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Abstract: While it is widely known that coronal mass ejections and their related solar wind features are significant drivers of activity with geospace it is less known that corotating interaction regions (CIRs) and the high speed stream (HSS) periods that precede them are also drivers of activity within geospace. The most recent extended and weak solar minimum interval has brought renewed attention to the space weather impacts of CIR+HSS periods since the highly structured and relatively stable coronal hole features on the Sun resulted in numerous CIR+HSS periods. In this paper we examine two Carrington Rotations (CRs) using the Coupled Magnetosphere Ionosphere Thermosphere (CMIT) model. CR2060 lasted from August 14, 2007 to September 11, 2007 and contained three CIR+HSS periods. CR2068, also known as the Whole Heliosphere Interval (WHI), began on March 20, 2008 and lasted until April 16, 2008 and contained two CIR+HSS periods. For each CR simulations driven by both L1 solar wind observations from the OMNI data set and L1 conditions extracted from CORHEL heliospheric simulations were conducted. The heliospheric simulation results capture the velocity and density structures seen in the solar wind well for CR2060 and only get one of the CIR+HSS periods in CR2068. In each CR the heliospheric simulations produce a much weaker IMF and have less temporal variability in all parameters. We compare the results of the CMIT simulations for each CR to observations of the cross polar cap potential (CPCP), hemispheric power (HP), and index including the computation of RMS and cross correlation error metrics. We examine the response of the thermospheric density during these intervals by utilizing data from the CHAMP satellite. In the magnetosphere we use magnetic field data from the GOES spacecraft to asses the different simulations ability to describe the distribution and intensity the ULF wave power. Our results show that the L1 driven simulations under-estimates the index and HP and over-estimates the CPCP. We believe that over estimation of the CPCP is directly linked to the low HP highlighting the need for an improved precipitation model within CMIT. The ULF power in the L1 simulations compares well with the observations, especially for the compressional component important in radiation belt energization processes. In all cases, the CMIT simulations driven by the heliospheric simulation results produce dramatically inferior predictions highlighting the importance of having good IMF predictions in heliospheric model results and possibly indicating the importance of having fluctuations in the solar wind. [Copyright &y& Elsevier]

Abstract: A goal of predictive models of the space radiation environment is to provide advanced knowledge of significant variations in the highly energetic particle populations that form the Earth''s radiation belts. The global geomagnetic field models that result from the Center for Integrated Space-weather Modeling (CISM) effort will provide a necessary input, a real-time description of the dynamic variation of the electromagnetic fields in the magnetosphere, for conducting detailed simulations of the radiation belts. In this work, we describe the issues and techniques that CISM will use to provide a physical space radiation model. An analysis of the global field configurations typical of the magneto hydrodynamic (MHD) models used in CISM suggest that much of the radiation belt modeling can proceed under a guiding center particle approximation, whereby individual, non-interacting test particles are used to track the aggregate dynamics of the radiation belts. This technique provides a relatively simple means of both conducting the necessary simulations, and coupling the relevant codes with other elements of the CISM project. The guiding center equations used to track the particles are based on a phase-space conserving approximation that conserves energy in regions of high curvature. Examples of test particle simulations with the MHD fields are given, both in the initial trapped particle population, and among the energetic particles that form the plasma sheet in the tail. These simulations suggest that multiple radiation belt models running simultaneously in the framework provided by CISM can be combined to provide an overall picture of the energetic particle environment. Finally, analysis of the spectral properties of the fields suggests how an alternate approach to modeling the global radiation belts, solution of the appropriate transport equations, might be advanced through the CISM effort. [Copyright &y& Elsevier]

We examine the simulation of the January 10 1997, magnetic storm using the Lyon-Fedder-Mobarry three-dimensional magnetohydrodynamic simulation of the interaction of the solar wind with the magnetosphere. We explore the response of the energy coupling between the solar wind and the magnetosphere during the extreme solar wind conditions produced by magnetic cloud that hit the Earth's magnetosphere during the first half of January 10. During the early part of the event, the simulation produced substorm-like behavior marked by a loading and unloading of stored magnetic flux. However, during the period of strong, sustained solar wind energy Input, the loading-unloading behavior essentially goes away sd the simulation entered a directly driven phase. During this direct-driving phase the solar wind dynamic pressure controlled the ionospheric Joule heating in the simulation. [ABSTRACT FROM AUTHOR]

Abstract In cylindrical/spherical geometries, MHD solvers using explicit finite-volume methods face restrictive time steps imposed by the CFL condition due to the clustering of cells in the azimuthal direction near the pole/axis. We use a conservative averaging-reconstruction method (Ring Average) on structured cylindrical/spherical mesh to remove this severe time step restriction for multi-dimensional curvilinear finite-volume MHD solvers. The Ring Average technique is implemented as a post-processing step and thus requires no changes to the existing data structure, grid definition or numerical methods in the original MHD solver. This paper describes the Ring Average algorithm and presents simulation results using field loop advection and MHD blast waves in cylindrical/spherical geometries for validation. The algorithm is shown to be inexpensive and easily implemented in existing curvilinear finite-volume MHD solvers. Highlights • Ring Average is a "post-processing" module without modifying the original solver. • Ring Average relaxes time-step restrictions in MHD solvers with axis singularities. • Ring Average conserves mass, momentum and energy for proper shock propagations. • Ring Average works for codes with either divergence cleaning or constrained transport. [ABSTRACT FROM AUTHOR]

