Search

In space plasmas, the energy transfer across different scales can be recast in the general picture of Langevin processes, whose dynamical variables are represented, in this case, by magnetic/velocity field fluctuations. It has been shown that this picture is consistent with observations at both inertial and sub-ion scales, thus making stochastic thermodynamics a suitable framework for the investigation of solar wind turbulent fluctuations. The thermodynamics of Langevin equation, which aims to extend the traditional concepts of thermodynamics to mesoscopic scales (i.e., the range of scales where details of the single particle motion is coarse grained), leads to a definition of entropy production associated with single stochastic realizations of the cascading process. We show that fluctuations associated with entropy consumption exhibit distinct statistical properties with respect to the entropy producing counterpart, emphasizing the different thermodynamic effects ascribable to the occurrence of small-scale intermittency. Starting from the evolution equation of the structure functions of magnetic field increments, we derive a simple scaling relation in the non-diffusive limit of the Langevin equation and we establish a link between the drift term and the scaling exponent of sub-ion scale fluctuations. Results are tested on different data samples showing consistent results between observations and simulations, thus giving credits to the newly introduced framework for the statistical properties of solar wind at sub-ion scales., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The topside ionosphere embraces the region extending from the F2-layer electron density peak to the overlying plasmasphere. In this work, we aim at characterizing the effective plasma scale height (H0) above the F2-layer peak using in-situ electron density (Ne) observations by Langmuir Probes (LPs) on the China Seismo-Electromagnetic Satellite (CSES-01). The International Reference Ionosphere (IRI) model and COSMIC-1 radio occultation measurements provide additional information. CSES-01 is a sun-synchronous satellite with an orbital inclination of 97.4° and an altitude of ~500 km, with descending and ascending nodes at ~14:00 local time (LT) and ~02:00 LT, respectively. Calibrated CSES-01 LPs Ne data from 2019-2021 provide information in the topside ionosphere, whereas IRI provides the Ne values at the F2-layer peak (NmF2) for the same time, latitude, and longitude sounded by CSES-01; COSMIC-1 data are instead used to infer the vertical gradient of the effective plasma scale height in the topside ionosphere. The two Ne set of values are used as anchor points to infer H0 by assuming a linear scale height in the topside representation given by the NeQuick model. By exploiting the CSES-01 dataset for the years 2019-2021 we deduced the global behavior of H0 for daytime (~14:00 LT) and nighttime (~02:00 LT) conditions, different seasons, and for low solar activity conditions. Results from CSES-01 observations are compared and validated with those from COSMIC-1 radio occultation and Swarm B satellite measurements, for similar diurnal, seasonal, and solar activity conditions., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

Current understanding of the kinetic-scale turbulence in weakly-collisional plasmas still remains elusive. We employ a general framework in which the turbulent energy transfer is envisioned as a scale-to-scale Langevin process. Fluctuations in the sub-ion range show a global scale invariance, thus suggesting a homogeneous energy repartition. In this Letter, we interpret such a feature by linking the drift term of the Langevin equation to scaling properties of fluctuations. Theoretical expectations are verified on solar wind observations and numerical simulations thus giving relevance to the proposed framework for understanding kinetic-scale turbulence in space plasmas., Comment: Accepted for publication in Physical Review Research

International audience; Using a dynamical systems approach, we examine the persistence and predictability of geomagnetic perturbations across a range of different latitudes and levels of geomagnetic activity. We look at the horizontal components of the magnetic field measured on the ground between 13 and 24 March 2015, at approximately 40 observatories in the Northern Hemisphere. We introduced two dynamical indicators: the extremal index θ, which quantifies the persistence of the system in a particular state and the instantaneous dimension d, which measures the active number of degrees of freedom of the system. The analysis revealed that during disturbed periods, the instantaneous dimension of the horizontal strength of the magnetic field, which depends on latitude, increases, indicating that the geomagnetic response is externally driven. Furthermore, during quiet times, the instantaneous dimension values fluctuate around the state-space dimension, indicating a more stochastic and thus less predictable nature system.

