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The field of atmospheric electricity has been very active in the last decades [...]

SUMARIO : La física solar en el IAA: investigación integral de nuestra estrella.- El imaginario del planeta rojo a través del arte.- Deconstrucción. La covid-19 y los rayos de tormenta.- El Moby Dick de David Martínez-Delgado (IAA-CSIC).- Historias: Accidente en Marte.- Actualidad.- Pilares e incertidumbres., Este número ha contado con el apoyo económico de la Agencia Estatal de Investigación (Ministerio de Ciencia, Innovación y Universidades) a través de la acreditación de Centro de Excelencia Severo Ochoa para el Instituto de Astrofísica de Andalucía (SEV-2017-0709). La página web de esta revista ha sido financiada por la Sociedad Española de Astronomía (SEA).

REPORTAJES: Fotografiando lo invisible.-- De Sevilla a Cádiz por Granada: el IAA .-- Ciencia en historias. Nuestra primera astrónoma.-- Deconstrucción. Impactos en la Luna.-- El Moby Dick de... Romano Corradi (IAC/GTC).-- Actualidad.-- Sala limpia. Sondas encantadoras, rovers adorables.-- Pilares e incertidumbres. Zonas de habitabilidad galáctica.-- Proyecto PIIISA, La página web de esta revista ha sido financiada por la Sociedad Española de Astronomía (SEA).

In this doctoral thesis we describe the development and results of several models to study electricity phenomena in the atmospheres of Venus, Earth, Jupiter and Saturn. In addition, in the context of the future launch of ASIM (ESA) in 2018 and TARANIS (CNES) in 2019, we present two methods to analyze the optical signals emitted by Transient Luminous Events (TLEs) from space-based photometers. We have developed two electrodynamical models to simulate the inception and evolution of halos and elves in planetary atmospheres. These models have been coupled with di erent sets of chemical reactions to describe TLEs in the upper atmospheres of Venus, Earth, Jupiter and Saturn. The terrestrial versions of these models have allowed us to quantify the local chemical impact of halos and elves in the atmosphere of the Earth. We have used these results together with the TLE occurrence rate reported by ISUAL (NSPO) to estimate the global impact of these events in the chemistry of the terrestrial mesosphere. We have also investigated the similarities and di erences between elves triggered by di erent types of lightning discharges, such as cloud-to-ground (CG) discharges, Compact Intracould Discharges (CIDs) and Energetic In-cloud Pulses (EIPs). Finally, the model of halos has been used to calculate the quasielectrostatic eld produced by this type of TLE at ground level., We have compared this result with measurements of electric elds from thunderstorms. The existence of lightning in Venus is still unclear. We have investigated the possibility of detecting Venusian TLE as an indirect evidence of the existence of Venusian lightning discharges. The Venusian versions of the TLEs models have been useful to predict the possible inception of halos and elves in Venus. According to our results, these Venusian TLEs could emit light in a wide range of frequencies of the optical spectrum. Some of these optical emissions would be produced in the 557 nm line. The Akatsuki spacecraft (JAXA), currently orbiting Venus since December 2015, could detect bursts of light in this spectral line. In the case of Jupiter and Saturn, the three-dimensional version of the elve model has enabled us to study the shape and intensity of the predicted optical emissions in the upper atmosphere of the giant gaseous planets depending on the latitude, lightning channel inclination and upper atmospheric composition. In addition, we have concluded that the optical ashes in the Saturnian and Jovian atmosphere detected by several spacecraft as the Voyagers (NASA) and Cassini (NASA, ESA and ASI) come from lightning rather than from elves. However, it is possible that TLEs in the giant planets are triggered by the lightning activity in the atmospheres of Saturn and Jupiter. The models developed in this thesis could help unveil such new optical transient events in coordination with future dedicated instruments to search for such phenomena. We have used a Full Wave Method to investigate the propagation of Very Low Frequency (VLF) waves through planetary atmospheres. In the case of Earth, we have calculated the transfer function of the curved Earth-ionosphere waveguide. This transfer, function is useful to analyze distant sources of electromagnetic pulses. This model has also been particularized to the case of whistler wave propagation through the Venusian atmosphere. The comparison of our results with signals reported by the Pioneer Venus Orbiter (PVO) of NASA and Venus Express (VEX) of ESA has allowed us to derive the rate of occurrence and energy released by hypothetical Venusian lightning radiating electromagnetic waves. Finally, we have used the simulated optical emissions of halos and elves to develop two methods to analyze the emitting source from optical signals recorded by space-based photometers onboard the future space missions ASIM and TARANIS to study atmospheric electricity in the Earth atmosphere. These methods can be used to obtain the temporal evolution of the number of photons emitted by elves and to deduce the reduced electric eld in halos and elves. We have applied one of these methods to the signals reported by GLIMS (JAXA)., This work has been made possible with the nancial assistance of the Spanish Ministry of Science and Innovation, MINECO (previously MICINN) under projects ESP2013-48032-C5-5-R, FIS2014- 61774-EXP, 09-RNP-101 (LESC) (European Science Foundation - Research Networking Programmes), ESP2015-69909-C5-2-R, ESP2017-86263-C4-4-R, H2020-MSCA-ITN-2016 (Marie Curie Innovation Training Networks - ITN) and the EU through the FEDER program.

