Periodic Reporting for period 1 - SERPENTINE (Solar EneRgetic ParticlE aNalysis plaTform for the INner hEliosphere) Reporting period: 2021-01-01 to 2021-12-31 Summary of the context and overall objectives of the project The Solar EneRgetic ParticlE aNalysis plaTform for the INner hEliosphere (SERPENTINE) project will answer several outstanding questions about the origin of Solar Energetic Particle (SEP) events and provides an advanced platform for the analysis and visualization of high-level datasets to benefit the wider heliophysics community. The key data comes from the most recent European and US missions, i.e. Solar Orbiter, Parker Solar Probe and BepiColombo, which have opened completely new avenues to investigate SEPs.The strongest SEP events constitute so-called solar radiation storms, which are part of space weather. These storms pose a radiation hazard to satellites in Earth orbit and beyond. Since a major part of our technology dependent society relies on the space sector (global navigation satellite systems, satellite telecommunication systems, Earth observation), a radiation storm knocking down a part of in-orbit resources could lead to severe consequences for the global economy. The strongest radiation storms can also have health effects on humans in space and even at flight altitudes in polar regions, which the highest energy particles are able to reach while the Earth’s magnetic field provides a deflective barrier at lower latitudes. Solar radiation storms also affect the polar ionosphere rendering HF radio communications unavailable during storm times, which again prohibits air traffic through the poles. Therefore, understanding SEP events is one of the key pre-requisites for developing space weather forecasting capabilities in the future.The project will focus on unravelling the causes of currently poorly understood large gradual and widespread SEP events. These events also pose the greatest radiation risk to spacecraft outside the shielding provided by Earth’s magnetic field. Our platform is expected to significantly foster the further exploitation of the data from European space-borne and ground-based instrumentation and interactions between different communities during and after the project period.The overall scientific objective SERPENTINE is to understand the acceleration and heliospheric transport of particles in large and widespread SEP events. To address this objective, SERPENTINE will address the following open science questions:Q1: What are the primary causes for widespread SEP events observed in the heliosphere?Q2: What are the shock acceleration mechanisms responsible for accelerating ions from thermal/suprathermal energies to near-relativistic energies in the corona and in the interplanetary medium?Q3: What is the role of shocks in electron acceleration in large gradual and widespread events? How does it relate to ion acceleration and what is its importance relative to flare acceleration?In the core of the SERPENTINE project are also the following technical objectives to achieve a maximal impact for exploitation of the data by the wider scientific community:T1: Produce and distribute catalogs of SEP events and in-situ shock events.T2: Provide an analysis platform with the data and tools for analysis along with visualization of the modeled heliospheric state.T3: Produce and deliver high-level and multi-instrument datasets for SEPs and the necessary ancillary data. Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far The frequency of SEP events varies over time in 11-year solar-activity cycles. At present solar activity is in an ascending phase. Thus, the Sun is getting more active in producing SEPs. We have analysed strong and widespread SEP events as well as weaker events that were observed in connection with interplanetary shock waves driven by coronal mass ejections (CMEs) while propagating through the solar wind. While the number of observed events is still small, the new datasets have been clearly demonstrated as being capable of shedding light to the open science questions that SERPENTINE wants to answer.We have also analysed data from older missions. A comprehensive catalogue of SEP events from the Helios mission (from mid 1970s to early 1980s) was produced. Helios had two spacecraft orbiting the Sun in elliptic orbits that reached a distance from the Sun of about a third of the Sun-Earth distance. Thus, like the present heliospheric fleet it had capabilities to observe SEP events from close distances to the Sun, but lacked the comprehensive context observations of the Sun that are important for the comprehensive interpretation of the events observed. Therefore, rather than detailed case studies, we will concentrate on statistical analyses of these events in order to prepare for the analyses of the events of the present solar activity cycle and to compare results between two solar activity cycles to learn about their similarities and differences.Another dataset comes from the STEREO mission with two spacecraft orbiting the Sun approximately at Earth’s distance but at different positions relative to the Earth. We analysed a sample of 33 events for which a comprehensive analysis of the solar eruption associated with the event was performed earlier. The earlier study showed a strong connection between energetic proton acceleration and properties of the coronal shock wave driven by the eruption. Our new study established a very similar connection between the shock and the energetic electrons — a major step forward in our understanding of the role of coronal shocks in the acceleration of electrons to the highest energies.The project also produced and released its first analysis tools, e.g. the Solar-MACH tool (https://solar-mach.github.io/) which shows the configuration of the heliospheric spacecraft and planets in their orbits around the Sun at any given time. SERPENTINE also contributed new datasets to existing analysis platforms and provided access to the Helios catalogue through a prototype server operated at the University of Alcala and to be released to the public during the second year of the project. Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far) During its first year, the project has provided several important science results that already contribute to answering the science questions Q1-Q3 of the project. In addition to heliophysicists, also the astrophysics community will have a great interest on scientific results on particle acceleration at shock waves. It has also already published its first data analysis tool to the heliophysics community — the SolarMACH tool — that provides an easy way to plot the configurations of spacecraft and planets in the inner heliosphere.An important aspect of the project’s impact is the foundation it gives for the development of practical space weather applications. Solar radiation storms generated by the large gradual SEP events are one of the main deleterious aspects of space weather, capable of disrupting satellite services and even air traffic over polar areas. Europe has a vibrant community, including several enterprises, working on space weather prediction tools and that sector will appreciate the improved access to data generated by SERPENTINE. Other sectors that the project will cater to include the university education (production of new educational material on SEP events) and space agencies and policymakers that take decisions on future solar and heliospheric missions to be launched. The project will also make an effort to educate the general public on solar eruptions and their effects on the society. These efforts have already been started during the first year through events targeted to public and through postings in social media. Illustration of a flare showing potential solar energetic particle source regions (image from NASA)
