An Observational Overview of Solar Flares

We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations.Comment: This is an article for a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011

Beam-induced backgrounds measured in the ATLAS detector during local gas injection into the LHC beam vacuum

Inelastic beam-gas collisions at the Large Hadron Collider (LHC), within a few hundred metres of the ATLAS experiment, are known to give the dominant contribution to beam backgrounds. These are monitored by ATLAS with a dedicated Beam Conditions Monitor (BCM) and with the rate of fake jets in the calorimeters. These two methods are complementary since the BCM probes backgrounds just around the beam pipe while fake jets are observed at radii of up to several metres. In order to quantify the correlation between the residual gas density in the LHC beam vacuum and the experimental backgrounds recorded by ATLAS, several dedicated tests were performed during LHC Run 2. Local pressure bumps, with a gas density several orders of magnitude higher than during normal operation, were introduced at different locations. The changes of beam-related backgrounds, seen in ATLAS, are correlated with the local pressure variation. In addition the rates of beam-gas events are estimated from the pressure measurements and pressure bump profiles obtained from calculations. Using these rates, the efficiency of the ATLAS beam background monitors to detect beam-gas events is derived as a function of distance from the interaction point. These efficiencies and characteristic distributions of fake jets from the beam backgrounds are found to be in good agreement with results of beam-gas simulations performed with theFluka Monte Carlo programme

Analysis of alfalfa leafcutter bee (Megachile rotundata) provisions pre-and post-sterilization with propylene oxide

Provisions of Megachile rotundata were analyzed for their physical, chemical and microbial properties prior to and following fumigation with propylene oxide. The effects of treated and untreated provisions on larval development and susceptibility to Ascosphaera aggregata were also studied. Bacteria, yeasts and filamentous fungi averaged 1.3 x 103, 1.5 x 10 2 and 7.5 x 103 colony-forming-units g-1, respectively. Fumigation with propylene oxide for 24 h at concentrations of 0.6 and 1.2%, but not 0.1%, effectively sterilized provisions. Untreated provisions consisted of 18.1% water, 56.8% nectar and 25.1 % pollen with a pH of 4.1. The sugar content was 65.9% and was comprised of fructose (48.1%), glucose (43.6%), sucrose (1.4%) and turanose/palatinose (1.8%). Pollen contained 6% protein. Pollen was not stratified within provisions and Medicago sativa was the most prevalent taxon (66.2%). Propylene oxide treatment had no effect on the protein content or distribution of pollen within provisions but increased the pH by 0.2-0.5. Total sugars and quantities of fructose and glucose were reduced by 3.2, 10.4 and 8.7%, respectively, whereas the caloric content of treated provisions was 1.6% greater than the control treatment. Detoxification under vacuum for 120 h reduced the water content of provisions by 40.3%. Eggs of M rotundata did not survive when placed on provisions detoxified under vacuum for 24 h post-fumigation. On provisions detoxified for 120 h, there were no differences in mortality between larvae reared on sterilized, artificial and non-sterilized provisions, but time to prepupation was delayed relative to the non-sterilized treatment. The mean mortalities of larvae inoculated with A aggregata were 98.0, 97.8 and 27.4%, respectively on artificial, sterilized and non-sterilized provisions