Darren Zeeuw - Academia.edu (original) (raw)
Papers by Darren Zeeuw
The Astrophysical Journal, 2004
The effect of magnetospheric substorms on the ring current is not completely understood. Using a ... more The effect of magnetospheric substorms on the ring current is not completely understood. Using a combination of the University of Michigan's BAT-S-RUS Model and Mei-Ching Fok's Ring Current Model, we will study how substorms can affect the ring current. Using simulated solar wind to drive substorms, we will study the effects of multiple substorms on the ring current. In particular
Using the University of Michigan's BAT-S-RUS Model to drive the Fok Radiation Belt Model,... more Using the University of Michigan's BAT-S-RUS Model to drive the Fok Radiation Belt Model, we will investigate the mechanisms for energy gains in the Earth's inner magnetosphere for recent storms. In addition, using simulated solar wind to drive substorms, we will study the effects of multiple substorms on relativistic electrons. In particular we will compare energy gains due to adiabatic
Using tracing particle analysis we will study possible sources of the cusp energetic particles CE... more Using tracing particle analysis we will study possible sources of the cusp energetic particles CEP observed in the cusp We will employ the University of Michigan BATSRUS global MHD code results as an input for the magnetospheric configuration Different ion species will be also discussed
Ionospheric conductances play a central role in the distribution of electric fields, horizontal c... more Ionospheric conductances play a central role in the distribution of electric fields, horizontal currents and drift patterns driven by the magnetosphere-ionosphere coupling through field-aligned currents (FAC) from the inner magnetosphere. In this study we investigate the impact on an MHD model of the magnetosphere of varying conductance models in an ionospheric potential solver. A statistical model derived from Dynamics Explorer 1 (DE-1) data is used as a basis for the FAC-conductance relation for Hall and Pedersen conductances. The FAC-conductance relation is also determined by the MHD model's spatial resolution near the Earth which limits the amplitude reached by the FAC and increases the width of current gradients compared to observations. This problem can be addressed by generating an empirical relation between spatially averaged currents and conductivities derived from the measurements. This FAC-conductance relation thus compensates for the lack of localized current densities from the MHD model. The impact of that FAC-conductance relation is investigated both in steady-state snapshots and in dynamic (time-dependent) simulations. Of particular interest are the feedbacks on the current system and the energy transfer between magnetosphere and ionosphere with impacts of modeled drift flow patterns in the ionosphere. These results pertain to science-based model validation efforts.
ABSTRACT The Virtual Model Repository (VMR) is a virtual observatory that enables scientific anal... more ABSTRACT The Virtual Model Repository (VMR) is a virtual observatory that enables scientific analysis of numerical models of the Earth's magnetosphere. A variety of model results are made available in a consistent and intuitive way through visualization tools and data/model comparisons. Open access to model output is provided, especially for model output used in support of published papers. The VMR enables browse/search of model output and satellite data for time periods of scientific interest. For example, the large event run library at NASA's Community Coordinated Modeling Center can be browsed and model output compared with a variety of satellite data. Data discovery and exchange is coordinated through various APIs from multiple sites to bring in the relevant data for visualization. A growing set of Michigan SWMF magnetosphere runs are also now available to download and/or visualize with a web graphics interface in 1D, 2D, and 3D.
The effect of magnetospheric substorms on the ring current is not completely understood. Using th... more The effect of magnetospheric substorms on the ring current is not completely understood. Using the BATS-R-US global MHD Model developed by the University of Michigan to drive the Fok Ring Current Model and the Fok Radiation Belt Model, we will explore how substorms affect the ring current and radiation belts. Using real and simulated solar wind data, we will explore
Advances in Space Research, 2005
The in situ measurements of particles and CME transients (IMPACT) investigation on the twin STERE... more The in situ measurements of particles and CME transients (IMPACT) investigation on the twin STEREO spacecraft focuses on the solar energetic particle, solar wind and suprathermal electron, and magnetic field measurements needed to address STEREOÕs goals. IMPACT will provide regular, identical, in situ multipoint measurements bracketing Earth as each spacecraft separates from it at a rate of 22°/yr along EarthÕs orbit. Combined with the PLASTIC and SWAVES investigations, IMPACT fills a critical role in the STEREO quest to connect SECCHIÕs 3D coronal images to their interplanetary consequences.
