Evaluation of solar irradiance models for climate studies

NASA Astrophysics Data System (ADS)

Ball, William; Yeo, Kok-Leng; Krivova, Natalie; Solanki, Sami; Unruh, Yvonne; Morrill, Jeff

2015-04-01

Instruments on satellites have been observing both Total Solar Irradiance (TSI) and Spectral Solar Irradiance (SSI), mainly in the ultraviolet (UV), since 1978. Models were developed to reproduce the observed variability and to compute the variability at wavelengths that were not observed or had an uncertainty too high to determine an accurate rotational or solar cycle variability. However, various models and measurements show different solar cycle SSI variability that lead to different modelled responses of ozone and temperature in the stratosphere, mainly due to the different UV variability in each model, and the global energy balance. The NRLSSI and SATIRE-S models are the most comprehensive reconstructions of solar irradiance variability for the period from 1978 to the present day. But while NRLSSI and SATIRE-S show similar solar cycle variability below 250 nm, between 250 and 400 nm SATIRE-S typically displays 50% larger variability, which is however, still significantly less then suggested by recent SORCE data. Due to large uncertainties and inconsistencies in some observational datasets, it is difficult to determine in a simple way which model is likely to be closer to the true solar variability. We review solar irradiance variability measurements and modelling and employ new analysis that sheds light on the causes of the discrepancies between the two models and with the observations.

The new climate data record of total and spectral solar irradiance: Current progress and future steps

NASA Astrophysics Data System (ADS)

Coddington, Odele; Lean, Judith; Rottman, Gary; Pilewskie, Peter; Snow, Martin; Lindholm, Doug

2016-04-01

We present a climate data record of Total Solar Irradiance (TSI) and Solar Spectral Irradiance (SSI), with associated time and wavelength dependent uncertainties, from 1610 to the present. The data record was developed jointly by the Laboratory for Atmospheric and Space Physics (LASP) at the University of Colorado Boulder and the Naval Research Laboratory (NRL) as part of the National Oceanographic and Atmospheric Administration's (NOAA) National Centers for Environmental Information (NCEI) Climate Data Record (CDR) Program, where the data record, source code, and supporting documentation are archived. TSI and SSI are constructed from models that determine the changes from quiet Sun conditions arising from bright faculae and dark sunspots on the solar disk using linear regression of proxies of solar magnetic activity with observations from the SOlar Radiation and Climate Experiment (SORCE) Total Irradiance Monitor (TIM), Spectral Irradiance Monitor (SIM), and SOlar Stellar Irradiance Comparison Experiment (SOLSTICE). We show that TSI can be separately modeled to within TIM's measurement accuracy from solar rotational to solar cycle time scales and we assume that SSI measurements are reliable on solar rotational time scales. We discuss the model formulation, uncertainty estimates, and operational implementation and present comparisons of the modeled TSI and SSI with the measurement record and with other solar irradiance models. We also discuss ongoing work to assess the sensitivity of the modeled irradiances to model assumptions, namely, the scaling of solar variability from rotational-to-cycle time scales and the representation of the sunspot darkening index.

Non-Power Purchase Agreement (PPA) Options for Financing Solar Deployment at Universities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Financing solar using power purchase agreements (PPAs) has facilitated solar deployment of more than 100 megawatts (MW) at universities--as compared to 50 MW facilitated by financing models not using PPAs. This brochure, which overviews existing financing models and funding mechanisms available for solar procurement, focuses on non-PPA financing models. For more information on solar deployment at universities using PPAs, refer to Using Power Purchase Agreements for Solar Deployment at Universities.

Solar Energy Potential in a Changing Climate: Iberia and Azores Assessment Combining Dynamical and Statistical Downscaling Methods

NASA Astrophysics Data System (ADS)

Magarreiro, Clarisse de Lurdes Chapa

The proper characterization of solar radiation resource is essential for the design of any solar energy harnessing systems which aims its optimal performance. To this end, the solar resource is often quantified through solar radiation measurements at meteorological stations. Unfortunately radiation data recorded on the desired location is often inexistent. Furthermore, the actual existing solar radiation databases have also a limited temporal span and, more frequently than desired, missing values and non-uniform formats. Also, such databases consist almost entirely of global solar radiation; variables such as the nature of the solar energy (direct or diffuse) are rarely recorded. Atmospheric models can add value to solar energy applications by enabling solar resource assessments as they easily overcome the limited spatial and temporal coverage of irradiance measuring networks. Furthermore, climate models can be used for any region of the planet to assess the solar resource for not only present climate conditions but also to analyse its long-term past evolution and future tendency. Nowadays such models are a popular approach on the field of solar radiation forecasting but the quality evaluation of the solar radiation representation by such models is first of all a fundamental step to understand its usefulness. Having this in mind, in this thesis, a dynamical downscaling approach is used to evaluate simulated solar radiation at the Earth’s surface which will then enable the characterization of the solar resource. The model output is also combined with a statistical downscaling approach used in its simplest form to minimize the model biases. The work focuses primarily in the Iberian Peninsula as its large climate gradients are representative of diverse meteorological conditions, enabling therefore the adaptation of the presented methods to other regions. Then, following the same methodology, the solar resource of the Azores archipelago is also addressed. The Azores region is often neglected in solar resource assessments and solar resource maps of the Earth’s surface or even of Europe region. These methods are used to characterize the present climate renewable solar resource and analyse the impact of climate change on its projections for the end of the 21st century for both Iberia Peninsula and Azores archipelago. Atmospheric numerical models are however limited in the sense that they only provide global solar radiation, the direct normal radiation and diffuse components are not common outputs to the user. Given this, the separation of global radiation into its diffuse and direct components is analysed in this thesis through models of diffuse solar radiation fraction. One important characteristic of these models is that they are empirically derived from site-specific measurements and a model developed and validated in a very specific climate type region may not hold its suitability to other regions. This thesis focuses on the assessment of such models only for the Azores region which has not been object of this type of analysis before.

Solar Integration Data Sets | Grid Modernization | NREL

Science.gov Websites

modeled solar data to study the operational impacts of solar on the electric power grid. Solar Power Data need to estimate power production from hypothetical solar power plants. Solar Integration National Dataset (SIND) Toolkit The next generation of modeled solar data with higher temporal and spatial

Improved solar models constructed with a formulation of convection for stellar structure and evolution calculations without the mixing-length theory approximations

NASA Technical Reports Server (NTRS)

Lydon, Thomas J.; Fox, Peter A.; Sofia, Sabatino

1993-01-01

We have updated a previous attempt to incorporate within a solar model a treatment of convection based upon numerical simulations of convection rather than mixing-length theory (MLT). We have modified our formulation of convection for a better treatment of the kinetic energy flux. Our solar model has been updated to include a complete range of OPAL opacities, the Debye-Hueckel correction to the equation of state, helium diffusion due to gravitational settling, and atmospheres by Kurucz. We construct a series of models using both MLT and our revised formulation of convection and the compared results to measurements of the solar radius, the solar luminosity, and the depth of the solar convection zone as inferred from helioseismology. We find X(solar) = 0.702 +/- 0.005, Y(solar) = 0.278 +/- 0.005, and Z(solar) = 0.0193 +/- 0.0005.

A numerical model for charge transport and energy conversion of perovskite solar cells.

PubMed

Zhou, Yecheng; Gray-Weale, Angus

2016-02-14

Based on the continuity equations and Poisson's equation, we developed a numerical model for perovskite solar cells. Due to different working mechanisms, the model for perovskite solar cells differs from that of silicon solar cells and Dye Sensitized Solar Cells. The output voltage and current are calculated differently, and in a manner suited in particular to perovskite organohalides. We report a test of our equations against experiment with good agreement. Using this numerical model, it was found that performances of solar cells increase with charge carrier's lifetimes, mobilities and diffusion lengths. The open circuit voltage (Voc) of a solar cell is dependent on light intensities, and charge carrier lifetimes. Diffusion length and light intensity determine the saturated current (Jsc). Additionally, three possible guidelines for the design and fabrication of perovskite solar cells are suggested by our calculations. Lastly, we argue that concentrator perovskite solar cells are promising.

Solar Physics

NASA Technical Reports Server (NTRS)

Wu, S. T.

2000-01-01

The areas of emphasis are: (1) develop theoretical models of the transient release of magnetic energy in the solar atmosphere, e.g., in solar flares, eruptive prominences, coronal mass ejections, etc.; (2) investigate the role of the Sun's magnetic field in the structuring of solar corona by the development of three-dimensional numerical models that describe the field configuration at various heights in the solar atmosphere by extrapolating the field at the photospheric level; (3) develop numerical models to investigate the physical parameters obtained by the ULYSSES mission; (4) develop numerical and theoretical models to investigate solar activity effects on the solar wind characteristics for the establishment of the solar-interplanetary transmission line; and (5) develop new instruments to measure solar magnetic fields and other features in the photosphere, chromosphere transition region and corona. We focused our investigation on the fundamental physical processes in solar atmosphere which directly effect our Planet Earth. The overall goal is to establish the physical process for the Sun-Earth connections.

Development of a Greek solar map based on solar model estimations

NASA Astrophysics Data System (ADS)

Kambezidis, H. D.; Psiloglou, B. E.; Kavadias, K. A.; Paliatsos, A. G.; Bartzokas, A.

2016-05-01

The realization of Renewable Energy Sources (RES) for power generation as the only environmentally friendly solution, moved solar systems to the forefront of the energy market in the last decade. The capacity of the solar power doubles almost every two years in many European countries, including Greece. This rise has brought the need for reliable predictions of meteorological data that can easily be utilized for proper RES-site allocation. The absence of solar measurements has, therefore, raised the demand for deploying a suitable model in order to create a solar map. The generation of a solar map for Greece, could provide solid foundations on the prediction of the energy production of a solar power plant that is installed in the area, by providing an estimation of the solar energy acquired at each longitude and latitude of the map. In the present work, the well-known Meteorological Radiation Model (MRM), a broadband solar radiation model, is engaged. This model utilizes common meteorological data, such as air temperature, relative humidity, barometric pressure and sunshine duration, in order to calculate solar radiation through MRM for areas where such data are not available. Hourly values of the above meteorological parameters are acquired from 39 meteorological stations, evenly dispersed around Greece; hourly values of solar radiation are calculated from MRM. Then, by using an integrated spatial interpolation method, a Greek solar energy map is generated, providing annual solar energy values all over Greece.

The structure of the solar wind in the inner heliosphere

NASA Astrophysics Data System (ADS)

Lee, Christina On-Yee

2010-12-01

This dissertation is devoted to expanding our understanding of the solar wind structure in the inner heliosphere and variations therein with solar activity. Using spacecraft observations and numerical models, the origins of the large-scale structures and long-term trends of the solar wind are explored in order to gain insights on how our Sun determines the space environments of the terrestrial planets. I use long term measurements of the solar wind density, velocity, interplanetary magnetic field, and particles, together with models based on solar magnetic field data, to generate time series of these properties that span one solar rotation (˜27 days). From these time series, I assemble and obtain the synoptic overviews of the solar wind properties. The resulting synoptic overviews show that the solar wind around Mercury, Venus, Earth, and Mars is a complex co-rotating structure with recurring features and occasional transients. During quiet solar conditions, the heliospheric current sheet, which separates the positive interplanetary magnetic field from the negative, usually has a remarkably steady two- or four-sector structure that persists for many solar rotations. Within the sector boundaries are the slow and fast speed solar wind streams that originate from the open coronal magnetic field sources that map to the ecliptic. At the sector boundaries, compressed high-density and the related high-dynamic pressure ridges form where streams from different coronal source regions interact. High fluxes of energetic particles also occur at the boundaries, and are seen most prominently during the quiet solar period. The existence of these recurring features depends on how long-lived are their source regions. In the last decade, 3D numerical solar wind models have become more widely available. They provide important scientific tools for obtaining a more global view of the inner heliosphere and of the relationships between conditions at Mercury, Venus, Earth, and Mars. When I compare the model results with observations for periods outside of solar wind disturbances, I find that the models do a good job of simulating at least the steady, large-scale, ambient solar wind structure. However, it remains a challenge to accurately model the solar wind during active solar conditions. During these times, solar transients such as coronal mass ejections travel through interplanetary space and disturb the ambient solar wind, producing a far less predictable and modelable space environment. However, such conditions may have the greatest impact on the planets - especially on their atmospheres and magnetospheres. I therefore also consider the next steps in modeling, toward including active conditions.

Prediction of energy balance and utilization for solar electric cars

NASA Astrophysics Data System (ADS)

Cheng, K.; Guo, L. M.; Wang, Y. K.; Zafar, M. T.

2017-11-01

Solar irradiation and ambient temperature are characterized by region, season and time-domain, which directly affects the performance of solar energy based car system. In this paper, the model of solar electric cars used was based in Xi’an. Firstly, the meteorological data are modelled to simulate the change of solar irradiation and ambient temperature, and then the temperature change of solar cell is calculated using the thermal equilibrium relation. The above work is based on the driving resistance and solar cell power generation model, which is simulated under the varying radiation conditions in a day. The daily power generation and solar electric car cruise mileage can be predicted by calculating solar cell efficiency and power. The above theoretical approach and research results can be used in the future for solar electric car program design and optimization for the future developments.

Development of Solar Drying Model for Selected Cambodian Fish Species

PubMed Central

Hubackova, Anna; Kucerova, Iva; Chrun, Rithy; Chaloupkova, Petra; Banout, Jan

2014-01-01

A solar drying was investigated as one of perspective techniques for fish processing in Cambodia. The solar drying was compared to conventional drying in electric oven. Five typical Cambodian fish species were selected for this study. Mean solar drying temperature and drying air relative humidity were 55.6°C and 19.9%, respectively. The overall solar dryer efficiency was 12.37%, which is typical for natural convection solar dryers. An average evaporative capacity of solar dryer was 0.049 kg·h−1. Based on coefficient of determination (R 2), chi-square (χ 2) test, and root-mean-square error (RMSE), the most suitable models describing natural convection solar drying kinetics were Logarithmic model, Diffusion approximate model, and Two-term model for climbing perch and Nile tilapia, swamp eel and walking catfish and Channa fish, respectively. In case of electric oven drying, the Modified Page 1 model shows the best results for all investigated fish species except Channa fish where the two-term model is the best one. Sensory evaluation shows that most preferable fish is climbing perch, followed by Nile tilapia and walking catfish. This study brings new knowledge about drying kinetics of fresh water fish species in Cambodia and confirms the solar drying as acceptable technology for fish processing. PMID:25250381

A solar radiation database for Chile.

PubMed

Molina, Alejandra; Falvey, Mark; Rondanelli, Roberto

2017-11-01

Chile hosts some of the sunniest places on earth, which has led to a growing solar energy industry in recent years. However, the lack of high resolution measurements of solar irradiance becomes a critical obstacle for both financing and design of solar installations. Besides the Atacama Desert, Chile displays a large array of "solar climates" due to large latitude and altitude variations, and so provides a useful testbed for the development of solar irradiance maps. Here a new public database for surface solar irradiance over Chile is presented. This database includes hourly irradiance from 2004 to 2016 at 90 m horizontal resolution over continental Chile. Our results are based on global reanalysis data to force a radiative transfer model for clear sky solar irradiance and an empirical model based on geostationary satellite data for cloudy conditions. The results have been validated using 140 surface solar irradiance stations throughout the country. Model mean percentage error in hourly time series of global horizontal irradiance is only 0.73%, considering both clear and cloudy days. The simplicity and accuracy of the model over a wide range of solar conditions provides confidence that the model can be easily generalized to other regions of the world.

Two-parameter model of total solar irradiance variation over the solar cycle

NASA Technical Reports Server (NTRS)

Pap, Judit M.; Willson, Richard C.; Donnelly, Richard F.

1991-01-01

Total solar irradiance measured by the SMM/ACRIM radiometer is modelled from the Photometric Sunspot Index and the Mg II core-to-wing ratio with multiple regression analysis. Considering that the formation of the Mg II line is very similar to that of the Ca II K line, the Mg II core-to-wing ratio, measured by the Nimbus-7 and NOAA9 satellites, is used as a proxy for the bright magnetic elements, including faculae and the magnetic network. It is shown that the relationship between the variations in total solar irradiance and the above solar activity indices depends upon the phase of the solar cycle. Thus, a better fit between total irradiance and its model estimates can be achieved if the irradiance models are calculated for the declining portion and minimum of solar cycle 21, and the rising portion of solar cycle 22, respectively. There is an indication that during the rising portion of solar cycle 22, similar to the maximum time of solar cycle 21, the modelled total irradiance values underestimate the measured values. This suggests that there is an asymmetry in the long-term total irradiance variability.

Standard solar model. II - g-modes

NASA Technical Reports Server (NTRS)

Guenther, D. B.; Demarque, P.; Pinsonneault, M. H.; Kim, Y.-C.

1992-01-01

The paper presents the g-mode oscillation for a set of modern solar models. Each solar model is based on a single modification or improvement to the physics of a reference solar model. Improvements were made to the nuclear reaction rates, the equation of state, the opacities, and the treatment of the atmosphere. The error in the predicted g-mode periods associated with the uncertainties in the model physics is predicted and the specific sensitivities of the g-mode periods and their period spacings to the different model structures are described. In addition, these models are compared to a sample of published observations. A remarkably good agreement is found between the 'best' solar model and the observations of Hill and Gu (1990).

Standard solar model

NASA Technical Reports Server (NTRS)

Guenther, D. B.; Demarque, P.; Kim, Y.-C.; Pinsonneault, M. H.

1992-01-01

A set of solar models have been constructed, each based on a single modification to the physics of a reference solar model. In addition, a model combining several of the improvements has been calculated to provide a best solar model. Improvements were made to the nuclear reaction rates, the equation of state, the opacities, and the treatment of the atmosphere. The impact on both the structure and the frequencies of the low-l p-modes of the model to these improvements are discussed. It is found that the combined solar model, which is based on the best physics available (and does not contain any ad hoc assumptions), reproduces the observed oscillation spectrum (for low-l) within the errors associated with the uncertainties in the model physics (primarily opacities).

Can binary stars test solar models?

NASA Technical Reports Server (NTRS)

Popper, D. M.; Ulrich, R. K.

1986-01-01

The position in the H-R diagram of the approximately solar-mass component of the Hyades eclipsing binary, HD 27130, is compared with the predictions of stellar structure theory. The stellar models are calibrated by matching a model with the solar heavy element composition and age to the solar radius and luminosity. The comparison to the Hyades binary then is a test of the prediction that the initial solar luminosity was only about 0.7 times the present solar luminosity. The agreement is satisfactory, lending a measure of confidence to the solar model employed, provided that the initial helium abundance of the Hyades stars is not greater than that of the sun and is not less by more than about 0.03 in Y. Unless the model is grossly incorrect, the inference of Stromgren, Olsen, and Gustafsson (1982) from the 'Hyades anomaly' in intermediate-band photometry that Y(Hyades) is less than Y(solar) by 0.1 or 0.15 is rejected by the observed properties of HD 27130.

The National Solar Radiation Database (NSRDB): A Brief Overview

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habte, Aron M; Sengupta, Manajit; Lopez, Anthony

This poster presents a high-level overview of the National Solar Radiation Database (NSRDB). The NSRDB uses the physics-based model (PSM), which was developed using: adapted PATMOS-X model for cloud identification and properties, REST-2 model for clear-sky conditions, and NREL's Fast All-sky Radiation Model for Solar Applications (FARMS) for cloudy-sky Global Horizontal Irradiance (GHI) solar irradiance calculations.

Ensemble Solar Forecasting Statistical Quantification and Sensitivity Analysis: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheung, WanYin; Zhang, Jie; Florita, Anthony

2015-12-08

Uncertainties associated with solar forecasts present challenges to maintain grid reliability, especially at high solar penetrations. This study aims to quantify the errors associated with the day-ahead solar forecast parameters and the theoretical solar power output for a 51-kW solar power plant in a utility area in the state of Vermont, U.S. Forecasts were generated by three numerical weather prediction (NWP) models, including the Rapid Refresh, the High Resolution Rapid Refresh, and the North American Model, and a machine-learning ensemble model. A photovoltaic (PV) performance model was adopted to calculate theoretical solar power generation using the forecast parameters (e.g., irradiance,more » cell temperature, and wind speed). Errors of the power outputs were quantified using statistical moments and a suite of metrics, such as the normalized root mean squared error (NRMSE). In addition, the PV model's sensitivity to different forecast parameters was quantified and analyzed. Results showed that the ensemble model yielded forecasts in all parameters with the smallest NRMSE. The NRMSE of solar irradiance forecasts of the ensemble NWP model was reduced by 28.10% compared to the best of the three NWP models. Further, the sensitivity analysis indicated that the errors of the forecasted cell temperature attributed only approximately 0.12% to the NRMSE of the power output as opposed to 7.44% from the forecasted solar irradiance.« less

Seven-panel solar wing deployment and on-orbit maneuvering analyses

NASA Astrophysics Data System (ADS)

Hwang, Earl

2005-05-01

BSS developed a new generation high power (~20kW) solar array to meet the customer demands. The high power solar array had the north and south solar wings of which designs were identical. Each side of the solar wing consists of three main conventional solar panels and the four-side panel swing-out new design. The fully deployed solar array surface area is 966 ft2. It was a quite challenging task to define the solar array's optimum design parameters and deployment scheme for such a huge solar array's successful deployment and on-orbit maneuvering. Hence, a deployable seven-flex-panel solar wing nonlinear math model and a fully deployed solar array/bus-payload math model were developed with the Dynamic Analysis and Design System (DADS) program codes utilizing the inherited and empirical data. Performing extensive parametric analyses with the math model, the optimum design parameters and the orbit maneuvering /deployment schemes were determined to meet all the design requirements, and for the successful solar wing deployment on-orbit.

Subgrid Scale Modeling in Solar Convection Simulations using the ASH Code

NASA Technical Reports Server (NTRS)

Young, Y.-N.; Miesch, M.; Mansour, N. N.

2003-01-01

The turbulent solar convection zone has remained one of the most challenging and important subjects in physics. Understanding the complex dynamics in the solar con- vection zone is crucial for gaining insight into the solar dynamo problem. Many solar observatories have generated revealing data with great details of large scale motions in the solar convection zone. For example, a strong di erential rotation is observed: the angular rotation is observed to be faster at the equator than near the poles not only near the solar surface, but also deep in the convection zone. On the other hand, due to the wide range of dynamical scales of turbulence in the solar convection zone, both theory and simulation have limited success. Thus, cutting edge solar models and numerical simulations of the solar convection zone have focused more narrowly on a few key features of the solar convection zone, such as the time-averaged di erential rotation. For example, Brun & Toomre (2002) report computational finding of differential rotation in an anelastic model for solar convection. A critical shortcoming in this model is that the viscous dissipation is based on application of mixing length theory to stellar dynamics with some ad hoc parameter tuning. The goal of our work is to implement the subgrid scale model developed at CTR into the solar simulation code and examine how the differential rotation will be a affected as a result. Specifically, we implement a Smagorinsky-Lilly subgrid scale model into the ASH (anelastic spherical harmonic) code developed over the years by various authors. This paper is organized as follows. In x2 we briefly formulate the anelastic system that describes the solar convection. In x3 we formulate the Smagorinsky-Lilly subgrid scale model for unstably stratifed convection. We then present some preliminary results in x4, where we also provide some conclusions and future directions.

Solar-terrestrial models and application software

NASA Technical Reports Server (NTRS)

Bilitza, Dieter

1990-01-01

The empirical models related to solar-terrestrial sciences are listed and described which are available in the form of computer programs. Also included are programs that use one or more of these models for application specific purposes. The entries are grouped according to the region of the solar-terrestrial environment to which they belong and according to the parameter which they describe. Regions considered include the ionosphere, atmosphere, magnetosphere, planets, interplanetary space, and heliosphere. Also provided is the information on the accessibility for solar-terrestrial models to specify the magnetic and solar activity conditions.

Modeling and simulation of the solar concentrator in photovoltaic systems through the application of a new BRDF function model

NASA Astrophysics Data System (ADS)

Plachta, Kamil

2016-04-01

The paper presents a new algorithm that uses a combination of two models of BRDF functions: Torrance-Sparrow model and HTSG model. The knowledge of technical parameters of a surface is especially useful in the construction of the solar concentrator. The concentrator directs the reflected solar radiation on the surface of photovoltaic panels, increasing the amount of incident radiance. The software applying algorithm allows to calculate surface parameters of the solar concentrator. Performed simulation showing the share of diffuse component and directional component in reflected stream for surfaces made from particular materials. The impact of share of each component in reflected stream on the efficiency of the solar concentrator and photovoltaic surface has also been described. Subsequently, simulation change the value of voltage, current and power output of monocrystalline photovoltaic panels installed in a solar concentrator system has been made for selected surface of materials solar concentrator.

Modeling Climate Responses to Spectral Solar Forcing on Centennial and Decadal Time Scales

NASA Technical Reports Server (NTRS)

Wen, G.; Cahalan, R.; Rind, D.; Jonas, J.; Pilewskie, P.; Harder, J.

2012-01-01

We report a series of experiments to explore clima responses to two types of solar spectral forcing on decadal and centennial time scales - one based on prior reconstructions, and another implied by recent observations from the SORCE (Solar Radiation and Climate Experiment) SIM (Spectral 1rradiance Monitor). We apply these forcings to the Goddard Institute for Space Studies (GISS) Global/Middle Atmosphere Model (GCMAM). that couples atmosphere with ocean, and has a model top near the mesopause, allowing us to examine the full response to the two solar forcing scenarios. We show different climate responses to the two solar forCing scenarios on decadal time scales and also trends on centennial time scales. Differences between solar maximum and solar minimum conditions are highlighted, including impacts of the time lagged reSponse of the lower atmosphere and ocean. This contrasts with studies that assume separate equilibrium conditions at solar maximum and minimum. We discuss model feedback mechanisms involved in the solar forced climate variations.

Analytical determination of critical crack size in solar cells

NASA Technical Reports Server (NTRS)

Chen, C. P.

1988-01-01

Although solar cells usually have chips and cracks, no material specifications concerning the allowable crack size on solar cells are available for quality assurance and engineering design usage. Any material specifications that the cell manufacturers use were developed for cosmetic reasons that have no technical basis. Therefore, the Applied Solar Energy Corporation (ASEC) has sponsored a continuing program for the fracture mechanics evaluation of GaAs. Fracture mechanics concepts were utilized to develop an analytical model that can predict the critical crack size of solar cells. This model indicates that the edge cracks of a solar cell are more critical than its surface cracks. In addition, the model suggests that the material specifications on the allowable crack size used for Si solar cells should not be applied to GaAs solar cells. The analytical model was applied to Si and GaAs solar cells, but it would also be applicable to the semiconductor wafers of other materials, such as a GaAs thin film on a Ge substrate, using appropriate input data.

Circuit transients due to negative bias arcs-II. [on solar cell power systems in low earth orbit

NASA Technical Reports Server (NTRS)

Metz, R. N.

1986-01-01

Two new models of negative-bias arcing on a solar cell power system in Low Earth Orbit are presented. One is an extended, analytical model and the other is a non-linear, numerical model. The models are based on an earlier analytical model in which the interactions between solar cell interconnects and the space plasma as well as the parameters of the power circuit are approximated linearly. Transient voltages due to arcs struck at the negative thermal of the solar panel are calculated in the time domain. The new models treat, respectively, further linear effects within the solar panel load circuit and non-linear effects associated with the plasma interactions. Results of computer calculations with the models show common-mode voltage transients of the electrically floating solar panel struck by an arc comparable to the early model but load transients that differ substantially from the early model. In particular, load transients of the non-linear model can be more than twice as great as those of the early model and more than twenty times as great as the extended, linear model.

Turbulent Transport in a Three-dimensional Solar Wind

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shiota, D.; Zank, G. P.; Adhikari, L.

2017-03-01

Turbulence in the solar wind can play essential roles in the heating of coronal and solar wind plasma and the acceleration of the solar wind and energetic particles. Turbulence sources are not well understood and thought to be partly enhanced by interaction with the large-scale inhomogeneity of the solar wind and the interplanetary magnetic field and/or transported from the solar corona. To investigate the interaction with background inhomogeneity and the turbulence sources, we have developed a new 3D MHD model that includes the transport and dissipation of turbulence using the theoretical model of Zank et al. We solve for themore » temporal and spatial evolution of three moments or variables, the energy in the forward and backward fluctuating modes and the residual energy and their three corresponding correlation lengths. The transport model is coupled to our 3D model of the inhomogeneous solar wind. We present results of the coupled solar wind-turbulence model assuming a simple tilted dipole magnetic configuration that mimics solar minimum conditions, together with several comparative intermediate cases. By considering eight possible solar wind and turbulence source configurations, we show that the large-scale solar wind and IMF inhomogeneity and the strength of the turbulence sources significantly affect the distribution of turbulence in the heliosphere within 6 au. We compare the predicted turbulence distribution results from a complete solar minimum model with in situ measurements made by the Helios and Ulysses spacecraft, finding that the synthetic profiles of the turbulence intensities show reasonable agreement with observations.« less

Toward a descriptive model of solar particles in the heliosphere

NASA Technical Reports Server (NTRS)

Shea, M. A.; Smart, D. F.; Adams, James H., Jr.; Chenette, D.; Feynman, Joan; Hamilton, Douglas C.; Heckman, G. R.; Konradi, A.; Lee, Martin A.; Nachtwey, D. S.

1988-01-01

During a workshop on the interplanetary charged particle environment held in 1987, a descriptive model of solar particles in the heliosphere was assembled. This model includes the fluence, composition, energy spectra, and spatial and temporal variations of solar particles both within and beyong 1 AU. The ability to predict solar particle fluences was also discussed. Suggestions for specific studies designed to improve the basic model were also made.

Astroparticle physics with solar neutrinos

PubMed Central

NAKAHATA, Masayuki

2011-01-01

Solar neutrino experiments observed fluxes smaller than the expectations from the standard solar model. This discrepancy is known as the “solar neutrino problem”. Flux measurements by Super-Kamiokande and SNO have demonstrated that the solar neutrino problem is due to neutrino oscillations. Combining the results of all solar neutrino experiments, parameters for solar neutrino oscillations are obtained. Correcting for the effect of neutrino oscillations, the observed neutrino fluxes are consistent with the prediction from the standard solar model. In this article, results of solar neutrino experiments are reviewed with detailed descriptions of what Kamiokande and Super-Kamiokande have contributed to the history of astroparticle physics with solar neutrino measurements. PMID:21558758

A Didactic Experiment and Model of a Flat-Plate Solar Collector

ERIC Educational Resources Information Center

Gallitto, Aurelio Agliolo; Fiordilino, Emilio

2011-01-01

We report on an experiment performed with a home-made flat-plate solar collector, carried out together with high-school students. To explain the experimental results, we propose a model that describes the heating process of the solar collector. The model accounts quantitatively for the experimental data. We suggest that solar-energy topics should…

Solar radiation - to - power generation models for one-axis tracking PV system with on-site measurements from Eskisehir, Turkey

NASA Astrophysics Data System (ADS)

Filik, Tansu; Başaran Filik, Ümmühan; Nezih Gerek, Ömer

2017-11-01

In this study, new analytic models are proposed for mapping on-site global solar radiation values to electrical power output values in solar photovoltaic (PV) panels. The model extraction is achieved by simultaneously recording solar radiation and generated power from fixed and tracking panels, each with capacity of 3 kW, in Eskisehir (Turkey) region. It is shown that the relation between the solar radiation and the corresponding electric power is not only nonlinear, but it also exhibits an interesting time-varying characteristic in the form of a hysteresis function. This observed radiation-to-power relation is, then, analytically modelled with three piece-wise function parts (corresponding to morning, noon and evening times), which is another novel contribution of this work. The model is determined for both fixed panels and panels with a tracking system. Especially the panel system with a dynamic tracker produces a harmonically richer (with higher values in general) characteristic, so higher order polynomial models are necessary for the construction of analytical solar radiation models. The presented models, characteristics of the hysteresis functions, and differences in the fixed versus solar-tracking panels are expected to provide valuable insight for further model based researches.

Wave Modeling of the Solar Wind.

PubMed

Ofman, Leon

The acceleration and heating of the solar wind have been studied for decades using satellite observations and models. However, the exact mechanism that leads to solar wind heating and acceleration is poorly understood. In order to improve the understanding of the physical mechanisms that are involved in these processes a combination of modeling and observational analysis is required. Recent models constrained by satellite observations show that wave heating in the low-frequency (MHD), and high-frequency (ion-cyclotron) range may provide the necessary momentum and heat input to coronal plasma and produce the solar wind. This review is focused on the results of several recent solar modeling studies that include waves explicitly in the MHD and the kinetic regime. The current status of the understanding of the solar wind acceleration and heating by waves is reviewed.

Effect of Grain Boundaries on the Performance of Thin-Film-Based Polycrystalline Silicon Solar Cells: A Numerical Modeling

NASA Astrophysics Data System (ADS)

Chhetri, Nikita; Chatterjee, Somenath

2018-01-01

Solar cells/photovoltaic, a renewable energy source, is appraised to be the most effective alternative to the conventional electrical energy generator. A cost-effective alternative of crystalline wafer-based solar cell is thin-film polycrystalline-based solar cell. This paper reports the numerical analysis of dependency of the solar cell parameters (i.e., efficiency, fill factor, open-circuit voltage and short-circuit current density) on grain size for thin-film-based polycrystalline silicon (Si) solar cells. A minority carrier lifetime model is proposed to do a correlation between the grains, grain boundaries and lifetime for thin-film-based polycrystalline Si solar cells in MATLAB environment. As observed, the increment in the grain size diameter results in increase in minority carrier lifetime in polycrystalline Si thin film. A non-equivalent series resistance double-diode model is used to find the dark as well as light (AM1.5) current-voltage (I-V) characteristics for thin-film-based polycrystalline Si solar cells. To optimize the effectiveness of the proposed model, a successive approximation method is used and the corresponding fitting parameters are obtained. The model is validated with the experimentally obtained results reported elsewhere. The experimentally reported solar cell parameters can be found using the proposed model described here.

Stochastic Short-term High-resolution Prediction of Solar Irradiance and Photovoltaic Power Output

DOE Office of Scientific and Technical Information (OSTI.GOV)

Melin, Alexander M.; Olama, Mohammed M.; Dong, Jin

The increased penetration of solar photovoltaic (PV) energy sources into electric grids has increased the need for accurate modeling and prediction of solar irradiance and power production. Existing modeling and prediction techniques focus on long-term low-resolution prediction over minutes to years. This paper examines the stochastic modeling and short-term high-resolution prediction of solar irradiance and PV power output. We propose a stochastic state-space model to characterize the behaviors of solar irradiance and PV power output. This prediction model is suitable for the development of optimal power controllers for PV sources. A filter-based expectation-maximization and Kalman filtering mechanism is employed tomore » estimate the parameters and states in the state-space model. The mechanism results in a finite dimensional filter which only uses the first and second order statistics. The structure of the scheme contributes to a direct prediction of the solar irradiance and PV power output without any linearization process or simplifying assumptions of the signal’s model. This enables the system to accurately predict small as well as large fluctuations of the solar signals. The mechanism is recursive allowing the solar irradiance and PV power to be predicted online from measurements. The mechanism is tested using solar irradiance and PV power measurement data collected locally in our lab.« less

Probability Density Functions of the Solar Wind Driver of the Magnetopshere-Ionosphere System

NASA Astrophysics Data System (ADS)

Horton, W.; Mays, M. L.

2007-12-01

The solar-wind driven magnetosphere-ionosphere system is a complex dynamical system in that it exhibits (1) sensitivity to initial conditions; (2) multiple space-time scales; (3) bifurcation sequences with hysteresis in transitions between attractors; and (4) noncompositionality. This system is modeled by WINDMI--a network of eight coupled ordinary differential equations which describe the transfer of power from the solar wind through the geomagnetic tail, the ionosphere, and ring current in the system. The model captures both storm activity from the plasma ring current energy, which yields a model Dst index result, and substorm activity from the region 1 field aligned current, yielding model AL and AU results. The input to the model is the solar wind driving voltage calculated from ACE solar wind parameter data, which has a regular coherent component and broad-band turbulent component. Cross correlation functions of the input-output data time series are computed and the conditional probability density function for the occurrence of substorms given earlier IMF conditions are derived. The model shows a high probability of substorms for solar activity that contains a coherent, rotating IMF with magnetic cloud features. For a theoretical model of the imprint of solar convection on the solar wind we have used the Lorenz attractor (Horton et al., PoP, 1999, doi:10.10631.873683) as a solar wind driver. The work is supported by NSF grant ATM-0638480.

Bridging the Radiative Transfer Models for Meteorology and Solar Energy Applications

NASA Astrophysics Data System (ADS)

Xie, Y.; Sengupta, M.

2017-12-01

Radiative transfer models are used to compute solar radiation reaching the earth surface and play an important role in both meteorology and solar energy studies. Therefore, they are designed to meet the needs of specialized applications. For instance, radiative transfer models for meteorology seek to provide more accurate cloudy-sky radiation compared to models used in solar energy that are geared towards accuracy in clear-sky conditions associated with the maximum solar resource. However, models for solar energy applications are often computationally faster, as the complex solution of the radiative transfer equation is parameterized by atmospheric properties that can be acquired from surface- or satellite-based observations. This study introduces the National Renewable Energy Laboratory's (NREL's) recent efforts to combine the advantages of radiative transfer models designed for meteorology and solar energy applictions. A fast all-sky radiation model, FARMS-NIT, was developed to efficiently compute narrowband all-sky irradiances over inclined photovoltaic (PV) panels. This new model utilizes the optical preperties from a solar energy model, SMARTS, to computes surface radiation by considering all possible paths of photon transmission and the relevent scattering and absorption attenuation. For cloudy-sky conditions, cloud bidirectional transmittance functions (BTDFs) are provided by a precomputed lookup table (LUT) by LibRadtran. Our initial results indicate that FARMS-NIT has an accuracy that is similar to LibRadtran, a highly accurate multi-stream model, but is significantly more efficient. The development and validation of this model will be presented.

Mass-loading of the solar wind at 67P/Churyumov-Gerasimenko. Observations and modelling

NASA Astrophysics Data System (ADS)

Behar, E.; Lindkvist, J.; Nilsson, H.; Holmström, M.; Stenberg-Wieser, G.; Ramstad, R.; Götz, C.

2016-11-01

Context. The first long-term in-situ observation of the plasma environment in the vicinity of a comet, as provided by the European Rosetta spacecraft. Aims: Here we offer characterisation of the solar wind flow near 67P/Churyumov-Gerasimenko (67P) and its long term evolution during low nucleus activity. We also aim to quantify and interpret the deflection and deceleration of the flow expected from ionization of neutral cometary particles within the undisturbed solar wind. Methods: We have analysed in situ ion and magnetic field data and combined this with hybrid modeling of the interaction between the solar wind and the comet atmosphere. Results: The solar wind deflection is increasing with decreasing heliocentric distances, and exhibits very little deceleration. This is seen both in observations and in modeled solar wind protons. According to our model, energy and momentum are transferred from the solar wind to the coma in a single region, centered on the nucleus, with a size in the order of 1000 km. This interaction affects, over larger scales, the downstream modeled solar wind flow. The energy gained by the cometary ions is a small fraction of the energy available in the solar wind. Conclusions: The deflection of the solar wind is the strongest and clearest signature of the mass-loading for a small, low-activity comet, whereas there is little deceleration of the solar wind.

Torsional Buckling Tests of a Simulated Solar Array

NASA Technical Reports Server (NTRS)

Thornton, E. A.

1996-01-01

Spacecraft solar arrays are typically large structures supported by long, thin deployable booms. As such, they may be particularly susceptible to abnormal structural behavior induced by mechanical and thermal loading. One example is the Hubble Space Telescope solar arrays which consist of two split tubes fit one inside the other called BiSTEMs. The original solar arrays on the Hubble Space Telescope were found to be severely twisted following deployment and later telemetry data showed the arrays were vibrating during daylight to night and night to daylight transition. The solar array twist however can force the BiSTEM booms to change in cross-section and cause tile solar arrays to react unpredictably to future loading. The solar arrays were redesigned to correct for tile vibration, however, upon redeployment they again twisted. To assess the influence of boom cross-sectional configuration, experiments were conducted on two types of booms, (1)booms with closed cross-sections, and (2) booms with open cross-sections. Both models were subjected to compressive loading and imposed tip deflections. An existing analytical model by Chung and Thornton was used to define the individual load ranges for each model solar array configuration. The load range for the model solar array using closed cross-section booms was 0-120 Newtons and 0-160 Newtons for the model solar array using open cross-section booms. The results indicate the model solar array with closed cross-section booms buckled only in flexure. However, the results of the experiment with open cross-section booms indicate the model solar array buckled only in torsion and with imposed tip deflections the cross section can degrade by rotation of the inner relative to the outer STEM. For tile Hubble Space Telescope solar arrays the results of these experiments indicate the twisting resulted from the initial mechanical loading of the open cross-section booms.

An empirical model to forecast solar wind velocity through statistical modeling

NASA Astrophysics Data System (ADS)

Gao, Y.; Ridley, A. J.

2013-12-01

The accurate prediction of the solar wind velocity has been a major challenge in the space weather community. Previous studies proposed many empirical and semi-empirical models to forecast the solar wind velocity based on either the historical observations, e.g. the persistence model, or the instantaneous observations of the sun, e.g. the Wang-Sheeley-Arge model. In this study, we use the one-minute WIND data from January 1995 to August 2012 to investigate and compare the performances of 4 models often used in literature, here referred to as the null model, the persistence model, the one-solar-rotation-ago model, and the Wang-Sheeley-Arge model. It is found that, measured by root mean square error, the persistence model gives the most accurate predictions within two days. Beyond two days, the Wang-Sheeley-Arge model serves as the best model, though it only slightly outperforms the null model and the one-solar-rotation-ago model. Finally, we apply the least-square regression to linearly combine the null model, the persistence model, and the one-solar-rotation-ago model to propose a 'general persistence model'. By comparing its performance against the 4 aforementioned models, it is found that the accuracy of the general persistence model outperforms the other 4 models within five days. Due to its great simplicity and superb performance, we believe that the general persistence model can serve as a benchmark in the forecast of solar wind velocity and has the potential to be modified to arrive at better models.

Measurements and Modeling of Radiation Exposure Due to Solar Particle Events

NASA Astrophysics Data System (ADS)

Beck, P.; Conrad Wp6-Sgb Team

Dose assessment procedures of cosmic radiation to aircraft crew are introduced in most of the European countries according the corresponding European directive and national regulations 96 29 Euratom However the radiation exposure due to solar particle events is still a matter of scientific research Several in-flight measurements were performed during solar storm conditions First models to estimate the exposure due to solar particle events were discussed previously Recently EURADOS European Radiation Dosimetry Group http www eurados org started to coordinate research activities in model improvements for dose assessment of solar particle events The coordinated research is a work package of the European research project CONRAD Coordinated Network for Radiation Dosimetry on complex mixed radiation fields at workplaces Major aim of sub group B of that work package is the validation of models for dose assessment of solar particle events using data from neutron ground level monitors in-flight measurement results obtained during a solar particle event and proton satellite data The paper describes the current status of obtainable solar storm measurements and gives an overview of the existing models for dose assessment of solar particle events in flight altitudes

Interdigitated Back-Surface-Contact Solar Cell Modeling Using Silvaco Atlas

DTIC Science & Technology

2015-06-01

11 2. Solar Spectrum ...................................................................................13 3. PV Cell Efficiency...Figure 10. Spectrum of solar radiance, from [12]. 14 3. PV Cell Efficiency There are many factors that affect the efficiency of a solar cell. Metal...BACK-SURFACE-CONTACT SOLAR CELL MODELING USING SILVACO ATLAS by Shawn E. Green June 2015 Thesis Advisor: Sherif Michael Second Reader

Forecast Method of Solar Irradiance with Just-In-Time Modeling

NASA Astrophysics Data System (ADS)

Suzuki, Takanobu; Goto, Yusuke; Terazono, Takahiro; Wakao, Shinji; Oozeki, Takashi

PV power output mainly depends on the solar irradiance which is affected by various meteorological factors. So, it is required to predict solar irradiance in the future for the efficient operation of PV systems. In this paper, we develop a novel approach for solar irradiance forecast, in which we introduce to combine the black-box model (JIT Modeling) with the physical model (GPV data). We investigate the predictive accuracy of solar irradiance over wide controlled-area of each electric power company by utilizing the measured data on the 44 observation points throughout Japan offered by JMA and the 64 points around Kanto by NEDO. Finally, we propose the application forecast method of solar irradiance to the point which is difficulty in compiling the database. And we consider the influence of different GPV default time on solar irradiance prediction.

A multi-node model for transient heat transfer analysis of stratospheric airships

NASA Astrophysics Data System (ADS)

Alam, Mohammad Irfan; Pant, Rajkumar S.

2017-06-01

This paper describes a seven-node thermal model for transient heat transfer analysis of a solar powered stratospheric airship in floating condition. The solar array is modeled as a three node system, viz., outer layer, solar cell and substrate. The envelope is also modeled in three nodes, and the contained gas is considered as the seventh node. The heat transfer equations involving radiative, infra-red and conductive heat are solved simultaneously using a fourth order Runge-Kutta Method. The model can be used to study the effect of solar radiation, ambient wind, altitude and location of deployment of the airship on the temperature of the solar array. The model has been validated against some experimental data and numerical results quoted in literature. The effect of change in the value of some operational parameters on temperature of the solar array, and hence on its power output is also discussed.

Calculated values of atomic oxygen fluences and solar exposure on selected surfaces of LDEF

NASA Technical Reports Server (NTRS)

Gillis, J. R.; Pippin, H. G.; Bourassa, R. J.; Gruenbaum, P. E.

1995-01-01

Atomic oxygen (AO) fluences and solar exposure have been modeled for selected hardware from the Long Duration Exposure Facility (LDEF). The atomic oxygen exposure was modeled using the microenvironment modeling code SHADOWV2. The solar exposure was modeled using the microenvironment modeling code SOLSHAD version 1.0.

Self consistent MHD modeling of the solar wind from coronal holes with distinct geometries

NASA Technical Reports Server (NTRS)

Stewart, G. A.; Bravo, S.

1995-01-01

Utilizing an iterative scheme, a self-consistent axisymmetric MHD model for the solar wind has been developed. We use this model to evaluate the properties of the solar wind issuing from the open polar coronal hole regions of the Sun, during solar minimum. We explore the variation of solar wind parameters across the extent of the hole and we investigate how these variations are affected by the geometry of the hole and the strength of the field at the coronal base.

A Solar-luminosity Model and Climate

NASA Technical Reports Server (NTRS)

Perry, Charles A.

1990-01-01

Although the mechanisms of climatic change are not completely understood, the potential causes include changes in the Sun's luminosity. Solar activity in the form of sunspots, flares, proton events, and radiation fluctuations has displayed periodic tendencies. Two types of proxy climatic data that can be related to periodic solar activity are varved geologic formations and freshwater diatom deposits. A model for solar luminosity was developed by using the geometric progression of harmonic cycles that is evident in solar and geophysical data. The model assumes that variation in global energy input is a result of many periods of individual solar-luminosity variations. The 0.1-percent variation of the solar constant measured during the last sunspot cycle provided the basis for determining the amplitude of each luminosity cycle. Model output is a summation of the amplitudes of each cycle of a geometric progression of harmonic sine waves that are referenced to the 11-year average solar cycle. When the last eight cycles in Emiliani's oxygen-18 variations from deep-sea cores were standardized to the average length of glaciations during the Pleistocene (88,000 years), correlation coefficients with the model output ranged from 0.48 to 0.76. In order to calibrate the model to real time, model output was graphically compared to indirect records of glacial advances and retreats during the last 24,000 years and with sea-level rises during the Holocene. Carbon-14 production during the last millenium and elevations of the Great Salt Lake for the last 140 years demonstrate significant correlations with modeled luminosity. Major solar flares during the last 90 years match well with the time-calibrated model.

Future missions studies: Combining Schatten's solar activity prediction model with a chaotic prediction model

NASA Technical Reports Server (NTRS)

Ashrafi, S.

1991-01-01

K. Schatten (1991) recently developed a method for combining his prediction model with our chaotic model. The philosophy behind this combined model and his method of combination is explained. Because the Schatten solar prediction model (KS) uses a dynamo to mimic solar dynamics, accurate prediction is limited to long-term solar behavior (10 to 20 years). The Chaotic prediction model (SA) uses the recently developed techniques of nonlinear dynamics to predict solar activity. It can be used to predict activity only up to the horizon. In theory, the chaotic prediction should be several orders of magnitude better than statistical predictions up to that horizon; beyond the horizon, chaotic predictions would theoretically be just as good as statistical predictions. Therefore, chaos theory puts a fundamental limit on predictability.

Astroparticle physics with solar neutrinos.

PubMed

Nakahata, Masayuki

2011-01-01

Solar neutrino experiments observed fluxes smaller than the expectations from the standard solar model. This discrepancy is known as the "solar neutrino problem". Flux measurements by Super-Kamiokande and SNO have demonstrated that the solar neutrino problem is due to neutrino oscillations. Combining the results of all solar neutrino experiments, parameters for solar neutrino oscillations are obtained. Correcting for the effect of neutrino oscillations, the observed neutrino fluxes are consistent with the prediction from the standard solar model. In this article, results of solar neutrino experiments are reviewed with detailed descriptions of what Kamiokande and Super-Kamiokande have contributed to the history of astroparticle physics with solar neutrino measurements. (Communicated by Toshimitsu Yamazaki, M.J.A.).

Solar-wind predictions for the Parker Solar Probe orbit. Near-Sun extrapolations derived from an empirical solar-wind model based on Helios and OMNI observations

NASA Astrophysics Data System (ADS)

Venzmer, M. S.; Bothmer, V.

2018-03-01

Context. The Parker Solar Probe (PSP; formerly Solar Probe Plus) mission will be humanitys first in situ exploration of the solar corona with closest perihelia at 9.86 solar radii (R⊙) distance to the Sun. It will help answer hitherto unresolved questions on the heating of the solar corona and the source and acceleration of the solar wind and solar energetic particles. The scope of this study is to model the solar-wind environment for PSPs unprecedented distances in its prime mission phase during the years 2018 to 2025. The study is performed within the Coronagraphic German And US SolarProbePlus Survey (CGAUSS) which is the German contribution to the PSP mission as part of the Wide-field Imager for Solar PRobe. Aim. We present an empirical solar-wind model for the inner heliosphere which is derived from OMNI and Helios data. The German-US space probes Helios 1 and Helios 2 flew in the 1970s and observed solar wind in the ecliptic within heliocentric distances of 0.29 au to 0.98 au. The OMNI database consists of multi-spacecraft intercalibrated in situ data obtained near 1 au over more than five solar cycles. The international sunspot number (SSN) and its predictions are used to derive dependencies of the major solar-wind parameters on solar activity and to forecast their properties for the PSP mission. Methods: The frequency distributions for the solar-wind key parameters, magnetic field strength, proton velocity, density, and temperature, are represented by lognormal functions. In addition, we consider the velocity distributions bi-componental shape, consisting of a slower and a faster part. Functional relations to solar activity are compiled with use of the OMNI data by correlating and fitting the frequency distributions with the SSN. Further, based on the combined data set from both Helios probes, the parameters frequency distributions are fitted with respect to solar distance to obtain power law dependencies. Thus an empirical solar-wind model for the inner heliosphere confined to the ecliptic region is derived, accounting for solar activity and for solar distance through adequate shifts of the lognormal distributions. Finally, the inclusion of SSN predictions and the extrapolation down to PSPs perihelion region enables us to estimate the solar-wind environment for PSPs planned trajectory during its mission duration. Results: The CGAUSS empirical solar-wind model for PSP yields dependencies on solar activity and solar distance for the solar-wind parameters' frequency distributions. The estimated solar-wind median values for PSPs first perihelion in 2018 at a solar distance of 0.16 au are 87 nT, 340 km s-1, 214 cm-3, and 503 000 K. The estimates for PSPs first closest perihelion, occurring in 2024 at 0.046 au (9.86 R⊙), are 943 nT, 290 km s-1, 2951 cm-3, and 1 930 000 K. Since the modeled velocity and temperature values below approximately 20 R⊙appear overestimated in comparison with existing observations, this suggests that PSP will directly measure solar-wind acceleration and heating processes below 20 R⊙ as planned.

Validation for Global Solar Wind Prediction Using Ulysses Comparison: Multiple Coronal and Heliospheric Models Installed at the Community Coordinated Modeling Center

NASA Technical Reports Server (NTRS)

Jian, L. K.; MacNeice, P. J.; Mays, M. L.; Taktakishvili, A.; Odstrcil, D.; Jackson, B.; Yu, H.-S.; Riley, P.; Sokolov, I. V.

2016-01-01

The prediction of the background global solar wind is a necessary part of space weather forecasting. Several coronal and heliospheric models have been installed and/or recently upgraded at the Community Coordinated Modeling Center (CCMC), including the Wang-Sheely-Arge (WSA)-Enlil model, MHD-Around-a-Sphere (MAS)-Enlil model, Space Weather Modeling Framework (SWMF), and Heliospheric tomography using interplanetary scintillation data. Ulysses recorded the last fast latitudinal scan from southern to northern poles in 2007. By comparing the modeling results with Ulysses observations over seven Carrington rotations, we have extended our third-party validation from the previous near-Earth solar wind to middle to high latitudes, in the same late declining phase of solar cycle 23. Besides visual comparison, wehave quantitatively assessed the models capabilities in reproducing the time series, statistics, and latitudinal variations of solar wind parameters for a specific range of model parameter settings, inputs, and grid configurations available at CCMC. The WSA-Enlil model results vary with three different magnetogram inputs.The MAS-Enlil model captures the solar wind parameters well, despite its underestimation of the speed at middle to high latitudes. The new version of SWMF misses many solar wind variations probably because it uses lower grid resolution than other models. The interplanetary scintillation-tomography cannot capture the latitudinal variations of solar wind well yet. Because the model performance varies with parameter settings which are optimized for different epochs or flow states, the performance metric study provided here can serve as a template that researchers can use to validate the models for the time periods and conditions of interest to them.

