Collision-dependent power law scalings in 2D gyrokinetic turbulence

Nonlinear gyrokinetics provides a suitable framework to describe short-wavelength turbulence in magnetized laboratory and astrophysical plasmas. In the electrostatic limit, this system is known to exhibit a free energy cascade towards small scales in (perpendicular) real and/or velocity space. The dissipation of free energy is always due to collisions (no matter how weak the collisionality), but may be spread out across a wide range of scales. Here, we focus on freely-decaying 2D electrostatic turbulence on sub-ion-gyroradius scales. An existing scaling theory for the turbulent cascade in the weakly collisional limit is generalized to the moderately collisional regime. In this context, non-universal power law scalings due to multiscale dissipation are predicted, and this prediction is confirmed by means of direct numerical simulations.Comment: 7 pages, 5 figures, accepted for publication in Physics of Plasma

Gyrokinetic Large Eddy Simulations

The Large Eddy Simulation (LES) approach is adapted to the study of plasma microturbulence in a fully three-dimensional gyrokinetic system. Ion temperature gradient driven turbulence is studied with the {\sc GENE} code for both a standard resolution and a reduced resolution with a model for the sub-grid scale turbulence. A simple dissipative model for representing the effect of the sub-grid scales on the resolved scales is proposed and tested. Once calibrated, the model appears to be able to reproduce most of the features of the free energy spectra for various values of the ion temperature gradient

Free energy cascade in gyrokinetic turbulence

In gyrokinetic theory, the quadratic nonlinearity is known to play an important role in the dynamics by redistributing (in a conservative fashion) the free energy between the various active scales. In the present study, the free energy transfer is analyzed for the case of ion temperature gradient driven turbulence. It is shown that it shares many properties with the energy transfer in fluid turbulence. In particular, one finds a forward (from large to small scales), extremely local, and self-similar cascade of free energy in the plane perpendicular to the background magnetic field. These findings shed light on some fundamental properties of plasma turbulence, and encourage the development of large eddy simulation techniques for gyrokinetics.Comment: 4 pages, 2 Postscript figure

Evaluation of soil salinity indexes based on bulk electrical conductivity

[SPA] Los sensores del suelo que miden conductividad eléctrica (CE) y humedad desempeñan un papel esencial en el control de la salinidad del suelo. Sin embargo, la interpretación precisa de la salinidad del suelo depende del desarrollo de Índices de Salinidad (IS) adecuados. Este trabajo se enfoca en el estudio del potencial de varios IS basados en la CE del medio (ECb), utilizando análisis de regresión para conocer cómo estos IS representan la salinidad del suelo. Los resultados indican que el ECb es un IS eficiente siempre que se mida a humedad constante. Además, la precisión de esta medida aumenta con la humedad del sustrato. La pendiente del ajuste de regresión lineal humedad-ECb se propone como un IS nuevo y fiable. [ENG] Soil sensors that measure electrical conductivity (EC) and moisture play an essential role in monitoring soil salinity. However, the accurate understanding of salinity depends on the development of suitable sensor-based Salinity Indices (SI). This work studied the potential of several SIs based on bulk EC (ECb), which is the only EC directly measured by sensors. Regression studies were performed to know how these SIs describe soil salinity. The results indicate that ECb is an efficient SI as long as humidity is constant. Moreover, its accuracy increases with substrate moisture. The slope of the linear regression fit moisture-ECb is proposed as a novel and reliable SIEsta investigación ha sido financiada por el Ministerio de Ciencia, Innovación y Universidades de España, el Fondo Europeo de Desarrollo Regional, subvención número RTI2018-093997-B-I00, y por la AEI española (subvención número PCI 2019-103608) bajo el programa PRIMA en el marco del proyecto PRECIMED

Axion sourcing in dense stellar matter via CP-violating couplings

Compact objects such as neutron stars and white dwarfs can source axionlike particles and QCD axions due to CP-violating axion-fermion couplings. The magnitude of the axion field depends on the stellar density and on the strength of the axion-fermion couplings. We show that even CP-violating couplings one order of magnitude smaller than existing constraints source extended axion field configurations. For axionlike particles, the axion energy is comparable to the magnetic energy in neutron stars with inferred magnetic fields of the order of 1013 G and exceeds by more than one order of magnitude the magnetic energy content of white dwarfs with inferred fields of the order of 104 G. On the other hand, the energy stored in the QCD axion field is orders of magnitude lower due to the smallness of the predicted CP-violating couplings. It is shown that the sourced axion field can polarize the photons emitted from the stellar surface, and stimulate the production of photons with energies in the radio band.F. A., P. D. L., and A. M. are supported by the Australian Research Council (ARC) Centre of Excellence for Gravitational Wave Discovery (OzGrav), through Project No. CE170100004. P. D. L. is supported through ARC Discovery Project DP220101610. J. A. P. and A. G. acknowledge support from the Generalitat Valenciana Grants No. ASFAE/2022/026 (with funding from NextGenerationEU PRTR-C17.I1) and CIPROM/2022/ 13, and from the AEI Grant No. PID2021-127495NB I00 funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future.

