Robert Weigel

Robert Weigel
George Mason University | GMU · Department of Physics and Astronomy

PhD

About

124
Publications
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1,409
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Publications

Publications (124)
Article
Full-text available
We present results of a global survey of single-pixel intensity power spectra from a 12-hour time period on June 26, 2013 in a 1600x1600 pixel region from five channels of the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) instrument. We extract single-pixel time series from a derotated image sequence, fit models to the power s...
Article
This paper is the primary deliverable of the very first NASA Living With a Star Institute Working Group, Geomagnetically Induced Currents (GIC) Working Group. The paper provides a broad overview of the current status and future challenges pertaining to the science, engineering, and applications of the GIC problem. Science is understood here as the...
Article
The geoelectric field is the primary input used for estimation of geomagnetically induced currents (GICs) in conducting systems. We compare three methods for estimating the geoelectric field given the measured geomagnetic field at four locations in the U.S. during time intervals with average Kp in the range of 2–3 and when the measurements had few...
Article
We consider two types of events, identified by decreases in Dst below a threshold value and increases in the equatorial mass density at geosynchronous altitudes, ρeq, above a threshold value using the Takahashi et al. (2010) data set. From the Dst events and 1 day averages, we find that there is a statistically weak and small-amplitude difference b...
Article
We present the latest result of a community-wide space weather model validation effort coordinated among the Community Coordinated Modeling Center (CCMC), NOAA Space Weather Prediction Center (SWPC), model developers, and the broader science community. Validation of geospace models is a critical activity for both building confidence in the science...
Article
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We introduce new quantities for exploratory causal inference between bivariate time series. The quantities, called penchants and leanings, are computationally straightforward to apply, follow directly from assumptions of probabilistic causality, do not depend on any assumed models for the time series generating process, and do not rely on any embed...
Data
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Article
The upper atmosphere changes significantly in temperature, density and composition as a result of solar cycle variations, which causes severe storms and flares, and increases in the amount of absorbed solar radiation from solar energetic events. Satellite orbits are consequently affected by this process, especially those in low Earth orbit (LEO). I...
Article
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Convergent Cross-Mapping (CCM) is a technique for computing specific kinds of correlations between sets of times series. It was introduced by Sugihara et al. and is reported to be "a necessary condition for causation" capable of distinguishing causality from standard correlation. We show that the relationships between CCM correlations proposed in \...
Article
[1] In this paper we continue the community-wide rigorous modern space weather model validation efforts carried out within GEM, CEDAR and SHINE programs. In this particular effort, in coordination among the Community Coordinated Modeling Center (CCMC), NOAA Space Weather Prediction Center (SWPC), modelers, and science community, we focus on studyin...
Article
This paper reports the metrics-based results of the Dst index part of the 2008-2009 GEM Metrics Challenge. The 2008-2009 GEM Metrics Challenge asked modelers to submit results for four geomagnetic storm events and five different types of observations that can be modeled by statistical, climatological or physics-based models of the magnetosphere-ion...
Article
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We describe an algorithm for intracalibration of measurements from plasma or energetic particle detectors on a three-axis stabilized platform. Modeling and forecasting of Earth's radiation belt environment requires data from particle instruments, and these data depend on measurements which have an inherent calibration uncertainty. Pre-launch calibr...
Article
Within the domain of Heliophysics, data discovery is being actively addressed. However, data diversity in the returned results has proven to be a significant barrier to integrated multi-mission analysis. Software is being actively developed (e.g. Vandergriff and Brown, 2008) that is data format and measurement type agnostic. However, such approache...
Article
The Service Environment for Enhanced Knowledge and Research (SEEKR) Framework is a configurable service oriented framework to enable the discovery, access and analysis of data shared in a community. The SEEKR framework integrates many existing independent services through the use of web technologies and standard metadata. Services are hosted on sys...
Article
Los Alamos is leading the Science Operations Center (SOC) for the Energetic Particle, Composition, and Thermal Plasma Suite (ECT) for NASA's upcoming Radiation Belt Storm Probe Mission (RBSP). This paper will present the ECT team's plans for making data available to both the ECT team and the public. The ECT-SOC will make extensive use of resources...
