Maria M. Kuznetsova

Simulation of the 23 July 2012 Extreme Space Weather Event: What if This Extremely Rare CME Was Earth Directed?

Extreme space weather events are known to cause adverse impacts on critical modern day technological infrastructure such as high-voltage electric power transmission grids. On 23 July 2012, NASAs Solar Terrestrial Relations Observatory-Ahead (STEREO-A) spacecraft observed in situ an extremely fast coronal mass ejection (CME) that traveled 0.96 astronomical units (∼1 AU) in about 19 h. Here we use the Space Weather Modeling Framework (SWMF) to perform a simulation of this rare CME. We consider STEREO-A in situ observations to represent the upstream L1 solar wind boundary conditions. The goal of this study is to examine what would have happened if this Rare-type CME was Earth-bound. Global SWMF-generated ground geomagnetic field perturbations are used to compute the simulated induced geoelectric field at specific ground-based active INTERMAGNET magnetometer sites. Simulation results show that while modeled global SYM-H index, a high-resolution equivalent of the Dst index, was comparable to previously observed severe geomagnetic storms such as the Halloween 2003 storm, the 23 July CME would have produced some of the largest geomagnetically induced electric fields, making it very geoeffective. These results have important practical applications for risk management of electrical power grids.

Electron nongyrotropy in the context of collisionless magnetic reconnection

Collisionless magnetized plasmas have the tendency to isotropize their velocity distribution function around the local magnetic field direction, i.e., to be gyrotropic, unless some spatial and/or temporal fluctuations develop at the particle gyroscales. Electron gyroscale inhomogeneities are well known to develop during the magnetic reconnection process. Nongyrotropic electron velocity distribution functions have been observed to play a key role in the dissipative process breaking the field line connectivity. In this paper, we present a new method to quantify the deviation of a particle population from gyrotropy. The method accounts for the full 3D shape of the distribution and its analytical formulation allows fast numerical computation. Regions associated with a significant degree of nongyrotropy are shown, as well as the kinetic origin of the nongyrotropy and the fluid signature it is associated with. Using the result of 2.5D Particle-In-Cell simulations of magnetic reconnection in symmetric and asymme...

Global MHD modeling of the impact of a solar wind pressure change

[1] A sudden increase in the solar wind dynamic pressure compresses the magnetosphere and launches compressional waves into the magnetosphere. The global response of the magnetosphere, including the ionosphere and the location of the field-aligned current (FAC) generation, to a step increase in the solar wind density has been studied using a global three-dimensional adaptive MHD model. As the density increase propagated along the flanks of the magnetopause, a two-phased response was seen in the ionosphere. The first response was an increase in FACs near the polar cap. For this response we found the location of FACs to lie just inside the magnetosphere. The second response was an increase in FACs at lower latitudes. The increase in FACs was in the same direction as region 1 currents. For the second response we found the location of FACs to fall well within the magnetosphere.

Modeling Extreme 'Carrington-Type' Space Weather Events Using Three-dimensional Global MHD Simulations

There is a growing concern over possible severe societal consequences related to adverse space weather impacts on man-made technological infrastructure. In the last two decades, significant progress has been made toward the first-principles modeling of space weather events, and three-dimensional (3-D) global magnetohydrodynamics (MHD) models have been at the forefront of this transition, thereby playing a critical role in advancing our understanding of space weather. However, the modeling of extreme space weather events is still a major challenge even for the modern global MHD models. In this study, we introduce a specially adapted University of Michigan 3-D global MHD model for simulating extreme space weather events with a Dst footprint comparable to the Carrington superstorm of September 1859 based on the estimate by Tsurutani et. al. (2003). Results are presented for a simulation run with “very extreme” constructed/idealized solar wind boundary conditions driving the magnetosphere. In particular, we describe the reaction of the magnetosphere-ionosphere system and the associated induced geoelectric field on the ground to such extreme driving conditions. The model setup is further tested using input data for an observed space weather event of Halloween storm October 2003 to verify the MHD model consistence and to draw additional guidance for future work. This extreme space weather MHD model setup is designed specifically for practical application to the modeling of extreme geomagnetically induced electric fields, which can drive large currents in ground-based conductor systems such as power transmission grids. Therefore, our ultimate goal is to explore the level of geoelectric fields that can be induced from an assumed storm of the reported magnitude, i.e., Dst∼=−1600 nT.