Validation for global solar wind prediction using Ulysses comparison: Multiple coronal and heliospheric models installed at the Community Coordinated Modeling Center

NASA Astrophysics Data System (ADS)

Jian, L. K.; MacNeice, P. J.; Mays, M. L.; Taktakishvili, A.; Odstrcil, D.; Jackson, B.; Yu, H.-S.; Riley, P.; Sokolov, I. V.

2016-08-01

The prediction of the background global solar wind is a necessary part of space weather forecasting. Several coronal and heliospheric models have been installed and/or recently upgraded at the Community Coordinated Modeling Center (CCMC), including the Wang-Sheely-Arge (WSA)-Enlil model, MHD-Around-a-Sphere (MAS)-Enlil model, Space Weather Modeling Framework (SWMF), and heliospheric tomography using interplanetary scintillation data. Ulysses recorded the last fast latitudinal scan from southern to northern poles in 2007. By comparing the modeling results with Ulysses observations over seven Carrington rotations, we have extended our third-party validation from the previous near-Earth solar wind to middle to high latitudes, in the same late declining phase of solar cycle 23. Besides visual comparison, we have quantitatively assessed the models' capabilities in reproducing the time series, statistics, and latitudinal variations of solar wind parameters for a specific range of model parameter settings, inputs, and grid configurations available at CCMC. The WSA-Enlil model results vary with three different magnetogram inputs. The MAS-Enlil model captures the solar wind parameters well, despite its underestimation of the speed at middle to high latitudes. The new version of SWMF misses many solar wind variations probably because it uses lower grid resolution than other models. The interplanetary scintillation-tomography cannot capture the latitudinal variations of solar wind well yet. Because the model performance varies with parameter settings which are optimized for different epochs or flow states, the performance metric study provided here can serve as a template that researchers can use to validate the models for the time periods and conditions of interest to them.

Performance assessment of different day-of-the-year-based models for estimating global solar radiation - Case study: Egypt

NASA Astrophysics Data System (ADS)

Hassan, Gasser E.; Youssef, M. Elsayed; Ali, Mohamed A.; Mohamed, Zahraa E.; Shehata, Ali I.

2016-11-01

Different models are introduced to predict the daily global solar radiation in different locations but there is no specific model based on the day of the year is proposed for many locations around the world. In this study, more than 20 years of measured data for daily global solar radiation on a horizontal surface are used to develop and validate seven models to estimate the daily global solar radiation by day of the year for ten cities around Egypt as a case study. Moreover, the generalization capability for the best models is examined all over the country. The regression analysis is employed to calculate the coefficients of different suggested models. The statistical indicators namely, RMSE, MABE, MAPE, r and R2 are calculated to evaluate the performance of the developed models. Based on the validation with the available data, the results show that the hybrid sine and cosine wave model and 4th order polynomial model have the best performance among other suggested models. Consequently, these two models coupled with suitable coefficients can be used for estimating the daily global solar radiation on a horizontal surface for each city, and also for all the locations around the studied region. It is believed that the established models in this work are applicable and significant for quick estimation for the average daily global solar radiation on a horizontal surface with higher accuracy. The values of global solar radiation generated by this approach can be utilized in the design and estimation of the performance of different solar applications.

Modeling of the Electric Characteristics of Solar Cells

NASA Astrophysics Data System (ADS)

Logan, Benjamin; Tzolov, Marian

The purpose of a solar cell is to covert solar energy, through means of photovoltaic action, into a sustainable electrical current that produces usable electricity. The electrical characteristics of solar cells can be modeled to better understand how they function. As an electrical device, solar cells can be conveniently represented as an equivalent electrical circuit with an ideal diode, ideal current source for the photovoltaic action, a shunt resistor for recombination, a resistor in series to account for contact resistance, and a resistor modeling external power consumption. The values of these elements have been modified to model dark and illumination states. Fitting the model to the experimental current voltage characteristics allows to determine the values of the equivalent circuit elements. Comparing values of open circuit voltage, short circuit current, and shunt resistor can determine factors such as the amount of recombination to diagnose problems in solar cells. The many measurable quantities of a solar cell's characteristics give guidance for the design when they are related with microscopic processes.

An IBM PC-based math model for space station solar array simulation

NASA Technical Reports Server (NTRS)

Emanuel, E. M.

1986-01-01

This report discusses and documents the design, development, and verification of a microcomputer-based solar cell math model for simulating the Space Station's solar array Initial Operational Capability (IOC) reference configuration. The array model is developed utilizing a linear solar cell dc math model requiring only five input parameters: short circuit current, open circuit voltage, maximum power voltage, maximum power current, and orbit inclination. The accuracy of this model is investigated using actual solar array on orbit electrical data derived from the Solar Array Flight Experiment/Dynamic Augmentation Experiment (SAFE/DAE), conducted during the STS-41D mission. This simulator provides real-time simulated performance data during the steady state portion of the Space Station orbit (i.e., array fully exposed to sunlight). Eclipse to sunlight transients and shadowing effects are not included in the analysis, but are discussed briefly. Integrating the Solar Array Simulator (SAS) into the Power Management and Distribution (PMAD) subsystem is also discussed.

Multifluid Simulations of the Global Solar Wind Including Pickup Ions and Turbulence Modeling

NASA Technical Reports Server (NTRS)

Goldstein, Melvyn L.; Usmanov, A. V.

2011-01-01

I will describe a three-dimensional magnetohydrodynamic model of the solar wind that takes into account turbulent heating of the wind by velocity and magnetic fluctuations as well as a variety of effects produced by interstellar pickup protons. The interstellar pickup protons are treated in the model as one fluid and the protons and electrons are treated together as a second fluid. The model equations include a Reynolds decomposition of the plasma velocity and magnetic field into mean and fluctuating quantities, as well as energy transfer from interstellar pickup protons to solar wind protons that results in the deceleration of the solar wind. The model is used to simulate the global steady-state structure of the solar wind in the region from 0.3 to 100 AU. The simulation assumes that the background magnetic field on the Sun is either a dipole (aligned or tilted with respect to the solar rotation axis) or one that is deduced from solar magnetograms.

Updated Model of the Solar Energetic Proton Environment in Space

NASA Astrophysics Data System (ADS)

Jiggens, Piers; Heynderickx, Daniel; Sandberg, Ingmar; Truscott, Pete; Raukunen, Osku; Vainio, Rami

2018-05-01

The Solar Accumulated and Peak Proton and Heavy Ion Radiation Environment (SAPPHIRE) model provides environment specification outputs for all aspects of the Solar Energetic Particle (SEP) environment. The model is based upon a thoroughly cleaned and carefully processed data set. Herein the evolution of the solar proton model is discussed with comparisons to other models and data. This paper discusses the construction of the underlying data set, the modelling methodology, optimisation of fitted flux distributions and extrapolation of model outputs to cover a range of proton energies from 0.1 MeV to 1 GeV. The model provides outputs in terms of mission cumulative fluence, maximum event fluence and peak flux for both solar maximum and solar minimum periods. A new method for describing maximum event fluence and peak flux outputs in terms of 1-in-x-year SPEs is also described. SAPPHIRE proton model outputs are compared with previous models including CREME96, ESP-PSYCHIC and the JPL model. Low energy outputs are compared to SEP data from ACE/EPAM whilst high energy outputs are compared to a new model based on GLEs detected by Neutron Monitors (NMs).

Three-Dimensional MHD Modeling of The Solar Corona and Solar Wind: Comparison with The Wang-Sheeley Model

NASA Technical Reports Server (NTRS)

Usmanov, A. V.; Goldstein, M. L.

2003-01-01

We present simulation results from a tilted-dipole steady-state MHD model of the solar corona and solar wind and compare the output from our model with the Wang-Sheeley model which relates the divergence rate of magnetic flux tubes near the Sun (inferred from solar magnetograms) to the solar wind speed observed near Earth and at Ulysses. The boundary conditions in our model specified at the coronal base and our simulation region extends out to 10 AU. We assumed that a flux of Alfven waves with amplitude of 35 km per second emanates from the Sun and provides additional heating and acceleration for the coronal outflow in the open field regions. The waves are treated in the WKB approximation. The incorporation of wave acceleration allows us to reproduce the fast wind measurements obtained by Ulysses, while preserving reasonable agreement with plasma densities typically found at the coronal base. We find that our simulation results agree well with Wang and Sheeley's empirical model.

On solar geoengineering and climate uncertainty

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacMartin, Douglas; Kravitz, Benjamin S.; Rasch, Philip J.

2015-09-03

Uncertainty in the climate system response has been raised as a concern regarding solar geoengineering. Here we show that model projections of regional climate change outcomes may have greater agreement under solar geoengineering than with CO2 alone. We explore the effects of geoengineering on one source of climate system uncertainty by evaluating the inter-model spread across 12 climate models participating in the Geoengineering Model Intercomparison project (GeoMIP). The model spread in regional temperature and precipitation changes is reduced with CO2 and a solar reduction, in comparison to the case with increased CO2 alone. That is, the intermodel spread in predictionsmore » of climate change and the model spread in the response to solar geoengineering are not additive but rather partially cancel. Furthermore, differences in efficacy explain most of the differences between models in their temperature response to an increase in CO2 that is offset by a solar reduction. These conclusions are important for clarifying geoengineering risks.« less

A model for solar constant secular changes

NASA Technical Reports Server (NTRS)

Schatten, Kenneth H.

1988-01-01

In this paper, contrast models for solar active region and global photospheric features are used to reproduce the observed Active Cavity Radiometer and Earth Radiation Budget secular trends in reasonably good fashion. A prediction for the next decade of solar constant variations is made using the model. Secular trends in the solar constant obtained from the present model support the view that the Maunder Minimum may be related to the Little Ice Age of the 17th century.

Solar Measurement and Modeling | Grid Modernization | NREL

Science.gov Websites

Energy SunShot Initiative by improving the tools and methods that measure solar radiation to reduce and disseminate accurate solar measurement and modeling methods, best practices and standards, and Normal Irradiance Measurements, Solar Energy (2016) Radiometer Calibration Methods and Resulting

The MSFC Solar Activity Future Estimation (MSAFE) Model

NASA Technical Reports Server (NTRS)

Suggs, Ronnie J.

2017-01-01

The MSAFE model provides forecasts for the solar indices SSN, F10.7, and Ap. These solar indices are used as inputs to many space environment models used in orbital spacecraft operations and space mission analysis. Forecasts from the MSAFE model are provided on the MSFC Natural Environments Branch's solar webpage and are updated as new monthly observations come available. The MSAFE prediction routine employs a statistical technique that calculates deviations of past solar cycles from the mean cycle and performs a regression analysis to predict the deviation from the mean cycle of the solar index at the next future time interval. The prediction algorithm is applied recursively to produce monthly smoothed solar index values for the remaining of the cycle. The forecasts are initiated for a given cycle after about 8 to 12 months of observations are collected. A forecast made at the beginning of cycle 24 using the MSAFE program captured the cycle fairly well with some difficulty in discerning the double peak that occurred at solar cycle maximum.

The MSFC Solar Activity Future Estimation (MSAFE) Model

NASA Technical Reports Server (NTRS)

Suggs, Ron

2017-01-01

The Natural Environments Branch of the Engineering Directorate at Marshall Space Flight Center (MSFC) provides solar cycle forecasts for NASA space flight programs and the aerospace community. These forecasts provide future statistical estimates of sunspot number, solar radio 10.7 cm flux (F10.7), and the geomagnetic planetary index, Ap, for input to various space environment models. For example, many thermosphere density computer models used in spacecraft operations, orbital lifetime analysis, and the planning of future spacecraft missions require as inputs the F10.7 and Ap. The solar forecast is updated each month by executing MSAFE using historical and the latest month's observed solar indices to provide estimates for the balance of the current solar cycle. The forecasted solar indices represent the 13-month smoothed values consisting of a best estimate value stated as a 50 percentile value along with approximate +/- 2 sigma values stated as 95 and 5 percentile statistical values. This presentation will give an overview of the MSAFE model and the forecast for the current solar cycle.

A parametric simulation of solar chimney power plant

NASA Astrophysics Data System (ADS)

Beng Hooi, Lim; Kannan Thangavelu, Saravana

2018-01-01

The strong solar radiation, continuous supplies of sunlight and environmental friendly factors have made the solar chimney power plant becoming highly feasible to build in Malaysia. Solar chimney power plant produces upward buoyancy force through the greenhouse effect. Numerical simulation was performed on the model of a solar chimney power plant using the ANSYS Fluent software by applying standard k-epsilon turbulence model and discrete ordinates (DO) radiation model to solve the relevant equations. A parametric study was carried out to evaluate the performance of solar chimney power plant, which focused on the temperature rise in the collector, air velocity at the chimney base, and pressure drop inside the chimney were based on the results of temperature, velocity, and static pressure distributions. The results demonstrate reliability by comparing a model with the experimental data of Manzanares Spanish prototype. Based on the numerical results, power capacity and efficiency were analysed theoretically. Results indicate that a stronger solar radiation and larger prototype will improve the performance of solar chimney power plant.

Estimation of available global solar radiation using sunshine duration over South Korea

NASA Astrophysics Data System (ADS)

Das, Amrita; Park, Jin-ki; Park, Jong-hwa

2015-11-01

Besides designing a solar energy system, accurate insolation data is also a key component for many biological and atmospheric studies. But solar radiation stations are not widely available due to financial and technical limitations; this insufficient number affects the spatial resolution whenever an attempt is made to construct a solar radiation map. There are several models in literature for estimating incoming solar radiation using sunshine fraction. Seventeen of such models among which 6 are linear and 11 non-linear, have been chosen for studying and estimating solar radiation on a horizontal surface over South Korea. The better performance of a non-linear model signifies the fact that the relationship between sunshine duration and clearness index does not follow a straight line. With such a model solar radiation over 79 stations measuring sunshine duration is computed and used as input for spatial interpolation. Finally monthly solar radiation maps are constructed using the Ordinary Kriging method. The cross validation results show good agreement between observed and predicted data.

Variation of solar cell sensitivity and solar radiation on tilted surfaces

NASA Technical Reports Server (NTRS)

Klucher, T. M.

1978-01-01

An empirical study was performed (1) to evaluate the validity of various insolation models used to compute solar radiation incident on tilted surfaces from global data measured on horizontal surfaces and (2) to determine the variation of solar cell sensitivity to solar radiation over a wide range of atmospheric condition. Evaluation of the insolation data indicates that the isotropic sky model of Liu and Jordan underestimates the amount of solar radiation falling on tilted surfaces by as much as 10%. An anisotropic-clear-sky model proposed by Temps and Coulson was also evaluated and found to be deficient under cloudy conditions. A new model, formulated herein, reduced the deviations between measured and predicted insolation to less than 3%. Evaluation of solar cell sensitivity data indicates small change (2-3%) in sensitivity from winter to summer for tilted cells. The feasibility of using such global data as a means for calibrating terrestrial solar cells as done by Treble is discussed.

The Role of Structural Models in the Solar Sail Flight Validation Process

NASA Technical Reports Server (NTRS)

Johnston, John D.

2004-01-01

NASA is currently soliciting proposals via the New Millennium Program ST-9 opportunity for a potential Solar Sail Flight Validation (SSFV) experiment to develop and operate in space a deployable solar sail that can be steered and provides measurable acceleration. The approach planned for this experiment is to test and validate models and processes for solar sail design, fabrication, deployment, and flight. These models and processes would then be used to design, fabricate, and operate scaleable solar sails for future space science missions. There are six validation objectives planned for the ST9 SSFV experiment: 1) Validate solar sail design tools and fabrication methods; 2) Validate controlled deployment; 3) Validate in space structural characteristics (focus of poster); 4) Validate solar sail attitude control; 5) Validate solar sail thrust performance; 6) Characterize the sail's electromagnetic interaction with the space environment. This poster presents a top-level assessment of the role of structural models in the validation process for in-space structural characteristics.

FIRST NEW SOLAR MODELS WITH OPAS OPACITY TABLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Pennec, M.; Turck-Chièze, S.; Salmon, S.

Stellar seismology appears more and more as a powerful tool for a better determination of the fundamental properties of solar-type stars. However, the particular case of the Sun is still challenging. For about a decade now, the helioseismic sound-speed determination has continued to disagree with the standard solar model (SSM) prediction, questioning the reliability of this model. One of the sources of uncertainty could be in the treatment of the transport of radiation from the solar core to the surface. In this Letter, we use the new OPAS opacity tables, recently available for solar modeling, to address this issue. Wemore » discuss first the peculiarities of these tables, then we quantify their impact on the solar sound-speed and density profiles using the reduced OPAS tables taken on the grids of the OPAL ones. We use the two evolution codes, Modules for Experiments in Stellar Astrophysics and Code Liégeois d’Evolution Stellaire, that led to similar conclusions in the solar radiative zone. In comparison to commonly used OPAL opacity tables, the new solar models are computed for the most recent photospheric composition with OPAS tables and present improvements to the location of the base of the convective zone and to the description of the solar radiative zone in comparison to the helioseismic observations, even if the differences in the Rosseland mean opacity do not exceed 6%. We finally carry out a comparison to a solar model computed with the OP opacity tables.« less

Sensitivity of solar g-modes to varying G cosmologies

NASA Technical Reports Server (NTRS)

Guenther, D. B.; Sills, Ken; Demarque, Pierre; Krauss, Lawrence M.

1995-01-01

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.

The MSFC Solar Activity Future Estimation (MSAFE) Model

NASA Technical Reports Server (NTRS)

Suggs, Ron

2017-01-01

The MSAFE model provides forecasts for the solar indices SSN, F10.7, and Ap. These solar indices are used as inputs to space environment models used in orbital spacecraft operations and space mission analysis. Forecasts from the MSAFE model are provided on the MSFC Natural Environments Branch's solar web page and are updated as new monthly observations become available. The MSAFE prediction routine employs a statistical technique that calculates deviations of past solar cycles from the mean cycle and performs a regression analysis to calculate the deviation from the mean cycle of the solar index at the next future time interval. The forecasts are initiated for a given cycle after about 8 to 9 monthly observations from the start of the cycle are collected. A forecast made at the beginning of cycle 24 using the MSAFE program captured the cycle fairly well with some difficulty in discerning the double peak that occurred at solar cycle maximum.

An improved electrothermal model for the ERBE nonscanning radiometer - Comparison of predicted and measured behavior during solar observations

NASA Technical Reports Server (NTRS)

Tira, Nour E.; Mahan, J. R.; Lee, Robert B., III

1989-01-01

The improved Earth Radiation Budget Experiment nonscanning-channels electrothermal model presented is used to model two types of solar observations: those obtained through the solar port during solar calibration, and and those obtained during the satellite pitch-over maneuver, in which the sun is observed by the radiometer while it is in earth-viewing configuration. Thermal noise has been separately studied to evaluate its contribution to the radiative energy absorbed by the active cavity. It is found that the scattering of the collimated solar radiation contributes an average of 0.071 mW during solar calibration.

Worldwide multi-model intercomparison of clear-sky solar irradiance predictions

NASA Astrophysics Data System (ADS)

Ruiz-Arias, Jose A.; Gueymard, Christian A.; Cebecauer, Tomas

2017-06-01

Accurate modeling of solar radiation in the absence of clouds is highly important because solar power production peaks during cloud-free situations. The conventional validation approach of clear-sky solar radiation models relies on the comparison between model predictions and ground observations. Therefore, this approach is limited to locations with availability of high-quality ground observations, which are scarce worldwide. As a consequence, many areas of in-terest for, e.g., solar energy development, still remain sub-validated. Here, a worldwide inter-comparison of the global horizontal irradiance (GHI) and direct normal irradiance (DNI) calculated by a number of appropriate clear-sky solar ra-diation models is proposed, without direct intervention of any weather or solar radiation ground-based observations. The model inputs are all gathered from atmospheric reanalyses covering the globe. The model predictions are compared to each other and only their relative disagreements are quantified. The largest differences between model predictions are found over central and northern Africa, the Middle East, and all over Asia. This coincides with areas of high aerosol optical depth and highly varying aerosol distribution size. Overall, the differences in modeled DNI are found about twice larger than for GHI. It is argued that the prevailing weather regimes (most importantly, aerosol conditions) over regions exhibiting substantial divergences are not adequately parameterized by all models. Further validation and scrutiny using conventional methods based on ground observations should be pursued in priority over those specific regions to correctly evaluate the performance of clear-sky models, and select those that can be recommended for solar concentrating applications in particular.

One-Dimensional Fast Transient Simulator for Modeling Cadmium Sulfide/Cadmium Telluride Solar Cells

NASA Astrophysics Data System (ADS)

Guo, Da

Solar energy, including solar heating, solar architecture, solar thermal electricity and solar photovoltaics, is one of the primary alternative energy sources to fossil fuel. Being one of the most important techniques, significant research has been conducted in solar cell efficiency improvement. Simulation of various structures and materials of solar cells provides a deeper understanding of device operation and ways to improve their efficiency. Over the last two decades, polycrystalline thin-film Cadmium-Sulfide and Cadmium-Telluride (CdS/CdTe) solar cells fabricated on glass substrates have been considered as one of the most promising candidate in the photovoltaic technologies, for their similar efficiency and low costs when compared to traditional silicon-based solar cells. In this work a fast one dimensional time-dependent/steady-state drift-diffusion simulator, accelerated by adaptive non-uniform mesh and automatic time-step control, for modeling solar cells has been developed and has been used to simulate a CdS/CdTe solar cell. These models are used to reproduce transients of carrier transport in response to step-function signals of different bias and varied light intensity. The time-step control models are also used to help convergence in steady-state simulations where constrained material constants, such as carrier lifetimes in the order of nanosecond and carrier mobility in the order of 100 cm2/Vs, must be applied.

Propagation of Interplanetary Disturbances in the Outer Heliosphere

NASA Technical Reports Server (NTRS)

Wang, Chi

2005-01-01

Contents include the following: 1. We have developed a one-dimensional, spherically symmetric, multi-fluid MHD model that includes solar wind protons and electrons, pickup ions, and interstellar neutral hydrogen. This model advances the existing solar wind models for the outer heliosphere in two important ways: one is that it distinguishes solar wind protons from pickup ions, and the other is that it allows for energy transfer from pickup ions to the solar wind protons. Model results compare favorably with the Voyager 2 observations. 2. 2. Solar wind slowdown and interstellar neutral density. The solar wind in the outer heliosphere is fundamentally different from that in the inner heliosphere since the effects of interstellar neutrals become significant. 3. ICME propagation from the inner to outer heliosphere. Large coronal mass ejections (CMEs) have major effects on the structure of the solar wind and the heliosphere. The plasma and magnetic field can be compressed ahead of interplanetary CMEs. 4. During the current solar cycle (Cycle 23), several major CMEs associated with solar flares produced large transient shocks which were observed by widely-separated spacecraft such as Wind at Earth and Voyager 2 beyond 60 AU. Using data from these spacecraft, we use the multi-fluid model to investigate shock propagation and interaction in the heliosphere. Specifically, we studied the Bastille Day 2000, April 2001 and Halloween 2003 events. 5. Statistical properties of the solar wind in the outer heliosphere. In a collaboration with L.F. Burlaga of GSFC, it is shown that the basic statistical properties of the solar wind in the outer heliosphere can be well produced by our model. We studied the large-scale heliospheric magnetic field strength fluctuations as a function of distance from the Sun during the declining phase of a solar cycle, using our numerical model with observations made at 1 AU during 1995 as input. 6. Radial heliospheric magnetic field events. The heliospheric magnetic field (HMF) direction, on average, conforms well to the Parker spiral.

Taking Venus models to new dimensions.

NASA Astrophysics Data System (ADS)

Murawski, K.

1997-11-01

Space plasma physicists in Poland and Japan have gained new insights into the interaction between the solar wind and Venus. Computer simulations of this 3D global interaction between the solar wind and nonmagnetized bodies have enabled greater understanding of the large-scale processes involved in such phenomena. A model that offers improved understanding of the solar wind interaction with Venus (as well as other nonmagnetized bodies impacted by the solar wind) has been developed. In this model, the interaction of the solar wind with the ionosphere of Venus is studied by calculating numerical solutions of the 3D MHD equations for two-component, chemically reactive plasma. The author describes the innovative model.

Analysis of Solar Cell Efficiency for Venus Atmosphere and Surface Missions

NASA Technical Reports Server (NTRS)

Landis, Geoffrey A.; Haag, Emily

2013-01-01

A simplified model of solar power in the Venus environment is developed, in which the solar intensity, solar spectrum, and temperature as a function of altitude is applied to a model of photovoltaic performance, incorporating the temperature and intensity dependence of the open-circuit voltage and the temperature dependence of the bandgap and spectral response of the cell. We use this model to estimate the performance of solar cells for both the surface of Venus and for atmospheric probes at altitudes from the surface up to 60 km. The model shows that photovoltaic cells will produce power even at the surface of Venus.

On the radial evolution of reflection-driven turbulence in the inner solar wind in preparation for Parker Solar Probe

NASA Astrophysics Data System (ADS)

Perez, J. C.; Chandran, B. D. G.

2017-12-01

In this work we present recent results from high-resolution direct numerical simulations and a phenomenological model that describes the radial evolution of reflection-driven Alfven Wave turbulence in the solar atmosphere and the inner solar wind. The simulations are performed inside a narrow magnetic flux tube that models a coronal hole extending from the solar surface through the chromosphere and into the solar corona to approximately 21 solar radii. The simulations include prescribed empirical profiles that account for the inhomogeneities in density, background flow, and the background magnetic field present in coronal holes. Alfven waves are injected into the solar corona by imposing random, time-dependent velocity and magnetic field fluctuations at the photosphere. The phenomenological model incorporates three important features observed in the simulations: dynamic alignment, weak/strong nonlinear AW-AW interactions, and that the outward-propagating AWs launched by the Sun split into two populations with different characteristic frequencies. Model and simulations are in good agreement and show that when the key physical parameters are chosen within observational constraints, reflection-driven Alfven turbulence is a plausible mechanism for the heating and acceleration of the fast solar wind. By flying a virtual Parker Solar Probe (PSP) through the simulations, we will also establish comparisons between the model and simulations with the kind of single-point measurements that PSP will provide.

Short-term prediction of solar energy in Saudi Arabia using automated-design fuzzy logic systems

PubMed Central

2017-01-01

Solar energy is considered as one of the main sources for renewable energy in the near future. However, solar energy and other renewable energy sources have a drawback related to the difficulty in predicting their availability in the near future. This problem affects optimal exploitation of solar energy, especially in connection with other resources. Therefore, reliable solar energy prediction models are essential to solar energy management and economics. This paper presents work aimed at designing reliable models to predict the global horizontal irradiance (GHI) for the next day in 8 stations in Saudi Arabia. The designed models are based on computational intelligence methods of automated-design fuzzy logic systems. The fuzzy logic systems are designed and optimized with two models using fuzzy c-means clustering (FCM) and simulated annealing (SA) algorithms. The first model uses FCM based on the subtractive clustering algorithm to automatically design the predictor fuzzy rules from data. The second model is using FCM followed by simulated annealing algorithm to enhance the prediction accuracy of the fuzzy logic system. The objective of the predictor is to accurately predict next-day global horizontal irradiance (GHI) using previous-day meteorological and solar radiation observations. The proposed models use observations of 10 variables of measured meteorological and solar radiation data to build the model. The experimentation and results of the prediction are detailed where the root mean square error of the prediction was approximately 88% for the second model tuned by simulated annealing compared to 79.75% accuracy using the first model. This results demonstrate a good modeling accuracy of the second model despite that the training and testing of the proposed models were carried out using spatially and temporally independent data. PMID:28806754

Short-term prediction of solar energy in Saudi Arabia using automated-design fuzzy logic systems.

PubMed

Almaraashi, Majid

2017-01-01

Solar energy is considered as one of the main sources for renewable energy in the near future. However, solar energy and other renewable energy sources have a drawback related to the difficulty in predicting their availability in the near future. This problem affects optimal exploitation of solar energy, especially in connection with other resources. Therefore, reliable solar energy prediction models are essential to solar energy management and economics. This paper presents work aimed at designing reliable models to predict the global horizontal irradiance (GHI) for the next day in 8 stations in Saudi Arabia. The designed models are based on computational intelligence methods of automated-design fuzzy logic systems. The fuzzy logic systems are designed and optimized with two models using fuzzy c-means clustering (FCM) and simulated annealing (SA) algorithms. The first model uses FCM based on the subtractive clustering algorithm to automatically design the predictor fuzzy rules from data. The second model is using FCM followed by simulated annealing algorithm to enhance the prediction accuracy of the fuzzy logic system. The objective of the predictor is to accurately predict next-day global horizontal irradiance (GHI) using previous-day meteorological and solar radiation observations. The proposed models use observations of 10 variables of measured meteorological and solar radiation data to build the model. The experimentation and results of the prediction are detailed where the root mean square error of the prediction was approximately 88% for the second model tuned by simulated annealing compared to 79.75% accuracy using the first model. This results demonstrate a good modeling accuracy of the second model despite that the training and testing of the proposed models were carried out using spatially and temporally independent data.

Studies of the Solar Radiations' Influence About Geomembranes Used in Ecological Landfill

NASA Astrophysics Data System (ADS)

Vasiluta, Petre; Cofaru, Ileana Ioana; Cofaru, Nicolae Florin; Popa, Dragos Laurentiu

2017-12-01

The study shown in this paper presents the behavior of geomembranes used at the ecological landfills. The influences of the solar radiations has a great importance regarding the correct mounting of the geomembranes. The mathematical model developed for the determination anytime and anywhere in the world for the next values and parameters: apparent solar time, solar declination, solar altitude, solar azimuth and incidence angle, zone angle, angle of sun elevation, solar declination, solar constant, solar flux density, diffuse solar radiation, global radiation, soil albedo, total radiant flux density and relational links of these values. The results of this model was used for creations an AutoCAD subroutines useful for choosing the correct time for correct mounting anywhere of the geomembranes

The solar cycle; Proceedings of the National Solar Observatory/Sacramento Peak 12th Summer Workshop, Sunspot, NM, Oct. 15-18, 1991

NASA Technical Reports Server (NTRS)

Harvey, Karen L. (Editor)

1992-01-01

Attention is given to a flux-transport model, the effect of fractal distribution on the evolution of solar surface magnetic fields, active nests on the sun, magnetic flux transport in solar active regions, recent advances in stellar cycle research, magnetic intermittency on the sun, a search for existence of large-scale motions on the sun, and new solar cycle data from the NASA/NSO spectromagnetograph. Attention is also given to the solar cycle variation of coronal temperature during cycle 22, the distribution of the north-south asymmetry for the various activity cycles, solar luminosity variation, a two-parameter model of total solar irradiance variation over the solar cycle, the origin of the solar cycle, nonlinear feedbacks in the solar dynamo, and long-term dynamics of the solar cycle.

Future Directions in Simulating Solar Geoengineering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kravitz, Benjamin S.; Robock, Alan; Boucher, Olivier

2014-08-05

Solar geoengineering is a proposed set of technologies to temporarily alleviate some of the consequences of anthropogenic greenhouse gas emissions. The Geoengineering Model Intercomparison Project (GeoMIP) created a framework of geoengineering simulations in climate models that have been performed by modeling centers throughout the world (B. Kravitz et al., The Geoengineering Model Intercomparison Project (GeoMIP), Atmospheric Science Letters, 12(2), 162-167, doi:10.1002/asl.316, 2011). These experiments use state-of-the-art climate models to simulate solar geoengineering via uniform solar reduction, creation of stratospheric sulfate aerosol layers, or injecting sea spray into the marine boundary layer. GeoMIP has been quite successful in its mission ofmore » revealing robust features and key uncertainties of the modeled effects of solar geoengineering.« less

Using Data Assimilation Methods of Prediction of Solar Activity

NASA Technical Reports Server (NTRS)

Kitiashvili, Irina N.; Collins, Nancy S.

2017-01-01

The variable solar magnetic activity known as the 11-year solar cycle has the longest history of solar observations. These cycles dramatically affect conditions in the heliosphere and the Earth's space environment. Our current understanding of the physical processes that make up global solar dynamics and the dynamo that generates the magnetic fields is sketchy, resulting in unrealistic descriptions in theoretical and numerical models of the solar cycles. The absence of long-term observations of solar interior dynamics and photospheric magnetic fields hinders development of accurate dynamo models and their calibration. In such situations, mathematical data assimilation methods provide an optimal approach for combining the available observational data and their uncertainties with theoretical models in order to estimate the state of the solar dynamo and predict future cycles. In this presentation, we will discuss the implementation and performance of an Ensemble Kalman Filter data assimilation method based on the Parker migratory dynamo model, complemented by the equation of magnetic helicity conservation and long-term sunspot data series. This approach has allowed us to reproduce the general properties of solar cycles and has already demonstrated a good predictive capability for the current cycle, 24. We will discuss further development of this approach, which includes a more sophisticated dynamo model, synoptic magnetogram data, and employs the DART Data Assimilation Research Testbed.

Early Estimation of Solar Activity Cycle: Potential Capability and Limits

NASA Technical Reports Server (NTRS)

Kitiashvili, Irina N.; Collins, Nancy S.

2017-01-01

The variable solar magnetic activity known as the 11-year solar cycle has the longest history of solar observations. These cycles dramatically affect conditions in the heliosphere and the Earth's space environment. Our current understanding of the physical processes that make up global solar dynamics and the dynamo that generates the magnetic fields is sketchy, resulting in unrealistic descriptions in theoretical and numerical models of the solar cycles. The absence of long-term observations of solar interior dynamics and photospheric magnetic fields hinders development of accurate dynamo models and their calibration. In such situations, mathematical data assimilation methods provide an optimal approach for combining the available observational data and their uncertainties with theoretical models in order to estimate the state of the solar dynamo and predict future cycles. In this presentation, we will discuss the implementation and performance of an Ensemble Kalman Filter data assimilation method based on the Parker migratory dynamo model, complemented by the equation of magnetic helicity conservation and longterm sunspot data series. This approach has allowed us to reproduce the general properties of solar cycles and has already demonstrated a good predictive capability for the current cycle, 24. We will discuss further development of this approach, which includes a more sophisticated dynamo model, synoptic magnetogram data, and employs the DART Data Assimilation Research Testbed.

Solar Radiation Estimated Through Mesoscale Atmospheric Modeling over Northeast Brazil

NASA Astrophysics Data System (ADS)

de Menezes Neto, Otacilio Leandro; Costa, Alexandre Araújo; Ramalho, Fernando Pinto; de Maria, Paulo Henrique Santiago

2009-03-01

The use of renewable energy sources, like solar, wind and biomass is rapidly increasing in recent years, with solar radiation as a particularly abundant energy source over Northeast Brazil. A proper quantitative knowledge of the incoming solar radiation is of great importance for energy planning in Brazil, serving as basis for developing future projects of photovoltaic power plants and solar energy exploitation. This work presents a methodology for mapping the incoming solar radiation at ground level for Northeast Brazil, using a mesoscale atmospheric model (Regional Atmospheric Modeling System—RAMS), calibrated and validated using data from the network of automatic surface stations from the State Foundation for Meteorology and Water Resources from Ceará (Fundação Cearense de Meteorologia e Recursos Hídricos- FUNCEME). The results showed that the model exhibits systematic errors, overestimating surface radiation, but that, after the proper statistical corrections, using a relationship between the model-predicted cloud fraction, the ground-level observed solar radiation and the incoming solar radiation estimated at the top of the atmosphere, a correlation of 0.92 with a confidence interval of 13.5 W/m2 is found for monthly data. Using this methodology, we found an estimate for annual average incoming solar radiation over Ceará of 215 W/m2 (maximum in October: 260 W/m2).

The virtual enhancements - solar proton event radiation (VESPER) model

NASA Astrophysics Data System (ADS)

Aminalragia-Giamini, Sigiava; Sandberg, Ingmar; Papadimitriou, Constantinos; Daglis, Ioannis A.; Jiggens, Piers

2018-02-01

A new probabilistic model introducing a novel paradigm for the modelling of the solar proton environment at 1 AU is presented. The virtual enhancements - solar proton event radiation model (VESPER) uses the European space agency's solar energetic particle environment modelling (SEPEM) Reference Dataset and produces virtual time-series of proton differential fluxes. In this regard it fundamentally diverges from the approach of existing SPE models that are based on probabilistic descriptions of SPE macroscopic characteristics such as peak flux and cumulative fluence. It is shown that VESPER reproduces well the dataset characteristics it uses, and further comparisons with existing models are made with respect to their results. The production of time-series as the main output of the model opens a straightforward way for the calculation of solar proton radiation effects in terms of time-series and the pairing with effects caused by trapped radiation and galactic cosmic rays.

Comparative Validation of Realtime Solar Wind Forecasting Using the UCSD Heliospheric Tomography Model

NASA Technical Reports Server (NTRS)

MacNeice, Peter; Taktakishvili, Alexandra; Jackson, Bernard; Clover, John; Bisi, Mario; Odstrcil, Dusan

2011-01-01

The University of California, San Diego 3D Heliospheric Tomography Model reconstructs the evolution of heliospheric structures, and can make forecasts of solar wind density and velocity up to 72 hours in the future. The latest model version, installed and running in realtime at the Community Coordinated Modeling Center(CCMC), analyzes scintillations of meter wavelength radio point sources recorded by the Solar-Terrestrial Environment Laboratory(STELab) together with realtime measurements of solar wind speed and density recorded by the Advanced Composition Explorer(ACE) Solar Wind Electron Proton Alpha Monitor(SWEPAM).The solution is reconstructed using tomographic techniques and a simple kinematic wind model. Since installation, the CCMC has been recording the model forecasts and comparing them with ACE measurements, and with forecasts made using other heliospheric models hosted by the CCMC. We report the preliminary results of this validation work and comparison with alternative models.

Numerical modelling of CIGS/CdS solar cell

NASA Astrophysics Data System (ADS)

Devi, Nisha; Aziz, Anver; Datta, Shouvik

2018-05-01

In this work, we design and analyze the Cu(In,Ga)Se2 (CIGS) solar cell using simulation software "Solar Cell Capacitance Simulator in One Dimension (SCAPS-1D)". The conventional CIGS solar cell uses various layers, like intrinsic ZnO/Aluminium doped ZnO as transparent oxide, antireflection layer MgF2, and electron back reflection (EBR) layer at CIGS/Mo interface for good power conversion efficiency. We replace this conventional model by a simple model which is easy to fabricate and also reduces the cost of this cell because of use of lesser materials. The new designed model of CIGS solar cell is ITO/CIGS/OVC/CdS/Metal contact, where OVC is ordered vacancy compound. From this simple structure, even at very low illumination we are getting good results. We simulate this CIGS solar cell model by varying various physical parameters of CIGS like thickness, carrier density, band gap and temperature.

Systems analysis techniques for annual cycle thermal energy storage solar systems

NASA Astrophysics Data System (ADS)

Baylin, F.

1980-07-01

Community-scale annual cycle thermal energy storage solar systems are options for building heat and cooling. A variety of approaches are feasible in modeling ACTES solar systems. The key parameter in such efforts, average collector efficiency, is examined, followed by several approaches for simple and effective modeling. Methods are also examined for modeling building loads for structures based on both conventional and passive architectural designs. Two simulation models for sizing solar heating systems with annual storage are presented. Validation is presented by comparison with the results of a study of seasonal storage systems based on SOLANSIM, an hour-by-hour simulation. These models are presently used to examine the economic trade-off between collector field area and storage capacity. Programs directed toward developing other system components such as improved tanks and solar ponds or design tools for ACTES solar systems are examined.

Near Earth Asteroid Scout Solar Sail Thrust and Torque Model

NASA Technical Reports Server (NTRS)

Heaton, Andy; Ahmad, Naeem; Miller, Kyle

2017-01-01

The Near Earth Asteroid (NEA) Scout is a solar sail mission whose objective is to scout at least one Near Earth Asteroid to help prepare for human missions to Near Earth Asteroids. NEA Scout will launch as a secondary payload on the first SLS-Orion mission. NEA Scout will perform a small trim maneuver shortly after deploy from the spent SLS upper stage using a cold gas propulsion system, but from that point on will depend entirely on the solar sail for thrust. As such, it is important to accurately characterize the thrust of the sail in order to achieve mission success. Additionally, the solar sail creates a relatively large solar disturbance torque that must be mitigated. For early mission design studies a flat plate model of the solar sail with a fixed center of pressure was adequate, but as mission concepts and the sail design matured, greater fidelity was required. Here we discuss the progress to a three-dimensional sail model that includes the effects of tension and thermal deformation that has been derived from a large structural Finite Element Model (FEM) developed by the Langley Research Center. We have found that the deformed sail membrane affects torque relatively much more than thrust; a flat plate model could potentially model thrust well enough to close mission design studies, but a three-dimensional solar sail is essential to control system design. The three-dimensional solar sail model revealed that thermal deformations of unshielded booms would create unacceptably large solar disturbance torques. The original large FEM model was used in control and mission simulations, but was resulted in simulations with prohibitive run times. This led us to adapt the Generalized Sail Model (GSM) of Rios-Reyes. A design reference sail model has been baselined for NEA Scout and has been used to design the mission and control system for the sailcraft. Additionally, since NEA Scout uses reaction wheels for attitude pointing and control, the solar torque model is essentially to successfully design the NEA Scout momentum management control system. We have also updated the estimate of diffusivity used for the aluminized sail material based on optical testing of wrinkled sail material. The model presented here represents the current state of the art of NASA's ability to model solar sail thrust and torque.

A Bayesian estimation of the helioseismic solar age

NASA Astrophysics Data System (ADS)

Bonanno, A.; Fröhlich, H.-E.

2015-08-01

Context. The helioseismic determination of the solar age has been a subject of several studies because it provides us with an independent estimation of the age of the solar system. Aims: We present the Bayesian estimates of the helioseismic age of the Sun, which are determined by means of calibrated solar models that employ different equations of state and nuclear reaction rates. Methods: We use 17 frequency separation ratios r02(n) = (νn,l = 0-νn-1,l = 2)/(νn,l = 1-νn-1,l = 1) from 8640 days of low-ℓBiSON frequencies and consider three likelihood functions that depend on the handling of the errors of these r02(n) ratios. Moreover, we employ the 2010 CODATA recommended values for Newton's constant, solar mass, and radius to calibrate a large grid of solar models spanning a conceivable range of solar ages. Results: It is shown that the most constrained posterior distribution of the solar age for models employing Irwin EOS with NACRE reaction rates leads to t⊙ = 4.587 ± 0.007 Gyr, while models employing the Irwin EOS and Adelberger, et al. (2011, Rev. Mod. Phys., 83, 195) reaction rate have t⊙ = 4.569 ± 0.006 Gyr. Implementing OPAL EOS in the solar models results in reduced evidence ratios (Bayes factors) and leads to an age that is not consistent with the meteoritic dating of the solar system. Conclusions: An estimate of the solar age that relies on an helioseismic age indicator such as r02(n) turns out to be essentially independent of the type of likelihood function. However, with respect to model selection, abandoning any information concerning the errors of the r02(n) ratios leads to inconclusive results, and this stresses the importance of evaluating the trustworthiness of error estimates.

Oxygen Pickup Ions Measured by MAVEN Outside the Martian Bow Shock

NASA Astrophysics Data System (ADS)

Rahmati, A.; Cravens, T.; Larson, D. E.; Lillis, R. J.; Dunn, P.; Halekas, J. S.; Connerney, J. E. P.; Eparvier, F. G.; Thiemann, E.; Mitchell, D. L.; Jakosky, B. M.

2015-12-01

The MAVEN (Mars Atmosphere and Volatile EvolutioN) spacecraft entered orbit around Mars on September 21, 2014 and has since been detecting energetic oxygen pickup ions by its SEP (Solar Energetic Particles) and SWIA (Solar Wind Ion Analyzer) instruments. The oxygen pickup ions detected outside the Martian bowshock and in the upstream solar wind are associated with the extended hot oxygen exosphere of Mars, which is created mainly by the dissociative recombination of molecular oxygen ions with electrons in the ionosphere. We use analytic solutions to the equations of motion of pickup ions moving in the undisturbed upstream solar wind magnetic and motional electric fields and calculate the flux of oxygen pickup ions at the location of MAVEN. Our model calculates the ionization rate of oxygen atoms in the exosphere based on the hot oxygen densities predicted by Rahmati et al. (2014), and the sources of ionization include photo-ionization, charge exchange, and electron impact ionization. The photo-ionization frequency is calculated using the FISM (Flare Irradiance Spectral Model) solar flux model, based on MAVEN EUVM (Extreme Ultra-Violet Monitor) measurements. The frequency of charge exchange between a solar wind proton and an oxygen atom is calculated using MAVEN SWIA solar wind proton flux measurements, and the electron impact ionization frequency is calculated based on MAVEN SWEA (Solar Wind Electron Analyzer) solar wind electron flux measurements. The solar wind magnetic field used in the model is from the measurements taken by MAVEN MAG (magnetometer) in the upstream solar wind. The good agreement between our predicted pickup oxygen fluxes and the MAVEN SEP and SWIA measured ones confirms detection of oxygen pickup ions and these model-data comparisons can be used to constrain models of hot oxygen densities and photochemical escape flux.

Model for Cumulative Solar Heavy Ion Energy and LET Spectra

NASA Technical Reports Server (NTRS)

Xapsos, Mike; Barth, Janet; Stauffer, Craig; Jordan, Tom; Mewaldt, Richard

2007-01-01

A probabilistic model of cumulative solar heavy ion energy and lineary energy transfer (LET) spectra is developed for spacecraft design applications. Spectra are given as a function of confidence level, mission time period during solar maximum and shielding thickness. It is shown that long-term solar heavy ion fluxes exceed galactic cosmic ray fluxes during solar maximum for shielding levels of interest. Cumulative solar heavy ion fluences should therefore be accounted for in single event effects rate calculations and in the planning of space missions.

Solar flux variability and the lifetimes of cometary H2O and OH

NASA Astrophysics Data System (ADS)

Budzien, S. A.; Festou, M. C.; Feldman, P. D.

1994-01-01

A solar EUV/FUV flux model based on recent SUSIM solar observations is presented. It is shown that both the fluxes and variabilities of the model are more consistent with SME and SUSIM solar spectrum measurements than those of the SERF1 model. It is calculated that photodissociation accounts for about 80 percent of the H2O destruction rate, while photoionization and solar wind particle interactions each account for about 10 percent of the H2O destruction. The calculated H2O and OH lifetimes against direct photodissociation both vary by 30 percent with solar activity. The major destruction channel for OH is predissociation, while direct photodissociation and solar wind interactions account for roughly 30 and 10 percent of the destruction rate, respectively.

Solar Spectral Irradiance Variations in 240 - 1600 nm During the Recent Solar Cycles 21 - 23

NASA Astrophysics Data System (ADS)

Pagaran, J.; Weber, M.; Deland, M. T.; Floyd, L. E.; Burrows, J. P.

2011-08-01

Regular solar spectral irradiance (SSI) observations from space that simultaneously cover the UV, visible (vis), and the near-IR (NIR) spectral region began with SCIAMACHY aboard ENVISAT in August 2002. Up to now, these direct observations cover less than a decade. In order for these SSI measurements to be useful in assessing the role of the Sun in climate change, records covering more than an eleven-year solar cycle are required. By using our recently developed empirical SCIA proxy model, we reconstruct daily SSI values over several decades by using solar proxies scaled to short-term SCIAMACHY solar irradiance observations to describe decadal irradiance changes. These calculations are compared to existing solar data: the UV data from SUSIM/UARS, from the DeLand & Cebula satellite composite, and the SIP model (S2K+VUV2002); and UV-vis-IR data from the NRLSSI and SATIRE models, and SIM/SORCE measurements. The mean SSI of the latter models show good agreement (less than 5%) in the vis regions over three decades while larger disagreements (10 - 20%) are found in the UV and IR regions. Between minima and maxima of Solar Cycles 21, 22, and 23, the inferred SSI variability from the SCIA proxy is intermediate between SATIRE and NRLSSI in the UV. While the DeLand & Cebula composite provide the highest variability between solar minimum and maximum, the SIP/Solar2000 and NRLSSI models show minimum variability, which may be due to the use of a single proxy in the modeling of the irradiances. In the vis-IR spectral region, the SCIA proxy model reports lower values in the changes from solar maximum to minimum, which may be attributed to overestimations of the sunspot proxy used in modeling the SCIAMACHY irradiances. The fairly short timeseries of SIM/SORCE shows a steeper decreasing (increasing) trend in the UV (vis) than the other data during the descending phase of Solar Cycle 23. Though considered to be only provisional, the opposite trend seen in the visible SIM data challenges the validity of proxy-based linear extrapolation commonly used in reconstructing past irradiances.

The Response of High Energy Photoelectrons in The Mars Atmosphere to Variable Solar Input

NASA Astrophysics Data System (ADS)

Mills, I. F.; Eparvier, F. G.; Thiemann, E.; Mitchell, D. L.

2016-12-01

The Mars Atmosphere and Volatile Evolution (MAVEN) mission aims to understand the processes by which Mars has been losing atmosphere over time by analyzing data taken from different levels of the Martian atmosphere as well as solar drivers. In this project, we isolate data taken from the ionosphere to study high-energy electrons created by a particular ionization process called the Auger effect. This process occurs when soft x-rays ionize atmospheric gases. In particular, we focus on Auger electrons that are ionized from CO2 molecules and atomic O via solar irradiance in the 0.1-6 nm wavelength range. Thus far, the portion of the solar spectrum that produces Auger electrons has been sparsely measured and its spectral distribution is poorly understood, especially as a function of solar activity. To make up for this, models of spectral irradiance are used in studies of atmospheric effects. In an effort to validate solar irradiance models from 0.1- 6 nm, we utilize data from two instruments on board the MAVEN spacecraft, EUVM (the Extreme Ultraviolet Monitor), which measures the broadband solar irradiance from 0.1-6 nm and SWEA (the Solar Wind Electron Analyzer), which measures the photoelectron energy spectrum in the Mars atmosphere. We then compare these observed data sets to two different spectral irradiance models: MAVEN SynRef, and FISM-M (the Flare Irradiance Spectral Model for Mars). SynRef is a version of the SORCE XPS model modified to be used by MAVEN/EUVM, and FISM-M is a version of the FISM proxy model previously developed for Earth irradiance and modified to be used by MAVEN/EUVM. Our method of comparison is to find the Pearson correlation between the data and the models over October 2015, a month that had a strong solar rotational variability in the solar irradiance. By filtering the SWEA data for different altitudes and solar zenith angles, we are able to analyze how Auger electrons react under different solar activity levels. Both irradiance models correlate well with the electron data, specifically when comparing them with electrons in the bin containing the Auger peak, and when integrating over multiple energy bins surrounding this peak.

Changes in atmospheric circulation between solar maximum and minimum conditions in winter and summer

NASA Astrophysics Data System (ADS)

Lee, Jae Nyung

2008-10-01

Statistically significant climate responses to the solar variability are found in Northern Annular Mode (NAM) and in the tropical circulation. This study is based on the statistical analysis of numerical simulations with ModelE version of the chemistry coupled Goddard Institute for Space Studies (GISS) general circulation model (GCM) and National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis. The low frequency large scale variability of the winter and summer circulation is described by the NAM, the leading Empirical Orthogonal Function (EOF) of geopotential heights. The newly defined seasonal annular modes and its dynamical significance in the stratosphere and troposphere in the GISS ModelE is shown and compared with those in the NCEP/NCAR reanalysis. In the stratosphere, the summer NAM obtained from NCEP/NCAR reanalysis as well as from the ModelE simulations has the same sign throughout the northern hemisphere, but shows greater variability at low latitudes. The patterns in both analyses are consistent with the interpretation that low NAM conditions represent an enhancement of the seasonal difference between the summer and the annual averages of geopotential height, temperature and velocity distributions, while the reverse holds for high NAM conditions. Composite analysis of high and low NAM cases in both the model and observation suggests that the summer stratosphere is more "summer-like" when the solar activity is near a maximum. This means that the zonal easterly wind flow is stronger and the temperature is higher than normal. Thus increased irradiance favors a low summer NAM. A quantitative comparison of the anti-correlation between the NAM and the solar forcing is presented in the model and in the observation, both of which show lower/higher NAM index in solar maximum/minimum conditions. The summer NAM in the troposphere obtained from NCEP/NCAR reanalysis has a dipolar zonal structure with maximum variability over the Asian monsoon region. The corresponding EOF in ModelE has a qualitatively similar structure but with less variability in the Asian monsoon region which is displaced eastward of its observed position. In both the NCEP/NCAR reanalysis and the GISS GCM, the negative anomalies associated with the NAM in the Euro-Atlantic and Aleutian island regions are enhanced in the solar minimum conditions, though the results are not statistically significant. The difference of the downward propagation of NAM between solar maximum and solar minimum is shown with the NCEP/NCAR reanalysis. For the winter NAM, a much greater fraction of stratospheric circulation perturbations penetrate to the surface in solar maximum conditions than in minimum conditions. This difference is more striking when the zonal wind direction in the tropics is from the west: when equatorial 50 hPa winds are from the west, no stratospheric signals reach the surface under solar minimum conditions, while over 50 percent reach the surface under solar maximum conditions. This work also studies the response of the tropical circulation to the solar forcing in combination with different atmospheric compositions and with different ocean modules. Four model experiments have been designed to investigate the role of solar forcing in the tropical circulation: one with the present day (PD) greenhouse gases and aerosol conditions, one with the preindustrial (PI) conditions, one with the doubled minimum solar forcing, and finally one with the hybrid-isopycnic ocean model (HYCOM). The response patterns in the tropical humidity and in the vertical motion due to solar forcing are season dependent and spatially heterogeneous. The tropical humidity response from the model experiments are compared with the corresponding differences obtained from the NCEP/NCAR reanalysis with all years and with non-ENSO years. Both the model and the reanalysis consistently show that the specific humidity is significantly greater in the convective region in solar maximum compared to solar minimum for January and July. The column integrated humidity in all the model experiments with different composition, different solar forcing, and different ocean module, increased with solar forcing in the tropical band over the Atlantic sector in both seasons. The model's humidity response pattern is generally consistent with the paleoclimate records indicating increased precipitation near the equator that decreases at subtropical to middle latitudes with increased solar output. The differences in the zonally averaged vertical velocities indicate that the ascending branch of the Hadley cell is enhanced and shifted northward, and that the descending branch is weakened and shifted northward in the solar MAX simulation in January. The downward branch of the Hadley cell is strengthened in MAX in July. A possible link of climate response in midlatitudes to solar forcing is also presented by showing changes in zonal mean wind, changes in temperature gradient, and changes in E-P flux.