Interplanetary coronal mass ejections (ICMEs) are large-scale solar wind disturbances propagating from the Sun and causing a depression of the galactic-cosmic ray (GCR) intensity known as Forbush decrease (FD). IC- MEs generally contain coherent plasma structures called magnetic clouds (MCs). A unique and powerful data analysis tool allowing for the study of the quasi-3-D configuration of a MC is the Grad-Shafranov (GS) recons - truction. The aim of this work is to investigate the role played by the MC configuration in the formation of a FD. A suited full-orbit test-particle simulation has been developed in order to evaluate FD amplitude and time pro- file produced by the MC obtained with the GS reconstruction. Particle trajectories are computed starting from an isotropic flux outside the MC region. In addition, particle diffusion has been modeled by superimposing a small-angle scattering over the unperturbed charged particle motion at each time step. The model allows us to investigate the MC effect on GCR propagation and to study the energy dependence of the physical processes in - volved, as it provides an estimate of ground-based GCR counts observations at different latitudes. A comparison between model results and both space-based cosmic-ray measurements in L1 and ground-based observations suggests a major role of drifts in producing the FD and a reduced contribution of GCR particle diffusion.

We investigate the role of sub-proton dynamics in inducing large-scale transitions in the solar wind magnetic eld by means of dynamical systems metrics based on instantaneous fractal dimensions. By looking at the corresponding multiscale features, we observe a break in the average attractor dimension occurring at the crossover between the inertial and the sub-proton regime. Our analysis suggests that large-scale transitions are induced by sub-proton dynamics through an inverse cascade mechanism driven by local correlations, while electron contributions (if any) are hidden by instrumental noise.

Ground-based indices, such as the Dst, ap, and AE, have been used for decades to describe the interplay of the terrestrial magnetosphere with the solar wind and provide quantifiable indications of the state of geomagnetic activity in general. These indices have been traditionally derived from ground-based observations from magnetometer stations all around the Earth. In the last 7 years though, the highly successful satellite mission Swarm has provided the scientific community with an abundance of high quality magnetic measurements at Low Earth Orbit, which can be used to produce the space-based counterparts of these indices, such the Swarm-Dst, Swarm-ap, and Swarm-AE indices. In this work, we present the first results from this endeavor, with comparisons against traditionally used parameters. We postulate on the possible usefulness of these Swarm-based products for a more accurate monitoring of the dynamics of the magnetosphere and thus, for providing a better diagnosis of space weather conditions. Plain Language Summary Ground-based geomagnetic activity indices have been used for decades to monitor the dynamics of the Earth's magnetosphere, and provide information on two major types of space weather phenomena, that is, magnetic storm and magnetospheric substorm occurrence and intensity. This study demonstrates how magnetic field data from a Low Earth Orbit satellite mission, like ESA's Swarm constellation, can be used to derive corresponding space-based geomagnetic activity indices. Swarm is unraveling one of the most mysterious aspects of our planet: the magnetic field. The magnetic field and electric currents in and around our planet generate complex forces that have immeasurable impact on everyday life. The comparison of Swarm-based with ground-based indices shows a very good agreement, indicating that Swarm magnetic field data can be used to provide new satellite-based global indices to monitor the level of geomagnetic activity. Given the fact that the official ground-based index for the substorm activity is constructed by data from 12 ground stations solely in the northern hemisphere, it can be said that this index is predominantly northern, while the Swarm-derived substorm activity index may be more representative of a global state, since it is based on measurements from both hemispheres.

