Energy release in the solar atmosphere from a stream of infalling prominence debris

Recent high-resolution and high-cadence EUV imaging has revealed a new phenomenon, impacting prominence debris, where prominence material from failed or partial eruptions can impact the lower atmosphere, releasing energy. We report a clear example of energy release and EUV brightening due to infalling prominence debris that occurred on 2011 September 7-8. The initial eruption of material was associated with an X1.8-class flare from AR11283, occurring at 22:30 UT on 2011 September 7. Subsequently, a semi-continuous stream of this material returned to the solar surface with a velocity v > 150 km/s, impacting a region remote from the original active region between 00:20 - 00:40 UT on 2011 September 8. Using SDO/AIA, the differential emission measure of the plasma was estimated throughout this brightening event. We found that the radiated energy of the impacted plasma was L_rad ~10^27 ergs, while the thermal energy peaked at ~10^28 ergs. From this we were able to determine the mass content of the debris to be in the range 2x10^14 < m < 2x10^15 g. Given typical promimence masses, the likely debris mass is towards the lower end of this range. This clear example of a prominence debris event shows that significant energy release takes place during these events, and that such impacts may be used as a novel diagnostic tool for investigating prominence material properties.Comment: Accepted by AstroPhysical Journal Letters, 6 pages, 5 figure

The Foraging and Habitat Ecology of Black Terns in Maine

The population of Black Terns in Maine is small and factors related to the ecology of this species’ foraging and habitat ecology might limit population growth and recovery. The objectives were to (1) determine if diet and provisioning rates are limiting chick growth, (2) identify and rank suitable habitat in Maine, and (3) determine if precipitation patterns and water level dynamics are limiting in Maine. I compared growth rates of chicks in 1998-2000 in Maine to rates from other studies, determined the influence of colony, year, and diet on growth rates and food deliveries and used an energetics model to determine the sensitivity of growth rates to feeding parameters. To identify potential wetland habitat, I used a Geographic Information System analysis of National Wetlands Inventory data from Maine based on the following criteria: wetland complexes were \u3e5 ha total area with \u3e1 ha open water and contained semi-permanently flooded emergent wetland. To assess effects of flooding, I determined the probability of occurrence for 3 levels (low, moderate, and catastrophic)?of nest losses associated with flooding, based on nest loss data and stream gauge and precipitation data for 1960-1999. Growth rates of Black Tern chicks in Maine ( ? = 4.46 g/d) were similar to other studies (range 4.18-5.18 g/d) and varied with hatch order and brood, but not year or colony. Third-hatched chicks (of 3) grew most slowly ( ? = 4.15 g/d) but at greater rates than one reported estimate (3.32 g/d) for starved chicks. Patterns of food deliveries were complex. The ratio of fish to insects in the diet ranged from 3.4-13.3, and total delivery rates varied widely (9.1-23.7 items/brood-hr), but there was no evidence that growth rates differed among diets. Weight change in chicks was best predicted by delivery rates of large fish, large and small insects, and temperature; however, modeling indicated that growth rates were most sensitive to rates of large insect delivery. My results indicate that diet type did not influence growth rates of chicks at the observed rates of delivery, and overall there was no evidence that food resources limited fledging rates in Black Terns in Maine. I identified 730 potential colony sites for Black Terns in Maine. Potential sites ranged in size from 5-30,864 ha ( ? = 425 ha) and had 0.04-228 ha of semipermanently flooded emergent wetland. However, only 51 sites were classified as high potential sites (\u3e20 ha of semi-permanently flooded emergent wetland) The availability of potential sites does not appear to be limiting the population of Black Terns in Maine, but these sites should be ground surveyed because wetland classification data may be out-dated or too coarse-grained. Moderate flooding events have the potential to cause the greatest long-term effect on nesting success in Maine because of a high frequency of occurrence (38% of years)?and \u3e50% nest loss in the largest colony and 36% in other colonies. Small flooding events occurred often (70% of years), but resulted in few nest losses and catastrophic flooding events caused extensive nest losses (\u3e94% in the largest colony and 36% in other colonies) but occurred in only 13% of years

Supported Programming for Beginning Developers

Testing code is important, but writing test cases can be time consuming, particularly for beginning programmers who are already struggling to write an implementation. We present TestBuilder, a system for test case generation which uses an SMT solver to generate inputs to reach specified lines in a function, and asks the user what the expected outputs would be for those inputs. The resulting test cases check the correctness of the output, rather than merely ensuring the code does not crash. Further, by querying the user for expectations, TestBuilder encourages the programmer to think about what their code ought to do, rather than assuming that whatever it does is correct. We demonstrate, using mutation testing of student projects, that tests generated by TestBuilder perform better than merely compiling the code using Python’s built-in compile function, although they underperform the tests students write when required to achieve 100% test coverage

The spiral wind-up and dissipation of vorticity and a passive scalar in a strained planar vortex