Simulation of Solar Energy Use in Livelihood of Buildings

NASA Astrophysics Data System (ADS)

Lvocich, I. Ya; Preobrazhenskiy, A. P.; Choporov, O. N.

2017-11-01

Solar energy can be considered as the most technological and economical type of renewable energy. The purpose of the paper is to increase the efficiency of solar energy utilization on the basis of the mathematical simulation of the solar collector. A mathematical model of the radiant heat transfer vacuum solar collector is clarified. The model was based on the process of radiative heat transfer between glass and copper walls with the defined blackness degrees. A mathematical model of the ether phase transition point is developed. The dependence of the reservoir walls temperature change on the ambient temperature over time is obtained. The results of the paper can be useful for the development of prospective sources using solar energy.

Solar forcing for CMIP6 (v3.2)

NASA Astrophysics Data System (ADS)

Matthes, Katja; Funke, Bernd; Andersson, Monika E.; Barnard, Luke; Beer, Jürg; Charbonneau, Paul; Clilverd, Mark A.; Dudok de Wit, Thierry; Haberreiter, Margit; Hendry, Aaron; Jackman, Charles H.; Kretzschmar, Matthieu; Kruschke, Tim; Kunze, Markus; Langematz, Ulrike; Marsh, Daniel R.; Maycock, Amanda C.; Misios, Stergios; Rodger, Craig J.; Scaife, Adam A.; Seppälä, Annika; Shangguan, Ming; Sinnhuber, Miriam; Tourpali, Kleareti; Usoskin, Ilya; van de Kamp, Max; Verronen, Pekka T.; Versick, Stefan

2017-06-01

This paper describes the recommended solar forcing dataset for CMIP6 and highlights changes with respect to CMIP5. The solar forcing is provided for radiative properties, namely total solar irradiance (TSI), solar spectral irradiance (SSI), and the F10.7 index as well as particle forcing, including geomagnetic indices Ap and Kp, and ionization rates to account for effects of solar protons, electrons, and galactic cosmic rays. This is the first time that a recommendation for solar-driven particle forcing has been provided for a CMIP exercise. The solar forcing datasets are provided at daily and monthly resolution separately for the CMIP6 preindustrial control, historical (1850-2014), and future (2015-2300) simulations. For the preindustrial control simulation, both constant and time-varying solar forcing components are provided, with the latter including variability on 11-year and shorter timescales but no long-term changes. For the future, we provide a realistic scenario of what solar behavior could be, as well as an additional extreme Maunder-minimum-like sensitivity scenario. This paper describes the forcing datasets and also provides detailed recommendations as to their implementation in current climate models.For the historical simulations, the TSI and SSI time series are defined as the average of two solar irradiance models that are adapted to CMIP6 needs: an empirical one (NRLTSI2-NRLSSI2) and a semi-empirical one (SATIRE). A new and lower TSI value is recommended: the contemporary solar-cycle average is now 1361.0 W m-2. The slight negative trend in TSI over the three most recent solar cycles in the CMIP6 dataset leads to only a small global radiative forcing of -0.04 W m-2. In the 200-400 nm wavelength range, which is important for ozone photochemistry, the CMIP6 solar forcing dataset shows a larger solar-cycle variability contribution to TSI than in CMIP5 (50 % compared to 35 %).We compare the climatic effects of the CMIP6 solar forcing dataset to its CMIP5 predecessor by using time-slice experiments of two chemistry-climate models and a reference radiative transfer model. The differences in the long-term mean SSI in the CMIP6 dataset, compared to CMIP5, impact on climatological stratospheric conditions (lower shortwave heating rates of -0.35 K day-1 at the stratopause), cooler stratospheric temperatures (-1.5 K in the upper stratosphere), lower ozone abundances in the lower stratosphere (-3 %), and higher ozone abundances (+1.5 % in the upper stratosphere and lower mesosphere). Between the maximum and minimum phases of the 11-year solar cycle, there is an increase in shortwave heating rates (+0.2 K day-1 at the stratopause), temperatures ( ˜ 1 K at the stratopause), and ozone (+2.5 % in the upper stratosphere) in the tropical upper stratosphere using the CMIP6 forcing dataset. This solar-cycle response is slightly larger, but not statistically significantly different from that for the CMIP5 forcing dataset.CMIP6 models with a well-resolved shortwave radiation scheme are encouraged to prescribe SSI changes and include solar-induced stratospheric ozone variations, in order to better represent solar climate variability compared to models that only prescribe TSI and/or exclude the solar-ozone response. We show that monthly-mean solar-induced ozone variations are implicitly included in the SPARC/CCMI CMIP6 Ozone Database for historical simulations, which is derived from transient chemistry-climate model simulations and has been developed for climate models that do not calculate ozone interactively. CMIP6 models without chemistry that perform a preindustrial control simulation with time-varying solar forcing will need to use a modified version of the SPARC/CCMI Ozone Database that includes solar variability. CMIP6 models with interactive chemistry are also encouraged to use the particle forcing datasets, which will allow the potential long-term effects of particles to be addressed for the first time. The consideration of particle forcing has been shown to significantly improve the representation of reactive nitrogen and ozone variability in the polar middle atmosphere, eventually resulting in further improvements in the representation of solar climate variability in global models.

Solar Plus: A Holistic Approach to Distributed Solar PV

DOE Office of Scientific and Technical Information (OSTI.GOV)

OShaughnessy, Eric J.; Ardani, Kristen B.; Cutler, Dylan S.

Solar 'plus' refers to an emerging approach to distributed solar photovoltaic (PV) deployment that uses energy storage and controllable devices to optimize customer economics. The solar plus approach increases customer system value through technologies such as electric batteries, smart domestic water heaters, smart air-conditioner (AC) units, and electric vehicles We use an NREL optimization model to explore the customer-side economics of solar plus under various utility rate structures and net metering rates. We explore optimal solar plus applications in five case studies with different net metering rates and rate structures. The model deploys different configurations of PV, batteries, smart domesticmore » water heaters, and smart AC units in response to different rate structures and customer load profiles. The results indicate that solar plus improves the customer economics of PV and may mitigate some of the negative impacts of evolving rate structures on PV economics. Solar plus may become an increasingly viable model for optimizing PV customer economics in an evolving rate environment.« less

Operation of the computer model for microenvironment solar exposure

NASA Technical Reports Server (NTRS)

Gillis, J. R.; Bourassa, R. J.; Gruenbaum, P. E.

1995-01-01

A computer model for microenvironmental solar exposure was developed to predict solar exposure to satellite surfaces which may shadow or reflect on one another. This document describes the technical features of the model as well as instructions for the installation and use of the program.

Mathematical and computational modeling simulation of solar drying Systems

USDA-ARS?s Scientific Manuscript database

Mathematical modeling of solar drying systems has the primary aim of predicting the required drying time for a given commodity, dryer type, and environment. Both fundamental (Fickian diffusion) and semi-empirical drying models have been applied to the solar drying of a variety of agricultural commo...

Lagged correlations between the NAO and the 11-year solar cycle: forced response or internal variability?

NASA Astrophysics Data System (ADS)

Oehrlein, J.; Chiodo, G.; Polvani, L. M.; Smith, A. K.

2017-12-01

Recently, the North Atlantic Oscillation has been suggested to respond to the 11-year solar cycle with a lag of a few years. The solar/NAO relationship provides a potential pathway for solar activity to modulate surface climate. However, a short observational record paired with the strong internal variability of the NAO raises questions about the robustness of the claimed solar/NAO relationship. For the first time, we investigate the robustness of the solar/NAO signal in four different reanalysis data sets and long integrations from an ocean-coupled chemistry-climate model forced with the 11-year solar cycle. The signal appears to be robust in the different reanalysis datasets. We also show, for the first time, that many features of the observed signal, such as amplitude, spatial pattern, and lag of 2/3 years, can be accurately reproduced in our model simulations. However, in both the reanalysis and model simulations, we find that this signal is non-stationary. A lagged NAO/solar signal can also be reproduced in two sets of model integrations without the 11-year solar cycle. This suggests that the correlation found in observational data could be the result of internal decadal variability in the NAO and not a response to the solar cycle. This has wide implications towards the interpretation of solar signals in observational data.

A Time-dependent Heliospheric Model Driven by Empirical Boundary Conditions

NASA Astrophysics Data System (ADS)

Kim, T. K.; Arge, C. N.; Pogorelov, N. V.

2017-12-01

Consisting of charged particles originating from the Sun, the solar wind carries the Sun's energy and magnetic field outward through interplanetary space. The solar wind is the predominant source of space weather events, and modeling the solar wind propagation to Earth is a critical component of space weather research. Solar wind models are typically separated into coronal and heliospheric parts to account for the different physical processes and scales characterizing each region. Coronal models are often coupled with heliospheric models to propagate the solar wind out to Earth's orbit and beyond. The Wang-Sheeley-Arge (WSA) model is a semi-empirical coronal model consisting of a potential field source surface model and a current sheet model that takes synoptic magnetograms as input to estimate the magnetic field and solar wind speed at any distance above the coronal region. The current version of the WSA model takes the Air Force Data Assimilative Photospheric Flux Transport (ADAPT) model as input to provide improved time-varying solutions for the ambient solar wind structure. When heliospheric MHD models are coupled with the WSA model, density and temperature at the inner boundary are treated as free parameters that are tuned to optimal values. For example, the WSA-ENLIL model prescribes density and temperature assuming momentum flux and thermal pressure balance across the inner boundary of the ENLIL heliospheric MHD model. We consider an alternative approach of prescribing density and temperature using empirical correlations derived from Ulysses and OMNI data. We use our own modeling software (Multi-scale Fluid-kinetic Simulation Suite) to drive a heliospheric MHD model with ADAPT-WSA input. The modeling results using the two different approaches of density and temperature prescription suggest that the use of empirical correlations may be a more straightforward, consistent method.

Modeling, Simulation, and Control of a Solar Electric Propulsion Vehicle in Near-Earth Vicinity Including Solar Array Degradation

NASA Technical Reports Server (NTRS)

Witzberger, Kevin (Inventor); Hojnicki, Jeffery (Inventor); Manzella, David (Inventor)

2016-01-01

Modeling and control software that integrates the complexities of solar array models, a space environment, and an electric propulsion system into a rigid body vehicle simulation and control model is provided. A rigid body vehicle simulation of a solar electric propulsion (SEP) vehicle may be created using at least one solar array model, at least one model of a space environment, and at least one model of a SEP propulsion system. Power availability and thrust profiles may be determined based on the rigid body vehicle simulation as the SEP vehicle transitions from a low Earth orbit (LEO) to a higher orbit or trajectory. The power availability and thrust profiles may be displayed such that a user can use the displayed power availability and thrust profiles to determine design parameters for an SEP vehicle mission.

Toward Improved Modeling of Spectral Solar Irradiance for Solar Energy Applications: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Yu; Sengupta, Manajit

This study introduces the National Renewable Energy Laboratory's (NREL's) recent efforts to extend the capability of the Fast All-sky Radiation Model for Solar applications (FARMS) by computing spectral solar irradiances over both horizontal and inclined surfaces. A new model is developed by computing the optical thickness of the atmosphere using a spectral irradiance model for clear-sky conditions, SMARTS2. A comprehensive lookup table (LUT) of cloud bidirectional transmittance distribution functions (BTDFs) is precomputed for 2002 wavelength bands using an atmospheric radiative transfer model, libRadtran. The solar radiation transmitted through the atmosphere is given by considering all possible paths of photon transmissionmore » and the relevent scattering and absorption attenuation. Our results indicate that this new model has an accuracy that is similar to that of state-of-the-art radiative transfer models, but it is significantly more efficient.« less

An Improved Radiative Transfer Model for Climate Calculations

NASA Technical Reports Server (NTRS)

Bergstrom, Robert W.; Mlawer, Eli J.; Sokolik, Irina N.; Clough, Shepard A.; Toon, Owen B.

1998-01-01

This paper presents a radiative transfer model that has been developed to accurately predict the atmospheric radiant flux in both the infrared and the solar spectrum with a minimum of computational effort. The model is designed to be included in numerical climate models To assess the accuracy of the model, the results are compared to other more detailed models for several standard cases in the solar and thermal spectrum. As the thermal spectrum has been treated in other publications, we focus here on the solar part of the spectrum. We perform several example calculations focussing on the question of absorption of solar radiation by gases and aerosols.

Object-oriented simulation model of a parabolic trough solar collector: Static and dynamic validation

NASA Astrophysics Data System (ADS)

Ubieta, Eduardo; Hoyo, Itzal del; Valenzuela, Loreto; Lopez-Martín, Rafael; Peña, Víctor de la; López, Susana

2017-06-01

A simulation model of a parabolic-trough solar collector developed in Modelica® language is calibrated and validated. The calibration is performed in order to approximate the behavior of the solar collector model to a real one due to the uncertainty in some of the system parameters, i.e. measured data is used during the calibration process. Afterwards, the validation of this calibrated model is done. During the validation, the results obtained from the model are compared to the ones obtained during real operation in a collector from the Plataforma Solar de Almeria (PSA).

Modelling rotational and cyclical spectral solar irradiance variations

NASA Astrophysics Data System (ADS)

Unruh, Yvonne

Solar irradiance changes are highly wavelength dependent: solar-cycle variations in the UV can be on the order of tens of percent, while changes in the visible are typically only of the order of one or two permille. With the launch of a number of instruments to measure spectral solar irradiance, we are now for a first time in a good position to explore the changing solar irradiance over a large range of wavelengths and to test our irradiance models as well as some of their underlying assumptions. I will introduce some of the current modelling approaches and present model-data comparisons, using the SATIRE irradiance model and SORCE/SIM measurements as an example. I will conclude by highlighting a number of outstanding questions regarding the modelling of spectral irradiance and current approaches to address these.

Relationship between a solar drying model of red pepper and the kinetics of pure water evaporation (1)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Passamai, V.; Saravia, L.

1997-05-01

Drying of red pepper under solar radiation was investigated, and a simple model related to water evaporation was developed. Drying experiments at constant laboratory conditions were undertaken where solar radiation was simulated by a 1,000 W lamp. In this first part of the work, water evaporation under radiation is studied and laboratory experiments are presented with two objectives: to verify Penman`s model of evaporation under radiation, and to validate the laboratory experiments. Modifying Penman`s model of evaporation by introducing two drying conductances as a function of water content, allows the development of a drying model under solar radiation. In themore » second part of this paper, the model is validated by applying it to red pepper open air solar drying experiments.« less

Modelling Solar and Stellar Brightness Variabilities

NASA Astrophysics Data System (ADS)

Yeo, K. L.; Shapiro, A. I.; Krivova, N. A.; Solanki, S. K.

2016-04-01

Total and spectral solar irradiance, TSI and SSI, have been measured from space since 1978. This is accompanied by the development of models aimed at replicating the observed variability by relating it to solar surface magnetism. Despite significant progress, there remains persisting controversy over the secular change and the wavelength-dependence of the variation with impact on our understanding of the Sun's influence on the Earth's climate. We highlight the recent progress in TSI and SSI modelling with SATIRE. Brightness variations have also been observed for Sun-like stars. Their analysis can profit from knowledge of the solar case and provide additional constraints for solar modelling. We discuss the recent effort to extend SATIRE to Sun-like stars.

Reconstructions of solar irradiance on centennial time scales

NASA Astrophysics Data System (ADS)

Krivova, Natalie; Solanki, Sami K.; Dasi Espuig, Maria; Kok Leng, Yeo

Solar irradiance is the main external source of energy to Earth's climate system. The record of direct measurements covering less than 40 years is too short to study solar influence on Earth's climate, which calls for reconstructions of solar irradiance into the past with the help of appropriate models. An obvious requirement to a competitive model is its ability to reproduce observed irradiance changes, and a successful example of such a model is presented by the SATIRE family of models. As most state-of-the-art models, SATIRE assumes that irradiance changes on time scales longer than approximately a day are caused by the evolving distribution of dark and bright magnetic features on the solar surface. The surface coverage by such features as a function of time is derived from solar observations. The choice of these depends on the time scale in question. Most accurate is the version of the model that employs full-disc spatially-resolved solar magnetograms and reproduces over 90% of the measured irradiance variation, including the overall decreasing trend in the total solar irradiance over the last four cycles. Since such magnetograms are only available for about four decades, reconstructions on time scales of centuries have to rely on disc-integrated proxies of solar magnetic activity, such as sunspot areas and numbers. Employing a surface flux transport model and sunspot observations as input, we have being able to produce synthetic magnetograms since 1700. This improves the temporal resolution of the irradiance reconstructions on centennial time scales. The most critical aspect of such reconstructions remains the uncertainty in the magnitude of the secular change.

Comparison of Model and Observations of Middle Atmospheric HOx Response to Solar 27-day Cycles: Quantifying Model Uncertainties due to Photochemistry

NASA Astrophysics Data System (ADS)

Wang, S.; Li, K. F.; Shia, R. L.; Yung, Y. L.; Sander, S. P.

2016-12-01

HO2 and OH (known as odd oxygen HOx), play an important role in middle atmospheric chemistry, in particular, O3 destruction through catalytic HOx reaction cycles. Due to their photochemical production and short chemical lifetimes, HOx species response rapidly to solar UV irradiance changes during solar cycles, resulting in variability in the corresponding O3 chemistry. Observational evidences for both OH and HO2 variability due to solar cycles have been reported. However, puzzling discrepancies remain. In particular, the large discrepancy between model and observations of solar 11-year cycle signal in OH and the significantly different model results when adopting different solar spectral irradiance (SSI) [Wang et al., 2013] suggest that both uncertainties in SSI variability and uncertainties in our current understanding of HOx-O3 chemistry could contribute to the discrepancy. Since the short-term SSI variability (e.g. changes during solar 27-day cycles) has little uncertainty, investigating 27-day solar cycle signals in HOx allows us to simplify the complex problem and to focus on the uncertainties in chemistry alone. We use the Caltech-JPL photochemical model to simulate observed HOx variability during 27-day cycles. The comparison between Aura Microwave Limb Sounder (MLS) observations and our model results (using standard chemistry and "adjusted chemistry", respectively) will be discussed. A better understanding of uncertainties in chemistry will eventually help us separate the contribution of chemistry from contributions of SSI uncertainties to the complex discrepancy between model and observations of OH responses to solar 11-year cycles.

NREL: Renewable Resource Data Center - Solar Resource Models and Tools

Science.gov Websites

Solar Resource Models and Tools The Renewable Resource Data Center (RReDC) features the following -supplied hourly average measured global horizontal data. NSRDB Data Viewer Visualize, explore, and download solar resource data from the National Solar Radiation Database. PVWatts® Calculator PVWattsÂ

A Groundwater Model to Assess Water Resource Impacts at the Brenda Solar Energy Zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quinn, John; Carr, Adrianne E.; Greer, Chris

2013-12-01

The purpose of this study is to develop a groundwater flow model to examine the influence of potential groundwater withdrawal to support utility-scale solar energy development at the Brenda Solar Energy Zone (SEZ), as a part of the Bureau of Land Management’s (BLM’s) Solar Energy Program.

Elementary Students' Mental Models of the Solar System

ERIC Educational Resources Information Center

Calderon-Canales, Elena; Flores-Camacho, Fernando; Gallegos-Cazares, Leticia

2013-01-01

This research project aimed to identify and analyze Mexican primary school students' ideas about the components of the solar system. In particular, this study focused on conceptions of the solar system and representations of the dynamics of the solar system based on the functional and structural models that students make in school. Using a…

Distributed Generation Market Demand Model (dGen): Documentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sigrin, Benjamin; Gleason, Michael; Preus, Robert

The Distributed Generation Market Demand model (dGen) is a geospatially rich, bottom-up, market-penetration model that simulates the potential adoption of distributed energy resources (DERs) for residential, commercial, and industrial entities in the continental United States through 2050. The National Renewable Energy Laboratory (NREL) developed dGen to analyze the key factors that will affect future market demand for distributed solar, wind, storage, and other DER technologies in the United States. The new model builds off, extends, and replaces NREL's SolarDS model (Denholm et al. 2009a), which simulates the market penetration of distributed PV only. Unlike the SolarDS model, dGen can modelmore » various DER technologies under one platform--it currently can simulate the adoption of distributed solar (the dSolar module) and distributed wind (the dWind module) and link with the ReEDS capacity expansion model (Appendix C). The underlying algorithms and datasets in dGen, which improve the representation of customer decision making as well as the spatial resolution of analyses (Figure ES-1), also are improvements over SolarDS.« less

Interplanetary Radiation and Internal Charging Environment Models for Solar Sails

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Altstatt, Richard L.; NeegaardParker, Linda

2005-01-01

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.

Baseline and Target Values for PV Forecasts: Toward Improved Solar Power Forecasting: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jie; Hodge, Bri-Mathias; Lu, Siyuan

2015-08-05

Accurate solar power forecasting allows utilities to get the most out of the solar resources on their systems. To truly measure the improvements that any new solar forecasting methods can provide, it is important to first develop (or determine) baseline and target solar forecasting at different spatial and temporal scales. This paper aims to develop baseline and target values for solar forecasting metrics. These were informed by close collaboration with utility and independent system operator partners. The baseline values are established based on state-of-the-art numerical weather prediction models and persistence models. The target values are determined based on the reductionmore » in the amount of reserves that must be held to accommodate the uncertainty of solar power output. forecasting metrics. These were informed by close collaboration with utility and independent system operator partners. The baseline values are established based on state-of-the-art numerical weather prediction models and persistence models. The target values are determined based on the reduction in the amount of reserves that must be held to accommodate the uncertainty of solar power output.« less

Solar influence on climate during the past millennium: Results from transient simulations with the NCAR Climate System Model

PubMed Central

Ammann, Caspar M.; Joos, Fortunat; Schimel, David S.; Otto-Bliesner, Bette L.; Tomas, Robert A.

2007-01-01

The potential role of solar variations in modulating recent climate has been debated for many decades and recent papers suggest that solar forcing may be less than previously believed. Because solar variability before the satellite period must be scaled from proxy data, large uncertainty exists about phase and magnitude of the forcing. We used a coupled climate system model to determine whether proxy-based irradiance series are capable of inducing climatic variations that resemble variations found in climate reconstructions, and if part of the previously estimated large range of past solar irradiance changes could be excluded. Transient simulations, covering the published range of solar irradiance estimates, were integrated from 850 AD to the present. Solar forcing as well as volcanic and anthropogenic forcing are detectable in the model results despite internal variability. The resulting climates are generally consistent with temperature reconstructions. Smaller, rather than larger, long-term trends in solar irradiance appear more plausible and produced modeled climates in better agreement with the range of Northern Hemisphere temperature proxy records both with respect to phase and magnitude. Despite the direct response of the model to solar forcing, even large solar irradiance change combined with realistic volcanic forcing over past centuries could not explain the late 20th century warming without inclusion of greenhouse gas forcing. Although solar and volcanic effects appear to dominate most of the slow climate variations within the past thousand years, the impacts of greenhouse gases have dominated since the second half of the last century. PMID:17360418

JEDI Concentrating Solar Power Model | Jobs and Economic Development Impact

Science.gov Websites

Economic Development Impacts (JEDI) Concentrating Solar Power Model allows users to estimate economic development impacts from concentrating solar power projects and includes default information that can be

Characterizing a Model of Coronal Heating and Solar Wind Acceleration Based on Wave Turbulence.

NASA Astrophysics Data System (ADS)

Downs, C.; Lionello, R.; Mikic, Z.; Linker, J.; Velli, M.

2014-12-01

Understanding the nature of coronal heating and solar wind acceleration is a key goal in solar and heliospheric research. While there have been many theoretical advances in both topics, including suggestions that they may be intimately related, the inherent scale coupling and complexity of these phenomena limits our ability to construct models that test them on a fundamental level for realistic solar conditions. At the same time, there is an ever increasing impetus to improve our spaceweather models, and incorporating treatments for these processes that capture their basic features while remaining tractable is an important goal. With this in mind, I will give an overview of our exploration of a wave-turbulence driven (WTD) model for coronal heating and solar wind acceleration based on low-frequency Alfvénic turbulence. Here we attempt to bridge the gap between theory and practical modeling by exploring this model in 1D HD and multi-dimensional MHD contexts. The key questions that we explore are: What properties must the model possess to be a viable model for coronal heating? What is the influence of the magnetic field topology (open, closed, rapidly expanding)? And can we simultaneously capture coronal heating and solar wind acceleration with such a quasi-steady formulation? Our initial results suggest that a WTD based formulation performs adequately for a variety of solar and heliospheric conditions, while significantly reducing the number of free parameters when compared to empirical heating and solar wind models. The challenges, applications, and future prospects of this type of approach will also be discussed.

Economic and Environmental Consequences of Widespread Expansion of Solar energy

NASA Astrophysics Data System (ADS)

Satija, Gaurav

The purpose of the thesis is to examine the sustainability of an expansion in solar energy subject to resource constraints of Indium. Coal and natural gas are taken as competitors for solar in the energy market. The consumer electronics market also competes with solar PV production because of Indium's use in the manufacturing of LCD screens. A partial equilibrium model is made which determines the rate of extraction of indium, coal and natural gas endogenously. Consumer demand is modeled by the use of cost shares. Generation of electricity and production of LCDs are modeled using Constant Elasticity of Substitution functions. Initial production capacity for both electricity and LCD is considered in the model. The model then endogenously determines the level of investment required. Model simulations are performed to predict the extraction paths and production levels for a timeline of 100 years. A sensitivity analysis is performed to see the reaction of the model to changes in consumer demand and learning rates in solar energy. The response of the model to imposition of various emission caps is also shown. Results of the model show that indium scarcity prevents solar from expanding significantly to a level where it can take over from non-renewable sources of energy. Increased research in solar technologies would not be of much help unless more Indium is available, either by recycling of solar PVs and LCDs or searching for alternate technologies to manufacture LCD screes. Emission caps are able to control excessive usage of fossil fuels and preserve them for a longer time.

Inversions of the Ledoux discriminant: a closer look at the tachocline

NASA Astrophysics Data System (ADS)

Buldgen, Gaël; Salmon, S. J. A. J.; Godart, M.; Noels, A.; Scuflaire, R.; Dupret, M. A.; Reese, D. R.; Colgan, J.; Fontes, C. J.; Eggenberger, P.; Hakel, P.; Kilcrease, D. P.; Richard, O.

2017-11-01

Modelling the base of the solar convective envelope is a tedious problem. Since the first rotation inversions, solar modellers are confronted with the fact that a region of very limited extent has an enormous physical impact on the Sun. Indeed, it is the transition region from differential to solid body rotation, the tachocline, which furthermore is influenced by turbulence and is also supposed to be the seat of the solar magnetic dynamo. Moreover, solar models show significant disagreement with the sound-speed profile in this region. In this Letter, we show how helioseismology can provide further constraints on this region by carrying out an inversion of the Ledoux discriminant. We compare these inversions for standard solar sodels built using various opacity tables and chemical abundances and discuss the origins of the discrepancies between solar models and the Sun.

Probing the solar core with low-degree p modes

NASA Astrophysics Data System (ADS)

Roxburgh, I. W.; Vorontsov, S. V.

2002-01-01

We address the question of what could be learned about the solar core structure if the seismic data were limited to low-degree modes only. The results of three different experiments are described. The first is the linearized structural inversion of the p-mode frequencies of a solar model modified slightly in the energy-generating core, using the original (unmodified) model as an initial guess. In the second experiment, we invert the solar p-mode frequencies measured in the 32-month subset of BiSON data (Chaplin et al. 1998), degraded with additional 0.1 μHz random errors, using a model of 2.6 Gyr age from the solar evolutionary sequence as an initial approximation. This second inversion is non-linear. In the third experiment, we compare the same set of BiSON frequencies with current reference solar model.

An Update of the Analytical Groundwater Modeling to Assess Water Resource Impacts at the Afton Solar Energy Zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quinn, John J.; Greer, Christopher B.; Carr, Adrianne E.

2014-10-01

The purpose of this study is to update a one-dimensional analytical groundwater flow model to examine the influence of potential groundwater withdrawal in support of utility-scale solar energy development at the Afton Solar Energy Zone (SEZ) as a part of the Bureau of Land Management’s (BLM’s) Solar Energy Program. This report describes the modeling for assessing the drawdown associated with SEZ groundwater pumping rates for a 20-year duration considering three categories of water demand (high, medium, and low) based on technology-specific considerations. The 2012 modeling effort published in the Final Programmatic Environmental Impact Statement for Solar Energy Development in Sixmore » Southwestern States (Solar PEIS; BLM and DOE 2012) has been refined based on additional information described below in an expanded hydrogeologic discussion.« less

Deep Learning Based Solar Flare Forecasting Model. I. Results for Line-of-sight Magnetograms

NASA Astrophysics Data System (ADS)

Huang, Xin; Wang, Huaning; Xu, Long; Liu, Jinfu; Li, Rong; Dai, Xinghua

2018-03-01

Solar flares originate from the release of the energy stored in the magnetic field of solar active regions, the triggering mechanism for these flares, however, remains unknown. For this reason, the conventional solar flare forecast is essentially based on the statistic relationship between solar flares and measures extracted from observational data. In the current work, the deep learning method is applied to set up the solar flare forecasting model, in which forecasting patterns can be learned from line-of-sight magnetograms of solar active regions. In order to obtain a large amount of observational data to train the forecasting model and test its performance, a data set is created from line-of-sight magnetogarms of active regions observed by SOHO/MDI and SDO/HMI from 1996 April to 2015 October and corresponding soft X-ray solar flares observed by GOES. The testing results of the forecasting model indicate that (1) the forecasting patterns can be automatically reached with the MDI data and they can also be applied to the HMI data; furthermore, these forecasting patterns are robust to the noise in the observational data; (2) the performance of the deep learning forecasting model is not sensitive to the given forecasting periods (6, 12, 24, or 48 hr); (3) the performance of the proposed forecasting model is comparable to that of the state-of-the-art flare forecasting models, even if the duration of the total magnetograms continuously spans 19.5 years. Case analyses demonstrate that the deep learning based solar flare forecasting model pays attention to areas with the magnetic polarity-inversion line or the strong magnetic field in magnetograms of active regions.

Reconstruction of total and spectral solar irradiance from 1974 to 2013 based on KPVT, SoHO/MDI, and SDO/HMI observations

NASA Astrophysics Data System (ADS)

Yeo, K. L.; Krivova, N. A.; Solanki, S. K.; Glassmeier, K. H.

2014-10-01

Context. Total and spectral solar irradiance are key parameters in the assessment of solar influence on changes in the Earth's climate. Aims: We present a reconstruction of daily solar irradiance obtained using the SATIRE-S model spanning 1974 to 2013 based on full-disc observations from the KPVT, SoHO/MDI, and SDO/HMI. Methods: SATIRE-S ascribes variation in solar irradiance on timescales greater than a day to photospheric magnetism. The solar spectrum is reconstructed from the apparent surface coverage of bright magnetic features and sunspots in the daily data using the modelled intensity spectra of these magnetic structures. We cross-calibrated the various data sets, harmonizing the model input so as to yield a single consistent time series as the output. Results: The model replicates 92% (R2 = 0.916) of the variability in the PMOD TSI composite including the secular decline between the 1996 and 2008 solar cycle minima. The model also reproduces most of the variability in observed Lyman-α irradiance and the Mg II index. The ultraviolet solar irradiance measurements from the UARS and SORCE missions are mutually consistent up to about 180 nm before they start to exhibit discrepant rotational and cyclical variability, indicative of unresolved instrumental effects. As a result, the agreement between model and measurement, while relatively good below 180 nm, starts to deteriorate above this wavelength. As with earlier similar investigations, the reconstruction cannot reproduce the overall trends in SORCE/SIM SSI. We argue, from the lack of clear solar cycle modulation in the SIM record and the inconsistency between the total flux recorded by the instrument and TSI, that unaccounted instrumental trends are present. Conclusions: The daily solar irradiance time series is consistent with observations from multiple sources, demonstrating its validity and utility for climate models. It also provides further evidence that photospheric magnetism is the prime driver of variation in solar irradiance on timescales greater than a day.

Model studies of the solar limb shape variation with wavelenght within the PICARD project.

NASA Astrophysics Data System (ADS)

Melo, Stella M. L.; Thuillier, Gerard; Claudel, Jennyfer; Haberreiter, Margit; Mein, Nicole; Schmutz, Werner; Shapiro, Alexander; Sofia, Sabatino; Short, Christopher I.

Solar images in the visible wavelength range show that the disk centre is brighter than the limb region. This phenomenon, which is both known as "centre to limb variation (CLV)", or "limb darkening function", is know to depend on wavelength. Since the CLV is determined by the density and temperature stratification, as well as the chemical composition of the so-lar photosphere, its measurement is important to validate theoretical assumption made when building numerical models of the solar atmosphere. The definition of the solar diameter is nor-mally adopted as the separation between two inflection points at opposite ends of a line passing through the center of the solar disk. Therefore, in order to understand long term variability on the solar diameter, it is important to understand what drives the dependence of the position of the inflection point on wavelength. In this paper we use different available solar atmosphere models to study this dependence. The results presented here refer to quiet Sun conditions and encompass the visible and near infra-red spectral regions, which are the regions of interest for the PICARD Satellite Mission. In a first step we utilize the solar atmosphere parameters with a radiative transfer code. This allows for the study of the impact of different factors such as opacities, electron density and temperature from different models on the results. Then, we compare results obtained using each solar atmosphere model. Our results are compared with existent ground based measurements performed by the Pic du Midi telescope, the balloon board measurements with the Solar Disk Sextant experiment, and with the measurements by the Michelson Doppler Imager on board SoHO satellite. The model simulations show that the position of the inflection point is sensitive to the different parameters and model assumptions. Furthermore, our study shows, for the first time, that the position of the inflection point changes dramatically with and outside of Fraunhofer lines.

Magnetohydrodynamic modelling of solar disturbances in the interplanetary medium

NASA Astrophysics Data System (ADS)

Dryer, M.

1985-12-01

A scientifically constructed series of interplanetary magnetohydrodynamic models is made that comprise the foundations for a composite solar terrestrial environment model. These models, unique in the field of solar wind physics, include both 2-1/2D as well as 3D time dependent codes that will lead to future operational status. We have also developed a geomagnetic storm forecasting strategy, referred to as the Solar Terrestrial Environment Model (STEM/2000), whereby these models would be appended in modular fashion to solar, magnetosphere, ionosphere, thermosphere, and neutral atmosphere models. We stress that these models, while still not appropriate at this date for operational use, outline a strategy or blueprint for the future. This strategy, if implemented in its essential features, offers a high probability for technology transfer from theory to operational testing within, approximately, a decade. It would ensure that real time observations would be used to drive physically based models that outputs of which would be used by space environment forecasters.

A numerical calculation of outward propagation of solar disturbances. [solar atmospheric model with shock wave propagation

NASA Technical Reports Server (NTRS)

Wu, S. T.

1974-01-01

The responses of the solar atmosphere due to an outward propagation shock are examined by employing the Lax-Wendroff method to solve the set of nonlinear partial differential equations in the model of the solar atmosphere. It is found that this theoretical model can be used to explain the solar phenomena of surge and spray. A criterion to discriminate the surge and spray is established and detailed information concerning the density, velocity, and temperature distribution with respect to the height and time is presented. The complete computer program is also included.

Evaluation of the National Solar Radiation Database (NSRDB) Using Ground-Based Measurements

NASA Astrophysics Data System (ADS)

Xie, Y.; Sengupta, M.; Habte, A.; Lopez, A.

2017-12-01

Solar resource is essential for a wide spectrum of applications including renewable energy, climate studies, and solar forecasting. Solar resource information can be obtained from ground-based measurement stations and/or from modeled data sets. While measurements provide data for the development and validation of solar resource models and other applications modeled data expands the ability to address the needs for increased accuracy and spatial and temporal resolution. The National Renewable Energy Laboratory (NREL) has developed and regular updates modeled solar resource through the National Solar Radiation Database (NSRDB). The recent NSRDB dataset was developed using the physics-based Physical Solar Model (PSM) and provides gridded solar irradiance (global horizontal irradiance (GHI), direct normal irradiance (DNI), and diffuse horizontal irradiance) at a 4-km by 4-km spatial and half-hourly temporal resolution covering 18 years from 1998-2015. A comprehensive validation of the performance of the NSRDB (1998-2015) was conducted to quantify the accuracy of the spatial and temporal variability of the solar radiation data. Further, the study assessed the ability of NSRDB (1998-2015) to accurately capture inter-annual variability, which is essential information for solar energy conversion projects and grid integration studies. Comparisons of the NSRDB (1998-2015) with nine selected ground-measured data were conducted under both clear- and cloudy-sky conditions. These locations provide a high quality data covering a variety of geographical locations and climates. The comparison of the NSRDB to the ground-based data demonstrated that biases were within +/- 5% for GHI and +/-10% for DNI. A comprehensive uncertainty estimation methodology was established to analyze the performance of the gridded NSRDB and includes all sources of uncertainty at various time-averaged periods, a method that is not often used in model evaluation. Further, the study analyzed the inter-annual and mean-anomaly of the 18 years of solar radiation data. This presentation will outline the validation methodology and provide detailed results of the comparison.

Solar Field Optical Characterization at Stillwater Geothermal/Solar Hybrid Plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Guangdong; Turchi, Craig

Concentrating solar power (CSP) can provide additional thermal energy to boost geothermal plant power generation. For a newly constructed solar field at a geothermal power plant site, it is critical to properly characterize its performance so that the prediction of thermal power generation can be derived to develop an optimum operating strategy for a hybrid system. In the past, laboratory characterization of a solar collector has often extended into the solar field performance model and has been used to predict the actual solar field performance, disregarding realistic impacting factors. In this work, an extensive measurement on mirror slope error andmore » receiver position error has been performed in the field by using the optical characterization tool called Distant Observer (DO). Combining a solar reflectance sampling procedure, a newly developed solar characterization program called FirstOPTIC and public software for annual performance modeling called System Advisor Model (SAM), a comprehensive solar field optical characterization has been conducted, thus allowing for an informed prediction of solar field annual performance. The paper illustrates this detailed solar field optical characterization procedure and demonstrates how the results help to quantify an appropriate tracking-correction strategy to improve solar field performance. In particular, it is found that an appropriate tracking-offset algorithm can improve the solar field performance by about 15%. The work here provides a valuable reference for the growing CSP industry.« less

Solar Field Optical Characterization at Stillwater Geothermal/Solar Hybrid Plant

DOE PAGES

Zhu, Guangdong; Turchi, Craig

2017-01-27

Concentrating solar power (CSP) can provide additional thermal energy to boost geothermal plant power generation. For a newly constructed solar field at a geothermal power plant site, it is critical to properly characterize its performance so that the prediction of thermal power generation can be derived to develop an optimum operating strategy for a hybrid system. In the past, laboratory characterization of a solar collector has often extended into the solar field performance model and has been used to predict the actual solar field performance, disregarding realistic impacting factors. In this work, an extensive measurement on mirror slope error andmore » receiver position error has been performed in the field by using the optical characterization tool called Distant Observer (DO). Combining a solar reflectance sampling procedure, a newly developed solar characterization program called FirstOPTIC and public software for annual performance modeling called System Advisor Model (SAM), a comprehensive solar field optical characterization has been conducted, thus allowing for an informed prediction of solar field annual performance. The paper illustrates this detailed solar field optical characterization procedure and demonstrates how the results help to quantify an appropriate tracking-correction strategy to improve solar field performance. In particular, it is found that an appropriate tracking-offset algorithm can improve the solar field performance by about 15%. The work here provides a valuable reference for the growing CSP industry.« less

Space Environment Effects: Model for Emission of Solar Protons (ESP): Cumulative and Worst Case Event Fluences

NASA Technical Reports Server (NTRS)

Xapsos, M. A.; Barth, J. L.; Stassinopoulos, E. G.; Burke, E. A.; Gee, G. B.

1999-01-01

The effects that solar proton events have on microelectronics and solar arrays are important considerations for spacecraft in geostationary and polar orbits and for interplanetary missions. Designers of spacecraft and mission planners are required to assess the performance of microelectronic systems under a variety of conditions. A number of useful approaches exist for predicting information about solar proton event fluences and, to a lesser extent, peak fluxes. This includes the cumulative fluence over the course of a mission, the fluence of a worst-case event during a mission, the frequency distribution of event fluences, and the frequency distribution of large peak fluxes. Naval Research Laboratory (NRL) and NASA Goddard Space Flight Center, under the sponsorship of NASA's Space Environments and Effects (SEE) Program, have developed a new model for predicting cumulative solar proton fluences and worst-case solar proton events as functions of mission duration and user confidence level. This model is called the Emission of Solar Protons (ESP) model.

Space Environment Effects: Model for Emission of Solar Protons (ESP)--Cumulative and Worst-Case Event Fluences

NASA Technical Reports Server (NTRS)

Xapsos, M. A.; Barth, J. L.; Stassinopoulos, E. G.; Burke, Edward A.; Gee, G. B.

1999-01-01

The effects that solar proton events have on microelectronics and solar arrays are important considerations for spacecraft in geostationary and polar orbits and for interplanetary missions. Designers of spacecraft and mission planners are required to assess the performance of microelectronic systems under a variety of conditions. A number of useful approaches exist for predicting information about solar proton event fluences and, to a lesser extent, peak fluxes. This includes the cumulative fluence over the course of a mission, the fluence of a worst-case event during a mission, the frequency distribution of event fluences, and the frequency distribution of large peak fluxes. Naval Research Laboratory (NRL) and NASA Goddard Space Flight Center, under the sponsorship of NASA's Space Environments and Effects (SEE) Program, have developed a new model for predicting cumulative solar proton fluences and worst-case solar proton events as functions of mission duration and user confidence level. This model is called the Emission of Solar Protons (ESP) model.

Measurements and Modeling of Total Solar Irradiance in X-class Solar Flares

NASA Technical Reports Server (NTRS)

Moore, Christopher S.; Chamberlin, Phillip Clyde; Hock, Rachel

2014-01-01

The Total Irradiance Monitor (TIM) from NASA's SOlar Radiation and Climate Experiment can detect changes in the total solar irradiance (TSI) to a precision of 2 ppm, allowing observations of variations due to the largest X-class solar flares for the first time. Presented here is a robust algorithm for determining the radiative output in the TIM TSI measurements, in both the impulsive and gradual phases, for the four solar flares presented in Woods et al., as well as an additional flare measured on 2006 December 6. The radiative outputs for both phases of these five flares are then compared to the vacuum ultraviolet (VUV) irradiance output from the Flare Irradiance Spectral Model (FISM) in order to derive an empirical relationship between the FISM VUV model and the TIM TSI data output to estimate the TSI radiative output for eight other X-class flares. This model provides the basis for the bolometric energy estimates for the solar flares analyzed in the Emslie et al. study.

Solar related waves in the Venusian atmosphere from the cloud tops to 100 km

NASA Technical Reports Server (NTRS)

Elson, L. S.

1983-01-01

A quasi-linear diagnostic model using observed solar-related temperatures and a specified solar mean circulation and surface structure to find the solar-related circulation above the clouds of Venus is presented. Despite the greater dependence of model-derived, solar-related circulation on the mean flow than is the case for terrestrial tides, as well as the uncertainty concerning this mean flow, significant conclusions are drawn for the solar-related circulation and thermal structure of Venus. An anomalously large response is found in the polar regions, due to the model's requirement of a process such as dissipation which will act as a major sink for momentum. Dissipation is specified in the model as Rayleigh friction with an unknown free parameter coefficient. In view of this, dissipation is either very efficient by terrestrial standards and accompanied by small solar-related circulation, or similar to that of earth and possessed of a circulation large enough to have an impact on the mean circulation.

Solar maximum mission: Ground support programs at the Harvard Radio Astronomy Station

NASA Technical Reports Server (NTRS)

Maxwell, A.

1983-01-01

Observations of the spectral characteristics of solar radio bursts were made with new dynamic spectrum analyzers of high sensitivity and high reliability, over the frequency range 25-580 MHz. The observations also covered the maximum period of the current solar cycle and the period of international cooperative programs designated as the Solar Maximum Year. Radio data on shock waves generated by solar flares were combined with optical data on coronal transients, taken with equipment on the SMM and other satellites, and then incorporated into computer models for the outward passage of fast-mode MHD shocks through the solar corona. The MHD models are non-linear, time-dependent and for the most recent models, quasi-three-dimensional. They examine the global response of the corona for different types of input pulses (thermal, magnetic, etc.) and for different magnetic topologies (for example, open and closed fields). Data on coronal shocks and high-velocity material ejected from solar flares have been interpreted in terms of a model consisting of three main velocity regimes.

Solar Corona/Wind Composition and Origins of the Solar Wind

NASA Astrophysics Data System (ADS)

Lepri, S. T.; Gilbert, J. A.; Landi, E.; Shearer, P.; von Steiger, R.; Zurbuchen, T.

2014-12-01

Measurements from ACE and Ulysses have revealed a multifaceted solar wind, with distinctly different kinetic and compositional properties dependent on the source region of the wind. One of the major outstanding issues in heliophysics concerns the origin and also predictability of quasi-stationary slow solar wind. While the fast solar wind is now proven to originate within large polar coronal holes, the source of the slow solar wind remains particularly elusive and has been the subject of long debate, leading to models that are stationary and also reconnection based - such as interchange or so-called S-web based models. Our talk will focus on observational constraints of solar wind sources and their evolution during the solar cycle. In particular, we will point out long-term variations of wind composition and dynamic properties, particularly focused on the abundance of elements with low First Ionization Potential (FIP), which have been routinely measured on both ACE and Ulysses spacecraft. We will use these in situ observations, and remote sensing data where available, to provide constraints for solar wind origin during the solar cycle, and on their correspondence to predictions for models of the solar wind.

Model for Solar Proton Risk Assessment

NASA Technical Reports Server (NTRS)

Xapos, M. A.; Stauffer, C.; Gee, G. B.; Barth, J. L.; Stassinopoulos, E. G.; McGuire, R. E.

2004-01-01

A statistical model for cumulative solar proton event fluences during space missions is presented that covers both the solar minimum and solar maximum phases of the solar cycle. It is based on data from the IMP and GOES series of satellites that is integrated together to allow the best features of each data set to be taken advantage of. This allows fluence-energy spectra to be extended out to energies of 327 MeV.

Time Exceedances for High Intensity Solar Proton Fluxes

NASA Technical Reports Server (NTRS)

Xapsos, Michael A.; Stauffer, Craig A.; Jordan, Thomas M.; Adam, James H., Jr.; Dietrich, William F.

2011-01-01

A model is presented for times during a space mission that specified solar proton flux levels are exceeded. This includes both total time and continuous time periods during missions. Results for the solar maximum and solar minimum phases of the solar cycle are presented and compared for a broad range of proton energies and shielding levels. This type of approach is more amenable to reliability analysis for spacecraft systems and instrumentation than standard statistical models.

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, Kwang S.; Kim, K. H.; Stock, L. V.

1986-01-01

In order to evaluate the feasibility of the solar pumped dye laser, the parametric study of a dye laser amplifier pumped by a solar simulator and flashlamp was carried out, and the amplifier gains were measured at various pump beam irradiances on the dye cell. Rhodamine 6G was considered as a candidate for the solar pumped laser because of its good utilization of the solar spectrum and high quantum efficiency. The measurement shows that a solar concentration of 20,000 is required to reach the threshold of the dye. The work to construct a kinetic model algorithm which predicts the output parameter of laser was progressed. The kinetic model was improved such that there is good agreement between the theoretical model and experimental data for the systems defined previously as flashlamp pumped laser oscillator, and the long path length solar pumped laser.

Comparing WSA coronal and solar wind model predictions driven by line-of-sight and vector HMI ADAPT maps

NASA Astrophysics Data System (ADS)

Arge, C. N.; Henney, C. J.; Shurkin, K.; Wallace, S.

2017-12-01

As the primary input to nearly all coronal models, reliable estimates of the global solar photospheric magnetic field distribution are critical for accurate modeling and understanding of solar and heliospheric magnetic fields. The Air Force Data Assimilative Photospheric flux Transport (ADAPT) model generates synchronic (i.e., globally instantaneous) maps by evolving observed solar magnetic flux using relatively well understood transport processes when measurements are not available and then updating modeled flux with new observations (available from both the Earth and the far-side of the Sun) using data assimilation methods that rigorously take into account model and observational uncertainties. ADAPT is capable of assimilating line-of-sight and vector magnetic field data from all observatory sources including the expected photospheric vector magnetograms from the Polarimetric and Helioseismic Imager (PHI) on the Solar Orbiter, as well as those generated using helioseismic methods. This paper compares Wang-Sheeley-Arge (WSA) coronal and solar wind modeling results at Earth and STEREO A & B using ADAPT input model maps derived from both line-of-site and vector SDO/HMI magnetograms that include methods for incorporating observations of a large, newly emerged (July 2010) far-side active region (AR11087).

Simulations and Characteristics of Large Solar Events Propagating Throughout the Heliosphere and Beyond (Invited)

NASA Astrophysics Data System (ADS)

Intriligator, D. S.; Sun, W.; Detman, T. R.; Dryer, Ph D., M.; Intriligator, J.; Deehr, C. S.; Webber, W. R.; Gloeckler, G.; Miller, W. D.

2015-12-01

Large solar events can have severe adverse global impacts at Earth. These solar events also can propagate throughout the heliopshere and into the interstellar medium. We focus on the July 2012 and Halloween 2003 solar events. We simulate these events starting from the vicinity of the Sun at 2.5 Rs. We compare our three dimensional (3D) time-dependent simulations to available spacecraft (s/c) observations at 1 AU and beyond. Based on the comparisons of the predictions from our simulations with in-situ measurements we find that the effects of these large solar events can be observed in the outer heliosphere, the heliosheath, and even into the interstellar medium. We use two simulation models. The HAFSS (HAF Source Surface) model is a kinematic model. HHMS-PI (Hybrid Heliospheric Modeling System with Pickup protons) is a numerical magnetohydrodynamic solar wind (SW) simulation model. Both HHMS-PI and HAFSS are ideally suited for these analyses since starting at 2.5 Rs from the Sun they model the slowly evolving background SW and the impulsive, time-dependent events associated with solar activity. Our models naturally reproduce dynamic 3D spatially asymmetric effects observed throughout the heliosphere. Pre-existing SW background conditions have a strong influence on the propagation of shock waves from solar events. Time-dependence is a crucial aspect of interpreting s/c data. We show comparisons of our simulation results with STEREO A, ACE, Ulysses, and Voyager s/c observations.

A new method to estimate average hourly global solar radiation on the horizontal surface

NASA Astrophysics Data System (ADS)

Pandey, Pramod K.; Soupir, Michelle L.

2012-10-01

A new model, Global Solar Radiation on Horizontal Surface (GSRHS), was developed to estimate the average hourly global solar radiation on the horizontal surfaces (Gh). The GSRHS model uses the transmission function (Tf,ij), which was developed to control hourly global solar radiation, for predicting solar radiation. The inputs of the model were: hour of day, day (Julian) of year, optimized parameter values, solar constant (H0), latitude, and longitude of the location of interest. The parameter values used in the model were optimized at a location (Albuquerque, NM), and these values were applied into the model for predicting average hourly global solar radiations at four different locations (Austin, TX; El Paso, TX; Desert Rock, NV; Seattle, WA) of the United States. The model performance was assessed using correlation coefficient (r), Mean Absolute Bias Error (MABE), Root Mean Square Error (RMSE), and coefficient of determinations (R2). The sensitivities of parameter to prediction were estimated. Results show that the model performed very well. The correlation coefficients (r) range from 0.96 to 0.99, while coefficients of determination (R2) range from 0.92 to 0.98. For daily and monthly prediction, error percentages (i.e. MABE and RMSE) were less than 20%. The approach we proposed here can be potentially useful for predicting average hourly global solar radiation on the horizontal surface for different locations, with the use of readily available data (i.e. latitude and longitude of the location) as inputs.

A Groundwater Model to Assess Water Resource Impacts at the Imperial East Solar Energy Zone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quinn, John; Greer, Chris; O'Connor, Ben L.

2013-12-01

The purpose of this study is to develop a groundwater flow model to examine the influence of potential groundwater withdrawal to support the utility-scale solar energy development at the Imperial East Solar Energy Zone (SEZ) as a part of the Bureau of Land Management’s (BLM) solar energy program.

A New Revision of the Solar Irradiance Climate Data Record Incorporates Recent Research into Proxies of Sunspot Darkening and the Sunspot Number Record

NASA Astrophysics Data System (ADS)

Coddington, O.; Lean, J.; Pilewskie, P.; Baranyi, T.; Snow, M. A.; Kopp, G.; Richard, E. C.; Lindholm, C.

2017-12-01

An operational climate data record (CDR) of total and spectral solar irradiance became available in November 2015 as part of the National Oceanographic and Atmospheric Administration's National Centers for Environmental Information Climate Data Record Program. The data record, which is updated quarterly, is available from 1610 to the present as yearly-average values and from 1882 to the present as monthly- and daily-averages, with associated time and wavelength-dependent uncertainties. It was developed jointly by the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics and the Naval Research Laboratory, and, together with the source code and supporting documentation, is available at https://www.ncdc.noaa.gov/cdr/. In the Solar Irradiance CDR, total solar irradiance (TSI) and solar spectral irradiance (SSI) are estimated from models that determine the changes from quiet Sun conditions arising from bright faculae and dark sunspots on the solar disk. The models are constructed using linear regression of proxies of solar sunspot and facular features with the approximately decade-long irradiance observations from the SOlar Radiation and Climate Experiment. A new revision of this data record was recently released in an ongoing effort to reduce solar irradiance uncertainties in two ways. First, the sunspot darkening proxy was revised using a new cross calibration of the current sunspot region observations made by the Solar Observing Optical Network with the historical records of the Royal Greenwich Observatory. This implementation affects modeled irradiances from 1882 - 1978. Second, the impact of a revised record of sunspot number by the Sunspot Index and Long-term Solar Observations center on modeled irradiances was assessed. This implementation provides two different reconstructions of historical, yearly-averaged irradiances from 1610-1881. Additionally, we show new, preliminary results that demonstrate improvements in modeled TSI by using Debrecen Photoheliographic sunspot area and location data produced by the Debrecen Heliophysical Observatory as the proxy of sunspot darkening. Our results describe comparisons of the modeled TSI and SSI with observational records and with other solar irradiance models.