N umerical simulation and modeling are increasingly essential to basic and applied space-physics ... more N umerical simulation and modeling are increasingly essential to basic and applied space-physics research for two primary reasons. First, the heliosphere and magnetosphere are vast regions of space from which we have relatively few in situ measurements. Numerical simulations let us "stitch together" observations from different regions and provide data-interpretation insight to help us understand this complex system's global behavior. Second, models have evolved to where their physical content and numerical robustness, flexibility, and improving ease of use inspire researchers to apply them to intriguing scenarios with new measures of confidence.
Space Weather
The Space Physics Archive Search and Extract Consortium has developed and implemented the "SPASE ... more The Space Physics Archive Search and Extract Consortium has developed and implemented the "SPASE Data Model" that provides a common language for registering a wide range of Heliophysics (HP) data and other products. The Data Model enables discovery and access tools such that any researcher can obtain data easily, thereby facilitating research, including on space weather. The Data Model includes descriptions of Simulation Models and Numerical Output, pioneered by the Integrated Medium for Planetary Exploration (IMPEx) group in Europe, and subsequently adopted by the Community Coordinated Modeling Center (CCMC). The SPASE group intends to register all relevant Heliophysics data resources, including space-, ground-, and model-based. Substantial progress has been made, especially for space-based observational data and associated observatories, instruments, and display data. Legacy product registrations and access go back more than 50 years. Real-time data will be included. The NASA portion of the SPASE group has funding that assures continuity in the upkeep of the Data Model and aids with adding new products. Tools are being developed for making and editing data descriptions. Digital Object Identifiers (DOIs) for Data Products can now be included in the descriptions. The data access that SPASE facilitates is becoming more uniform and work is progressing on Web Service access via a standard Application Programming Interface. The SPASE Data Model is stable; changes over the past nine years were additions of terms and capabilities that are backward compatible. This paper provides a summary of the history, structure, use, and future of the SPASE Data Model.
ABSTRACT Cross-field current streamline traces through numerical simulation results of various st... more ABSTRACT Cross-field current streamline traces through numerical simulation results of various storm events are presented and discussed. In particular, a comparison of the location and strength of the various near-Earth nightside current systems is made for two events, one driven by an interplanetary coronal mass ejection and another driven by a corotating interaction region/high speed stream. Using results from the Space Weather Modeling Framework, a systematic set of current streamline traces are found from a grid of starting locations in the midnight meridional plane. These current streamlines are then labels according to the current system to which they belong: symmetric ring current, partial ring current, tail current, etc. It is shown that the interpretation of cross-field currents is a difficult task. A single near-tail magnetic field line can be part of a variety of cross field current systems. For example, a field line crossing downtail at R=8 during the main phase of a storm was found to contain partial ring current, symmetric ring current, and tail current simultaneously. Such field lines with multiple currents are common in the near-Earth tail. The occurrence and morphology of the current systems in relation to the magnetic field topology is presented and discussed within the context of two representative ICME and CIR/HSS driven storms.
AIP Conference Proceedings, 2003
The first part of this paper reviews some issues representing major computational challenges for ... more The first part of this paper reviews some issues representing major computational challenges for global MHD models of the space environment. These issues include mathematical formulation and discretization of the governing equations that ensure the proper jump conditions and propagation speeds, regions of relativistic Alfvén speed, and controlling the divergence of the magnetic field. The second part of the paper concentrates on modern solution methods that have been developed by the aerodynamics, applied mathematics and DoE communities. Such methods have recently begun to be implemented in space-physics codes, which solve the governing equations for a compressible magnetized plasma. These techniques include high-resolution upwind schemes, block-based solution-adaptive grids and domain decomposition for parallelization. We describe the space physics MHD code developed at the University of Michigan, based on the developments listed above.
34Th Cospar Scientific Assembly, 2002
ABSTRACT Using the University of Michigan MHD code, we have simulated the magnetospheric and iono... more ABSTRACT Using the University of Michigan MHD code, we have simulated the magnetospheric and ionospheric configuration for a number of different extreme solar wind and interplanetary magnetic field conditions. We have calculated magnetopause standoff distances and bowshock locations for a wide range of solar wind and IMF conditions, and compare these with data-derived models. We examine the saturation of the cross polar cap potential for strongly negative IMF Bz and the influence of the solar wind dynamic pressure on the cross polar cap potential. Lastly, we present results from the 1859 Carrington Event superstorm.