Safe wastewater reuse in agriculture. Emerging contaminants and risk assessment

[SPA] El objetivo principal de la tesis es abordar de manera integrada los riesgos asociados a la utilización de aguas regeneradas en agricultura. En concreto se realizará una evaluación exhaustiva de la presencia, persistencia y acumulación de los denominados contaminantes de preocupación emergente en el sistema agua-suelo-planta. Para ello, se seleccionarán cultivos reales de alto interés comercial, diferentes condiciones de trabajo (sistemas de riego, tipo de sustratos, etc.), y se propondrán protocolos de análisis específicos que permitirán evaluar la calidad de los cultivos. Los resultados obtenidos, junto con protocolos adicionales para estudios microbiológicos y la valoración de efectos toxicológicos a corto y largo plazo, permitirán prever futuros escenarios de riesgo y evitar problemas en el complejo suelo-planta, garantizando una producción agrícola de alta calidad, protegiendo además la salud humana. [ENG] The main objective of this thesis is to address the risks associated with the use of reclaimed water in agriculture in an integrated manner. Particularly, a comprehensive assessment of the presence, persistence and accumulation of the so-called pollutants of emerging concern in the water-soil-plant system will be carried out. For this purpose, real crops of high commercial interest, different working conditions (irrigation systems, type of substrates, etc.) will be selected, and specific analysis protocols will be proposed to assess the quality of the crops. The results obtained, together with additional protocols for microbiological studies and the evaluation of short- and long-term toxicological effects, will help to foresee future risk scenarios, and avoid problems in the soil-plant complex, guaranteeing high-quality agricultural production while protecting human health.Esta tesis se desarrolla en el marco del proyecto RIS3MUR REUSAGUA, financiado por la Consejería de Empresa, Industria y Portavocía de la Región de Murcia, que se desarrolla en el marco del Programa Operativo Feder 2014-2020, y en el que se encuentran involucradas las siguientes entidades: CEBAS-CSIC, Imida, Esamur, UMU, UPCT, Cetenma, Azud, Hidrogea y Emuasa. El doctorando se encuentra financiado por un contrato predoctoral de la Fundación Séneca. Comunidad Autónoma de la Región de Murcia

Results from Bottom Trawl Survey on Flemish Cap of June-July 2017

A stratified random bottom trawl survey on Flemish Cap was carried out from June 16th to July 15th 2017. The area surveyed was extended up to depths of 800 fathoms (1460 meters) following the same procedures as in previous years and 181 fishing stations planned. The survey was carried out by the R/V Vizconde de Eza with the usual survey gear (Lofoten). A total of 181 valid hauls were made by the vessel R/V Vizconde de Eza, 120 up to 730 meters depth and 61 up to 1460 meters. Survey results including abundance indices of the main commercial species and age distributions for American plaice, Greenland halibut, roughhead grenadier and shrimp are presented. Cod and redfish age distributions are not available for 2017 due to administrative problems. The general indexes for this year are estimated taken into account the traditional swept area (strata 1-19, up to depths of 730 m.) and the total area surveyed (strata 1-34, up to depths of 1460 m.).Versión del editor

Magnetic Dynamo Caused by Axions in Neutron Stars

The coupling between axions and photons modifies Maxwell’s equations, introducing a dynamo term in the magnetic induction equation. In neutron stars, for critical values of the axion decay constant and axion mass, the magnetic dynamo mechanism increases the total magnetic energy of the star. We show that this generates substantial internal heating due to enhanced dissipation of crustal electric currents. These mechanisms would lead magnetized neutron stars to increase their magnetic energy and thermal luminosity by several orders of magnitude, in contrast to observations of thermally emitting neutron stars. To prevent the activation of the dynamo, bounds on the allowed axion parameter space can be derived.F. A., P. D. L., and A. M. are supported by the Australian Research Council (ARC) Centre of Excellence for Gravitational Wave Discovery (OzGrav), through Project No. CE170100004. P. D. L. is supported through ARC Discovery Project No. DP220101610. J. A. P. acknowledges support by the Generalitat Valenciana (PROMETEO/2019/071) and AEI Grant No. PID2021-127495NB-I00

Magnetic dynamo caused by axions in neutron stars

The coupling between axions and photons modifies Maxwell's equations, introducing a dynamo term in the magnetic induction equation. In neutron stars, for critical values of the axion decay constant and axion mass, the magnetic dynamo mechanism increases the total magnetic energy of the star. We show that this generates substantial internal heating due to enhanced dissipation of crustal electric currents. These mechanisms would lead magnetized neutron stars to increase their magnetic energy and thermal luminosity by several orders of magnitude, in contrast to observations of thermally-emitting neutron stars. To prevent the activation of the dynamo, bounds on the allowed axion parameter space can be derived.Comment: 5 pages, 2 figures, 1 table + Supplemental Materia

Dynamical and temporal characterization of the total ozone column over Spain

As the ozone is one of the most relevant variables in the climate system, to get further in its long-term characterization is a critical issue. In this study, measurements of total ozone column (TOC) from five well-calibrated Brewer spectrophotometers placed in the Iberian Peninsula are analyzed. The temporal trend rate for TOC is +9.3 DU per decade for the period 1993–2012 in Central Iberian Peninsula. However, the low TOC levels during 2011 and 2012 over the study region notably reduce this rate. Empirical linear relationships are established between TOC and pressure, height, and temperature of the tropopause. The linear fits showed seasonal and latitudinal dependence, with stronger relationships during winter and spring. Events with the presence of a double tropopause (DT) are proved to be characteristic of the study region. The decrease in TOC levels when these anomalous events occur is quantified around 10 % in winter and spring with respect to the usual cases with a single tropopause. The total weight of the DT events with respect to the annual values is about 20 %, with a negligible occurrence in summer and autumn and being latitudinal-dependent. The North Atlantic Oscillation (NAO) index explains 30 % of the total ozone variability in winter. The DT events are found to be more frequent during phases with positive NAO.This work was partially supported the Ministerio de Ciencia e Innovación through project CGL2011-29921-C02-01