arXiv subjects

Marco Pinto

Publications and source records attributed to Marco Pinto.

8 recordsLinked to original sources

arXiv2026

In-flight calibration of RADEM, the JUICE mission radiation monitor

The RADiation-hard Electron Monitor (RADEM) aboard the Jupiter Icy Moons Explorer (JUICE), launched on 14 April 2023, measures high-energy protons and electrons during the cruise phase and will continue throughout the nominal mission. Initial in-flight observations could not be explained by pre-flight ground calibration, motivating an in-flight calibration campaign. We calibrated the RADEM sensors using galactic cosmic rays by progressively increasing detector thresholds, thereby modifying their response to high-energy particles. Threshold-dependent in-flight count rates were compared with theoretical expectations derived from the Badhwar-O'Neill 2020 galactic cosmic ray model and corresponding response functions. These results were used to derive new in-flight calibration coefficients and to develop a flux reconstruction algorithm based on the bow-tie method. In several cases, the in-flight calibration slopes differ by up to an order of magnitude from ground calibration values. Proton fluxes from solar energetic particle events reconstructed with this method agree within a factor of two with independent measurements from the Solar and Heliospheric Observatory. These results demonstrate that RADEM provides accurate proton flux measurements in interplanetary space and is well suited for both single-spacecraft analyses and coordinated multi-mission studies of solar energetic particles. While electrons were clearly detected during the JUICE Lunar-Earth gravity assist, reliable reconstruction of their fluxes requires further analysis.

astro-ph.SR↗

arXiv2026

A study of solar energetic particle transport on 30 March 2022 using multi-spacecraft data assimilation

We analyze a unique solar energetic particle event observed simultaneously by the BepiColombo and STEREO-A spacecraft on March 30, 2022. The two spacecraft at heliocentric distances of 0.6 and 1.0 AU are expected to be aligned approximately along the same magnetic field line, providing a valuable opportunity to investigate particle transport processes in the inner heliosphere. Protons with energies above 1.0 MeV exhibit velocity dispersion during the rise phase, suggesting that the energetic particles are produced close to the Sun, possibly associated with a coronal mass ejection. In contrast, protons during the decay phase are characterized by long-lasting time profiles with longer time scales at 1.0 AU than at 0.6 AU, suggesting that the particles deviate from ballistic propagation. By assimilating these multi-spacecraft observation data into numerical simulations of the focused transport equation, for the first time, we estimate the mean free path parallel to the magnetic field as a time series. The inferred mean free path decreases over time and approaches around 0.5-1.0 AU at the STEREO-A location during the decay phase, suggesting an increasing influence of scattering on particle transport. This interpretation is qualitatively supported by independent STEREO-A observations that showed increasing magnetic field fluctuations, suggesting the connection between the particle transport and the local field fluctuations. However, only a fraction of these fluctuations is expected to contribute to particle scattering, which may be due to the multidimensional nature of magnetic field fluctuations.

astro-ph.SR↗

arXiv2025

Spatio-Temporal Evolution of the March 2022 ICME Revealed by Multi-Point Observations of Forbush Decreases

Interplanetary coronal mass ejections (ICMEs) cause Forbush Decreases (FDs) effects, which are local decreases in background galactic cosmic rays (GCR). Even though FDs can be observed with simple particle instruments, their amplitude and shape provide physical profiles of passing ICMEs. However, in some cases, previous statistical studies of the heliocentric distance dependence of FD changes associated with ICME propagation have found no strong correlation. We need the criteria for evaluating the relationship between ICMEs structure and FD, necessary for FDs statistical analysis. This study investigates the effect of evolutions and interactions of ICMEs on FDs profiles in the inner Solar System, using multipoint comparisons. We focus on multipoint ICME observations by Solar Orbiter, BepiColombo, and near-Earth spacecraft from March 10-16, 2022, when these spacecraft were ideally located for studying the radial and longitudinal evolutions of ICME and accompanying FDs. We compared GCR variations with the multiple in-situ data and ICME model, clarifying the correspondence between the evolution of each ICME structure in radial and azimuthal directions and the depth and gradients of the FD. The radial comparison revealed decreases in FD intensities and gradients associated with the expansion of the ICME. The longitudinal difference found in FD intensity indicates longitudinal variations of the ICMEs shielding effect. These results suggest that accurate multi-point FD comparisons require determining the relationship between the observers position and the inner structure of the passing ICMEs.

astro-ph.SR↗

arXiv2024

Improved modelling of SEP event onset within the WSA-Enlil-SEPMOD framework

Multi-spacecraft observations of solar energetic particle (SEP) events not only enable a deeper understanding and development of particle acceleration and transport theories, but also provide important constraints for model validation efforts. However, because of computational limitations, a given physics-based SEP model is usually best-suited to capture a particular phase of an SEP event, rather than its whole development from onset through decay. For example, magnetohydrodynamic (MHD) models of the heliosphere often incorporate solar transients only at the outer boundary of their so-called coronal domain -- usually set at a heliocentric distance of 20-30 $R_{\odot}$. This means that particle acceleration at CME-driven shocks is also computed from this boundary onwards, leading to simulated SEP event onsets that can be many hours later than observed, since shock waves can form much lower in the solar corona. In this work, we aim to improve the modelled onset of SEP events by inserting a "fixed source" of particle injection at the outer boundary of the coronal domain of the coupled WSA-Enlil 3D MHD model of the heliosphere. The SEP model that we employ for this effort is SEPMOD, a physics-based test-particle code based on a field line tracer and adiabatic invariant conservation. We apply our initial tests and results of SEPMOD's fixed-source option to the 2021 October 9 SEP event, which was detected at five well-separated locations in the inner heliosphere -- Parker Solar Probe, STEREO-A, Solar Orbiter, BepiColombo, and near-Earth spacecraft.

