Svestka's Research: Then and Now

Zdenek Svestka's research work influenced many fields of solar physics, especially in the area of flare research. In this article I take five of the areas that particularly interested him and assess them in a "then and now" style. His insights in each case were quite sound, although of course in the modern era we have learned things that he could not readily have envisioned. His own views about his research life have been published recently in this journal, to which he contributed so much, and his memoir contains much additional scientific and personal information (Svestka, 2010).Comment: Invited review for "Solar and Stellar Flares," a conference in honour of Prof. Zden\v{e}k \v{S}vestka, Prague, June 23-27, 2014. This is a contribution to a Topical Issue in Solar Physics, based on the presentations at this meeting (Editors Lyndsay Fletcher and Petr Heinzel

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

Grid and method of manufacturing such grid

The invention relates to a slit pattern, to be referred to as grid, comprising a plurality of laminations arranged parallel, which, to form a slit pattern, are maintained in spaced relation by distancing elements, to be referred to as spacers, arranged between the laminations. The invention further relates to a method for the manufacture of such grid.Delft University of Technolog

Coronal interconnection of two active regions observed in 3.5–5.5 keV X-rays

Using HXIS data, we have studied further development of the coronal arch extending towards SE above the active region (AR) No.17255 in November 1980. The disappearance of that arch was followed by the appearance of another arch-like structure towards SW. We have studied the development of the new structure and classified it as an arch interconnecting AR 17255 with AR 17251, which was 30° to the west. We estimate physical characteristics of this interconnection and compare them with Skylab data and the earlier arches

Coronal interconnection of two active regions observed in 3.5–5.5 keV X-rays

Using HXIS data, we have studied further development of the coronal arch extending towards SE above the active region (AR) No.17255 in November 1980. The disappearance of that arch was followed by the appearance of another arch-like structure towards SW. We have studied the development of the new structure and classified it as an arch interconnecting AR 17255 with AR 17251, which was 30° to the west. We estimate physical characteristics of this interconnection and compare them with Skylab data and the earlier arches

A measurement of auroral electrons in the 1–10 MeV range

Particle fluxes have been measured by means of shielded Geiger-Müller telescopes mounted m a rocket, which was launched from ESRANGE(Kiruna) into a diffuse aurora. The analysis of the dependence of the counting rates on altitude indicates that a weak flux of energetic electrons, 1–10 MeV, has been detected

Evaluation of methods to assess push and pull forces in a contruction task

The objective of the present study was to determine the validity of methods to assess push/pull forces exerted in a construction task. Forces assessed using a hand-held digital force gauge were compared to those obtained using a highly accurate measuring frame. No significant differences were found between the methods, except for peak push forces, for which the forces assessed with the force gauge were significantly lower than those assessed with the measuring frame. When the construction task was reproduced close to the actual workplace by simulation against a fixed object using the force gauge, all exerted forces on the force gauge were significantly lower than those on the measuring frame, except for mean pull forces. When self-reports were compared to the exerted forces on the measuring frame, the construction workers overestimated the exerted push/pull forces by 50%. In conclusion, when applied for direct measurements, the force gauge can be used to validly assess push/pull forces at the workplace

The effectiveness of a construction worksite prevention program on work ability, health, and sick leave: results from a cluster randomized controlled trial

Objective This study aimed to investigate the effectiveness of a prevention program on work ability, health, and sick leave targeted at construction worksites. Methods A total of 15 departments (N=297 workers) from 6 construction companies participated in this cluster randomized controlled trial and were randomly allocated to the intervention (8 departments; N=171 workers) or control (7 departments; N=122 workers) group. The intervention consisted of two individual training sessions with a physical therapist aimed at lowering the physical workload, a rest-break tool to improve the balance between work and recovery, and two empowerment training sessions to increase the worker's influence at the worksite. Data on workability, physical and mental health status, and musculoskeletal symptoms were collected at baseline, and at 3, 6, and 12 months follow-up. Sick leave data were obtained from the companies. Results Overall, no differences in work ability [beta 0.02, 95% confidence interval (95% CI) -0.34-0.37] or physical and mental health status (beta -0.04, 95% CI -1.43-1.35, and beta 0.80 95% CI -0.51-2.11, respectively) were found between the intervention and control group. The intervention showed an overall decline in musculoskeletal symptoms (ranging from OR 0.68, 95% CI 0.34-1.33, to OR 0.86, 95% CI 0.47-1.57) and long-term sick leave (OR 0.44, 95% CI 0.13-1.26) among construction workers. Both reductions were not statistically significant. Conclusion The prevention program seemed to result in a beneficial but not statistically significant decline in the prevalence of musculoskeletal symptoms and long-term sick leave among construction workers, but showed no effects with regard to work ability, physical health, and mental healt

Electron-ion and ion-ion reaction rate coefficients at low altitudes during a PCA event

Based on experimental data from several ESRO PCA rocket flights some considerations are presented regarding the mean values of the electron-ion dissociative recombination coefficient (αd) and the ion-ion neutralization coefficient (αi). The estimates yield values for αd = 10−5 cm3 sec−1 for heights between 60 and 67 km. The data indicate that αi is smaller than αd by a factor of 100