EUropean Heliospheric FORecasting Information Asset (EUHFORIA) is a physics-based data-driven solar wind and CME propagation model designed for space weather forecasting and event analysis investigations. Although EUHFORIA can predict the solar wind plasma and magnetic field properties at Earth, it is not equipped to quantify the geoeffectiveness of the solar transients in terms of the geomagnetic indices like the disturbance storm time (Dst) index and the eauroral indices that quantify the impact of the magnetized plasma encounters on Earth's magnetosphere. Therefore, we couple EUHFORIA with the Open Geospace General Circulation Model (OpenGGCM), a magnetohydrodynamic model of the response of Earth's magnetosphere, ionosphere, and thermosphere, to transient solar wind characteristics. In this coupling, OpenGGCM is driven by the solar wind and interplanetary magnetic field obtained from EUHFORIA simulations to produce the magnetospheric and ionospheric response to the CMEs. This coupling is validated with two observed geoeffective CME events driven with the spheromak flux-rope CME model. We compare these simulation results with the indices obtained from OpenGGCM simulations driven by the measured solar wind data from spacecraft. We further employ the dynamic time warping (DTW) technique to assess the model performance in predicting Dst. The main highlight of this study is to use EUHFORIA simulated time series to predict the Dst and auroral indices 1 to 2 days in advance, as compared to using the observed solar wind data at L1, which only provides predictions 1 to 2 hours before the actual impact.

Much of what we know about the solar wind’s interaction with the Earth’s magnetosphere has been gained from isolated in-situ measurements by single or multiple spacecraft. Based on their observations, we know that reconnection, whether on the dayside magnetopause or deep within the Earth’s magnetotail, controls the bulk flow of solar wind energy into and through the global system and that nightside activity provides the energized particles that power geomagnetic storms. But by their very nature these isolated in-situ measurements cannot provide an instantaneous global view of the entire system or its cross-scale dynamics. To fully quantify the dynamics of the coupled solar wind-magnetosphere requires comprehensive end-to-end global imaging of the key plasma structures that comprise the magnetosphere which have spatial resolutions that exceeds anything possible with multi-point or constellation situ measurements. Global, end-to-end, imaging provides the pathway to understanding the system as a whole, its constituent parts, and its cross-scale processes on a continuous basis, as needed to quantify the flow of solar wind energy through the global magnetospheric system. This paper describes how a comprehensively-instrumented single spacecraft in a high-altitude, high-inclination orbit coupled with ground-based instruments provides the essential observations needed to track and quantify the flow of solar wind energy through the magnetosphere. This includes observations of the solar wind plasma and magnetic field input, the magnetopause location in soft X-rays, the auroral oval in far ultraviolet, the ring current in energetic neutrals, the plasmasphere in extreme ultraviolet, the exosphere in Lyman-α, and the microstructure of the nightside auroral oval from ground-based all sky cameras.

It is well known that the polar cap, delineated by the open–closed field line boundary (OCB), responds to changes in the interplanetary magnetic field (IMF). In general, the boundary moves equatorward when the IMF turns southward and contracts poleward when the IMF turns northward. However, observations of the OCB are spotty and limited in local time, making more detailed studies of its IMF dependence difficult. Here, we simulate five solar storm periods with the coupled model consisting of the Open Geospace General Circulation Model (OpenGGCM) coupled with the Coupled Thermosphere Ionosphere Model (CTIM) and the Rice Convection Model (RCM), i.e., the OpenGGCM-CTIM-RCM, to estimate the location and dynamics of the OCB. For these events, polar cap boundary location observations are also obtained from Defense Meteorological Satellite Program (DMSP) precipitation spectrograms and compared with the model output. There is a large scatter in the DMSP observations and in the model output. Although the model does not predict the OCB with high fidelity for every observation, it does reproduce the general trend as a function of IMF clock angle. On average, the model overestimates the latitude of the open–closed field line boundary by 1.61∘. Additional analysis of the simulated polar cap boundary dynamics across all local times shows that the MLT of the largest polar cap expansion closely correlates with the IMF clock angle, that the strongest correlation occurs when the IMF is southward, that during strong southward IMF the polar cap shifts sunward, and that the polar cap rapidly contracts at all local times when the IMF turns northward.

It is well known that the polar cap, delineated by the Open Closed field line Bound ary (OCB), responds to changes in the Interplanetary Magnetic Field (IMF). In general, the boundary moves equatorward when the IMF turns southward and contracts poleward when the IMF turns northward. However, observations of the OCB are spotty and limited in local time, making more detailed studies of its IMF dependence difficult. Here, we simulate five solar storm periods with the coupled OpenGGCM-RCM-CTIM model to estimate the location and dynamics of the OCB. For these events, polar cap boundary location observations are also obtained from Defense-Meteorological Satellite Pro- gram (DMSP) precipitation spectrograms and compared with the model output. There is a large scatter in the DMSP observations and in the model output. However, we generally find good agreement between the model and the observations. On average, the model overestimates the latitude of the open-closed field line boundary by 1.61◦. Additional analysis of the simulated polar cap boundary dynamics across all local times shows that the MLT of the largest polar cap expansion closely correlates with the IMF clock angle; that the strongest correlation occurs when the IMF is southward; that during strong southward IMF the polar cap shifts sunward; and that the polar cap rapidly contracts at all local times when the IMF turns northward.

