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  • 1
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    Three-dimensional MHD simulation of the evolution of the April 2000 CME event and its induced shocks using a magnetized plasma blob model (2011)
    Wiley
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    Publication Date: 2011-04-01
    Description: A three-dimensional (3-D) time-dependent, numerical magnetohydrodynamic (MHD) model with asynchronous and parallel time-marching method is used to investigate the propagation of coronal mass ejections (CMEs) in the nonhomogenous background solar wind flow. The background solar wind is constructed based on the self-consistent source surface with observed line-of-sight of magnetic field and density from the source surface of 2.5 Rs to the Earth's orbit (215 Rs) and beyond. The CMEs are simulated by means of a very simple flux rope model: a high-density, high-velocity, and high-temperature magnetized plasma blob is superimposed on a steady state background solar wind with an initial launch direction. The dynamical interaction of a CME with the background solar wind flow between 2.5 and 220 Rs is investigated. The evolution of the physical parameters at the cobpoint, which is located at the shock front region magnetically connected to ACE spacecraft, is also investigated. We have chosen the well-defined halo-CME event of 4–6 April 2000 as a test case. In this validation study we find that this 3-D MHD model, with the asynchronous and parallel time-marching method, the self-consistent source surface as initial boundary conditions, and the simple flux rope as CME model, provide a relatively satisfactory comparison with the ACE spacecraft observations at the L1 point.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Using a 3-D spherical plasmoid to interpret the Sun-to-Earth propagation of the 4 November 1997 coronal mass ejection event (2012)
    Wiley
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    Publication Date: 2012-01-10
    Description: We present the time-dependent propagation of a Sun-Earth connection event that occurred on 4 November 1997 using a three-dimensional (3-D) numerical magnetohydrodynamics (MHD) simulation. A global steady state solar wind for this event is obtained by a 3-D SIP-CESE MHD model with Parker's 1-D solar wind solution and measured photospheric magnetic fields as the initial values. Then, superposed on the quiet background solar wind, a spherical plasmoid is used to mimic the 4 November 1997 coronal mass ejection (CME) event. The CME is assumed to arise from the evolution of a spheromak magnetic structure with high-speed, high-pressure, and high-plasma-density plasmoid near the Sun. Moreover, the axis of the initial simulated CME is put at S14W34 to conform to the observed location of this flare/CME event. The result has provided us with a relatively satisfactory comparison with the Wind spacecraft observations, such as southward interplanetary magnetic field and large-scale smooth rotation of the magnetic field associated with the CME.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Forward Modeling and Optimization of Methane Emissions in the South Central United States Using Aircraft Transects Across Frontal Boundaries (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract The South Central United States is a hot spot for anthropogenic methane (CH4) emissions, with contributions from the oil/gas (O&G) and animal agriculture sectors. During frontal weather events, airflow combines enhancements from these emissions into a large plume. In this study, we take CH4 and ethane (C2H6) observations from the Atmospheric Carbon and Transport‐America campaign and adjust O&G and animal agriculture emissions such that modeled CH4 and C2H6 enhancements match the observed plume. Results from the joint CH4‐C2H6 optimization indicate that emissions from the O&G sector are 1.8 ± 0.7 (2σ) times larger than EPA inventory estimates. These results match synthesis work from recent literature and reject the possibility that this increase compared to inventories is due to a potential bias in daytime‐only measurements of these facilities. Successful modeling from this study raises the possibility of using trace gas measurements along frontal crossings to solve for emissions in other regions of the United States.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    Time-dependent MHD modeling of the global solar corona for year 2007: Driven by daily-updated magnetic field synoptic data (2012)
    Wiley
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    Publication Date: 2012-08-28
