A BPM Lifecycle Plug-in for Modeling Methods Agility

Business Process Management literature has proposed several BPM lifecycles on a level of abstraction that is modeling method -agnostic, i.e. they consider the modeling language and tool support an underlying invariant or technological concern. While remaining on the same abstraction layer, we highlight a method agility requirement observed in commercial BPM consulting projects - concretely, it manifests as change requests for the modeling language or tool, from one lifecycle iteration to the next, leading to situations of model value co-creation as customer demands are assimilated in the modeling method. Based on a conceptualization of such situations, a lifecycle plug-in is proposed in the form of a methodology and associated tool support, allowing for responsive evolution of the adopted modeling method with impact on several lifecycle phases. Historical examples from the evolution of a BPM product are provided to illustrate and classify the demands that motivate the existence of this lifecycle plug-in

Fractal Dimension Analysis of Solar Granulation- Boxcounting dimension

The fractal dimension of high resolution Hinode solar granulation observations and numerical simulations is studied and the results are compared. These observations are not influenced by atmospheric seeing conditions and therefore allow a more realistic estimate of the fractal dimension than in previous works. Though arriving at similar results for observations and simulation data, non integer fractal dimension $<2$, some differences in the numerical values occur, and these are discussed

Solar Ca II K plage regions as proxies for magnetic fields of solar like stars

Solar plage regions can be observed directly, whereas plage regions as well as star-spots on solar like stars, can only be detected via their contribution to spectral irradiances of these stars. Such a spectral irradiance can be modelled by fractions belonging to the quiet star, the plage regions, and the star-spots. The idea is, to measure these fractions as well as the intensity enhancement due to plage regions on our Sun and then use this information to be able to model solar like stars. We verify the close connection between the size of the plage regions and the luminosity of the Sun, given by a correlation coefficient of 0.822. The size of the plage regions varies from 0%, when the Sun is very quiet, up to 2.7% for a more active Sun (a complete solar cycle is not yet analysed and hence our study does not contain an activity maximum). The used data sets are full-disc images taken by the RISE/PSPT instrument during the period from 2005 to 2012, at the MLSO

Photospheric magnetic structure of coronal holes

In this study, we investigate in detail the photospheric magnetic structure of 98 coronal holes using line-of-sight magnetograms of SDO/HMI, and for a subset of 42 coronal holes using HINODE/SOT G-band filtergrams. We divided the magnetic field maps into magnetic elements and quiet coronal hole regions by applying a threshold at $\pm 25$ G. We find that the number of magnetic bright points in magnetic elements is well correlated with the area of the magnetic elements (cc=$0.83\pm 0.01$). Further, the magnetic flux of the individual magnetic elements inside coronal holes is related to their area by a power law with an exponent of $1.261\pm 0.004$ (cc=$0.984\pm 0.001$). Relating the magnetic elements to the overall structure of coronal holes, we find that on average ($69\pm 8$) % of the overall unbalanced magnetic flux of the coronal holes arises from long-lived magnetic elements with lifetimes > 40 hours. About ($22\pm 4$) % of the unbalanced magnetic flux arises from a very weak background magnetic field in the quiet coronal hole regions with a mean magnetic field density of about 0.2 to 1.2 G. This background magnetic field is correlated to the flux of the magnetic elements with lifetimes of > 40 h (cc=$0.88\pm 0.02$). The remaining flux arises from magnetic elements with lifetimes < 40 hours. By relating the properties of the magnetic elements to the overall properties of the coronal holes, we find that the unbalanced magnetic flux of the coronal holes is completely determined by the total area that the long-lived magnetic elements cover (cc=$0.994\pm 0.001$)