We investigate the effect of halo activity on the electrostatic field measured at ground level. We use electrostatic arguments as well as self-consistent simulations to show that, due to the screening charge in the ionosphere, the distant electrostatic field created by the uncompensated charge in a thundercloud decays exponentially rather than as the third power of the distance. Furthermore, significative ionization around the lower edge of the ionosphere slightly reduces the electrostatic field at ground level. We conclude that halos do not extend the range of detectability of lightning-induced electrostatic fields., This work was supported by the Spanish Ministry of Science and Innovation, MINECO under projects ESP2013-48032-C5-5-R, FIS2014-61774-EXP, and ESP2015-69909-C5-2-R and by the EU through the FEDER program. F.J.P.I. acknowledges a MINECO predoctoral contract, code BES-2014-069567. A.L. acknowledges support by a Ramon y Cajal contract, code RYC-2011-07801

A self-consistent two-dimensional model is proposed to account for the transient mesospheric nighttime optical emissions associated to possible intracloud (IC) lightning occurring in the Venusian troposphere. The model calculates the mesospheric (between 75km and 120km in altitude) quasi-elestrostatic electric field and electron density produced in response to IC lightning activity located between 40km and 65km in the Venusian cloud layer. The optical signatures and the densities of perturbed excited atomic and molecular neutral and ionic species in the mesosphere of Venus are also calculated using a basic kinetic scheme. The calculations were performed for different IC lightning discharge properties. We found that the calculated electric fields in the mesosphere of Venus are above breakdown values and that, consequently, visible transient glows (similar to terrestrial Halos produced by lightning) right above the parent IC lightning are predicted. The transient optical emissions result from radiative deexcitation of excited electronic states of N-2 (in the ultraviolet, visible and near-infrared ranges) and of O(S-1) and of O(D-1) in, respectively, the green (557nm) and red (630nm) wavelengths. The predicted transient lightning-induced glows from O(S-1) can reach an intensity higher than 167R and, consequently, be above the detection threshold of the Lightning and Airglow Camera instrument aboard the Japanese Akatsuki probe orbiting Venus since December 2015. However, according to our model, successful observations of transient lightning-induced optical glows could only be possible for sufficiently close (300km or maximum 1000km) distances., This work was supported by the Spanish Ministry of Science and Innovation, MINECO under projects ESP2013-48032-C5-5-R, FIS2014-61774-EXP, and ESP2015-69909-C5-2-R and by the EU through the FEDER program. F.J.P.I. acknowledges a MINECO predoctoral contract, code BES-2014-069567. A.L. acknowledges support by a Ramon y Cajal contract, code RYC-2011-07801.

