Alessandro Ippolito

The most intense radio feature in the Solar System are the solar Type‐III radio bursts, which are associated with electron beams that propagate along open magnetic field lines. Although solar radio bursts have been studied since the 1940s, observations remain mainly restricted within 1 AU. In this study, we explore 16.5 years of data (2005–2021) from the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) onboard Mars Express. While not the central aim of the instrument, MARSIS has been recording solar radio bursts since its deployment in mid‐2005. Given the potential of this new radio burst data set for heliophysics studies, we have created a catalog of Type‐III solar radio burst events between 1.38 and 1.66 AU (Mars' orbit) within the frequency range of 0.1 and 5.5 MHz and with an instrument measuring cadence of 7.5 s. We demonstrate that these emissions seen at Mars come from the Sun, follow the solar cycle pattern, and are not influenced by the planet's own properties such as crustal magnetic fields. We also compare the propagation of a few illustrative events from the Sun to Mars to demonstrate the utility of this new data set for heliophysics studies. Mars catalogs provide a fundamentally new perspective on the spatial extent, directivity, and evolution of solar radio emission in the inner heliosphere. It serves as an essential benchmark for multi‐point heliospheric studies and for constraining radio emissions mechanisms beyond Earth orbit, and demonstrating the usefulness of planetary missions in contributing to heliophysics science in diverse ways.

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

Context. During September 2014, intense solar activity led to a number of coronal mass ejections (CMEs) propagating in the heliosphere. The strong perturbation in the interplanetary magnetic field and the remarkable enhancements in the energetic particle fluxes accelerated by the shock waves associated with the CMEs affected the environments of the inner planets of the Solar System. Aims. Taking advantage of a relatively favorable position in terms of angular distance among Mercury, Earth, and Mars, our purpose is to observe the evolution and impact of strong solar events, providing an overview of the impact of the same solar phenomena on different planetary environments, with special interest in the response of Mars’ ionosphere as this may have implications for future exploration of the red planet. Methods. We used observations from a fleet of spacecraft distributed in the inner Solar System, such as STEREO B, MESSENGER, Mars Express, and SOHO, to perform a characterization of the interaction with the planets, investigating some of the main effects of the CMEs on the different planetary environments. Besides, we applied a numerical simulation to reconstruct the magnetic connection from Mercury, Earth, and Mars to the solar corona on the dates on which the CME events occurred. Results. We find that the CMEs events analyzed here induced remarkable effects that affected all the environments of the inner planets of the Solar System. Enhancements in the solar energetic particle fluxes were observed at Mercury, Earth, and Mars, with different characteristics. In addition, a solar radio burst was observed both at Earth and Mars, together with strong disturbances in the geomagnetic field, and diffuse echoes and radio black outs in the Martian ionosphere. Conclusions. The proposed multi-spacecraft and multiparameter analysis, along with the numerical simulations for reconstructing the magnetic footpoints of the Parker spiral on the Sun’s surface, offer a detailed cause-and-effect framework for studying space weather events in the Solar System.

In early 2024 May, the solar active region AR 13664 released a series of X-class solar flares and multiple coronal mass ejections (CMEs) that resulted in the strongest geomagnetic storm of the last 20 yr. This study aims at improving our understanding of the magnetic connectivity between Earth and the solar corona by reconstructing the magnetic footpoint of the Earth on the solar surface during this geomagnetic superstorm. A Monte Carlo simulation was applied to model the random walk of interplanetary magnetic field lines due to low-frequency turbulence in the solar wind. This model uses local diffusion coefficients dependent on magnetic fluctuations and the correlation length of solar wind turbulence. The simulation revealed an enhanced diffusion of magnetic field lines due to the passage of CMEs, leading to a broader area of solar surface magnetically connected to Earth, particularly near AR 13664. This proximity facilitated the rapid propagation of solar energetic protons, increasing fluxes observed at L1. The findings have significant implications for predicting space weather effects on Earth and other solar system bodies, contributing to the development of more accurate models for future space exploration missions. Since the Parker spiral reconstruction is consistent with the Magnetic Connectivity Tool, validating the model's reliability, it shows promise for reconstructing magnetic connections for potential real-time purposes.

A comparison of three types of ionosonde data from Europe during an interplanetary coronal mass ejection (ICME)- and a corotating interaction region (CIR)-driven geomagnetic storm event is detailed in this study. The selected events are 16–20 March 2015 for the ICME-driven storm and 30 May to 4 June 2013 for the CIR-driven one. Ionospheric data from three European ionosonde stations, namely Pruhonice (PQ), Sopron (SO) and Rome (RO), are investigated. The ionospheric F2-layer responses to these geomagnetic events are analyzed with the ionospheric foF2 and h’F2 parameters, the calculated deltafoF2 and deltahF2 values, the ratio of total electron content (rTEC) and Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite Global Ultraviolet Imager (GUVI) thermospheric [O]/[N₂] measurement data. The storm-time and the quiet-day mean values are also compared, and it can be concluded that the quiet-day curves are similar at all the stations while the storm-time ones show the latitudinal dependence during the development of the storm. As a result of the electron density comparison, during the two events, it can be concluded that the sudden storm commencement (SSC) that characterized the ICME induced a traveling atmospheric disturbance (TAD) seen in the European stations in the main phase, while this is not seen in the CIR-driven ionospheric storm, which shows a stronger and more prolonged negative effect in all the stations, probably due to the season and the depleted O/N₂ ratio.

The comparison of three types of ionosonde data from Europe during an Interplanetary Coronal Mass Ejection (ICME) and a Stream Interaction Regions (SIRs) / Corotating Interaction Regions (CIRs) -driven geomagnetic storm event is detailed in this study. The selected events are 16-20 March 2015 for the ICME-driven and 30 May to 04 June 2013 for the SIR/CIR-driven one. Ionospheric data from three European ionosonde stations, namely Pruhonice (PQ), Sopron (SO) and Rome (RO), are investigated. The ionospheric F2-layer responses to these geomagnetic events are analyzed with the ionospheric foF2 and h’F2 parameter, the calculated deltafoF2 and deltahF2 values, ratio of Total Electron Content (rTEC) and Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics (TIMED) satellite Global Ultraviolet Imager (GUVI) thermospheric [O]/[N2] measurement data. The storm-time and the quiet day mean values are also compared, and it can be concluded that the quiet day curves are similar at all stations while the storm-time ones showed the latitudinal dependence during the development of the storm. As a result of the electron density comparison, during the two events it can be concluded that SSC that characterized the ICME induced a Travelling Atmospheric Disturbance (TAD) seen in the European stations, while this is not in the SIR/CIR-driven ionospheric storm, which showed a stronger and more prolonged negative effect in all stations probably due to the season.

We present a study conducted on a number of selected events characterised by a significant increase in the solar proton fluxes measured by FIPS-MESSENGER during the period 2011-2013. For each of them, the magnetic connection between Mercury and the solar corona (Source Surface Field @2.5 RS) has been reconstructed, in order to identify the possible source of the accelerated particles on the solar surface. The transport of the magnetic field lines in the heliosphere is here evaluated with a Monte Carlo code that computes a random displacement at each step of the integration along the Parker magnetic field model. Such displacement is proportional to a “local” diffusion coefficient, which is a function of the fluctuation level and magnetic turbulence correlation lengths. The simulation is tailored to the specific events by using the observed values of solar wind velocity and magnetic fluctuation levels.