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Eruptive Phenomena in the Solar Atmosphere: Radiation-MHD Modeling and Code Development

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Eruptive Phenomena in the Solar Atmosphere: Radiation-MHD Modeling and Code Development Universidad de La Laguna Oficina de Sede Electrónica Entrada Nº registro: 2018/27987 Nº reg. oficina: OF002/2018/24260 Fecha: 11/06/2018 17:53:40 DEPARTAMENTO DE ASTROFISICA Universidad de La Laguna Eruptive phenomena in the solar atmosphere: radiation-MHD modeling and code development Memoria que presenta Daniel N´obrega-Siverio para optar al grado de Doctor por la Universidad de La Laguna. Director: Prof. Fernando Moreno-Insertis Co-supervisor: Dr. Juan Mart´ınez-Sykora INSTITUTO D- ASTROFISICA D- CANARIAS Junio de 2018 Este documento incorpora firma electrónica, y es copia auténtica de un documento electrónico archivado por la ULL según la Ley 39/2015. Su autenticidad puede ser contrastada en la siguiente dirección https://sede.ull.es/validacion/ Identificador del documento: 1311908Código de verificación: QWdYKT2W Firmado por: DANIEL ELIAS NOBREGA SIVERIO Fecha: 08/06/2018 16:42:13 UNIVERSIDAD DE LA LAGUNA Fernando Moreno Insertis 11/06/2018 12:19:50 UNIVERSIDAD DE LA LAGUNA JUAN MARTINEZ SYKORA 11/06/2018 17:51:30 UNIVERSIDAD DE LA LAGUNA 1 / 115 Universidad de La Laguna Oficina de Sede Electrónica Entrada Nº registro: 2018/27987 Nº reg. oficina: OF002/2018/24260 Fecha: 11/06/2018 17:53:40 c Daniel N´obrega-Siverio 2018 Este documento incorpora firma electrónica, y es copia auténtica de un documento electrónico archivado por la ULL según la Ley 39/2015. Su autenticidad puede ser contrastada en la siguiente dirección https://sede.ull.es/validacion/ Identificador del documento: 1311908Código de verificación: QWdYKT2W Firmado por: DANIEL ELIAS NOBREGA SIVERIO Fecha: 08/06/2018 16:42:13 UNIVERSIDAD DE LA LAGUNA Fernando Moreno Insertis 11/06/2018 12:19:50 UNIVERSIDAD DE LA LAGUNA JUAN MARTINEZ SYKORA 11/06/2018 17:51:30 UNIVERSIDAD DE LA LAGUNA 2 / 115 Universidad de La Laguna Oficina de Sede Electrónica Entrada Nº registro: 2018/27987 Nº reg. oficina: OF002/2018/24260 Fecha: 11/06/2018 17:53:40 Resumen En la atm´osferasolar tienen lugar continuamente una extraordinaria variedad de fen´omenos eruptivos que abarcan un amplio rango de escalas espaciales y temporales. De especial in- ter´esson aquellos relacionados con reconexi´onmagn´eticaentre sistemas que interact´uanen la atm´osfera, sobre todo cuando es resultado de emergencia de flujo magn´eticoprocedente del interior solar. Dichos fen´omenoscausan grandes perturbaciones en la atm´osferasolar, liberan energ´ıamagn´eticaque se transforma en energ´ıacin´etica e interna del plasma y radiaci´on, expulsan masa de forma impulsiva, y provocan la reconfiguraci´ondel campo magn´eticocro- mosf´ericoy coronal. Entre los fen´omenos eruptivos, hay uno cuya comprensi´onha progresado lentamente desde que se les conoci´oobservacionalmente hace muchas d´ecadas:los surges. Los surges son eyecciones fr´ıas,densas y no colimadas observadas t´ıpicamente en l´ıneas cromosf´ericas,como Hα 6563 A,˚ con velocidades desde unas pocas hasta varias decenas de km s−1 y longitudes de 10 − 50 Mm. Aparecen frecuentemente en la atm´osferarelacionados con otros eventos de naturaleza ef´ımeracomo estallidos UV o jets coronales de EUV/Rayos- X. Los experimentos num´ericosidealizados del pasado explican los surges como un subpro- ducto de reconexi´onmagn´eticaque tiene lugar entre los sistemas emergentes y preexistentes, y que, con el tiempo, arrastra plasma cromosf´ericoa alturas superiores en la atm´osfera.A pesar de su inter´es,estos experimentos carecen de algunos mecanismos f´ısicosfundamentales a la hora de tratar con los surges, lo que supone que solamente puedan considerarse como primeros pasos en su investigaci´on. Esta tesis abarca el fen´omeno surge desde cuatro puntos de vista: (1) desde su en- foque b´asico,que es te´orico,modela la formaci´ony evoluci´onde los surges usando un c´odigoradiativo-magnetohidrodin´amico(R-MHD) que incluye un tratamiento realista de las propiedades del plasma y del transporte radiativo; (2) desde una perspectiva observa- cional, analiza observaciones coordinadas de alta resoluci´onde la cromosfera y regi´onde transici´on(RT), explora la respuesta de las l´ıneasde RT a la eyecci´onde un surge, y estu- dia la relaci´onestrecha entre surges y otros fen´omenoscomo estallidos UV; (3) desde una perspectiva de modelado directo, crea observaciones sint´eticasque nos permiten entender algunas de las peculiares caracter´ısticasvistas en las observaciones y proporcionarles un fun- damento te´orico;y (4) desde un punto de vista de programaci´oncient´ıfica, desarrolla un m´odulode Fortran que mejora la eficiencia computacional del t´erminode difusi´onambipo- lar, abriendo, de esta manera, la posibilidad de incluir efectos de ionizaci´onparcial en la electrodin´amicade nuestros estudios por medio de la ley generalizada de Ohm. iii Este documento incorpora firma electrónica, y es copia auténtica de un documento electrónico archivado por la ULL según la Ley 