Article
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1] Acquiring quantitative metricsbased knowledge about the performance of various space physics modeling approaches is central for the space weather community. Quantification of the performance helps the users of the modeling products to better understand the capabilities of the models and to choose the approach that best suits their specific needs...
Article
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In his Forum, P. Vermeesch (Eos, 90(47), 443, doi:10.1029/2009EO470004, 2009) argues that ``the strong dependence of p values on sample size makes them uninterpretable'' with an example where p values in a hypothesis test using Pearson's chi-square statistic differed by a factor of 1016 when the sample size decreased tenfold. The data were a sequen...
Article
The Virtual Model Repository is a virtual observatory that enables scientific analysis of complex computation models by facilitating visualization of model output and brings in observational data for data/model comparisons. It enables browse/search of model output and satellite data for time periods of scientific interest. For example, the large ev...
Article
Autoplot is software for plotting data from many different sources and in many different formats. All data is converted to a common data model before plotting. It is used in the Heliophysics Data Environment as a plotting tool that is easily interfaced to websites, but also as a uniform way to bring data into environments like IDL and Matlab. It al...
Article
Cloud computing offers a scalable on-demand resource allocation model to evolving needs in data intensive geophysical applications, where computational needs in CPU and storage can vary over time depending on modeling or field campaign. Separate, sometimes incompatible cloud platforms and services are already available from major computing vendors...
Article
ViRBO (Virtual Radiation Belt Observatory) is one of the domain-specific virtual observatories funded under the NASA Heliophysics Data Environment (HPDE) program that began development in 2006. In this work, we report on the search, display, and data access functionality of ViRBO along with plans for interaction with upcoming missions, including Ra...
Article
Full-text available
Solar wind density has been argued to have a strong effect on geomagnetic storms. Elevated solar wind density tends to occur in time intervals when the solar wind electric field is large. This complicates the analysis required to identify a solar wind density influence because the solar wind electric field is the dominant driver of geomagnetic stor...
Article
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Time Series Data Server (TSDS) is a software package for implementing a server that provides fast super-setting, sub-setting, filtering, and uniform gridding of time series-like data. TSDS was developed to respond quickly to requests for long time spans of data. Data may be served from a fast database, typically created by aggregating granules (e.g...
Article
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The recent Heliophysics Virtual Observatory (VxO) effort involves the development of separate observatories with a low overlap in physical domain or area of scientific specialization and a high degree of overlap in metadata management needs. VxOware is a content and metadata management system. While it is intended for use by a VxO specifically, it...
Article
Full-text available
Autoplot is software developed for the Virtual Observatories in Heliophysics to provide intelligent and automated plotting capabilities for many typical data products that are stored in a variety of file formats or databases. Autoplot has proven to be a flexible tool for exploring, accessing, and viewing data resources as typically found on the web...
Article
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Autoplot is software for plotting and manipulating data sets that come from a variety of sources and applications, and a flexible interface for representing data has been developed. QDataSet is the name for the "data model" which has evolved over a decade from previous models implemented by the author. A "data model" is similar to a "metadata model...
Article
Five years ago, the NASA Living with a Star program funded a group of Virtual Observatories intended to ``integrate data and models across many missions, data centers, agencies and countries''. Each observatory was designed to meet the unique needs of specific heliophysics research communities. One of the observatories funded under this program, th...
Article
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A variety of observations have shown strong seasonal variations in an array of magnetosphere-ionosphere parameters, including field-aligned currents, cross polar cap potential, and precipitating electron energy flux. In this presentation we examine how these variations are modeled in the Lyon-Fedder-Mobarry (LFM) global scale magnetohydrodynamic (M...
Article
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Scientific satellites, balloons, ground-based instruments, and other observational platforms are producing rich streams of data about the Earth and space. Ensuring widespread access to such data has led to the development of a new type of observatory: the virtual observatory. Existing only in cyberspace, virtual observatories are Web-based interfac...
