Why every observatory needs a disco ball

Commercial disco balls provide a safe, effective and instructive way of observing the Sun. We explore the optics of solar projections with disco balls, and find that while sunspot observations are challenging, the solar disk and its changes during eclipses are easy and fun to observe. We explore the disco ball's potential for observing the moon and other bright astronomical phenomena.Comment: 6 pages, 7 figures. Submitted to Physics Education. Comments welcom

Reconstructing ICMEs with the toroidal Grad-Shafranov method

The main objective of this thesis is to model the magneticstructure of interplanetary coronal mass ejections (ICME) measuredin-situ from the WIND spacecraft positioned at L1. The modeling isdone by a magnetohydrodynamic reconstruction technique based onthe GS equation with a toroidal geometry. The purpose has been toextend the application of the reconstruction program to real dataand to test its performance when different input parameters arechanged. Two events are presented; 16-17 May 2012 and 15-16 May2005 ICMEs have been successfully reconstructed with this model. The main achievements of the study are that a) the code now worksfor real data b) the important parameters that can be changed fordifferent reconstructions in the code are the number of iterationsused to find the optimal Z-axis, the plasma pressure and the orderof the polynomial fitting of the flux functional, c) if all crosssection reconstructions for different variations of theseparameters strongly resembles each other then this is anindication that the model approximation is good and that the fluxrope exists. The results have been compared and verified withpreviously published studies of these events. Using a toroidal geometry for the GS reconstruction method weobtain very similar results to the one obtained with differentreconstruction techniques.This implies that at L1, the ICMEs haveexpanded so much that a cylindrical geometry is sufficient todescribe the flux rope geometry. The toroidal Grad-Shafranovreconstruction technique is best suited for circular, or slightlyelongated, flux rope cross section profiles but have been provento work for one complex ejecta consisting of two merged fluxropes. The toroidal model might become an important asset in thefuture when data from spacecraft closer to the Sun, such as ParkerSolar Probe and Solar Orbiter, is public. When the major radius ofthe flux rope is smaller the choice of geometry will most likelyhave a larger role than for measurements at L1 and so, thetoroidal Grad-Shafranov reconstruction technique will probably bethe better alternative of the models that exists today

Reconstructing ICMEs with the toroidal Grad-Shafranov method

The main objective of this thesis is to model the magneticstructure of interplanetary coronal mass ejections (ICME) measuredin-situ from the WIND spacecraft positioned at L1. The modeling isdone by a magnetohydrodynamic reconstruction technique based onthe GS equation with a toroidal geometry. The purpose has been toextend the application of the reconstruction program to real dataand to test its performance when different input parameters arechanged. Two events are presented; 16-17 May 2012 and 15-16 May2005 ICMEs have been successfully reconstructed with this model. The main achievements of the study are that a) the code now worksfor real data b) the important parameters that can be changed fordifferent reconstructions in the code are the number of iterationsused to find the optimal Z-axis, the plasma pressure and the orderof the polynomial fitting of the flux functional, c) if all crosssection reconstructions for different variations of theseparameters strongly resembles each other then this is anindication that the model approximation is good and that the fluxrope exists. The results have been compared and verified withpreviously published studies of these events. Using a toroidal geometry for the GS reconstruction method weobtain very similar results to the one obtained with differentreconstruction techniques.This implies that at L1, the ICMEs haveexpanded so much that a cylindrical geometry is sufficient todescribe the flux rope geometry. The toroidal Grad-Shafranovreconstruction technique is best suited for circular, or slightlyelongated, flux rope cross section profiles but have been provento work for one complex ejecta consisting of two merged fluxropes. The toroidal model might become an important asset in thefuture when data from spacecraft closer to the Sun, such as ParkerSolar Probe and Solar Orbiter, is public. When the major radius ofthe flux rope is smaller the choice of geometry will most likelyhave a larger role than for measurements at L1 and so, thetoroidal Grad-Shafranov reconstruction technique will probably bethe better alternative of the models that exists today

Analysis of the neutron albedo’s influence on TIP deviations in Forsmark 1

In the operation of a nuclear reactor, detailed calculations are performed to predict the power distribution in the core and to ensure the maintenance of a number of safety margins. Repeatedly during a power cycle, the predictions are verified in so-called TIP measurements, and the consequences of possible deviations are investigated. During the latest power cycles until today, the Forsmark 1 reactor has experienced large deviations in TIP measurements at the edge of the reactor core that have caused reasons to question the limits of the thermal margins needed to ensure fuel safety. These deviations have especially been present in the first half of cycle 34, which is why only data from this period is investigated in this report. It is expected that the deviations between predictions and measurements occur due to approximate calculations of the neutron albedo, i.e. the model for how neutrons leaving the core's periphery are reflected by materials surrounding the core. The objective of this work was to investigate whether the albedo model in the nuclear reactor core calculation programme POLCA7 may be adjusted to reduce deviations. If so, an additional objective would be to give details on the identified adjustments and, if possible, propose a better albedo model that in the future could be implemented on-line at Forsmark 1. Two analyses are presented, power deviation analysis and CPR (Critical PowerRatio) margin analysis. The presented investigations are based on existing albedo model commands ("cards") in the POLCA7 code, which have been used to introduce alternative albedo models in the calculations. Comparisons between updated and original albedo model cards were done with pre-written analysis scripts in MATLAB that calculated and plotted power deviation and thermal margins. This approach resulted in one set of proposed albedo parameters with respect to deviations in the power distribution and another set of proposed albedo parameters with respect to CPR margin. The two sets are similar, but not identical. More research in the subject is necessary since the two proposed parameter sets do not coincide and since there still is some deviation between measurements and predictions when applying these adjustments. In conclusion, the implemented albedo models give improved agreement between simulated and measured data. The results indicate that better predictions for future cycles may be obtained if these model improvements are introduced into future calculations. However, additional studies are required in order to draw conclusions that apply to the general case

Firefly: The Case for a Holistic Understanding of the Global Structure and Dynamics of the Sun and the Heliosphere

This white paper is on the HMCS Firefly mission concept study. Firefly focuses on the global structure and dynamics of the Sun's interior, the generation of solar magnetic fields, the deciphering of the solar cycle, the conditions leading to the explosive activity, and the structure and dynamics of the corona as it drives the heliosphere