El número contiene las siguientes contribuciones: Rayos en el Sistema Solar.--Galaxias activas: alimentando al monstruo.--Estrellas de la población III.--Planetas azules en torno a estrellas rojas.--Cien años de agujeros negros.--La imagen con mayor resolución de la historia de la astronomía muestra las entrañas de un núcleo galáctico.--La concentración de dióxido de carbono también aumenta en la alta atmósfera.--Se cuestionan los resultados obtenidos hasta ahora en el estudio de estrellas pulsantes.--Estudian la historia de la galaxia Andrómeda a través de sus cadáveres estelares.--Rosetta confirma que el cometa 67P se formó por la fusión de dos objetos.--Sala limpia.--El origen del universo.--Destacados., La página web de esta revista ha sido financiada por la Sociedad Española de Astronomía (SEA).

Tesis del Departamento de Sistema Solar del Instituto de Astrofísica de Andalucía. Leída en el Salón de Actos del IAA el 17 de marzo del 2023, a las 12:00 h ., [EN] The main objective of this doctoral thesis is to exhaustively study the corona-type electrical discharges that take place in storm clouds. Corona discharges are characterized, among other things, by transient optical emissions in the near ultraviolet and visible blue range (280 - 450 nm). This is why they have been called Blue LUminous Events (BLUEs). This thesis presents the first worldwide nighttime climatology of corona discharges in storm clouds by combining two years of BLUEs data recorded by MMIA instrument of ASIM on-board the ISS (Neubert et al., 2019). This doctoral thesis focuses on investigating the physics of BLUEs, with the aim of un- derstanding their nature and determining the mechanisms that produce them. Addition- ally, the thesis addresses the detailed analysis of the geographic and seasonal distribution of BLUEs is addressed from two years of unique data obtained by the Modular Multispec- tral Imaging Array (MMIA) of the European Space Agency’s (ESA) Atmosphere Space Interaction Monitor (ASIM) instrument that was launched into space on April 18, 2018 and has been operational at the International Space Station (ISS) since then. MMIA has three fast photometers (100 kHz) and two cameras. The photometers have interferential filters centered on the wavelengths 337.0 nm (with a width of 4 nm), 777.4 nm (with a width of 5 nm) and a wide filter between 180 nm and 230 nm. The two available cameras use filters centered at 337.0 nm and 777.4 nm with the same characteristics as the light meter filters. The doctoral thesis is presented as a collection of three scientific articles in which I am the first author. These articles have been published in high-impact journals in the field of atmospheric sciences (atmospheric electricity). The articles are preceded by a thesis index, a summary (in Spanish and English), an introduction, the motivation of the studies carried out, a brief description of the methodology that has been followed and a concise presentation of the BLUEs. In my first article (published in Journal of Geophysical Research - Atmospheres, 2020, and highlighted by the editor) the structure of the BLUEs is described based on the observations of a storm recorded by ASIM on May 14, 2019 over Indonesia. The events were observed using the 337.0 nm photometer, during periods of little or no concurrent activity in the photometer centered on the 777.4 nm band (which is typical for lightning optical emissions). Through radio measurements made from the ground, it was concluded, that 7 of the 10 cases analyzed corresponded to positive narrow bipolar events (NBE). NBEs are characterized by being very strong radio frequency (RF) pulses with three important features: (1) their very short duration (about 20 microseconds), (2) a bipolar appearance (very fast rise and fall of two radio pulses of positive and negative polarity or vice versa) of the waveform in the VLF / LF frequency range (10 - 400 kHz) and (3) followed by extremely powerful bursts of radiation. on VHF / HF (3 - 300 MHz). NBEs, when detected in the VLF/LF range, are typically ten times more intense than radio emissions in the high frequency (HF) range typically emitted by normal intracloud and/or intercloud lightning.. In