Solar Array Model Corrections from Mars Pathfinder Lander Data
The MESUR solar array power model initially uses assumed values for many input variables.
array tilt azimuth array temperature spectral shif↗
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Results for “SOLAR MODELING”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A Model for Solar Polar Jets
We propose a model for the jetting activity that is commonly observed in the Sun's corona, especially in the open-field regions of polar coronal holes. Magnetic reconnection is the process driving the jets and a relevant magnetic configuration is the well-known null point and fan separatrix topology. The primary challenge in explaining the observations is that reconnection must occur in a short-duration energetic burst rather than quasi-continuously as is implied by the observations of long-lived structures in coronal holes, such as polar plumes, for example. The key idea underlying our model for jets is that reconnection is forbidden for an axisymmetric null-point topology. Consequently, by imposing a twisting motion that maintains the axisymmetry, magnetic stress can be built up to large levels until an ideal instability breaks the symmetry and leads to an explosive release of energy via reconnection. Using 3D MHD simulations we demonstrate that this mechanism does produce jets with high speed and mass, driven by nonlinear Alfven waves. We discuss the implications of our results for observations of the solar corona.
Pariat, E.↗
Interplanetary Radiation and Internal Charging Environment Models for Solar Sails
A Solar Sail Radiation Environment (SSRE) model has been developed for defining charged particle environments over an energy range from 0.01 keV to 1 MeV for hydrogen ions, helium ions, and electrons. The SSRE model provides the free field charged particle environment required for characterizing energy deposition per unit mass, charge deposition, and dose rate dependent conductivity processes required to evaluate radiation dose and internal (bulk) charging processes in the solar sail membrane in interplanetary space. Solar wind and energetic particle measurements from instruments aboard the Ulysses spacecraft in a solar, near-polar orbit provide the particle data over a range of heliospheric latitudes used to derive the environment that can be used for radiation and charging environments for both high inclination 0.5 AU Solar Polar Imager mission and the 1.0 AU L1 solar missions. This paper describes the techniques used to model comprehensive electron, proton, and helium spectra over the range of particle energies of significance to energy and charge deposition in thin (less than 25 micrometers) solar sail materials.
Minow, Joseph I.↗
STEADY-STATE MODEL OF SOLAR WIND ELECTRONS REVISITED
In a recent paper, Kim et al. put forth a steady-state model for the solar wind electrons. The model assumed local equilibrium between the halo electrons, characterized by an intermediate energy range, and the whistler-range fluctuations. The basic wave–particle interaction is assumed to be the cyclotron resonance. Similarly, it was assumed that a dynamical steady state is established between the highly energetic superhalo electrons and high-frequency Langmuir fluctuations. Comparisons with the measured solar wind electron velocity distribution function (VDF) during quiet times were also made, and reasonable agreements were obtained. In such a model, however, only the steady-state solution for the Fokker–Planck type of electron particle kinetic equation was considered. The present paper complements the previous analysis by considering both the steady-state particle and wave kinetic equations. It is shown that the model halo and superhalo electron VDFs, as well as the assumed wave intensity spectra for the whistler and Langmuir fluctuations, approximately satisfy the quasi-linear wave kinetic equations in an approximate sense, thus further validating the local equilibrium model constructed in the paper by Kim et al.
79 ASTRONOMY AND ASTROPHYSICS↗
Deep Learning-enhanced Block-Diagram Modeling of Solar Power Systems
Data-driven models of power system inverter-based resources are desired to run simulations faster than with detailed electromagnetic transient models, to hide proprietary design details, to support control system design applications, and to aggregate the effects of distributed energy resources. This paper applies a customized Hammerstein Wiener framework to train block diagram models from thousands of electromagnetic transient simulations or experimental test records. The block diagram models integrate with larger grid simulations as voltagecontrolled current sources or current-controlled voltage sources for several simulators. Guidelines for block architecture and training are presented. Three-phase balanced, three-phase unbalanced, and single-phase examples all achieve an acceptable root mean square error of no more than 0.05 per-unit.