Solar EUV irradiance for space weather applications

NASA Astrophysics Data System (ADS)

Viereck, R. A.

2015-12-01

Solar EUV irradiance is an important driver of space weather models. Large changes in EUV and x-ray irradiances create large variability in the ionosphere and thermosphere. Proxies such as the F10.7 cm radio flux, have provided reasonable estimates of the EUV flux but as the space weather models become more accurate and the demands of the customers become more stringent, proxies are no longer adequate. Furthermore, proxies are often provided only on a daily basis and shorter time scales are becoming important. Also, there is a growing need for multi-day forecasts of solar EUV irradiance to drive space weather forecast models. In this presentation we will describe the needs and requirements for solar EUV irradiance information from the space weather modeler's perspective. We will then translate these requirements into solar observational requirements such as spectral resolution and irradiance accuracy. We will also describe the activities at NOAA to provide long-term solar EUV irradiance observations and derived products that are needed for real-time space weather modeling.

Temperature based daily incoming solar radiation modeling based on gene expression programming, neuro-fuzzy and neural network computing techniques.

NASA Astrophysics Data System (ADS)

Landeras, G.; López, J. J.; Kisi, O.; Shiri, J.

2012-04-01

The correct observation/estimation of surface incoming solar radiation (RS) is very important for many agricultural, meteorological and hydrological related applications. While most weather stations are provided with sensors for air temperature detection, the presence of sensors necessary for the detection of solar radiation is not so habitual and the data quality provided by them is sometimes poor. In these cases it is necessary to estimate this variable. Temperature based modeling procedures are reported in this study for estimating daily incoming solar radiation by using Gene Expression Programming (GEP) for the first time, and other artificial intelligence models such as Artificial Neural Networks (ANNs), and Adaptive Neuro-Fuzzy Inference System (ANFIS). Traditional temperature based solar radiation equations were also included in this study and compared with artificial intelligence based approaches. Root mean square error (RMSE), mean absolute error (MAE) RMSE-based skill score (SSRMSE), MAE-based skill score (SSMAE) and r2 criterion of Nash and Sutcliffe criteria were used to assess the models' performances. An ANN (a four-input multilayer perceptron with ten neurons in the hidden layer) presented the best performance among the studied models (2.93 MJ m-2 d-1 of RMSE). A four-input ANFIS model revealed as an interesting alternative to ANNs (3.14 MJ m-2 d-1 of RMSE). Very limited number of studies has been done on estimation of solar radiation based on ANFIS, and the present one demonstrated the ability of ANFIS to model solar radiation based on temperatures and extraterrestrial radiation. By the way this study demonstrated, for the first time, the ability of GEP models to model solar radiation based on daily atmospheric variables. Despite the accuracy of GEP models was slightly lower than the ANFIS and ANN models the genetic programming models (i.e., GEP) are superior to other artificial intelligence models in giving a simple explicit equation for the phenomenon which shows the relationship between the input and output parameters. This study provided new alternatives for solar radiation estimation based on temperatures.

Magnetofluid Simulations of the Global Solar Wind Including Pickup Ions and Turbulence Modeling

NASA Technical Reports Server (NTRS)

Goldstein, Melvyn L.; Usmanov, Arcadi V.; Matthaeus, William H.

2011-01-01

I will describe a three-dimensional magnetohydrodynamic model of the solar wind that takes into account turbulent heating of the wind by velocity and magnetic fluctuations as well as a variety of effects produced by interstellar pickup protons. In this report, the interstellar pickup protons are treated as one fluid and the protons and electrons are treated together as a second fluid. The model equations include a Reynolds decomposition of the plasma velocity and magnetic field into mean and fluctuating quantities, as well as energy transfer from interstellar pickup protons to solar wind protons that results in the deceleration of the solar wind. The model is used to simulate the global steady-state structure of the solar wind in the region from 0.3 to 100 AU. Where possible, the model is compared with Voyager data. Initial results from generalization to a three-fluid model is described elsewhere in this session.

Variation of solar cell sensitivity and solar radiation on tilted surfaces

NASA Technical Reports Server (NTRS)

Klucher, T. M.

1978-01-01

The validity is studied that one of various insolation models used to compute solar radiation incident on tilted surfaces from global data measured on horizontal surfaces. The variation of solar cell sensitivity to solar radiation is determined over a wide range of atmospheric condition. A new model was formulated that reduced the deviations between measured and predicted insolation to less than 3 percent. Evaluation of solar cell sensitivity data indicates small change (2-3 percent) in sensitivity from winter to summer for tilted cells. The feasibility of using such global data as a means for calibrating terrestrial solar cells is discussed.

A machine learning approach to estimation of downward solar radiation from satellite-derived data products: An application over a semi-arid ecosystem in the U.S.

PubMed

Zhou, Qingtao; Flores, Alejandro; Glenn, Nancy F; Walters, Reggie; Han, Bangshuai

2017-01-01

Shortwave solar radiation is an important component of the surface energy balance and provides the principal source of energy for terrestrial ecosystems. This paper presents a machine learning approach in the form of a random forest (RF) model for estimating daily downward solar radiation flux at the land surface over complex terrain using MODIS (MODerate Resolution Imaging Spectroradiometer) remote sensing data. The model-building technique makes use of a unique network of 16 solar flux measurements in the semi-arid Reynolds Creek Experimental Watershed and Critical Zone Observatory, in southwest Idaho, USA. Based on a composite RF model built on daily observations from all 16 sites in the watershed, the model simulation of downward solar radiation matches well with the observation data (r2 = 0.96). To evaluate model performance, RF models were built from 12 of 16 sites selected at random and validated against the observations at the remaining four sites. Overall root mean square errors (RMSE), bias, and mean absolute error (MAE) are small (range: 37.17 W/m2-81.27 W/m2, -48.31 W/m2-15.67 W/m2, and 26.56 W/m2-63.77 W/m2, respectively). When extrapolated to the entire watershed, spatiotemporal patterns of solar flux are largely consistent with expected trends in this watershed. We also explored significant predictors of downward solar flux in order to reveal important properties and processes controlling downward solar radiation. Based on the composite RF model built on all 16 sites, the three most important predictors to estimate downward solar radiation include the black sky albedo (BSA) near infrared band (0.858 μm), BSA visible band (0.3-0.7 μm), and clear day coverage. This study has important implications for improving the ability to derive downward solar radiation through a fusion of multiple remote sensing datasets and can potentially capture spatiotemporally varying trends in solar radiation that is useful for land surface hydrologic and terrestrial ecosystem modeling.

A machine learning approach to estimation of downward solar radiation from satellite-derived data products: An application over a semi-arid ecosystem in the U.S.

PubMed Central

Flores, Alejandro; Glenn, Nancy F.; Walters, Reggie; Han, Bangshuai

2017-01-01

Shortwave solar radiation is an important component of the surface energy balance and provides the principal source of energy for terrestrial ecosystems. This paper presents a machine learning approach in the form of a random forest (RF) model for estimating daily downward solar radiation flux at the land surface over complex terrain using MODIS (MODerate Resolution Imaging Spectroradiometer) remote sensing data. The model-building technique makes use of a unique network of 16 solar flux measurements in the semi-arid Reynolds Creek Experimental Watershed and Critical Zone Observatory, in southwest Idaho, USA. Based on a composite RF model built on daily observations from all 16 sites in the watershed, the model simulation of downward solar radiation matches well with the observation data (r2 = 0.96). To evaluate model performance, RF models were built from 12 of 16 sites selected at random and validated against the observations at the remaining four sites. Overall root mean square errors (RMSE), bias, and mean absolute error (MAE) are small (range: 37.17 W/m2-81.27 W/m2, -48.31 W/m2-15.67 W/m2, and 26.56 W/m2-63.77 W/m2, respectively). When extrapolated to the entire watershed, spatiotemporal patterns of solar flux are largely consistent with expected trends in this watershed. We also explored significant predictors of downward solar flux in order to reveal important properties and processes controlling downward solar radiation. Based on the composite RF model built on all 16 sites, the three most important predictors to estimate downward solar radiation include the black sky albedo (BSA) near infrared band (0.858 μm), BSA visible band (0.3–0.7 μm), and clear day coverage. This study has important implications for improving the ability to derive downward solar radiation through a fusion of multiple remote sensing datasets and can potentially capture spatiotemporally varying trends in solar radiation that is useful for land surface hydrologic and terrestrial ecosystem modeling. PMID:28777811

Variability of the Martian thermospheric temperatures during the last 7 Martian Years

NASA Astrophysics Data System (ADS)

Gonzalez-Galindo, Francisco; Lopez-Valverde, Miguel Angel; Millour, Ehouarn; Forget, François

2014-05-01

The temperatures and densities in the Martian upper atmosphere have a significant influence over the different processes producing atmospheric escape. A good knowledge of the thermosphere and its variability is thus necessary in order to better understand and quantify the atmospheric loss to space and the evolution of the planet. Different global models have been used to study the seasonal and interannual variability of the Martian thermosphere, usually considering three solar scenarios (solar minimum, solar medium and solar maximum conditions) to take into account the solar cycle variability. However, the variability of the solar activity within the simulated period of time is not usually considered in these models. We have improved the description of the UV solar flux included on the General Circulation Model for Mars developed at the Laboratoire de Météorologie Dynamique (LMD-MGCM) in order to include its observed day-to-day variability. We have used the model to simulate the thermospheric variability during Martian Years 24 to 30, using realistic UV solar fluxes and dust opacities. The model predicts and interannual variability of the temperatures in the upper thermosphere that ranges from about 50 K during the aphelion to up to 150 K during perihelion. The seasonal variability of temperatures due to the eccentricity of the Martian orbit is modified by the variability of the solar flux within a given Martian year. The solar rotation cycle produces temperature oscillations of up to 30 K. We have also studied the response of the modeled thermosphere to the global dust storms in Martian Year 25 and Martian Year 28. The atmospheric dynamics are significantly modified by the global dust storms, which induces significant changes in the thermospheric temperatures. The response of the model to the presence of both global dust storms is in good agreement with previous modeling results (Medvedev et al., Journal of Geophysical Research, 2013). As expected, the simulated ionosphere is also sensitive to the variability of the solar activity. Acknowledgemnt: Francisco González-Galindo is funded by a CSIC JAE-Doc contract financed by the European Social Fund

Future mission studies: Preliminary comparisons of solar flux models

NASA Technical Reports Server (NTRS)

Ashrafi, S.

1991-01-01

The results of comparisons of the solar flux models are presented. (The wavelength lambda = 10.7 cm radio flux is the best indicator of the strength of the ionizing radiations such as solar ultraviolet and x-ray emissions that directly affect the atmospheric density thereby changing the orbit lifetime of satellites. Thus, accurate forecasting of solar flux F sub 10.7 is crucial for orbit determination of spacecrafts.) The measured solar flux recorded by National Oceanic and Atmospheric Administration (NOAA) is compared against the forecasts made by Schatten, MSFC, and NOAA itself. The possibility of a combined linear, unbiased minimum-variance estimation that properly combines all three models into one that minimizes the variance is also discussed. All the physics inherent in each model are combined. This is considered to be the dead-end statistical approach to solar flux forecasting before any nonlinear chaotic approach.

Solar Luminosity on the Main Sequence, Standard Model and Variations

NASA Astrophysics Data System (ADS)

Ayukov, S. V.; Baturin, V. A.; Gorshkov, A. B.; Oreshina, A. V.

2017-05-01

Our Sun became Main Sequence star 4.6 Gyr ago according Standard Solar Model. At that time solar luminosity was 30% lower than current value. This conclusion is based on assumption that Sun is fueled by thermonuclear reactions. If Earth's albedo and emissivity in infrared are unchanged during Earth history, 2.3 Gyr ago oceans had to be frozen. This contradicts to geological data: there was liquid water 3.6-3.8 Gyr ago on Earth. This problem is known as Faint Young Sun Paradox. We analyze luminosity change in standard solar evolution theory. Increase of mean molecular weight in the central part of the Sun due to conversion of hydrogen to helium leads to gradual increase of luminosity with time on the Main Sequence. We also consider several exotic models: fully mixed Sun; drastic change of pp reaction rate; Sun consisting of hydrogen and helium only. Solar neutrino observations however exclude most non-standard solar models.

Improvement and Application of Atmospheric Radiative Transfer Models for Prediction of the Climatic Effects of Aerosol

NASA Technical Reports Server (NTRS)

Bergstrom, Robert W.; Mlawer, Eli J.; Sokolik, Irina N.; Clough, Shepard A.; Toon, Owen B.

1998-01-01

This paper presents a radiative transfer model that has been developed to accurately predict the atmospheric radiant flux in both the infrared and the solar spectrum with a minimum of computational effort. The model is designed to be included in numerical climate models. To assess the accuracy of the model, the results are compared to other more detailed models for several standard cases in the solar and thermal spectrum. As the thermal spectrum has been treated in other publications, we focus here on the solar part of the spectrum. We perform several example calculations focussing on the question of absorption of solar radiation by gases and aerosols.

Improvement and Application of Atmospheric Radiative Transfer Models for Prediction of the Climatic Effects of Aerosol

NASA Technical Reports Server (NTRS)

Bergstrom, Robert W.

1998-01-01

This paper presents a radiative transfer model that has been developed to accurately predict the atmospheric radiant flux in both the infrared and the solar spectrum with a minimum of computational effort. The model is designed to be included in numerical climate models. To assess the accuracy of the model, the results are compared to other more detailed models for several standard cases in the solar and thermal spectrum. As the thermal spectrum has been treated in other publications we focus here on the solar part of the spectrum. We perform several example calculations focussing on the question of absorption of solar radiation by gases and aerosols.

Solar Control of Earth's Ionosphere: Observations from Solar Cycle 23

NASA Astrophysics Data System (ADS)

Doe, R. A.; Thayer, J. P.; Solomon, S. C.

2005-05-01

A nine year database of sunlit E-region electron density altitude profiles (Ne(z)) measured by the Sondrestrom ISR has been partitioned over a 30-bin parameter space of averaged 10.7 cm solar radio flux (F10.7) and solar zenith angle (χ) to investigate long-term solar and thermospheric variability, and to validate contemporary EUV photoionization models. A two stage filter, based on rejection of Ne(z) profiles with large Hall to Pedersen ratio, is used to minimize auroral contamination. Resultant filtered mean Ne(z) compares favorably with subauroral Ne measured for the same F10.7 and χ conditions at the Millstone Hill ISR. Mean Ne, as expected, increases with solar activity and decreases with large χ, and the variance around mean Ne is shown to be greatest at low F10.7 (solar minimum). ISR-derived mean Ne is compared with two EUV models: (1) a simple model without photoelectrons and based on the 5 -- 105 nm EUVAC model solar flux [Richards et al., 1994] and (2) the GLOW model [Solomon et al., 1988; Solomon and Abreu, 1989] suitably modified for inclusion of XUV spectral components and photoelectron flux. Across parameter space and for all altitudes, Model 2 provides a closer match to ISR mean Ne and suggests that the photoelectron and XUV enhancements are essential to replicate measured plasma densities below 150 km. Simulated Ne variance envelopes, given by perturbing the Model 2 neutral atmosphere input by the measured extremum in Ap, F10.7, and Te, are much narrower than ISR-derived geophysical variance envelopes. We thus conclude that long-term variability of the EUV spectra dominates over thermospheric variability and that EUV spectral variability is greatest at solar minimum. ISR -- model comparison also provides evidence for the emergence of an H (Lyman β) Ne feature at solar maximum. Richards, P. G., J. A. Fennelly, and D. G. Torr, EUVAC: A solar EUV flux model for aeronomic calculations, J. Geophys. Res., 99, 8981, 1994. Solomon, S. C., P. B. Hays, and V. J. Abreu, The auroral 6300 Å emission: Observations and Modeling, J. Geophys. Res., 93, 9867, 1988. Solomon, S. C. and V. J. Abreu, The 630 nm dayglow, J. Geophys. Res., 94, 6817, 1989.

Orbit Stability of OSIRIS-REx in the Vicinity of Bennu Using a High-Fidelity Solar Radiation Model

NASA Technical Reports Server (NTRS)

Williams, Trevor W.; Hughes, Kyle M.; Mashiku, Alinda K.; Longuski, James M.

2015-01-01

Solar radiation pressure is one of the largest perturbing forces on the OSIRISRex trajectory as it orbits the asteroid Bennu. In this work, we investigate how forces due to solar radiation perturb the OSIRIS-REx trajectory in a high-fidelity model. The model accounts for Bennu's non-spherical gravity field, third-body gravity forces from the Sun and Jupiter, as well as solar radiation forces acting on a simplified spacecraft model. Such high-fidelity simulations indicate significant solar radiation pressure perturbations from the nominal orbit. Modifications to the initial design of the nominal orbit are found using a variation of parameters approach that reduce the perturbation in eccentricity by a factor of one-half.

Forecasting of global solar radiation using anfis and armax techniques

NASA Astrophysics Data System (ADS)

Muhammad, Auwal; Gaya, M. S.; Aliyu, Rakiya; Aliyu Abdulkadir, Rabi'u.; Dauda Umar, Ibrahim; Aminu Yusuf, Lukuman; Umar Ali, Mudassir; Khairi, M. T. M.

2018-01-01

Procurement of measuring device, maintenance cost coupled with calibration of the instrument contributed to the difficulty in forecasting of global solar radiation in underdeveloped countries. Most of the available regressional and mathematical models do not capture well the behavior of the global solar radiation. This paper presents the comparison of Adaptive Neuro Fuzzy Inference System (ANFIS) and Autoregressive Moving Average with eXogenous term (ARMAX) in forecasting global solar radiation. Full-Scale (experimental) data of Nigerian metrological agency, Sultan Abubakar III international airport Sokoto was used to validate the models. The simulation results demonstrated that the ANFIS model having achieved MAPE of 5.34% outperformed the ARMAX model. The ANFIS could be a valuable tool for forecasting the global solar radiation.

Solar wind stream evolution at large heliocentric distances - Experimental demonstration and the test of a model

NASA Technical Reports Server (NTRS)

Gosling, J. T.; Hundhausen, A. J.; Bame, S. J.

1976-01-01

A stream propagation model which neglects all dissipation effects except those occurring at shock interfaces, was used to compare Pioneer-10 solar wind speed observations, during the time when Pioneer 10, the earth, and the sun were coaligned, with near-earth Imp-7 observations of the solar wind structure, and with the theoretical predictions of the solar wind structure at Pioneer 10 derived from the Imp-7 measurements, using the model. The comparison provides a graphic illustration of the phenomenon of stream steepening in the solar wind with the attendant formation of forward-reverse shock pairs and the gradual decay of stream amplitudes with increasing heliocentric distance. The comparison also provides a qualitative test of the stream propagation model.

Semiempirical Two-Dimensional Magnetohydrodynamic Model of the Solar Corona and Interplanetary Medium

NASA Technical Reports Server (NTRS)

Sittler, Edward C., Jr.; Guhathakurta, Madhulika

1999-01-01

We have developed a two-dimensional semiempirical MHD model of the solar corona and solar wind. The model uses empirically derived electron density profiles from white-light coronagraph data measured during the Skylub period and an empirically derived model of the magnetic field which is fitted to observed streamer topologies, which also come from the white-light coronagraph data The electron density model comes from that developed by Guhathakurta and coworkers. The electron density model is extended into interplanetary space by using electron densities derived from the Ulysses plasma instrument. The model also requires an estimate of the solar wind velocity as a function of heliographic latitude and radial component of the magnetic field at 1 AU, both of which can be provided by the Ulysses spacecraft. The model makes estimates as a function of radial distance and latitude of various fluid parameters of the plasma such as flow velocity V, effective temperature T(sub eff), and effective heat flux q(sub eff), which are derived from the equations of conservation of mass, momentum, and energy, respectively. The term effective indicates that wave contributions could be present. The model naturally provides the spiral pattern of the magnetic field far from the Sun and an estimate of the large-scale surface magnetic field at the Sun, which we estimate to be approx. 12 - 15 G. The magnetic field model shows that the large-scale surface magnetic field is dominated by an octupole term. The model is a steady state calculation which makes the assumption of azimuthal symmetry and solves the various conservation equations in the rotating frame of the Sun. The conservation equations are integrated along the magnetic field direction in the rotating frame of the Sun, thus providing a nearly self-consistent calculation of the fluid parameters. The model makes a minimum number of assumptions about the physics of the solar corona and solar wind and should provide a very accurate empirical description of the solar corona and solar wind Once estimates of mass density rho, flow velocity V, effective temperature T(sub eff), effective heat flux q(sub eff), and magnetic field B are computed from the model and waves are assumed unimportant, all other plasma parameters such as Mach number, Alfven speed, gyrofrequency, etc. can be derived as a function of radial distance and latitude from the Sun. The model can be used as a planning tool for such missions as Slar Probe and provide an empirical framework for theoretical models of the solar corona and solar wind The model will be used to construct a semiempirical MHD description of the steady state solar corona and solar wind using the SOHO Large Angle Spectrometric Coronagraph (LASCO) polarized brightness white-light coronagraph data, SOHO Extreme Ultraviolet Imaging Telescope data, and Ulysses plasma data.

Recent variability of the solar spectral irradiance and its impact on climate modelling

NASA Astrophysics Data System (ADS)

Ermolli, I.; Matthes, K.; Dudok de Wit, T.; Krivova, N. A.; Tourpali, K.; Weber, M.; Unruh, Y. C.; Gray, L.; Langematz, U.; Pilewskie, P.; Rozanov, E.; Schmutz, W.; Shapiro, A.; Solanki, S. K.; Woods, T. N.

2013-04-01

The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE (SOlar Radiation and Climate Experiment) satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of recent chemistry-climate model (CCM) simulations have shown that this might have significant implications on the Earth's atmosphere. Motivated by these results, we summarize here our current knowledge of SSI variability and its impact on Earth's climate. We present a detailed overview of existing SSI measurements and provide thorough comparison of models available to date. SSI changes influence the Earth's atmosphere, both directly, through changes in shortwave (SW) heating and therefore, temperature and ozone distributions in the stratosphere, and indirectly, through dynamical feedbacks. We investigate these direct and indirect effects using several state-of-the art CCM simulations forced with measured and modelled SSI changes. A unique asset of this study is the use of a common comprehensive approach for an issue that is usually addressed separately by different communities. We show that the SORCE measurements are difficult to reconcile with earlier observations and with SSI models. Of the five SSI models discussed here, specifically NRLSSI (Naval Research Laboratory Solar Spectral Irradiance), SATIRE-S (Spectral And Total Irradiance REconstructions for the Satellite era), COSI (COde for Solar Irradiance), SRPM (Solar Radiation Physical Modelling), and OAR (Osservatorio Astronomico di Roma), only one shows a behaviour of the UV and visible irradiance qualitatively resembling that of the recent SORCE measurements. However, the integral of the SSI computed with this model over the entire spectral range does not reproduce the measured cyclical changes of the total solar irradiance, which is an essential requisite for realistic evaluations of solar effects on the Earth's climate in CCMs. We show that within the range provided by the recent SSI observations and semi-empirical models discussed here, the NRLSSI model and SORCE observations represent the lower and upper limits in the magnitude of the SSI solar cycle variation. The results of the CCM simulations, forced with the SSI solar cycle variations estimated from the NRLSSI model and from SORCE measurements, show that the direct solar response in the stratosphere is larger for the SORCE than for the NRLSSI data. Correspondingly, larger UV forcing also leads to a larger surface response. Finally, we discuss the reliability of the available data and we propose additional coordinated work, first to build composite SSI data sets out of scattered observations and to refine current SSI models, and second, to run coordinated CCM experiments.

A Solar Data Model for Use in Virtual Observatories

NASA Astrophysics Data System (ADS)

Reardon, K. P.; Bentley, R. D.; Messerotti, M.; Giordano, S.

2004-05-01

The creation of a virtual solar observatories relies heavily on the merging of the metadata describing different datasets into a common form so that it can be handled in a standard way for all associated resources. In order to bring together the varied data descriptions that already exist, it is necessary to have a common framework on which all the different datasets can be represented. The definition of this framework is done through a data model which attempts to provide a simplified but realistic description of the various entities that make up a data set or solar resource. We present the solar data model which has been developed as part of the European Grid of Solar Observations (EGSO) project. This model attempts to include many of the different elements in the field of solar physics, including data producers, data sets, event lists, and data providers. This global picture can then be used to focus on the particular elements required for a specific implementation. We present the different aspects of the model and describe some systems in which portions of this model have been implemented.

Characteristics of shocks in the solar corona, as inferred from radio, optical, and theoretical investigations

NASA Technical Reports Server (NTRS)

Maxwell, A.; Dryer, M.

1982-01-01

Solar radio bursts of spectral type II provide one of the chief diagnostics for the propagation of shocks through the solar corona. Radio data on the shocks are compared with computer models for propagation of fast-mode MHD shocks through the solar corona. Data on coronal shocks and high-velocity ejecta from solar flares are then discussed in terms of a general model consisting of three main velocity regimes.

Acceleration of the Fast Solar Wind by Solitary Waves in Coronal Holes

NASA Technical Reports Server (NTRS)

Ofman, Leon

2001-01-01

The purpose of this investigation is to develop a new model for the acceleration of the fast solar wind by nonlinear. time-dependent multidimensional MHD simulations of waves in solar coronal holes. Preliminary computational studies indicate that nonlinear waves are generated in coronal holes by torsional Alfv\\'{e}n waves. These waves in addition to thermal conduction may contribute considerably to the accelerate the solar wind. Specific goals of this proposal are to investigate the generation of nonlinear solitary-like waves and their effect on solar wind acceleration by numerical 2.5D MHD simulation of coronal holes with a broad range of plasma and wave parameters; to study the effect of random disturbances at the base of a solar coronal hole on the fast solar wind acceleration with a more advanced 2.5D MHD model and to compare the results with the available observations; to extend the study to a full 3D MHD simulation of fast solar wind acceleration with a more realistic model of a coronal hole and solar boundary conditions. The ultimate goal of the three year study is to model the, fast solar wind in a coronal hole, based on realistic boundary conditions in a coronal hole near the Sun, and the coronal hole structure (i.e., density, temperature. and magnetic field geometry,) that will become available from the recently launched SOHO spacecraft.

Acceleration of the Fast Solar Wind by Solitary Waves in Coronal Holes

NASA Technical Reports Server (NTRS)

Ofman, Leon

2000-01-01

The purpose of this investigation is to develop a new model for the acceleration of the fast solar wind by nonlinear, time-dependent multidimensional MHD simulations of waves in solar coronal holes. Preliminary computational studies indicate that solitary-like waves are generated in coronal holes nonlinearly by torsional Alfven waves. These waves in addition to thermal conduction may contribute considerably to the accelerate the solar wind. Specific goals of this proposal are to investigate the generation of nonlinear solitary-like waves and their effect on solar wind acceleration by numerical 2.5D MHD simulation of coronal holes with a broad range of plasma and wave parameters; to study the effect of random disturbances at the base of a solar coronal hole on the fast solar wind acceleration with a more advanced 2.5D MHD model and to compare the results with the available observations; to extend the study to a full 3D MHD simulation of fast solar wind acceleration with a more realistic model of a coronal hole and solar boundary conditions. The ultimate goal of the three year study is to model the fast solar wind in a coronal hole, based on realistic boundary conditions in a coronal hole near the Sun, and the coronal hole structure (i.e., density, temperature, and magnetic field geometry) that will become available from the recently launched SOHO spacecraft.

3D ELECTRON DENSITY DISTRIBUTIONS IN THE SOLAR CORONA DURING SOLAR MINIMA: ASSESSMENT FOR MORE REALISTIC SOLAR WIND MODELING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Patoul, Judith de; Foullon, Claire; Riley, Pete, E-mail: j.depatoul@exeter.ac.uk, E-mail: c.foullon@exeter.ac.uk, E-mail: rileype@saic.com

Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996–1997 and 2008–2010), devoid of coronal mass ejections. The goals are to derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method and to compare the results between the two solar minima and with two magnetohydrodynamic models. First, we confirm that the values of the density distribution in thermodynamic models aremore » more realistic than in polytropic ones. The tomography provides more accurate distributions in the polar regions, and we find that the density in tomographic and thermodynamic solutions varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the predicted large-scale heliospheric current sheet or its helmet streamer but can follow the locations of pseudo-streamers. We deduce that tomography offers reliable density distributions in the corona, reproducing the slow time evolution of coronal structures, without prior knowledge of the coronal magnetic field over a full rotation. Finally, we suggest that the highest-density structures show a differential rotation well above the surface depending on how they are magnetically connected to the surface. Such valuable information on the rotation of large-scale structures could help to connect the sources of the solar wind to their in situ counterparts in future missions such as Solar Orbiter and Solar Probe Plus.« less

Models of Solar Wind Structures and Their Interaction with the Earth's Space Environment

NASA Astrophysics Data System (ADS)

Watermann, J.; Wintoft, P.; Sanahuja, B.; Saiz, E.; Poedts, S.; Palmroth, M.; Milillo, A.; Metallinou, F.-A.; Jacobs, C.; Ganushkina, N. Y.; Daglis, I. A.; Cid, C.; Cerrato, Y.; Balasis, G.; Aylward, A. D.; Aran, A.

2009-11-01

The discipline of “Space Weather” is built on the scientific foundation of solar-terrestrial physics but with a strong orientation toward applied research. Models describing the solar-terrestrial environment are therefore at the heart of this discipline, for both physical understanding of the processes involved and establishing predictive capabilities of the consequences of these processes. Depending on the requirements, purely physical models, semi-empirical or empirical models are considered to be the most appropriate. This review focuses on the interaction of solar wind disturbances with geospace. We cover interplanetary space, the Earth’s magnetosphere (with the exception of radiation belt physics), the ionosphere (with the exception of radio science), the neutral atmosphere and the ground (via electromagnetic induction fields). Space weather relevant state-of-the-art physical and semi-empirical models of the various regions are reviewed. They include models for interplanetary space, its quiet state and the evolution of recurrent and transient solar perturbations (corotating interaction regions, coronal mass ejections, their interplanetary remnants, and solar energetic particle fluxes). Models of coupled large-scale solar wind-magnetosphere-ionosphere processes (global magnetohydrodynamic descriptions) and of inner magnetosphere processes (ring current dynamics) are discussed. Achievements in modeling the coupling between magnetospheric processes and the neutral and ionized upper and middle atmospheres are described. Finally we mention efforts to compile comprehensive and flexible models from selections of existing modules applicable to particular regions and conditions in interplanetary space and geospace.

Basic Modeling of the Solar Atmosphere and Spectrum

NASA Technical Reports Server (NTRS)

Avrett, Eugene H.; Wagner, William J. (Technical Monitor)

2000-01-01

During the last three years we have continued the development of extensive computer programs for constructing realistic models of the solar atmosphere and for calculating detailed spectra to use in the interpretation of solar observations. This research involves two major interrelated efforts: work by Avrett and Loeser on the Pandora computer program for optically thick non-LTE modeling of the solar atmosphere including a wide range of physical processes, and work by Kurucz on the detailed high-resolution synthesis of the solar spectrum using data for over 58 million atomic and molecular lines. Our objective is to construct atmospheric models from which the calculated spectra agree as well as possible with high-and low-resolution observations over a wide wavelength range. Such modeling leads to an improved understanding of the physical processes responsible for the structure and behavior of the atmosphere.

Kinematic solar dynamo models with a deep meridional flow

NASA Astrophysics Data System (ADS)

Guerrero, G. A.; Muñoz, J. D.

2004-05-01

We develop two different solar dynamo models to verify the hypothesis that a deep meridional flow can restrict the appearance of sunspots below 45°, proposed recently by Nandy & Choudhuri. In the first one, a single polytropic approximation for the density profile was taken, for both radiative and convective zones. In the second one, that of Pinzon & Calvo-Mozo, two polytropes were used to distinguish between both zones. The magnetic buoyancy mechanism proposed by Dikpati & Charbonneau was chosen in both models. We have in fact obtained that a deep meridional flow pushes the maxima of toroidal magnetic field towards the solar equator, but, in contrast to Nandy & Choudhuri, a second zone of maximal fields remains at the poles. The second model, although closely resembling the solar standard model of Bahcall et al., gives solar cycles three times longer than observed.

The Development of New Solar Indices for use in Thermospheric Density Modeling

NASA Technical Reports Server (NTRS)

Tobiska, W. Kent; Bouwer, S. Dave; Bowman, Bruce R.

2006-01-01

New solar indices have been developed to improve thermospheric density modeling for research and operational purposes. Out of 11 new and 4 legacy indices and proxies, we have selected three (F10.7, S10.7, and M10.7) for use in the new JB2006 empirical thermospheric density model. In this work, we report on the development of these solar irradiance indices. The rationale for their use, their definitions, and their characteristics, including the ISO 21348 spectral category and sub-category, wavelength range, solar source temperature region, solar source feature, altitude region of terrestrial atmosphere absorption at unit optical depth, and terrestrial atmosphere thermal processes in the region of maximum energy absorption, are described. We also summarize for each solar index, the facility and instrument(s) used to observe the solar emission, the time frame over which the data exist, the measurement cadence, the data latency, and the research as well as operational availability. The new solar indices are provided in forecast (http://SpaceWx.com) as well as real-time and historical (http://sol.spacenvironment.net/jb2006/) time frames. We describe the forecast methodology, compare results with actual data for active and quiet solar conditions, and compare improvements in F10.7 forecasting with legacy High Accuracy Satellite Drag Model (HASDM) and NOAA SEC forecasts.

Stillwater Hybrid Geo-Solar Power Plant Optimization Analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wendt, Daniel S.; Mines, Gregory L.; Turchi, Craig S.

2015-09-02

The Stillwater Power Plant is the first hybrid plant in the world able to bring together a medium-enthalpy geothermal unit with solar thermal and solar photovoltaic systems. Solar field and power plant models have been developed to predict the performance of the Stillwater geothermal / solar-thermal hybrid power plant. The models have been validated using operational data from the Stillwater plant. A preliminary effort to optimize performance of the Stillwater hybrid plant using optical characterization of the solar field has been completed. The Stillwater solar field optical characterization involved measurement of mirror reflectance, mirror slope error, and receiver position error.more » The measurements indicate that the solar field may generate 9% less energy than the design value if an appropriate tracking offset is not employed. A perfect tracking offset algorithm may be able to boost the solar field performance by about 15%. The validated Stillwater hybrid plant models were used to evaluate hybrid plant operating strategies including turbine IGV position optimization, ACC fan speed and turbine IGV position optimization, turbine inlet entropy control using optimization of multiple process variables, and mixed working fluid substitution. The hybrid plant models predict that each of these operating strategies could increase net power generation relative to the baseline Stillwater hybrid plant operations.« less

An MHD simulation model of time-dependent global solar corona with temporally varying solar-surface magnetic field maps

NASA Astrophysics Data System (ADS)

Hayashi, K.

2013-11-01

We present a model of a time-dependent three-dimensional magnetohydrodynamics simulation of the sub-Alfvenic solar corona and super-Alfvenic solar wind with temporally varying solar-surface boundary magnetic field data. To (i) accommodate observational data with a somewhat arbitrarily evolving solar photospheric magnetic field as the boundary value and (ii) keep the divergence-free condition, we developed a boundary model, here named Confined Differential Potential Field model, that calculates the horizontal components of the magnetic field, from changes in the vertical component, as a potential field confined in a thin shell. The projected normal characteristic method robustly simulates the solar corona and solar wind, in response to the temporal variation of the boundary Br. We conduct test MHD simulations for two periods, from Carrington Rotation number 2009 to 2010 and from Carrington Rotation 2074 to 2075 at solar maximum and minimum of Cycle 23, respectively. We obtained several coronal features that a fixed boundary condition cannot yield, such as twisted magnetic field lines at the lower corona and the transition from an open-field coronal hole to a closed-field streamer. We also obtained slight improvements of the interplanetary magnetic field, including the latitudinal component, at Earth.

Solar-QBO Interaction and Its Impact on Stratospheric Ozone in a Zonally Averaged Photochemical Transport Model of the Middle Atmosphere

DTIC Science & Technology

2007-08-28

Solar- QBO interaction and its impact on stratospheric ozone in a zonally averaged photochemical transport model of the middle atmosphere J. P...investigate the solar cycle modulation of the quasi-biennial oscillation ( QBO ) in stratospheric zonal winds and its impact on stratospheric ozone with an...updated version of the zonally averaged CHEM2D middle atmosphere model. We find that the duration of the westerly QBO phase at solar maximum is 3 months

Midlatitude atmospheric OH response to the most recent 11-y solar cycle.

PubMed

Wang, Shuhui; Li, King-Fai; Pongetti, Thomas J; Sander, Stanley P; Yung, Yuk L; Liang, Mao-Chang; Livesey, Nathaniel J; Santee, Michelle L; Harder, Jerald W; Snow, Martin; Mills, Franklin P

2013-02-05

The hydroxyl radical (OH) plays an important role in middle atmospheric photochemistry, particularly in ozone (O(3)) chemistry. Because it is mainly produced through photolysis and has a short chemical lifetime, OH is expected to show rapid responses to solar forcing [e.g., the 11-y solar cycle (SC)], resulting in variabilities in related middle atmospheric O(3) chemistry. Here, we present an effort to investigate such OH variability using long-term observations (from space and the surface) and model simulations. Ground-based measurements and data from the Microwave Limb Sounder on the National Aeronautics and Space Administration's Aura satellite suggest an ∼7-10% decrease in OH column abundance from solar maximum to solar minimum that is highly correlated with changes in total solar irradiance, solar Mg-II index, and Lyman-α index during SC 23. However, model simulations using a commonly accepted solar UV variability parameterization give much smaller OH variability (∼3%). Although this discrepancy could result partially from the limitations in our current understanding of middle atmospheric chemistry, recently published solar spectral irradiance data from the Solar Radiation and Climate Experiment suggest a solar UV variability that is much larger than previously believed. With a solar forcing derived from the Solar Radiation and Climate Experiment data, modeled OH variability (∼6-7%) agrees much better with observations. Model simulations reveal the detailed chemical mechanisms, suggesting that such OH variability and the corresponding catalytic chemistry may dominate the O(3) SC signal in the upper stratosphere. Continuing measurements through SC 24 are required to understand this OH variability and its impacts on O(3) further.

Midlatitude atmospheric OH response to the most recent 11-y solar cycle

PubMed Central

Wang, Shuhui; Li, King-Fai; Pongetti, Thomas J.; Sander, Stanley P.; Yung, Yuk L.; Liang, Mao-Chang; Livesey, Nathaniel J.; Santee, Michelle L.; Harder, Jerald W.; Snow, Martin; Mills, Franklin P.

2013-01-01

The hydroxyl radical (OH) plays an important role in middle atmospheric photochemistry, particularly in ozone (O3) chemistry. Because it is mainly produced through photolysis and has a short chemical lifetime, OH is expected to show rapid responses to solar forcing [e.g., the 11-y solar cycle (SC)], resulting in variabilities in related middle atmospheric O3 chemistry. Here, we present an effort to investigate such OH variability using long-term observations (from space and the surface) and model simulations. Ground-based measurements and data from the Microwave Limb Sounder on the National Aeronautics and Space Administration’s Aura satellite suggest an ∼7–10% decrease in OH column abundance from solar maximum to solar minimum that is highly correlated with changes in total solar irradiance, solar Mg-II index, and Lyman-α index during SC 23. However, model simulations using a commonly accepted solar UV variability parameterization give much smaller OH variability (∼3%). Although this discrepancy could result partially from the limitations in our current understanding of middle atmospheric chemistry, recently published solar spectral irradiance data from the Solar Radiation and Climate Experiment suggest a solar UV variability that is much larger than previously believed. With a solar forcing derived from the Solar Radiation and Climate Experiment data, modeled OH variability (∼6–7%) agrees much better with observations. Model simulations reveal the detailed chemical mechanisms, suggesting that such OH variability and the corresponding catalytic chemistry may dominate the O3 SC signal in the upper stratosphere. Continuing measurements through SC 24 are required to understand this OH variability and its impacts on O3 further. PMID:23341617

Modelling of electric characteristics of 150-watt peak solar panel using Boltzmann sigmoid function under various temperature and irradiance

NASA Astrophysics Data System (ADS)

Sapteka, A. A. N. G.; Narottama, A. A. N. M.; Winarta, A.; Amerta Yasa, K.; Priambodo, P. S.; Putra, N.

2018-01-01

Solar energy utilized with solar panel is a renewable energy that needs to be studied further. The site nearest to the equator, it is not surprising, receives the highest solar energy. In this paper, a modelling of electrical characteristics of 150-Watt peak solar panels using Boltzmann sigmoid function under various temperature and irradiance is reported. Current, voltage, temperature and irradiance data in Denpasar, a city located at just south of equator, was collected. Solar power meter is used to measure irradiance level, meanwhile digital thermometer is used to measure temperature of front and back panels. Short circuit current and open circuit voltage data was also collected at different temperature and irradiance level. Statistically, the electrical characteristics of 150-Watt peak solar panel can be modelled using Boltzmann sigmoid function with good fit. Therefore, it can be concluded that Boltzmann sigmoid function might be used to determine current and voltage characteristics of 150-Watt peak solar panel under various temperature and irradiance.

Helioseismology Observations of Solar Cycles and Dynamo Modeling

NASA Astrophysics Data System (ADS)

Kosovichev, A. G.; Guerrero, G.; Pipin, V.

2017-12-01

Helioseismology observations from the SOHO and SDO, obtained in 1996-2017, provide unique insight into the dynamics of the Sun's deep interior for two solar cycles. The data allow us to investigate variations of the solar interior structure and dynamics, and compare these variations with dynamo models and simulations. We use results of the local and global helioseismology data processing pipelines at the SDO Joint Science Operations Center (Stanford University) to study solar-cycle variations of the differential rotation, meridional circulation, large-scale flows and global asphericity. By comparing the helioseismology results with the evolution of surface magnetic fields we identify characteristic changes associated the initiation and development of Solar Cycles 23 and 24. For the physical interpretation of observed variations, the results are compared with the current mean-field dynamo models and 3D MHD dynamo simulations. It is shown that the helioseismology inferences provide important constraints on the solar dynamo mechanism, may explain the fundamental difference between the two solar cycles, and also give information about the next solar cycle.

Influences of misprediction costs on solar flare prediction

NASA Astrophysics Data System (ADS)

Huang, Xin; Wang, HuaNing; Dai, XingHua

2012-10-01

The mispredictive costs of flaring and non-flaring samples are different for different applications of solar flare prediction. Hence, solar flare prediction is considered a cost sensitive problem. A cost sensitive solar flare prediction model is built by modifying the basic decision tree algorithm. Inconsistency rate with the exhaustive search strategy is used to determine the optimal combination of magnetic field parameters in an active region. These selected parameters are applied as the inputs of the solar flare prediction model. The performance of the cost sensitive solar flare prediction model is evaluated for the different thresholds of solar flares. It is found that more flaring samples are correctly predicted and more non-flaring samples are wrongly predicted with the increase of the cost for wrongly predicting flaring samples as non-flaring samples, and the larger cost of wrongly predicting flaring samples as non-flaring samples is required for the higher threshold of solar flares. This can be considered as the guide line for choosing proper cost to meet the requirements in different applications.

Understanding Solar Cycle Variability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cameron, R. H.; Schüssler, M., E-mail: cameron@mps.mpg.de

The level of solar magnetic activity, as exemplified by the number of sunspots and by energetic events in the corona, varies on a wide range of timescales. Most prominent is the 11-year solar cycle, which is significantly modulated on longer timescales. Drawing from dynamo theory, together with the empirical results of past solar activity and similar phenomena for solar-like stars, we show that the variability of the solar cycle can be essentially understood in terms of a weakly nonlinear limit cycle affected by random noise. In contrast to ad hoc “toy models” for the solar cycle, this leads to amore » generic normal-form model, whose parameters are all constrained by observations. The model reproduces the characteristics of the variable solar activity on timescales between decades and millennia, including the occurrence and statistics of extended periods of very low activity (grand minima). Comparison with results obtained with a Babcock–Leighton-type dynamo model confirm the validity of the normal-mode approach.« less

Modeling the heliospheric current sheet: Solar cycle variations

NASA Astrophysics Data System (ADS)

Riley, Pete; Linker, J. A.; Mikić, Z.

2002-07-01

In this report we employ an empirically driven, three-dimensional MHD model to explore the evolution of the heliospheric current sheet (HCS) during the course of the solar cycle. We compare our results with a simpler ``constant-speed'' approach for mapping the HCS outward into the solar wind to demonstrate that dynamic effects can substantially deform the HCS in the inner heliosphere (<~5 AU). We find that these deformations are most pronounced at solar minimum and become less significant at solar maximum, when interaction regions are less effective. Although solar maximum is typically associated with transient, rather than corotating, processes, we show that even under such conditions, the HCS can maintain its structure over the course of several solar rotations. While the HCS may almost always be topologically equivalent to a ``ballerina skirt,'' we discuss an interval approaching the maximum of solar cycle 23 (Carrington rotations 1960 and 1961) when the shape would be better described as ``conch shell''-like. We use Ulysses magnetic field measurements to support the model results.

A Temperature-Based Model for Estimating Monthly Average Daily Global Solar Radiation in China

PubMed Central

Li, Huashan; Cao, Fei; Wang, Xianlong; Ma, Weibin

2014-01-01

Since air temperature records are readily available around the world, the models based on air temperature for estimating solar radiation have been widely accepted. In this paper, a new model based on Hargreaves and Samani (HS) method for estimating monthly average daily global solar radiation is proposed. With statistical error tests, the performance of the new model is validated by comparing with the HS model and its two modifications (Samani model and Chen model) against the measured data at 65 meteorological stations in China. Results show that the new model is more accurate and robust than the HS, Samani, and Chen models in all climatic regions, especially in the humid regions. Hence, the new model can be recommended for estimating solar radiation in areas where only air temperature data are available in China. PMID:24605046

The Surface Density Distribution in the Solar Nebula

NASA Technical Reports Server (NTRS)

Davis, Sanford S.

2004-01-01

The commonly used minimum mass power law representation of the pre-solar nebula is reanalyzed using a new cumulative-mass-model. This model predicts a smoother surface density approximation compared with methods based on direct computation of surface density. The density is quantified using two independent analytical formulations. First, a best-fit transcendental function is applied directly to the basic planetary data. Next a solution to the time-dependent disk evolution equation is parametrically adapted to the solar nebula data. The latter model is shown to be a good approximation to the finite-size early Solar Nebula, and by extension to other extra solar protoplanetary disks.

A Snapshot of the Sun Near Solar Minimum: The Whole Heliosphere Interval

NASA Technical Reports Server (NTRS)

Thompson, Barbara J.; Gibson, Sarah E.; Schroeder, Peter C.; Webb, David F.; Arge, Charles N.; Bisi, Mario M.; de Toma, Giuliana; Emery, Barbara A.; Galvin, Antoinette B.; Haber, Deborah A.;

An analytical model of prominence dynamics

NASA Astrophysics Data System (ADS)

Routh, Swati; Saha, Snehanshu; Bhat, Atul; Sundar, M. N.

2018-01-01

Solar prominences are magnetic structures incarcerating cool and dense gas in an otherwise hot solar corona. Prominences can be categorized as quiescent and active. Their origin and the presence of cool gas (∼104 K) within the hot (∼106K) solar corona remains poorly understood. The structure and dynamics of solar prominences was investigated in a large number of observational and theoretical (both analytical and numerical) studies. In this paper, an analytic model of quiescent solar prominence is developed and used to demonstrate that the prominence velocity increases exponentially, which means that some gas falls downward towards the solar surface, and that Alfvén waves are naturally present in the solar prominences. These theoretical predictions are consistent with the current observational data of solar quiescent prominences.

Low-cost production of solar-cell panels

NASA Technical Reports Server (NTRS)

Bickler, D. B.; Gallagher, B. D.; Sanchez, L. E.

1980-01-01

Large-scale production model combines most modern manufacturing techniques to produce silicon-solar-cell panels of low costs by 1982. Model proposes facility capable of operating around the clock with annual production capacity of 20 W of solar cell panels.

Technique for experimental determination of radiation interchange factors in solar wavelengths

NASA Technical Reports Server (NTRS)

Bobco, R. P.; Nolte, L. J.; Wensley, J. R.

1971-01-01

Process obtains solar heating data which support analytical design. Process yields quantitative information on local solar exposure of models which are geometrically and reflectively similar to prototypes under study. Models are tested in a shirtsleeve environment.

Variations of Strahl Properties with Fast and Slow Solar Wind

NASA Technical Reports Server (NTRS)

Figueroa-Vinas, Adolfo; Goldstein, Melvyn L.; Gurgiolo, Chris

2008-01-01

The interplanetary solar wind electron velocity distribution function generally shows three different populations. Two of the components, the core and halo, have been the most intensively analyzed and modeled populations using different theoretical models. The third component, the strahl, is usually seen at higher energies, is confined in pitch-angle, is highly field-aligned and skew. This population has been more difficult to identify and to model in the solar wind. In this work we make use of the high angular, energy and time resolution and three-dimensional data of the Cluster/PEACE electron spectrometer to identify and analyze this component in the ambient solar wind during high and slow speed solar wind. The moment density and fluid velocity have been computed by a semi-numerical integration method. The variations of solar wind density and drift velocity with the general build solar wind speed could provide some insight into the source, origin, and evolution of the strahl.

A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5

NASA Astrophysics Data System (ADS)

Hsu, Juno; Prather, Michael J.; Cameron-Smith, Philip; Veidenbaum, Alex; Nicolau, Alex

2017-07-01

Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18-0.8 µm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. The spectral extension from 0.8 to 12 µm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth's atmosphere.The Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG-SW). Solar-J successfully matches RRTMG-SW's tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. We compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we find a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW's two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW's three different parameterizations are as large as about 20-40 % depending on the solar zenith angles and occur throughout the atmosphere.Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth's atmosphere, for which the three major components - wavelength integration, scattering, and averaging over cloud fields - all have comparably small errors. More accurate solutions with Solar-J come with increased computational costs, about 5 times that of RRTMG-SW for a single atmosphere. There are options for reduced costs or computational acceleration that would bring costs down while maintaining improved fidelity and balanced errors.

A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hsu, Juno; Prather, Michael J.; Cameron-Smith, Philip

Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18–0.8 µm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. Themore » spectral extension from 0.8 to 12 µm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth's atmosphere. Furthermore, the Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG-SW). Solar-J successfully matches RRTMG-SW's tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. Here, we compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we find a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW's two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW's three different parameterizations are as large as about 20–40 % depending on the solar zenith angles and occur throughout the atmosphere. Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth's atmosphere, for which the three major components – wavelength integration, scattering, and averaging over cloud fields – all have comparably small errors. More accurate solutions with Solar-J come with increased computational costs, about 5 times that of RRTMG-SW for a single atmosphere. There are options for reduced costs or computational acceleration that would bring costs down while maintaining improved fidelity and balanced errors.« less

A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5

DOE PAGES

Hsu, Juno; Prather, Michael J.; Cameron-Smith, Philip; ...

2017-01-01

Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18–0.8 µm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. Themore » spectral extension from 0.8 to 12 µm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth's atmosphere. Furthermore, the Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG-SW). Solar-J successfully matches RRTMG-SW's tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. Here, we compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we find a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW's two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW's three different parameterizations are as large as about 20–40 % depending on the solar zenith angles and occur throughout the atmosphere. Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth's atmosphere, for which the three major components – wavelength integration, scattering, and averaging over cloud fields – all have comparably small errors. More accurate solutions with Solar-J come with increased computational costs, about 5 times that of RRTMG-SW for a single atmosphere. There are options for reduced costs or computational acceleration that would bring costs down while maintaining improved fidelity and balanced errors.« less

Flexible Models for Solar Sail Control

NASA Technical Reports Server (NTRS)

Weaver Smith, Suzanne; Song, Haiping; Baker, John R.; Black, Jonathan; Muheim, Danniella M.

2005-01-01

Solar sails employ a unique form of propulsion, gaining momentum from incident and reflected photons. However, the momentum transferred by an individual photon is extremely small. Consequently, a solar sail must have an extremely large surface area and also be extremely light. The flexibility of the sail then must be considered when designing or evaluating control laws. In this paper, solar sail flexibility and its influence on control effectiveness is considered using idealized two-dimensional models to represent physical phenomena rather than a specific design. Differential equations of motion are derived for a distributed parameter model of a flexible solar sail idealized as a rotating central hub with two opposing flexible booms. This idealization is appropriate for solar sail designs in which the vibrational modes of the sail and supporting booms move together allowing the sail mass to be distributed along the booms in the idealized model. A reduced analytical model of the flexible response is considered. Linear feedback torque control is applied at the central hub. Two translational disturbances and a torque disturbance also act at the central hub representing the equivalent effect of deflecting sail shape about a reference line. Transient simulations explore different control designs and their effectiveness for controlling orientation, for reducing flexible motion and for disturbance rejection. A second model also is developed as a two-dimensional "pathfinder" model to calculate the effect of solar sail shape on the resultant thrust, in-plane force and torque at the hub. The analysis is then extended to larger models using the finite element method. The finite element modeling approach is verified by comparing results from a two-dimensional finite element model with those from the analytical model. The utility of the finite element modeling approach for this application is then illustrated through examples based on a full finite element model.

Modeling of the steam hydrolysis in a two-step process for hydrogen production by solar concentrated energy

NASA Astrophysics Data System (ADS)

Valle-Hernández, Julio; Romero-Paredes, Hernando; Pacheco-Reyes, Alejandro

2017-06-01

In this paper the simulation of the steam hydrolysis for hydrogen production through the decomposition of cerium oxide is presented. The thermochemical cycle for hydrogen production consists of the endothermic reduction of CeO2 to lower-valence cerium oxide, at high temperature, where concentrated solar energy is used as a source of heat; and of the subsequent steam hydrolysis of the resulting cerium oxide to produce hydrogen. The modeling of endothermic reduction step was presented at the Solar Paces 2015. This work shows the modeling of the exothermic step; the hydrolysis of the cerium oxide (III) to form H2 and the corresponding initial cerium oxide made at lower temperature inside the solar reactor. For this model, three sections of the pipe where the reaction occurs were considered; the steam water inlet, the porous medium and the hydrogen outlet produced. The mathematical model describes the fluid mechanics; mass and energy transfer occurring therein inside the tungsten pipe. Thermochemical process model was simulated in CFD. The results show a temperature distribution in the solar reaction pipe and allow obtaining the fluid dynamics and the heat transfer within the pipe. This work is part of the project "Solar Fuels and Industrial Processes" from the Mexican Center for Innovation in Solar Energy (CEMIE-Sol).

