Anisotropy of Density Fluctuations in the Solar Wind at 1 au

Wang, Jiaming; Chhiber, Rohit; Roy, Sohom; Cuesta, Manuel E.; Pecora, Francesco; Yang, Yan; Fu, Xiangrong; Li, Hui; Matthaeus, William H.

doi:10.3847/1538-4357/ad3e7a

Cited by 3 publications

(1 citation statement)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While they found significant structures in both the X GSE and Y GSE directions, their spatial reconstructions revealed solar wind parcels elongated along the Y GSE direction up to a scale size of the order of the spacecraft separation. In a very recent investigation using 10 yr of in situ data from the ACE mission, Wang et al (2024) found that the density correlation scale in directions quasi-parallel to the mean magnetic field is slightly larger than the one in quasiperpendicular directions. This translates to slightly larger dimensions along the direction perpendicular to the Sun-Earth line at 1 au given the average orientation of the IMF.…”

Section: Discussionmentioning

confidence: 99%

Azimuthal Size Scales of Solar Wind Periodic Density Structures

Di Matteo,

Katsavrias,

Kepko

et al. 2024

ApJ

View full text Add to dashboard Cite

Periodic density structures (PDSs) are quasiperiodic variations of solar wind density ranging from a few minutes to a few hours. PDSs advect with the solar wind and have radial length scales (L x ) of tens to several thousand megameters, thus belonging to the class of “mesoscale structures.” Current interplanetary multispacecraft observations are not at spatial separations capable of directly measuring the 3D size scale of PDSs or other mesoscale structures. Instead, previous investigations estimated characteristic spatial scales in solar wind parameters using cross-correlation and/or coherence analysis applied to multispacecraft observations. For the solar wind density and interplanetary magnetic field (IMF) intensity, the reported size scales perpendicular to the Sun–Earth line (L y ) ranged between ≈30 and ≈200 Earth Radii (R E). Here, we implemented a similar approach for the same parameters, but focused on high-density, slow-solar-wind intervals with PDSs observed by the Wind and ARTEMIS-P1 spacecraft. Additionally, this is the first statistical study of the IMF intensity periodicities in relation to PDSs. We identified intervals in which the two spacecraft observed the same periodicity, obtaining two PDS groups based on their radial length scale: L x1 ≈ 86R E and L x2 ≈ 35R E. Then, we classified the events based on the periodic variations’ coherence level. Reproducing the results with simulations of the PDSs’ transit, we inferred the L y order of magnitudes for the two PDS groups: L y1 ≈ 340R E and L y2 ≈ 187R E. Knowing the PDSs’ size scales is fundamental for constraining models aimed at reproducing these structures and is critical for better understanding the PDS–magnetosphere coupling.

show abstract

Section: Discussionmentioning

confidence: 99%

Azimuthal Size Scales of Solar Wind Periodic Density Structures

Di Matteo,

Katsavrias,

Kepko

et al. 2024

ApJ

View full text Add to dashboard Cite

show abstract

Magnetohydrodynamic Turbulence Simulations as a Testing Ground for PUNCH

Pecora,

Yang,

Gibson

et al. 2024

Sol Phys

View full text Add to dashboard Cite

The Polarimeter to UNify the Corona and Heliosphere (PUNCH) will image macroscopic features of the inner heliosphere and also admit sufficiently high spatial resolution to probe scales of turbulence within the upper end of the inertial range, close to the integral scale. As PUNCH is an imager, its measurements will relate differently to the underlying turbulent environment of the outer corona and inner heliosphere from more familiar in situ samples. We present a numerical study that combines magnetohydrodynamic simulations of turbulence together with FORWARD-modeling synthesis of white-light data via the FORWARD code. We show that (i) the “usual” turbulence scalings are modified by the integration along the LOS in an optically thin medium, and (ii) those scalings are still linked to the original properties of the turbulent field. This study is a first step in the process of analyzing and understanding the unprecedented information that PUNCH will provide.

show abstract

Plasma Motions and Compressive Wave Energetics in the Solar Corona and Solar Wind from Radio Wave Scattering Observations

Azzollini,

Emslie,

Clarkson

et al. 2024

ApJ

View full text Add to dashboard Cite

Radio signals propagating via the solar corona and solar wind are significantly affected by compressive waves, impacting the properties of solar bursts as well as sources viewed through the turbulent solar atmosphere. While static fluctuations scatter radio waves elastically, moving, turbulent, or oscillating density irregularities act to broaden the frequency of the scattered waves. Using a new anisotropic density fluctuation model from the kinetic scattering theory for solar radio bursts, we deduce the plasma velocities required to explain observations of spacecraft signal frequency broadening. The inferred velocities are consistent with motions that are dominated by the solar wind at distances ≳10 R ⊙, but the levels of frequency broadening for ≲10 R ⊙ require additional radial speeds ∼(100–300) km s−1 and/or transverse speeds ∼(20–70) km s−1. The inferred radial velocities also appear consistent with the sound or proton thermal speeds, while the speeds perpendicular to the radial direction are consistent with nonthermal motions measured via coronal Doppler-line broadening, interpreted as Alfvénic fluctuations. Landau damping of parallel propagating ion-sound (slow MHD) waves allows an estimate of the proton heating rate. The energy deposition rates due to ion-sound wave damping peak at a heliocentric distance of ∼(1–3) R ⊙ are comparable to the rates available from a turbulent cascade of Alfvénic waves at large scales, suggesting a coherent picture of energy transfer, via the cascade or/and parametric decay of Alfvén waves to the small scales where heating takes place.

show abstract

Anisotropy of Density Fluctuations in the Solar Wind at 1 au

Cited by 3 publications

References 69 publications

Azimuthal Size Scales of Solar Wind Periodic Density Structures

Azimuthal Size Scales of Solar Wind Periodic Density Structures

Magnetohydrodynamic Turbulence Simulations as a Testing Ground for PUNCH

Plasma Motions and Compressive Wave Energetics in the Solar Corona and Solar Wind from Radio Wave Scattering Observations

Contact Info

Product

Resources

About