Mcdermott, Thomas E. [Private consulting company]↗
Foundational Open Source Solar System Modeling Through Improvement and Validation of the System Advisor Model and PVWatts (FY19-FY21 Final Technical Report)
Accelerating intelligent deployment of solar energy technologies demands accurate system modeling every step of the way. From project development to policy research, grid integration studies to development of novel technologies, industry and researchers alike need validated, transparent, easy-to-use, extensible, cutting-edge, and accurate models of both the performance and financing of solar systems. The System Advisor Model (SAM) and PVWatts tools provide a platform to fill that need. The overarching goal of this set of software tools is to enable accurate PV system modeling across the industry, and our usage metrics indicate that we continue to succeed in that endeavor, with a user starting SAM every 2 minutes globally, and over 17 million PVWatts hits per month. This project leveraged DOEs past investment in the SAM and PVWatts platforms to continue to provide valuable and extensible PV, battery, and financial modeling resources to the larger solar community. We pursued multiple avenues in parallel: software maintenance and technical support that are foundational to the continued usability of the SAM and PVWatts platforms; platform and PV model improvements and stakeholder engagement activities that are core to the continued relevance of the platforms; and open source activities to foster the continued creation of a vibrant open-source community around the SAM and PVWatts tools, which opens up exciting new opportunities for industry interaction.
14 SOLAR ENERGY↗
Seismic inversion of the solar entropy: setting a cat among the pigeons
The Sun is the most constrained and well-studied of all stars. As a consequence, the physical ingredients entering solar models are used as a reference to study all other stars observed in the Universe. However, our understanding of the solar structure is still imperfect, as illustrated by the current debate on the heavy element abundances in the Sun. Aims. We wish to provide additional information on the solar structure by carrying out structural inversions of a new physical quantity, a proxy of the entropy of the solar plasma which properties are very sensitive to the temperature gradient below the convective zone. Methods. We use new structural kernels to carry out direct inversions of an entropy proxy of the solar plasma and compare the solar structure to various standard solar models built using various opacity tables and chemical abundances. We also link our results to classical tests commonly found in the literature. Results. Our analysis allows us to probe more efficiently the uncertain regions of the solar models, just below the convective zone, paving the way for new in-depth analyses of the Sun taking into account additional physical uncertainties of solar models beyond the specific question of chemical abundances.
79 ASTRONOMY AND ASTROPHYSICS↗
Impacts of Non-Simultaneous Global Photospheric Magnetic Measurements on Coronal and Solar Wind Modeling
The intensity and arrival time of coronal mass ejections (CMEs) can be significantly influenced by the background solar wind encountered as they propagate outward from the Sun into the interplanetary medium. In addition, solar energetic particles (SEPs) race ahead of CME shock fronts and flare regions along magnetic field lines largely determined by the background solar wind. Predicting the solar wind accurately is therefore critical for improving forecasts of CMEs, SEPs, and high-speed streams. Modeling of the corona and solar wind is challenging in general, as it is highly dependent on global photospheric magnetic field maps, which serve as the boundary conditions to all coronal models that drive solar wind models. Unfortunately, less than half of the Sun’s photospheric magnetic field is reliably measured from any given vantage point and thus it is common for the maps to have highly dated and unreliable measurements in them. While Solar Obiter (SolO) now provides for the first time the opportunity to have simultaneous measurements of nearly the entire surface magnetic field of Sun (e.g., when SolO/PHI measurements are combined with those from SDO/HMI), the required alignment to accomplish this occurs only occasionally. Further, coronal models are extremely sensitive to the strengths of the polar magnetic fields of the Sun, which remain poorly observed. Recently, efforts to mitigate this problem include using flux transport models such as the Air Force Data Assimilative Photospheric Flux Transport (ADAPT) model, which evolves the field forward in time using well known transport processes occurring on the Sun. However, it cannot account for the emergence of new magnetic flux without direct observations. The ESA VIGIL mission will eventually provide continuous observations from the L5, and the proposed SunCHASER mission will likewise do this at the L4 vantage point should it be funded. Ultimately, what is needed is a constellation of spacecraft distributed around the Sun with magnetographs that continuously measure the global surface magnetic field. In this talk, we discuss how the lack of simultaneous global measurements of the photospheric magnetic field adversely impacts the predictive performance of coronal and solar wind models.