Spacecraft Charging Current Balance Model Applied to High Voltage Solar Array Operations

NASA Technical Reports Server (NTRS)

Willis, Emily M.; Pour, Maria Z. A.

2016-01-01

Spacecraft charging induced by high voltage solar arrays can result in power losses and degradation of spacecraft surfaces. In some cases, it can even present safety issues for astronauts performing extravehicular activities. An understanding of the dominant processes contributing to spacecraft charging induced by solar arrays is important to current space missions, such as the International Space Station, and to any future space missions that may employ high voltage solar arrays. A common method of analyzing the factors contributing to spacecraft charging is the current balance model. Current balance models are based on the simple idea that the spacecraft will float to a potential such that the current collecting to the surfaces equals the current lost from the surfaces. However, when solar arrays are involved, these currents are dependent on so many factors that the equation becomes quite complicated. In order for a current balance model to be applied to solar array operations, it must incorporate the time dependent nature of the charging of dielectric surfaces in the vicinity of conductors1-3. This poster will present the factors which must be considered when developing a current balance model for high voltage solar array operations and will compare results of a current balance model with data from the Floating Potential Measurement Unit4 on board the International Space Station.

Tomographic Validation of the AWSoM Model of the Inner Corona During Solar Minima

NASA Astrophysics Data System (ADS)

Manchester, W.; Vásquez, A. M.; Lloveras, D. G.; Mac Cormack, C.; Nuevo, F.; Lopez-Fuentes, M.; Frazin, R. A.; van der Holst, B.; Landi, E.; Gombosi, T. I.

2017-12-01

Continuous improvement of MHD three-dimensional (3D) models of the global solar corona, such as the Alfven Wave Solar Model (AWSoM) of the Space Weather Modeling Framework (SWMF), requires testing their ability to reproduce observational constraints at a global scale. To that end, solar rotational tomography based on EUV image time-series can be used to reconstruct the 3D distribution of the electron density and temperature in the inner solar corona (r < 1.25 Rsun). The tomographic results, combined with a global coronal magnetic model, can further provide constraints on the energy input flux required at the coronal base to maintain stable structures. In this work, tomographic reconstructions are used to validate steady-state 3D MHD simulations of the inner corona using the latest version of the AWSoM model. We perform the study for selected rotations representative of solar minimum conditions, when the global structure of the corona is more axisymmetric. We analyse in particular the ability of the MHD simulation to match the tomographic results across the boundary region between the equatorial streamer belt and the surrounding coronal holes. The region is of particular interest as the plasma flow from that zone is thought to be related to the origin of the slow component of the solar wind.

Evaluating predictive models for solar energy growth in the US states and identifying the key drivers

NASA Astrophysics Data System (ADS)

Chakraborty, Joheen; Banerji, Sugata

2018-03-01

Driven by a desire to control climate change and reduce the dependence on fossil fuels, governments around the world are increasing the adoption of renewable energy sources. However, among the US states, we observe a wide disparity in renewable penetration. In this study, we have identified and cleaned over a dozen datasets representing solar energy penetration in each US state, and the potentially relevant socioeconomic and other factors that may be driving the growth in solar. We have applied a number of predictive modeling approaches - including machine learning and regression - on these datasets over a 17-year period and evaluated the relative performance of the models. Our goals were: (1) identify the most important factors that are driving the growth in solar, (2) choose the most effective predictive modeling technique for solar growth, and (3) develop a model for predicting next year’s solar growth using this year’s data. We obtained very promising results with random forests (about 90% efficacy) and varying degrees of success with support vector machines and regression techniques (linear, polynomial, ridge). We also identified states with solar growth slower than expected and representing a potential for stronger growth in future.

Solar total and spectral irradiance reconstruction over last 9000 years

NASA Astrophysics Data System (ADS)

Wu, Chi-Ju; Usoskin, Ilya; Krivova, Natalie; Solanki, Sami K.

2016-07-01

Although the mechanisms of solar influence on Earth climate system are not yet fully understood, solar total and spectral irradiance are considered to be among the main determinants. Solar total irradiance is the total flux of solar radiative energy entering Earth's climate system, whereas the spectral irradiance describes this energy is distributed over the spectrum. Solar irradiance in the UV band is of special importance since it governs chemical processes in the middle and upper atmosphere. On timescales of the 11-year solar cycle and shorter, solar irradiance is measured by space-based instruments while models are needed to reconstruct solar irradiance on longer timescale. The SATIRE-M model (Spectral And Total Irradiance Reconstruction over millennia) is employed in this study to reconstruct solar irradiance from decadal radionuclide isotope data such as 14C and 10Be stored in tree rings and ice cores, respectively. A reconstruction over the last 9000 years will be presented.

Solar Total and Spectral Irradiance Reconstruction over Last 9000 Years

NASA Astrophysics Data System (ADS)

Wu, C. J.; Krivova, N.; Solanki, S. K.; Usoskin, I. G.

2016-12-01

Although the mechanisms of solar influence on Earth climate system are not yet fully understood, solar total and spectral irradiance are considered to be among the main determinants. Solar total irradiance is the total flux of solar radiative energy entering Earth's climate system, whereas the spectral irradiance describes this energy is distributed over the spectrum. Solar irradiance in the UV band is of special importance since it governs chemical processes in the middle and upper atmosphere. On timescales of the 11-year solar cycle and shorter, solar irradiance is measured by space-based instruments while models are needed to reconstruct solar irradiance on longer timescale. The SATIRE-M model (Spectral And Total Irradiance Reconstruction over millennia) is employed in this study to reconstruct solar irradiance from decadal radionuclide isotope data such as 14C and 10Be stored in tree rings and ice cores, respectively. A reconstruction over the last 9000 years will be presented.

Model of spacecraft atomic oxygen and solar exposure microenvironments

NASA Technical Reports Server (NTRS)

Bourassa, R. J.; Pippin, H. G.

1993-01-01

Computer models of environmental conditions in Earth orbit are needed for the following reasons: (1) derivation of material performance parameters from orbital test data, (2) evaluation of spacecraft hardware designs, (3) prediction of material service life, and (4) scheduling spacecraft maintenance. To meet these needs, Boeing has developed programs for modeling atomic oxygen (AO) and solar radiation exposures. The model allows determination of AO and solar ultraviolet (UV) radiation exposures for spacecraft surfaces (1) in arbitrary orientations with respect to the direction of spacecraft motion, (2) overall ranges of solar conditions, and (3) for any mission duration. The models have been successfully applied to prediction of experiment environments on the Long Duration Exposure Facility (LDEF) and for analysis of selected hardware designs for deployment on other spacecraft. The work on these models has been reported at previous LDEF conferences. Since publication of these reports, a revision has been made to the AO calculation for LDEF, and further work has been done on the microenvironments model for solar exposure.

A comparative Thermal Analysis of conventional parabolic receiver tube and Cavity model tube in a Solar Parabolic Concentrator

NASA Astrophysics Data System (ADS)

Arumugam, S.; Ramakrishna, P.; Sangavi, S.

2018-02-01

Improvements in heating technology with solar energy is gaining focus, especially solar parabolic collectors. Solar heating in conventional parabolic collectors is done with the help of radiation concentration on receiver tubes. Conventional receiver tubes are open to atmosphere and loose heat by ambient air currents. In order to reduce the convection losses and also to improve the aperture area, we designed a tube with cavity. This study is a comparative performance behaviour of conventional tube and cavity model tube. The performance formulae were derived for the cavity model based on conventional model. Reduction in overall heat loss coefficient was observed for cavity model, though collector heat removal factor and collector efficiency were nearly same for both models. Improvement in efficiency was also observed in the cavity model’s performance. The approach towards the design of a cavity model tube as the receiver tube in solar parabolic collectors gave improved results and proved as a good consideration.

The effects of solarization on the performance of a gas turbine

NASA Astrophysics Data System (ADS)

Homann, Christiaan; van der Spuy, Johan; von Backström, Theodor

2016-05-01

Various hybrid solar gas turbine configurations exist. The Stellenbosch University Solar Power Thermodynamic (SUNSPOT) cycle consists of a heliostat field, solar receiver, primary Brayton gas turbine cycle, thermal storage and secondary Rankine steam cycle. This study investigates the effect of the solarization of a gas turbine on its performance and details the integration of a gas turbine into a solar power plant. A Rover 1S60 gas turbine was modelled in Flownex, a thermal-fluid system simulation and design code, and validated against a one-dimensional thermodynamic model at design input conditions. The performance map of a newly designed centrifugal compressor was created and implemented in Flownex. The effect of the improved compressor on the performance of the gas turbine was evident. The gas turbine cycle was expanded to incorporate different components of a CSP plant, such as a solar receiver and heliostat field. The solarized gas turbine model simulates the gas turbine performance when subjected to a typical variation in solar resource. Site conditions at the Helio100 solar field were investigated and the possibility of integrating a gas turbine within this system evaluated. Heat addition due to solar irradiation resulted in a decreased fuel consumption rate. The influence of the additional pressure drop over the solar receiver was evident as it leads to decreased net power output. The new compressor increased the overall performance of the gas turbine and compensated for pressure losses incurred by the addition of solar components. The simulated integration of the solarized gas turbine at Helio100 showed potential, although the solar irradiation is too little to run the gas turbine on solar heat alone. The simulation evaluates the feasibility of solarizing a gas turbine and predicts plant performance for such a turbine cycle.

Stratospheric O3 changes during 2001-2010: the small role of solar flux variations in a chemical transport model

NASA Astrophysics Data System (ADS)

Dhomse, S. S.; Chipperfield, M. P.; Feng, W.; Ball, W. T.; Unruh, Y. C.; Haigh, J. D.; Krivova, N. A.; Solanki, S. K.; Smith, A. K.

2013-10-01

Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O3 changes during solar cycle 23 (1996-2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate middle atmospheric O3 using three different solar flux data sets (SORCE, NRL-SSI and SATIRE-S). Simulated O3 changes are compared with Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O3 anomalies from all solar flux data sets show good agreement with the observations, despite the different flux variations. The off-line CTM reproduces these changes through dynamical information contained in the analyses. A notable feature during this period is a robust positive solar signal in the tropical middle stratosphere, which is due to realistic dynamical changes in our simulations. Ozone changes in the lower mesosphere cannot be used to discriminate between solar flux data sets due to large uncertainties and the short time span of the observations. Overall this study suggests that, in a CTM, the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O3 changes during 2001-2010.

GISS GCMAM Modeled Climate Responses to Total and Spectral Solar Forcing on Decadal and Centennial Time Scales

NASA Astrophysics Data System (ADS)

Wen, Guoyong; Cahalan, Robert; Rind, David; Jonas, Jeffrey; Pilewskie, Peter; Harder, Jerry

2014-05-01

We examine the influence of the SORCE (Solar Radiation and Climate Experiment) SIM (Spectral Irradiance Monitor) observed spectral solar irradiance (SSI) variations on Earth's climate. We apply two reconstructed spectral solar forcing scenarios, one SIM based, the other based on the SATIRE (Spectral And Total Irradiance REconstruction) model, as inputs to the GISS (Goddard Institute for Space Studies) GCMAM (Global Climate Middle Atmosphere Model) to examine the climate responses on decadal and centennial time scales. We show that the atmosphere has different temperature, ozone, and dynamic responses to the two solar spectral forcing scenarios, even when the variations in TSI (Total Solar Irradiance) are the same. We find that solar variations under either scenario contribute a small fraction of the observed temperature increase since the industrial revolution. The trend of global averaged surface air temperature response to the SIM-based solar forcing is 0.02 °C/century, about half of the temperature trend to the SATIRE-based SSI. However the temporal variation of the surface air temperature for the SIM-based solar forcing scenario is much larger compared to its SATIRE counterpart. Further research is required to examine TSI and SSI variations in the ascending phase of solar cycle 24, to assess their implications for the solar influence on climate.

GISS GCMAM Modeled Climate Responses to Total and Spectral Solar Forcing on Decadal and Centennial Time Scales

NASA Astrophysics Data System (ADS)

Wen, G.; Cahalan, R. F.; Rind, D. H.; Jonas, J.; Pilewskie, P.; Harder, J. W.; Krivova, N.

2014-12-01

We examine the influence of the SORCE (Solar Radiation and Climate Experiment) SIM (Spectral Irradiance Monitor) observed spectral solar irradiance (SSI) variations on Earth's climate. We apply two reconstructed spectral solar forcing scenarios, one SIM based, the other based on the SATIRE (Spectral And Total Irradiance REconstruction) model, as inputs to the GISS (Goddard Institute for Space Studies) GCMAM (Global Climate Middle Atmosphere Model) to examine the climate responses on decadal and centennial time scales. We show that the atmosphere has different temperature, ozone, and dynamic responses to the two solar spectral forcing scenarios, even when the variations in TSI (Total Solar Irradiance) are the same. We find that solar variations under either scenario contribute a small fraction of the observed temperature increase since the industrial revolution. The trend of global averaged surface air temperature response to the SIM-based solar forcing is 0.02 °C/century, about half of the temperature trend to the SATIRE-based SSI. However the temporal variation of the surface air temperature for the SIM-based solar forcing scenario is much larger compared to its SATIRE counterpart. Further research is required to examine TSI and SSI variations in the ascending phase of solar cycle 24, to assess their implications for the solar influence on climate.

Solar spectral irradiance variability in cycle 24: observations and models

NASA Astrophysics Data System (ADS)

Marchenko, Sergey V.; DeLand, Matthew T.; Lean, Judith L.

2016-12-01

Utilizing the excellent stability of the Ozone Monitoring Instrument (OMI), we characterize both short-term (solar rotation) and long-term (solar cycle) changes of the solar spectral irradiance (SSI) between 265 and 500 nm during the ongoing cycle 24. We supplement the OMI data with concurrent observations from the Global Ozone Monitoring Experiment-2 (GOME-2) and Solar Radiation and Climate Experiment (SORCE) instruments and find fair-to-excellent, depending on wavelength, agreement among the observations, and predictions of the Naval Research Laboratory Solar Spectral Irradiance (NRLSSI2) and Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE-S) models.

Modeling and simulation of temperature effect in polycrystalline silicon PV cells

NASA Astrophysics Data System (ADS)

Marcu, M.; Niculescu, T.; Slusariuc, R. I.; Popescu, F. G.

2016-06-01

Due to the human needs of energy, there is a need to apply new technologies in energy conversion to supply the demand of clean and cheap energy in the context of environmental issues. Renewable energy sources like solar energy has one of the highest potentials. In this paper, solar panel is the key part of a photovoltaic system which converts solar energy to electrical energy. The purpose of this paper is to give a MATLAB/ Simulink simulation for photovoltaic module based on the one-diode model of a photovoltaic cell made of polycrystalline silicon. This model reveals the effect of the ambient temperature and the heating of the panel due to the solar infrared radiation. Also the measurements on the solar cell exposed to solar radiation can confirm the simulation.

Students To Compete in Model Solar Car Race

Science.gov Websites

., May 8, 1998 — Middle school students from across Colorado will design, build and race model solar build solar-powered vehicles no larger than 16 inches wide, 24 inches long and 12 inches high. The sun's

Magnetopause Standoff Position Changes and Geosynchronous Orbit Crossings: Models and Observations

NASA Astrophysics Data System (ADS)

Collado-Vega, Y. M.; Rastaetter, L.; Sibeck, D. G.

2017-12-01

The Earth's magnetopause is the boundary that mostly separates the solar wind with the Earth's magnetosphere. Its location has been studied and estimated via simulation models, observational data and empirical models. This research aims to study the changes of the magnetopause standoff location due to different solar wind conditions using a combination of all the different methods. We will use the Run-On-Request capabilities within the MHD models available from the Community Coordinated Modeling Center (CCMC) at NASA Goddard Space Flight Center, specifically BATS-R-US (SWMF), OpenGGCM, LFM and GUMICS models. The magnetopause standoff position prediction and response time to the solar wind changes will then be compared to results from available empirical models (e.g. Shue et al. 1998), and to THEMIS, Cluster, Geotail and MMS missions magnetopause crossing observations. We will also use times of extreme solar wind conditions where magnetopause crossings have been observed by the GOES satellites. Rigorous analysis/comparison of observations and empirical models is critical in determining magnetosphere dynamics for model validation. This research goes also hand in hand with the efforts of the working group at the CCMC/LWS International Forum for Space Weather Capabilities Assessment workshop that aims to analyze different events to define metrics for model-data comparison. Preliminary results of this particular research show that there are some discrepancies between the MHD models standoff positions of the dayside magnetopause for the same solar wind conditions that include an increase in solar wind dynamic pressure and a step function in the IMF Bz component. In cases of nominal solar wind conditions, it has been observed that the models do mostly agree with the observational data from the different satellite missions.

Statistical and observational research of solar flare for total spectra and geometrical features

NASA Astrophysics Data System (ADS)

Nishimoto, S.; Watanabe, K.; Imada, S.; Kawate, T.; Lee, K. S.

2017-12-01

Impulsive energy release phenomena such as solar flares, sometimes affect to the solar-terrestrial environment. Usually, we use soft X-ray flux (GOES class) as the index of flare scale. However, the magnitude of effect to the solar-terrestrial environment is not proportional to that scale. To identify the relationship between solar flare phenomena and influence to the solar-terrestrial environment, we need to understand the full spectrum of solar flares. There is the solar flare irradiance model named the Flare Irradiance Spectral Model (FISM) (Chamberlin et al., 2006, 2007, 2008). The FISM can estimate solar flare spectra with high wavelength resolution. However, this model can not express the time evolution of emitted plasma during the solar flare, and has low accuracy on short wavelength that strongly effects and/or controls the total flare spectra. For the purpose of obtaining the time evolution of total solar flare spectra, we are performing statistical analysis of the electromagnetic data of solar flares. In this study, we select solar flare events larger than M-class from the Hinode flare catalogue (Watanabe et al., 2012). First, we focus on the EUV emission observed by the SDO/EVE. We examined the intensities and time evolutions of five EUV lines of 55 flare events. As a result, we found positive correlation between the "soft X-ray flux" and the "EUV peak flux" for all EVU lines. Moreover, we found that hot lines peaked earlier than cool lines of the EUV light curves. We also examined the hard X-ray data obtained by RHESSI. When we analyzed 163 events, we found good correlation between the "hard X-ray intensity" and the "soft X-ray flux". Because it seems that the geometrical features of solar flares effect to those time evolutions, we also looked into flare ribbons observed by SDO/AIA. We examined 21 flare events, and found positive correlation between the "GOES duration" and the "ribbon length". We also found positive correlation between the "ribbon length" and the "ribbon distance", however, there was no remarkable correlation of the "ribbon width". To understand physical process of flare emission, we performed numerical simulation (Imada et al., 2015), and compared with the observational flare model. We also discuss the flare numerical model which can be fitted to the observational flare model.

The Sun as a variable star: Solar and stellar irradiance variations; Colloquium of the International Astronomical Union, 143rd, Boulder, CO, Jun. 20-25, 1993

NASA Technical Reports Server (NTRS)

Pap, Judit M. (Editor); Froehlich, Claus (Editor); Hudson, Hugh S. (Editor); Tobiska, W. Kent (Editor)

1994-01-01

Variations in solar and stellar irradiances have long been of interest. An International Astronomical Union (IAU) colloquium reviewed such relevant subjects as observations, theoretical interpretations, and empirical and physical models, with a special emphasis on climatic impact of solar irradiance variability. Specific topics discussed included: (1) General Reviews on Observations of Solar and Stellar Irradiance Variability; (2) Observational Programs for Solar and Stellar Irradiance Variability; (3) Variability of Solar and Stellar Irradiance Related to the Network, Active Regions (Sunspots and Plages), and Large-Scale Magnetic Structures; (4) Empirical Models of Solar Total and Spectral Irradiance Variability; (5) Solar and Stellar Oscillations, Irradiance Variations and their Interpretations; and (6) The Response of the Earth's Atmosphere to Solar Irradiance Variations and Sun-Climate Connections.

How Reliable Is the Prediction of Solar Wind Background?

NASA Astrophysics Data System (ADS)

Jian, Lan K.; MacNeice, Peter; Taktakishvili, Aleksandre; Odstrcil, Dusan; Jackson, Bernard; Yu, Hsiu-Shan; Riley, Pete; Sokolov, Igor

2015-04-01

The prediction of solar wind background is a necessary part of space weather forecasting. Multiple coronal and heliospheric models have been installed at the Community Coordinated Modeling Center (CCMC) to produce the solar wind, including the Wang-Sheely-Arge (WSA)-Enlil model, MHD-Around-a-Sphere (MAS)-Enlil model, Space Weather Modeling Framework (SWMF), and heliospheric tomography using interplanetary scintillation (IPS) data. By comparing the modeling results with the OMNI data over 7 Carrington rotations in 2007, we have conducted a third-party validation of these models for the near-Earth solar wind. This work will help the models get ready for the transition from research to operation. Besides visual comparison, we have quantitatively assessed the models’ capabilities in reproducing the time series and statistics of solar wind parameters. Using improved algorithms, we have identified magnetic field sector boundaries (SBs) and slow-to-fast stream interaction regions (SIRs) as focused structures. The success rate of capturing them and the time offset vary largely with models. For this period, the 2014 version of MAS-Enlil model works best for SBs, and the heliospheric tomography works best for SIRs. General strengths and weaknesses for each model are identified to provide an unbiased reference to model developers and users.

Theory for optimal design of waveguiding light concentrators in photovoltaic microcell arrays.

PubMed

Semichaevsky, Andrey V; Johnson, Harley T; Yoon, Jongseung; Nuzzo, Ralph G; Li, Lanfang; Rogers, John

2011-06-10

Efficiency of ultrathin flexible solar photovoltaic silicon microcell arrays can be significantly improved using nonimaging solar concentrators. A fluorophore is introduced to match the solar spectrum and the low-reflectivity wavelength range of Si, reduce the escape losses, and allow the nontracking operation. In this paper we optimize our solar concentrators using a luminescent/nonluminescent photon transport model. Key modeling results are compared quantitatively to experiments and are in good agreement with the latter. Our solar concentrator performance is not limited by the dye self-absorption. Bending deformations of the flexible solar collectors do not result in their indirect gain degradation compared to flat solar concentrators with the same projected area.

Determining the metallicity of the solar envelope using seismic inversion techniques

NASA Astrophysics Data System (ADS)

Buldgen, G.; Salmon, S. J. A. J.; Noels, A.; Scuflaire, R.; Dupret, M. A.; Reese, D. R.

2017-11-01

The solar metallicity issue is a long-lasting problem of astrophysics, impacting multiple fields and still subject to debate and uncertainties. While spectroscopy has mostly been used to determine the solar heavy elements abundance, helioseismologists attempted providing a seismic determination of the metallicity in the solar convective envelope. However, the puzzle remains since two independent groups provided two radically different values for this crucial astrophysical parameter. We aim at providing an independent seismic measurement of the solar metallicity in the convective envelope. Our main goal is to help provide new information to break the current stalemate amongst seismic determinations of the solar heavy element abundance. We start by presenting the kernels, the inversion technique and the target function of the inversion we have developed. We then test our approach in multiple hare-and-hounds exercises to assess its reliability and accuracy. We then apply our technique to solar data using calibrated solar models and determine an interval of seismic measurements for the solar metallicity. We show that our inversion can indeed be used to estimate the solar metallicity thanks to our hare-and-hounds exercises. However, we also show that further dependencies in the physical ingredients of solar models lead to a low accuracy. Nevertheless, using various physical ingredients for our solar models, we determine metallicity values between 0.008 and 0.014.

Extrapolating Solar Dynamo Models Throughout the Heliosphere

NASA Astrophysics Data System (ADS)

Cox, B. T.; Miesch, M. S.; Augustson, K.; Featherstone, N. A.

2014-12-01

There are multiple theories that aim to explain the behavior of the solar dynamo, and their associated models have been fiercely contested. The two prevailing theories investigated in this project are the Convective Dynamo model that arises from the pure solving of the magnetohydrodynamic equations, as well as the Babcock-Leighton model that relies on sunspot dissipation and reconnection. Recently, the supercomputer simulations CASH and BASH have formed models of the behavior of the Convective and Babcock-Leighton models, respectively, in the convective zone of the sun. These models show the behavior of the models within the sun, while much less is known about the effects these models may have further away from the solar surface. The goal of this work is to investigate any fundamental differences between the Convective and Babcock-Leighton models of the solar dynamo outside of the sun and extending into the solar system via the use of potential field source surface extrapolations implemented via python code that operates on data from CASH and BASH. The use of real solar data to visualize supergranular flow data in the BASH model is also used to learn more about the behavior of the Babcock-Leighton Dynamo. From the process of these extrapolations it has been determined that the Babcock-Leighton model, as represented by BASH, maintains complex magnetic fields much further into the heliosphere before reverting into a basic dipole field, providing 3D visualisations of the models distant from the sun.

The calculation of theoretical chromospheric models and the interpretation of the solar spectrum

NASA Technical Reports Server (NTRS)

Avrett, Eugene H.

1994-01-01

Since the early 1970s we have been developing the extensive computer programs needed to construct models of the solar atmosphere and to calculate detailed spectra for use in the interpretation of solar observations. This research involves two major related efforts: work by Avrett and Loeser on the Pandora computer program for non-LTE modeling of the solar atmosphere including a wide range of physical processes, and work by Kurucz on the detailed synthesis of the solar spectrum based on opacity data for over 58 million atomic and molecular lines. Our goals are to determine models of the various features observed on the sun (sunspots, different components of quiet and active regions, and flares) by means of physically realistic models, and to calculate detailed spectra at all wavelengths that match observations of those features. These two goals are interrelated: discrepancies between calculated and observed spectra are used to determine improvements in the structure of the models, and in the detailed physical processes used in both the model calculations and the spectrum calculations. The atmospheric models obtained in this way provide not only the depth variation of various atmospheric parameters, but also a description of the internal physical processes that are responsible for nonradiative heating, and for solar activity in general.

The calculation of theoretical chromospheric models and the interpretation of solar spectra from rockets and spacecraft

NASA Technical Reports Server (NTRS)

Avrett, Eugene H.

1993-01-01

Since the early 1970s we have been developing the extensive computer programs needed to construct models of the solar atmosphere and to calculate detailed spectra for use in the interpretation of solar observations. This research involves two major related efforts: work by Avrett and Loeser on the Pandora computer program for non-LTE modeling of the solar atmosphere including a wide range of physical processes, and work by Kurucz on the detailed synthesis of the solar spectrum based on opacity data for over 58 million atomic and molecular lines. Our goals are to determine models of the various features observed on the Sun (sunspots, different components of quiet and active regions, and flares) by means of physically realistic models, and to calculate detailed spectra at all wavelengths that match observations of those features. These two goals are interrelated: discrepancies between calculated and observed spectra are used to determine improvements in the structure of the models, and in the detailed physical processes used in both the model calculations and the spectrum calculations. The atmospheric models obtained in this way provide not only the depth variation of various atmospheric parameters, but also a description of the internal physical processes that are responsible for non-radiative heating, and for solar activity in general.

A model for proton-irradiated GaAs solar cells

NASA Technical Reports Server (NTRS)

Wilson, J. W.; Walker, G. H.; Outlaw, R. A.; Stock, L. V.

1982-01-01

A simple model for proton radiation damage in GaAs heteroface solar cells is developed. The model includes the effects of spatial nonuniformity of low energy proton damage. Agreement between the model and experimental proton damage data for GaAs heteroface solar cells is satisfactory. An extension of the model to include angular isotropy, as is appropriate for protons in space, is shown to result in significantly less cell damage than for normal proton incidence.

Mars Radiation Surface Model

NASA Astrophysics Data System (ADS)

Alzate, N.; Grande, M.; Matthiae, D.

2017-09-01

Planetary Space Weather Services (PSWS) within the Europlanet H2020 Research Infrastructure have been developed following protocols and standards available in Astrophysical, Solar Physics and Planetary Science Virtual Observatories. Several VO-compliant functionalities have been implemented in various tools. The PSWS extends the concepts of space weather and space situational awareness to other planets in our Solar System and in particular to spacecraft that voyage through it. One of the five toolkits developed as part of these services is a model dedicated to the Mars environment. This model has been developed at Aberystwyth University and the Institut fur Luft- und Raumfahrtmedizin (DLR Cologne) using modeled average conditions available from Planetocosmics. It is available for tracing propagation of solar events through the Solar System and modeling the response of the Mars environment. The results have been synthesized into look-up tables parameterized to variable solar wind conditions at Mars.

A NEW THREE-DIMENSIONAL SOLAR WIND MODEL IN SPHERICAL COORDINATES WITH A SIX-COMPONENT GRID

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Xueshang; Zhang, Man; Zhou, Yufen, E-mail: fengx@spaceweather.ac.cn

In this paper, we introduce a new three-dimensional magnetohydrodynamics numerical model to simulate the steady state ambient solar wind from the solar surface to 215 R {sub s} or beyond, and the model adopts a splitting finite-volume scheme based on a six-component grid system in spherical coordinates. By splitting the magnetohydrodynamics equations into a fluid part and a magnetic part, a finite volume method can be used for the fluid part and a constrained-transport method able to maintain the divergence-free constraint on the magnetic field can be used for the magnetic induction part. This new second-order model in space andmore » time is validated when modeling the large-scale structure of the solar wind. The numerical results for Carrington rotation 2064 show its ability to produce structured solar wind in agreement with observations.« less

Modeling the Solar Dust Environment at 9.5 Solar Radii: Revealing Radiance Trends with MESSENGER Star Tracker Data

NASA Astrophysics Data System (ADS)

Strong, S. B.; Strikwerda, T.; Lario, D.; Raouafi, N.; Decker, R.

2010-12-01

The main components of interplanetary dust are created through destruction, erosion, and collision of asteroids and comets (e.g. Mann et al. 2006). Solar radiation forces distribute these interplanetary dust particles throughout the solar system. The percent contribution of these source particulates to the net interplanetary dust distribution can reveal information about solar nebula conditions, within which these objects are formed. In the absence of observational data (e.g. Helios, Pioneer), specifically at distances less than 0.3 AU, the precise dust distributions remain unknown and limited to 1 AU extrapolative models (e.g. Mann et al. 2003). We have developed a model suitable for the investigation of scattered dust and electron irradiance incident on a sensor for distances inward of 1 AU. The model utilizes the Grün et al. (1985) and Mann et al. (2004) dust distribution theory combined with Mie theory and Thomson electron scattering to determine the magnitude of solar irradiance scattered towards an optical sensor as a function of helio-ecliptic latitude and longitude. MESSENGER star tracker observations (launch to 2010) of the ambient celestial background combined with Helios data (Lienert et al. 1982) reveal trends in support of the model predictions. This analysis further emphasizes the need to characterize the inner solar system dust environment in anticipation of near-Solar missions.

A discussion of plausible solar irradiance variations, 1700-1992

NASA Technical Reports Server (NTRS)

Hoyt, Douglas V.; Schatten, Kenneth H.

1993-01-01

From satellite observations the solar total irradiance is known to vary. Sunspot blocking, facular emission, and network emission are three identified causes for the variations. In this paper we examine several different solar indices measured over the past century that are potential proxy measures for the Sun's irradiance. These indices are (1) the equatorial solar rotation rate, (2) the sunspot structure, the decay rate of individual sunspots, and the number of sunspots without umbrae, and (3) the length and decay rate of the sunspot cycle. Each index can be used to develop a model for the Sun's total irradiance as seen at the Earth. Three solar indices allow the irradiance to be modeled back to the mid-1700s. The indices are (1) the length of the solar cycle, (2) the normalized decay rate of the solar cycle, and (3) the mean level of solar activity. All the indices are well correlated, and one possible explanation for their nearly simultaneous variations is changes in the Sun's convective energy transport. Although changes in the Sun's convective energy transport are outside the realm of normal stellar structure theory (e.g., mixing length theory), one can imagine variations arising from even the simplest view of sunspots as vertical tubes of magnetic flux, which would serve as rigid pillas affecting the energy flow patterns by ensuring larger-scale eddies. A composite solar irradiance model, based upon these proxies, is compared to the northern hemisphere temperature depatures for 1700-1992. Approximately 71% of the decadal variance in the last century can be modeled with these solar indices, although this analysis does not include anthropogenic or other variations which would affect the results. Over the entire three centuries, approx. 50% of the variance is modeled. Both this analysis and previous similar analyses have correlations of model solar irradiances and measured Earth surface temperatures that are significant at better than the 95% confidence level. To understand our present climate variations, we must place the anthropogenic variations in the context of natural variability from solar, volcanic, oceanic, and other sources.

Precipitation response to solar geoengineering in a high-resolution tropical-cyclone permitting coupled general circulation model

NASA Astrophysics Data System (ADS)

Irvine, P. J.; Keith, D.; Dykema, J. A.; Vecchi, G. A.; Horowitz, L. W.

2016-12-01

Solar geoengineering may limit or even halt the rise in global-average surface temperatures. Evidence from the geoMIP model intercomparison project shows that idealized geoengineering can greatly reduce temperature changes on a region-by-region basis. If solar geoengineering is used to hold radiative forcing or surface temperatures constant in the face of rising CO2, then the global evaporation and precipitation rates will be reduced below pre-industrial. The spartial and frequency distribution of the precipitation response is, however, much less well understood. There is limited evidence that solar geoengineering may reduce extreme precipitation events more that it reduces mean precipitation, but that evidence is based on relatively course resolution models that may to a poor job representing the distribution of extreme precipitation in the current climate. The response of global and regional climate, as well as tropical cyclone (TC) activity, to increasing solar geoengineering is explored through experiments with climate models spanning a broad range of atmospheric resolutions. Solar geoengineering is represented by an idealized adjustment of the solar constant that roughly halves the rate of increase in radiative forcing in a scenario with increasing CO2 concentration. The coarsest resolution model has approximately a 2-degree global resolution, representative of the typical resolution of past GCMs used to explore global response to CO2 increase, and its response is compared to that of two tropical cyclone permitting GCMs of approximately 0.5 and 0.25 degree resolution (FLOR and HiFLOR). The models have exactly the same ocean and sea-ice components, as well as the same parameterizations and parameter settings. These high-resolution models are used for real-time seasonal prediction, providing a unified framework for seasonal-to-multidecadal climate modeling. We assess the extreme precipitation response, comparing the frequency distribution of extreme events with and without solar geoengineering. We compare our results to two prior studies of the response of climate extremes to solar geoengineering.

Validation of the Earth atmosphere models using the EUV solar occultation data from the CORONAS and PROBA 2 instruments

NASA Astrophysics Data System (ADS)

Slemzin, Vladimir; Kuzin, Sergey; Berghmans, David; Pertsov, Andrey; Dominique, Marie; Ulyanov, Artyom; Gaikovich, Konstantin

Absorption in the atmosphere below 500 km results in attenuation of the solar EUV flux, variation of its spectra and distortion of solar images acquired by solar EUV instruments operating on LEO satellites even on solar synchronous orbits. Occultation measurements are important for planning of solar observations from these satellites, and can be used for monitoring the upper atmosphere as well as for studying its response to the solar activity. We present the results of the occultation measurements of the solar EUV radiation obtained by the CORONAS-F/SPIRIT telescope at high solar activity (2002), by the CORONAS-Photon/TESIS telescope at low activity (2009), and by the SWAP telescope and LYRA radiometer onboard the PROBA 2 satellite at moderate activity (2010). The measured attenuation profiles and the retrieved linear extinction coefficients at the heights 200-500 km are compared with simulations by the NRLMSIS-00 and DTM2013 atmospheric models. It was shown that the results of simulations by the DTM2013 model are well agreed with the data of measurements at all stages of solar activity and in presence of the geomagnetic storm, whereas the results of the NRLMSISE-00 model significantly diverge from the measurements, in particular, at high and low activity. The research leading to these results has received funding from the European Union’s Seventh Programme for Research, Technological Development and Demonstration under Grant Agreement “eHeroes” (project No.284461, www.eheroes.eu).

Stochastic Fluctuations in a Babcock-Leighton Model of the Solar Cycle

NASA Astrophysics Data System (ADS)

Charbonneau, Paul; Dikpati, Mausumi

2000-11-01

We investigate the effect of stochastic fluctuations on a flux transport model of the solar cycle based on the Babcock-Leighton mechanism. Specifically, we make use of our recent flux transport model (Dikpati & Charbonneau) to investigate the consequences of introducing large-amplitude stochastic fluctuations in either or both the meridional flow and poloidal source term in the model. Solar cycle-like oscillatory behavior persists even for fluctuation amplitudes as high as 300%, thus demonstrating the inherent robustness of this class of solar cycle models. We also find that high-amplitude fluctuations lead to a spread of cycle amplitude and duration showing a statistically significant anticorrelation, comparable to that observed in sunspot data. This is a feature of the solar cycle that is notoriously difficult to reproduce with dynamo models based on mean field electrodynamics and relying only on nonlinearities associated with the back-reaction of the Lorentz force to produce amplitude modulation. Another noteworthy aspect of our flux transport model is the fact that meridional circulation in the convective envelope acts as a ``clock'' regulating the tempo of the solar cycle; shorter-than-average cycles are typically soon followed by longer-than-average cycles. In other words, the oscillation exhibits good phase locking, a property that also characterizes the solar activity cycle. This shows up quite clearly in our model, but we argue that it is in fact a generic property of flux transport models based on the Babcock-Leighton mechanism, and relies on meridional circulation as the primary magnetic field transport agent.

Modelling Solar Energetic Particle Propagation in Realistic Heliospheric Solar Wind Conditions Using a Combined MHD and Stochastic Differential Equation Approach

NASA Astrophysics Data System (ADS)

Wijsen, N.; Poedts, S.; Pomoell, J.

2017-12-01

Solar energetic particles (SEPs) are high energy particles originating from solar eruptive events. These particles can be energised at solar flare sites during magnetic reconnection events, or in shock waves propagating in front of coronal mass ejections (CMEs). These CME-driven shocks are in particular believed to act as powerful accelerators of charged particles throughout their propagation in the solar corona. After escaping from their acceleration site, SEPs propagate through the heliosphere and may eventually reach our planet where they can disrupt the microelectronics on satellites in orbit and endanger astronauts among other effects. Therefore it is of vital importance to understand and thereby build models capable of predicting the characteristics of SEP events. The propagation of SEPs in the heliosphere can be described by the time-dependent focused transport equation. This five-dimensional parabolic partial differential equation can be solved using e.g., a finite difference method or by integrating a set of corresponding first order stochastic differential equations. In this work we take the latter approach to model SEP events under different solar wind and scattering conditions. The background solar wind in which the energetic particles propagate is computed using a magnetohydrodynamic model. This allows us to study the influence of different realistic heliospheric configurations on SEP transport. In particular, in this study we focus on exploring the influence of high speed solar wind streams originating from coronal holes that are located close to the eruption source region on the resulting particle characteristics at Earth. Finally, we discuss our upcoming efforts towards integrating our particle propagation model with time-dependent heliospheric MHD space weather modelling.

MODIS Solar Diffuser: Modelled and Actual Performance

NASA Technical Reports Server (NTRS)

Waluschka, Eugene; Xiong, Xiao-Xiong; Esposito, Joe; Wang, Xin-Dong; Krebs, Carolyn (Technical Monitor)

2001-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument's solar diffuser is used in its radiometric calibration for the reflective solar bands (VIS, NTR, and SWIR) ranging from 0.41 to 2.1 micron. The sun illuminates the solar diffuser either directly or through a attenuation screen. The attenuation screen consists of a regular array of pin holes. The attenuated illumination pattern on the solar diffuser is not uniform, but consists of a multitude of pin-hole images of the sun. This non-uniform illumination produces small, but noticeable radiometric effects. A description of the computer model used to simulate the effects of the attenuation screen is given and the predictions of the model are compared with actual, on-orbit, calibration measurements.

New formulation feed method in tariff model of solar PV in Indonesia

NASA Astrophysics Data System (ADS)

Djamal, Muchlishah Hadi; Setiawan, Eko Adhi; Setiawan, Aiman

2017-03-01

Geographically, Indonesia has 18 latitudes that correlated strongly with the potential of solar radiation for the implementation of solar photovoltaic (PV) technologies. This is becoming the basis assumption to develop a proportional model of Feed In Tariff (FIT), consequently the FIT will be vary, according to the various of latitudes in Indonesia. This paper proposed a new formulation of solar PV FIT based on the potential of solar radiation and some independent variables such as latitude, longitude, Levelized Cost of Electricity (LCOE), and also socio-economic. The Principal Component Regression (PCR) method is used to analyzed the correlation of six independent variables C1-C6 then three models of FIT are presented. Model FIT-2 is chosen because it has a small residual value and has higher financial benefit compared to the other models. This study reveals the value of variable FIT associated with solar energy potential in each region, can reduce the total FIT to be paid by the state around 80 billion rupiahs in 10 years of 1 MW photovoltaic operation at each 34 provinces in Indonesia.

The Predictability of Advection-dominated Flux-transport Solar Dynamo Models

NASA Astrophysics Data System (ADS)

Sanchez, Sabrina; Fournier, Alexandre; Aubert, Julien

2014-01-01

Space weather is a matter of practical importance in our modern society. Predictions of forecoming solar cycles mean amplitude and duration are currently being made based on flux-transport numerical models of the solar dynamo. Interested in the forecast horizon of such studies, we quantify the predictability window of a representative, advection-dominated, flux-transport dynamo model by investigating its sensitivity to initial conditions and control parameters through a perturbation analysis. We measure the rate associated with the exponential growth of an initial perturbation of the model trajectory, which yields a characteristic timescale known as the e-folding time τ e . The e-folding time is shown to decrease with the strength of the α-effect, and to increase with the magnitude of the imposed meridional circulation. Comparing the e-folding time with the solar cycle periodicity, we obtain an average estimate for τ e equal to 2.76 solar cycle durations. From a practical point of view, the perturbations analyzed in this work can be interpreted as uncertainties affecting either the observations or the physical model itself. After reviewing these, we discuss their implications for solar cycle prediction.

Towards Building Reliable, High-Accuracy Solar Irradiance Database For Arid Climates

NASA Astrophysics Data System (ADS)

Munawwar, S.; Ghedira, H.

2012-12-01

Middle East's growing interest in renewable energy has led to increased activity in solar technology development with the recent commissioning of several utility-scale solar power projects and many other commercial installations across the Arabian Peninsula. The region, lying in a virtually rainless sunny belt with a typical daily average solar radiation exceeding 6 kWh/m2, is also one of the most promising candidates for solar energy deployment. However, it is not the availability of resource, but its characterization and reasonably accurate assessment that determines the application potential. Solar irradiance, magnitude and variability inclusive, is the key input in assessing the economic feasibility of a solar system. The accuracy of such data is of critical importance for realistic on-site performance estimates. This contribution aims to identify the key stages in developing a robust solar database for desert climate by focusing on the challenges that an arid environment presents to parameterization of solar irradiance attenuating factors. Adjustments are proposed based on the currently available resource assessment tools to produce high quality data for assessing bankability. Establishing and maintaining ground solar irradiance measurements is an expensive affair and fairly limited in time (recently operational) and space (fewer sites) in the Gulf region. Developers within solar technology industry, therefore, rely on solar radiation models and satellite-derived data for prompt resource assessment needs. It is imperative that such estimation tools are as accurate as possible. While purely empirical models have been widely researched and validated in the Arabian Peninsula's solar modeling history, they are known to be intrinsically site-specific. A primal step to modeling is an in-depth understanding of the region's climate, identifying the key players attenuating radiation and their appropriate characterization to determine solar irradiance. Physical approach based models and tools can subsequently be recalibrated or improvised to address the unique features of characteristically high aerosol load, frequent dust episodes and yet, typically clear skies, in the Gulf's primarily arid region. For example, though clouds are an important factor, radiative extinction in desert climates is primarily due to aerosols; a fact that needs to be taken into consideration since most of the existing solar radiation models are technically cloud-based. Satellite derived irradiance, although carrying a tag of uncertainties (5-10%), have special relevance in the Gulf due to lack of long-term data at the source of application. Satellite data can be merged or combined with short-term ground measurements, by various techniques available in the literature, to smooth out uncertainties in the data and build high-accuracy long-term solar irradiance profiles. Such concatenation is of particular interest to investors as it provides vital information on solar resource variability.

THE CHROMOSPHERIC SOLAR LIMB BRIGHTENING AT RADIO, MILLIMETER, SUB-MILLIMETER, AND INFRARED WAVELENGTHS

DOE Office of Scientific and Technical Information (OSTI.GOV)

De la Luz, V.

2016-07-10

Observations of the emission at radio, millimeter, sub-millimeter, and infrared wavelengths in the center of the solar disk validate the autoconsistence of semi-empirical models of the chromosphere. Theoretically, these models must reproduce the emission at the solar limb. In this work, we tested both the VALC and C7 semi-empirical models by computing their emission spectrum in the frequency range from 2 GHz to 10 THz at solar limb altitudes. We calculate the Sun's theoretical radii as well as their limb brightening. Non-local thermodynamic equilibrium was computed for hydrogen, electron density, and H{sup −}. In order to solve the radiative transfermore » equation, a three-dimensional (3D) geometry was employed to determine the ray paths, and Bremsstrahlung, H{sup −}, and inverse Bremsstrahlung opacity sources were integrated in the optical depth. We compared the computed solar radii with high-resolution observations at the limb obtained by Clark. We found that there are differences between the observed and computed solar radii of 12,000 km at 20 GHz, 5000 km at 100 GHz, and 1000 km at 3 THz for both semi-empirical models. A difference of 8000 km in the solar radii was found when comparing our results against the heights obtained from H α observations of spicules-off at the solar limb. We conclude that the solar radii cannot be reproduced by VALC and C7 semi-empirical models at radio—infrared wavelengths. Therefore, the structures in the high chromosphere provide a better measurement of the solar radii and their limb brightening as shown in previous investigations.« less

A Smoothed Eclipse Model for Solar Electric Propulsion Trajectory Optimization

NASA Technical Reports Server (NTRS)

Aziz, Jonathan D.; Scheeres, Daniel J.; Parker, Jeffrey S.; Englander, Jacob A.

2017-01-01

Solar electric propulsion (SEP) is the dominant design option for employing low-thrust propulsion on a space mission. Spacecraft solar arrays power the SEP system but are subject to blackout periods during solar eclipse conditions. Discontinuity in power available to the spacecraft must be accounted for in trajectory optimization, but gradient-based methods require a differentiable power model. This work presents a power model that smooths the eclipse transition from total eclipse to total sunlight with a logistic function. Example trajectories are computed with differential dynamic programming, a second-order gradient-based method.

Stratospheric O3 changes during 2001-2010: The small role of solar flux variations in a CTM

NASA Astrophysics Data System (ADS)

Dhomse, Sandip; Chipperfield, Martyn; Feng, Wuhu; Ball, William; Unruh, Yvonne; Haigh, Joanna; Krivova, Natalie; Solanki, Sami

2013-04-01

Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) shows different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL, SATIRE-S). Some modelling studies have suggested that stratospheric O3 changes during solar cycle 23 (1996-2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate stratospheric O3 using 3 different solar flux datasets (SORCE, NRL-SSI and SATIRE-S). Simulated O3 changes are compared with Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O3 anomalies using all solar flux datasets show good agreement with the observations, despite the different flux variations. A notable feature during this period is a robust positive solar signal in the tropical middle stratosphere. The CTM reproduces these changes through dynamical information contained in the analyses. Changes in the upper stratosphere cannot be used to discriminate between solar flux datasets due to large uncertainties in the O3 observations. Overall this study suggests that the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O3 changes during 2001-2010.

Construction of a Model Solar Building. A Learning Experience for Coastal and Oceanic Awareness Studies, No. 318. [Project COAST].

ERIC Educational Resources Information Center

Delaware Univ., Newark. Coll. of Education.

This activity is designed for secondary school students. The process of constructing a model solar building includes consideration of many fundamental scientific principles, such as the nature of heat, light, electricity, and energy conversion technology. When the model solar building is completed, there are numerous possibilities for the use of…

Examination of Solar Cycle Statistical Model and New Prediction of Solar Cycle 23

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; Wilson, John W.

2000-01-01

Sunspot numbers in the current solar cycle 23 were estimated by using a statistical model with the accumulating cycle sunspot data based on the odd-even behavior of historical sunspot cycles from 1 to 22. Since cycle 23 has progressed and the accurate solar minimum occurrence has been defined, the statistical model is validated by comparing the previous prediction with the new measured sunspot number; the improved sunspot projection in short range of future time is made accordingly. The current cycle is expected to have a moderate level of activity. Errors of this model are shown to be self-correcting as cycle observations become available.

Variation of the Mn I 539.4 nm line with the solar cycle

NASA Astrophysics Data System (ADS)

Danilovic, S.; Solanki, S. K.; Livingston, W.; Krivova, N.; Vince, I.

2016-03-01

Context. As a part of the long-term program at Kitt Peak National Observatory (KPNO), the Mn I 539.4 nm line has been observed for nearly three solar cycles using the McMath telescope and the 13.5 m spectrograph in double-pass mode. These full-disk spectrophotometric observations revealed an unusually strong change of this line's parameters over the solar cycle. Aims: Optical pumping by the Mg II k line was originally proposed to explain these variations. More recent studies have proposed that this is not required and that the magnetic variability (I.e., the changes in solar atmospheric structure due to faculae) might explain these changes. Magnetic variability is also the mechanism that drives the changes in total solar irradiance variations (TSI). With this work we investigate this proposition quantitatively by using the same model that was earlier successfully employed to reconstruct the irradiance. Methods: We reconstructed the changes in the line parameters using the model SATIRE-S, which takes only variations of the daily surface distribution of the magnetic field into account. We applied exactly the same model atmospheres and value of the free parameter as were used in previous solar irradiance reconstructions to now model the variation in the Mn I 539.4 nm line profile and in neighboring Fe I lines. We compared the results of the theoretical model with KPNO observations. Results: The changes in the Mn I 539.4 nm line and a neighbouring Fe I 539.52 nm line over approximately three solar cycles are reproduced well by the model without additionally tweaking the model parameters, if changes made to the instrument setup are taken into account. The model slightly overestimates the change for the strong Fe I 539.32 nm line. Conclusions: Our result confirms that optical pumping of the Mn II 539.4 nm line by Mg II k is not the main cause of its solar cycle change. It also provides independent confirmation of solar irradiance models which are based on the assumption that irradiance variations are caused by the evolution of the solar surface magnetic flux. The result obtained here also supports the spectral irradiance variations computed by these models.

Implementation of a subcanopy solar radiation model on a forested headwater basin in the Southern Appalachians to estimate riparian canopy density and stream insolation for stream temperature models

NASA Astrophysics Data System (ADS)

Belica, L.; Petras, V.; Iiames, J. S., Jr.; Caldwell, P.; Mitasova, H.; Nelson, S. A. C.

2016-12-01

Water temperature is a key aspect of water quality and understanding how the thermal regimes of forested headwater streams may change in response to climatic and land cover changes is increasingly important to scientists and resource managers. In recent years, the forested mountain watersheds of the Southeastern U.S. have experienced changing climatic patterns as well as the loss of a keystone riparian tree species and anticipated hydrologic responses include lower summer stream flows and decreased stream shading. Solar radiation is the main source of thermal energy to streams and a key parameter in heat-budget models of stream temperature; a decrease in flow volume combined with a reduction in stream shading during summer have the potential to increase stream temperatures. The high spatial variability of forest canopies and the high spatio-temporal variability in sky conditions make estimating the solar radiation reaching small forested headwater streams difficult. The Subcanopy Solar Radiation Model (SSR) (Bode et al. 2014) is a GIS model that generates high resolution, spatially explicit estimates of solar radiation by incorporating topographic and vegetative shading with a light penetration index derived from leaf-on airborne LIDAR data. To evaluate the potential of the SSR model to provide estimates of stream insolation to parameterize heat-budget models, it was applied to the Coweeta Basin in the Southern Appalachians using airborne LIDAR (NCALM 2009, 1m resolution). The LIDAR derived canopy characteristics were compared to current hyperspectral images of the canopy for changes and the SSR estimates of solar radiation were compared with pyranometer measurements of solar radiation at several subcanopy sites during the summer of 2016. Preliminary results indicate the SSR model was effective in identifying variations in canopy density and light penetration, especially in areas associated with road and stream corridors and tree mortality. Current LIDAR data and more solar radiation measurements are needed to fully validate the accuracy of the SSR model in Southern Appalachian forests, but initial results suggest the high resolution, spatially explicit estimates of solar radiation can improve solar radiation parameter estimates in deterministic models of stream temperature in forested landscapes.

Effects of Mg II and Ca II ionization on ab-initio solar chromosphere models

NASA Technical Reports Server (NTRS)

Rammacher, W.; Cuntz, M.

1991-01-01

Acoustically heated solar chromosphere models are computed considering radiation damping by (non-LTE) emission from H(-) and by Mg II and Ca II emission lines. The radiative transfer equations for the Mg II k and Ca II K emission lines are solved using the core-saturation method with complete redistribution. The Mg II k and Ca II K cooling rates are compared with the VAL model C. Several substantial improvements over the work of Ulmschneider et al. (1987) are included. It is found that the rapid temperature rises caused by the ionization of Mg II are not formed in the middle chromosphere, but occur at larger atmospheric heights. These models represent the temperature structure of the 'real' solar chromosphere much better. This result is a major precondition for the study of ab-initio models for solar flux tubes based on MHD wave propagation and also for ab-initio models for the solar transition layer.

Fast All-Sky Radiation Model for Solar Applications (FARMS): A Brief Overview of Mechanisms, Performance, and Applications: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Yu; Sengupta, Manajit

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 RRTMmore » 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.« less

Slow Solar Wind: Observations and Modeling

NASA Technical Reports Server (NTRS)

Abbo, L.; Ofman, L.; Antiochos, S. K.; Hansteen, V. H.; Harra, L.; Ko, Y.-K.; Lapenta, G.; Li, B.; Riley, P.; Strachan, L.;

A Model of Magnetic Braking of Solar Rotation that Satisfies Observational Constraints

NASA Astrophysics Data System (ADS)

Denissenkov, Pavel A.

