Anisotropy leads to ambiguity when interpreting in situ turbulence observations in the solar wind because an apparent change in the measurements could be due to either the change of intrinsic turbulence properties or to a simple change of the spacecraft sampling direction. We demonstrate the ambiguity using the spectral index and magnetic compressibility in the inertial range observed by the Parker Solar Probe during its first seven orbits ranging from 0.1 to 0.6 au. To unravel the effects of the sampling direction, we assess whether the wavevector anisotropymore »Free, publiclyaccessible full text available January 1, 2023

Abstract The Parker Solar Probe (PSP) entered a region of subAlfvénic solar wind during encounter 8, and we present the first detailed analysis of lowfrequency turbulence properties in this novel region. The magnetic field and flow velocity vectors were highly aligned during this interval. By constructing spectrograms of the normalized magnetic helicity, crosshelicity, and residual energy, we find that PSP observed primarily Alfvénic fluctuations, a consequence of the highly fieldaligned flow that renders quasi2D fluctuations unobservable to PSP. We extend Taylor’s hypothesis to sub and superAlfvénic flows. Spectra for the fluctuating forward and backward Elsässer variables ( z ± ,more »Free, publiclyaccessible full text available February 1, 2023