C. Nick Arge↗
Fast All-Sky Radiation Model for Solar Applications (FARMS): A Brief Overview of Mechanisms, Performance, and Applications: Preprint
Solar radiation can be computed using radiative transfer models, such as the Rapid Radiation Transfer Model (RRTM) and its general circulation model applications, and used for various energy applications. Due to the complexity of computing radiation fields in aerosol and cloudy atmospheres, simulating solar radiation can be extremely time-consuming, but many approximations--e.g., the two-stream approach and the delta-M truncation scheme--can be utilized. To provide a new fast option for computing solar radiation, we developed the Fast All-sky Radiation Model for Solar applications (FARMS) by parameterizing the simulated diffuse horizontal irradiance and direct normal irradiance for cloudy conditions from the RRTM runs using a 16-stream discrete ordinates radiative transfer method. The solar irradiance at the surface was simulated by combining the cloud irradiance parameterizations with a fast clear-sky model, REST2. To understand the accuracy and efficiency of the newly developed fast model, we analyzed FARMS runs using cloud optical and microphysical properties retrieved using GOES data from 2009-2012. The global horizontal irradiance for cloudy conditions was simulated using FARMS and RRTM for global circulation modeling with a two-stream approximation and compared to measurements taken from the U.S. Department of Energy's Atmospheric Radiation Measurement Climate Research Facility Southern Great Plains site. Our results indicate that the accuracy of FARMS is comparable to or better than the two-stream approach; however, FARMS is approximately 400 times more efficient because it does not explicitly solve the radiative transfer equation for each individual cloud condition. Radiative transfer model runs are computationally expensive, but this model is promising for broad applications in solar resource assessment and forecasting. It is currently being used in the National Solar Radiation Database, which is publicly available from the National Renewable Energy Laboratory at http://nsrdb.nrel.gov.
14 SOLAR ENERGY↗
The formation of a standing shock in a polytropic solar wind model within 1-10 Rs
It is shown how a one-fluid polytropic solar wind model exhibits properties similar to an isothermal wind when localized momentum and/or rapid area divergence produce multiple critical points in the flow. In particular, it is shown that when the sonic transition in the flow occurs closer to the coronal base, multiple steady solutions can exist. These multiple steady solutions consist of a contiuous solution passing through the innermost critical point and other steady solutions involving a steady shock transition. By following the temporal evolution of the solar wind from a steady state with one critical point to a steady state with three critical points, it is shown that a standing shock solution is more likely to develop than a continuous solution when momentum deposition occurs close to the coronal base and the equation of motion admits multiple steady solutions. This result is particularly relevant to the solar wind when momentum deposition occurs as a result of a rapidly diverging coronal hole geometry.
Habbal, S. R.↗
A model of solar energtic particles for use in calculating LET spectra developed from ONR-604 data
A model of Solar Energetic Particles (SEP) has been developed and is applied to solar flares during the 1990/1991 Combined Release and Radiation Effects Satellite (CRRES) mission using data measured by the University of Chicago instrument, ONR-604. The model includes the time-dependent behavior, heavy-ion content, energy spectrum and influence, and can accurately represent the observed SEP events in the energy range between 40 to 500 MeV/nucleon. Results are presented for the March and June, 1991 flare periods.
Chen, J.↗
Assessing the Performance of the Fast All-sky Radiation Model for Solar Applications with Narrowband Irradiances on Tilted Surfaces (FARMS-NIT): Preprint
This study evaluates the performance of a new radiative transfer model, Fast All-sky Radiation Model for Solar Applications with Narrowband Irradiances on Tilted surfaces (FARMS-NIT), that efficiently computes spectral irradiances on inclined photovoltaic panels. FARMS-NIT numerically solves the spatial distribution of solar radiation in 2,002 wavelength bands and thereby accurately provides plane-of-array (POA) irradiances by integrating radiances over inclined surfaces. The FARMS-NIT for clear- and cloudy-sky conditions are used to compute POA irradiances for Typical Meteorological Year 3 sites and compared with the simulation by TMYSPEC. Our results indicate that FARMS-NIT leads to approximately 5% greater spectral irradiances compared to TMYSPEC. The difference in POA irradiance with a latitude tilt angle is slightly larger than global horizontal irradiance.
14 SOLAR ENERGY↗
Sensitivity of solar g-modes to varying G cosmologies
The sensitivity of the solar g-mode oscillation spectrum to variability in the universal gravitational constant G is described. Solar models in varying G cosmologies were constructed by evolving a zero-age main-sequence stellar model to the Sun's current age, while allowing the value of G to change according to the power law G(t) proportional to t(exp -beta), where Beta approximately equals delta G/GH and H is the Hubble constant. All solar models were constrained to the observed luminosity and radius at the current age of the Sun by adjusting the helium abundance and the mixing-length parameter of the models in the usual way for standard stellar models. Low-l g-mode oscillation periods were calculated for each of the models and compared to the claimed observation of the solar g-mode oscillation spectrum by Hill & Gu (1990). If one accepts Hill & Gu's claims, then within the uncertainties of the physics of the solar model calculation, our models rule out all but (delta G/GH) less than approximately 0.05. In other words, we conclude that G could not have varied by more than 2% over the past 4.5 Gyr, the lifetime of the present-day Sun. This result lends independent support to the validity of the standard solar model.