2010-08-01

The model of magnetic braking of solar rotation considered by Charbonneau & MacGregor has been modified so that it is able to reproduce for the first time the rotational evolution of both the fastest and slowest rotators among solar-type stars in open clusters of different ages, without coming into conflict with other observational constraints, such as the time evolution of the atmospheric Li abundance in solar twins and the thinness of the solar tachocline. This new model assumes that rotation-driven turbulent diffusion, which is thought to amplify the viscosity and magnetic diffusivity in stellar radiative zones, is strongly anisotropic with the horizontal components of the transport coefficients strongly dominating over those in the vertical direction. Also taken into account is the poloidal field decay that helps to confine the width of the tachocline at the solar age. The model's properties are investigated by numerically solving the azimuthal components of the coupled momentum and magnetic induction equations in two dimensions using a finite element method.

Periodic orbits of solar sail equipped with reflectance control device in Earth-Moon system

NASA Astrophysics Data System (ADS)

Yuan, Jianping; Gao, Chen; Zhang, Junhua

2018-02-01

In this paper, families of Lyapunov and halo orbits are presented with a solar sail equipped with a reflectance control device in the Earth-Moon system. System dynamical model is established considering solar sail acceleration, and four solar sail steering laws and two initial Sun-sail configurations are introduced. The initial natural periodic orbits with suitable periods are firstly identified. Subsequently, families of solar sail Lyapunov and halo orbits around the L1 and L2 points are designed with fixed solar sail characteristic acceleration and varying reflectivity rate and pitching angle by the combination of the modified differential correction method and continuation approach. The linear stabilities of solar sail periodic orbits are investigated, and a nonlinear sliding model controller is designed for station keeping. In addition, orbit transfer between the same family of solar sail orbits is investigated preliminarily to showcase reflectance control device solar sail maneuver capability.

A generalized analysis of solar space heating

NASA Astrophysics Data System (ADS)

Clark, J. A.

A life-cycle model is developed for solar space heating within the United States. The model consists of an analytical relationship among five dimensionless parameters that include all pertinent technical, climatological, solar, operating and economic factors that influence the performance of a solar space heating system. An important optimum condition presented is the break-even metered cost of conventional fuel at which the cost of the solar system is equal to that of a conventional heating system. The effect of Federal (1980) and State (1979) income tax credits on these costs is determined. A parameter that includes both solar availability and solar system utilization is derived and plotted on a map of the U.S. This parameter shows the most favorable present locations for solar space heating application to be in the Central and Mountain States. The data employed are related to the rehabilitated solar data recently made available by the National Climatic Center.

Comparison of modeled and typical meteorological year. Diffuse, direct, and tilted solar radiation values with measured data in a cloudy climate: Seattle-Tacoma data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Straub, D.; Baylon, D.; Smith, O.

1980-01-01

Four commonly used solar radiation models that determine the diffuse and direct components of the solar radiation on a horizontal surface are compared against measured data to determine their predictive and modeling applicability. The John Hay model is determined to underpredict the diffuse and the Pereira/Rabl model to overpredict the diffuse radiation. The daily Liu and Jordan correlation and the hourly Boes correlation are shown to be better predictors.

Project for Solar-Terrestrial Environment Prediction (PSTEP): Towards Predicting Next Solar Cycle

NASA Astrophysics Data System (ADS)

Imada, S.; Iijima, H.; Hotta, H.; Shiota, D.; Kanou, O.; Fujiyama, M.; Kusano, K.

2016-10-01

It is believed that the longer-term variations of the solar activity can affect the Earth's climate. Therefore, predicting the next solar cycle is crucial for the forecast of the "solar-terrestrial environment". To build prediction schemes for the activity level of the next solar cycle is a key for the long-term space weather study. Although three-years prediction can be almost achieved, the prediction of next solar cycle is very limited, so far. We are developing a five-years prediction scheme by combining the Surface Flux Transport (SFT) model and the most accurate measurements of solar magnetic fields as a part of the PSTEP (Project for Solar-Terrestrial Environment Prediction),. We estimate the meridional flow, differential rotation, and turbulent diffusivity from recent modern observations (Hinode and Solar Dynamics Observatory). These parameters are used in the SFT models to predict the polar magnetic fields strength at the solar minimum. In this presentation, we will explain the outline of our strategy to predict the next solar cycle. We also report the present status and the future perspective of our project.

Solar cell options based on different geographical locations and wall inclination

NASA Astrophysics Data System (ADS)

Ma, Jie

2018-05-01

Two major trends in the development of contemporary solar energy science and technology [1]: First, the combination of light and point, the second is the combination of solar energy and construction. A large number of houses at the top of the installation of solar water heaters and other primary solar energy utilization equipment can no longer meet the needs of the majority of users, people pay more attention to the ventilation and heating of housing and solar power supply and other integrated multi-purpose building construction. Under the condition of simplification, this model gives the options of laying suitable solar cells for houses with different geographical positions and different inclination angles according to the actual situation. Based on our model, firstly we calculate the wall radiation according to the model (WRCM) to get the light radiation of the wall of the house, and then according to the power generation model (PGM), we can calculate the output of several types of batteries in the selected range. Finally, through the economic benefits mode l (EBM), we get the economic benefits of each type of battery in different places, and then we can choose the most suitable battery type. At the end of the article, we take Datong, Shanxi Province as an example, and substitute the relevant data from online search into the model. Compared with the actual situation, we verify that the model has good applicability.

Diffusion of solar energy technologies in the new-construction market: A survey of new solar-home and conventional-home buyers

NASA Astrophysics Data System (ADS)

Rains, D.; Dunipace, D.; Woo, C. K.

1981-02-01

Consumer motivations for choosing a solar energy equipped home when the nonsolar or conventional model was available were investigated. The approach was to test the relative importance of demographic, dwelling unit, and heating system characteristics in household decisions to purchase a home equipped with solar energy devices. Two statistical models were developed: one to examine the relationship between the types of home buyers (as an identifiable market segment) and the decision to purchase a solar home; and the other to compare the energy use of solar vs. conventional homes selected in the sample.

Forecast of solar wind parameters according to STOP magnetograph observations

NASA Astrophysics Data System (ADS)

Tlatov, A. G.; Pashchenko, M. P.; Ponyavin, D. I.; Svidskii, P. M.; Peshcherov, V. S.; Demidov, M. L.

2016-12-01

The paper discusses the results of the forecast of solar wind parameters at a distance of 1 AU made according to observations made by the STOP telescope magnetograph during 2014-2015. The Wang-Sheeley-Arge (WSA) empirical model is used to reconstruct the magnetic field topology in the solar corona and estimate the solar wind speed in the interplanetary medium. The proposed model is adapted to STOP magnetograph observations. The results of the calculation of solar wind parameters are compared with ACE satellite measurements. It is shown that the use of STOP observations provides a significant correlation of predicted solar wind speed values with the observed ones.

Solar Spectral Irradiance Variability in Cycle 24: Model Predictions and OMI Observations

NASA Technical Reports Server (NTRS)

Marchenko, S.; DeLand, M.; Lean, J.

2016-01-01

Utilizing the excellent stability of the Ozone Monitoring Instrument (OMI), we characterize both short-term (solar rotation) and long-term (solar cycle) changes of the solar spectral irradiance (SSI) between 265-500 nanometers during the ongoing Cycle 24. We supplement the OMI data with concurrent observations from the GOME-2 (Global Ozone Monitoring Experiment - 2) and SORCE (Solar Radiation and Climate Experiment) instruments and find fair-to-excellent agreement between the observations and predictions of the NRLSSI2 (Naval Research Laboratory Solar Spectral Irradiance - post SORCE) and SATIRE-S (the Naval Research Laboratory's Spectral And Total Irradiance REconstruction for the Satellite era) models.

Preliminary survey on site-adaptation techniques for satellite-derived and reanalysis solar radiation datasets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Polo, J.; Wilbert, S.; Ruiz-Arias, J. A.

2016-07-01

At any site, the bankability of a projected solar power plant largely depends on the accuracy and general quality of the solar radiation data generated during the solar resource assessment phase. The term 'site adaptation' has recently started to be used in the framework of solar energy projects to refer to the improvement that can be achieved in satellite-derived solar irradiance and model data when short-term local ground measurements are used to correct systematic errors and bias in the original dataset. This contribution presents a preliminary survey of different possible techniques that can improve long-term satellite-derived and model-derived solar radiationmore » data through the use of short-term on-site ground measurements. The possible approaches that are reported here may be applied in different ways, depending on the origin and characteristics of the uncertainties in the modeled data. This work, which is the first step of a forthcoming in-depth assessment of methodologies for site adaptation, has been done within the framework of the International Energy Agency Solar Heating and Cooling Programme Task 46 'Solar Resource Assessment and Forecasting.'« less

Interplanetary Radiation and Internal Charging Environment Models for Solar Sails

NASA Technical Reports Server (NTRS)

Minow, Joseph I.; Altstatt, Richard L.; Neergaard, Linda F.

2004-01-01

A Solar Sail Radiation Environment (SSRE) model has been developed for characterizing the radiation dose and internal charging environments in the solar wind. The SSRE model defines the 0.01 keV to 1 MeV charged particle environment for use in testing the radiation dose vulnerability of candidate solar sail materials and for use in evaluating the internal charging effects in the interplanetary environment. Solar wind and energetic particle instruments aboard the Ulysses spacecraft provide the particle data used to derive the environments for the high inclination 0.5 AU Solar Polar Imager mission and the 1.0 AU L1 solar sail missions. Ulysses is the only spacecraft to sample high latitude solar wind environments far from the ecliptic plane and is therefore uniquely capable of providing the information necessary for defining radiation environments for the Solar Polar Imager spacecraft. Cold plasma moments are used to derive differential flux spectra based on Kappa distribution functions. Energetic particle flux measurements are used to constrain the high energy, non-thermal tails of the distribution functions providing a comprehensive electron, proton, and helium spectra from less than 0.01 keV to a few MeV.

Testing and optical modeling of novel concentrating solar receiver geometries to increase light trapping and effective solar absorptance

NASA Astrophysics Data System (ADS)

Yellowhair, Julius; Ho, Clifford K.; Ortega, Jesus D.; Christian, Joshua M.; Andraka, Charles E.

2015-09-01

Concentrating solar power receivers are comprised of panels of tubes arranged in a cylindrical or cubical shape on top of a tower. The tubes contain heat-transfer fluid that absorbs energy from the concentrated sunlight incident on the tubes. To increase the solar absorptance, black paint or a solar selective coating is applied to the surface of the tubes. However, these coatings degrade over time and must be reapplied, which reduces the system performance and increases costs. This paper presents an evaluation of novel receiver shapes and geometries that create a light-trapping effect, thereby increasing the effective solar absorptance and efficiency of the solar receiver. Several prototype shapes were fabricated from Inconel 718 and tested in Sandia's solar furnace at an irradiance of ~30 W/cm2. Photographic methods were used to capture the irradiance distribution on the receiver surfaces. The irradiance profiles were compared to results from raytracing models. The effective solar absorptance was also evaluated using the ray-tracing models. Results showed that relative to a flat plate, the new geometries could increase the effective solar absorptance from 86% to 92% for an intrinsic material absorptance of 86%, and from 60% to 73% for an intrinsic material absorptance of 60%.

Solar measurements from the Airglow-Solar Spectrometer Instrument (ASSI) on the San Marco 5 satellite

NASA Technical Reports Server (NTRS)

Woods, Thomas N.

1994-01-01

The analysis of the solar spectral irradiance from the Airglow-Solar Spectrometer Instrument (ASSI) on the San Marco 5 satellite is the focus for this research grant. A pre-print copy of the paper describing the calibrations of and results from the San Marco ASSI is attached to this report. The calibration of the ASSI included (1) transfer of photometric calibration from a rocket experiment and the Solar Mesosphere Explorer (SME), (2) use of the on-board radioactive calibration sources, (3) validation of the ASSI sensitivity over its field of view, and (4) determining the degradation of the spectrometers. We have determined that the absolute values for the solar irradiance needs adjustment in the current proxy models of the solar UV irradiance, and the amount of solar variability from the proxy models are in reasonable agreement with the ASSI measurements. This research grant also has supported the development of a new solar EUV irradiance proxy model. We expected that the magnetic flux is responsible for most of the heating, via Alfen waves, in the chromosphere, transition region, and corona. From examining time series of solar irradiance data and magnetic fields at different levels, we did indeed find that the chromospheric emissions correlate best with the large magnetic field levels.

Assessment of global solar radiation to examine the best locations to install a PV system in Tunisia

NASA Astrophysics Data System (ADS)

Belkilani, Kaouther; Ben Othman, Afef; Besbes, Mongi

2018-02-01

The study of the solar radiation is the starting point of any investigation for a new energy, to study and search the best location to install a PV system. A very important factor in the assessment of solar potential is the availability of data for global solar radiation that must be coherent and of high quality. In this paper, we analyze the estimation result of the monthly global solar radiation for three different locations, Bizerte in Northern Tunisia, Kairouan in Middle Eastern Tunisia, and Tozeur in Southern Tunisia, measured on the surface by the National Institute of Meteorology and the meteorological year irradiation based on satellite imagery result PVGIS radiation databases. To get the right measurements with minimum error, we propose a numerical model used to calculate the global solar radiation in the indicated three sites. The results show that the model can estimate the global solar radiation (kWh/m²) at a specific station and over most area of Tunisia. The model gives a good estimation for solar radiation where error between the measured values and those calculated are negligible.

Comparisons of Measurements and Modeling of Solar Eclipse Effects on VLF Transmissions

NASA Astrophysics Data System (ADS)

Eccles, J. V.; Rice, D. D.; Sojka, J. J.; Marshall, R. A.; Drob, D. P.; Decena, J. C.

2017-12-01

The solar eclipse of 2017 August 21 provides an excellent opportunity to examine Very Low Frequency (VLF) radio signal propagation through the path of the solar eclipse between Navy VLF transmitters and several VLF receivers. The VLF transmitters available for this study radio signal propagation study are NLK in Jim Creek, Washington (24.8 kHz, 192 kW, 48.20N, 121.90W), NML in LaMour, North Dakota (25.2 kHz, 500 kW 46.37N, 93.34W), and NAA in Cutler, Maine (24.0 kHz, 1000 kW, 44.65N, 67.29W). These VLF transmitters provide propagation paths to three VLF receivers at Utah State University (41.75N, 111.76W), Bear Lake Observatory (41.95N, 111.39W), Salt Lake City (40.76N, 111.89W) and one receiver in Boulder, Colorado (40.02N, 105.27W). The solar eclipse shadow will cross all propagations paths during the day and will modify the D region electron density within the solar shadow. The week prior to the solar eclipse will be used to generate a diurnal baseline of VLF single strength for each transmitter-receiver pair. These will be compared to the day of the solar eclipse to identify VLF propagation differences through the solar eclipse shawdow. Additionally, the electron density effects of the week prior and of the solar eclipse day will be modeled using the Data-Driven D Region (DDDR) model [Eccles et al., 2005] with a detailed eclipse solar flux mask. The Long-Wave Propagation Code and the HASEL RF ray-tracing code will be used to generate VLF signal strength for each measured propagation path through the days prior and the solar eclipse day. Model-measurement comparisons will be presented and the D region electron density effects of the solar eclipse will be examined. The DDDR is a time-dependent D region model, which makes it very suitable for the solar eclipse effects on the electron density for the altitude range of 36 to 130 km. Eccles J. V., R. D. Hunsucker, D. Rice, J. J. Sojka (2005), Space weather effects on midlatitude HF propagation paths: Observations and a data-driven D region model, Space Weather, 3, S01002, doi:10.1029/2004SW000094.

Multifractal two-scale Cantor set model for slow solar wind turbulence in the outer heliosphere during solar maximum

NASA Astrophysics Data System (ADS)

Macek, W. M.; Wawrzaszek, A.

2011-05-01

To quantify solar wind turbulence, we consider a generalized two-scale weighted Cantor set with two different scales describing nonuniform distribution of the kinetic energy flux between cascading eddies of various sizes. We examine generalized dimensions and the corresponding multifractal singularity spectrum depending on one probability measure parameter and two rescaling parameters. In particular, we analyse time series of velocities of the slow speed streams of the solar wind measured in situ by Voyager 2 spacecraft in the outer heliosphere during solar maximum at various distances from the Sun: 10, 30, and 65 AU. This allows us to look at the evolution of multifractal intermittent scaling of the solar wind in the distant heliosphere. Namely, it appears that while the degree of multifractality for the solar wind during solar maximum is only weakly correlated with the heliospheric distance, but the multifractal spectrum could substantially be asymmetric in a very distant heliosphere beyond the planetary orbits. Therefore, one could expect that this scaling near the frontiers of the heliosphere should rather be asymmetric. It is worth noting that for the model with two different scaling parameters a better agreement with the solar wind data is obtained, especially for the negative index of the generalized dimensions. Therefore we argue that there is a need to use a two-scale cascade model. Hence we propose this model as a useful tool for analysis of intermittent turbulence in various environments and we hope that our general asymmetric multifractal model could shed more light on the nature of turbulence.

Parametric analysis of ATM solar array.

NASA Technical Reports Server (NTRS)

Singh, B. K.; Adkisson, W. B.

1973-01-01

The paper discusses the methods used for the calculation of ATM solar array performance characteristics and provides the parametric analysis of solar panels used in SKYLAB. To predict the solar array performance under conditions other than test conditions, a mathematical model has been developed. Four computer programs have been used to convert the solar simulator test data to the parametric curves. The first performs module summations, the second determines average solar cell characteristics which will cause a mathematical model to generate a curve matching the test data, the third is a polynomial fit program which determines the polynomial equations for the solar cell characteristics versus temperature, and the fourth program uses the polynomial coefficients generated by the polynomial curve fit program to generate the parametric data.

The Flare Irradiance Spectral Model (FISM) and its Contributions to Space Weather Research, the Flare Energy Budget, and Instrument Design

NASA Technical Reports Server (NTRS)

Chamberlin, Phillip

2008-01-01

The Flare Irradiance Spectral Model (FISM) is an empirical model of the solar irradiance spectrum from 0.1 to 190 nm at 1 nm spectral resolution and on a 1-minute time cadence. The goal of FISM is to provide accurate solar spectral irradiances over the vacuum ultraviolet (VUV: 0-200 nm) range as input for ionospheric and thermospheric models. The seminar will begin with a brief overview of the FISM model, and also how the Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) will contribute to improving FISM. Some current studies will then be presented that use FISM estimations of the solar VUV irradiance to quantify the contributions of the increased irradiance from flares to Earth's increased thermospheric and ionospheric densites. Initial results will also be presented from a study looking at the electron density increases in the Martian atmosphere during a solar flare. Results will also be shown quantifying the VUV contributions to the total flare energy budget for both the impulsive and gradual phases of solar flares. Lastly, an example of how FISM can be used to simplify the design of future solar VUV irradiance instruments will be discussed, using the future NOAA GOES-R Extreme Ultraviolet and X-Ray Sensors (EXIS) space weather instrument.

Urban UV environment in a sub-tropical megacity - A measurement and modelling study

NASA Astrophysics Data System (ADS)

Wai, Ka-Ming; Yu, Peter K. N.; Chan, Pok-Man

The variations of solar total UV (UVA + UVB) exposure rates in a megacity featured with high-rise buildings during summer months were measured and relevant model predictions were evaluated. The maximum pedestrian-level total solar UV exposure rate was less than the un-obstructed exposure rate at any time, attributing to the prevailing reduction in the diffuse solar radiation due to the obstruction effects of distant buildings. Comparing with the measurements, our coupled model well captured the spatial and temporal variations of the reduction of UV exposure rates. By measurements, large reduction in the solar total UV exposure rate down to 12% of un-obstructed exposure rate due to the building obstruction effects was found, agreeing with our previous simulation results and results from an Australian megacity. On the other hand, building reflection from reflective curtain walls could reach 23% of the un-obstructed solar total UV exposure rate at the ground level. This implied improper building design creating additional harmful effects of solar UV radiation on the environment. The coupled model was also applied to predict the urban UV exposure rates during a tropical-cyclone induced aerosol episode. A well-evaluated urban solar UV model is an important tool for sustainable urban design.

On the applications of nanofluids to enhance the performance of solar collectors: A comparative analysis of Atangana-Baleanu and Caputo-Fabrizio fractional models

NASA Astrophysics Data System (ADS)

Sheikh, Nadeem Ahmad; Ali, Farhad; Khan, Ilyas; Gohar, Madeha; Saqib, Muhammad

2017-12-01

In the modern era, solar energy has gained the consideration of researchers to a great deal. Apparently, the reasons are twofold: firstly, the researchers are concerned to design new devices like solar collectors, solar water heaters, etc. Secondly, the use of new approaches to improve the performance of solar energy equipment. The aim of this paper is to model the problem of the enhancement of heat transfer rate of solar energy devices, using nanoparticles and to find the exact solutions of the considered problem. The classical model is transformed to a generalized model using two different types of time-fractional derivatives, namely the Caputo-Fabrizio and Atangana-Baleanu derivatives and their comparative analysis has been presented. The solutions for the flow profile and heat transfer are presented using the Laplace transform method. The variation in the heat transfer rate has been observed for different nanoparticles and their different volume fractions. Theoretical results show that by adding aluminum oxide nanoparticles, the efficiency of solar collectors may be enhanced by 5.2%. Furthermore, the effect of volume friction of nanoparticles on velocity distribution has been discussed in graphical illustrations. The solutions are reduced to the corresponding classical model of nanofluid.

Estimation of Solar Radiation on Building Roofs in Mountainous Areas

NASA Astrophysics Data System (ADS)

Agugiaro, G.; Remondino, F.; Stevanato, G.; De Filippi, R.; Furlanello, C.

2011-04-01

The aim of this study is estimating solar radiation on building roofs in complex mountain landscape areas. A multi-scale solar radiation estimation methodology is proposed that combines 3D data ranging from regional scale to the architectural one. Both the terrain and the nearby building shadowing effects are considered. The approach is modular and several alternative roof models, obtained by surveying and modelling techniques at varying level of detail, can be embedded in a DTM, e.g. that of an Alpine valley surrounded by mountains. The solar radiation maps obtained from raster models at different resolutions are compared and evaluated in order to obtain information regarding the benefits and disadvantages tied to each roof modelling approach. The solar radiation estimation is performed within the open-source GRASS GIS environment using r.sun and its ancillary modules.

Experimental and Numerical Correlation of Gravity Sag in Solar Sail Quality Membranes

NASA Technical Reports Server (NTRS)

Black, Jonathan T.; Leifer, Jack; DeMoss, Joshua A.; Walker, Eric N.; Belvin, W. Keith

2004-01-01

Solar sails are among the most studied members of the ultra-lightweight and inflatable (Gossamer) space structures family due to their potential to provide propellentless propulsion. They are comprised of ultra-thin membrane panels that, to date, have proven very difficult to experimentally characterize and numerically model due to their reflectivity and flexibility, and the effects of gravity sag and air damping. Numerical models must be correlated with experimental measurements of sub-scale solar sails to verify that the models can be scaled up to represent full-sized solar sails. In this paper, the surface shapes of five horizontally supported 25 micron thick aluminized Kapton membranes were measured to a 1.0 mm resolution using photogrammetry. Several simple numerical models closely match the experimental data, proving the ability of finite element simulations to predict actual behavior of solar sails.

Middle Atmosphere Response to Different Descriptions of the 11-Year Solar Cycle in Spectral Irradiance in a Chemistry-Climate Model

NASA Technical Reports Server (NTRS)

Swartz, W. H.; Stolarski, R. S.; Oman, L. D.; Fleming, E. L.; Jackman, C. H.

2012-01-01

The 11-year solar cycle in solar spectral irradiance (SSI) inferred from measurements by the SOlar Radiation & Climate Experiment (SORCE) suggests a much larger variation in the ultraviolet than previously accepted. We present middle atmosphere ozone and temperature responses to the solar cycles in SORCE SSI and the ubiquitous Naval Research Laboratory (NRL) SSI reconstruction using the Goddard Earth Observing System chemistry-climate model (GEOS CCM). The results are largely consistent with other recent modeling studies. The modeled ozone response is positive throughout the stratosphere and lower mesosphere using the NRL SSI, while the SORCE SSI produces a response that is larger in the lower stratosphere but out of phase with respect to total solar irradiance above 45 km. The modeled responses in total ozone are similar to those derived from satellite and ground-based measurements, 3-6 Dobson Units per 100 units of 10.7-cm radio flux (F10.7) in the tropics. The peak zonal mean tropical temperature response 50 using the SORCE SSI is nearly 2 K per 100 units 3 times larger than the simulation using the NRL SSI. The GEOS CCM and the Goddard Space Flight Center (GSFC) 2-D coupled model are used to examine how the SSI solar cycle affects the atmosphere through direct solar heating and photolysis processes individually. Middle atmosphere ozone is affected almost entirely through photolysis, whereas the solar cycle in temperature is caused both through direct heating and photolysis feedbacks, processes that are mostly linearly separable. Further, the net ozone response results from the balance of ozone production at wavelengths less than 242 nm and destruction at longer wavelengths, coincidentally corresponding to the wavelength regimes of the SOLar STellar Irradiance Comparison Experiment (SOLSTICE) and Spectral Irradiance Monitor (SIM) on SORCE, respectively. A higher wavelength-resolution analysis of the spectral response could allow for a better prediction of the atmospheric response to arbitrary SSI variations.

The Distribution of Solar Wind Speeds During Solar Minimum: Calibration for Numerical Solar Wind Modeling Constraints on the Source of the Slow Solar Wind (Postprint)

DTIC Science & Technology

2012-03-05

subsonic corona below the critical point, resulting in an increased scale height and mass flux, while keeping the kinetic energy of the flow fairly...Approved for public release; distribution is unlimited. tubes with small expansion factors the heating occurs in the supersonic corona, where the energy ...goes into the kinetic energy of the solar wind, increasing the flow speed [Leer and Holzer, 1980; Pneuman, 1980]. Using this model and a sim- plified

Univariate Time Series Prediction of Solar Power Using a Hybrid Wavelet-ARMA-NARX Prediction Method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nazaripouya, Hamidreza; Wang, Yubo; Chu, Chi-Cheng

This paper proposes a new hybrid method for super short-term solar power prediction. Solar output power usually has a complex, nonstationary, and nonlinear characteristic due to intermittent and time varying behavior of solar radiance. In addition, solar power dynamics is fast and is inertia less. An accurate super short-time prediction is required to compensate for the fluctuations and reduce the impact of solar power penetration on the power system. The objective is to predict one step-ahead solar power generation based only on historical solar power time series data. The proposed method incorporates discrete wavelet transform (DWT), Auto-Regressive Moving Average (ARMA)more » models, and Recurrent Neural Networks (RNN), while the RNN architecture is based on Nonlinear Auto-Regressive models with eXogenous inputs (NARX). The wavelet transform is utilized to decompose the solar power time series into a set of richer-behaved forming series for prediction. ARMA model is employed as a linear predictor while NARX is used as a nonlinear pattern recognition tool to estimate and compensate the error of wavelet-ARMA prediction. The proposed method is applied to the data captured from UCLA solar PV panels and the results are compared with some of the common and most recent solar power prediction methods. The results validate the effectiveness of the proposed approach and show a considerable improvement in the prediction precision.« less

Development, Production and Validation of the NOAA Solar Irradiance Climate Data Record

NASA Astrophysics Data System (ADS)

Coddington, O.; Lean, J.; Pilewskie, P.; Snow, M. A.; Lindholm, D. M.

2015-12-01

A new climate data record of Total Solar Irradiance (TSI) and Solar Spectral Irradiance (SSI), including source code and supporting documentation is now publicly available as part of the National Oceanographic and Atmospheric Administration's (NOAA) National Centers for Environmental Information (NCEI) Climate Data Record (CDR) Program. Daily and monthly averaged values of TSI and SSI, with associated time and wavelength dependent uncertainties, are estimated from 1882 to the present with yearly averaged values since 1610, updated quarterly for the foreseeable future. The new Solar Irradiance Climate Data Record, jointly developed by the University of Colorado at Boulder's Laboratory for Atmospheric and Space Physics (LASP) and the Naval Research Laboratory (NRL), is constructed from solar irradiance models that determine the changes from quiet Sun conditions when bright faculae and dark sunspots are present on the solar disk. The magnitudes of the irradiance changes that these features produce are determined from linear regression of the proxy Mg II index and sunspot area indices against the approximately decade-long solar irradiance measurements made by instruments on the SOlar Radiation and Climate Experiment (SORCE) spacecraft. We describe the model formulation, uncertainty estimates, operational implementation and validation approach. Future efforts to improve the uncertainty estimates of the Solar Irradiance CDR arising from model assumptions, and augmentation of the solar irradiance reconstructions with direct measurements from the Total and Spectral Solar Irradiance Sensor (TSIS: launch date, July 2017) are also discussed.

Solar Sail Models and Test Measurements Correspondence for Validation Requirements Definition

NASA Technical Reports Server (NTRS)

Ewing, Anthony; Adams, Charles

2004-01-01

Solar sails are being developed as a mission-enabling technology in support of future NASA science missions. Current efforts have advanced solar sail technology sufficient to justify a flight validation program. A primary objective of this activity is to test and validate solar sail models that are currently under development so that they may be used with confidence in future science mission development (e.g., scalable to larger sails). Both system and model validation requirements must be defined early in the program to guide design cycles and to ensure that relevant and sufficient test data will be obtained to conduct model validation to the level required. A process of model identification, model input/output documentation, model sensitivity analyses, and test measurement correspondence is required so that decisions can be made to satisfy validation requirements within program constraints.

Projections of long-term changes in solar radiation based on CMIP5 climate models and their influence on energy yields of photovoltaic systems

NASA Astrophysics Data System (ADS)

Wild, Martin; Folini, Doris; Henschel, Florian; Müller, Björn

2015-04-01

Traditionally, for the planning and assessment of solar energy systems, the amount of solar radiation (sunlight) incident on the Earth's surface is assumed to be constant over the years. However, with changing climate and air pollution levels, solar resources may no longer be stable over time and undergo substantial decadal changes. Observational records covering the past decades confirm long-term changes in this quantity. Here we examine, how the latest generation of climate models used for the 5th IPCC report projects potential changes in surface solar radiation over the coming decades, and how this may affect, in combination with the expected greenhouse warming, solar power output from photovoltaic (PV) systems. For this purpose, projections up to the mid 21th century from 39 state of the art climate models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) are analysed globally and for selected key regions with major solar power production capacity. The large model ensemble allows to assess the degree of consistency of their projections. Models are largely consistent in the sign of the projected changes in solar radiation under cloud-free conditions as well as in surface temperatures over most of the globe, while still reasonably consistent over a considerable part of the globe in the sign of changes in cloudiness and associated changes in solar radiation. A first order estimate of the impact of solar radiation and temperature changes on energy yields of PV systems under the RPC8.5 scenario indicates statistically significant decreases in PV outputs in large parts of the world, but notable exceptions with positive trends in parts of Europe and the South-East of China. Projected changes between 2006 and 2049 under the RCP8.5 scenario overall are on the order of 1 % per decade for horizontal planes, but may be larger for tilted or tracked planes as well as on shorter (decadal) timescales. Related References: Wild, M., Folini, D., Henschel, F., and Müller, B. 2015: Projections of long-term changes in solar radiation based on CMIP5 climate models and their influence on energy yields of photovoltaic systems, submitted. Muller, B., Wild, M., Driesse, A., and Behrens, K., 2014: Rethinking solar resource assessments in the context of global dimming and brightening, Solar Energy, 99, 272-282. Wild, M. 2012: Enlightening Global Dimming and Brightening. Bull. Amer. Meteor. Soc., 93, 27-37, doi:10.1175/BAMS-D-11-00074.1

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Shaughnessy, Eric; Ardani, Kristen; Cutler, Dylan

Solar 'plus' refers to an emerging approach to distributed solar photovoltaic (PV) deployment that uses energy storage and controllable devices to optimize customer economics. The solar plus approach increases customer system value through technologies such as electric batteries, smart domestic water heaters, smart air-conditioner (AC) units, and electric vehicles We use an NREL optimization model to explore the customer-side economics of solar plus under various utility rate structures and net metering rates. We explore optimal solar plus applications in five case studies with different net metering rates and rate structures. The model deploys different configurations of PV, batteries, smart domesticmore » water heaters, and smart AC units in response to different rate structures and customer load profiles. The results indicate that solar plus improves the customer economics of PV and may mitigate some of the negative impacts of evolving rate structures on PV economics. Solar plus may become an increasingly viable model for optimizing PV customer economics in an evolving rate environment.« less

Response of Solar Irradiance to Sunspot-area Variations

NASA Astrophysics Data System (ADS)

Dudok de Wit, T.; Kopp, G.; Shapiro, A.; Witzke, V.; Kretzschmar, M.

2018-02-01

One of the important open questions in solar irradiance studies is whether long-term variability (i.e., on timescales of years and beyond) can be reconstructed by means of models that describe short-term variability (i.e., days) using solar proxies as inputs. Preminger & Walton showed that the relationship between spectral solar irradiance and proxies of magnetic-flux emergence, such as the daily sunspot area, can be described in the framework of linear system theory by means of the impulse response. We significantly refine that empirical model by removing spurious solar-rotational effects and by including an additional term that captures long-term variations. Our results show that long-term variability cannot be reconstructed from the short-term response of the spectral irradiance, which questions the extension of solar proxy models to these timescales. In addition, we find that the solar response is nonlinear in a way that cannot be corrected simply by applying a rescaling to a sunspot area.

Realistic Modeling of Multi-Scale MHD Dynamics of the Solar Atmosphere

NASA Technical Reports Server (NTRS)

Kitiashvili, Irina; Mansour, Nagi N.; Wray, Alan; Couvidat, Sebastian; Yoon, Seokkwan; Kosovichev, Alexander

2014-01-01

Realistic 3D radiative MHD simulations open new perspectives for understanding the turbulent dynamics of the solar surface, its coupling to the atmosphere, and the physical mechanisms of generation and transport of non-thermal energy. Traditionally, plasma eruptions and wave phenomena in the solar atmosphere are modeled by prescribing artificial driving mechanisms using magnetic or gas pressure forces that might arise from magnetic field emergence or reconnection instabilities. In contrast, our 'ab initio' simulations provide a realistic description of solar dynamics naturally driven by solar energy flow. By simulating the upper convection zone and the solar atmosphere, we can investigate in detail the physical processes of turbulent magnetoconvection, generation and amplification of magnetic fields, excitation of MHD waves, and plasma eruptions. We present recent simulation results of the multi-scale dynamics of quiet-Sun regions, and energetic effects in the atmosphere and compare with observations. For the comparisons we calculate synthetic spectro-polarimetric data to model observational data of SDO, Hinode, and New Solar Telescope.

Solar corona electron density distribution

NASA Astrophysics Data System (ADS)

Esposito, P. B.; Edenhofer, P.; Lueneburg, E.

1980-07-01

The paper discusses the three and one-half months of single-frequency time delay data which were acquired from the Helios 2 spacecraft around the time of its solar occultation. The excess time delay due to integrated effect of free electrons along the signal's ray path could be separated and modeled following the determination of the spacecraft trajectory. An average solar corona and equatorial electron density profile during solar minimum were deduced from the time delay measurements acquired within 5-60 solar radii of the sun. As a point of reference at 10 solar radii from the sun, an average electron density was 4500 el/cu cm. However, an asymmetry was found in the electron density as the ray path moved from the west to east solar limb. This may be related to the fact that during entry into occultation the heliographic latitude of the ray path was about 6 deg, while during exit it was 7 deg. The Helios density model is compared with similar models deduced from different experimental techniques.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michael, A. T.; Opher, M.; Provornikova, E.

In the heliosheath (HS), Voyager 2 has observed a flow with constant radial velocity and magnetic flux conservation. Voyager 1, however, has observed a decrease in the flow’s radial velocity and an order of magnitude decrease in magnetic flux. We investigate the role of the 11 yr solar cycle variation of the magnetic field strength on the magnetic flux within the HS using a global 3D magnetohydrodynamic model of the heliosphere. We use time and latitude-dependent solar wind velocity and density inferred from Solar and Heliospheric Observatory/SWAN and interplanetary scintillations data and implemented solar cycle variations of the magnetic fieldmore » derived from 27 day averages of the field magnitude average of the magnetic field at 1 AU from the OMNI database. With the inclusion of the solar cycle time-dependent magnetic field intensity, the model matches the observed intensity of the magnetic field in the HS along both Voyager 1 and 2. This is a significant improvement from the same model without magnetic field solar cycle variations, which was over a factor of two larger. The model accurately predicts the radial velocity observed by Voyager 2; however, the model predicts a flow speed ∼100 km s{sup −1} larger than that derived from LECP measurements at Voyager 1. In the model, magnetic flux is conserved along both Voyager trajectories, contrary to observations. This implies that the solar cycle variations in solar wind magnetic field observed at 1 AU does not cause the order of magnitude decrease in magnetic flux observed in the Voyager 1 data.« less

Solar Neutrino Problem

DOE R&D Accomplishments Database

Davis, R. Jr.; Evans, J. C.; Cleveland, B. T.

1978-04-28

A summary of the results of the Brookhaven solar neutrino experiment is given and discussed in relation to solar model calculations. A review is given of the merits of various new solar neutrino detectors that were proposed.

A generalized analysis of solar space heating in the United States

NASA Astrophysics Data System (ADS)

Clark, J. A.

A life-cycle model is developed for solar space heating within the United States that is based on the solar design data from the Los Alamos Scientific Laboratory. The model consists of an analytical relationship among five dimensionless parameters that include all pertinent technical, climatological, solar, operating and economic factors that influence the performance of a Solar Space Heating System. An important optimum condition presented is the 'Breakeven' metered cost of conventional fuel at which the cost of the solar system is equal to that of a conventional heating system. The effect of Federal (1980) and State (1979) income tax credits on these costs is determined. A parameter that includes both solar availability and solar system utilization is derived and plotted on a map of the U.S. This parameter shows the most favorable present locations for solar space heating application to be in the Central and Mountain States. The data employed are related to the rehabilitated solar data recently made available by the National Climatic Center (SOLMET).

Solar Signals in CMIP-5 Simulations: The Stratospheric Pathway

NASA Technical Reports Server (NTRS)

Mitchell, D.M.; Misios, S.; Gray, L. J.; Tourpali, K.; Matthes, K.; Hood, L.; Schmidt, H.; Chiodo, G.; Thieblemont, R.; Rozanov, E.;

If We Can't Predict Solar Cycle 24, What About Solar Cycle 34?

NASA Technical Reports Server (NTRS)

Pesnell. William Dean

2008-01-01

Predictions of solar activity in Solar Cycle 24 range from 50% larger than SC 23 to the onset of a Grand Minimum. Because low levels of solar activity are associated with global cooling in paleoclimate and isotopic records, anticipating these extremes is required in any longterm extrapolation of climate variability. Climate models often look forward 100 or more years, which would mean 10 solar cycles into the future. Predictions of solar activity are derived from a number of methods, most of which, such as climatology and physics-based models, will be familiar to atmospheric scientists. More than 50 predictions of the maximum amplitude of SC 24 published before solar minimum will be discussed. Descriptions of several methods that result in the extreme predictions and some anticipation of even longer term predictions will be presented.

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, K. S.

1985-01-01

This semiannual progress report covers the period from April 1, 1985 to Sept. 30, 1985 under NASA grant NAS1-441 entitled direct solar pumped iodine laser amplifier. During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator was carried out before the amplifier studies. The amplifier studies are postponed to the extended period following completion of the parametric studies. In addition, the kinetic modeling of a solar pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) the radiation characteristics of solar simulator and the parametric characteristics of photodissociation iodine laser continuously pumped by a Vortek solar simulator; (2) kinetic modeling of a solar pumped iodine laser amplifier; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

The Effect of a Potentially Low Solar Cycle #24 on Orbital Lifetimes of Fengyun 1-C Debris

NASA Technical Reports Server (NTRS)

Whitlock, David; Johnson, Nicholas; Matney, Mark; Krisko, Paula

2008-01-01

The magnitude of Solar Cycle #24 will have a non-trivial impact on the lifetimes of debris pieces that resulted from the intentional hypervelocity impact of the Fengyun 1-C satellite in January 2007. Recent solar flux measurements indicate Solar Cycle #24 has begun in the last few months, and will continue until approximately 2019. While there have been differing opinions on whether the intensity of this solar cycle will be higher or lower than usual, the Space Weather Prediction Center within the National Oceanic Atmospheric Administration (NOAA/SWPC) has recently forecast unusually low solar activity, which would result in longer orbital lifetimes. Using models for both the breakup of Fengyun 1-C and the propagation of the resultant debris cloud, the Orbital Debris Program Office at NASA Johnson Space Center conducted a study to better understand the impact of the solar cycle on lifetimes for pieces as small as 1 mm. Using a modified collision breakup model and PROP3D propagation software, the orbits of nearly 2 million objects 1 mm and larger were propagated for up to 200 years. By comparing a normal solar cycle with that of the NOAA/SWPC forecast low cycle, the effect of the solar flux on the lifetimes of the debris pieces is evaluated. The modeling of the low solar cycle shows an additional debris count of 12% for pieces larger than 10 cm by 2019 when compared to the resultant debris count using a normal cycle. The difference becomes more exaggerated (over 15%) for debris count in the smaller size regimes. However, in 50 years, the models predict the differences in debris count from differing models of Solar Cycle #24 to be less than 10% for all size regimes, with less variance in the smaller sizes. Understanding the longevity of the debris cloud will affect collision probabilities for both operational spacecraft and large derelict objects over the next century and beyond.

Modeling thermospheric neutral density

NASA Astrophysics Data System (ADS)

Qian, Liying

Satellite drag prediction requires determination of thermospheric neutral density. The NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM) and the global-mean Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (TIMEGCM) were used to quantify thermospheric neutral density and its variations, focusing on annual/semiannual variation, the effect of using measured solar irradiance on model calculations of solar-cycle variation, and global change in the thermosphere. Satellite drag data and the MSIS00 empirical model were utilized to compare to the TIEGCM simulations. The TIEGCM simulations indicated that eddy diffusion and its annual/semiannual variation is a mechanism for annual/semiannual density variation in the thermosphere. It was found that eddy diffusion near the turbopause can effectively influence thermospheric neutral density. Eddy diffusion, together with annual insolation variation and large-scale circulation, generated global annual/semiannual density variation observed by satellite drag. Using measured solar irradiance as solar input for the TIEGCM improved the solar-cycle dependency of the density calculation shown in F10.7 -based thermospheric empirical models. It has been found that the empirical models overestimate density at low solar activity. The TIEGCM simulations did not show such solar-cycle dependency. Using historic measurements of CO2 and F 10.7, simulations of the global-mean TIMEGCM showed that thermospheric neutral density at 400 km had an average long-term decrease of 1.7% per decade from 1970 to 2000. A forecast of density decrease for solar cycle 24 suggested that thermospheric density will decrease at 400 km from present to the end of solar cycle 24 at a rate of 2.7% per decade. Reduction in thermospheric density causes less atmospheric drag on earth-orbiting space objects. The implication of this long-term decrease of thermospheric neutral density is that it will increase the lifetime of satellites, but also it will increase the amount of space junk.

Modelling total solar irradiance using a flux transport model

NASA Astrophysics Data System (ADS)

Dasi Espuig, Maria; Jiang, Jie; Krivova, Natalie; Solanki, Sami

2014-05-01

Reconstructions of solar irradiance into the past are of considerable interest for studies of solar influence on climate. Models based on the assumption that irradiance changes are caused by the evolution of the photospheric magnetic field have been the most successful in reproducing the measured irradiance variations. Our SATIRE-S model is one of these. It uses solar full-disc magnetograms as an input, and these are available for less than four decades. Thus, to reconstruct the irradiance back to times when no observed magnetograms are available, we combine the SATIRE-S model with synthetic magnetograms, produced using a surface flux transport model. The model is fed with daily, observed or modelled statistically, records of sunspot positions, areas, and tilt angles. To describe the secular change in the irradiance, we used the concept of overlapping ephemeral region cycles. With this technique TSI can be reconstructed back to 1700.

An efficient descriptor model for designing materials for solar cells

NASA Astrophysics Data System (ADS)

Alharbi, Fahhad H.; Rashkeev, Sergey N.; El-Mellouhi, Fedwa; Lüthi, Hans P.; Tabet, Nouar; Kais, Sabre

2015-11-01

An efficient descriptor model for fast screening of potential materials for solar cell applications is presented. It works for both excitonic and non-excitonic solar cells materials, and in addition to the energy gap it includes the absorption spectrum (α(E)) of the material. The charge transport properties of the explored materials are modelled using the characteristic diffusion length (Ld) determined for the respective family of compounds. The presented model surpasses the widely used Scharber model developed for bulk heterojunction solar cells. Using published experimental data, we show that the presented model is more accurate in predicting the achievable efficiencies. To model both excitonic and non-excitonic systems, two different sets of parameters are used to account for the different modes of operation. The analysis of the presented descriptor model clearly shows the benefit of including α(E) and Ld in view of improved screening results.

Development of a computational model for predicting solar wind flows past nonmagnetic terrestrial planets

NASA Technical Reports Server (NTRS)

Stahara, S. S.; Spreiter, J. R.

1983-01-01

A computational model for the determination of the detailed plasma and magnetic field properties of the global interaction of the solar wind with nonmagnetic terrestrial planetary obstacles is described. The theoretical method is based on an established single fluid, steady, dissipationless, magnetohydrodynamic continuum model, and is appropriate for the calculation of supersonic, super-Alfvenic solar wind flow past terrestrial ionospheres.

Comprehensive silicon solar-cell computer modeling

NASA Technical Reports Server (NTRS)

Lamorte, M. F.

1984-01-01

A comprehensive silicon solar cell computer modeling scheme was developed to perform the following tasks: (1) model and analysis of the net charge distribution in quasineutral regions; (2) experimentally determined temperature behavior of Spire Corp. n+pp+ solar cells where n+-emitter is formed by ion implantation of 75As or 31P; and (3) initial validation results of computer simulation program using Spire Corp. n+pp+ cells.

Extreme Ultraviolet Variability Experiment (EVE) on the Solar Dynamics Observatory (SDO): Overview of Science Objectives, Instrument Design, Data Products, and Model Developments

NASA Technical Reports Server (NTRS)

Woods, T. N.; Eparvier, F. G.; Hock, R.; Jones, A. R.; Woodraska, D.; Judge, D.; Didkovsky, L.; Lean, J.; Mariska, J.; Warren, H.;

Atmospheric drag model calibrations for spacecraft lifetime prediction

NASA Technical Reports Server (NTRS)

Binebrink, A. L.; Radomski, M. S.; Samii, M. V.

1989-01-01

Although solar activity prediction uncertainty normally dominates decay prediction error budget for near-Earth spacecraft, the effect of drag force modeling errors for given levels of solar activity needs to be considered. Two atmospheric density models, the modified Harris-Priester model and the Jacchia-Roberts model, to reproduce the decay histories of the Solar Mesosphere Explorer (SME) and Solar Maximum Mission (SMM) spacecraft in the 490- to 540-kilometer altitude range were analyzed. Historical solar activity data were used in the input to the density computations. For each spacecraft and atmospheric model, a drag scaling adjustment factor was determined for a high-solar-activity year, such that the observed annual decay in the mean semimajor axis was reproduced by an averaged variation-of-parameters (VOP) orbit propagation. The SME (SMM) calibration was performed using calendar year 1983 (1982). The resulting calibration factors differ by 20 to 40 percent from the predictions of the prelaunch ballistic coefficients. The orbit propagations for each spacecraft were extended to the middle of 1988 using the calibrated drag models. For the Jaccia-Roberts density model, the observed decay in the mean semimajor axis of SME (SMM) over the 4.5-year (5.5-year) predictive period was reproduced to within 1.5 (4.4) percent. The corresponding figure for the Harris-Priester model was 8.6 (20.6) percent. Detailed results and conclusions regarding the importance of accurate drag force modeling for lifetime predictions are presented.

A simplified solar cell array modelling program

NASA Technical Reports Server (NTRS)

Hughes, R. D.

1982-01-01

As part of the energy conversion/self sufficiency efforts of DSN engineering, it was necessary to have a simplified computer model of a solar photovoltaic (PV) system. This article describes the analysis and simplifications employed in the development of a PV cell array computer model. The analysis of the incident solar radiation, steady state cell temperature and the current-voltage characteristics of a cell array are discussed. A sample cell array was modelled and the results are presented.

150 kW Class Solar Electric Propulsion Spacecraft Power Architecture Model

NASA Technical Reports Server (NTRS)

Csank, Jeffrey T.; Aulisio, Michael V.; Loop, Benjamin

2017-01-01

The National Aeronautics and Space Administration (NASA) Solar Electric Propulsion Technology Demonstration Mission in conjunction with PC Krause and Associates has created a Simulink-based power architecture model for a 50 kilo-Watt (kW) solar electric propulsion system. NASA has extended this model to investigate 150 kW solar electric propulsion systems. Increasing the power system capability from 50 kW to 150 kW better aligns with the anticipated power requirements for Mars and other deep space explorations. The high-power solar electric propulsion capability has been identified as a critical part of NASAs future beyond-low-Earth-orbit for human-crewed exploration missions. This paper presents multiple 150 kW architectures, simulation results, and a discussion of their merits.

Three-Fluid Magnetohydrodynamic Modeling of the Solar Wind in the Outer Heliosphere

NASA Technical Reports Server (NTRS)

Usmanov, Arcadi V.; Goldstein, Melvyn L.; Matthaeus, William H.

2011-01-01

We have developed a three-fluid, fully three-dimensional magnetohydrodynamic model of the solar wind plasma in the outer heliosphere as a co-moving system of solar wind protons, electrons, and interstellar pickup protons, with separate energy equations for each species. Our approach takes into account the effects of electron heat conduction and dissipation of Alfvenic turbulence on the spatial evolution of the solar wind plasma and interplanetary magnetic fields. The turbulence transport model is based on the Reynolds decomposition of physical variables into mean and fluctuating components and uses the turbulent phenomenologies that describe the conversion of fluctuation energy into heat due to a turbulent cascade. We solve the coupled set of the three-fluid equations for the mean-field solar wind and the turbulence equations for the turbulence energy, cross helicity, and correlation length. The equations are written in the rotating frame of reference and include heating by turbulent dissipation, energy transfer from interstellar pickup protons to solar wind protons, and solar wind deceleration due to the interaction with the interstellar hydrogen. The numerical solution is constructed by the time relaxation method in the region from 0.3 to 100 AU. Initial results from the novel model are presented.

The faint young Sun paradox: an observational test of an alternative solar model

NASA Technical Reports Server (NTRS)

Gaidos, E. J.; Gudel, M.; Blake, G. A.

2000-01-01

We report the results of deep observations at radio (3.6 cm) wavelengths of the nearby solar-type star pi 01 Ursa Majoris with the Very Large Array (VLA) intended to test an alternative theory of solar luminosity evolution. The standard model predicts a solar luminosity only 75% of the present value and surface temperatures below freezing on Earth and Mars at 4 Ga, seemingly in conflict with geologic evidence for liquid water on these planets. An alternative model invokes a compensatory mass loss through a declining solar wind that results in a more consistent early luminosity. The free-free emission from an enhanced wind around nearby young Sun-like stars should be detectable at microwave frequencies. Our observations of pi 01 UMa, a 300 million year-old solar-mass star, place an upper limit on the mass loss rate of 4-5 x 10(-11) M(solar) yr-1. Total mass loss from such a star over 4 Gyr would be less than 6%. If this star is indeed an analog of the early Sun, it casts doubt on the alternative model as a solution to the faint young Sun paradox, particularly for Mars.

Ninth Workshop 'Solar Influences on the Magnetosphere, Ionosphere and Atmosphere'

NASA Astrophysics Data System (ADS)

Georgieva, Kayta; Kirov, Boian; Danov, Dimitar

2017-08-01

The 9th Workshop "Solar Influences on the Magnetosphere, Ionosphere and Atmosphere" is an international forum for scientists working in the fields of: Sun and solar activity, Solar wind-magnetosphere-ionosphere interactions, Solar influences on the lower atmosphere and climate, Solar effects in the biosphere, Instrumentation for space weather monitoring and Data processing and modelling.

CONTROLLING INFLUENCE OF MAGNETIC FIELD ON SOLAR WIND OUTFLOW: AN INVESTIGATION USING CURRENT SHEET SOURCE SURFACE MODEL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Poduval, B., E-mail: bpoduval@spacescience.org

2016-08-10

This Letter presents the results of an investigation into the controlling influence of large-scale magnetic field of the Sun in determining the solar wind outflow using two magnetostatic coronal models: current sheet source surface (CSSS) and potential field source surface. For this, we made use of the Wang and Sheeley inverse correlation between magnetic flux expansion rate (FTE) and observed solar wind speed (SWS) at 1 au. During the period of study, extended over solar cycle 23 and beginning of solar cycle 24, we found that the coefficients of the fitted quadratic equation representing the FTE–SWS inverse relation exhibited significantmore » temporal variation, implying the changing pattern of the influence of FTE on SWS over time. A particularly noteworthy feature is an anomaly in the behavior of the fitted coefficients during the extended minimum, 2008–2010 (CRs 2073–2092), which is considered due to the particularly complex nature of the solar magnetic field during this period. However, this variation was significant only for the CSSS model, though not a systematic dependence on the phase of the solar cycle. Further, we noticed that the CSSS model demonstrated better solar wind prediction during the period of study, which we attribute to the treatment of volume and sheet currents throughout the corona and the more accurate tracing of footpoint locations resulting from the geometry of the model.« less

Galactic and solar radiation exposure to aircrew during a solar cycle.