The role of solar wind density in the cross polar cap potential (CPCP) response under northward interplanetary magnetic field is investigated with observation-based global simulations. A rare event was reported by Clauer et al. (2016) during which the ionospheric electric field EISP does not saturate under extreme interplanetary electric field (IEF) of ∼15 mV/m. While commonly utilized coupling functions based on IEF fail to provide an unambiguous explanation for the linear response, the Lyon-Fedder-Mobarry-Magnetosphere-Ionosphere Coupler/Solver model is used to explore the mechanisms in this study. The model first reproduces the observed linear features of the EISP. The simulated CPCP also responds linearly to IEF variations. A controlled simulation is designed with solar wind density artificially reduced to 10% of the observed value while all other parameters such as the IEF are kept the same. The controlled simulation shows saturation of the EISP as well as the CPCP. Further analysis shows the difference in the magnetosheath plasma β, implying the distinct dominant forces between the two simulations. The Lopez magnetosheath force balance theory is used to explain the CPCP responses under different solar wind densities. This comparison study highlights the role of solar wind density in determining the magnetosphere-ionosphere response to extreme interplanetary drivings. [ABSTRACT FROM AUTHOR]

This paper reviews the state of knowledge concerning the source of magnetospheric plasma at Earth. Source of plasma, its acceleration and transport throughout the system, its consequences on system dynamics, and its loss are all discussed. Both observational and modeling advances since the last time this subject was covered in detail (Hultqvist et al., Magnetospheric Plasma Sources and Losses, ) are addressed. [ABSTRACT FROM AUTHOR]

A recent study showed that 355-nm nanosecond lasers cut cornea with similar precision to infrared femtosecond lasers. However, use of ultraviolet wavelength requires precise assessment of ocular safety to determine the range of possible ophthalmic applications. In this study, the 355-nm nanosecond laser was evaluated for corneal and iris damage in rabbit, porcine, and human donor eyes as determined by minimum visible lesion (MVL) observation, live/dead staining of the endothelium, and apoptosis assay. Single-pulse damage to the iris was evaluated on porcine eyes using live/dead staining. In live rabbits, the cumulative median effective dose (ED50) for corneal damage was 231 J/cm2, as seen by lesion observation. Appearance of endothelial damage in live/dead staining or apoptosis occurred at higher radiant exposure of 287 J/cm2. On enucleated rabbit and porcine corneas, ED50 was 87 and 52 J/cm2, respectively, by MVL, and 241 and 160 J/cm2 for endothelial damage. In human eyes, ED50 for MVL was 110 J/cm2 and endothelial damage at 453 J/cm2. Single-pulse iris damage occurred at ED50 of 208 mJ/cm2. These values determine the energy permitted for surgical patterns and can guide development of ophthalmic laser systems. Lower damage threshold in corneas of enucleated eyes versus live rabbits is noted for future safety evaluation. [ABSTRACT FROM AUTHOR]

Computer models enable scientists to investigate real-world phenomena in a virtual laboratory using computer experiments. Statistical calibration enables scientists to incorporate field data in this analysis. However, the practical application is hardly straightforward for data structures such as spatial-temporal fields, which are usually large or not well represented by a stationary process model. We present a computationally efficient approach to estimating the calibration parameters using a criterion that measures discrepancy between the computer model output and field data. One can then construct empirical distributions for the calibration parameters and propose new computer model trials using sequential design. The approach is relatively simple to implement using existing algorithms and is able to estimate calibration parameters for large and nonstationary data. Supplementary R code is available online. [ABSTRACT FROM AUTHOR]

Abstract: We present a statistical comparison of plasma sheet properties from Geotail measurements and from the Lyon–Fedder–Mobarry (LFM) global magnetohydrodynamic (MHD) model. We compare more than three years of Geotail data with 10 consecutive days of simulation results driven by real solar wind data. Both studies have statistically similar solar wind inputs and a plasma sheet definition that follows from criteria that are widely used in the literature. We map the average plasma pressures, fields, and flows as functions of position within the equatorial plasma sheet. The comparisons show a persistent dawn–dusk asymmetry in the statistical patterns of plasma flows and electric fields in both the Geotail and the simulation results. Geotail observes a less rapid fall-off of thermal pressure with downtail distance than is seen in the simulation. The Geotail dataset suffers from an orbital bias, but we show the dawn–dusk asymmetry persists after accounting for the bias. Overall, our study finds similar statistical plasma pressures, magnetic pressures, and perpendicular flows in Geotail measurements, and the LFM MHD regions of the plasma sheet. [Copyright &y& Elsevier]

Abstract: This paper describes the 3D simulation of a space weather event using the coupled model approach adopted by the Center for Integrated Space Weather Modeling (CISM). The simulation employs corona, solar wind, and magnetosphere MHD models, and an upper atmosphere/ionosphere fluid dynamic model, with interfaces that exchange parameters specifying each component of the connected solar terrestrial system. A hypothetical coronal mass ejection is launched from the Sun by a process emulating photospheric field changes such as are observed with solar magnetographs. The associated ejected magnetic flux rope propagates into a realistically structured solar wind, producing a leading interplanetary shock, sheath, and magnetic cloud. These reach 1AU where the solar wind and interplanetary magnetic field parameters are used to drive the magnetosphere–ionosphere–thermosphere coupled model in the same manner as upstream in situ measurements. The simulated magnetosphere responds with a magnetic storm, producing enhanced convection and auroral energy inputs to the upper atmosphere/ionosphere. These results demonstrate the potential for future studies using a modular, systemic numerical modeling approach to space weather research and forecasting. [Copyright &y& Elsevier]