Guenther, D. B.↗
Unifying the Validation of Ambient Solar Wind Models
Progress in space weather research and awareness needs community-wide strategies and procedures to evaluate our modeling assets. Here we present the activities of the Ambient Solar Wind Validation Team embedded in the COSPAR ISWAT initiative. We aim to bridge the gap between model developers and end-users to provide the community with an assessment of the state-of-the-art in solar wind forecasting. To this end, we develop an open online platform for validating solar wind models by comparing their solutions with in situ spacecraft measurements. The online platform will allow the space weather community to test the quality of state-of-the-art solar wind models with unified metrics providing an unbiased assessment of progress over time. In this study, we propose a metadata architecture and recommend community-wide forecasting goals and validation metrics. We conclude with a status update of the online platform and outline future perspectives.
Space weather↗
Adiabatic and nonadiabatic processes in thermal models of solar hard X-ray bursts
The temporal evolution of thermal-bremsstrahlung-emitting material at the top of a solar coronal loop under various processes is examined as a model of solar hard X-ray bursts. The behavior of emission measure and temperature with time is analyzed for the hot plasma confined in a segment at the top of a loop, taking into account the effects or the time variation of the confining toroidal magnetic field, the longitudinal expansion of the source through the motion of a pair of collisionless conduction fronts and unspecified heating or cooling processes. Analytic expressions for the behavior of the toroidal magnetic field and the heating rate necessary to reproduce a given behavior of emission measure and temperature with time are obtained in terms of the initial magnetic field strength and density of the heated region and a characteristic longitudinal expansion time. Results are applied to observations of two impulsive solar hard X-ray bursts, and it is shown that the contribution of heating is negligible after the first few seconds of the events, although significant nonadiabatic heating occurs early in the events.
Emslie, A. G.↗
Investigations of a turbulence-driven solar wind model
This work presents an investigation of the properties of the one-dimensional, two-fluid turbulence-driven solar wind model introduced by Hollweg and Johnson (1988). It is found that the model has serious difficulties in reproducing the observed high-speed wind at 1 AU. In particular, the model proton temperatures are lower than those observed by a factor of 2 or more, and the highest temperature models yield excessive wave intensities at 1 AU. It appears that the problem stems from the specific spatial distribution of heat deposition in the model. Thus this study does not rule out a turbulence-driven fast solar wind, since other forms of the turbulent evolution could probably achieve better results. A three-fluid version of the model is also presented to show that the addition of alpha particles does not significantly reduce the extreme proton temperatures displayed near the sun by the Hollweg and Johnson work. Finally, it is suggested that the additional heating needs to be located well beyond the critical point, implying that the heating mechanism for the fast solar wind is likely not the same as that heating the solar corona.
Isenberg, Philip A.↗
A two-fluid model for solar wind fluid with higher order moments
A spherically symmetric two-fluid model for the solar wind with higher-order moments is presented. In this model, continuity, momentum, temperature and heat flux equations for two components (electrons and protrons) in steady solar wind states are simultaneously solved by using a time-dependent method. This work is used to compare solutions of the steady-state solar wind with and without higher order moments, and to study the effects of thermal conduction. The coupling between electrons and protrons is also given special attention. The numerical solutions of the steady-state solar wind in both subsonic and supersonic regions between the Sun and 1 AU are obtained and graphically illustrated.
Wang, Jingfang↗
Statistical Downscaling of Climate Models for Solar Resource Assessment
This study presents the development of statistical models to efficiently downscale future projections of solar irradiance for solar energy applications. A climate data set simulated from a Regional Climate Model (RCM) obtained from the North American Coordinated Regional Climate Downscaling Experiment (NA-CORDEX) is selected as input to the statistical models to create high-resolution global horizontal irradiance (GHI) over the contiguous United States (CONUS). Our approach builds statistical downscaling models that (1) regrid RCM data (0.22 degree and daily spatiotemporal resolution), (2) correct bias of GHI projections, (3) downscale the future GHI project from daily-scale to hourly-scale, and (4) spatially downscale to generate GHI at 8-km resolution. To calibrate and validate the statistical models, we adapt and use the National Solar Radiation Database (NSRDB). Preliminary results show that the statistical downscaling approach downscales future projections of GHI under two climate scenarios (RCP4.5 and RCP8.5) with a nBIAS of 3%, nMAE of 34% and nRMSE of 46% estimated against NSRDB for the contiguous United State. This presentation will summarize the implemented methodology and validation results as well as future extension of this research.
climate data↗