Modeling extreme “Carrington‐type” space weather events using three‐dimensional global MHD simulations

Abstract

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.

Searching for Carrington-like events and their signatures and triggers

“…Their models yielded an extremely large IMF B z component (>À200 nT for 2.5 h) and an equally large density (400-800 cm À3 ) and velocity (~2000 km s À1 ). Although coronagraph images show CMEs travelling at speeds like the one assumed by Ngwira et al (2014), the magnetic field and the solar wind density proposed are however unprecedented: the strongest absolute field strengths reported at 1 AU are 60-80 nT (less than one third) and the largest observed density is below 200 cm À3 .…”

“…The duskside detached aurora, whose separation to the oval was not visible at the SI-12 camera, on board the IMAGE satellite (Mende et al 2003), started to expand towards nightside at 17:17 UT. The nightside detached aurora was observed around 55°MLat, well below the nightside edge of the auroral oval around 63°MLat.…”

The Dehydration of Water Worlds via Atmospheric Losses

“…Table 3. Three hypothetical stellar wind input parameters for a solar-type star based on: (i) typical solar wind parameters at 1 AU at the current epoch (Schunk & Nagy 2009), (ii) ancient (4.02 Gyr) solar wind parameters at 1 AU (Boesswetter et al 2010) and (iii) solar wind values at the maximum total pressure of an extreme "Carrington-type" space weather event (Ngwira et al 2014). Note that 1 EUV (below) refers to the EUV flux received at Earth during the solar cycle maximum.…”

Influence of spatial variations of the geoelectric field on geomagnetically induced currents

“…This is obviously due to a pronounced local enhancement of the electric field, and this underlines the need to understand localised features in addition to regional scales (cf. Ngwira et al, 2015;Pulkkinen et al, 2015).…”

“…The geoelectric field varies rapidly temporarily and spatially as demonstrated, for example, by Beggan et al (2013), Bedrosian and Love (2015), Wei et al (2013) and Wang et al (2016) for regional and continental scales, and by Püthe and Kuvshinov (2013) and Ngwira et al (2015) for global scales. Temporal variations are due to time variations of space currents and are connected with time variations of the geomagnetic field by Faraday's law.…”