The Astrophysical Journal, 2004
The effect of magnetospheric substorms on the ring current is not completely understood. Using a ... more The effect of magnetospheric substorms on the ring current is not completely understood. Using a combination of the University of Michigan's BAT-S-RUS Model and Mei-Ching Fok's Ring Current Model, we will study how substorms can affect the ring current. Using simulated solar wind to drive substorms, we will study the effects of multiple substorms on the ring current. In particular
Using the University of Michigan's BAT-S-RUS Model to drive the Fok Radiation Belt Model,... more Using the University of Michigan's BAT-S-RUS Model to drive the Fok Radiation Belt Model, we will investigate the mechanisms for energy gains in the Earth's inner magnetosphere for recent storms. In addition, using simulated solar wind to drive substorms, we will study the effects of multiple substorms on relativistic electrons. In particular we will compare energy gains due to adiabatic
Using tracing particle analysis we will study possible sources of the cusp energetic particles CE... more Using tracing particle analysis we will study possible sources of the cusp energetic particles CEP observed in the cusp We will employ the University of Michigan BATSRUS global MHD code results as an input for the magnetospheric configuration Different ion species will be also discussed
Ionospheric conductances play a central role in the distribution of electric fields, horizontal c... more Ionospheric conductances play a central role in the distribution of electric fields, horizontal currents and drift patterns driven by the magnetosphere-ionosphere coupling through field-aligned currents (FAC) from the inner magnetosphere. In this study we investigate the impact on an MHD model of the magnetosphere of varying conductance models in an ionospheric potential solver. A statistical model derived from Dynamics Explorer 1 (DE-1) data is used as a basis for the FAC-conductance relation for Hall and Pedersen conductances. The FAC-conductance relation is also determined by the MHD model's spatial resolution near the Earth which limits the amplitude reached by the FAC and increases the width of current gradients compared to observations. This problem can be addressed by generating an empirical relation between spatially averaged currents and conductivities derived from the measurements. This FAC-conductance relation thus compensates for the lack of localized current densities from the MHD model. The impact of that FAC-conductance relation is investigated both in steady-state snapshots and in dynamic (time-dependent) simulations. Of particular interest are the feedbacks on the current system and the energy transfer between magnetosphere and ionosphere with impacts of modeled drift flow patterns in the ionosphere. These results pertain to science-based model validation efforts.
ABSTRACT The Virtual Model Repository (VMR) is a virtual observatory that enables scientific anal... more ABSTRACT The Virtual Model Repository (VMR) is a virtual observatory that enables scientific analysis of numerical models of the Earth's magnetosphere. A variety of model results are made available in a consistent and intuitive way through visualization tools and data/model comparisons. Open access to model output is provided, especially for model output used in support of published papers. The VMR enables browse/search of model output and satellite data for time periods of scientific interest. For example, the large event run library at NASA's Community Coordinated Modeling Center can be browsed and model output compared with a variety of satellite data. Data discovery and exchange is coordinated through various APIs from multiple sites to bring in the relevant data for visualization. A growing set of Michigan SWMF magnetosphere runs are also now available to download and/or visualize with a web graphics interface in 1D, 2D, and 3D.
The effect of magnetospheric substorms on the ring current is not completely understood. Using th... more The effect of magnetospheric substorms on the ring current is not completely understood. Using the BATS-R-US global MHD Model developed by the University of Michigan to drive the Fok Ring Current Model and the Fok Radiation Belt Model, we will explore how substorms affect the ring current and radiation belts. Using real and simulated solar wind data, we will explore
Advances in Space Research, 2005
The in situ measurements of particles and CME transients (IMPACT) investigation on the twin STERE... more The in situ measurements of particles and CME transients (IMPACT) investigation on the twin STEREO spacecraft focuses on the solar energetic particle, solar wind and suprathermal electron, and magnetic field measurements needed to address STEREOÕs goals. IMPACT will provide regular, identical, in situ multipoint measurements bracketing Earth as each spacecraft separates from it at a rate of 22°/yr along EarthÕs orbit. Combined with the PLASTIC and SWAVES investigations, IMPACT fills a critical role in the STEREO quest to connect SECCHIÕs 3D coronal images to their interplanetary consequences.
