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High Energy Solar Particle Events foRecastIng and Analysis

Periodic Reporting for period 1 - HESPERIA (High Energy Solar Particle Events foRecastIng and Analysis)

Reporting period: 2015-05-01 to 2017-04-30

HESPERIA has unfolded both the physical processes resulting into high-energy SEP events and also built novel forecasting operational services in order to enhance the performance of solar radiation storm prediction. SEP events pose important challenges for modern society, largely relying on technology. They have effects both on technological systems and on human health. They can cause Single Event Upsets, solar cell degradation, interference with CCD imaging devices, star tracking positioning problems, and increased space radiation for space missions. High-energy SEPs may have easier access to the polar regions near Earth’s magnetic poles than at the equator, thus, high inclination LEO satellites can at times be vulnerable to SEPs, and the International Space Station (ISS). SEP events can also affect signal propagation between the Earth and satellites due to polar cap absorption events resulting from intense ionization of the polar ionosphere. When SEPs reach aviation altitudes they can be a serious hazard for human health, since the radiation dose received can increase significantly, particularly during high-latitude flights and polar routes. For commercial aviation this can be a risk for frequent flyers and aircrew. >30 MeV protons can be a fatal radiation hazard for astronauts. Overall objectives are: 1) To develop two novel SEP forecasting schemes based upon proven concepts, 2) To develop SEP forecasting tools searching for electromagnetic proxies of the γ-ray emission in order to predict large SEP events, 3) To perform systematic exploitation of the novel high-energy γ-ray observations of the FERMI mission together with in situ SEP measurements near 1 AU, 4) To provide for the first time publicly available software to invert neutron monitor (ΝΜ) observations of relativistic SEPs to physical parameters that can be compared with the space-borne measurements at lower energies, 5) To perform examination of currently unexploited tools, 6) To design recommendations for future SEP forecasting systems . Two novel real-time SEP forecasting systems have been developed, HESPERIA REleASE generating proton flux alerts at 30-50 MeV, making use of SOHO/EPHIN relativistic electrons and ACE/EPAM near-relativistic electrons and HESPERIA UMASEP-500 which makes real-time predictions of the occurrence of GLE events, from the analysis of soft X-ray and differential proton flux measured by the GOES satellites. The latter is the only GLE predictor with a performance exceeding that of the NM based ones. A unique GLE inversion software was developed to derive the solar source function and the interplanetary transport parameters of relativistic SEPs observed near Earth. The extensive data analysis of 25 high-energy γ-ray events detected by Fermi/LAT showed that the SEP events associated with long-duration γ-ray emission are remarkable, often widespread, but not unique in terms of SEP characteristics. It was found that there is no evidence for time-extended electron acceleration in the low corona, close to the flaring active region, after the early post-impulsive phase. Comparison of the statistical characteristics of the solar cycles 23 (SC23) and 24 (SC24) showed the total number of SEP events is about 1/3 lower in SC24 compared to SC23, for both low and high energies. Using a joint Ne/O and Fe/O data analysis correction of the interplanetary transport effect was carried out and the Fe-poor and Fe-rich large SEP events were identified and compared in both cycles.
The project work has consisted of data analysis and modelling for the development of two novel near-real-time prototype tools, the HESPERIA UMASEP-500 tool, for predicting >500 MeV SEP events and the HESPERIA REleASE for predicting 30-50 MeV SEP events, both operational via the project’s website. Two post-event prediction tools were developed exploring the usefulness of microwave data for SEP prediction. The interpretation of the results of SEP modeling showed shock acceleration is a possible mechanism to account for the observed γ-ray emission. A new single-step inversion software was developed to derive the energy spectra and the directional distributions of relativistic SEPs at the outer boundary of the Earth’s magnetosphere from NM observations and the solar source function and the interplanetary transport parameters of relativistic SEPs observed near Earth. A new proton list based on the 14-17 MeV proton data by SOHO/ERNE has been constructed and correlation analysis between the SEP events and their parent solar activity was carried out and comparison between the SC23 and SC24 was performed. A joint analysis of Ne/O and Fe/O data was carried out and used as a diagnostic tool, in order to identify the Fe-poor and Fe-rich events in each cycle. Dissemination of the HESPERIA results and SEP forecasting tools has taken place via presentations in international conferences, publications in refereed journals and outreach activities (e.g. Researcher’s nights in Europe). HESPERIA UMASEP-500 predicts ~50% of the GLE events with a warning time of 8-15 minutes with respect to NM based warnings and can be utilized by aircraft operators, telecommunication companies and space operators. HESPERIA REleASE can be useful for applications for spacecraft operations, to investigate in near-real time the influence of SEPs to space electronics and utilize it for actions preventing severe failures. Both forecasting tools could be exploited by the Space Situational Awareness (SSA) programme of ESA and by the Community Coordinated Modeling Center (CCMC) of NASA. The GLE inversion software can be used for further scientific exploitation and dosimetry. The solar cycle comparison results can serve as a baseline for future solar missions.
HESPERIA UMASEP-500 and HESPERIA REleASE, building upon and expanding the new limits of proven forecasting approaches (UMASEP, REleASE), contribute new upgraded services able to predict, with a significantly higher precision than previously, space weather events affecting the Earth and the near-Earth space environment. HESPERIA also provided an in depth feasibility study on the usage of microwave data to SEP forecasting, utilizing the UMASEP concept, which demonstrated that microwave data can be used as proxies for the SEP occurrence and that they can be integrated into a space weather service, replacing the soft X-ray recordings routinely used in such forecasting schemes. HESPERIA provided freely available software for the full inversion of GLE events, providing a breakthrough to the scientific community. HESPERIA developed concepts and tools that can be integrated into space weather prediction services. An example is the project Civil Aviation to set up a space weather warning center especially for transpolar flights, where many aircraft rely on HF communications. HESPERIA is an asset for Civil Aviation, since it provides real-time forecasting of high-energy SEPs, relevant to the recorded radiation dose enhancements present at high-latitude flights. Those forecasts are evidently of major interest for satellites in near-Earth orbit (e.g. telecommunications) since they can provide a fair forewarning to spacecraft operators, assisting them to apply mitigation actions in time and thus secure the communications at Earth. Furthermore, the SEP forecasts provided by HESPERIA are of major interest for operations of the ISS as well as for human space exploration.
Space Situational Awareness: Space Weather, Credit: ESA-P. Carril