Evolución galáctica de los elementos ligeros

Un modelo de evolución galáctica permite representar los cambios que ocurren desde la formación de la galaxia hasta su estado actual, atendiendo fundamentalmente a las características evolutivas de las estrellas que la constituyen y a su ritmo de crecimiento. Dado que un modelo global de evolución debe ser necesariamente un compendio de los resultados de numerosas teorías individuales que describen fenómenos particulares de la galaxia, se trata de un instrumento de gran utilidad para buscar y confirmar (o en su caso negar) relaciones entre las teorías que lo componen, o bien para comparar modelos galácticos que representen galaxias de diversas clases. Actualmente no puede hablarse de un modelo evolutivo úinico, ya que el escaso conocimiento que se tiene de algunas cuestiones dan lugar a varios modelos, todos ellos coherentes con los datos de que se dispone. En su ya clásico artículo de 1957, Burbidge et al. conseguían explicar la síntesis del litio a partir del hidrógeno y del helio en las reacciones termonucleares que se dan en el interior de las estrellas. Sin embargo, al ser un elemento muy frágil y hallarse expuesto continuamente al bombardeo por protones, era destruido “in situ”. Su conclusión era que los elementos ligeros se deberían producer en un medio a temperatura y densidad bajas, por un mecanismo entonces no conocido que denominaron “proceso x”. El hecho de que los elementos ligeros sean fácilmente destruidos en los interiors estelares hace especialmente interesante su inclusion y studio en un modelo de evolución química de la galaxia, pues del conocimiento de la variación de sus abundancias en el gas interestelar y en las estrellas se podrá deducir la importancia de los diversos mecanismos que los sintetizan y destruyen, y su incidencia en la evolución de la galaxia. Dejando aparte la possible producción cosmológica del litio, las contribuciones más importantes a la formación de elementos ligeros se dan a partir de la radiación cósmica, al interaccionar ésta con el medio interestelar produciéndose reacciones de astillado a alta energía, y por reacciones del mismo tipo con partículas supratérmicas de baja energía en las inmediaciones de las supernovas y en las atmósferas de estrellas gigantes, material que posteriormente pierde la Estrella por viento estelar. La abundancia final de elementos ligeros en el medio interestelar será el resultado de la mezcla del gas con el material irradiado y enriquecido en estos procesos. En este trabajo se estudiará la evolución de dichos elementos en el marco de diversos modelos galáctivos y a la luz de los últimos resultados sobre su formación por la radiación cósmica galáctica (Reeves y Meyer 1978), y en las supernovas y estrellas gigantes (Canal, Isern y Sanahuja 1975, 1977 a/b)

Evolución galáctica de los elementos ligeros

[spa] Un modelo de evolución galáctica permite representar los cambios que ocurren desde la formación de la galaxia hasta su estado actual, atendiendo fundamentalmente a las características evolutivas de las estrellas que la constituyen y a su ritmo de crecimiento. Dado que un modelo global de evolución debe ser necesariamente un compendio de los resultados de numerosas teorías individuales que describen fenómenos particulares de la galaxia, se trata de un instrumento de gran utilidad para buscar y confirmar (o en su caso negar) relaciones entre las teorías que lo componen, o bien para comparar modelos galácticos que representen galaxias de diversas clases. Actualmente no puede hablarse de un modelo evolutivo úinico, ya que el escaso conocimiento que se tiene de algunas cuestiones dan lugar a varios modelos, todos ellos coherentes con los datos de que se dispone. En su ya clásico artículo de 1957, Burbidge et al. conseguían explicar la síntesis del litio a partir del hidrógeno y del helio en las reacciones termonucleares que se dan en el interior de las estrellas. Sin embargo, al ser un elemento muy frágil y hallarse expuesto continuamente al bombardeo por protones, era destruido “in situ”. Su conclusión era que los elementos ligeros se deberían producer en un medio a temperatura y densidad bajas, por un mecanismo entonces no conocido que denominaron “proceso x”. El hecho de que los elementos ligeros sean fácilmente destruidos en los interiors estelares hace especialmente interesante su inclusion y studio en un modelo de evolución química de la galaxia, pues del conocimiento de la variación de sus abundancias en el gas interestelar y en las estrellas se podrá deducir la importancia de los diversos mecanismos que los sintetizan y destruyen, y su incidencia en la evolución de la galaxia. Dejando aparte la possible producción cosmológica del litio, las contribuciones más importantes a la formación de elementos ligeros se dan a partir de la radiación cósmica, al interaccionar ésta con el medio interestelar produciéndose reacciones de astillado a alta energía, y por reacciones del mismo tipo con partículas supratérmicas de baja energía en las inmediaciones de las supernovas y en las atmósferas de estrellas gigantes, material que posteriormente pierde la Estrella por viento estelar. La abundancia final de elementos ligeros en el medio interestelar será el resultado de la mezcla del gas con el material irradiado y enriquecido en estos procesos. En este trabajo se estudiará la evolución de dichos elementos en el marco de diversos modelos galáctivos y a la luz de los últimos resultados sobre su formación por la radiación cósmica galáctica (Reeves y Meyer 1978), y en las supernovas y estrellas gigantes (Canal, Isern y Sanahuja 1975, 1977 a/b)