astro-ph.SR↗

arXiv2023

The effect of the ambient solar wind medium on a CME-driven shock and the associated gradual solar energetic particle event

We present simulation results of a gradual solar energetic particle (SEP) event detected on 2021 October 9 by multiple spacecraft, including BepiColombo (Bepi) and near-Earth spacecraft such as the Advanced Composition Explorer (ACE). A peculiarity of this event is that the presence of a high speed stream (HSS) affected the low-energy ion component ($\lesssim 5$ MeV) of the gradual SEP event at both Bepi and ACE, despite the HSS having only a modest solar wind speed increase. Using the EUHFORIA (European Heliospheric FORecasting Information Asset) magnetohydrodynamic model, we replicate the solar wind during the event and the coronal mass ejection (CME) that generated it. We then combine these results with the energetic particle transport model PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration). We find that the structure of the CME-driven shock was affected by the non-uniform solar wind, especially near the HSS, resulting in a shock wavefront with strong variations in its properties such as its compression ratio and obliquity. By scaling the emission of energetic particles from the shock to the solar wind compression at the shock, an excellent match between the PARADISE simulation and in-situ measurements of $\lesssim 5$ MeV ions is obtained. Our modelling shows that the intricate intensity variations observed at both ACE and Bepi were influenced by the non-uniform emission of energetic particles from the deformed shock wave and demonstrates the influence of even modest background solar wind structures on the development of SEP events.

physics.space-ph↗

arXiv2021

Spectral Dependence

This paper presents a general framework for modeling dependence in multivariate time series. Its fundamental approach relies on decomposing each signal in a system into various frequency components and then studying the dependence properties through these oscillatory activities.The unifying theme across the paper is to explore the strength of dependence and possible lead-lag dynamics through filtering. The proposed framework is capable of representing both linear and non-linear dependencies that could occur instantaneously or after some delay(lagged dependence). Examples for studying dependence between oscillations are illustrated through multichannel electroencephalograms. These examples emphasized that some of the most prominent frequency domain measures such as coherence, partial coherence,and dual-frequency coherence can be derived as special cases under this general framework.This paper also introduces related approaches for modeling dependence through phase-amplitude coupling and causality of (one-sided) filtered signals.

stat.ME↗

arXiv2021

Smooth Online Parameter Estimation for time varying VAR models with application to rat's LFP data

Multivariate time series data appear often as realizations of non-stationary processes where the covariance matrix or spectral matrix smoothly evolve over time. Most of the current approaches estimate the time-varying spectral properties only retrospectively - that is, after the entire data has been observed. Retrospective estimation is a major limitation in many adaptive control applications where it is important to estimate these properties and detect changes in the system as they happen in real-time. One major obstacle in online estimation is the computational cost due to the high-dimensionality of the parameters. Existing methods such as the Kalman filter or local least squares are feasible. However, they are not always suitable because they provide noisy estimates and can become prohibitively costly as the dimension of the time series increases. In our brain signal application, it is critical to develop a robust method that can estimate, in real-time, the properties of the underlying stochastic process, in particular, the spectral brain connectivity measures. For these reasons we propose a new smooth online parameter estimation approach (SOPE) that has the ability to control for the smoothness of the estimates with a reasonable computational complexity. Consequently, the models are fit in real-time even for high dimensional time series. We demonstrate that our proposed SOPE approach is as good as the Kalman filter in terms of mean-squared error for small dimensions. However, unlike the Kalman filter, the SOPE has lower computational cost and hence scalable for higher dimensions. Finally, we apply the SOPE method to a rat's local field potential data during a hippocampus-dependent sequence-memory task. As demonstrated in the video, the proposed SOPE method is able to capture the dynamics of the connectivity as the rat performs the sequence of non-spatial working memory tasks.

stat.ME↗

arXiv2018

GUIMesh: a tool to import STEP geometries into Geant4 via GDML

Detailed radiation analysis of instruments flown in space is critical to ensure mission safety, often requiring the use of state-of-the-art particle transport simulation tools. Geant4 is one of the most powerful toolkits to simulate the interaction and the passage of particles through matter. This framework however, is not prepared to receive Standard for The Exchange of Product data (STEP) files, the most versatile Computer-Aided Design (CAD) format, as inputs requiring previous conversion to other formats. This, especially when the instruments have complex shapes, and/or a large number of volumes may lead to loss of detail and under or overestimation of the quantities under study. Though several solutions have been proposed to import complex geometries into Geant4, so far, only commercial options are available. In this paper we present a new tool, GUIMesh, that embeds FreeCAD libraries, an open-source CAD editor, to tessellate volumes, and convert them to Geometry Description Markup Language (GDML), a Geant4 readable format, in a straightforward way. Several degrees of freedom are given to the user regarding the mesh and choice of material. Different geometries were tested for p material definition, geometry and navigation errors, successfully validating the method used.

physics.comp-ph↗