Article
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On 28 September 2009, a space weather forecasting contest will be initiated at http://swxcontest.gmu.edu/. This contest, sponsored by the Space Weather Laboratory at George Mason University, in Fairfax, Va., is intended to bring space weather to a broader community by allowing interested students and researchers to get hands-on experience with spac...
Conference Paper
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We describe the new undergraduate science degree program in Computational and Data Sciences (CDS) at George Mason University (Mason), which began offering courses for both major (B.S.) and minor degrees in Spring 2008. The overarching theme and goal of the program are to train the next-generation scientists in the tools and techniques of cyber-enab...
Article
Full-text available
1] A variety of observations have shown strong seasonal variations in a vast array of magnetosphere-ionosphere parameters, including field-aligned currents, cross polar cap potential, and precipitating electron energy flux. In this paper we examine how these variations are modeled in the Lyon-Fedder-Mobarry (LFM) global-scale magnetohydrodynamic si...
Article
The first major release of the Virtual Radiation Belt Observatory (ViRBO) is presented. ViRBO is a virtual observatory which allows access to and use of data and tools for radiation belt scientists. Data sets include data from the SAMPEX, GOES, POES, LANL GEO, Polar, and GPS satellites. A number of new data sets, not previously available, are avail...
Article
Autoplot (www.autoplot.org) is software for plotting data from many different sources and in many different file formats. Data from CDF, CEF, Fits, NetCDF, and OpenDAP can be plotted, along with many other sources such as ASCII tables and Excel spreadsheets. This is done by adapting these various data formats and APIs into a common data model that...
Article
During the passage of solar wind high-speed streams, normally characterized by a weak IMF, historic observations [e.g. Rostoker et al., JGR 1998] have shown that a peak of both ULF wave power and electron flux is formed at high L (5-6), measurable from geosynchronous orbit (6.6). Recurrence of the streams leads to a driven oscillation in the magnet...
Article
The Virtual Radiation Belt Observatory (ViRBO) has synthesized a large collection of data and tools relevant to radiation belt science including instrument data, scientist-contributed model data, and analysis software. Instrument data from the SAMPEX, GOES, POES, LANL GEO, Polar, and GPS satellites are all available from a common interface. Scienti...
Article
The heliophysics community is presenting at this meeting the results of the development of a number of virtual observatories that have been funded by NASA to provide data access for various subdisciplines (magnetospheres. ionospheres, cosmic rays, radiation belts, etc.) within the realm of heliophysics. For users in one subdiscipline to determine w...
Article
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Although space weather is modeled after tropospheric weather, both in its conception as a weather system and in our efforts to forecast it, no capability exists today for assimilating magnetospheric data into space weather simulations. In this paper a scheme is proposed for assimilating magnetospheric data into a global MHD code. The scheme is simi...
Article
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1] The day-of-year (DOY) variation in the average value of a solar wind driver of geomagnetic activity has been shown to explain only a minority of the observed amplitude of DOY variation in geomagnetic activity. The proxies for solar wind driving used to show this are averages of a solar wind measurement in the same hour or 3-hour interval as the...
Article
One main objective of the Center for Integrated Space Weather Modeling (CISM) is to develop forecast models (FM) for the Sun-Earth chain, and to mature them close to the operational stage. The Sun-Earth chain comprises empirical and physical models. Among the former is the Planetary Equivalent Amplitude FM with a 1 to 7 day prediction of the daily...
Article
Several research groups are presently modeling key portions of the solar–terrestrial environment. Large-scale models of the solar corona, of the interplanetary medium, and of the coupled magnetosphere–ionosphere system are providing important insights into the dynamics and temporal evolution of these regions during normal, as well as disturbed, con...
Article
It has been known for quite some time that there exists significant seasonal variation in activity within the coupled magnetosphere - ionosphere system. Crooker and Siscoe have proposed a mechacism whcih it explains the variation due to the role of the Earth's dipole tilt in regulating the effecency of energy transfer at the magnetopause. Recently,...
