Accelerated particle beams in a 3D simulation of the quiet Sun

Observational and theoretical evidence suggest that beams of accelerated particles are produced in flaring events of all sizes in the solar atmosphere, from X-class flares to nanoflares. Current models of these types of particles in flaring loops assume an isolated 1D atmosphere. A more realistic environment for modelling accelerated particles can be provided by 3D radiative magnetohydrodynamics codes. Here, we present a simple model for particle acceleration and propagation in the context of a 3D simulation of the quiet solar atmosphere, spanning from the convection zone to the corona. We then examine the additional transport of energy introduced by the particle beams. The locations of particle acceleration associated with magnetic reconnection were identified by detecting changes in magnetic topology. At each location, the parameters of the accelerated particle distribution were estimated from local conditions. The particle distributions were then propagated along the magnetic field, and the energy deposition due to Coulomb collisions with the ambient plasma was computed. We find that particle beams originate in extended acceleration regions that are distributed across the corona. Upon reaching the transition region, they converge and produce strands of intense heating that penetrate the chromosphere. Within these strands, beam heating consistently dominates conductive heating below the bottom of the transition region. This indicates that particle beams qualitatively alter the energy transport even outside of active regions.Comment: Accepted for publication in A&

Implementing accelerated particle beams in a 3D simulation of the quiet Sun

Context. The magnetic field in the solar atmosphere continually reconnects and accelerates charged particles to high energies. Simulations of the atmosphere in three dimensions that include the effects of accelerated particles can aid our understanding of the interplay between energetic particle beams and the environment where they emerge and propagate. We presented the first attempt at such a simulation in a previous paper, emphasising the physical model of particle beams. However, the numerical implementation of this model is not straightforward due to the diverse conditions in the atmosphere and the way we must distribute computation between multiple CPU cores. Aims. Here, we describe and verify our numerical implementation of energy transport by electron beams in a 3D magnetohydrodynamics code parallelised by domain decomposition. Methods. We trace beam trajectories using a Runge-Kutta scheme with adaptive step length control and integrate deposited beam energy along the trajectories with a hybrid analytical and numerical approach. To parallelise this, we coordinate beam transport across subdomains owned by separate processes using a buffering system designed to optimise data flow. Results. Using an ad hoc magnetic field with analytical field lines as a test scenario, we show that our parallel implementation of adaptive tracing efficiently follows a challenging trajectory with high precision. By timing executions of electron beam transport with different numbers of processes, we found that the processes communicate with minimal overhead but that the parallel scalability is still sublinear due to workload imbalance caused by the uneven spatial distribution of beams.Comment: Submitted to Astronomy & Astrophysic

Accelerated particle beams in a 3D simulation of the quiet Sun. Lower atmospheric spectral diagnostics

Nanoflare heating through small-scale magnetic reconnection events is one of the prime candidates to explain heating of the solar corona. However, direct signatures of nanoflares are difficult to determine, and unambiguous observational evidence is still lacking. Numerical models that include accelerated electrons and can reproduce flaring conditions are essential in understanding how low-energetic events act as a heating mechanism of the corona, and how such events are able to produce signatures in the spectral lines that can be detected through observations. We investigate the effects of accelerated electrons in synthetic spectra from a 3D radiative magnetohydrodynamics simulation to better understand small-scale heating events and their impact on the solar atmosphere. We synthesised the chromospheric Ca II and Mg II lines and the transition region Si IV resonance lines from a quiet Sun numerical simulation that includes accelerated electrons. We calculated the contribution function to the intensity to better understand how the lines are formed, and what factors are contributing to the detailed shape of the spectral profiles. The synthetic spectra are highly affected by variations in temperature and vertical velocity. Beam heating exceeds conductive heating at the heights where the spectral lines form, indicating that the electrons should contribute to the heating of the lower atmosphere and hence affect the line profiles. However, we find that it is difficult to determine specific signatures from the non-thermal electrons due to the complexity of the atmospheric response to the heating in combination with the relatively low energy output (~1e21 erg/s). Even so, our results contribute to understanding small-scale heating events in the solar atmosphere, and give further guidance to future observations

Intelligent User Interfaces for Expert System Applications in Power Plants

This paper describes how an expert system shell has been integrated into an interactive tool-kit which is tailored for the development of easy to use graphical environments. The result is that the expert system technology can be shielded from the end-user with all the capabilities still available. An expert system for diagnosis of heat rate degradation in power plants is discussed to illustrate the utility of the approach

Commentaries on Health Services Research

A cornerstone of patient-centered medical homes (PCMHs) is team-based care; however, little information exists on the composition of providers delivering direct primary care in PCMHs. This study examined the number and distribution of primary care physicians, NPs, and PAs in New York state practices (n=7,431). Designated PCMHs had more NPs and PAs per primary care physician relative to non-PCMHs. The ratios of NPs to primary care physicians were almost twice as high in PCMHs compared with non-PCMHs (0.20 and 0.11), and ratios were similarly different for PAs to primary care physicians (0.16 and 0.09, respectively). The multivariate analyses also support that higher NP and PA staffing was associated with PCMH designation—that is, for every 25 primary care physicians, PCMHs had one additional NP and/or PA. The growth of PCMHs may require more NPs and PAs to meet the anticipated growth in demand for healthcare. Policy- and practice-level changes are necessary to use them in the most effective ways