arXiv subjects

F. Pecora

Publications and source records attributed to F. Pecora.

6 recordsLinked to original sources

arXiv2026

Assessing VBz variations during CME propagation: a preparatory study for the HENON mission using EUHFORIA

Coronal mass ejections (CMEs) are among the main drivers of space weather hazards. In this context, HENON is a new space mission designed to carry out observations in the solar wind upstream of the Earth, aiming to provide timely alerts for hazardous perturbations propagating towards the Earth. HENON will orbit Earth on a distant retrograde orbit, approximately 0.082 AU upstream of the Earth when it is on the Sun-Earth line. The measurements taken by HENON will allow us to determine plasma and magnetic field parameters with a lead time of several hours with respect to the Lagrangian point L1. We assess the VB_z parameter variations (the product of solar wind speed V and southward magnetic field B_z) along the HENON orbit. Given its role as a primary driver of geomagnetic activity, we analyse how these measurements change with respect to Earth's position to evaluate HENON's forecasting potential. We used the FRi3D CME model of the EUHFORIA simulation code to characterize the initial properties of the CME. FRi3D allows us to set the CME magnetic field as a magnetic flux rope. From the simulation results, we evaluated the VB_z parameter at nine virtual spacecraft positions along the planned HENON orbit. The heliocentric longitudes of the virtual spacecraft range from about -6.9{\deg} to 6.9{\deg}, while the geocentric longitudes vary from -60{\deg} to +60{\deg} in steps of 15{\deg}. The initial direction of propagation of the CME central apex is either along the Sun-Earth line or at heliocentric longitudes of {\pm}30{\deg}. We find that with the proposed orbital parameters, the values of the VBz parameter along the HENON orbit are sufficiently similar to those measured in the vicinity of the Earth to be useful for space weather forecasts. HENON enables reliable VB_z estimates 2-8 hours in advance, improving space weather forecasting and protection of critical infrastructure and satellites.

astro-ph.SR↗

arXiv2024

Correlation of Coronal Mass Ejection Shock Temperature with Solar Energetic Particle Intensity

Solar energetic particle (SEP) events have been observed by the Parker Solar Probe (PSP) spacecraft since its launch in 2018. These events include sources from solar flares and coronal mass ejections (CMEs). Onboard PSP is the IS$\odot$IS instrument suite measuring ions over energies from ~ 20 keV/nucleon to 200 MeV/nucleon and electrons from ~ 20 keV to 6 MeV. Previous studies sought to group CME characteristics based on their plasma conditions and arrived at general descriptions with large statistical errors, leaving open questions on how to properly group CMEs based solely on their plasma conditions. To help resolve these open questions, plasma properties of CMEs have been examined in relation to SEPs. Here we reexamine one plasma property, the solar wind proton temperature, and compare it to the proton SEP intensity in a region immediately downstream of a CME-driven shock for seven CMEs observed at radial distances within 1 au. We find a statistically strong correlation between proton SEP intensity and bulk proton temperature, indicating a clear relationship between SEPs and the conditions in the solar wind. Furthermore, we propose that an indirect coupling of SEP intensity to the level of turbulence and the amount of energy dissipation that results is mainly responsible for the observed correlation between SEP intensity and proton temperature. These results are key to understanding the interaction of SEPs with the bulk solar wind in CME-driven shocks and will improve our ability to model the interplay of shock evolution and particle acceleration.

physics.space-ph↗

arXiv2022

The essential role of multi-point measurements in investigations of turbulence, three-dimensional structure, and dynamics: the solar wind beyond single scale and the Taylor Hypothesis