39/2015. Su autenticidad puede ser contrastada en la siguiente dirección https://sede.ull.es/validacion/ Identificador del documento: 1311908Código de verificación: QWdYKT2W Firmado por: DANIEL ELIAS NOBREGA SIVERIO Fecha: 08/06/2018 16:42:13 UNIVERSIDAD DE LA LAGUNA Fernando Moreno Insertis 11/06/2018 12:19:50 UNIVERSIDAD DE LA LAGUNA JUAN MARTINEZ SYKORA 11/06/2018 17:51:30 UNIVERSIDAD DE LA LAGUNA 3 / 115 Universidad de La Laguna Oficina de Sede Electrónica Entrada Nº registro: 2018/27987 Nº reg. oficina: OF002/2018/24260 Fecha: 11/06/2018 17:53:40 iv El primer objetivo se logra gracias a las posibilidades ofrecidas por el c´odigoBifrost. Mediante experimentos R-MHD 2.5D de emergencia de flujo magn´eticodesde las capas subyacentes a la superficie solar hasta la corona, hemos encontrado que el surge se forma a pesar de la interacci´onprevia del campo emergente con las celdas granulares en y por debajo de la superficie. El surge se separa de la regi´onemergida como consecuencia de choques fuertes causados por el impacto de plasmoides eyectados a lo largo de la capa de corriente en el sitio de reconexi´on. Durante su ascenso, los elementos de plasma del surge experimentan aceleraciones que superan por mucho la gravedad solar, mientras que en la fase central y de descenso sufren ca´ıdalibre. Usando trazado Lagrangiano detallado, distinguimos diferentes poblaciones de patrones evolutivos dentro del surge, algunas de ellas directamente relacionadas con procesos de calentamiento/enfriamiento incluidos como parte del c´odigo Bifrost. De hecho, hemos encontrado que una fracci´onno despreciable del surge no puede ser reproducida en experimentos previos y m´asidealizados debido a la falta de un tratamiento adecuado para la termodin´amicay fuentes de entrop´ıa. Hemos conseguido el segundo objetivo por medio de observaciones de un surge Hα si- mult´aneoa un estallido UV obtenidos con el Interface Region Imaging Spectrograph (IRIS) y el Swedish 1-m Solar Telescope (SST), respectivamente. Aunque tradicionalmente rela- cionados con l´ıneascromosf´ericas,hemos encontrado que los surges pueden exhibir emisi´on UV realzada en l´ıneasde Si IV con perfiles que son m´asbrillantes y anchos que en una RT promedio. Adem´as,proporcionamos evidencia observacional que respalda el origen com´uny la relaci´onentre surges y estallidos UV. El tercer objetivo se consigue por medio de modelado directo de experimentos num´ericos que incluyen la ionizaci´onfuera del equilibrio de elementos clave en la RT como el silicio y el ox´ıgeno. Los resultados muestran que la RT que envuelve al surge se ve fuertemente afectada por efectos de no-equilibrio, aumentando notablemente el n´umerode emisores de las principales l´ıneasde Si IV y O IV. La desviaci´ondel equilibrio estad´ısticose debe a los tiempos cortos de las p´erdidas´opticamente delgadas y de la conducci´ont´ermicadurante la evoluci´ondel surge. Adem´as,hemos concluido que los efectos de l´ınea de visi´onson importantes para entender los abrillantamientos interminentes en Si IV y O IV dentro de los surges. Finalmente, hemos logrado el ´ultimoprop´ositode esta tesis a trav´esdel desarrollo de un nuevo m´oduloen el c´odigo Bifrost que implementa el m´etodo Super Time-Stepping (STS) para acelerar los c´alculoscon difusi´onambipolar. Mediante un an´alisisen detalle del m´etodo, encontramos la combinaci´on´optimade par´ametrosque garantiza estabilidad y eficiencia. Como primera aproximaci´onal trabajo a realizar en la etapa post-doctoral, en el ´ultimo cap´ıtuloempezamos a explorar los efectos de difusi´onambipolar en el proceso de emergencia de flujo y en el propio surge. Unesco: 210602, 210604, 220409, 220410 Este documento incorpora firma electrónica, y es copia auténtica de un documento electrónico archivado por la ULL según la Ley 39/2015. Su autenticidad puede ser contrastada en la siguiente dirección https://sede.ull.es/validacion/ Identificador del documento: 1311908Código de verificación: QWdYKT2W Firmado por: DANIEL ELIAS NOBREGA SIVERIO Fecha: 08/06/2018 16:42:13 UNIVERSIDAD DE LA LAGUNA Fernando Moreno Insertis 11/06/2018 12:19:50 UNIVERSIDAD DE LA LAGUNA JUAN MARTINEZ SYKORA 11/06/2018 17:51:30 UNIVERSIDAD DE LA LAGUNA 4 / 115 Universidad de La Laguna Oficina de Sede Electrónica Entrada Nº registro: 2018/27987 Nº reg. oficina: OF002/2018/24260 Fecha: 11/06/2018 17:53:40 Abstract A bewildering variety of eruptive and ejective phenomena continually take place in the solar atmosphere on a wide range of space and time scales. Particular attention was devoted in the past decades to those associated with the reconnection of magnetic field lines of separate plasma systems that come into contact in the atmosphere, especially when this is the result of the emergence of magnetic flux from the solar interior. Such events can cause a large disruption of the solar atmosphere, lead to the release of magnetic energy which is turned into kinetic and internal energy of the plasma and radiation, launch impulsive mass ejections, and bring about the reconfiguration of the magnetic domain structure in the chromosphere and corona.
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