Article
The Virtual Radiation Belt Observatory (ViRBO) is part of the new VxO infrastructure being developed to support Heliophysics research. Though focused specifically on the data and physics of the Earth's radiation belts its development has revealed patterns for scientific data sharing that are relevant across the VxO domain. We will present a discuss...
Article
A significant fraction of magnetospheric and geomagnetic activity is a direct result of variations in the external solar wind energy input, which fluctuates on time scales that are similar to the time scales of internal magnetospheric phenomena. To isolate the part of the magnetospheric activity signal that is due to internal magnetospheric process...
Article
We present a time-dependent model for the energetic electron flux in Earth's radiation belts developed from measurements by several spacecraft in the radiation belts (POLAR, SAMPEX, Akebono, HEO, and GOES) and the solar wind (ACE, WIND). The flux is a function of L shell (1-11), particle energy (0.8-6.4 MeV) and time. A different module is develope...
Article
First results are presented of the space weather forecasting capability of the real-time WINDMI model that has been operating since February 2006 as a physics based AL and Dst prediction tool. The well documented WINDMI model is a network of eight coupled ordinary differential equations which describe the transfer of power from the solar wind throu...
Article
Full-text available
Several basic results from decision theory as applied to rare event forecasts are reviewed, and an alternative method for comparing rare event forecasts is presented. A fundamental result is that for a large class of users only interested in economic utility, the relevant performance quantity is the number of correct and false alarm forecasts. This...
Chapter
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Since the early 1990s a series of spacecraft missions have completely transformed our view of the electron radiation belts. This paper summarizes a number of new results on the structure and dynamics of the belts obtained from those measurements. First, the structure of the outer electron belt is discussed with emphasis on the regions (P0-P2) disti...
Article
We present a simple yet numerically robust technique, using autoregressive linear filters, to remove unwanted "col-ored noise" from solar wind and radiation belt electron data at sub-daily resolution. The remaining signal is then studied using finite impulse response linear prediction filters to represent the driven portion of the linear dynamics t...
Article
This chapter reviews the three types of models of geomagnetic activity, based on the concepts of dynamical chaos, self-organized criticality, and non-equilibrium phase transition physics. These concepts are shown to provide important new techniques improving the simplest approach to modeling solar wind-magnetosphere interactions based on linear fil...
Article
The CISM Data Explorer is a modular but integrated collection of data, models, and tools for analysis and visualization that is targeted for use by space physics researchers and students. It relies on integrated libraries, programs, and examples written in OpenDX, Octave, Perl, C, and FORTRAN. This project began in response to a need to simplify mo...
Article
Full-text available
1] Among the many challenges facing space physics today is the need for an analysis and visualization package which can examine the results from numerical and empirical models as well as observational data. In this paper we introduce the CISM-DX package as a possible answer to this problem. We have created a tool which is capable of completing high...
Article
Linear state-space models offer a compact and flexible data-derived dynamical modeling framework for describing the coupled multi-output linear response of geophysical systems like the Earth's electron radiation belts. Unlike more traditional finite impulse response (FIR) linear filters, they effectively separate external perturbations from interna...
Article
A model for the time-dependence of the high-latitude ground magnetic field and its time rate of change, dB/dt, is presented. The model coefficients are computed at an annular grid from magnetic field measurements from the IMAGE meridional array. The nonlinear response at high activity is represented by a local-linear model. The magnetic field model...
Article
The Dst historically has been used as a measure of the disturbance of the magnetosphere and an indicator of when a geomagnetic storm is occuring. The Temerin-Li [2002] (TL02) model is a semi-empirical Dst model which was trained on five years (1995 - 1999) of data. The TL02 model is the most successful Dst predictor in terms of prediction efficienc...
Article
Several prior studies have suggested the solar wind velocity acts as a driver for the relativistic electron flux in the radiation belts. In this study, time series of ACE solar wind velocity measurements are included along with past electron flux measurements from SAMPEX in order to predict future electron flux. Since previous flux measurements are...
Article
Linear state-space models, most common in engineering applications, offer a more flexible alternative to the familiar finite impulse response (FIR) linear prediction filters commonly used to predict radiation belt electron fluxes based on solar wind input. They can be designed to be mathematically equivalent to FIR models, but may also incorporate...
