Emanuele Papini

Recent analysis of Parker Solar Probe (PSP) and Solar Orbiter data indicates that fluctuation energy is transferred to the bulk flow in fast streams of the solar wind at heliocentric distances of between 15 and 120 R _⊙ . To gain an insight into this process, we analyzed data collected during the inbound orbit of PSP in Encounter 10, when it is in approximate corotation with the Sun and an accelerating stream is detected between 25 and 45 R _⊙ . The geometry of the flow indicates that a neighboring very fast stream is colliding with the corotating stream, causing large-scale magnetic field distortion, density enhancement, and acceleration. However, also deposition of fluctuations’ energy can heat and do work on the solar wind plasma, resulting in a radial acceleration. We evaluate the energy lost by fluctuations via radial variation of conserved quantities in the corotating stream and find that it is almost equally partitioned into heating and work. While the heating is marginally consistent with the nonadiabatic decrease in proton temperature, the work exerted on the wind is insufficient to account for the measured solar wind acceleration. Although limited to this event, observations suggest that shear interaction is capable of accelerating slower streams within relatively short distances from the Sun, possibly leaving its imprint as large-scale density and magnetic fluctuations.

Turbulence properties in the solar wind change with increasing heliospheric distance. Observations from different missions have shown how spectral indices converge toward an f ^−5/3 spectrum in the inertial range as the solar wind reaches 1 au and how the cascade rate decays as the plasma moves away from the Sun. We evaluate whether these properties display similar trends in a smaller astrophysical system, that of a planetary magnetosheath. Using data from the 2023 Magnetospheric Multiscale (MMS) unbiased magnetosheath campaign, we determine the evolution of the spectral indices and the cascade rate along 15 inbound magnetosheath crossings. WIND observations were permitted to monitor the state of the solar wind during the campaign and allowed to study the impact of the upstream plasma conditions on the evolution of the cascade rate downstream from the bow shock. Our results show an increase of the cascade rate between 2 and 3 orders of magnitude after the plasma crosses the bow shock into the magnetosheath. Once in the magnetosheath, turbulence develops with increasing distance to the bow shock in a way similar to solar wind observations, despite the smaller size of the system. Incompressible Hall magnetohydrodynamics (MHD) scaling-law estimates of the cascade rate show a clear power-law decay of the cascade rate in the magnetosheath, particularly for the cases with upstream slow wind. This suggests that the way energy is injected into the system plays a role in the decay of turbulence as the plasma moves away from the bow shock.

Compressible fluctuations represent a key element of turbulence in astrophysical plasmas, where the compression and expansion of turbulent flows play a critical role in regulating energy transfer and dissipation. In this work, we examine how local streamline topology and energy cascade rate self-organize in plasma turbulence at a fixed scale. Using a fully compressible Hall-magnetohydrodynamic simulation, we quantify the subgrid-scale energy transfer and analyze its relationship to streamline structures by means of gradient-tensor geometric invariants of the velocity field. Our results highlight how streamline topology is crucial for diagnosing turbulence, since the direction of the energy transfer rate is found to be shaped by the local streamline topology. Compressible fluctuations, on the contrary, do not show a clear topological selection in the energy transfer since the overall direction of the local cascade rate is found to be determined by the sign of −∇ · u (plasma volumetric compression or expansion).

The crossover between fluid and ion scales in space plasmas plays a crucial role in the overall energization of the system and it’s where most of the energy exchanges between fields and particles take place. At these scales, turbulent dynamics cascading from larger fluid scales and structures from local ion microphysics typically coexist, leading to still unexplored couplings. Multi-point/multi-scale measurements are then required to fully capture this complex dynamics in situ. 7-point measurements by Plasma Observatory (PMO) in the Earth’s magnetosphere environment offer the opportunity to explore this dynamics and the fluid-ion scale coupling for the first time, in plasma environments with different typical characteristic parameters and dynamical regimes: e.g. solar wind, magnetosheath, magnetotail.In this presentation, we review numerical simulations of plasma turbulence focussing on the transition from fluid to ion scales and its coexistence with ion kinetic processes, in particular micro-instabilities (e.g. mirror, firehose, ion-drift). This include the role played by pressure-strain interactions in controlling the turbulent cascade rate and modulating energy exchanges in the plasma, and how these aspects could be captured for the first time by a constellation like PMO.We address the interplay between these processes and highlight the different spatial and temporal scales involved. As waves and structures from these processes are typically anisotropic, different characteristic scales can be observed, depending on the direction of the sampling, thus making multi-point measurements essential to fully capture them.