In this work, we present a case study of the relevant timescales responsible for coupling between the changes of the solar wind and interplanetary magnetic field (IMF) conditions and the magnetospheric dynamics during the St. Patrick's Day Geomagnetic Storms in 2013 and 2015. We investigate the behavior of the interplanetary magnetic field (IMF) component Bz, the Perreault-Akasofu coupling function and the AE, AL, AU, SYM-H, and ASY-H geomagnetic indices at different timescales by using the empirical mode decomposition (EMD) method and the delayed mutual information (DMI). The EMD, indeed, allows to extract the intrinsic oscillations (modes) present into the different data sets, while the DMI, which provides a measure of the total amount of the linear and nonlinear shared information (correlation degree), allows to investigate the relevance of the different timescales in the solar wind-magnetosphere coupling. The results clearly indicate the existence of a relevant timescale separation in the solar wind-magnetosphere coupling. Indeed, while fluctuations at long timescales (τ > 200 min) show a large degree of correlation between solar wind parameters and magnetospheric dynamics proxies, at short timescales (τ < 200 min) this direct link is missing. This result suggests that fluctuations at timescales lower than 200 min, although triggered by changes of the interplanetary conditions, are mainly dominated by internal processes and are not directly driven by solar wind/IMF. Conversely, the magnetospheric dynamics in response to the solar wind/IMF driver at timescales longer than 200 min resembles the changes observed in the solar wind/IMF features. Finally, these results can be useful for Space Weather forecasting.

Advanced Astronomy for Heliophysics Plus (ADAHELI+) is a project concept for a small solar and space weather mission with a budget compatible with an European Space Agency (ESA) S-class mission, including launch, and a fast development cycle. ADAHELI+ was submitted to the European Space Agency by a European-wide consortium of solar physics research institutes in response to the "Call for a small mission opportunity for a launch in 2017," of March 9, 2012. The ADAHELI+ project builds on the heritage of the former ADAHELI mission, which had successfully completed its phase-A study under the Italian Space Agency 2007 Small Mission Programme, thus proving the soundness and feasibility of its innovative low-budget design. ADAHELI+ is a solar space mission with two main instruments: ISODY+: an imager, based on Fabry-Perot interferometers, whose design is optimized to the acquisition of highest cadence, long-duration, multiline spectropolarimetric images in the visible/near-infrared region of the solar spectrum. XSPO: an x-ray polarimeter for solar flares in x-rays with energies in the 15 to 35 keV range. ADAHELI+ is capable of performing observations that cannot be addressed by other currently planned solar space missions, due to their limited telemetry, or by ground-based facilities, due to the problematic effect of the terrestrial atmosphere. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

BepiColombo Mio (previously called MMO: Mercury Magnetospheric Orbiter) was successfully launched by Ariane 5 from Kourou, French Guiana on October 20, 2018. The Mercury Plasma/Particle Experiment (MPPE) is a comprehensive instrument package onboard Mio spacecraft used for plasma, high-energy particle and energetic neutral atom measurements. It consists of seven sensors including two Mercury Electron Analyzers (MEA1 and MEA2), Mercury Ion Analyzer (MIA), Mass Spectrum Analyzer (MSA), High Energy Particle instrument for electron (HEP-ele), High Energy Particle instrument for ion (HEP-ion), and Energetic Neutrals Analyzer (ENA). Significant efforts were made pre-flight to calibrate all of the MPPE sensors at the appropriate facilities on the ground. High voltage commissioning of MPPE analyzers was successfully performed between June and August 2019 and in February 2020 following the completion of the low voltage commissioning in November 2018. Although all of the MPPE analyzers are now ready to begin observation, the full service performance has been delayed until Mio’s arrival at Mercury. Most of the fields of view (FOVs) of the MPPE analyzers are blocked by the thermal shield surrounding the Mio spacecraft during the cruising phase. Together with other instruments on Mio including Magnetic Field Investigation (MGF) and Plasma Wave Investigation (PWI) that measure plasma field parameters, MPPE will contribute to the comprehensive understanding of the plasma environment around Mercury when BepiColombo/Mio begins observation after arriving at the planet Mercury in December 2025.