N umerical simulation and modeling are increasingly essential to basic and applied space-physics ... more N umerical simulation and modeling are increasingly essential to basic and applied space-physics research for two primary reasons. First, the heliosphere and magnetosphere are vast regions of space from which we have relatively few in situ measurements. Numerical simulations let us "stitch together" observations from different regions and provide data-interpretation insight to help us understand this complex system's global behavior. Second, models have evolved to where their physical content and numerical robustness, flexibility, and improving ease of use inspire researchers to apply them to intriguing scenarios with new measures of confidence.
Space Weather
The Space Physics Archive Search and Extract Consortium has developed and implemented the "SPASE ... more The Space Physics Archive Search and Extract Consortium has developed and implemented the "SPASE Data Model" that provides a common language for registering a wide range of Heliophysics (HP) data and other products. The Data Model enables discovery and access tools such that any researcher can obtain data easily, thereby facilitating research, including on space weather. The Data Model includes descriptions of Simulation Models and Numerical Output, pioneered by the Integrated Medium for Planetary Exploration (IMPEx) group in Europe, and subsequently adopted by the Community Coordinated Modeling Center (CCMC). The SPASE group intends to register all relevant Heliophysics data resources, including space-, ground-, and model-based. Substantial progress has been made, especially for space-based observational data and associated observatories, instruments, and display data. Legacy product registrations and access go back more than 50 years. Real-time data will be included. The NASA portion of the SPASE group has funding that assures continuity in the upkeep of the Data Model and aids with adding new products. Tools are being developed for making and editing data descriptions. Digital Object Identifiers (DOIs) for Data Products can now be included in the descriptions. The data access that SPASE facilitates is becoming more uniform and work is progressing on Web Service access via a standard Application Programming Interface. The SPASE Data Model is stable; changes over the past nine years were additions of terms and capabilities that are backward compatible. This paper provides a summary of the history, structure, use, and future of the SPASE Data Model.
ABSTRACT Cross-field current streamline traces through numerical simulation results of various st... more ABSTRACT Cross-field current streamline traces through numerical simulation results of various storm events are presented and discussed. In particular, a comparison of the location and strength of the various near-Earth nightside current systems is made for two events, one driven by an interplanetary coronal mass ejection and another driven by a corotating interaction region/high speed stream. Using results from the Space Weather Modeling Framework, a systematic set of current streamline traces are found from a grid of starting locations in the midnight meridional plane. These current streamlines are then labels according to the current system to which they belong: symmetric ring current, partial ring current, tail current, etc. It is shown that the interpretation of cross-field currents is a difficult task. A single near-tail magnetic field line can be part of a variety of cross field current systems. For example, a field line crossing downtail at R=8 during the main phase of a storm was found to contain partial ring current, symmetric ring current, and tail current simultaneously. Such field lines with multiple currents are common in the near-Earth tail. The occurrence and morphology of the current systems in relation to the magnetic field topology is presented and discussed within the context of two representative ICME and CIR/HSS driven storms.
AIP Conference Proceedings, 2003
The first part of this paper reviews some issues representing major computational challenges for ... more The first part of this paper reviews some issues representing major computational challenges for global MHD models of the space environment. These issues include mathematical formulation and discretization of the governing equations that ensure the proper jump conditions and propagation speeds, regions of relativistic Alfvén speed, and controlling the divergence of the magnetic field. The second part of the paper concentrates on modern solution methods that have been developed by the aerodynamics, applied mathematics and DoE communities. Such methods have recently begun to be implemented in space-physics codes, which solve the governing equations for a compressible magnetized plasma. These techniques include high-resolution upwind schemes, block-based solution-adaptive grids and domain decomposition for parallelization. We describe the space physics MHD code developed at the University of Michigan, based on the developments listed above.
34Th Cospar Scientific Assembly, 2002
ABSTRACT Using the University of Michigan MHD code, we have simulated the magnetospheric and iono... more ABSTRACT Using the University of Michigan MHD code, we have simulated the magnetospheric and ionospheric configuration for a number of different extreme solar wind and interplanetary magnetic field conditions. We have calculated magnetopause standoff distances and bowshock locations for a wide range of solar wind and IMF conditions, and compare these with data-derived models. We examine the saturation of the cross polar cap potential for strongly negative IMF Bz and the influence of the solar wind dynamic pressure on the cross polar cap potential. Lastly, we present results from the 1859 Carrington Event superstorm.