The interplay between turbulence and magnetic reconnection in collisionless plasmas is of great interest in many different space and astrophysical environments. Turbulence generates ion-scale current sheets (CSs) which reconnect, driving a turbulent cascade at sub-ion scales and thus providing a channel for energy dissipation. We present a collection of high-resolution 2D and 3D hybrid (kinetic ions, fluid electrons) simulations of plasma turbulence with different physical parameters to investigate how the macroscopic properties of the turbulent plasma background affect the dynamics and statistics of magnetic reconnection. We focus our analysis on the impact of two key parameters: the energy injection scale (i.e., the turbulence correlation length) and the amplitude of the initial fluctuations with respect to the ambient magnetic field (i.e., the turbulence strength). These two, combined, also determine the nonlinear time associated with the turbulent cascade. We first compare the similarity and differences in the properties and dynamics of the turbulence itself (shape and size of coherent structures in real space, spectral properties of the turbulent fluctuations, energy transfer rate) and then the changes in the properties and dynamics of the CSs undergoing reconnection (CS thickness and aspect ratio, reconnection rate). We discuss how the above properties rescale with respect to the two key parameters in the context of existing theories and models for turbulence and magnetic reconnection and the physical implications of our findings.

The China Seismo-Electromagnetic Satellite (CSES) mission provides in-situ measurements of plasma parameters, electromagnetic fields, and energetic particles in the topside ionosphere, with the primary objective of characterizing ionospheric disturbances associated with seismic activity and solar–terrestrial interactions. In this context, we present CSESpy (Papini et al., 2025), a Python package that offers streamlined access to CSES Level 2 data products and expedites higher-level analysis and visualization across multiple payloads and both CSES-01 and CSES-02 spacecraft. Here, we illustrate the capabilities of CSESpy through a typical use case: the characterization of coseismic ionospheric electromagnetic anomalies associated with the 14 August 2021 Haiti earthquake (Recchiuti et al., 2023). Building on this case study, CSESpy is then used to extend the search for ionospheric electromagnetic anomalies to all geographic locations sampled by CSES, exploiting the full data set. The results demonstrate the potential of CSESpy as a powerful tool for systematic earthquake studies and for the investigation of complex events involving coupled variations across multiple physical observables in the near-Earth electromagnetic environment.References[1] Papini, E., Follega, F. M., Battiston, R., & Piersanti, M.: CSESpy: A unified framework for data analysis of the payloads on board the CSES satellite, Remote Sensing, 17(20), 5070, 2025, doi:10.3390/rs17205070[2] Recchiuti, D., D’Angelo, G., Piersanti, M., Di Ruzza, S., Cicone, A., & Battiston, R.: Detection of electromagnetic anomalies over seismic regions during two strong (Mw > 5) earthquakes, Frontiers in Earth Science, 11, 1152343, 2023, doi:10.3389/feart.2023.1152343.

This study investigates the spectral and dynamic characteristics of turbulent fluctuations in the electric field within equatorial plasma bubbles using data from the Electric Field Detector aboard the China Seismo‐Electromagnetic Satellite‐01. We applied a novel analysis method, developed within the framework of dynamical systems theory, to high‐resolution electric field data, allowing us to resolve spatial scales down to just a few meters. This method evaluates the system's persistence in specific states and the instantaneous dimension of fluctuations. Our findings reveal a significant increase in the instantaneous dimension and a decrease in the extremal index , which measures local persistence, within the plasma bubbles. These results suggest a complex interplay of structures at different scales driven by turbulent dynamics characterizing these ionospheric plasma depletions. This study provides new insights into the turbulent processes within equatorial plasma bubbles, advancing our understanding of their underlying mechanisms.

The China Seismo Electromagnetic Satellite (CSES) mission provides in situ measurements of the electromagnetic field, plasma, and charged particles in the topside ionosphere. Each CSES spacecraft carries several different scientific payloads delivering a wealth of information about the ionospheric plasma dynamics and properties, as well as measurement about energetic particles precipitating in the ionosphere. In this work, we introduce CSESpy, a Python package designed to provide an interface to CSES data products, with the aim of easing the pathway for scientists to carry out analyses of CSES data. Beyond simply being an interface to the data, CSESpy aims to provide higher-level analysis and visualization tools, as well as methods for combining concurrent measurements from different instruments, so as to allow multipayload studies in a unified framework. Moreover, CSESpy is designed to be highly flexible as such, it can be extended to interface with datasets from other sources and can be embedded in wider software ecosystems. We highlight some applications, also demonstrating that CSESpy is a powerful visualization tool for investigating complex events involving variations across multiple physical observables.

We introduce the Whistler Identification by Spectral Power Estimation and Recognition (WhISPER) algorithm, a novel automated technique for detecting whistler waves in the top side of the Earth’s ionosphere. WhISPER is the first step towards a comprehensive system designed to accumulate and analyze a large dataset of whistler observations, which has been developed to advance our understanding of whistler generation and propagation. Unlike conventional image-correlation-based techniques, WhISPER identifies whistlers based on their energy content, enhancing computational efficiency. This work presents the results of applying WhISPER to four years (2019–2022) of top-side ionospheric magnetic field data. A statistical analysis of over 800,000 detected whistlers reveals a strong correlation with lightning activity and (as expected) higher occurrence rates during local summer months. The presented results demonstrate the excellent performance of the WhISPER technique in identifying whistler events.