    Description: In this paper, we develop a time-dependent MHD model driven by the daily-updated synoptic magnetograms (MHD-DUSM) to study the dynamic evolution of the global corona with the help of the 3D Solar-Interplanetary (SIP) adaptive mesh refinement (AMR) space-time conservation element and solution element (CESE) MHD model (SIP-AMR-CESE MHD Model). To accommodate the observations, the tangential component of the electric field at the lower boundary is specified to allow the flux evolution to match the observed changes of magnetic field. Meanwhile, the time-dependent solar surface boundary conditions derived from the method of characteristics and the mass flux limit are incorporated to couple the observation and the 3D MHD model. The simulated evolution of the global coronal structure during 2007 is compared with solar observations and solar wind measurements from both Ulysses and spacecrafts near the Earth. The MHD-DUSM model is also validated by comparisons with the standard potential field source surface (PFSS) model, the newly improved Wang-Sheeley-Arge (WSA) empirical formula, and the MHD simulation with a monthly synoptic magnetogram (MHD-MSM). Comparisons show that the MHD-DUSM results have good overall agreement with coronal and interplanetary structures, including the sizes and distributions of coronal holes, the positions and shapes of the streamer belts, and the transitions of the solar wind speeds and magnetic field polarities. The MHD-DUSM results also display many features different from those of the PFSS, the WSA, and the MHD-MSM models.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 5
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    MHD numerical study of the latitudinal deflection of coronal mass ejection (2013)
    Wiley
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    Publication Date: 2013-10-13
    Description: [1]  In this paper, we analyze and quantitatively study the deflection of CME in the latitudinal direction during its propagation from the Corona to interplanetary (IP) space using a three-dimensional (3D) numerical magnetohydrodynamics (MHD) simulation. To this end, 12 May 1997 CME event during the Carrington rotation 1922 is selected. Firstly, we try to reproduce the physical properties for this halo CME event observed by the WIND spacecraft. Then, we study the deflection of CME, and quantify the effect of the background magnetic field and the initiation parameters (such as the initial magnetic polarity and the parameters of the CME model) on the latitudinal deflection of CMEs. The simulations show that the initial magnetic polarity substantially affects the evolution of CMEs. The “parallel" CMEs (with the CME's initial magnetic field parallel to that of the ambient field) originating from high latitude show a clear Equator-ward deflection at the beginning, and then propagate almost parallel to heliospheric current sheet (HCS), and the “anti-parallel" CMEs (with the CME's initial magnetic field opposite to that of the ambient field) deflect toward the pole. Our results demonstrate that the latitudinal deflection extent of the “parallel" CMEs is not only mainly controlled by the background magnetic field strength, but also by the initial magnetic field strength of the CMEs. There is an anti-correlation between the latitudinal deflection extent and the CME average transit speed and the energy ratio E cme / E sw .
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 6
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    Shock propagation model version-2 (SPM2) and its application in predicting the arrivals at Earth of interplanetary shocks during Solar Cycle 23 (2013)
    Wiley
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    Publication Date: 2013-12-13
    Description: [1]  The Shock Propagation Model (SPM) based on an analytic solution of blast waves has been proposed [Feng and Zhao, 2006] to predict shock arrival times (SATs) at Earth. Here to reduce the limitations of the SPM theoretical model in real applications and optimize its input parameters, a new version (called SPM2) is presented in order to enhance prediction performance. First, an empirical relationship is established to adjust the initial shock speed, which, as computed from the Type II burst drift rate, often contains observational uncertainties. Second, an additional acceleration/deceleration relation is added to the model to eliminate inherent prediction bias. Third, the propagation direction is derived in order to mitigate the isotropy limitation of blast wave theory in real predictions. Finally, an equivalent shock strength index (ESSI) at the Earth's location to judge whether or not an interplanetary (IP) shock will encounter the Earth is implemented in SPM2. The prediction results of SPM2 for 551 solar disturbance events of Solar Cycle 23 demonstrate that the success rate of SPM2 for both shock (W-shock) and non-shock (W/O-shock) events at Earth is ∼ 60%. The prediction error for the W-shock events is less than 12 hours (root-mean-square) and 10 hours (mean-absolute), respectively. Comparisons between the predicted results of SPM2 and those of STOA, ISPM and HAFv.2 based on similar data samples reveal that the SPM2 model offers generally equivalent prediction accuracy and reliability compared to the existing Fearless Forecast models (STOA, ISPM and HAFv.2).