PubMed

Lewis, B J; Bennett, L G I; Green, A R; McCall, M J; Ellaschuk, B; Butler, A; Pierre, M

2002-01-01

An on-going investigation using a tissue-equivalent proportional counter (TEPC) has been carried out to measure the ambient dose equivalent rate of the cosmic radiation exposure of aircrew during a solar cycle. A semi-empirical model has been derived from these data to allow for the interpolation of the dose rate for any global position. The model has been extended to an altitude of up to 32 km with further measurements made on board aircraft and several balloon flights. The effects of changing solar modulation during the solar cycle are characterised by correlating the dose rate data to different solar potential models. Through integration of the dose-rate function over a great circle flight path or between given waypoints, a Predictive Code for Aircrew Radiation Exposure (PCAIRE) has been further developed for estimation of the route dose from galactic cosmic radiation exposure. This estimate is provided in units of ambient dose equivalent as well as effective dose, based on E/H x (10) scaling functions as determined from transport code calculations with LUIN and FLUKA. This experimentally based treatment has also been compared with the CARI-6 and EPCARD codes that are derived solely from theoretical transport calculations. Using TEPC measurements taken aboard the International Space Station, ground based neutron monitoring, GOES satellite data and transport code analysis, an empirical model has been further proposed for estimation of aircrew exposure during solar particle events. This model has been compared to results obtained during recent solar flare events.

Hybrid Model of Inhomogeneous Solar Wind Plasma Heating by Alfven Wave Spectrum: Parametric Studies

NASA Technical Reports Server (NTRS)

Ofman, L.

2010-01-01

Observations of the solar wind plasma at 0.3 AU and beyond show that a turbulent spectrum of magnetic fluctuations is present. Remote sensing observations of the corona indicate that heavy ions are hotter than protons and their temperature is anisotropic (T(sub perpindicular / T(sub parallel) >> 1). We study the heating and the acceleration of multi-ion plasma in the solar wind by a turbulent spectrum of Alfvenic fluctuations using a 2-D hybrid numerical model. In the hybrid model the protons and heavy ions are treated kinetically as particles, while the electrons are included as neutralizing background fluid. This is the first two-dimensional hybrid parametric study of the solar wind plasma that includes an input turbulent wave spectrum guided by observation with inhomogeneous background density. We also investigate the effects of He++ ion beams in the inhomogeneous background plasma density on the heating of the solar wind plasma. The 2-D hybrid model treats parallel and oblique waves, together with cross-field inhomogeneity, self-consistently. We investigate the parametric dependence of the perpendicular heating, and the temperature anisotropy in the H+-He++ solar wind plasma. It was found that the scaling of the magnetic fluctuations power spectrum steepens in the higher-density regions, and the heating is channeled to these regions from the surrounding lower-density plasma due to wave refraction. The model parameters are applicable to the expected solar wind conditions at about 10 solar radii.

Space Environment Modelling with the Use of Artificial Intelligence Methods

NASA Astrophysics Data System (ADS)

Lundstedt, H.; Wintoft, P.; Wu, J.-G.; Gleisner, H.; Dovheden, V.

1996-12-01

Space based technological systems are affected by the space weather in many ways. Several severe failures of satellites have been reported at times of space storms. Our society also increasingly depends on satellites for communication, navigation, exploration, and research. Predictions of the conditions in the satellite environment have therefore become very important. We will here present predictions made with the use of artificial intelligence (AI) techniques, such as artificial neural networks (ANN) and hybrids of AT methods. We are developing a space weather model based on intelligence hybrid systems (IHS). The model consists of different forecast modules, each module predicts the space weather on a specific time-scale. The time-scales range from minutes to months with the fundamental time-scale of 1-5 minutes, 1-3 hours, 1-3 days, and 27 days. Solar and solar wind data are used as input data. From solar magnetic field measurements, either made on the ground at Wilcox Solar Observatory (WSO) at Stanford, or made from space by the satellite SOHO, solar wind parameters can be predicted and modelled with ANN and MHD models. Magnetograms from WSO are available on a daily basis. However, from SOHO magnetograms will be available every 90 minutes. SOHO magnetograms as input to ANNs will therefore make it possible to even predict solar transient events. Geomagnetic storm activity can today be predicted with very high accuracy by means of ANN methods using solar wind input data. However, at present real-time solar wind data are only available during part of the day from the satellite WIND. With the launch of ACE in 1997, solar wind data will on the other hand be available during 24 hours per day. The conditions of the satellite environment are not only disturbed at times of geomagnetic storms but also at times of intense solar radiation and highly energetic particles. These events are associated with increased solar activity. Predictions of these events are therefore also handled with the modules in the Lund Space Weather Model. Interesting Links: Lund Space Weather and AI Center

Demonstration PreFab Solar Heated Vacation Home

ERIC Educational Resources Information Center

Ariola, Frank; Walencik, Vincent J.

1978-01-01

To update a traditional construction shop program, students at Passaic Valley High School, New Jersey, developed a mock-up model of a solar-heated A-frame vacation house using prefab construction. The article describes the project and illustrates it with photographs of the model and a drawing of the solar collector. (MF)

Continuing data analysis of the AS/E grazing incidence X-ray telescope experiment on the OSO-4 satellite

NASA Technical Reports Server (NTRS)

Vaiana, G.; Haggerty, R.; Kahler, S.; Krieger, A.; Landini, M.; Timothy, A.; Webb, D.

1973-01-01

The work to correct and extend the calculation of the theoretical solar X-ray spectrum produced during earlier OSO-4 data analysis is reported along with the work to formulate models of active regions, and compare these models with the experimental values. An atlas of solar X-ray photographs is included, and solar X-ray observations are correlated with the solar wind.

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, Kwang S.; Kim, K. H.; Stock, L. V.

1987-01-01

The improvement on the collection system of the Tarmarack Solar Simulator beam was attemped. The basic study of evaluating the solid state laser materials for the solar pumping and also the work to construct a kinetic model algorithm for the flashlamp pumped iodine lasers were carried out. It was observed that the collector cone worked better than the lens assembly in order to collect the solar simulator beam and to focus it down to a strong power density. The study on the various laser materials and their lasing characteristics shows that the neodymium and chromium co-doped gadolinium scandium gallium garnet (Nr:Cr:GSGG) may be a strong candidate for the high power solar pumped solid state laser crystal. On the other hand the improved kinetic modeling for the flashlamp pumped iodine laser provides a good agreement between the theoretical model and the experimental data on the laser power output, and predicts the output parameters of a solar pumped iodine laser.

Model of Energy Spectrum Parameters of Ground Level Enhancement Events in Solar Cycle 23

NASA Astrophysics Data System (ADS)

Wu, S.-S.; Qin, G.

2018-01-01

Mewaldt et al. (2012) fitted the observations of the ground level enhancement (GLE) events during solar cycle 23 to the double power law equation to obtain the four spectral parameters, the normalization constant C, low-energy power law slope γ1, high-energy power law slope γ2, and break energy E0. There are 16 GLEs from which we select 13 for study by excluding some events with complicated situation. We analyze the four parameters with conditions of the corresponding solar events. According to solar event conditions, we divide the GLEs into two groups, one with strong acceleration by interplanetary shocks and another one without strong acceleration. By fitting the four parameters with solar event conditions we obtain models of the parameters for the two groups of GLEs separately. Therefore, we establish a model of energy spectrum of solar cycle 23 GLEs, which may be used in prediction in the future.

Analysis of type II and type III solar radio bursts

NASA Astrophysics Data System (ADS)

Wijesekera, J. V.; Jayaratne, K. P. S. C.; Adassuriya, J.

2018-04-01

Solar radio burst is an arrangement of a frequency space that variation with time. Most of radio burst can be identified in low frequency range such as below 200 MHz and depending on frequencies. Solar radio bursts were the first phenomenon identified in the field of radio astronomy field. Solar radio frequency range is from 70 MHz to 2.2 GHz. Most of the radio burst can be identified in a low frequency range such as below 200 MHz. Properties of low-frequency radio were analyzed this research. There are two types of solar radio bursts were analyzed, named as type II and type III radio bursts. Exponential decay type could be seen in type II, and a linear could be indicated in type III solar radio bursts. The results of the drift rate graphs show the values of each chosen solar radio burst. High drift rate values can be seen in type III solar flares whereas low to medium drift rate values can be seen in type II solar flares. In the second part of the research the Newkirk model electron density model was used to estimate the drift velocities of the solar radio bursts. Although the special origin of the solar radio burst is not known clearly we assumed. The chosen solar radio bursts were originated within the solar radius of 0.9 - 1.3 range from the photosphere. We used power low in the form of (x) = A × 10‑bx were that the electron density related to the height of the solar atmosphere. The calculation of the plasma velocity of each solar radio burst was done using the electron density model and drift rates. Therefore velocity of chosen type II solar radio bursts indicates low velocities. The values are 233.2499 Km s‑1, 815.9522 Km s‑1 and 369.5425 Km s‑1. Velocity of chosen type III solar radio bursts were 1443.058 Km s‑1and 1205.05Km s ‑1.

Modeling and Analysis of Geoelectric Fields: Extended Solar Shield

NASA Astrophysics Data System (ADS)

Ngwira, C. M.; Pulkkinen, A. A.

2016-12-01

In the NASA Applied Sciences Program Solar Shield project, an unprecedented first-principles-based system to forecast geomagnetically induced current (GIC) in high-voltage power transmission systems was developed. Rapid progress in the field of numerical physics-based space environment modeling has led to major developments over the past few years. In this study modeling and analysis of induced geoelectric fields is discussed. Specifically, we focus on the successful incorporation of 3-D EM transfer functions in the modeling of E-fields, and on the analysis of near real-time simulation outputs used in the Solar Shield forecast system. The extended Solar Shield is a collaborative project between DHS, NASA, NOAA, CUA and EPRI.

Recent solar extreme ultraviolet irradiance observations and modeling: A review

NASA Technical Reports Server (NTRS)

Tobiska, W. Kent

1993-01-01

For more than 90 years, solar extreme ultraviolet (EUV) irradiance modeling has progressed from empirical blackbody radiation formulations, through fudge factors, to typically measured irradiances and reference spectra was well as time-dependent empirical models representing continua and line emissions. A summary of recent EUV measurements by five rockets and three satellites during the 1980s is presented along with the major modeling efforts. The most significant reference spectra are reviewed and threee independently derived empirical models are described. These include Hinteregger's 1981 SERF1, Nusinov's 1984 two-component, and Tobiska's 1990/1991/SERF2/EUV91 flux models. They each provide daily full-disk broad spectrum flux values from 2 to 105 nm at 1 AU. All the models depend to one degree or another on the long time series of the Atmosphere Explorer E (AE-E) EUV database. Each model uses ground- and/or space-based proxies to create emissions from solar atmospheric regions. Future challenges in EUV modeling are summarized including the basic requirements of models, the task of incorporating new observations and theory into the models, the task of comparing models with solar-terrestrial data sets, and long-term goals and modeling objectives. By the late 1990s, empirical models will potentially be improved through the use of proposed solar EUV irradiance measurements and images at selected wavelengths that will greatly enhance modeling and predictive capabilities.

An economic model for passive solar designs in commercial environments

NASA Astrophysics Data System (ADS)

Powell, J. W.

1980-06-01

The model incorporates a life cycle costing approach that focuses on the costs of purchase, installation, maintenance, repairs, replacement, and energy. It includes a detailed analysis of tax laws affecting the use of solar energy in commercial buildings. Possible methods of treating difficult to measure benefits and costs, such as effects of the passive solar design on resale value of the building and on lighting costs, rental income from the building, and the use of commercial space, are presented. The model is illustrated in two case examples of prototypical solar design for low rise commercial buildings in an urban setting.

Implementing Badhwar-O'Neill Galactic Cosmic Ray Model for the Analysis of Space Radiation Exposure

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; O'Neill, Patrick M.; Slaba, Tony C.

2014-01-01

For the analysis of radiation risks to astronauts and planning exploratory space missions, accurate energy spectrum of galactic cosmic radiation (GCR) is necessary. Characterization of the ionizing radiation environment is challenging because the interplanetary plasma and radiation fields are modulated by solar disturbances and the radiation doses received by astronauts in interplanetary space are likewise influenced. A model of the Badhwar-O'Neill 2011 (BO11) GCR environment, which is represented by GCR deceleration potential theta, has been derived by utilizing all of the GCR measurements from balloons, satellites, and the newer NASA Advanced Composition Explorer (ACE). In the BO11 model, the solar modulation level is derived from the mean international sunspot numbers with time-delay, which has been calibrated with actual flight instrument measurements to produce better GCR flux data fit during solar minima. GCR fluxes provided by the BO11 model were compared with various spacecraft measurements at 1 AU, and further comparisons were made for the tissue equivalent proportional counters measurements at low Earth orbits using the high-charge and energy transport (HZETRN) code and various GCR models. For the comparison of the absorbed dose and dose equivalent calculations with the measurements by Radiation Assessment Detector (RAD) at Gale crater on Mars, the intensities and energies of GCR entering the heliosphere were calculated by using the BO11 model, which accounts for time-dependent attenuation of the local interstellar spectrum of each element. The BO11 model, which has emphasized for the last 24 solar minima, showed in relatively good agreement with the RAD data for the first 200 sols, but it was resulted in to be less well during near the solar maximum of solar cycle 24 due to subtleties in the changing heliospheric conditions. By performing the error analysis of the BO11 model and the optimization in reducing overall uncertainty, the resultant BO13 model corrects the fit at solar maxima as well as being accurate at solar minima. The BO13 model is implemented to the NASA Space Cancer Risk model for the assessment of radiation risks. Overall cumulative probability distribution of solar modulation parameters represents the percentile rank of the average interplanetary GCR environment, and the probabilistic radiation risks can be assessed for various levels of GCR environment to support mission design and operational planning for future manned space exploration missions.

Stratospheric O3 changes during 2001-2010: the small role of solar flux variations in a CTM

NASA Astrophysics Data System (ADS)

Dhomse, S. S.; Chipperfield, M. P.; Feng, W.; Ball, W. T.; Unruh, Y. C.; Haigh, J. D.; Krivova, N. A.; Solanki, S. K.; Smith, A. K.

2013-05-01

Solar spectral fluxes (or irradiance) measured by the SOlar Radiation and Climate Experiment (SORCE) show different variability at ultraviolet (UV) wavelengths compared to other irradiance measurements and models (e.g. NRL-SSI, SATIRE-S). Some modelling studies have suggested that stratospheric/lower mesospheric O3 changes during solar cycle 23 (1996-2008) can only be reproduced if SORCE solar fluxes are used. We have used a 3-D chemical transport model (CTM), forced by meteorology from the European Centre for Medium-Range Weather Forecasts (ECMWF), to simulate middle atmospheric O3 using three different solar flux datasets (SORCE, NRL-SSI and SATIRE-S). Simulated O3 changes are compared with Microwave Limb Sounder (MLS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite data. Modelled O3 anomalies from all solar flux datasets show good agreement with the observations, despite the different flux variations. The off-line CTM reproduces these changes through dynamical information contained in the analyses. A notable feature during this period is a robust positive solar signal in the tropical middle stratosphere due to changes in stratospheric dynamics. Ozone changes in the lower mesosphere cannot be used to discriminate between solar flux datasets due to large uncertainties and the short time span of the observations. Overall this study suggests that, in a CTM, the UV variations detected by SORCE are not necessary to reproduce observed stratospheric O3 changes during 2001-2010.

Direct solar-pumped iodine laser amplifier

NASA Technical Reports Server (NTRS)

Han, K. S.

1986-01-01

During this period the parametric studies of the iodine laser oscillator pumped by a Vortek simulator were carried out before amplifier studies. The amplifier studies are postponed to the extended period after completing the parametric studies. In addition, the kinetic modeling of a solar-pumped iodine laser amplifier, and the experimental work for a solar pumped dye laser amplifier are in progress. This report contains three parts: (1) a 10 W CW iodine laser pumped by a Vortek solar simulator; (2) kinetic modeling to predict the time to lasing threshold, lasing time, and energy output of solar-pumped iodine laser; and (3) the study of the dye laser amplifier pumped by a Tamarack solar simulator.

Solar wind electron densities from Viking dual-frequency radio measurements

NASA Technical Reports Server (NTRS)

Muhleman, D. O.; Anderson, J. D.

1981-01-01

Simultaneous phase coherent, two-frequency measurements of the time delay between the earth station and the Viking spacecraft have been analyzed in terms of the electron density profiles from 4 solar radii to 200 solar radii. The measurements were made during a period of solar activity minimum (1976-1977) and show a strong solar latitude effect. The data were analyzed with both a model independent, direct numerical inversion technique and with model fitting, yielding essentially the same results. It is shown that the solar wind density can be represented by two power laws near the solar equator proportional to r exp -2.7 and r exp -2.04. However, the more rapidly falling term quickly disappears at moderate latitudes (approximately 20 deg) leaving only the inverse-square behavior.

Baseline and Target Values for PV Forecasts: Toward Improved Solar Power Forecasting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jie; Hodge, Bri-Mathias; Lu, Siyuan

2015-10-05

Accurate solar power forecasting allows utilities to get the most out of the solar resources on their systems. To truly measure the improvements that any new solar forecasting methods can provide, it is important to first develop (or determine) baseline and target solar forecasting at different spatial and temporal scales. This paper aims to develop baseline and target values for solar forecasting metrics. These were informed by close collaboration with utility and independent system operator partners. The baseline values are established based on state-of-the-art numerical weather prediction models and persistence models. The target values are determined based on the reductionmore » in the amount of reserves that must be held to accommodate the uncertainty of solar power output.« less

Spatio-temporal distribution of global solar radiation for Mexico using GOES data

NASA Astrophysics Data System (ADS)

Bonifaz, R.; Cuahutle, M.; Valdes, M.; Riveros, D.

2013-05-01

Increased need of sustainable and renewable energies around the world requires studies about the amount and distribution of such types of energies. Global solar radiation distribution in space and time is a key component on order to know the availability of the energy for different applications. Using GOES hourly data, the heliosat model was implemented for Mexico. Details about the model and its components are discussed step by stem an once obtained the global solar radiation images, different time datasets (hourly, daily, monthly and seasonal) were built in order to know the spatio-temporal behavior of this type of energy. Preliminary maps of the available solar global radiation energy for Mexico are presented, the amount and variation of the solar radiation by regions are analyzed and discussed. Future work includes a better parametrization of the model using calibrated ground stations data and more use of more complex models for better results.

Performance and Simulation of a Stand-alone Parabolic Trough Solar Thermal Power Plant

NASA Astrophysics Data System (ADS)

Mohammad, S. T.; Al-Kayiem, H. H.; Assadi, M. K.; Gilani, S. I. U. H.; Khlief, A. K.

2018-05-01

In this paper, a Simulink® Thermolib Model has been established for simulation performance evaluation of Stand-alone Parabolic Trough Solar Thermal Power Plant in Universiti Teknologi PETRONAS, Malaysia. This paper proposes a design of 1.2 kW parabolic trough power plant. The model is capable to predict temperatures at any system outlet in the plant, as well as the power output produced. The conditions that are taken into account as input to the model are: local solar radiation and ambient temperatures, which have been measured during the year. Other parameters that have been input to the model are the collector’s sizes, location in terms of latitude and altitude. Lastly, the results are presented in graphical manner to describe the analysed variations of various outputs of the solar fields obtained, and help to predict the performance of the plant. The developed model allows an initial evaluation of the viability and technical feasibility of any similar solar thermal power plant.

Uncertainty Model for Total Solar Irradiance Estimation on Australian Rooftops

NASA Astrophysics Data System (ADS)

Al-Saadi, Hassan; Zivanovic, Rastko; Al-Sarawi, Said

2017-11-01

The installations of solar panels on Australian rooftops have been in rise for the last few years, especially in the urban areas. This motivates academic researchers, distribution network operators and engineers to accurately address the level of uncertainty resulting from grid-connected solar panels. The main source of uncertainty is the intermittent nature of radiation, therefore, this paper presents a new model to estimate the total radiation incident on a tilted solar panel. Where a probability distribution factorizes clearness index, the model is driven upon clearness index with special attention being paid for Australia with the utilization of best-fit-correlation for diffuse fraction. The assessment of the model validity is achieved with the adoption of four goodness-of-fit techniques. In addition, the Quasi Monte Carlo and sparse grid methods are used as sampling and uncertainty computation tools, respectively. High resolution data resolution of solar irradiations for Adelaide city were used for this assessment, with an outcome indicating a satisfactory agreement between actual data variation and model.

Using a Magnetic Flux Transport Model to Predict the Solar Cycle

NASA Technical Reports Server (NTRS)

Lyatskaya, S.; Hathaway, D.; Winebarger, A.

2007-01-01

We present the results of an investigation into the use of a magnetic flux transport model to predict the amplitude of future solar cycles. Recently Dikpati, de Toma, & Gilman (2006) showed how their dynamo model could be used to accurately predict the amplitudes of the last eight solar cycles and offered a prediction for the next solar cycle - a large amplitude cycle. Cameron & Schussler (2007) found that they could reproduce this predictive skill with a simple 1-dimensional surface flux transport model - provided they used the same parameters and data as Dikpati, de Toma, & Gilman. However, when they tried incorporating the data in what they argued was a more realistic manner, they found that the predictive skill dropped dramatically. We have written our own code for examining this problem and have incorporated updated and corrected data for the source terms - the emergence of magnetic flux in active regions. We present both the model itself and our results from it - in particular our tests of its effectiveness at predicting solar cycles.

Advanced solar irradiances applied to satellite and ionospheric operational systems

NASA Astrophysics Data System (ADS)

Tobiska, W. Kent; Schunk, Robert; Eccles, Vince; Bouwer, Dave

Satellite and ionospheric operational systems require solar irradiances in a variety of time scales and spectral formats. We describe the development of a system using operational grade solar irradiances that are applied to empirical thermospheric density models and physics-based ionospheric models used by operational systems that require a space weather characterization. The SOLAR2000 (S2K) and SOLARFLARE (SFLR) models developed by Space Environment Technologies (SET) provide solar irradiances from the soft X-rays (XUV) through the Far Ultraviolet (FUV) spectrum. The irradiances are provided as integrated indices for the JB2006 empirical atmosphere density models and as line/band spectral irradiances for the physics-based Ionosphere Forecast Model (IFM) developed by the Space Environment Corporation (SEC). We describe the integration of these irradiances in historical, current epoch, and forecast modes through the Communication Alert and Prediction System (CAPS). CAPS provides real-time and forecast HF radio availability for global and regional users and global total electron content (TEC) conditions.

Solar Research | NREL

Science.gov Websites

the System Advisor Model (SAM) PV engineering PV performance reliability and safety Solar resource Research Photo of a city landscape with a sun in the background. Solar energy research at NREL includes photovoltaics, concentrating solar power, solar grid and systems integration, and market research

Correlation of Doppler noise during solar conjunctions with fluctuations in solar activity

NASA Technical Reports Server (NTRS)

Berman, A. L.; Rockwell, S. T.

1975-01-01

Deviations betweeb observed Doppler noise and the noise model during solar conjunction were analyzed. It is tentatively concluded that these deviations are due to short-term fluctuations in solar activity as seen along the signal path, and not to solar/antenna structure effects or system noise temperature.

Solar F10.7 radiation - A short term model for Space Station applications

NASA Technical Reports Server (NTRS)

Vedder, John D.; Tabor, Jill L.

1991-01-01

A new method is described for statistically modeling the F10.7 component of solar radiation for 91-day intervals. The resulting model represents this component of the solar flux as a quasi-exponentially correlated, Weibull distributed random variable, and thereby demonstrates excellent agreement with observed F10.7 data. Values of the F10.7 flux are widely used in models of the earth's upper atmosphere because of its high correlation with density fluctuations due to solar heating effects. Because of the direct relation between atmospheric density and drag, a realistic model of the short term fluctuation of the F10.7 flux is important for the design and operation of Space Station Freedom. The method of modeling this flux described in this report should therefore be useful for a variety of Space Station applications.

MODELING THE SOLAR WIND AT THE ULYSSES , VOYAGER , AND NEW HORIZONS SPACECRAFT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, T. K.; Pogorelov, N. V.; Zank, G. P.

The outer heliosphere is a dynamic region shaped largely by the interaction between the solar wind and the interstellar medium. While interplanetary magnetic field and plasma observations by the Voyager spacecraft have significantly improved our understanding of this vast region, modeling the outer heliosphere still remains a challenge. We simulate the three-dimensional, time-dependent solar wind flow from 1 to 80 astronomical units (au), where the solar wind is assumed to be supersonic, using a two-fluid model in which protons and interstellar neutral hydrogen atoms are treated as separate fluids. We use 1 day averages of the solar wind parameters frommore » the OMNI data set as inner boundary conditions to reproduce time-dependent effects in a simplified manner which involves interpolation in both space and time. Our model generally agrees with Ulysses data in the inner heliosphere and Voyager data in the outer heliosphere. Ultimately, we present the model solar wind parameters extracted along the trajectory of the New Horizons spacecraft. We compare our results with in situ plasma data taken between 11 and 33 au and at the closest approach to Pluto on 2015 July 14.« less

A reconstruction of solar irradiance using a flux transport model

NASA Astrophysics Data System (ADS)

Dasi Espuig, Maria; Jiang, Jie; Krivova, Natalie; Solanki, Sami

2013-04-01

Reconstructions of solar irradiance into the past are of considerable interest for studies of solar influence on climate. Models based on the assumption that irradiance changes are caused by the evolution of the photospheric magnetic field have been the most successful in reproducing the measured irradiance variations. Our SATIRE-S model is one of these. It uses solar full-disc magnetograms as an input, and these are available for less than four decades. Thus, to reconstruct the irradiance back to times when no observed magnetograms are available, we combine the SATIRE-S model with synthetic magnetograms, produced using a surface flux transport model. The model is fed with daily, observed or modelled statistically, records of sunspot positions, areas, and tilt angles. To describe the secular change in the irradiance, we used the concept of overlapping ephemeral region cycles. With this technique TSI can be reconstructed back to 1610.

Solar Energy Evolution and Diffusion Studies Webinars | Solar Research |

Science.gov Websites

video Download the transcript Agent-based Models of How Segregation and Peer Effects Influence Solar PV to estimate the relative influence of peer effects, cognitive factors, and economic factors in solar

Non-equilibrium chemistry in the solar nebula and early solar system: Implications for the chemistry of comets

NASA Technical Reports Server (NTRS)

Fegley, Bruce, Jr.

1989-01-01

Theoretical models of solar nebula and early solar system chemistry which take into account the interplay between chemical, physical, and dynamical processes have great utility for deciphering the origin and evolution of the abundant chemically reactive volatiles (H, O, C, N, S) observed in comets. In particular, such models are essential for attempting to distinguish between presolar and solar nebula products and for quantifying the nature and duration of nebular and early solar system processing to which the volatile constituents of comets have been subjected. The diverse processes and energy sources responsible for chemical processing in the solar nebula and early solar system are discussed. The processes considered include homogeneous and heterogeneous thermochemical and photochemical reactions, and disequilibration resulting from fluid transport, condensation, and cooling whenever they occur on timescales shorter than those for chemical reactions.

Phase fluctuations model for EM wave propagation through solar scintillation at superior solar conjunction

NASA Astrophysics Data System (ADS)

Xu, Guanjun; Song, Zhaohui

2017-04-01

Traveling solar wind disturbances have a significant influence on radio wave characteristics during the superior solar conjunction communication. This paper considers the impact of solar scintillation on phase fluctuations of electromagnetic (EM) wave propagation during the superior solar conjunction. Based on the Geometric Optics approximation, the close-form approximation model for phase fluctuations is developed. Both effects of anisotropic temporal variations function of plasma irregularities and their power spectrum are presented and analyzed numerically. It is found that phase fluctuations rapidly decrease with increasing Sun-Earth-Probe angle and decrease with increasing frequency at the rate of 1/f2. Moreover, the role of various features of the solar wind irregularities and their influence on the EM wave characteristic parameters is studied and discussed. Finally, we study the phase fluctuations of typical cases in order to better understand the impact of phase fluctuations in future deep space communication scenarios during solar conjunction periods.

Quasi-Biennial Oscillation and Solar Cycle Influences over the Winter Arctic Simulated by the WACCM4 Model

NASA Astrophysics Data System (ADS)

Li, K. F.; Limpasuvan, T. L.; Limpasuvan, V.; Tung, K. K.; Yung, Y. L.

2017-12-01

Observations show that the quasi-biennial oscillation (QBO) and the 11-year solar cycle perturb the polar vortex via planetary wave convergence at high latitudes, a mechanism first proposed by Holton and Tan in 1980. Their perturbations lead to increases of stratospheric sudden warming events, and hence observable increases in temperature and ozone abundance in the polar vortex, during the easterly phase of QBO and the solar maximum. Here we simulate the changes in the polar atmosphere using the Whole Atmosphere Community Climate Model 4 (WACCM4) with the prescribed QBO and 11-year solar cycle forcing. The simulation is diagnosed in four groups: westerly QBO phase and solar minimum, westerly QBO phase and solar maximum, easterly QBO phase and solar minimum, and easterly QBO phase and solar maximum. The simulated changes in temperature and ozone are compared with satellite observations.

Solar Atmosphere to Earth's Surface: Long Lead Time dB/dt Predictions with the Space Weather Modeling Framework

NASA Astrophysics Data System (ADS)

Welling, D. T.; Manchester, W.; Savani, N.; Sokolov, I.; van der Holst, B.; Jin, M.; Toth, G.; Liemohn, M. W.; Gombosi, T. I.

2017-12-01

The future of space weather prediction depends on the community's ability to predict L1 values from observations of the solar atmosphere, which can yield hours of lead time. While both empirical and physics-based L1 forecast methods exist, it is not yet known if this nascent capability can translate to skilled dB/dt forecasts at the Earth's surface. This paper shows results for the first forecast-quality, solar-atmosphere-to-Earth's-surface dB/dt predictions. Two methods are used to predict solar wind and IMF conditions at L1 for several real-world coronal mass ejection events. The first method is an empirical and observationally based system to estimate the plasma characteristics. The magnetic field predictions are based on the Bz4Cast system which assumes that the CME has a cylindrical flux rope geometry locally around Earth's trajectory. The remaining plasma parameters of density, temperature and velocity are estimated from white-light coronagraphs via a variety of triangulation methods and forward based modelling. The second is a first-principles-based approach that combines the Eruptive Event Generator using Gibson-Low configuration (EEGGL) model with the Alfven Wave Solar Model (AWSoM). EEGGL specifies parameters for the Gibson-Low flux rope such that it erupts, driving a CME in the coronal model that reproduces coronagraph observations and propagates to 1AU. The resulting solar wind predictions are used to drive the operational Space Weather Modeling Framework (SWMF) for geospace. Following the configuration used by NOAA's Space Weather Prediction Center, this setup couples the BATS-R-US global magnetohydromagnetic model to the Rice Convection Model (RCM) ring current model and a height-integrated ionosphere electrodynamics model. The long lead time predictions of dB/dt are compared to model results that are driven by L1 solar wind observations. Both are compared to real-world observations from surface magnetometers at a variety of geomagnetic latitudes. Metrics are calculated to examine how the simulated solar wind drivers impact forecast skill. These results illustrate the current state of long-lead-time forecasting and the promise of this technology for operational use.

Modelling 1-minute directional observations of the global irradiance.

NASA Astrophysics Data System (ADS)

Thejll, Peter; Pagh Nielsen, Kristian; Andersen, Elsa; Furbo, Simon

2016-04-01

Direct and diffuse irradiances from the sky has been collected at 1-minute intervals for about a year from the experimental station at the Technical University of Denmark for the IEA project "Solar Resource Assessment and Forecasting". These data were gathered by pyrheliometers tracking the Sun, as well as with apertured pyranometers gathering 1/8th and 1/16th of the light from the sky in 45 degree azimuthal ranges pointed around the compass. The data are gathered in order to develop detailed models of the potentially available solar energy and its variations at high temporal resolution in order to gain a more detailed understanding of the solar resource. This is important for a better understanding of the sub-grid scale cloud variation that cannot be resolved with climate and weather models. It is also important for optimizing the operation of active solar energy systems such as photovoltaic plants and thermal solar collector arrays, and for passive solar energy and lighting to buildings. We present regression-based modelling of the observed data, and focus, here, on the statistical properties of the model fits. Using models based on the one hand on what is found in the literature and on physical expectations, and on the other hand on purely statistical models, we find solutions that can explain up to 90% of the variance in global radiation. The models leaning on physical insights include terms for the direct solar radiation, a term for the circum-solar radiation, a diffuse term and a term for the horizon brightening/darkening. The purely statistical model is found using data- and formula-validation approaches picking model expressions from a general catalogue of possible formulae. The method allows nesting of expressions, and the results found are dependent on and heavily constrained by the cross-validation carried out on statistically independent testing and training data-sets. Slightly better fits -- in terms of variance explained -- is found using the purely statistical fitting/searching approach. We describe the methods applied, results found, and discuss the different potentials of the physics- and statistics-only based model-searches.

A New SATIRE-S Spectral Solar Irradiance Reconstruction for Solar Cycles 21-23 and Its Implications for Stratospheric Ozone*

NASA Astrophysics Data System (ADS)

Ball, William T.; Krivova, Natalie A.; Unruh, Yvonne C.; Haigh, Joanna D.; Solanki, Sami K.

2014-11-01

We present a revised and extended total and spectral solar irradiance (SSI) reconstruction, which includes a wavelength-dependent uncertainty estimate, spanning the last three solar cycles using the SATIRE-S model. The SSI reconstruction covers wavelengths between 115 and 160,000 nm and all dates between August 1974 and October 2009. This represents the first full-wavelength SATIRE-S reconstruction to cover the last three solar cycles without data gaps and with an uncertainty estimate. SATIRE-S is compared with the NRLSSI model and SORCE/SOLSTICE ultraviolet (UV) observations. SATIRE-S displays similar cycle behaviour to NRLSSI for wavelengths below 242 nm and almost twice the variability between 242 and 310 nm. During the decline of last solar cycle, between 2003 and 2008, SSI from SORCE/SOLSTICE version 12 and 10 typically displays more than three times the variability of SATIRE-S between 200 and 300 nm. All three datasets are used to model changes in stratospheric ozone within a 2D atmospheric model for a decline from high solar activity to solar minimum. The different flux changes result in different modelled ozone trends. Using NRLSSI leads to a decline in mesospheric ozone, while SATIRE-S and SORCE/SOLSTICE result in an increase. Recent publications have highlighted increases in mesospheric ozone when considering version 10 SORCE/SOLSTICE irradiances. The recalibrated SORCE/SOLSTICE version 12 irradiances result in a much smaller mesospheric ozone response than when using version 10 and now similar in magnitude to SATIRE-S. This shows that current knowledge of variations in spectral irradiance is not sufficient to warrant robust conclusions concerning the impact of solar variability on the atmosphere and climate.

Improvement of solar-cycle prediction: Plateau of solar axial dipole moment

NASA Astrophysics Data System (ADS)

Iijima, H.; Hotta, H.; Imada, S.; Kusano, K.; Shiota, D.

2017-11-01

Aims: We report the small temporal variation of the axial dipole moment near the solar minimum and its application to the solar-cycle prediction by the surface flux transport (SFT) model. Methods: We measure the axial dipole moment using the photospheric synoptic magnetogram observed by the Wilcox Solar Observatory (WSO), the ESA/NASA Solar and Heliospheric Observatory Michelson Doppler Imager (MDI), and the NASA Solar Dynamics Observatory Helioseismic and Magnetic Imager (HMI). We also use the SFT model for the interpretation and prediction of the observed axial dipole moment. Results: We find that the observed axial dipole moment becomes approximately constant during the period of several years before each cycle minimum, which we call the axial dipole moment plateau. The cross-equatorial magnetic flux transport is found to be small during the period, although a significant number of sunspots are still emerging. The results indicate that the newly emerged magnetic flux does not contribute to the build up of the axial dipole moment near the end of each cycle. This is confirmed by showing that the time variation of the observed axial dipole moment agrees well with that predicted by the SFT model without introducing new emergence of magnetic flux. These results allow us to predict the axial dipole moment at the Cycle 24/25 minimum using the SFT model without introducing new flux emergence. The predicted axial dipole moment at the Cycle 24/25 minimum is 60-80 percent of Cycle 23/24 minimum, which suggests the amplitude of Cycle 25 is even weaker than the current Cycle 24. Conclusions: The plateau of the solar axial dipole moment is an important feature for the longer-term prediction of the solar cycle based on the SFT model.

A PROPOSED PARADIGM FOR SOLAR CYCLE DYNAMICS MEDIATED VIA TURBULENT PUMPING OF MAGNETIC FLUX IN BABCOCK–LEIGHTON-TYPE SOLAR DYNAMOS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hazra, Soumitra; Nandy, Dibyendu

At present, the Babcock–Leighton flux transport solar dynamo models appear to be the most promising models for explaining diverse observational aspects of the sunspot cycle. The success of these flux transport dynamo models is largely dependent upon a single-cell meridional circulation with a deep equatorward component at the base of the Sun’s convection zone. However, recent observations suggest that the meridional flow may in fact be very shallow (confined to the top 10% of the Sun) and more complex than previously thought. Taken together, these observations raise serious concerns on the validity of the flux transport paradigm. By accounting formore » the turbulent pumping of magnetic flux, as evidenced in magnetohydrodynamic simulations of solar convection, we demonstrate that flux transport dynamo models can generate solar-like magnetic cycles even if the meridional flow is shallow. Solar-like periodic reversals are recovered even when meridional circulation is altogether absent. However, in this case, the solar surface magnetic field dynamics does not extend all the way to the polar regions. Very importantly, our results demonstrate that the Parker–Yoshimura sign rule for dynamo wave propagation can be circumvented in Babcock–Leighton dynamo models by the latitudinal component of turbulent pumping, which can generate equatorward propagating sunspot belts in the absence of a deep, equatorward meridional flow. We also show that variations in turbulent pumping coefficients can modulate the solar cycle amplitude and periodicity. Our results suggest the viability of an alternate magnetic flux transport paradigm—mediated via turbulent pumping—for sustaining solar-stellar dynamo action.« less

Pickup Protons: Comparisons using the Three-Dimensional MHD HHMS-PI model and Ulysses SWICS Measurements

NASA Technical Reports Server (NTRS)

Intriligator, Devrie S.; Detman, Thomas; Gloecker, George; Gloeckler, Christine; Dryer, Murray; Sun, Wei; Intriligator, James; Deehr, Charles

2012-01-01

We report the first comparisons of pickup proton simulation results with in situ measurements of pickup protons obtained by the SWICS instrument on Ulysses. Simulations were run using the three dimensional (3D) time-dependent Hybrid Heliospheric Modeling System with Pickup Protons (HHMS-PI). HHMS-PI is an MHD solar wind model, expanded to include the basic physics of pickup protons from neutral hydrogen that drifts into the heliosphere from the local interstellar medium. We use the same model and input data developed by Detman et al. (2011) to now investigate the pickup protons. The simulated interval of 82 days in 2003 2004, includes both quiet solar wind (SW) and also the October November 2003 solar events (the Halloween 2003 solar storms). The HHMS-PI pickup proton simulations generally agree with the SWICS measurements and the HHMS-PI simulated solar wind generally agrees with SWOOPS (also on Ulysses) measurements. Many specific features in the observations are well represented by the model. We simulated twenty specific solar events associated with the Halloween 2003 storm. We give the specific values of the solar input parameters for the HHMS-PI simulations that provide the best combined agreement in the times of arrival of the solar-generated shocks at both ACE and Ulysses. We show graphical comparisons of simulated and observed parameters, and we give quantitative measures of the agreement of simulated with observed parameters. We suggest that some of the variations in the pickup proton density during the Halloween 2003 solar events may be attributed to depletion of the inflowing local interstellar medium (LISM) neutral hydrogen (H) caused by its increased conversion to pickup protons in the immediately preceding shock.

Aeroheating Thermal Model Correlation for Mars Global Surveyor (MGS) Solar Array

NASA Technical Reports Server (NTRS)

Amundsen, Ruth M.; Dec, John A.; George, Benjamin E.

2003-01-01

The Mars Global Surveyor (MGS) Spacecraft made use of aerobraking to gradually reduce its orbit period from a highly elliptical insertion orbit to its final science orbit. Aerobraking produces a high heat load on the solar arrays, which have a large surface area exposed to the airflow and relatively low mass. To accurately model the complex behavior during aerobraking, the thermal analysis needed to be tightly coupled to the spatially varying, time dependent aerodynamic heating. Also, the thermal model itself needed to accurately capture the behavior of the solar array and its response to changing heat load conditions. The correlation of the thermal model to flight data allowed a validation of the modeling process, as well as information on what processes dominate the thermal behavior. Correlation in this case primarily involved detailing the thermal sensor nodes, using as-built mass to modify material property estimates, refining solar cell assembly properties, and adding detail to radiation and heat flux boundary conditions. This paper describes the methods used to develop finite element thermal models of the MGS solar array and the correlation of the thermal model to flight data from the spacecraft drag passes. Correlation was made to data from four flight thermal sensors over three of the early drag passes. Good correlation of the model was achieved, with a maximum difference between the predicted model maximum and the observed flight maximum temperature of less than 5%. Lessons learned in the correlation of this model assisted in validating a similar model and method used for the Mars Odyssey solar array aeroheating analysis, which were used during onorbit operations.

Mathematical model of solar radiation based on climatological data from NASA SSE

NASA Astrophysics Data System (ADS)

Obukhov, S. G.; Plotnikov, I. A.; Masolov, V. G.

2018-05-01

An original model of solar radiation arriving at the arbitrarily oriented surface has been developed. The peculiarity of the model is that it uses numerical values of the atmospheric transparency index and the surface albedo from the NASA SSE database as initial data. The model is developed in the MatLab/Simulink environment to predict the main characteristics of solar radiation for any geographical point in Russia, including those for territories with no regular actinometric observations.

Collisionless solar wind protons: A comparison of kinetic and hydrodynamic descriptions

NASA Technical Reports Server (NTRS)

Leer, E.; Holzer, T. E.

1971-01-01

Kinetic and hydrodynamic descriptions of a collisionless solar wind proton gas are compared. Heat conduction and viscosity are neglected in the hydrodynamic formulation but automatically included in the kinetic formulation. The results of the two models are very nearly the same, indicating that heat conduction and viscosity are not important in the solar wind proton gas beyond about 0.1 AU. It is concluded that the hydrodynamic equations provide a valid description of the collisionless solar wind protons, and hence that future models of the quiet solar wind should be based on a hydrodynamic formulation.

The Impact of Different Absolute Solar Irradiance Values on Current Climate Model Simulations

NASA Technical Reports Server (NTRS)

Rind, David H.; Lean, Judith L.; Jonas, Jeffrey

2014-01-01

Simulations of the preindustrial and doubled CO2 climates are made with the GISS Global Climate Middle Atmosphere Model 3 using two different estimates of the absolute solar irradiance value: a higher value measured by solar radiometers in the 1990s and a lower value measured recently by the Solar Radiation and Climate Experiment. Each of the model simulations is adjusted to achieve global energy balance; without this adjustment the difference in irradiance produces a global temperature change of 0.48C, comparable to the cooling estimated for the Maunder Minimum. The results indicate that by altering cloud cover the model properly compensates for the different absolute solar irradiance values on a global level when simulating both preindustrial and doubled CO2 climates. On a regional level, the preindustrial climate simulations and the patterns of change with doubled CO2 concentrations are again remarkably similar, but there are some differences. Using a higher absolute solar irradiance value and the requisite cloud cover affects the model's depictions of high-latitude surface air temperature, sea level pressure, and stratospheric ozone, as well as tropical precipitation. In the climate change experiments it leads to an underestimation of North Atlantic warming, reduced precipitation in the tropical western Pacific, and smaller total ozone growth at high northern latitudes. Although significant, these differences are typically modest compared with the magnitude of the regional changes expected for doubled greenhouse gas concentrations. Nevertheless, the model simulations demonstrate that achieving the highest possible fidelity when simulating regional climate change requires that climate models use as input the most accurate (lower) solar irradiance value.

The interpretation of hard X-ray polarization measurements in solar flares

NASA Technical Reports Server (NTRS)

Leach, J.; Emslie, A. G.; Petrosian, V.

1983-01-01

Observations of polarization of moderately hard X-rays in solar flares are reviewed and compared with the predictions of recent detailed modeling of hard X-ray bremsstrahlung production by non-thermal electrons. The recent advances in the complexity of the modeling lead to substantially lower predicted polarizations than in earlier models and more fully highlight how various parameters play a role in determining the polarization of the radiation field. The new predicted polarizations are comparable to those predicted by thermal modeling of solar flare hard X-ray production, and both are in agreement with the observations. In the light of these results, new polarization observations with current generation instruments are proposed which could be used to discriminate between non-thermal and thermal models of hard X-ray production in solar flares.

The Development of a New Model of Solar EUV Irradiance Variability

NASA Technical Reports Server (NTRS)

Warren, Harry; Wagner, William J. (Technical Monitor)

2002-01-01

The goal of this research project is the development of a new model of solar EUV (Extreme Ultraviolet) irradiance variability. The model is based on combining differential emission measure distributions derived from spatially and spectrally resolved observations of active regions, coronal holes, and the quiet Sun with full-disk solar images. An initial version of this model was developed with earlier funding from NASA. The new version of the model developed with this research grant will incorporate observations from SoHO as well as updated compilations of atomic data. These improvements will make the model calculations much more accurate.

Modeling the heliolatitudinal gradient of the solar wind parameters with exact MHD solutions

NASA Technical Reports Server (NTRS)

Lima, J. J. G.; Tsinganos, K.

1995-01-01

The heliolatitudinal dependence of observations of the solar wind macroscopic quantities such as the averaged proton speed, density and the mass and momentum flux are modeled. The published observations covering the last two and a half solar cycles, are obtained either via the technique of interplanetary scintillations for the last 2 solar cycles (1970-1990), or, from the plasma experiment aboard the ULYSSES spacecraft for the recent period 1990-1994. Exact, two dimensional solutions of the full set of the steady MHD equations are used which are obtained through a nonlinear separation of the variables in the MHD equations. The three parameters emerging from the solutions are fixed from these observations, as well as from observations of the solar rotation. It is found that near solar maximum the solar wind speed is uniformly low, around the 400 km/s over a wide range of latitudes. On the other hand, during solar minimum and the declining phase of the solar activity cycle, there is a strong heliolatitudinal gradient in proton speed between 400-800 from equator to pole. This modeling also agrees with previous findings that the gradient in wind speed with the latitude is offset by a gradient in density such that the mass and momentum flux vary relatively little.

Multi-Wavelength Imaging of Solar Plasma - High-Beta Disruption Model of Solar Flares -

NASA Astrophysics Data System (ADS)

Shibasaki, Kiyoto

Solar atmosphere is filled with plasma and magnetic field. Activities in the atmosphere are due to plasma instabilities in the magnetic field. To understand the physical mechanisms of activities / instabilities, it is necessary to know the physical conditions of magnetized plasma, such as temperature, density, magnetic field, and their spatial structures and temporal developments. Multi-wavelength imaging is essential for this purpose. Imaging observations of the Sun at microwave, X-ray, EUV and optical ranges are routinely going on. Due to free exchange of original data among solar physics and related field communities, we can easily combine images covering wide range of spectrum. Even under such circumstances, we still do not understand the cause of activities in the solar atmosphere well. The current standard model of solar activities is based on magnetic reconnection: release of stored magnetic energy by reconnection is the cause of solar activities on the Sun such as solar flares. However, recent X-ray, EUV and microwave observations with high spatial and temporal resolution show that dense plasma is involved in activities from the beginning. Based on these observations, I propose a high-beta model of solar activities, which is very similar to high-beta disruptions in magnetically confined fusion experiments.

Lighting Condition Analysis for Mars' Moon Phobos

NASA Technical Reports Server (NTRS)

Li, Zu Qun; de Carufel, Guy; Crues, Edwin Z.; Bielski, Paul

2016-01-01

This study used high fidelity computer simulation to investigate the lighting conditions, specifically the solar radiation flux over the surface, on Phobos. Ephemeris data from the Jet Propulsion Laboratory (JPL) DE405 model was used to model the state of the Sun, Earth, Moon, and Mars. An occultation model was developed to simulate Phobos' self-shadowing and its solar eclipses by Mars. The propagated Phobos state was compared with data from JPL's Horizon system to ensure the accuracy of the result. Results for Phobos lighting conditions over one Martian year are presented, which include the duration of solar eclipses, average solar radiation intensity, surface exposure time, and radiant exposure for both sun tracking and fixed solar arrays. The results show that: Phobos' solar eclipse time varies throughout the Martian year, with longer eclipse durations during the Martian northern spring and fall seasons and no eclipses during the Martian northern summer and winter seasons; solar radiation intensity is close to minimum in late spring and close to maximum in late fall; exposure time per orbit is relatively constant over the surface during the spring and fall but varies with latitude during the summer and winter; and Sun tracking solar arrays generate more energy than a fixed solar array. A usage example of the result is also present in this paper to demonstrate the utility.

Design and Optimization of Copper Indium Gallium Selenide Thin Film Solar Cells

DTIC Science & Technology

2015-09-01

determined by the intensity of the illumination that the solar cell is exposed to. The diffusion lengths L can be further defined by n n nL D τ...absorbers with graded Ga concentrations. (3) Back Contact Model Models for back contact silicon solar cells have been created with results that closely...Radiation. New York, NY: Academic Press, 2012. [12] B. Richards, “Enhancing the performance of silicon solar cells via the application of passive

Optimum systems design with random input and output applied to solar water heating

NASA Astrophysics Data System (ADS)

Abdel-Malek, L. L.

1980-03-01

Solar water heating systems are evaluated. Models were developed to estimate the percentage of energy supplied from the Sun to a household. Since solar water heating systems have random input and output queueing theory, birth and death processes were the major tools in developing the models of evaluation. Microeconomics methods help in determining the optimum size of the solar water heating system design parameters, i.e., the water tank volume and the collector area.

Statistical Similarities Between WSA-ENLIL+Cone Model and MAVEN in Situ Observations From November 2014 to March 2016

NASA Astrophysics Data System (ADS)

Lentz, C. L.; Baker, D. N.; Jaynes, A. N.; Dewey, R. M.; Lee, C. O.; Halekas, J. S.; Brain, D. A.

2018-02-01

Normal solar wind flows and intense solar transient events interact directly with the upper Martian atmosphere due to the absence of an intrinsic global planetary magnetic field. Since the launch of the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission, there are now new means to directly observe solar wind parameters at the planet's orbital location for limited time spans. Due to MAVEN's highly elliptical orbit, in situ measurements cannot be taken while MAVEN is inside Mars' magnetosheath. To model solar wind conditions during these atmospheric and magnetospheric passages, this research project utilized the solar wind forecasting capabilities of the WSA-ENLIL+Cone model. The model was used to simulate solar wind parameters that included magnetic field magnitude, plasma particle density, dynamic pressure, proton temperature, and velocity during a four Carrington rotation-long segment. An additional simulation that lasted 18 Carrington rotations was then conducted. The precision of each simulation was examined for intervals when MAVEN was in the upstream solar wind, that is, with no exospheric or magnetospheric phenomena altering in situ measurements. It was determined that generalized, extensive simulations have comparable prediction capabilities as shorter, more comprehensive simulations. Generally, this study aimed to quantify the loss of detail in long-term simulations and to determine if extended simulations can provide accurate, continuous upstream solar wind conditions when there is a lack of in situ measurements.

Quantized Advantages to a Proposed Satellite at L5 from Simulated Synoptic Magnetograms

NASA Astrophysics Data System (ADS)

Schwarz, A. M.; Petrie, G. J. D.

2017-12-01

The dependency the Earth and its inhabitants have on the Sun is delicate and complex and sometimes dangerous. At the NSO, we provide 24/7 coverage of the full-disk solar magnetic field used in solar forecasting, however this only includes data from the Sun's Earth facing side. Ideally we would like to have constant coverage of the entire solar surface, however we are limited in our solar viewing angle. Our project attempts to quantify the advantages of full-disk magnetograms from a proposed satellite at L5. With instrumentation at L5 we would have an additional 60 degrees of solar surface coverage not seen from Earth. These 60 degrees crucially contain the solar longitudes that are about to rotate towards Earth. Using a full-surface flux-transport model of the evolving solar photospheric field, I created a simulation of full-disk observations from Earth and L5. Using standard solar forecasting tools we quantify the relative accuracy of the Earth-Only and Earth plus L5 forecasts relative to the "ground truth" of the full surface field model, the ideal case. My results gauge exactly how much polar coverage is improved, contrast the spherical multipoles of each model, and use a Potential-Field Source-Surface (PFSS) magnetic field analysis model to find comparisons in the neutral lines and open field coverage.

A model for straight and helical solar jets: II. Parametric study of the plasma beta.

PubMed

Pariat, E; Dalmasse, K; DeVore, C R; Antiochos, S K; Karpen, J T

2016-12-01

Jets are dynamic, impulsive, well-collimated plasma events that develop at many different scales and in different layers of the solar atmosphere. Jets are believed to be induced by magnetic reconnection, a process central to many astrophysical phenomena. Within the solar atmosphere, jet-like events develop in many different environments, e.g., in the vicinity of active regions as well as in coronal holes, and at various scales, from small photospheric spicules to large coronal jets. In all these events, signatures of helical structure and/or twisting/rotating motions are regularly observed. The present study aims to establish that a single model can generally reproduce the observed properties of these jet-like events. In this study, using our state-of-the-art numerical solver ARMS, we present a parametric study of a numerical tridimensional magnetohydrodynamic (MHD) model of solar jet-like events. Within the MHD paradigm, we study the impact of varying the atmospheric plasma β on the generation and properties of solar-like jets. The parametric study validates our model of jets for plasma β ranging from 10 -3 to 1, typical of the different layers and magnetic environments of the solar atmosphere. Our model of jets can robustly explain the generation of helical solar jet-like events at various β ≤ 1. This study introduces the new original result that the plasma β modifies the morphology of the helical jet, explaining the different observed shapes of jets at different scales and in different layers of the solar atmosphere. Our results allow us to understand the energisation, triggering, and driving processes of jet-like events. Our model allows us to make predictions of the impulsiveness and energetics of jets as determined by the surrounding environment, as well as the morphological properties of the resulting jets.

Ensemble Kalman Filter Data Assimilation in a Solar Dynamo Model

NASA Astrophysics Data System (ADS)

Dikpati, M.

