arXiv subjects

Maia Brodiano

Publications and source records attributed to Maia Brodiano.

4 recordsLinked to original sources

arXiv2026

Study of the 1/f spectrum using virtual spacecraft sampling in MHD turbulence

We investigate the appearance of a low-frequency 1/f magnetic spectrum in three-dimensional incompressible magnetohydrodynamic turbulence using direct numerical simulations and virtual spacecraft sampling. Our goal is to determine how the measured temporal spectra depend on the mean magnetic guide field, the probe velocity relative to the Alfvén speed, and the sampling angle with respect to the guide field. We find that the clearest 1/f ranges are obtained for stronger guide fields and are favored by faster sampler trajectories oriented more nearly perpendicular to the mean magnetic field. To characterize this behavior, we introduce a quantitative score that measures the quality and spectral coverage of the detected 1/f interval. We further show that, as the probe speed increases, the measured temporal spectra become progressively more consistent with a direct mapping between spatial and temporal fluctuations, particularly for nearly perpendicular sampling in the strong guide field case. These results indicate that the presence and clarity of a temporal 1/f range depend not only on the underlying turbulent dynamics, but also on the geometry and speed of the sampling process, with implications for the interpretation of low-frequency in situ measurements in the solar wind.

astro-ph.SR↗

arXiv2025

An Intermittent Model for the $1/f$ Spectrum in the Pristine Solar Wind

We present a statistical, observational study of the $1/f$ range of solar wind turbulence, where $f$ denotes frequency, using in situ data from the Parker Solar Probe (PSP). We compute the energy cascade rate using the third order law of incompressible magnetohydrodynamic (MHD) turbulence, incorporating expansion terms to account for solar wind dynamics. Our results reveal a $1/τ$ dependence of the energy cascade rate, where $τ$ is the temporal lag, within the $1/f$ range, in contrast to the constant cascade rate in the inertial range. To explain this behavior, we propose a new intermittent model predicting a $1/\ell$ scaling of the cascade rate, where $\ell$ represents the spatial lag. The analysis of the probability density function (PDF) of magnetic field increments confirms the intermittent nature of the parallel fluctuation component, whereas the perpendicular fluctuations are found to be quasi Gaussian. These findings provide new insights into energy transfer processes in the $1/f$ range of solar wind turbulence, with potential applications in planetary magnetosheaths.

astro-ph.SR↗

arXiv2023

A Statistical Study of the Compressible Energy Cascade Rate in Solar Wind Turbulence: Parker Solar Probe Observations

We investigated incompressible and compressible magnetohydrodynamic (MHD) energy cascade rates in the solar wind at different heliocentric distances. We used in situ magnetic field and plasma observations provided by the Parker Solar Probe (PSP) mission and exact relations in fully developed turbulence. To estimate the compressible cascade rate, we applied two recent exact relations for compressible isothermal and polytropic MHD turbulence, respectively. Our observational results show a clear increase of the absolute value of the compressible and incompressible cascade rates as we get closer to the Sun. Moreover, we obtained an increase in both isothermal and polytropic cascade rates with respect to the incompressible case as compressibility increases in the plasma. Further discussion about the relation between the compressibility and the heliocentric distance is carried out. Furthermore, we compared both exact relations as compressibility increases in the solar wind and although we note a slightly trend to observe larger cascades using a polytropic closure, we obtained essentially the same cascade rate in the range of compressibility observed. Finally, we investigated the signed incompressible and compressible energy cascade rates and its connection with the real cascade rate.

astro-ph.SR↗

arXiv2021

Spatio temporal analysis of waves in compressively driven magnetohydrodynamics turbulence

Using direct numerical simulations (DNSs), the interaction between linear waves and turbulence under the compressible magnetohydrodynamic (CMHD) approach was studied. A set of DNSs in three dimensions for a spatial resolution of $128^3$ and $256^3$ were performed. A parametric study was carried out varying the sonic Mach number, the mean magnetic field and the compressibility amplitude of the forcing. Spatio-temporal spectra of the magnetic energy were built and analyzed, allowing for direct identification of all wave modes in a CMHD turbulent system and quantification of the amount of energy in each mode as a function of the wave number. Thus, linear waves were detected, that is Alfvén waves and fast and slow magnetosonic waves. Furthermore, different responses of the plasma were found according to whether the Mach number or the mean magnetic field was varied. On the other hand, making use of spatio-temporal spectra and two different integration methods, we accurately quantified the amount of energy present in each of the normal modes. Finally, although the presence of linear waves was observed, in all the cases studied the system was mainly dominated by the non-linear dynamics of the plasma.

physics.plasm-ph↗