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 7
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    Three-dimensional MHD simulation of two coronal mass ejections' propagation and interaction using a successive magnetized plasma blobs model (2011)
    Wiley
    Details
    Publication Date: 2011-09-24
    Description: A three-dimensional (3-D), time-dependent, numerical magnetohydrodynamic (MHD) model is used to investigate the evolution and interaction of two coronal mass ejections (CMEs) in the nonhomogeneous ambient solar wind. The background solar wind is constructed on the basis of the self-consistent source surface with observed line of sight of magnetic field and density from the source surface of 2.5 Rs to Earth's orbit (215 Rs) and beyond. The two successive CMEs occurring on 28 March 2001 and forming a multiple magnetic cloud in interplanetary space are chosen as a test case, in which they are simulated by means of a two high-density, high-velocity, and high-temperature magnetized plasma blobs model, and are successively ejected into the nonhomogeneous background solar wind medium along different initial launch directions. The dynamical propagation and interaction of the two CMEs between 2.5 and 220 Rs are investigated. Our simulation results show that, although the two CMEs are separated by 10 h, the second CME is able to overtake the first one and cause compound interactions and an obvious acceleration of the shock. At the L1 point near Earth the two resultant magnetic clouds in our simulation are consistent with the observations by ACE. In this validation study we find that this 3-D MHD model, with the self-consistent source surface as the initial boundary condition and the magnetized plasma blob as the CME model, is able to reproduce and explain some of the general characters of the multiple magnetic clouds observed by satellite.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 8
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    Civilized enclaves of wilderness: substitutes for an alienated urban nature (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-09-20
    Description: The article stresses the inspirational capacity of spontaneous vegetation condensed in spaces defined by human oblivion, such as derelict structures and untamed lots. According to the holstering capacity of the medium, isolated cases (weeds sprouting on crumbling walls), or emulating natural habitats (wasteland flora) developed into a wasteland nature propagating as a consequence of dysfunctional urbanization. Because of increased infrastructure development and urbanization, spaces passable of accommodating such unintended design occurrences recede. Such crude source of inspiration for inoculating nature into architecture and design is to be found within the parameters of enduring, unintended, free form compositions of opportunistic vegetation. The article aims at hosting an alternative to current urban order, in what concerns a contextualized human-nature interaction, launching a thinking scheme for rewinding and sustaining the urge toward soil and nature.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 9
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    Designing switchable near room-temperature multiferroics via the discovery of a novel magnetoelectric coupling (2018)
    Institute of Physics (IOP)
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    Publication Date: 2018-05-10
    Description: Magnetoelectric (ME) coupling is the key ingredient for realizing the cross-control of magnetism and ferroelectricity in multiferroics. However, multiferroics are not only rare, especially at room-temperature, in nature but also the overwhelming majority of known multiferroics do not exhibit highly-desired switching of the direction of magnetization when the polarization is reversed by an electric field. Here, we report group theory analysis and ab initio calculations demonstrating, and revealing the origin of, the existence of a novel form of ME coupling term in a specific class of materials that does allow such switching. This term naturally explains the previously observed electric field control of magnetism in the first known multiferroics, i.e., the Ni– X boracite family. It is also presently used to design a switchable near room-temperature multiferroic (namely, LaSrMnOsO 6 perovskite) having rather large ferroelectric polarization and spontaneous ma...
    Electronic ISSN: 1367-2630
    Topics: Physics
    Published by Institute of Physics (IOP)
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  • 10
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    Thermodynamic analysis and economical evaluation of two 310-80 K pre-cooling stage configurations for helium refrigeration and liquefaction cycle (2017)
    Institute of Physics (IOP)
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    Publication Date: 2017-12-30
    Description: In 310-80 K pre-cooling stage, the temperature of the HP helium stream reduces to about 80 K where nearly 73% of the enthalpy drop from room temperature to 4.5 K occurs. Apart from the most common liquid nitrogen pre-cooling, another 310-80 K pre-cooling configuration with turbine is employed in some helium cryoplants. In this paper, thermodynamic and economical performance of these two kinds of 310-80 K pre-cooling stage configurations has been studied at different operating conditions taking discharge pressure, isentropic efficiency of turbines and liquefaction rate as independent parameters. The exergy efficiency, total UA of heat exchangers and operating cost of two configurations are computed. This work will provide a reference for choosing 310-80 K pre-cooling stage configuration during design.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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