addition, recent observations (2016 and 2017) suggest that NBEs are the result of very fast processes of electrical breakdown in air. Fast breakdown is associated to cold electrical discharges, that is, those that do not heat the surrounding air (unlike normal lightning) and in which the temperature of the ambient electrons reaches very high values of up to 80000 ◦C (about 7 eV) (electron volts). The fact that electrons have a small mass (2000 times lighter than the lightest atom) prevents them from heating the surrounding air. In this first work, a new and innovative method was developed to determine the height of BLUEs in storm clouds from the analysis of their optical signals. In particular, the method is based on fitting the 337.0 nm light curves captured by the MMIA 337.0 nm photometer to a model of light diffusion in storm clouds. The height obtained agrees well with measurements carried out with methods based on ground-based radio detection. The altitude at which these NBEs occur ranges between 8.5 km and 14 km. Obser- vations indicate that single-pulse blue flashes are caused by streamers (air plasma darts with strong head ionization) which, as discussed above, do not heat the air (they are cold discharges). The findings discussed in the first paper led us to conclude that positive NBEs are corona discharges made up of hundreds of millions of positive streamers (the head of the streamer carries positive electrical charge) that form in thunderclouds and that the BLUEs are the optical manifestation of the NBEs. My second article (published in Geophysical Research Letters, 2021), focuses on the global analysis of the blue pulses observed in storm clouds, focusing on studying the relationship of the BLUEs with lightning, both annually and seasonally. For this, a new algorithm has been developed and used to be able to filter the raw information from MMIA, and systematically obtain only the activity of BLUEs, excluding the rest of electrical interactions in storm clouds. The result of this comprehensive work is the first, and so far the only, nocturnal climatology of BLUEs (corona discharge activity in storm clouds) obtained from data from the ASIM MMIA instrument. Our research concluded that approximately 11 BLUEs occur globally every second at local midnight, and the average number of BLUEs on land/sea is 7 to 4. Geographically, the peak of, the distribution of BLUEs is located in a region in northwestern Colombia. Three main zones of atmospheric electrical activity are shown in this distribution: America, Europe / Africa, and Asia / Australia. A zone of weaker BLUE electrical activity has also been found in the Pacific. My third paper (published in Journal of Geophysical Research - Atmospheres, 2022) delves into the results of the second, and focuses on distinguishing different types of blue pulses based on the goodness of their fit with the ”first hitting model” or FHM (model of diffusion of light in storm clouds) and in extracting its main characteristics such as optical power density (μW m−2) of the 337.0 nm pulse maximum, rise time of maximum, total duration, brightness, etc, based on the fit and raw data. In addition, we also found two types of global distributions of BLUEs, depending on whether an extra criteria is applied (or not) to the algorithm of the previous work (paper two) on the South Atlantic Magnetic Anomaly (SAA). This additional criteria is included because a clear oversensing of cosmic rays was observed with ASIM in the SAA region. The extra criteria aims to limit the number of cosmic rays detected by putting a limit on the duration of the events detected in the SAA. It is concluded that the real number of BLUEs would range between the two distributions found in this third work. The analysis of the characteristics of the BLUEs indicates that around 10% of the events are clearly BLUEs with a clear maximum. Most of them have a peak optical power density below 25 μW/m2, occur up to 4 km below the upper cloud boundary and are made up of hundreds of millions of streamers (up to 3 × 109)., [ES] El objetivo de esta tesis doctoral es estudiar de forma exhaustiva las descargas el ́ectricas de tipo corona que tienen lugar en las nubes