Article
We introduce the CISM Data Explorer: a collection of data, models, and tools for analysis and visualization, to be used by space physics researchers and students. It relies heavily on well--documented programs and examples written in OpenDX, Octave, Perl, C, and FORTRAN. This project began in response to a need to simplify model (both empirical and...
Article
Within the CISM project empirical models serve as baselines against which to monitor the increase in predictive skill of physics-based numerical codes as they advance. Empirical models also establish a suite of forecast models from which to evolve toward greater forecast accuracy by incorporating numerical codes as they advance enough to increase f...
Article
Metrics and model validation represent two key elements upon which the success of the Center for Integrated Space Weather Modeling (CISM) hinges. The routine calculation of important operationally- and scientifically-motivated metrics permits us to objectively measure and track the ability of coupled CISM models to predict essential space weather q...
Article
High fluxes of relativistic electrons in the inner magnetosphere have been associated with a range of spacecraft anomalies, and therefore the modeling of the flux is of direct relevance to the development of space weather applications. Time variations of the electron flux at a given L shell are ultimately functions of interplanetary parameters as w...
Article
The Wang–Sheeley–Arge (WSA) method is used to predict the solar wind speed (and certain other parameters) near the Earth's orbit based upon solar surface measurements. This approach gives a predicted solar wind time series with a lead time of three to four days. Such forecasted solar wind conditions can then be convolved with linear and nonlinear f...
Article
Full-text available
We test the ability of a data-derived model of geomagnetic activity, originally optimized to have a high prediction efficiency (PE), for its ability to predict only large geomagnetic disturbances. Correlation-based metrics, such as prediction efficiency, are often used as a measure of model performance. This metric puts equal weight on prediction o...
Article
Linear autoregressive (AR) processes have modeled many natural systems successfully. In this study, fourth and sixth order Kalman filters were used to identify the coefficients in time series of relativistic electron flux measurements in the region 1
Article
Long records of geomagnetic measurements allow for many studies to be carried out that are not possible using data from a few events or by using geomagnetic indices. We present examples of using longer-than 5 year records of magnetometer data along with L1 solar wind measurements to determine (1) the spatial distribution of the predictability of gr...
Article
Full-text available
Prior studies have examined the time-stationary (and quasi-stationary) dynamic response of relativistic electrons in the Earth's outer radiation belt to changes in solar wind bulk speed using linear prediction filters [Baker et al., 1990; Vassiliadis et al., 2002]. For this study, we have implemented an adaptive system identification scheme, based...
Article
Metrics and model validation represent two key elements upon which the success of the Center for Integrated Spaceweather Modeling (CISM) hinges. The routine calculation of important operationally- and scientifically-motivated metrics permits us to objectively measure and track the ability of coupled CISM models to predict essential space weather qu...
Article
Relativistic electrons pose a significant threat to satellites in a variety of orbital configurations in the form of deep dielectric charging within vital electronic subsystems. Accurate specification and short-term predictions of radiation belt electron flux variability can serve as useful tools to mitigate such detrimental, and potentially expens...
Article
An important space weather threat is associated with very high energy electrons trapped in Earth's outer Van Allen zone. Past work has shown that radiation belt electron fluxes are highly dependent on the solar wind speed (VSW). Generally, when VSW. goes above 500km/s, the radiation belt electron fluxes increase substantially. We have used the Wang...
Article
Full-text available
An analysis of large-amplitude relativistic electron fluxes, Je, is given using models that predict their appearance based on solar wind precursors. It has been noted that relativistic electron flux bursts in the magnetosphere are associated with high-speed solar wind streams. This observation is used to motivate several models that quantify the as...
Article
Full-text available
A statistical model of short time-scale geomagnetic fluctuations is developed and used to evaluate how geomagnetic dynamics are influenced by different solar wind controlling parameters. The functional form of the probability distribution function (PDF) that describes extreme-value (greater than 4σ) minute-to-minute changes in the ground magnetic f...