A self-consistent determination of the temperature profile and the magnetic field geometry in winds of late-type stars

Cool giant and supergiant stars generally present low velocity winds with high mass loss rates. Several models have been proposed to explain the acceleration process of these winds. Although dust is known to be present in these objects, the radiation pressure on these particles is uneffective in reproducing the observed physical parameters of the wind. The most promising acceleration mechanism cited in the literature is the transference of momentum and energy from Alfven waves to the gas. Usually, these models consider the wind to be isothermal. We present a stellar wind model in which the Alfven waves are used as the main acceleration mechanism, and determine the temperature profile by solving the energy equation taking into account both the radiative losses and the wave heating. We also determine self-consistently the magnetic field geometry as the result of the competition between the magnetic field and the thermal pressures gradient. As main result, we show that the magnetic geometry present a super-radial index in the region where the gas pressure is increasing. However, this super-radial index is greater than that observed for the solar corona.Comment: Accepted for publication in Space Science Reviews. Presented at the World Space Environment Forum 2005, Austria. 8 pages, 2 figure

Origins of the Ambient Solar Wind: Implications for Space Weather

The Sun's outer atmosphere is heated to temperatures of millions of degrees, and solar plasma flows out into interplanetary space at supersonic speeds. This paper reviews our current understanding of these interrelated problems: coronal heating and the acceleration of the ambient solar wind. We also discuss where the community stands in its ability to forecast how variations in the solar wind (i.e., fast and slow wind streams) impact the Earth. Although the last few decades have seen significant progress in observations and modeling, we still do not have a complete understanding of the relevant physical processes, nor do we have a quantitatively precise census of which coronal structures contribute to specific types of solar wind. Fast streams are known to be connected to the central regions of large coronal holes. Slow streams, however, appear to come from a wide range of sources, including streamers, pseudostreamers, coronal loops, active regions, and coronal hole boundaries. Complicating our understanding even more is the fact that processes such as turbulence, stream-stream interactions, and Coulomb collisions can make it difficult to unambiguously map a parcel measured at 1 AU back down to its coronal source. We also review recent progress -- in theoretical modeling, observational data analysis, and forecasting techniques that sit at the interface between data and theory -- that gives us hope that the above problems are indeed solvable.Comment: Accepted for publication in Space Science Reviews. Special issue connected with a 2016 ISSI workshop on "The Scientific Foundations of Space Weather." 44 pages, 9 figure

Heliolatitude and time variations of solar wind structure from in situ measurements and interplanetary scintillation observations

The 3D structure of solar wind and its evolution in time is needed for heliospheric modeling and interpretation of energetic neutral atoms observations. We present a model to retrieve the solar wind structure in heliolatitude and time using all available and complementary data sources. We determine the heliolatitude structure of solar wind speed on a yearly time grid over the past 1.5 solar cycles based on remote-sensing observations of interplanetary scintillations, in situ out-of-ecliptic measurements from Ulysses, and in situ in-ecliptic measurements from the OMNI-2 database. Since the in situ information on the solar wind density structure out of ecliptic is not available apart from the Ulysses data, we derive correlation formulae between solar wind speed and density and use the information on the solar wind speed from interplanetary scintillation observations to retrieve the 3D structure of solar wind density. With the variations of solar wind density and speed in time and heliolatitude available we calculate variations in solar wind flux, dynamic pressure and charge exchange rate in the approximation of stationary H atoms.Comment: Accepted for publication in Solar Physic

Solar parameters for modeling interplanetary background

The goal of the Fully Online Datacenter of Ultraviolet Emissions (FONDUE) Working Team of the International Space Science Institute in Bern, Switzerland, was to establish a common calibration of various UV and EUV heliospheric observations, both spectroscopic and photometric. Realization of this goal required an up-to-date model of spatial distribution of neutral interstellar hydrogen in the heliosphere, and to that end, a credible model of the radiation pressure and ionization processes was needed. This chapter describes the solar factors shaping the distribution of neutral interstellar H in the heliosphere. Presented are the solar Lyman-alpha flux and the solar Lyman-alpha resonant radiation pressure force acting on neutral H atoms in the heliosphere, solar EUV radiation and the photoionization of heliospheric hydrogen, and their evolution in time and the still hypothetical variation with heliolatitude. Further, solar wind and its evolution with solar activity is presented in the context of the charge exchange ionization of heliospheric hydrogen, and in the context of dynamic pressure variations. Also the electron ionization and its variation with time, heliolatitude, and solar distance is presented. After a review of all of those topics, we present an interim model of solar wind and the other solar factors based on up-to-date in situ and remote sensing observations of solar wind. Results of this effort will further be utilised to improve on the model of solar wind evolution, which will be an invaluable asset in all heliospheric measurements, including, among others, the observations of Energetic Neutral Atoms by the Interstellar Boundary Explorer (IBEX).Comment: Chapter 2 in the planned "Cross-Calibration of Past and Present Far UV Spectra of Solar System Objects and the Heliosphere", ISSI Scientific Report No 12, ed. R.M. Bonnet, E. Quemerais, M. Snow, Springe

Large-Eddy Simulations of Magnetohydrodynamic Turbulence in Heliophysics and Astrophysics