Solar Particle Radiation Storms Forecasting and Analysis: The HESPERIA HORIZON 2020 Project and Beyond

The scenario and fundamentals of the physics of charged particle interplanetary transport are briefly introduced. Relevant characteristics of solar energetic particle (SEP) events and of the interplanetary magnetic field are described. Next, the motion of a charged particle and the main assumptions leading to the description of the focused and diffusive particle transport equations utilised in the next chapters are discussed. Finally, two different models are applied to interpret SEP events.</p

Modelling large solar proton events with the shock-and-particle model: Extraction of the characteristics of the MHD shock front at the cobpoint

We have developed a new version of a model that combines a two-dimensional Sun-to-Earth magnetohydrodynamic (MHD) simulation of the propagation of a CME-driven shock and a simulation of the transport of particles along the interplanetary magnetic field (IMF) line connecting the shock front and the observer. We assume that the shock-accelerated particles are injected at the point along the shock front that intersects this IMF line, i.e. at the cobpoint. Novel features of the model are an improved solar wind model and an enhanced fully automated algorithm to extract the necessary plasma characteristics from the shock simulation. In this work, the new algorithms have been employed to simulate the 2000 April 4 and the 2006 December 13 SEP events. In addition to quantifying the performance of the new model with respect to results obtained using previous versions of the shock-and-particle model, we investigate the semi-empirical relation between the injection rate of shock-accelerated particles, Q, and the jump in speed across the shock, VR, known as the Q(VR) relation. Our results show that while the magnetic field and density compression at the shock front is markedly different than in our previous modeling, the evolution of VR remains largely similar. As a result, we confirm that a simple relation can still be established between Q and VR, which enables the computation of synthetic intensity-time profiles at any location in interplanetary space. Furthermore, the new shock extraction tool is found to yield improved results being in general more robust. These results are important not only with regard to efforts to develop coupled magnetohydrodynamic and particle simulation models, but also to improve space weather related software tools that aim to predict the peak intensities, fluences and proton intensity-time profiles of SEP events (such as the SOLPENCO tool)

Solar Particle Radiation Storms Forecasting and Analysis: The HESPERIA HORIZON 2020 Project and Beyond

Solar γ-ray events recently detected by the Fermi/LAT instrument at energies above 100 MeV have presented a puzzle for solar physicists as many of such events were observed lasting for many hours after the associated flare/coronal mass ejection (CME) eruption. Data analyses suggest the γ-ray emission originate from decay of pions produced mainly by interactions of high-energy protons deep in the chromosphere. Whether those protons are accelerated in the associated flare or in the CME-driven shock has been under active discussion. In this chapter, we present some modelling efforts aimed at testing the shock acceleration hypothesis. We address two γ-ray events: 2012 January 23 and 2012 May 17 and approach the problem by, first, simulating the proton acceleration at the shock and, second, simulating their transport back to the Sun.</p

EUropean Heliospheric FORecasting Information Asset 2.0

Aims: This paper presents a H2020 project aimed at developing an advanced space weather forecasting tool, combining the MagnetoHydroDynamic (MHD) solar wind and coronal mass ejection (CME) evolution modelling with solar energetic particle (SEP) transport and acceleration model(s). The EUHFORIA 2.0 project will address the geoeffectiveness of impacts and mitigation to avoid (part of the) damage, including that of extreme events, related to solar eruptions, solar wind streams, and SEPs, with particular emphasis on its application to forecast geomagnetically induced currents (GICs) and radiation on geospace. Methods: We will apply innovative methods and state-of-the-art numerical techniques to extend the recent heliospheric solar wind and CME propagation model EUHFORIA with two integrated key facilities that are crucial for improving its predictive power and reliability, namely (1) data-driven flux-rope CME models, and (2) physics-based, self-consistent SEP models for the acceleration and transport of particles along and across the magnetic field lines. This involves the novel coupling of advanced space weather models. In addition, after validating the upgraded EUHFORIA/SEP model, it will be coupled to existing models for GICs and atmospheric radiation transport models. This will result in a reliable prediction tool for radiation hazards from SEP events, affecting astronauts, passengers and crew in high-flying aircraft, and the impact of space weather events on power grid infrastructure, telecommunication, and navigation satellites. Finally, this innovative tool will be integrated into both the Virtual Space Weather Modeling Centre (VSWMC, ESA) and the space weather forecasting procedures at the ESA SSCC in Ukkel (Belgium), so that it will be available to the space weather community and effectively used for improved predictions and forecasts of the evolution of CME magnetic structures and their impact on Earth. Results: The results of the first six months of the EU H2020 project are presented here. These concern alternative coronal models, the application of adaptive mesh refinement techniques in the heliospheric part of EUHFORIA, alternative flux-rope CME models, evaluation of data-assimilation based on Karman filtering for the solar wind modelling, and a feasibility study of the integration of SEP models

