Browsing by Author "Schunk, R. W."
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Item Restricted CEDAR Electrodynamics Thermosphere Ionosphere (ETI) Challenge for systematic assessment of ionosphere/thermosphere models: NmF2, hmF2, and vertical drift using ground‐based observations(American Geophysical Union, 2011-12-31) Shim, J. S.; Kuznetsova, M.; Rastätter, L.; Hesse, M.; Bilitza, D.; Butala, M.; Codrescu, M.; Emery, B.; Foster, B.; Fuller-Rowell, T.; Huba, J.; Mannucci, A. J.; Pi, X.; Ridley, A.; Scherliess, L.; Schunk, R. W.; Stephens, P.; Thompson, D. C.; Zhu, L.; Anderson, D.; Chau Chong Shing, Jorge Luis; Sojka, J. J.; Rideout, B.Objective quantification of model performance based on metrics helps us evaluate the current state of space physics modeling capability, address differences among various modeling approaches, and track model improvements over time. The Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) Electrodynamics Thermosphere Ionosphere (ETI) Challenge was initiated in 2009 to assess accuracy of various ionosphere/thermosphere models in reproducing ionosphere and thermosphere parameters. A total of nine events and five physical parameters were selected to compare between model outputs and observations. The nine events included two strong and one moderate geomagnetic storm events from GEM Challenge events and three moderate storms and three quiet periods from the first half of the International Polar Year (IPY) campaign, which lasted for 2 years, from March 2007 to March 2009. The five physical parameters selected were NmF2 and hmF2 from ISRs and LEO satellites such as CHAMP and COSMIC, vertical drifts at Jicamarca, and electron and neutral densities along the track of the CHAMP satellite. For this study, four different metrics and up to 10 models were used. In this paper, we focus on preliminary results of the study using ground‐based measurements, which include NmF2 and hmF2 from Incoherent Scatter Radars (ISRs), and vertical drifts at Jicamarca. The results show that the model performance strongly depends on the type of metrics used, and thus no model is ranked top for all used metrics. The analysis further indicates that performance of the model also varies with latitude and geomagnetic activity level.Item Restricted Ensemble Modeling with Data Assimilation Models: A New Strategy for Space Weather Specifications, Forecasts, and Science(American Geophysical Union, 2014-02-23) Schunk, R. W.; Scherliess, L.; Eccles, V.; Gardner, L. C.; Sojka, J. J.; Zhu, L.; Pi, X.; Mannucci, A. J.; Wilson, B. D.; Komjathy, A.; Wang, C.; Rosen, G.The Earth’s Ionosphere-Thermosphere-Electrodynamics (I-T-E) system varies markedly on a range of spatial and temporal scales and these variations have adverse effects on human operations and systems, including high-frequency communications, over-the-horizon radars, and survey and navigation systems that use Global Positioning System (GPS) satellites. Consequently, there is a need to elucidate the underlying physical processes that lead to space weather disturbances and to both mitigate and forecast near-Earth space weather. The meteorologists and oceanographers have shown that data assimilation models are superior to global physics-based models for specifications and forecasts, but only during the last 15 years have they been used for near-Earth investigations as more global (space and ground-based) measurements became available. Although data assimilation models produce better specifications and forecasts than global physicsbased models, there is still a spread in results for a given simulation scenario when different data assimilation models are used. This spread occurs because the different data assimilation models use different data types, data amounts, assimilation techniques, and background physics-based models. This data assimilation issue is being addressed with the launching of the “NASA/NSF Space Weather Modeling Collaboration” program. Currently, our team has seven physics-based data assimilation models for the ionosphere, plasmasphere, thermosphere, and electrodynamics. These models assimilate a myriad of different ground- and space-based observations, and there is more than one data assimilation model for each near-Earth space domain. These data assimilation models are being used to create a Multimodel Ensemble Prediction System (MEPS), which will allow ensemble modeling of the I-T-E system with different data assimilation models that are based on different physical assumptions, assimilation techniques, and initial conditions. The application of ensemble modeling with several different data assimilation models will lead to a paradigm shift in how basic physical processes are studied in near-Earth space, and it is expected to lead to a significant advance in space weather specifications and forecasts.Item Open Access Sundial: A world-wide study of interactive ionospheric processes and their roles in the transfer of energy and mass in the sunearth system(European Geosciences Union, 1988-01-01) Szuszczewicz, E. P.; Fejer, B. Q.; Roelof, E. C.; Schunk, R. W.; Leitinger, R.; Abdu, M. A.; Reddy, B. M.; Joselyn, J. C.; Wilkinson, P.; Woodman Pollitt, Ronald Francisco; Wolf, R. A.During the period 5-13 October 1984 a coordinated solar-terrestrial data base was acquired to develop a comprehensive understanding and an associated predictive capability for the cause-effect relationships which control the global-scale ionosphere. The effort, the first in a series of continuing investigations in a program called SUNDIAL, combined modelling of the ionospheric, magnetospheric, and thermospheric domains with a measurements activity that included a network of ionospheric monitoring stations at high-, middle-, and low latitudes in the American, European/African, and Asian/Australian sectors. Solar, solar wind, interplanetary, and geomagnetic data were also obtained through the NOAA Space Environment Services Center. The period began with nearly two full days of typically quiescent solar mínimum conditions, with the night of the 6th marking a transition to a substantial increase in solar wind velocities, and enhanced dynamics in the interplanetary magnetic field with associated geomagnetic disturbances. The increased solar wind velocities resulted from a corotating high-speed stream coupled to a transequatorial solar coronal hole. Evidence points to a step-wise coupling of processes from the coronal hole through the interplanetary and magnetospheric domains down to the equatorial ionosphere, where penetrating electric fields participated in triggering the most disturbed condition of equatorial spread-F ever recorded by the Jicamarca Observatory. The correlation of events also included : (1) enhanced particle precipitation power at high latitudes, (2) an associated cross polar cap potential of 75 k Y, and (3) simultaneous global observations of F-region dynamics. In addition, detailed model comparisons with observations of the quiet and disturbed ionosphere point to requirements for improved global specification of thermospheric winds and electric fields. The content of this paper presents an overview of the program, its initial findings, recommendations, and future perspectives.