Copyright © 1999 Cambridge University Press. Published version reproduced with the permission of the publisher.The response of a Gaussian vortex to a weak time-dependent external strain field is studied numerically. The cases of an impulsive strain, an on–off step function, and a continuous random strain are considered. Transfers of enstrophy between mean and azimuthal components are observed, and the results are compared with an analogous passive scalar model and with Kida's elliptical vortex model. A ‘rebound’ phenomenon is seen: after enstrophy is transferred from mean to azimuthal component by the external straining field, there is a subsequent transfer of enstrophy back from the azimuthal component to the mean. Analytical support is given for this phenomenon using Lundgren's asymptotic formulation of the spiral wind-up of vorticity. Finally the decay of the vortex under a continuous random external strain is studied numerically and compared with the passive scalar model. The vorticity distribution decays more slowly than the scalar because of the rebound phenomenon

Nonlinear equilibration of a dynamo in a smooth helical flow

Copyright © 1997 Cambridge University Press. Published version reproduced with the permission of the publisher.We investigate the nonlinear equilibration of magnetic fields in a smooth helical flow at large Reynolds number Re and magnetic Reynolds number Rm with Re >> Rm >> 1. We start with a smooth spiral Couette flow driven by boundary conditions. Such flows act as dynamos, that is are unstable to growing magnetic fields; here we disregard purely hydrodynamic instabilities such as Taylor-Couette modes. The dominant feedback from a magnetic field mode is only on the mean flow and this yields a simplified `mean-flow system' consisting of one magnetic mode and the mean flow, which we solve numerically. We also obtain the asymptotic structure of the equilibrated fields for weakly and strongly nonlinear regimes. In particular the field tends to concentrate in a cylindrical shell where all stretching and differential rotation is suppressed by the Lorentz force, and the fluid is in solid-body motion. This shell is bounded by thin diffusive layers where the stretching that maintains the field against diffusive decay is dominant

The spiral wind-up of vorticity in an inviscid planar vortex

Copyright © 1998 Cambridge University Press. Published version reproduced with the permission of the publisher.The relaxation of a smooth two-dimensional vortex to axisymmetry, also known as `axisymmetrization', is studied asymptotically and numerically. The vortex is perturbed at t = 0 and differential rotation leads to the wind-up of vorticity fluctuations to forma spiral. It is shown that for infinite Reynolds number and in the linear approximation, the vorticity distribution tends to axisymmetry in a weak or coarse-grained sense: when the vorticity field is integrated against a smooth test function the result decays asymptotically as t−λ with λ = 1 + (n2 + 8)1/2, where n is the azimuthal wavenumber of the perturbation and n ≥1. The far-field stream function of the perturbation decays with the same exponent. To obtain these results the paper develops a complete asymptotic picture of the linear evolution of vorticity fluctuations for large times t, which is based on that of Lundgren (1982)

Student-led success: Improving attendance and learning at Fourth Hour review sessions

This research continues the work of Gilbert et al. [1] by translating the “Fourth Hour” review session materials from Java to Python, keeping the focus on common misconceptions in the literature, continuing to use Peer Instruction (PI), and addressing two issues in the previous study: low attendance and short-term learning outcomes during the session. [2] The “Fourth Hour” is a review session designed to support students taking CS1 who may have missed class or need to review the previous week’s material. This review session is an hour long and is offered twice a week with the same material so more students can fit it into their schedules. In Gilbert et al’s study, attendance was too low for the results to be statistically significant. This new study attempts to address this issue by implementing in-class weekly assessments with retakes that will be used to improve attendance. This study also measures learning gains during the session by measuring the accuracy of the responses to the given PI questions to determine whether students who attend are actually learning the material being presented

Der junge Lukács als Diagnostiker der Krise. Subjektivismus und das Problem der Form

This paper argues that the work of the young Lukács can be read as a wide-ranging mediation on what I am labelling ›the crisis of subjectivism‹. Reading Lukács this way allows us to see important continuities between his pre-Marxist and Marxist period. Most significantly, it allows us to see how positing the proletariat as a ›subject-object‹ of history and developing a crisis diagnosis of bourgeois society, allowed Lukács to bring the fruits of his earlier intellectual labour under conceptual control.Das Werk des jungen Lukács wird im vorliegenden Beitrag als umfassende Verhandlung einer ›Krise des Subjektivismus‹ gelesen. Diese Lesart lässt wichtige Verbindungslinien zwischen Lukács̕ vormarxistischer und seiner marxistischen Phase erkennen. Vor allem jedoch wird deutlich, auf welche Weise die Positionierung des Proletariats als ›Subjekt-Objekt‹ der Geschichte und die Entwicklung einer Krisendiagnose der bürgerlichen Gesellschaft es Lukács ermöglichten, die Früchte seiner früheren Gedankenarbeit konzeptuell einzuhegen