de tormenta. Las descargas corona se caracterizan, entre otras cosas, por emitir luz en el rango ultravioleta cercano y azul (280 - 450 nm). Es por esto por lo que se las ha llamado Blue LUminous Events (BLUEs). Esta tesis presenta la primera climatolog ́ıa nocturna de descargas de corona en las nubes de tormenta combinando dos a ̃nos de datos de BLUEs recogidos por el instrumento MMIA de ASIM a bordo de la ISS (Neubert et al., 2019). La tesis se centra en, por un lado, investigar la f ́ısica de los BLUEs, esto es, en descifrar su naturaleza y en determinar cu ́ales son los mecanismos que los producen. Por otra lado, se aborda el an ́alisis detallado de la distribuci ́on geogr ́afica y estacional de los BLUEs a partir de dos a ̃nos de datos obtenidos por el Modular Multispectral Imaging Array (MMIA) del instrumento Atmosphere Space Interaction Monitor (ASIM) de la Agencia Espacial Europea (ESA) que fue lanzado al espacio el 18 de abril de 2018 y que est ́a operativo en la Estaci ́on Espacial Internacional (ISS) desde entonces. MMIA est ́a formado por tres fot ́ometros r ́apidos (100 kHz) y dos c ́amaras. Los fot ́ometros disponen de filtros interferenciales centrados en las longitudes de onda 337.0 nm (con una anchura de banda de 4 nm), 777.4 nm (con una anchura de banda de 5 nm) y un filtro ancho entre 180 nm y 230 nm. Las dos c ́amaras disponibles usan filtros centrados en 337.0 nm y 777.4 nm con las mismas caracter ́ısticas que los filtros de los fot ́ometros. La tesis doctoral se presenta como una colecci ́on de tres art ́ıculos cient ́ıficos en los que soy primer autor. Estos art ́ıculos sobre electricidad atmosf ́erica han sido publicados en revistas de alto impacto en el campo de las ciencias atmosf ́ericas. Los art ́ıculos vienen precedidos por un ́ındice de la tesis, un resumen (en espa ̃nol e ingl ́es), una introducci ́on, la motivaci ́on de los estudios realizados, una breve descripci ́on de la metodolog ́ıa que se ha seguido y una descripci ́on concisa de los BLUEs. En mi primer art ́ıculo (publicado en Journal of Geophysical Research - Atmospheres, 2020, y destacado por su editor) se describe la estructura de los BLUEs apoy ́andose en las observaciones de una tormenta registrada por ASIM el 14 de Mayo de 2019 sobre Indonesia. Los eventos fueron observados con el fot ́ometro 337.0 nm, sin actividad con- currente, o despreciable en el fot ́ometro centrado en la banda 777.4 nm (emisiones t ́ıpicas de rayos). A trav ́es de mediciones de radio efectuadas desde el suelo, se concluy ́o que 7, de los 10 casos analizados correspond ́ıan a eventos bipolares estrechos positivos o positive narrow bipolar events (NBE) en ingl ́es. Los NBEs se caracterizan por ser pulsos muy fuertes de radiofrecuencia (RF) con tres rasgos importantes: (1) su muy corta duraci ́on (apenas 20 microsegundos), (2) un aspecto bipolar (muy r ́apida subida y bajada de dos pulsos de radio de polaridad positiva y negativa o viceversa) de la forma de onda en el rango de frecuencias VLF / LF (10 - 400 kHz) y (3) por venir habitualmente seguidos de potent ́ısimos estallidos de radiaci ́on VHF / HF (3 - 300 MHz). Los NBE detectados en el rango VLF / LF son por lo general diez veces m ́as intensos que las emisiones de radio en el rango de alta frecuencia (HF) procedentes de rayos normales intranube o entre nubes. Adem ́as, observaciones recientes (2016 y 2017) parecen sugerir que los NBEs son el resultado de procesos muy r ́apidos de ruptura el ́ectrica del aire t ́ıpicos de descargas el ́ectricas fr ́ıas, esto es, aquellas que no calientan el aire circundante (al contrario que los rayos normales) y en las que la temperatura de los electrones ambientales alcanzan valores muy elevados de hasta 80000 ◦C (unos 7 eV [electr ́on voltios]). El hecho de que los electrones tengan una masa muy peque ̃na (2000 veces m ́as ligeros que el ́atomo m ́as liviano) impide que, a ́un siendo muy energ ́eticos, puedan calentar el aire circundante. En este primer trabajo se desarroll ́o un nuevo y novedoso m ́etodo para determinar la altura de los BLUEs en las nubes de tormenta a partir del an ́alisis de sus se ̃nales ́opticas. En particular, el m ́etodo se basa en ajustar las curvas de luz captadas por