In-situ measurements in the magnetotail are sparse and limited to single points. On the other hand, there is a broad range of observations, including magnetometers, aurora imagers, and radars, in the ionosphere. Since the nightside ionosphere resembles the magnetotail plasma sheet dynamics projection, it can be used to monitor the tail's dynamics. A proper interpretation of the ionosphere and ground observations necessitates understanding the coupling processes between the ionosphere and the magnetosphere. Here, we use the global magnetohydrodynamic simulation model, OpenGGCM-CTIM-RCM, to investigate these coupling processes during periods when the magnetic flux is transported through the tail via narrow fast flow channels, typically called bursty bulk flows (BBFs). We consider three relevant states of the magnetotail: immediately before the substorm's onset, during the expansion of the substorm, and during a steady magnetic convection (SMC) event. The number of flow channels increases, and they penetrate closer to the Earth during SMC. The IMF By direction influences fast flows' location but not their orientation in the plasma sheet during this event. However, the dimension of fast flows and streamers do not depend on the IMF conditions and state of the magnetosphere.

Over the past few decades global simulations have emerged as a valuable new tool to study the magnetosphere-ionosphere-thermosphere system, to the point where some of them are considered community models available for runs on demand by the community at the Community Coordinated Modeling Center (CCMC). Most leading global models are still based on the conventional and well-established MHD approximation; they are remarkably successful reproducing the major features and processes in geospace. Here, we briefly review the purpose and utility of such models, their history, their basic structure, the need for submodels of the ionosphere-thermosphere system and the inner magnetosphere, as well as inherent model limitations. The major computational and numerical constraints are discussed and recent simulations addressing plasma injections and sawtooth oscillations are presented.

Extreme space weather events are extremely rare, but pose a significant threat to our infrastructure. The one known event of such kind was the Carrington storm of 1859, but it was not well documented; in particular the solar wind and IMF conditions that caused it remain guesses. On the other hand, the STEREO-A observations of July 23, 2012 showed solar wind and IMF parameters that are most likely comparable to those of the Carrington event, and remind us that such extreme events are very well possible even during times of a quiet sun. Here, we use OpenGGCM simulations of such events to assess the effects of such solar wind and IMF on the magnetosphere. Precious work has shown that during the much more benign Halloween storm the nose of the magnetopause was as close as 4.9 RE, with an accordingly large polar cap. We will present simulations of a sequence of scaled-up storms with increasingly larger driving and demonstrate the further expansion of the polar cap, intensity of plasma injections, and the eventual saturation. In addition, we will show how the ionosphere potential penetrates to lower latitudes and affects the ionosphere and thermosphere at mid latitudes when the solar wind drivers become extreme.

In this work we perform a Sun-to-Earth comprehensive analysis of the July 12, 2012 CME with the aim of testing the space weather predictive capabilities of the newly developed EUHFORIA heliospheric model integrated with a flux rope model. In order to achieve this goal, we make use of a model chain approach by using EUHFORIA outputs at Earth as input parameters for the OpenGGCM magnetospheric model.

We use Open Geospace General Circulation Model (OpenGGCM) simulations to predict magnetic field perturbations at Low Earth Orbiting (LEO) satellites such as Swarm, at high latitudes. The simulations allow us to separate three different major contributions to the observed perturbations, i.e., the perturbations caused by currents in the outer magnetosphere, field-aligned currents (FACs), and the currents flowing in the ionosphere. We find that at an altitude of 500 km the strongest contribution comes from FACs, followed by the perturbations caused by the ionospheric currents, while the magnetospheric currents make only a minor contribution. The high latitude perturbations do not average out over extended quiet time periods. There are significant variations in the patterns; however, on a large scale, the basic shape of the pattern remains stable. Thus, without explicitly removing the perturbations from the data, any spherical harmonics fit is expected to incur a bias. Although the predicted OpenGGCM perturbations do not compare particularly well with Swarm data, the simulations reproduce the overall pattern. However, they may still be useful to reduce the bias of the ensemble and produce better global spherical harmonic fits, by producing an ensemble whose external field contributions average out. Since this paper only scratches the surface of the role that models of the external field can play in producing unbiased internal field models, much progress is still possible, for example by improving the external model, investigating larger ensembles, and by considering data from geomagnetically disturbed times.