Polar cap arcs from the magnetosphere to the ionosphere: kinetic modelling and observations by Cluster and TIMED

On 1 April 2004 the GUVI imager onboard the TIMED spacecraft spots an isolated and elongated polar cap arc. About 20 min later, the Cluster satellites detect an isolated upflowing ion beam above the polar cap. Cluster observations show that the ions are accelerated upward by a quasi-stationary electric field. The field-aligned potential drop is estimated to about 700 V and the upflowing ions are accompanied by a tenuous population of isotropic protons with a temperature of about 500 eV. <br><br> The magnetic footpoints of the ion outflows observed by Cluster are situated in the prolongation of the polar cap arc observed by TIMED GUVI. The upflowing ion beam and the polar cap arc may be different signatures of the same phenomenon, as suggested by a recent statistical study of polar cap ion beams using Cluster data. <br><br> We use Cluster observations at high altitude as input to a quasi-stationary magnetosphere-ionosphere (MI) coupling model. Using a Knight-type current-voltage relationship and the current continuity at the topside ionosphere, the model computes the energy spectrum of precipitating electrons at the top of the ionosphere corresponding to the generator electric field observed by Cluster. The MI coupling model provides a field-aligned potential drop in agreement with Cluster observations of upflowing ions and a spatial scale of the polar cap arc consistent with the optical observations by TIMED. The computed energy spectrum of the precipitating electrons is used as input to the Trans4 ionospheric transport code. This 1-D model, based on Boltzmann's kinetic formalism, takes into account ionospheric processes such as photoionization and electron/proton precipitation, and computes the optical and UV emissions due to precipitating electrons. The emission rates provided by the Trans4 code are compared to the optical observations by TIMED. They are similar in size and intensity. Data and modelling results are consistent with the scenario of quasi-static acceleration of electrons that generate a polar cap arc as they precipitate in the ionosphere. The detailed observations of the acceleration region by Cluster and the large scale image of the polar cap arc provided by TIMED are two different features of the same phenomenon. Combined together, they bring new light on the configuration of the high-latitude magnetosphere during prolonged periods of Northward IMF. Possible implications of the modelling results for optical observations of polar cap arcs are also discussed

Trimetric Imaging of the Martian Ionosphere Using a CubeSat Constellation

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143020/1/6.2017-5252.pd

GPR, a ground‐penetrating radar for the Netlander mission

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95485/1/jgre1563.pd

Offset Credits in the EU ETS: A Quantile Estimation of Firm-Level Transaction Costs

International offset certificates trade at lower prices than European Union Allowances (EUAs), although they are substitutes within the EU Emissions Trading System (EU ETS) for CO2. Firms therefore had a strong incentive to use the cheaper certificates. However, a considerable number of firms did not use their allowed offset quota and, by doing so, seemingly forwent profits. While most of the literature on emissions trading evaluates the efficiency of regulation in a frictionless world, in practice firms incur costs when complying with regulation. In order to assess the relevance of managerial and information-related transaction costs, this study examines the use of international offset credits in the EU ETS. It establishes a model of firm decision under fixed entry costs and estimates the size of transaction costs rationalizing firm behavior using semi-parametric binary quantile regressions. Comparing binary quantile results with probit estimates shows that high average transaction cost result from a strongly skewed underlying distribution. I find that for most firms the bulk of transaction costs stems from participation in the EU ETS in general, rather than additional participation in the offset trade

Three‐dimensional study of Mars upper thermosphere/ionosphere and hot oxygen corona: 2. Solar cycle, seasonal variations, and evolution over history

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95238/1/jgre2686.pd

The cost of mapping trachoma: data from the Global Trachoma Mapping Project

Background: The Global Trachoma Mapping Project (GTMP) was implemented with the aim of completing the baseline map of trachoma globally. Over 2.6 million people were examined in 1,546 districts across 29 countries between December 2012 and January 2016. The aim of the analysis was to estimate the unit cost and to identify the key cost drivers of trachoma prevalence surveys conducted as part of GTMP. Methodology and principal findings: In-country and global support costs were obtained using GTMP financial records. In-country expenditure was analysed for 1,164 districts across 17 countries. The mean survey cost was $13,113 per district [median:$11,675; IQR=$8,365-$14,618], $17,548 per evaluation unit [median:$15,839; IQR=$10,773-$19,915],$692 per cluster [median:$625; IQR=$452-$847] and $6.0 per person screened [median:$4.9; IQR=$3.7-$7.9]. Survey unit costs varied substantially across settings, and were driven by parameters such as geographic location, demographic characteristics, seasonal effects, and local operational constraints. Analysis by activities showed that fieldwork constituted the largest share of in-country survey costs (73.69%), followed by training of survey teams (11.01%). The main drivers of in-country survey costs were personnel (49.49%) and transportation (43.56%). Global support expenditure for all surveyed districts amounted to $5.1m, which included grant management, epidemiological support, and data stewardship. Conclusion: This study provides the most extensive analysis of the cost of conducting trachoma prevalence surveys to date. The findings can aid planning and budgeting for future trachoma surveys required to measure the impact of trachoma elimination activities. Furthermore, the results of this study can also be used as a cost basis for other disease mapping programmes, where disease or context-specific survey cost data are not available