Three-dimensional analytical magnetohydrostatic equilibria of rigidly rotating magnetospheres in cylindrical geometry

We present three-dimensional solutions of the magnetohydrostatic equations in the co-rotating frame of reference outside a magnetized rigidly rotating cylinder. We make no symmetry assumption for the magnetic field, but to be able to make analytical progress we neglect outflows and specify a particular form for the current density. The magnetohydrostatic equations can then be reduced to a single linear partial differential equation for a pseudo-potential $U$, from which the magnetic field can be calculated by differentiation. The equation for $U$ can be solved by standard methods. The solutions can also be used to determine the plasma pressure, density and temperature as functions of all three spatial coordinates. Despite the obvious limitations of this approach, it can for example be used as a simple tool to create three-dimensional models for the closed field line regions of rotating magnetospheres without rotational symmetry.Comment: 13 pages, 2 figures, accepted for publication by Geophysical and Astrophysical Fluid Dynamic

Assessing the impact of a health intervention via user-generated Internet content

Assessing the effect of a health-oriented intervention by traditional epidemiological methods is commonly based only on population segments that use healthcare services. Here we introduce a complementary framework for evaluating the impact of a targeted intervention, such as a vaccination campaign against an infectious disease, through a statistical analysis of user-generated content submitted on web platforms. Using supervised learning, we derive a nonlinear regression model for estimating the prevalence of a health event in a population from Internet data. This model is applied to identify control location groups that correlate historically with the areas, where a specific intervention campaign has taken place. We then determine the impact of the intervention by inferring a projection of the disease rates that could have emerged in the absence of a campaign. Our case study focuses on the influenza vaccination program that was launched in England during the 2013/14 season, and our observations consist of millions of geo-located search queries to the Bing search engine and posts on Twitter. The impact estimates derived from the application of the proposed statistical framework support conventional assessments of the campaign

Critical science plan for the Daniel K. Inouye solar telescope (DKIST)

The National Science Foundation’s Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand, and model the basic physical processes that control the structure and dynamics of the Sun and its atmosphere. The first-light DKIST images, released publicly on 29 January 2020, only hint at the extraordinary capabilities that will accompany full commissioning of the five facility instruments. With this Critical Science Plan (CSP) we attempt to anticipate some of what those capabilities will enable, providing a snapshot of some of the scientific pursuits that the DKIST hopes to engage as start-of-operations nears. The work builds on the combined contributions of the DKIST Science Working Group (SWG) and CSP Community members, who generously shared their experiences, plans, knowledge, and dreams. Discussion is primarily focused on those issues to which DKIST will uniquely contribute

Self-consistent three-dimensional steady state solutions of the MHD equations with field-aligned incompressible flow.

We present self-consistent steady state solutions of the three-dimensional MHD equations including held-aligned incompressible flow. The solutions are calculated by a transformation method which allows the construction of steady state MHD solutions with subalfvenic flow from known solutions of static MHD and of steady state MHD solutions with superalfvenic flow from known solutions of steady state hydrodynamics. For the first time this transformation method is used to calculate self-consistent three-dimensional solutions of the steady state MHD equations with flow. We discuss possible applications of particular solutions to flow phenomena in the solar atmosphere such as the Evershed flow in sunspots and flows in coronal arcades.</p

The Green's function method for a special class of linear three-dimensional magnetohydrostatic equilibria.

We present the Green's function method for a special class of linear self-consistent three-dimensional solutions of the magnetohydrostatic (MHS) equations for which the current density is a combination of a linear force-free part and a part with non-fore e-free components. This allows the construction of MHS solutions of this class with arbitrary photospheric boundary conditions for B-z. These solutions can be used to extrapolate coronal magnetic fields from known longitudinal photospheric field data and provide a self-consistent description of magnetic field, plasma pressure, plasma density and plasma temperature. The method therefore allows a better comparison of models with observations of solar coronal structures. We will demonstrate how the method works by giving an illustrative example.</p

Systematic construction of exact 2-D MHD equilibria with steady, compressible flow in Cartesian geometry and uniform gravity

We present a systematic method for constructing two-dimensional magnetohydrodynamic equilibria with compressible flow in Cartesian geometry. This systematic method has already been developed in spherical geometry and applied in modelling solar and stellar winds and outflows (Vlahakis &amp; Tsinganos 1998) but is derived here in Cartesian geometry in the context of the solar atmosphere for the first time. Using the method we find several new classes of solutions, some of which generalise known solutions, including the Kippenhahn &amp; Schluter (1957) and Hood &amp; Anzer (1990) solar prominence models and the Tsinganos et al. (1993) coronal loop model with flow, and some of which are completely new. Having developed the method in full and summarised the several classes of solutions, we explore in a some detail one of the classes to illustrate the general construction method. From one of the new classes of solutions we calculate two loop-like solutions, one of which is the first exact two-dimensional magnetohydrodynamic equilibrium with trans-Alfvenic flow