CalcDeltaB: An efficient postprocessing tool to calculate ground‐level magnetic perturbations from global magnetosphere simulations

Ground magnetic field variations can induce electric currents on long conductor systems such as high-voltage power transmission systems. The extra electric currents can interfere with normal operation of these conductor systems; and thus, there is a great need for better specification and prediction of the field perturbations. In this publication we present CalcDeltaB, an efficient postprocessing tool to calculate magnetic perturbations ΔB at any position on the ground from snapshots of the current systems that are being produced by first-principle models of the global magnetosphere-ionosphere system. This tool was developed during the recent “dB/dt” modeling challenge at the Community Coordinated Modeling Center that compared magnetic perturbations and their derivative with observational results. The calculation tool is separate from each of the magnetosphere models and ensures that the ΔB computation method is uniformly applied, and that validation studies using ΔB compare the performance of the models rather than the combination of each model and a built-in ΔB computation tool that may exist. Using the tool, magnetic perturbations on the ground are calculated from currents in the magnetosphere, from field-aligned currents between magnetosphere and ionosphere, and the Hall and Pedersen currents in the ionosphere. The results of the new postprocessing tool are compared with ΔB calculations within the Space Weather Modeling Framework model and are in excellent agreement. We find that a radial resolution of 1/30RE is fine enough to represent the contribution to ΔB from the region of field-aligned currents.

Comparison between hybrid and fully kinetic models of asymmetric magnetic reconnection: Coplanar and guide field configurations

Magnetic reconnection occurring in collisionless environments is a multi-scale process involving both ion and electron kinetic processes. Because of their small mass, the electron scales are difficult to resolve in numerical and satellite data, it is therefore critical to know whether the overall evolution of the reconnection process is influenced by the kinetic nature of the electrons, or is unchanged when assuming a simpler, fluid, electron model. This paper investigates this issue in the general context of an asymmetric current sheet, where both the magnetic field amplitude and the density vary through the discontinuity. A comparison is made between fully kinetic and hybrid kinetic simulations of magnetic reconnection in coplanar and guide field systems. The models share the initial condition but differ in their electron modeling. It is found that the overall evolution of the system, including the reconnection rate, is very similar between both models. The best agreement is found in the guide field system, which confines particle better than the coplanar one, where the locality of the moments is violated by the electron bounce motion. It is also shown that, contrary to the common understanding, reconnection is much faster in the guide field system than in the coplanar one. Both models show this tendency, indicating that the phenomenon is driven by ion kinetic effects and not electron ones.

GEM‐CEDAR challenge: Poynting flux at DMSP and modeled Joule heat

Poynting flux into the ionosphere measures the electromagnetic energy coming from the magnetosphere. This energy flux can vary greatly between quiet times and geomagnetic active times. As part of the Geospace Environment Modeling-coupling energetics and dynamics of atmospheric regions modeling challenge, physics-based models of the 3-D ionosphere and ionospheric electrodynamics solvers of magnetosphere models that specify Joule heat and empirical models specifying Poynting flux were run for six geomagnetic storm events of varying intensity. We compared model results with Poynting flux values along the DMSP-15 satellite track computed from ion drift meter and magnetic field observations. Although being a different quantity, Joule heat can in practice be correlated to incoming Poynting flux because the energy is dissipated primarily in high latitudes where Poynting flux is being deposited. Within the physics-based model group, we find mixed results with some models overestimating Joule heat and some models agreeing better with observed Poynting flux rates as integrated over auroral passes. In contrast, empirical models tend to underestimate integrated Poynting flux values. Modeled Joule heat or Poynting flux patterns often resemble the observed Poynting flux patterns on a large scale, but amplitudes can differ by a factor of 2 or larger due to the highly localized nature of observed Poynting flux deposition that is not captured by the models. In addition, the positioning of modeled patterns appear to be randomly shifted against the observed Poynting flux energy input. This study is the first to compare Poynting flux and Joule heat in a large variety of models of the ionosphere.

