Modeling coronal magnetic field using spherical geometry: cases with several active regions

The magnetic fields in the solar atmosphere structure the plasma, store free magnetic energy and produce a wide variety of active solar phenomena, like flare and coronal mass ejections(CMEs). The distribution and strength of magnetic fields are routinely measured in the solar surface(photosphere). Therefore, there is considerable interest in accurately modeling the 3D structure of the coronal magnetic field using photospheric vector magnetograms. Knowledge of the 3D structure of magnetic field lines also help us to interpret other coronal observations, e.g., EUV images of the radiating coronal plasma. Nonlinear force-free field (NLFFF) models are thought to be viable tools for those task. Usually those models use Cartesian geometry. However, the spherical nature of the solar surface cannot be neglected when the field of view is large. In this work, we model the coronal magnetic field above multiple active regions using NLFFF extrapolation code using vector magnetograph data from the Synoptic Optical Long-term Investigations of the Sun survey (SOLIS)/ Vector Spectromagnetograph (VSM) as a boundary conditions. We compare projections of the resulting magnetic field lines solutions with their respective coronal EUV-images from the Atmospheric Imaging Assembly (SDO/AIA) observed on October 11, 2011 and November 13, 2012. This study has found that the NLFFF model in spherical geometry reconstructs the magnetic configurations for several active regions which agrees with observations. During October 11, 2011 observation, there are substantial number of trans-equatorial loops carrying electric current.Comment: 3 Figures, Submitted to Astrophysics and Space Science Journa

Antimicrobial Prescription Practices in the Veterinary Clinics of Addis Ababa, Ethiopia

The objectives of this study were to assess the adherence of animal health workers to rational antimicrobial prescription guidelines. Data were collected from personnel working in 25 clinics by using structured  questionnaires. The data included the methods of diagnosis and drug selection, the frequently prescribed antimicrobials, methods of prescription and the availability of drug information sources. The study showed that diagnosis was established on a presumptive basis; pen-strep and oxytetracycline were the frequently prescribed drugs and verbal instruction was a common form of prescription. Adherence to the rational guidelines was substantially low and the prescription practices favor the selection of drug resistant pathogens. Educational programs are needed to ensure the perceived benefit of animals and reduce the rates of emergence of drug resistant pathogens of animal origin in Ethiopia.Keywords: Addis Ababa, Animals, Antimicrobials, Health workers, Prescription

Prevalence and factors affecting work-related injury among workers engaged in Small and Medium-scale industries in Gondar wereda, North Gondor zone, Amhara Regional State, Ethiopia

No Abstract. The Ethiopian Journal of Health Development Vol. 21 (1) 2007: pp. 25-3

A survey of viral status on potatoes grown in Eritrea and in vitro virus elimination of a local variety ‘Tsaeda embaba’

Potato viruses are the major causes of yield loss and reduction in quality of seed tubers in Eritrea. A study was conducted to investigate the prevalence of viruses in potatoes (Solanum tuberosum L.)grown in Eritrea and to evaluate methods for their elimination. Leaf samples of two indigenous, (Tsaeda embaba and Keyih embaba) and three exotic varieties, (Ajiba, Spunta and Cosmos) were collected fromfields growing potatoes in Maekel and Debub Administrative Zones and tested using the double antibody sandwich enzyme linked immunosorbent assay (DAS ELISA) technique. Five of the six mostimportant potato viruses, PVX, PVY, PLRV, PVS and PVA, were detected in single and multiple infections. Virus elimination techniques were tested using in vitro plantlets of T. embaba establishedfrom field-grown tubers. Presence of PVX, PLRV and PVS was confirmed by ELISA test. The plantlets were then subjected to thermotherapy treatment for one and two weeks at 37oC. The treatment wassuccessful in eliminating only PLRV but failed to eliminate PVX and PVS. When meristem culture was combined with thermotherapy treatment for one week all three viruses PVX, PLRV and PVS wereeliminated with a success rate of 86, 83 and 100%, respectively

Magnetic Connectivity between Active Regions 10987, 10988, and 10989 by Means of Nonlinear Force-Free Field Extrapolation

Extrapolation codes for modelling the magnetic field in the corona in cartesian geometry do not take the curvature of the Sun's surface into account and can only be applied to relatively small areas, \textit{e.g.}, a single active region. We apply a method for nonlinear force-free coronal magnetic field modelling of photospheric vector magnetograms in spherical geometry which allows us to study the connectivity between multi-active regions. We use vector magnetograph data from the Synoptic Optical Long-term Investigations of the Sun survey (SOLIS)/Vector Spectromagnetograph(VSM) to model the coronal magnetic field, where we study three neighbouring magnetically connected active regions (ARs: 10987, 10988, 10989) observed on 28, 29, and 30 March 2008, respectively. We compare the magnetic field topologies and the magnetic energy densities and study the connectivities between the active regions(ARs). We have studied the time evolution of magnetic field over the period of three days and found no major changes in topologies as there was no major eruption event. From this study we have concluded that active regions are much more connected magnetically than the electric current.Comment: Solar Physic

Quantification of the Impact of Integrated Soil and Water Conservation Measures on Groundwater Availability in Mendae Catchment, Abraha We-Atsebaha, eastern Tigray, Ethiopia

The paper tries to evaluate the impact of integrated soil and water conservation measures on water availability in Mendae catchment (10.37 km2), which is located in the northeastern Tigray. Historical background of the catchment with respect to its land use was obtained from the local Bureau of Agriculture and Rural Development office. The hydrology of the area was characterized based on its land use, soil, slope, rainfall,  temperature, evapotranspiration, and runoff. Thornthwaite method and Thornthwaite soil-water balance model were used to determine potential and actual evapotranspiration, respectively. The mean annual runoff from the catchment was computed using runoff coefficient method. Before the intervention, the area was severely degraded and known with scarcity of water. Integrated soil and water conservation (physical and biological measures) was introduced to the area since 1993. The catchment is characterized by two rainy season and three dry seasons during the year. The rainy seasons in total have four months whereas the dry seasons comprises of eight months. The mean annual rainfall of the catchment is 565.8 mm, out of which rainy season accounts for 86.13% and the dry season for 13.87%. The rain that occurs with a very high concentration accounts 73.20 % of the mean annual rainfall of the catchment and this occur only in two months (July and August).The mean annual potential and actual evapotranspiration was found to be 832.67 mm and 405.61mm, respectively. The volume of runoff before and after the intervention was found to be 26.88 % and 17.19 % of the mean annual rainfall of the catchment, respectively. The groundwater recharge before and after the intervention was found to be 1.43 % and 19.04% of the mean annual rainfall of the catchment, respectively. The availability of groundwater has increased more than 10 times since 1993. Though the groundwater is being used for both complimentary and supplementary irrigation during the dry and rainy season, respectively, construction of additional physical conservation structures is suggested to further improve the groundwater availability in the area.Keywords: Groundwater, Mendae catchment, Surface runoff, Water balance, Tigray, Ethiopia