EUropean Heliospheric FORecasting Information Asset 2.0

Aims: This paper presents a H2020 project aimed at developing an advanced space weather forecasting tool, combining the MagnetoHydroDynamic (MHD) solar wind and coronal mass ejection (CME) evolution modelling with solar energetic particle (SEP) transport and acceleration model(s). The EUHFORIA 2.0 project will address the geoeffectiveness of impacts and mitigation to avoid (part of the) damage, including that of extreme events, related to solar eruptions, solar wind streams, and SEPs, with particular emphasis on its application to forecast geomagnetically induced currents (GICs) and radiation on geospace. Methods: We will apply innovative methods and state-of-the-art numerical techniques to extend the recent heliospheric solar wind and CME propagation model EUHFORIA with two integrated key facilities that are crucial for improving its predictive power and reliability, namely (1) data-driven flux-rope CME models, and (2) physics-based, self-consistent SEP models for the acceleration and transport of particles along and across the magnetic field lines. This involves the novel coupling of advanced space weather models. In addition, after validating the upgraded EUHFORIA/SEP model, it will be coupled to existing models for GICs and atmospheric radiation transport models. This will result in a reliable prediction tool for radiation hazards from SEP events, affecting astronauts, passengers and crew in high-flying aircraft, and the impact of space weather events on power grid infrastructure, telecommunication, and navigation satellites. Finally, this innovative tool will be integrated into both the Virtual Space Weather Modeling Centre (VSWMC, ESA) and the space weather forecasting procedures at the ESA SSCC in Ukkel (Belgium), so that it will be available to the space weather community and effectively used for improved predictions and forecasts of the evolution of CME magnetic structures and their impact on Earth. Results: The results of the first six months of the EU H2020 project are presented here. These concern alternative coronal models, the application of adaptive mesh refinement techniques in the heliospheric part of EUHFORIA, alternative flux-rope CME models, evaluation of data-assimilation based on Karman filtering for the solar wind modelling, and a feasibility study of the integration of SEP models.</p

Review of solar energetic particle models

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.</p

Review of solar energetic particle prediction models

K. Whitman et alSolar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.The ISEP project is supported by the Advanced Exploration Systems Division under the Human Exploration and Operations Mission Directorate of NASA and performed in support of the Human Health and Performance Contract for NASA (NNJ15HK11B). The HESPERIA project was funded through the European Union’s HORIZON 2020 research and Innovation Programme (Contract No 637324) and coordinated by the National Observatory of Athens in Greece. PARADISE has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0) and the ESA project "Heliospheric modelling techniques“ (Contract No. 4000133080/20/NL/CRS). The code was developed in the framework of the projects C14/19/089 (C1 project Internal Funds KU Leuven), G.0D07.19N (FWO-Vlaanderen), SIDC Data Exploitation (ESA Prodex-12), and Belspo project B2/191/P1/SWiM. Predictive Science Inc. was supported by NASA grants 80NSSC19K0067 and 80NSSC20K0285, and NSF grant ICER1854790. The development of the Sadykov et al. model was supported by NASA ESI grant 80NSSC20K0302 and NSF FDSS grant 1936361. JGL and COL acknowledge support for the SEPMOD model development for CCMC under National Aeronautics and Space Administration (NASA) Grant/Cooperative Agreement 80NSSC20K1873 from GSFC to UCB/SSL, with additional support to COL from AFOSR Grant FA9550-16–1-0418. SEPSTER was supported by the NASA Living With a Star Program (grants NNX15AB80G and NNG06EO90A), and by the CCMC/SRAG ISEP project. SEPSTER2D was funded by the NASA/HSR program NNH19ZDA001NHSR, the Goddard Space Flight Center / Internal Scientist Funding Model (ISFM) grant HISFM18, and the Johnson Space Center / Space Radiation Analysis Group (SRAG) under the Integrated Solar Energetic Proton Alert/Warning System (ISEP) project. SOLPENCO was funded by the ESA contract 14098/99/NL/MM and its validation by the Spanish Ministerio de Educación y Ciencia under the project AYA2004-03022. SOLPENCO2 was developed under ESA’s SEPEM project (Crosby et al., 2015) and updated during ESA’s SOL2UP project (Aran et al., 2017), both projects under ESA’s contract n. 20162/06/NL/JD and 4000114116/15/NL/HK, respectively. SPARX was initially developed as part of the European Union-funded Seventh Framework Programme (FP7) COMESEP project. The development of the SPREADFAST framework has been funded by a contract to the ESA. SD and CW acknowledge support from NERC via grant NE/V002864/1.Peer reviewe