Geospace Environment Modeling 2008–2009 Challenge: Geosynchronous magnetic field

Abstract

In this paper the metrics‐based results of the inner magnetospheric magnetic field part of the 2008–2009 GEM Metrics Challenge are reported. The Metrics Challenge asked modelers to submit results for four geomagnetic storm events and five different types of observations that can be modeled by statistical or climatological or physics‐based (e.g., MHD) models of the magnetosphere‐ionosphere system. We present the results of 12 model settings that were run at the Community Coordinated Modeling Center and at the institutions of various modelers for these events. To measure the performance of each of the models against the observations, we use direct comparisons between the strength of the measured magnetic field (B), the sine of the elevation angle Θxz (τ), and the spectral power of fluctuations for both quantities. We find that model rankings vary widely by type of variable and skill score used. None of the models consistently performs best for all events. We find that empirical models perform well for weak storm events, and physics‐based (magnetohydrodynamic) models are better for strong storm events. Within a series of runs of the same model we find that higher resolution may not always improve results unless more physics of the inner magnetosphere, such as the kinetic description of the ring current, is included.

The two‐way relationship between ionospheric outflow and the ring current

“…These models all have a thorough history of data‐model validation that demonstrates their ability to reproduce key observed features of the magnetosphere‐ionosphere system. BATS‐R‐US and its associated ionosphere electrodynamics model have repeatedly shown high aptitude for reproducing observed magnetic field about the inner and outer magnetosphere [ Welling and Ridley , ; Rastätter et al , ], field‐aligned current patterns [ Ridley et al , ; Korth et al , ], and the resulting ground‐based perturbations [ Yu and Ridley , ; Pulkkinen et al , ]. The PWOM has demonstrated the ability to reproduce quiet time density and temperature altitude profiles [ Glocer et al , ].…”

“…Using PWOM to drive outflow into BATS‐R‐US has given the latter the ability to reproduce in situ observations of H + and O + densities [ Glocer et al , ] and velocities [ Glocer et al , ]. RAM‐SCB has shown the ability to reproduce the global D s t index [ Rastätter et al , ], large‐scale pressure distributions [ Jordanova et al , ], and in situ magnetic field and fluxes [ Zaharia et al , ; Yu et al , ; Jordanova et al , ; Yu et al , ].…”

Assessing predictive ability of three auroral precipitation models using DMSP energy flux

“…This study used prediction efficiency (PE) as a means of measuring each model's accuracy. Similar studies [ Li et al ., ; Pulkkinen et al ., ; Rastätter et al ., ] have successfully used PE to quantify model accuracy. Prediction efficiency describes the percentage of the variance in an observed data set that is explained by a model.…”

Challenges associated with near‐Earth nightside current

“…For instance, new empirical models have been created that more accurately define the parameter space for these currents [e.g., Tsyganenko , ; Stephens et al ., ]. Several studies have focused on comparisons against the Dst index as a measure of capturing the correctness of near‐Earth currents [e.g., Ganushkina et al ., , ; Cramer et al ., ; Rastätter et al ., ]. Some have investigated the current systems with circuit models of the magnetosphere‐ionosphere system [e.g., Ohtani and Uozumi , ; Patra and Spencer , ].…”