el fot ́ometro centrado en 337.0 nm de MMIA a un modelo de difusi ́on de luz en las nubes de tormenta. La altura obtenida concuerda bien con medidas realizadas con m ́etodos basados en radio detecci ́on. La altitud a la que ocurren estos NBEs se sit ́ua aproximadamente entre 8.5 y 14 km. Las observaciones indican que los flashes azules con un solo pulso son originados por streamers (dardos de plasma de aire con fuerte ionizaci ́on en la cabeza) que, como se ha mencionado, no calientan el aire, esto es, son descargas fr ́ıas, la luz emitida por streamers es pues la manifestaci ́on ́optica de dichos NBEs. Los hallazgos que se discuten en el primer trabajo nos llevaron a concluir que los NBEs positivos son descargas corona formadas por cientos de millones de streamers positivos (la cabeza del streamer transporta carga el ́ectrica positiva) que se forman en las nubes de tormenta y que los BLUEs son la manisfestaci ́on ́optica de dichos NBEs. Mi segundo art ́ıculo (publicado en Geophysical Research Letters, 2021), se centra en el an ́alisis a nivel global de los pulsos azules observados en las nubes de tormenta, de- teni ́endose en estudiar la relaci ́on de los BLUEs con los rayos, tanto anual como esta- cionalmente. Para ello se ha desarrollado y utilizado un novedoso algoritmo para poder filtrar la informaci ́on en bruto de MMIA, y obtener sistem ́aticamente s ́olo la actividad, de BLUEs excluyendo el resto de interacciones el ́ectricas en las nubes de tormenta. El resultado de este completo trabajo es la primera, y hasta ahora la ́unica, climatolog ́ıa nocturna de BLUEs (coronas en nubes de tormenta) obtenida a partir de datos del instrumento MMIA de ASIM. En nuestra investigaci ́on se concluy ́o que, aproximada- mente, tienen lugar unos 11 BLUEs a nivel global cada segundo en la media noche local, y que el promedio de BLUEs en tierra / mar es de 7 a 4. Geogr ́aficamente, el pico de la distribuci ́on de BLUEs est ́a localizado en una regi ́on al noroeste de Colombia. En esta distribuci ́on se muestran tres zonas principales de actividad el ́ectrica atmosf ́erica: Am ́erica, Europa/ ́Africa, y Asia/Australia. Tambi ́en se ha encontrado una zona de ac- tividad el ́ectrica m ́as d ́ebil en el Pac ́ıfico. Mi tercer trabajo (publicado en Journal of Geophysical Research - Atmospheres, 2022) profundiza en los resultados del segundo, y se centra en distinguir distintos tipos de pulsos azules en funci ́on de la bondad de su ajuste con el ”first hitting model” ́o FHM (modelo de difusi ́on de luz en las nubes) y en obtener sus principales caracter ́ısticas tales como densidad de potencia ́optica (μW m−2) del m ́aximo del pulso 337.0 nm, tiempo de subida del m ́aximo, duraci ́on total, brillo, etc, con base al ajuste y a los datos en bruto. Adem ́as, tambi ́en encontramos dos tipos de distribuciones globales de BLUEs, dependiendo de si se aplica (o no) un criterio extra al algoritmo del anterior trabajo en la anomal ́ıa magn ́etica del Atlantico Sur (SAA). Este criterio adicional se incluye debido que se observ ́o una clara sobredetecci ́on de rayos c ́osmicos con ASIM en la zona de la SAA. El criterio extra pretende limitar el n ́umero de rayos c ́osmicos detectados poniendo un l ́ımite en la duraci ́on de los eventos detectados en la SAA. Se estima que la cifra real de BLUEs se hallar ́a entre las dos distribuciones encontradas en este ́ultimo trabajo. El an ́alisis de las caracter ́ısticas de los BLUEs nos indica que alrededor del 10% de los eventos son claramente BLUEs con un m ́aximo claro. La mayor ́ıa de ellos tiene una densidad de potencia ́optica por unidad de superficie de pico por debajo de 25 μW/m2, ocurren a una distancia de hasta 4 km por debajo del l ́ımite superior de la nube y est ́an formados por cientos de millones de streamers (hasta 3 × 109)., This thesis was supported by the Spanish Ministry of Science and Innovation, Min- isterio de Ciencia e Innovaci ́on (AEI) under project ESP2017-86263-C4-4-R, PID2019- 109269RB-C43 and the FEDER program. I acknowledge a PhD research contract through the project ESP2017-86263-C4-4-R and I also acknowledge financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrof ́ısica de Andaluc ́ıa (SEV-2017-0709).