555 research outputs found

    Ionospheric Precipitation of Particles in the first 6D Vlasiator run

    Get PDF
    One of the most noticeable effects of solar–terrestrial physics is the aurora which regularly appears in the polar regions. This polar light is the result of the excitation of atmospheric species by charged particles originating from the solar wind and magnetosphere that enter the Earth’s atmosphere, which are called precipitating particles. We present the first results on auroral proton precipitation into the ionosphere using a global 3-dimensional simulation of near-Earth space plasma with the Vlasiator hybrid-Vlasov model, driven with a southward interplanetary magnetic field and steady solar wind parameters. The hybrid-Vlasov approach describes ions through their velocity distribution function in phase space (3-dimensional ordinary space and 3-dimensional velocity space), while electrons are represented by a massless charge-neutralizing fluid. Vlasiator is a global model describing the whole region of near-Earth space including the Earth’s magnetosphere (whole dayside and part of the magnetotail), the magnetosheath, as well as the foreshock region and some solar wind. The precipitating proton differential number fluxes for this run are determined from the proton phase-space density contained within the bounce loss-cone, which is set at a constant angle of 10 degrees everywhere. To determine the precipitation of particles at ionospheric altitudes (in this case a height of 110 km above the Earth’s surface), we trace magnetic field lines from the ionosphere to the inner boundary of the Vlasiator domain using the Tsyganenko model. With this, we obtain a magnetic local time–geomagnetic latitude map of differential number flux of precipitating protons in 9 energy bins between 0.5 and 50 keV. From the differential number flux, proton integral energy fluxes and mean energies can be obtained. The integral energy fluxes in the Vlasiator run are then compared to data of the Precipitation Electron/Proton Spectrometer (SSJ) instrument of the Defense Meteorological Satellite Program (DMSP) for several satellite overpasses during events with similar solar wind conditions as in the Vlasiator run. The SSJ instrument bins proton energies between 0.03 and 30 keV. Typical values of the total integral energy flux are between 5 · 10^6 and 5 · 10^7 keV cm−2 s−1 sr−1 in the cusp and between 1 · 10^6 and 3 · 10^7 keV cm−2 s−1 sr−1 in the evening sector for both Vlasiator and DMSP, although DMSP fluxes can locally be up to an order of magnitude higher. Additionally, global precipitation patterns in Vlasiator are compared to Ovation Prime, which is an empirical model based on data from DMSP which can be used to forecast precipitation of auroral electrons and protons. Although Ovation Prime shows a much wider cusp region compared to Vlasiator, both show similar maximum integral energy fluxes around 1 to 2 · 10^7 keV cm−2 s−1 sr−1 in the cusp region, and between 3 · 10^6 and 5 · 10^7 keV cm−2 s−1 sr−1 in the nightside oval

    Digital peer feedback to improve students' learning

    Get PDF

    Nutrition in an ethnically diverse society : what are some of the key challenges?

    Get PDF
    The role of nutrition is especially important in certain ‘lifestyle’ diseases that impact disproportionately on ethnic minority populations. The aim of this paper is to review the evidence of risk, health outcomes and interventions for certain diseases that affect the UK’s largest ethnic minority group (South Asians) in order to help professionals better address the needs of this diverse population. Research evidence is presented on factors influencing access to services by ethnic minority populations and the changing UK policy background for public health and preventive care. The available research base on obesity, diabetes and CVD is discussed. Conditions such as type 2 diabetes, which are more prevalent among the South Asian population, are associated with poorer health outcomes and appear to exhibit links to diet and nutrition that start in childhood or even before birth; all making preventive care important. Obesity is a major risk factor and it appears that BMI thresholds may need to be lower for South Asians. Targeted interventions to improve diet and outcomes in the South Asian population also appear promising. Recent moves to promote access to evidence of ethnicity and health and to improve the cultural competence of organisations are discussed. Health professionals will increasingly need to promote lifestyle changes in a manner that meets the needs of a diverse population in order to address future public health challenges. Nutritionists and other professionals will need to ensure that interventions are culturally appropriate and involve engagement with extended family members and communities

    Towards grading automation of open questions using machine learning

    Get PDF

    Kwaliteitszorg binnen de bedrijfsmechanisatie

    Get PDF

    Kwaliteitszorg binnen de bedrijfsmechanisatie

    Get PDF

    Cursussen 1992

    Get PDF

    Networked Design Decisions in Balanced Life Cycles

    Get PDF
    Many decisions, both conscious and unconscious, have to be made during a product development process. In reaching a decision, it is essential to take the consequences of the different alternatives into consideration. To assess preconditions and consequences of decisions, an actor network can be used. An actor network is a combination of interrelated entities, representing multiple individuals and/or organizations. By adding characteristics to these actors and their relation, aspects like supply chain and life cycle issues can be addressed.\ud \ud This publication describes the basic building blocks of an actor network from a generic and abstract viewpoint. From these essential building blocks, the construction of the overall actor network is described. Examples are used from the field of content-packaging combinations, as well as aspects from life cycle assessments to illustrate the intended fundamental functionality. In the bigger picture, the use of the actor network in the context of product-packaging combinations aims at achieving lasting balance in product-packaging networks
    • …
    corecore