Influence of the dissipation mechanism on collisionless magnetic reconnection in symmetric and asymmetric current layers

Numerical studies implementing different versions of the collisionless Ohms law have shown a reconnection rate insensitive to the nature of the non-ideal mechanism occurring at the X line, as soon as the Hall effect is operating. Consequently, the dissipation mechanism occurring in the vicinity of the reconnection site in collisionless systems is usually thought not to have a dynamical role beyond the violation of the frozen-in condition. The interpretation of recent studies has, however, led to the opposite conclusion that the electron scale dissipative processes play an important dynamical role in preventing an elongation of the electron layer from throttling the reconnection rate. This work re-visits this topic with a new approach. Instead of focusing on the extensively studied symmetric configuration, we aim to investigate whether the macroscopic properties of collisionless reconnection are affected by the dissipation physics in asymmetric configurations, for which the effect of the Hall physics is substantially modified. Because it includes all the physical scales a priori important for collisionless reconnection (Hall and ion kinetic physics) and also because it allows one to change the nature of the non-ideal electron scale physics, we use a (two dimensional) hybrid model. The effects of numerical, resistive, and hyper-resistive dissipation are studied. In a first part, we perform simulations of symmetric reconnection with different non-ideal electron physics. We show that the model captures the already known properties of collisionless reconnection. In a second part, we focus on an asymmetric configuration where the magnetic field strength and the density are both asymmetric. Our results show that contrary to symmetric reconnection, the asymmetric model evolution strongly depends on the nature of the mechanism which breaks the field line connectivity. The dissipation occurring at the X line plays an important role in preventing the electron current layer from elongating and forming plasmoids.

On the origin of plasma sheet reconfiguration during the substorm growth phase

Recently Hsieh and Otto [2014] suggested that transport of the closed magnetic flux to the dayside reconnection region may be a key process which controls the reconfiguration of magnetotail during the substorm growth phase. We investigate this problem using global self-consistent MHD simulations, and confirm that magnetotail reconfiguration is essentially a 3D process which cannot be fully described based on 2D-like tail evolution powered by the magnetic flux loading into the lobes. We found that near-Earth return convection strength on the nightside is directly related to the intensity of dayside reconnection, which causes the formation of anti-sunward azimuthal pressure gradients that force plasma to flow towards the dayside magnetopause. This near-Earth part of global convection develops immediately after the onset of dayside reconnection and reaches a quasi-steady level in 10 - 15 minutes. Its magnitude exceeds the total sunward flux transport in the midtail plasma sheet at X≈−20RE by an order of magnitude, causing significant amount (0.1 - 0.2 GWb) of closed magnetic flux to be removed from the near Earth plasma sheet during moderate substorm. In that region the Bz depletion and current sheet thinning are closely related to each other, and the local Jy(Bz) relationship in the simulations matches reasonably well the power law expression found in the plasma sheet. In summary, global simulations confirm quantitatively that near-Earth return convection is primarily responsible for the severe depletion of the closed magnetic flux in the plasma sheet, major tail stretching and current sheet thinning in the near magnetotail at r < 15RE.

Results of ground tests and calibration of x-ray focal plane detectors for ART-XC/SRG instrument

The Russian Space Research Institute (IKI) has developed seven flight models and three spare models of the X-ray detectors for the ART-XC/SRG telescope. Each detector situated in the focal plane of ART-XC X-ray optics and includes CdTe die, front-end electronics, data processing, storage and telemetry units. In the Space Research Institute performed a vibration, thermal cycling and thermal vacuum tests of X-ray detectors. During this tests have been studied the leakage current stability, polarization rate, spectroscopic and imaging performance in the working temperature range. The current status of the X-ray detectors development and testing presented.