Space plasmas are three-dimensional dynamic entities. Except under very special circumstances, their structure in space and their behavior in time are not related in any simple way. Therefore, single spacecraft in situ measurements cannot unambiguously unravel the full space-time structure of the heliospheric plasmas of interest in the inner heliosphere, in the Geospace environment, or the outer heliosphere. This shortcoming leaves numerous central questions incompletely answered. Deficiencies remain in at least two important subjects, Space Weather and fundamental plasma turbulence theory, due to a lack of a more complete understanding of the space-time structure of dynamic plasmas. Only with multispacecraft measurements over suitable spans of spatial separation and temporal duration can these ambiguities be resolved. We note that these characterizations apply to turbulence across a wide range of scales, and also equally well to shocks, flux ropes, magnetic clouds, current sheets, stream interactions, etc. In the following, we will describe the basic requirements for resolving space-time structure in general, using turbulence' as both an example and a principal target or study. Several types of missions are suggested to resolve space-time structure throughout the Heliosphere.

physics.space-ph↗

arXiv2021

Parker Solar Probe Observations of Helical Structures as Boundaries for Energetic Particles

Energetic particle transport in the interplanetary medium is known to be affected by magnetic structures. It has been demonstrated for solar energetic particles in near-Earth orbit studies, and also for the more energetic cosmic rays. In this paper, we show observational evidence that intensity variations of solar energetic particles can be correlated with the occurrence of helical magnetic flux tubes and their boundaries. The analysis is carried out using data from Parker Solar Probe orbit 5, in the period 2020 May 24 to June 2. We use FIELDS magnetic field data and energetic particle measurements from the Integrated Science Investigation of the Sun (\isois) suite on the Parker Solar Probe. We identify magnetic flux ropes by employing a real-space evaluation of magnetic helicity, and their potential boundaries using the Partial Variance of Increments method. We find that energetic particles are either confined within or localized outside of helical flux tubes, suggesting that the latter act as transport boundaries for particles, consistent with previously developed viewpoints.

astro-ph.SR↗

arXiv2021

Current sheets, plasmoids and flux ropes in the heliosphere. Part II: Theoretical aspects

Our understanding of processes occurring in the heliosphere historically began with reduced dimensionality - one-dimensional (1D) and two-dimensional (2D) sketches and models, which aimed to illustrate views on large-scale structures in the solar wind. However, any reduced dimensionality vision of the heliosphere limits the possible interpretations of in-situ observations. Accounting for non-planar structures, e.g. current sheets, magnetic islands, flux ropes as well as plasma bubbles, is decisive to shed the light on a variety of phenomena, such as particle acceleration and energy dissipation. In part I of this review, we have described in detail the ubiquitous and multi-scale observations of these magnetic structures in the solar wind and their significance for the acceleration of charged particles. Here, in part II, we elucidate existing theoretical paradigms of the structure of the solar wind and the interplanetary magnetic field, with particular attention to the fine structure and stability of current sheets. Differences in 2D and 3D views of processes associated with current sheets, magnetic islands, and flux ropes are discussed. We finally review the results of numerical simulations and in-situ observations, pointing out the complex nature of magnetic reconnection and particle acceleration in a strongly turbulent environment.

astro-ph.SR↗

arXiv2020

On the Identification of Coherent Structures in Space Plasmas: the Magnetic Helicity-PVI Method

Plasma turbulence can be viewed as a magnetic landscape populated by large and small scale coherent structures. In this complex network, large helical magnetic tubes might be separated by small scale magnetic reconnection events (current sheets). However, the identification of these magnetic structures in a continuous stream of data has always been a challenging task. Here we present a method that is able to characterize both the large and small scale structures of the turbulent solar wind, based on the combined use of a filtered magnetic helicity ($H_m$) and the Partial Variance of Increments (PVI). This simple, single-spacecraft technique, has been validated first via direct numerical simulations of plasma turbulence and then applied to data from the Parker Solar Probe (PSP) mission. This novel analysis, combining $H_m$&PVI methods, reveals that a large number of flux tubes populate the solar wind and continuously merge in contact regions where magnetic reconnection and particle acceleration may occur.

physics.plasm-ph↗