Detection of small convective patterns in observations and simulations

Recent results from high resolution solar granulation observations indicate the existence of a population of small granular cells on scales below 600 km in diameter, located in the intergranular lanes. We studied a set of Hinode SOT images and high resolution radiation hydrodynamics simulations in order to analyze small granular cells and to study their physical properties. An automated image segmentation algorithm specifically adapted to high resolution simulations for the identification of granules was developed. The algorithm was also used to analyze and compare physical quantities provided by the simulation and the observations. We found that small granules make a distinct contribution to the total area of granules. Both in observations and simulations, small granular cells exhibit on average lower intensities and vertical velocities

Two-Fluid 2.5D MHD-Code for Simulations in the Solar Atmosphere

We investigate magnetic reconnection due to the evolution of magnetic flux tubes in the solar chromosphere. We developed a new numerical two-fluid magnetohydrodynamic (MHD) code which will perform a 2.5D simulation of the dynamics from the upper convection zone up to the transition region. Our code is based on the Total Variation Diminishing Lax-Friedrichs scheme and makes use of an alternating-direction implicit method, in order to accommodate the two spatial dimensions. Since we apply a two-fluid model for our simulations, the effects of ion-neutral collisions, ionization/recombination, thermal/resistive diffusivity and collisional/resistive heating are included in the code. As initial conditions for the code we use analytically constructed vertically open magnetic flux tubes within a realistic stratified atmosphere. Initial MHD tests have already shown good agreement with known results of numerical MHD test problems like e.g. the Orszag-Tang vortex test

Could switchbacks originate in the lower solar atmosphere? II. Propagation of switchbacks in the solar corona

The magnetic switchbacks observed recently by the Parker Solar Probe have raised the question about their nature and origin. One of the competing theories of their origin is the interchange reconnection in the solar corona. In this scenario, switchbacks are generated at the reconnection site between open and closed magnetic fields, and are either advected by an upflow or propagate as waves into the solar wind. In this paper we test the wave hypothesis, numerically modeling the propagation of a switchback, modeled as an embedded Alfvén wave packet of constant magnetic field magnitude, through the gravitationally stratified solar corona with different degrees of background magnetic field expansion. While switchbacks propagating in a uniform medium with no gravity are relatively stable, as reported previously, we find that gravitational stratification together with the expansion of the magnetic field act in multiple ways to deform the switchbacks. These include WKB effects, which depend on the degree of magnetic field expansion, and also finite-amplitude effects, such as the symmetry breaking between nonlinear advection and the Lorentz force. In a straight or radially expanding magnetic field the propagating switchbacks unfold into waves that cause minimal magnetic field deflections, while a super-radially expanding magnetic field aids in maintaining strong deflections. Other important effects are the mass uplift the propagating switchbacks induce and the reconnection and drainage of plasmoids contained within the switchbacks. In the Appendix, we examine a series of setups with different switchback configurations and parameters, which broaden the scope of our study

Parallelization of the SIR code

A high-resolution 3-dimensional model of the photospheric magnetic field is essential for the investigation of small-scale solar magnetic phenomena. The SIR code is an advanced Stokes-inversion code that deduces physical quantities, e.g. magnetic field vector, temperature, and LOS velocity, from spectropolarimetric data. We extended this code by the capability of directly using large data sets and inverting the pixels in parallel. Due to this parallelization it is now feasible to apply the code directly on extensive data sets. Besides, we included the possibility to use different initial model atmospheres for the inversion, which enhances the quality of the results

New insights into the temporal evolution of MBPs

Magnetic bright points (MBPs) are among the most fascinating and interesting manifestations of small-scale solar magnetic fields. In the present work the temporal evolution of MBPs is followed in data sets taken by the Hinode satellite. The analysed data and obtained results confirm a recently presented study done with Sunrise/IMaX data, namely that MBPs are features undergoing fast evolution with magnetic fields starting around the equipartition field strength, then showing strong downflows (between 2 to 4 km/s) causing the magnetic field to amplify into the kG range (700 to 1500 G) before dissolving again. Furthermore the initial field inclinations depend on the initial magnetic field strengths and show an evolution with more vertical angles at some point during the evolution