We live in an age in which high-performance computing is transforming the way we do science. Previously intractable problems are now becoming accessible by means of increasingly realistic numerical simulations. One of the most enduring and most challenging of these problems is turbulence. Yet, despite these advances, the extreme parameter regimes encountered in space physics and astrophysics (as in atmospheric and oceanic physics) still preclude direct numerical simulation. Numerical models must take a Large Eddy Simulation (LES) approach, explicitly computing only a fraction of the active dynamical scales. The success of such an approach hinges on how well the model can represent the subgrid-scales (SGS) that are not explicitly resolved. In addition to the parameter regime, heliophysical and astrophysical applications must also face an equally daunting challenge: magnetism. The presence of magnetic fields in a turbulent, electrically conducting fluid flow can dramatically alter the coupling between large and small scales, with potentially profound implications for LES/SGS modeling. In this review article, we summarize the state of the art in LES modeling of turbulent magnetohydrodynamic (MHD) ows. After discussing the nature of MHD turbulence and the small-scale processes that give rise to energy dissipation, plasma heating, and magnetic reconnection, we consider how these processes may best be captured within an LES/SGS framework. We then consider several special applications in heliophysics and astrophysics, assessing triumphs, challenges,and future directions

Global Retinoblastoma Presentation and Analysis by National Income Level

Importance: Early diagnosis of retinoblastoma, the most common intraocular cancer, can save both a child's life and vision. However, anecdotal evidence suggests that many children across the world are diagnosed late. To our knowledge, the clinical presentation of retinoblastoma has never been assessed on a global scale. Objectives: To report the retinoblastoma stage at diagnosis in patients across the world during a single year, to investigate associations between clinical variables and national income level, and to investigate risk factors for advanced disease at diagnosis. Design, Setting, and Participants: A total of 278 retinoblastoma treatment centers were recruited from June 2017 through December 2018 to participate in a cross-sectional analysis of treatment-naive patients with retinoblastoma who were diagnosed in 2017. Main Outcomes and Measures: Age at presentation, proportion of familial history of retinoblastoma, and tumor stage and metastasis. Results: The cohort included 4351 new patients from 153 countries; the median age at diagnosis was 30.5 (interquartile range, 18.3-45.9) months, and 1976 patients (45.4) were female. Most patients (n = 3685 84.7%) were from low-and middle-income countries (LMICs). Globally, the most common indication for referral was leukocoria (n = 2638 62.8%), followed by strabismus (n = 429 10.2%) and proptosis (n = 309 7.4%). Patients from high-income countries (HICs) were diagnosed at a median age of 14.1 months, with 656 of 666 (98.5%) patients having intraocular retinoblastoma and 2 (0.3%) having metastasis. Patients from low-income countries were diagnosed at a median age of 30.5 months, with 256 of 521 (49.1%) having extraocular retinoblastoma and 94 of 498 (18.9%) having metastasis. Lower national income level was associated with older presentation age, higher proportion of locally advanced disease and distant metastasis, and smaller proportion of familial history of retinoblastoma. Advanced disease at diagnosis was more common in LMICs even after adjusting for age (odds ratio for low-income countries vs upper-middle-income countries and HICs, 17.92 95% CI, 12.94-24.80, and for lower-middle-income countries vs upper-middle-income countries and HICs, 5.74 95% CI, 4.30-7.68). Conclusions and Relevance: This study is estimated to have included more than half of all new retinoblastoma cases worldwide in 2017. Children from LMICs, where the main global retinoblastoma burden lies, presented at an older age with more advanced disease and demonstrated a smaller proportion of familial history of retinoblastoma, likely because many do not reach a childbearing age. Given that retinoblastoma is curable, these data are concerning and mandate intervention at national and international levels. Further studies are needed to investigate factors, other than age at presentation, that may be associated with advanced disease in LMICs. © 2020 American Medical Association. All rights reserved

Коррекция нарушений теплового баланса головного мозга в терапии и реабилитации пациентов с церебральной патологией

Temperature monitoring of the brain using radiothermometric technology allows you to assess the imbalance of the thermal balance of the brain, and the technique has shown the possibility and information content of its use in the diagnosis of cerebral lesions. In healthy individuals, at rest, the average temperature of the left (36.74 ± 0.37 ° C) and the right hemisphere (36.64 ± 0.32 ° C). In boxing athletes who received "planned" minor traumatic brain injuries after training sparring, the average temperature of the left (38.4 ± 0.28 ° C) and right temperature (38.2 ± 0.45 ° C), which is significantly elevated. Patients in chronic critical conditions showed a monotonous temperature distribution in the left (36.98 ± 0.18 ° C) and right hemispheres (36.88 ± 0.21 ° C). The temperature heterogeneity of the brain in this category of patients was less pronounced compared with healthy individuals, athletes after sports head injury.Поражения головного мозга весьма часто приводят к нарушениям общего и церебрального теплового баланса, играющим важную роль в патогенетических механизмах вторичных повреждений нейронов. Краниоцеребральная гипотермия позволяет купировать нарушения общего и церебрального термогомеостаза и проявляет выраженные нейропротективные эффекты, что позволяет рекомендовать её применение в составе лечебных и реабилитационных мероприятий. Краниоцеребральная гипотермия, по сравнению с методиками общего охлаждения организма, направлена в первую очередь на понижение температуры мозга, а не внутренних органов, то есть на достижение эффектов нейропротекции. Температурный мониторинг головного мозга с использованием радиотермометрических технологии позволяет оценить нарушения теплового баланса мозга, а методика показала возможность и информативность использования её в диагностике церебральных поражений. У здоровых лиц в покое значения усредненной температуры левого (36,74 ± 0,37°С) и правого полушария (36,64 ± 0,32°С). У спортсменов-боксеров, получивших «запланированные» легкие черепно-мозговые травмы после тренировочных спаррингов, значения усредненной температуры левого (38,4 ± 0,28°С) и правого (38,2 ± 0,45°С), что оказывается существенно повышенным. У пациентов в хронических критических состояниях выявлено монотонное распределение температуры в левом (36,98±0,18°С) и правом полушариях (36,88±0,21°С). Температурная гетерогенность мозга у данной категории пациентов была менее выражена по сравнению со здоровыми лицами, спортсменами после спортивной черепно-мозговой травмы