2017-12-01

Despite great advancement in solar dynamo models since the first model by Parker in 1955, there remain many challenges in the quest to build a dynamo-based prediction scheme that can accurately predict the solar cycle features. One of these challenges is to implement modern data assimilation techniques, which have been used in the oceanic and atmospheric prediction models. Development of data assimilation in solar models are in the early stages. Recently, observing system simulation experiments (OSSE's) have been performed using Ensemble Kalman Filter data assimilation, in the framework of Data Assimilation Research Testbed of NCAR (NCAR-DART), for estimating parameters in a solar dynamo model. I will demonstrate how the selection of ensemble size, number of observations, amount of error in observations and the choice of assimilation interval play important role in parameter estimation. I will also show how the results of parameter reconstruction improve when accuracy in low-latitude observations is increased, despite large error in polar region data. I will then describe how implementation of data assimilation in a solar dynamo model can bring more accuracy in the prediction of polar fields in North and South hemispheres during the declining phase of cycle 24. Recent evidence indicates that the strength of the Sun's polar field during the cycle minima might be a reliable predictor for the next sunspot cycle's amplitude; therefore it is crucial to accurately predict the polar field strength and pattern.

A Topside Equatorial Ionospheric Density and Composition Climatology During and After Extreme Solar Minimum

NASA Technical Reports Server (NTRS)

Klenzing, J. H.; Simoes, F.; Ivanov, S.; Heelis, R. A.; Bilitza, D.; Pfaff, R. F.; Rowland, D. E.

2011-01-01

During the recent solar minimum, solar activity reached the lowest levels observed during the space age. This extremely low solar activity has accompanied a number of unexpected observations in the Earth's ionosphere and thermosphere when compared to previous solar minima. Among these are the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Climatological altitude profiles of ion density and composition measurements near the magnetic dip equator are constructed from the C/NOFS satellite to characterize the shape of the top side ionosphere during the recent solar minimum and into the new solar cycle. The variation of the profiles with respect to local time, season, and solar activity are compared to the IRI-2007 model. Building on initial results reported by Heelis et al. [2009], here we describe the extent of the contracted ionosphere, which is found to persist throughout 2009. The shape of the ionosphere during 2010 is found to be consistent with observations from previous solar minima.

Modeling the Performance Limitations and Prospects of Perovskite/Si Tandem Solar Cells under Realistic Operating Conditions

PubMed Central

2017-01-01

Perovskite/Si tandem solar cells have the potential to considerably out-perform conventional solar cells. Under standard test conditions, perovskite/Si tandem solar cells already outperform the Si single junction. Under realistic conditions, however, as we show, tandem solar cells made from current record cells are hardly more efficient than the Si cell alone. We model the performance of realistic perovskite/Si tandem solar cells under real-world climate conditions, by incorporating parasitic cell resistances, nonradiative recombination, and optical losses into the detailed-balance limit. We show quantitatively that when optimizing these parameters in the perovskite top cell, perovskite/Si tandem solar cells could reach efficiencies above 38% under realistic conditions, even while leaving the Si cell untouched. Despite the rapid efficiency increase of perovskite solar cells, our results emphasize the need for further material development, careful device design, and light management strategies, all necessary for highly efficient perovskite/Si tandem solar cells. PMID:28920081

Modeling the Performance Limitations and Prospects of Perovskite/Si Tandem Solar Cells under Realistic Operating Conditions.

PubMed

Futscher, Moritz H; Ehrler, Bruno

2017-09-08

Perovskite/Si tandem solar cells have the potential to considerably out-perform conventional solar cells. Under standard test conditions, perovskite/Si tandem solar cells already outperform the Si single junction. Under realistic conditions, however, as we show, tandem solar cells made from current record cells are hardly more efficient than the Si cell alone. We model the performance of realistic perovskite/Si tandem solar cells under real-world climate conditions, by incorporating parasitic cell resistances, nonradiative recombination, and optical losses into the detailed-balance limit. We show quantitatively that when optimizing these parameters in the perovskite top cell, perovskite/Si tandem solar cells could reach efficiencies above 38% under realistic conditions, even while leaving the Si cell untouched. Despite the rapid efficiency increase of perovskite solar cells, our results emphasize the need for further material development, careful device design, and light management strategies, all necessary for highly efficient perovskite/Si tandem solar cells.

Topside Equatorial Ionospheric Density and Composition During and After Extreme Solar Minimum

NASA Technical Reports Server (NTRS)

Klenzing, J.; Simoes, F.; Ivanov, S.; Heelis, R. A.; Bilitza, D.; Pfaff, R.; Rowland, D.

2011-01-01

During the recent solar minimum, solar activity reached the lowest levels observed during the space age. This extremely low solar activity has accompanied a number of unexpected observations in the Earth s ionosphere-thermosphere system when compared to previous solar minima. Among these are the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Altitude profiles of ion density and composition measurements near the magnetic dip equator are constructed from the Communication/Navigation Outage Forecast System (C/NOFS) satellite to characterize the shape of the topside ionosphere during the recent solar minimum and into the new solar cycle. The variation of the profiles with respect to local time, season, and solar activity are compared to the IRI-2007 model. Building on initial results reported by Heelis et al. (2009), here we describe the extent of the contracted ionosphere, which is found to persist throughout 2009. The shape of the ionosphere during 2010 is found to be consistent with observations from previous solar minima.

Solar forcing synchronizes decadal North Atlantic climate variability.

PubMed

Thiéblemont, Rémi; Matthes, Katja; Omrani, Nour-Eddine; Kodera, Kunihiko; Hansen, Felicitas

2015-09-15

Quasi-decadal variability in solar irradiance has been suggested to exert a substantial effect on Earth's regional climate. In the North Atlantic sector, the 11-year solar signal has been proposed to project onto a pattern resembling the North Atlantic Oscillation (NAO), with a lag of a few years due to ocean-atmosphere interactions. The solar/NAO relationship is, however, highly misrepresented in climate model simulations with realistic observed forcings. In addition, its detection is particularly complicated since NAO quasi-decadal fluctuations can be intrinsically generated by the coupled ocean-atmosphere system. Here we compare two multi-decadal ocean-atmosphere chemistry-climate simulations with and without solar forcing variability. While the experiment including solar variability simulates a 1-2-year lagged solar/NAO relationship, comparison of both experiments suggests that the 11-year solar cycle synchronizes quasi-decadal NAO variability intrinsic to the model. The synchronization is consistent with the downward propagation of the solar signal from the stratosphere to the surface.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, X.; Florinski, V.

We present a new model that couples galactic cosmic-ray (GCR) propagation with magnetic turbulence transport and the MHD background evolution in the heliosphere. The model is applied to the problem of the formation of corotating interaction regions (CIRs) during the last solar minimum from the period between 2007 and 2009. The numerical model simultaneously calculates the large-scale supersonic solar wind properties and its small-scale turbulent content from 0.3 au to the termination shock. Cosmic rays are then transported through the background, and thus computed, with diffusion coefficients derived from the solar wind turbulent properties, using a stochastic Parker approach. Ourmore » results demonstrate that GCR variations depend on the ratio of diffusion coefficients in the fast and slow solar winds. Stream interfaces inside the CIRs always lead to depressions of the GCR intensity. On the other hand, heliospheric current sheet (HCS) crossings do not appreciably affect GCR intensities in the model, which is consistent with the two observations under quiet solar wind conditions. Therefore, variations in diffusion coefficients associated with CIR stream interfaces are more important for GCR propagation than the drift effects of the HCS during a negative solar minimum.« less

Physics-based Space Weather Forecasting in the Project for Solar-Terrestrial Environment Prediction (PSTEP) in Japan

NASA Astrophysics Data System (ADS)

Kusano, K.

2016-12-01

Project for Solar-Terrestrial Environment Prediction (PSTEP) is a Japanese nation-wide research collaboration, which was recently launched. PSTEP aims to develop a synergistic interaction between predictive and scientific studies of the solar-terrestrial environment and to establish the basis for next-generation space weather forecasting using the state-of-the-art observation systems and the physics-based models. For this project, we coordinate the four research groups, which develop (1) the integration of space weather forecast system, (2) the physics-based solar storm prediction, (3) the predictive models of magnetosphere and ionosphere dynamics, and (4) the model of solar cycle activity and its impact on climate, respectively. In this project, we will build the coordinated physics-based model to answer the fundamental questions concerning the onset of solar eruptions and the mechanism for radiation belt dynamics in the Earth's magnetosphere. In this paper, we will show the strategy of PSTEP, and discuss about the role and prospect of the physics-based space weather forecasting system being developed by PSTEP.

A MODEL OF MAGNETIC BRAKING OF SOLAR ROTATION THAT SATISFIES OBSERVATIONAL CONSTRAINTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Denissenkov, Pavel A., E-mail: pavel.denisenkov@gmail.co

The model of magnetic braking of solar rotation considered by Charbonneau and MacGregor has been modified so that it is able to reproduce for the first time the rotational evolution of both the fastest and slowest rotators among solar-type stars in open clusters of different ages, without coming into conflict with other observational constraints, such as the time evolution of the atmospheric Li abundance in solar twins and the thinness of the solar tachocline. This new model assumes that rotation-driven turbulent diffusion, which is thought to amplify the viscosity and magnetic diffusivity in stellar radiative zones, is strongly anisotropic withmore » the horizontal components of the transport coefficients strongly dominating over those in the vertical direction. Also taken into account is the poloidal field decay that helps to confine the width of the tachocline at the solar age. The model's properties are investigated by numerically solving the azimuthal components of the coupled momentum and magnetic induction equations in two dimensions using a finite element method.« less

Potential of Solar Energy in Kota Kinabalu, Sabah: An Estimate Using a Photovoltaic System Model

NASA Astrophysics Data System (ADS)

Markos, F. M.; Sentian, J.

2016-04-01

Solar energy is becoming popular as an alternative renewable energy to conventional energy source, particularly in the tropics, where duration and intensity of solar radiation are longer. This study is to assess the potential of solar energy generated from solar for Kota Kinabalu, a rapidly developing city in the State of Sabah, Malaysia. A year data of solar radiation was obtained using pyranometer, which was located at Universiti Malaysia Sabah (6.0367° N, 116.1186° E). It was concluded that the annual average solar radiation received in Kota Kinabalu was 182 W/m2. In estimating the potential energy generated from solar for Kota Kinabalu city area, a photovoltaic (PV) system model was used. The results showed that, Kota Kinabalu is estimated to produce 29,794 kWh/m2 of electricity from the solar radiation received in a year. This is equivalent to 0.014 MW of electricity produced just by using one solar panel. Considering the power demand in Sabah by 2020 is 1,331 MW, this model showed that the solar energy can contribute around 4% of energy for power demand, with 1 MW capacity of the PV system. 1 MW of PV system installation will require about 0.0328% from total area of the city. This assessment could suggest that, exploration for solar power energy as an alternative source of renewable energy in the city can be optimised and designed to attain significant higher percentage of contribution to the energy demand in the state.

The nature of solar brightness variations

NASA Astrophysics Data System (ADS)

Shapiro, A. I.; Solanki, S. K.; Krivova, N. A.; Cameron, R. H.; Yeo, K. L.; Schmutz, W. K.

2017-09-01

Determining the sources of solar brightness variations1,2, often referred to as solar noise3, is important because solar noise limits the detection of solar oscillations3, is one of the drivers of the Earth's climate system4,5 and is a prototype of stellar variability6,7—an important limiting factor for the detection of extrasolar planets. Here, we model the magnetic contribution to solar brightness variability using high-cadence8,9 observations from the Solar Dynamics Observatory (SDO) and the Spectral And Total Irradiance REconstruction (SATIRE)10,11 model. The brightness variations caused by the constantly evolving cellular granulation pattern on the solar surface were computed with the Max Planck Institute for Solar System Research (MPS)/University of Chicago Radiative Magnetohydrodynamics (MURaM)12 code. We found that the surface magnetic field and granulation can together precisely explain solar noise (that is, solar variability excluding oscillations) on timescales from minutes to decades, accounting for all timescales that have so far been resolved or covered by irradiance measurements. We demonstrate that no other sources of variability are required to explain the data. Recent measurements of Sun-like stars by the COnvection ROtation and planetary Transits (CoRoT)13 and Kepler14 missions uncovered brightness variations similar to that of the Sun, but with a much wider variety of patterns15. Our finding that solar brightness variations can be replicated in detail with just two well-known sources will greatly simplify future modelling of existing CoRoT and Kepler as well as anticipated Transiting Exoplanet Survey Satellite16 and PLAnetary Transits and Oscillations of stars (PLATO)17 data.

The origin of Total Solar Irradiance variability on timescales less than a day

NASA Astrophysics Data System (ADS)

Shapiro, Alexander; Krivova, Natalie; Schmutz, Werner; Solanki, Sami K.; Leng Yeo, Kok; Cameron, Robert; Beeck, Benjamin

2016-07-01

Total Solar Irradiance (TSI) varies on timescales from minutes to decades. It is generally accepted that variability on timescales of a day and longer is dominated by solar surface magnetic fields. For shorter time scales, several additional sources of variability have been proposed, including convection and oscillation. However, available simplified and highly parameterised models could not accurately explain the observed variability in high-cadence TSI records. We employed the high-cadence solar imagery from the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory and the SATIRE (Spectral And Total Irradiance Reconstruction) model of solar irradiance variability to recreate the magnetic component of TSI variability. The recent 3D simulations of solar near-surface convection with MURAM code have been used to calculate the TSI variability caused by convection. This allowed us to determine the threshold timescale between TSI variability caused by the magnetic field and convection. Our model successfully replicates the TSI measurements by the PICARD/PREMOS radiometer which span the period of July 2010 to February 2014 at 2-minute cadence. Hence, we demonstrate that solar magnetism and convection can account for TSI variability at all timescale it has ever been measured (sans the 5-minute component from p-modes).

Reconstruction of solar spectral irradiance since the Maunder minimum

NASA Astrophysics Data System (ADS)

Krivova, N. A.; Vieira, L. E. A.; Solanki, S. K.

2010-12-01

Solar irradiance is the main external driver of the Earth's climate. Whereas the total solar irradiance is the main source of energy input into the climate system, solar UV irradiance exerts control over chemical and physical processes in the Earth's upper atmosphere. The time series of accurate irradiance measurements are, however, relatively short and limit the assessment of the solar contribution to the climate change. Here we reconstruct solar total and spectral irradiance in the range 115-160,000 nm since 1610. The evolution of the solar photospheric magnetic flux, which is a central input to the model, is appraised from the historical record of the sunspot number using a simple but consistent physical model. The model predicts an increase of 1.25 W/m2, or about 0.09%, in the 11-year averaged solar total irradiance since the Maunder minimum. Also, irradiance in individual spectral intervals has generally increased during the past four centuries, the magnitude of the trend being higher toward shorter wavelengths. In particular, the 11-year averaged Ly-α irradiance has increased by almost 50%. An exception is the spectral interval between about 1500 and 2500 nm, where irradiance has slightly decreased (by about 0.02%).

Polarity Comparison Between the Coronal PFSS Model Field and the Heliospheric Magnetic Field at 1 AU Over Solar Cycles 21-24

NASA Astrophysics Data System (ADS)

Koskela, J. S.; Virtanen, I. I.; Mursula, K.

2015-12-01

The solar coronal magnetic field forms an important link between the underlying source in the solar photosphere and the heliospheric magnetic field (HMF). The coronal field has traditionally been calculated from the photospheric observations using various magnetic field models between the photosphere and the corona, in particular the potential field source surface (PFSS) model. Despite its simplicity, the predictions of the PFSS model generally agree quite well with the heliospheric observations and match very well with the predictions of more elaborate models. We make here a detailed comparison between the predictions of the PFSS model with the HMF field observed at 1 AU. We use the photospheric field measured at the Wilcox Solar Observatory, SDO/HMI, SOHO/MDI and SOLIS, and the heliospheric magnetic field measurements at 1 AU collected within the OMNI 2 dataset. This database covers the solar cycles 21-24. We use different source surface distances and different numbers of harmonic components for the PFSS model. We find an optimum polarity match between the coronal field and the HMF for source surface distance of 3.5 Rs. Increasing the number of harmonic components beyond the quadrupole does not essentially improve polarity agreement, indicating that the large scale structure of the HMF at 1 AU is responsible for the agreement while the small scale structure is greatly modified between corona and 1 AU. We also discuss the solar cycle evolution of polarity match and find that the PFSS model prediction is most reliable during the declining phase of the solar cycle. We also find large differences in match percentage between northern and southern hemispheres during the times of systematic southward shift of the heliospheric current sheet (the Bashful ballerina).

Climate responses to SATIRE and SIM-based spectral solar forcing in a 3D atmosphere-ocean coupled GCM

NASA Astrophysics Data System (ADS)

Wen, Guoyong; Cahalan, Robert F.; Rind, David; Jonas, Jeffrey; Pilewskie, Peter; Wu, Dong L.; Krivova, Natalie A.

2017-03-01

We apply two reconstructed spectral solar forcing scenarios, one SIM (Spectral Irradiance Monitor) based, the other the SATIRE (Spectral And Total Irradiance REconstruction) modeled, as inputs to the GISS (Goddard Institute for Space Studies) GCMAM (Global Climate Middle Atmosphere Model) to examine climate responses on decadal to centennial time scales, focusing on quantifying the difference of climate response between the two solar forcing scenarios. We run the GCMAM for about 400 years with present day trace gas and aerosol for the two solar forcing inputs. We find that the SIM-based solar forcing induces much larger long-term response and 11-year variation in global averaged stratospheric temperature and column ozone. We find significant decreasing trends of planetary albedo for both forcing scenarios in the 400-year model runs. However the mechanisms for the decrease are very different. For SATIRE solar forcing, the decreasing trend of planetary albedo is associated with changes in cloud cover. For SIM-based solar forcing, without significant change in cloud cover on centennial and longer time scales, the apparent decreasing trend of planetary albedo is mainly due to out-of-phase variation in shortwave radiative forcing proxy (downwelling flux for wavelength >330 nm) and total solar irradiance (TSI). From the Maunder Minimum to present, global averaged annual mean surface air temperature has a response of 0.1 °C to SATIRE solar forcing compared to 0.04 °C to SIM-based solar forcing. For 11-year solar cycle, the global surface air temperature response has 3-year lagged response to either forcing scenario. The global surface air 11-year temperature response to SATIRE forcing is about 0.12 °C, similar to recent multi-model estimates, and comparable to the observational-based evidence. However, the global surface air temperature response to 11-year SIM-based solar forcing is insignificant and inconsistent with observation-based evidence.

Distributed PV Adoption in Maine Through 2021

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gagnon, Pieter; Sigrin, Ben

2015-11-06

NREL has used its dSolar (distributed solar) model to generate low-medium-high estimates of distributed PV adoption in Maine through 2021. This presentation gives a high-level overview of the model and modeling results.

Solar Wind Interaction with the Martian Upper Atmosphere at Early Mars/Extreme Solar Conditions

NASA Astrophysics Data System (ADS)

Dong, C.; Bougher, S. W.; Ma, Y.; Toth, G.; Lee, Y.; Nagy, A. F.; Tenishev, V.; Pawlowski, D. J.; Combi, M. R.

2014-12-01

The investigation of ion escape fluxes from Mars, resulting from the solar wind interaction with its upper atmosphere/ionosphere, is important due to its potential impact on the long-term evolution of Mars atmosphere (e.g., loss of water) over its history. In the present work, we adopt the 3-D Mars cold neutral atmosphere profiles (0 ~ 300 km) from the newly developed and validated Mars Global Ionosphere Thermosphere Model (M-GITM) and the 3-D hot oxygen profiles (100 km ~ 5 RM) from the exosphere Monte Carlo model Adaptive Mesh Particle Simulator (AMPS). We apply these 3-D model output fields into the 3-D BATS-R-US Mars multi-fluid MHD (MF-MHD) model (100 km ~ 20 RM) that can simulate the interplay between Mars upper atmosphere and solar wind by considering the dynamics of individual ion species. The multi-fluid MHD model solves separate continuity, momentum and energy equations for each ion species (H+, O+, O2+, CO2+). The M-GITM model together with the AMPS exosphere model take into account the effects of solar cycle and seasonal variations on both cold and hot neutral atmospheres. This feature allows us to investigate the corresponding effects on the Mars upper atmosphere ion escape by using a one-way coupling approach, i.e., both the M-GITM and AMPS model output fields are used as the input for the multi-fluid MHD model and the M-GITM is used as input into the AMPS exosphere model. In this study, we present M-GITM, AMPS, and MF-MHD calculations (1-way coupled) for 2.5 GYA conditions and/or extreme solar conditions for present day Mars (high solar wind velocities, high solar wind dynamic pressure, and high solar irradiance conditions, etc.). Present day extreme conditions may result in MF-MHD outputs that are similar to 2.5 GYA cases. The crustal field orientations are also considered in this study. By comparing estimates of past ion escape rates with the current ion loss rates to be returned by the MAVEN spacecraft (2013-2016), we can better constrain the total ion loss to space over Mars history, and thus enhance the science returned from the MAVEN mission.

Evaluation of solar Type II radio burst estimates of initial solar wind shock speed using a kinematic model of the solar wind on the April 2001 solar event swarm

NASA Astrophysics Data System (ADS)

Sun, W.; Dryer, M.; Fry, C. D.; Deehr, C. S.; Smith, Z.; Akasofu, S.-I.; Kartalev, M. D.; Grigorov, K. G.

2002-04-01

We compare simulation results of real time shock arrival time prediction with observations by the ACE satellite for a series of solar flares/coronal mass ejections which took place between 28 March and 18 April, 2001 on the basis of the Hakamada-Akasofu-Fry, version 2 (HAFv.2) model. It is found, via an ex post facto calculation, that the initial speed of shock waves as an input parameter of the modeling is crucial for the agreement between the observation and the simulation. The initial speed determined by metric Type II radio burst observations must be substantially reduced (30 percent in average) for most high-speed shock waves.

150 kW Class Solar Electric Propulsion Spacecraft Power Architecture Model

NASA Technical Reports Server (NTRS)

Csank, Jeffrey T.; Aulisio, Michael V.; Loop, Benjamin

2017-01-01

The National Aeronautics and Space Administration (NASA) Solar Electric Propulsion Technology Demonstration Mission (SEP TDM), in conjunction with PC Krause and Associates, has created a Simulink-based power architecture model for a 50 kilo-Watt (kW) solar electric propulsion system. NASA has extended this model to investigate 150 kW solar electric propulsion systems. Increasing the power capability to 150 kW is an intermediate step to the anticipated power requirements for Mars and other deep space applications. The high-power solar electric propulsion capability has been identified as a critical part of NASA’s future beyond-low-Earth-orbit for human-crewed exploration missions. This paper presents four versions of a 150 kW architecture, simulation results, and a discussion of their merits.

Fuzzy attitude control of solar sail via linear matrix inequalities

NASA Astrophysics Data System (ADS)

Baculi, Joshua; Ayoubi, Mohammad A.

2017-09-01

This study presents a fuzzy tracking controller based on the Takagi-Sugeno (T-S) fuzzy model of the solar sail. First, the T-S fuzzy model is constructed by linearizing the existing nonlinear equations of motion of the solar sail. Then, the T-S fuzzy model is used to derive the state feedback controller gains for the Twin Parallel Distributed Compensation (TPDC) technique. The TPDC tracks and stabilizes the attitude of the solar sail to any desired state in the presence of parameter uncertainties and external disturbances while satisfying actuator constraints. The performance of the TPDC is compared to a PID controller that is tuned using the Ziegler-Nichols method. Numerical simulation shows the TPDC outperforms the PID controller when stabilizing the solar sail to a desired state.

Our Sun V: A Bright Young Sun Consistent with Helioseismology and Warm Temperatures on Ancient Earth and Mars

NASA Technical Reports Server (NTRS)

Sackmann, I.-Juliana; Boothroyd, Arnold I.

2001-01-01

The relatively warm temperatures required on early Earth and Mars have been difficult to account for with warming from greenhouse gases. A slightly more massive young Sun would be brighter than predicted by the standard solar model, simultaneously resolving this problem for both Earth and Mars. We computed high-precision solar models with seven initial masses, from Mi = 1.01 to 1.07 solar mass - the latter being the maximum permitted if the early Earth is not to lose its water via a moist greenhouse effect. The relatively modest early mass loss that is required remains consistent with observational limits on mass loss from young stars and with estimates of the past solar wind obtained from lunar rocks. We considered three types of mass loss rates: (1) a reasonable choice of a simple exponential decline, (2) an extreme step-function case that gives the maximum effect consistent with observations, and (3) the radical case of a linear decline which is inconsistent with the solar wind mass loss estimates from lunar rocks. Our computations demonstrated that mass loss leaves a fingerprint oil the Sun's internal structure large enough to be detectable with helioseismic observations. All of our mass-losing solar models were consistent with the helioseismic observations; in fact, our preferred mass-losing cases were in marginally better agreement with the helioseismology than the standard solar model was, although this difference was smaller than the effects of other uncertainties in the input physics and in the solar composition. Mass loss has only a relatively minor effect on the predicted lithium depletion; the major portion of the solar lithium depletion must still be due to rotational mixing. Thus the modest mass loss cases considered here cannot be ruled out by observed lithium depletions. For the three mass loss types considered, the preferred initial masses were 1.07 solar mass for the exponential case and 1.04 solar mass for the step-function and linear cases; all of these provided high enough solar fluxes at Mars 3.8 Gyr ago to be consistent with the existence of liquid water. For a more massive early Sun, the planets would have had to be closer to the young Sun in order to end up in their present orbits; the orbital radii of the planets would vary inversely with the solar mass. Both of these effects contribute to the fact that the early solar flux at the planets would have been considerably higher than that of the standard solar model at that time. In fact, the 1.07 solar mass exponential case has a flux at birth 5% higher than the present solar flux, while the radical 1.04 solar mass linear case has a nearly constant flux over the first 3 Gyr only about 10% lower than at present. The early solar evolution would be in the opposite direction in the H-R diagram to that of the standard Sun.

Solar energetic particle transport in the heliosphere

NASA Astrophysics Data System (ADS)

Pei, Chunsheng

2007-08-01

The transport of solar energetic particles (SEPs) in the inner heliosphere is a very important issue which can affect our daily life. For example, large SEP events can lead to the failure of power grids, interrupt communications, and may participate in global climate change. The SEPS also can harm humans in space and destroy the instruments on board spacecraft. Studying the transport of SEPs also helps us understand remote regions of space which are not visible to us because there are not enough photons in those places. The interplanetary magnetic field is the medium in which solar energetic particles travel. The Parker Model of the solar wind and its successor, the Weber and Davis model, have been the dominant models of the solar wind and the interplanetary magnetic field since 1960s. In this thesis, I have reviewed these models and applied an important correction to the Weber and Davis model Various solar wind models and their limitations are presented. Different models can affect the calculation of magnetic field direction at 1 AU by as much as about 30%. Analysis of the onset of SEP events could be used to infer the release time of solar energetic particles and to differentiate between models of particle acceleration near the Sun. It is demonstrated that because of the nature of the stochastic heliospheric magnetic field, the path length measured along the line of force can be shorter than that of the nominal Parker spiral. These results help to explain recent observations. A two dimensional model and a fully three dimensional numerical model for the transport of SEPs has been developed based on Parker's transport equation for the first time. ''Reservoir'' phenomenon, which means the inner heliosphere works like a reservoir for SEPs during large SEP events, and multi-spacecraft observation of peak intensities are explained by this numerical model.

Evaluation of a Revised Interplanetary Shock Prediction Model: 1D CESE-HD-2 Solar-Wind Model

NASA Astrophysics Data System (ADS)

Zhang, Y.; Du, A. M.; Du, D.; Sun, W.

2014-08-01

We modified the one-dimensional conservation element and solution element (CESE) hydrodynamic (HD) model into a new version [ 1D CESE-HD-2], by considering the direction of the shock propagation. The real-time performance of the 1D CESE-HD-2 model during Solar Cycle 23 (February 1997 - December 2006) is investigated and compared with those of the Shock Time of Arrival Model ( STOA), the Interplanetary-Shock-Propagation Model ( ISPM), and the Hakamada-Akasofu-Fry version 2 ( HAFv.2). Of the total of 584 flare events, 173 occurred during the rising phase, 166 events during the maximum phase, and 245 events during the declining phase. The statistical results show that the success rates of the predictions by the 1D CESE-HD-2 model for the rising, maximum, declining, and composite periods are 64 %, 62 %, 57 %, and 61 %, respectively, with a hit window of ± 24 hours. The results demonstrate that the 1D CESE-HD-2 model shows the highest success rates when the background solar-wind speed is relatively fast. Thus, when the background solar-wind speed at the time of shock initiation is enhanced, the forecasts will provide potential values to the customers. A high value (27.08) of χ 2 and low p-value (< 0.0001) for the 1D CESE-HD-2 model give considerable confidence for real-time forecasts by using this new model. Furthermore, the effects of various shock characteristics (initial speed, shock duration, background solar wind, longitude, etc.) and background solar wind on the forecast are also investigated statistically.

A hybrid system for solar irradiance specification

NASA Astrophysics Data System (ADS)

Tobiska, W.; Bouwer, S.

2006-12-01

Space environment research and space weather operations require solar irradiances in a variety of time scales and spectral formats. We describe the development of solar irradiance characterization using four models and systems that are also used for space weather operations. The four models/systems include SOLAR2000 (S2K), SOLARFLARE (SFLR), APEX, and IDAR, which are used by Space Environment Technologies (SET) to provide solar irradiances from the soft X-rays through the visible spectrum. SFLR uses the GOES 0.1 0.8 nm X-rays in combination with a Mewe model subroutine to provide 0.1 30.0 nm irradiances at 0.1 nm spectral resolution, at 1 minute time resolution, and in a 6-hour XUV EUV spectral solar flare evolution forecast with a 7 minute latency and a 2 minute cadence. These irradiances have been calibrated with the SORCE XPS observations and we report on the inclusion of these irradiances into the S2K model. The APEX system is a real-time data retrieval system developed in conjunction with the University of Southern California Space Sciences Center (SSC) to provide SOHO SEM data processing and distribution. SSC provides the updated SEM data to the research community and SET provides the operational data to the space operations community. We describe how the SOHO SEM data, and especially the new S10.7 index, is being integrated directly into the S2K model for space weather operations. The IDAR system has been developed by SET to extract coronal hole boundaries, streamers, coronal loops, active regions, plage, network, and background (internetwork) features from solar images for comparison with solar magnetic features. S2K, SFLR, APEX, and IDAR outputs are integrated through the S2K solar irradiance platform that has become a hybrid system, i.e., a system that is able to produce irradiances using different processes, including empirical and physics-based models combined with real-time data integration.

Multi-Satellite Measurements and Model Predictions of Mesospheric and Upper Stratospheric Influences from the Very Large July 14-16, 2000, Solar Proton Event

NASA Technical Reports Server (NTRS)

Jackman, Charles H.; McPeters, Richard D.; Russell, James M.; Bevilacqua, Richard; Labow, Gordon J.; Fleming, Eric L.; Einaudi, Franco (Technical Monitor)

2000-01-01

A large solar flare with an associated coronal mass ejection occurred in mid-July and caused a very large solar proton event at the earth in the time period July 14-16, 2000. So far this is the largest solar storm of solar cycle 23. The solar proton fluxes were measured by instruments aboard the GOES-10 satellite and used in our proton energy deposition model to help quantify the energy input to the middle atmosphere during this large solar event. Using this computed energy deposition in the GSFC 2D atmospheric model resulted in a prediction of $>$ 20\\% increases in HO$-(x)$ (H, OH, HO$-(2)$) and $>$ 100\\% increases in NO$-(x)$ (N, NO, NO$-(2)$) constituents in the mesosphere and upper stratosphere at polar latitudes ($>$ 60 degrees geomagnetic). Both the HO$-(x)$ and NO$_fx)$ increases impacted ozone. Large atmospheric impacts have been measured with the NOAA 14 SBUV/2 instrument (0$_(3)$), the UARS HALOE instrument (NO, NO$-(2)$, 0$-(3)$), and the POAM III instrument (0$_{3}$, NO$-(2)$). Preliminary analysis indicates that measured (SBUV/2) and modelled 0$_{3}$ decreases from this solar event are generally in agreement in the Northern Hemisphere. Short-term ozone changes (during the event) indicate $\\sim$ 15% reduction at 2 hPa ($\\sim$ 45 km) up to $\\sim$ 40% reduction at 0.5 hPa ($\\sim$ 55 km). A longer-term ozone depletion of $\\sim$ 5% is indicated between 4 and 2 hPa ($\\sim$ 40-45 km). The middle atmospheric changes caused by this solar event were very large and occurred fairly quickly ($\\sim$ 1-2 days). Such a significant natural perturbation provides a good test of our understanding of the middle atmosphere. The measured and modelled impacts of this solar event will be compared and discussed in this paper.

Real-Time Photovoltaic and Solar Resource Testing | Photovoltaic Research |

Science.gov Websites

community toward developing comprehensive PV standards. Each year, NCPV researchers, along with solar performance Bill Marion: Solar radiation resource information, and PV module and system performance modeling NREL Real-Time Photovoltaic and Solar Resource Testing Real-Time Photovoltaic and Solar

Recent Successes of Wave/Turbulence Driven Models of Solar Wind Acceleration

NASA Astrophysics Data System (ADS)

Cranmer, S. R.; Hollweg, J. V.; Chandran, B. D.; van Ballegooijen, A. A.

2010-12-01

A key obstacle in the way of producing realistic simulations of the Sun-heliosphere system is the lack of a first-principles understanding of coronal heating. Also, it is still unknown whether the solar wind is "fed" through flux tubes that remain open (and are energized by footpoint-driven wavelike fluctuations) or if mass and energy are input intermittently from closed loops into the open-field regions. In this presentation, we discuss self-consistent models that assume the energy comes from solar Alfven waves that are partially reflected, and then dissipated, by magnetohydrodynamic turbulence. These models have been found to reproduce many of the observed features of the fast and slow solar wind without the need for artificial "coronal heating functions" used by earlier models. For example, the models predict a variation with wind speed in commonly measured ratios of charge states and elemental abundances that agrees with observed trends. This contradicts a commonly held assertion that these ratios can only be produced by the injection of plasma from closed-field regions on the Sun. This presentation also reviews two recent comparisons between the models and empirical measurements: (1) The models successfully predict the amplitude and radial dependence of Faraday rotation fluctuations (FRFs) measured by the Helios probes for heliocentric distances between 2 and 15 solar radii. The FRFs are a particularly sensitive test of turbulence models because they depend not only on the plasma density and Alfven wave amplitude in the corona, but also on the turbulent correlation length. (2) The models predict the correct sense and magnitude of changes seen in the polar high-speed solar wind by Ulysses from the previous solar minimum (1996-1997) to the more recent peculiar minimum (2008-2009). By changing only the magnetic field along the polar magnetic flux tube, consistent with solar and heliospheric observations at the two epochs, the model correctly predicts that the wind speed remains relatively unchanged, but the in-situ density and temperature decrease by approximately 20 percent and 10 percent, respectively.

Diagnostics of the solar corona from comparison between Faraday rotation measurements and magnetohydrodynamic simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le Chat, G.; Cohen, O.; Kasper, J. C.

Polarized natural radio sources passing behind the Sun experience Faraday rotation as a consequence of the electron density and magnetic field strength in coronal plasma. Since Faraday rotation is proportional to the product of the density and the component of the magnetic field along the line of sight of the observer, a model is required to interpret the observations and infer coronal structures. Faraday rotation observations have been compared with relatively ad hoc models of the corona. Here for the first time we compare these observations with magnetohydrodynamic (MHD) models of the solar corona driven by measurements of the photosphericmore » magnetic field. We use observations made with the NRAO Very Large Array of 34 polarized radio sources occulted by the solar corona between 5 and 14 solar radii. The measurements were made during 1997 May, and 2005 March and April. We compare the observed Faraday rotation values with values extracted from MHD steady-state simulations of the solar corona. We find that (1) using a synoptic map of the solar magnetic field just one Carrington rotation off produces poorer agreements, meaning that the outer corona changes in the course of one month, even in solar minimum; (2) global MHD models of the solar corona driven by photospheric magnetic field measurements are generally able to reproduce Faraday rotation observations; and (3) some sources show significant disagreement between the model and the observations, which appears to be a function of the proximity of the line of sight to the large-scale heliospheric current sheet.« less

RECONSTRUCTING THE SOLAR WIND FROM ITS EARLY HISTORY TO CURRENT EPOCH

DOE Office of Scientific and Technical Information (OSTI.GOV)

Airapetian, Vladimir S.; Usmanov, Arcadi V., E-mail: vladimir.airapetian@nasa.gov, E-mail: avusmanov@gmail.com

Stellar winds from active solar-type stars can play a crucial role in removal of stellar angular momentum and erosion of planetary atmospheres. However, major wind properties except for mass-loss rates cannot be directly derived from observations. We employed a three-dimensional magnetohydrodynamic Alfvén wave driven solar wind model, ALF3D, to reconstruct the solar wind parameters including the mass-loss rate, terminal velocity, and wind temperature at 0.7, 2, and 4.65 Gyr. Our model treats the wind thermal electrons, protons, and pickup protons as separate fluids and incorporates turbulence transport, eddy viscosity, turbulent resistivity, and turbulent heating to properly describe proton and electronmore » temperatures of the solar wind. To study the evolution of the solar wind, we specified three input model parameters, the plasma density, Alfvén wave amplitude, and the strength of the dipole magnetic field at the wind base for each of three solar wind evolution models that are consistent with observational constrains. Our model results show that the velocity of the paleo solar wind was twice as fast, ∼50 times denser and 2 times hotter at 1 AU in the Sun's early history at 0.7 Gyr. The theoretical calculations of mass-loss rate appear to be in agreement with the empirically derived values for stars of various ages. These results can provide realistic constraints for wind dynamic pressures on magnetospheres of (exo)planets around the young Sun and other active stars, which is crucial in realistic assessment of the Joule heating of their ionospheres and corresponding effects of atmospheric erosion.« less

Modeling study of the ionospheric responses to the quasi-biennial oscillations of the sun and stratosphere

NASA Astrophysics Data System (ADS)

Wang, Jack C.; Tsai-Lin, Rong; Chang, Loren C.; Wu, Qian; Lin, Charles C. H.; Yue, Jia

2018-06-01

The Quasi-biennial Oscillation (QBO) is a persistent oscillation in the zonal mean zonal winds of the low latitude middle atmosphere that is driven by breaking planetary and gravity waves with a period near two years. The atmospheric tides that dominate the dynamics of the mesosphere and lower thermosphere region (MLT, between heights of 70-120 km) are excited in the troposphere and stratosphere, and propagate through QBO-modulated zonal mean zonal wind fields. This allows the MLT tidal response to also be modulated by the QBO, with implications for ionospheric/thermospheric variability. Interannual oscillations in solar radiation can also directly drive the variations in the ionosphere with similar periodicities through the photoionization. Many studies have observed the connection between the solar activity and QBO signal in ionospheric features such as total electron content (TEC). In this research, we develop an empirical model to isolate stratospheric QBO-related tidal variability in the MLT diurnal and semidiurnal tides using values from assimilated TIMED satellite data. Migrating tidal fields corresponding to stratospheric QBO eastward and westward phases, as well as with the quasi-biennial variations in solar activity isolated by the Multi-dimensional Ensemble Empirical Mode Decomposition (MEEMD) analysis from Hilbert-Huang Transform (HHT), are then used to drive the NCAR Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIE-GCM). The numerical experiment results indicate that the ionospheric QBO is mainly driven by the solar quasi-biennial variations during the solar maximum, since the solar quasi-biennial variation amplitude is directly proportionate to the solar cycle. The ionospheric QBO in the model is sensitive to both the stratospheric QBO and solar quasi-biennial variations during the solar minimum, with solar effects still playing a stronger role.

The Solar Wind Source Cycle: Relationship to Dynamo Behavior

NASA Astrophysics Data System (ADS)

Luhmann, J. G.; Li, Y.; Lee, C. O.; Jian, L. K.; Petrie, G. J. D.; Arge, C. N.

2017-12-01

Solar cycle trends of interest include the evolving properties of the solar wind, the heliospheric medium through which the Sun's plasmas and fields interact with Earth and the planets -including the evolution of CME/ICMEs enroute. Solar wind sources include the coronal holes-the open field regions that constantly evolve with solar magnetic fields as the cycle progresses, and the streamers between them. The recent cycle has been notably important in demonstrating that not all solar cycles are alike when it comes to contributions from these sources, including in the case of ecliptic solar wind. In particular, it has modified our appreciation of the low latitude coronal hole and streamer sources because of their relative prevalence. One way to understand the basic relationship between these source differences and what is happening inside the Sun and on its surface is to use observation-based models like the PFSS model to evaluate the evolution of the coronal field geometry. Although the accuracy of these models is compromised around solar maximum by lack of global surface field information and the sometimes non-potential evolution of the field related to more frequent and widespread emergence of active regions, they still approximate the character of the coronal field state. We use these models to compare the inferred recent cycle coronal holes and streamer belt sources of solar wind with past cycle counterparts. The results illustrate how (still) hemispherically asymmetric weak polar fields maintain a complex mix of low-to-mid latitude solar wind sources throughout the latest cycle, with a related marked asymmetry in the hemispheric distribution of the ecliptic wind sources. This is likely to be repeated until the polar field strength significantly increases relative to the fields at low latitudes, and the latter symmetrize.

3D electron density distributions in the solar corona during solar minima: assessment for more realistic solar wind modeling

NASA Astrophysics Data System (ADS)

de Patoul, J.; Foullon, C.; Riley, P.

2015-12-01

Knowledge of the electron density distribution in the solar corona put constraints on the magnetic field configurations for coronal modeling, and on initial conditions for solar wind modeling. We work with polarized SOHO/LASCO-C2 images from the last two recent minima of solar activity (1996-1997 and 2008-2010), devoid of coronal mass ejections. We derive the 4D electron density distributions in the corona by applying a newly developed time-dependent tomographic reconstruction method. First we compare the density distributions obtained from tomography with magnetohydrodynamic (MHD) solutions. The tomography provides more accurate distributions of electron densities in the polar regions, and we find that the observed density varies with the solar cycle in both polar and equatorial regions. Second, we find that the highest-density structures do not always correspond to the predicted large-scale heliospheric current sheet or its helmet streamer but can follow the locations of pseudo-streamers. We conclude that tomography offers reliable density distribution in the corona, reproducing the slow time evolution of coronal structures, without prior knowledge of the coronal magnetic field over a full rotation. Finally, we suggest that the highest-density structures show a differential rotation well above the surface depending on how it is magnetically connected to the surface. Such valuable information on the rotation of large-scale structures could help to connect the sources of the solar wind to their in-situ counterparts in future missions such as Solar Orbiter and Solar Probe Plus. This research combined with the MHD coronal modeling efforts has the potential to increase the reliability for future space weather forecasting.

A predictive analytic model for the solar modulation of cosmic rays

DOE PAGES

Cholis, Ilias; Hooper, Dan; Linden, Tim

2016-02-23

An important factor limiting our ability to understand the production and propagation of cosmic rays pertains to the effects of heliospheric forces, commonly known as solar modulation. The solar wind is capable of generating time- and charge-dependent effects on the spectrum and intensity of low-energy (≲10 GeV) cosmic rays reaching Earth. Previous analytic treatments of solar modulation have utilized the force-field approximation, in which a simple potential is adopted whose amplitude is selected to best fit the cosmic-ray data taken over a given period of time. Making use of recently available cosmic-ray data from the Voyager 1 spacecraft, along withmore » measurements of the heliospheric magnetic field and solar wind, we construct a time-, charge- and rigidity-dependent model of solar modulation that can be directly compared to data from a variety of cosmic-ray experiments. Here, we provide a simple analytic formula that can be easily utilized in a variety of applications, allowing us to better predict the effects of solar modulation and reduce the number of free parameters involved in cosmic-ray propagation models.« less

Analysis and verification of a prediction model of solar energetic proton events

NASA Astrophysics Data System (ADS)

Wang, J.; Zhong, Q.

2017-12-01

The solar energetic particle event can cause severe radiation damages near Earth. The alerts and summary products of the solar energetic proton events were provided by the Space Environment Prediction Center (SEPC) according to the flux of the greater than 10 MeV protons taken by GOES satellite in geosynchronous orbit. The start of a solar energetic proton event is defined as the time when the flux of the greater than 10 MeV protons equals or exceeds 10 proton flux units (pfu). In this study, a model was developed to predict the solar energetic proton events, provide the warning for the solar energetic proton events at least minutes in advance, based on both the soft X-ray flux and integral proton flux taken by GOES. The quality of the forecast model was measured against verifications of accuracy, reliability, discrimination capability, and forecast skills. The peak flux and rise time of the solar energetic proton events in the six channels, >1MeV, >5 MeV, >10 MeV, >30 MeV, >50 MeV, >100 MeV, were also simulated and analyzed.

A Raster Based Approach To Solar Pressure Modeling

NASA Technical Reports Server (NTRS)

Wright, Theodore

2014-01-01

The impact of photons upon a spacecraft introduces small forces and moments. The magnitude and direction of the forces depend on the material properties of the spacecraft components being illuminated. Which components are being lit depends on the orientation of the craft with respect to the Sun as well as the gimbal angles for any significant moving external parts (solar arrays, typically). Some components may shield others from the Sun.To determine solar pressure in the presence overlapping components, a 3D model can be used to determine which components are illuminated. A view (image) of the model as seen from the Sun shows the only contributors to solar pressure. This image can be decomposed into pixels, each of which can be treated as a non-overlapping flat plate as far as solar pressure calculations are concerned. The sums of the pressures and moments on these plates approximate the solar pressure and moments on the entire vehicle.The image rasterization technique can also be used to compute other spacecraft attributes that are dependent on attitude and geometry, including solar array power generation capability and free molecular flow drag.

Investigation and Development of Data-Driven D-Region Model for HF Systems Impacts

NASA Technical Reports Server (NTRS)

Eccles, J. V.; Rice, D.; Sojka, J. J.; Hunsucker, R. D.

2002-01-01

Space Environment Corporation (SEC) and RP Consultants (RPC) are to develop and validate a weather-capable D region model for making High Frequency (HF) absorption predictions in support of the HF communications and radar communities. The weather-capable model will assimilate solar and earth space observations from NASA satellites. The model will account for solar-induced impacts on HF absorption, including X-rays, Solar Proton Events (SPE's), and auroral precipitation. The work plan includes: I . Optimize D-region model to quickly obtain ion and electron densities for proper HF absorption calculations. 2. Develop indices-driven modules for D-region ionization sources for low, mid, & high latitudes including X-rays, cosmic rays, auroral precipitation, & solar protons. (Note: solar spectrum & auroral modules already exist). 3. Setup low-cost monitors of existing HF beacons and add one single-frequency beacon. 4. Use PENEX HF-link database with HF monitor data to validate D-region/HF absorption model using climatological ionization drivers. 5. Develop algorithms to assimilate NASA satellite data of solar, interplanetary, and auroral observations into ionization source modules. 6. Use PENEX HF-link & HF-beacon data for skill score comparison of assimilation versus climatological D-region/HF absorption model. Only some satellites are available for the PENEX time period, thus, HF-beacon data is necessary. 7. Use HF beacon monitors to develop HF-link data assimilation algorithms for regional improvement to the D-region/HF absorption model.

PROM7: 1D modeler of solar filaments or prominences

NASA Astrophysics Data System (ADS)

Gouttebroze, P.

2018-05-01

PROM7 is an update of PROM4 (ascl:1306.004) and computes simple models of solar prominences and filaments using Partial Radiative Distribution (PRD). The models consist of plane-parallel slabs standing vertically above the solar surface. Each model is defined by 5 parameters: temperature, density, geometrical thickness, microturbulent velocity and height above the solar surface. It solves the equations of radiative transfer, statistical equilibrium, ionization and pressure equilibria, and computes electron and hydrogen level population and hydrogen line profiles. Moreover, the code treats calcium atom which is reduced to 3 ionization states (Ca I, Ca II, CA III). Ca II ion has 5 levels which are useful for computing 2 resonance lines (H and K) and infrared triplet (to 8500 A).

Perturbed-input-data ensemble modeling of magnetospheric dynamics

NASA Astrophysics Data System (ADS)

Morley, S.; Steinberg, J. T.; Haiducek, J. D.; Welling, D. T.; Hassan, E.; Weaver, B. P.

2017-12-01

Many models of Earth's magnetospheric dynamics - including global magnetohydrodynamic models, reduced complexity models of substorms and empirical models - are driven by solar wind parameters. To provide consistent coverage of the upstream solar wind these measurements are generally taken near the first Lagrangian point (L1) and algorithmically propagated to the nose of Earth's bow shock. However, the plasma and magnetic field measured near L1 is a point measurement of an inhomogeneous medium, so the individual measurement may not be sufficiently representative of the broader region near L1. The measured plasma may not actually interact with the Earth, and the solar wind structure may evolve between L1 and the bow shock. To quantify uncertainties in simulations, as well as to provide probabilistic forecasts, it is desirable to use perturbed input ensembles of magnetospheric and space weather forecasting models. By using concurrent measurements of the solar wind near L1 and near the Earth, we construct a statistical model of the distributions of solar wind parameters conditioned on their upstream value. So that we can draw random variates from our model we specify the conditional probability distributions using Kernel Density Estimation. We demonstrate the utility of this approach using ensemble runs of selected models that can be used for space weather prediction.

The Measurement of the Solar Spectral Irradiance Variability at 782 nm during the Solar Cycle 24 using the SES on-board PICARD

NASA Astrophysics Data System (ADS)

Meftah, Mustapha; Hauchecorne, Alain; Irbah, Abdanour; Bekki, Slimane

2016-04-01

A Sun Ecartometry Sensor (SES) was developed to provide the stringent pointing requirements of the PICARD satellite. The SES sensor produced an image of the Sun at 782+/-5 nm. From the SES data, we obtained a new time series of the solar spectral irradiance at 782nm from 2010 to 2014. SES observations provided a qualitatively consistent evolution of the solar spectral irradiance variability at 782 nm during the solar cycle 24. Comparisons will be made with Spectral And Total Irradiance REconstruction for the Satellite era (SATIRE-S) semi-empirical model and with the Spectral Irradiance Monitor instrument (SIM) on-board the Solar Radiation and Climate Experiment satellite (SORCE). These data will help to improve the representation of the solar forcing in the IPSL Global Circulation Model.

Data-driven agent-based modeling, with application to rooftop solar adoption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Haifeng; Vorobeychik, Yevgeniy; Letchford, Joshua

Agent-based modeling is commonly used for studying complex system properties emergent from interactions among many agents. We present a novel data-driven agent-based modeling framework applied to forecasting individual and aggregate residential rooftop solar adoption in San Diego county. Our first step is to learn a model of individual agent behavior from combined data of individual adoption characteristics and property assessment. We then construct an agent-based simulation with the learned model embedded in artificial agents, and proceed to validate it using a holdout sequence of collective adoption decisions. We demonstrate that the resulting agent-based model successfully forecasts solar adoption trends andmore » provides a meaningful quantification of uncertainty about its predictions. We utilize our model to optimize two classes of policies aimed at spurring solar adoption: one that subsidizes the cost of adoption, and another that gives away free systems to low-income house- holds. We find that the optimal policies derived for the latter class are significantly more efficacious, whereas the policies similar to the current California Solar Initiative incentive scheme appear to have a limited impact on overall adoption trends.« less

Adding a solar-radiance function to the Hošek-Wilkie skylight model.

PubMed

Hošek, Lukáš; Wilkie, Alexander

2013-01-01

One prerequisite for realistic renderings of outdoor scenes is the proper capturing of the sky's appearance. Currently, an explicit simulation of light scattering in the atmosphere isn't computationally feasible, and won't be in the foreseeable future. Captured luminance patterns have proven their usefulness in practice but can't meet all user needs. To fill this capability gap, computer graphics technology has employed analytical models of sky-dome luminance patterns for more than two decades. For technical reasons, such models deal with only the sky dome's appearance, though, and exclude the solar disc. The widely used model proposed by Arcot Preetham and colleagues employed a separately derived analytical formula for adding a solar emitter of suitable radiant intensity. Although this yields reasonable results, the formula is derived in a manner that doesn't exactly match the conditions in their sky-dome model. But the more sophisticated a skylight model is and the more subtly it can represent different conditions, the more the solar radiance should exactly match the skylight's conditions. Toward that end, researchers propose a solar-radiance function that exactly matches a recently published high-quality analytical skylight model.

Data-driven agent-based modeling, with application to rooftop solar adoption

DOE PAGES

Zhang, Haifeng; Vorobeychik, Yevgeniy; Letchford, Joshua; ...

2016-01-25

Agent-based modeling is commonly used for studying complex system properties emergent from interactions among many agents. We present a novel data-driven agent-based modeling framework applied to forecasting individual and aggregate residential rooftop solar adoption in San Diego county. Our first step is to learn a model of individual agent behavior from combined data of individual adoption characteristics and property assessment. We then construct an agent-based simulation with the learned model embedded in artificial agents, and proceed to validate it using a holdout sequence of collective adoption decisions. We demonstrate that the resulting agent-based model successfully forecasts solar adoption trends andmore » provides a meaningful quantification of uncertainty about its predictions. We utilize our model to optimize two classes of policies aimed at spurring solar adoption: one that subsidizes the cost of adoption, and another that gives away free systems to low-income house- holds. We find that the optimal policies derived for the latter class are significantly more efficacious, whereas the policies similar to the current California Solar Initiative incentive scheme appear to have a limited impact on overall adoption trends.« less

Predicting the Structure of the Solar Corona During the December 4, 2002 Total Solar Eclipse

NASA Technical Reports Server (NTRS)

Mikic, Zoran; Linker, Jon A.; Riley, Pete; Lionello, Roberto

2003-01-01

The solar magnetic field plays a key role in determining coronal. The principal input to MHD models is the observed solar magnetic field. 3D MHD models can be used to compare with eclipse and coronograph images, SOHO images (LOSCO, EIT), Ulysses and WIND spacecraft data, and interplanetary scintillation (IPS) measurements. MHD computations can tell us about the structure of the corona. Eclipses can help us to verify the accuracy of the models. 4 December, 2002 total eclipce: visible in the southern hemisphere (South Atlantic, southern Africa, Indian Ocean, and Australia). Total in center Angola is at 06:00 UT.

Modeling solar wind with boundary conditions from interplanetary scintillations

DOE PAGES

Manoharan, P.; Kim, T.; Pogorelov, N. V.; ...

2015-09-30

Interplanetary scintillations make it possible to create three-dimensional, time- dependent distributions of the solar wind velocity. Combined with the magnetic field observations in the solar photosphere, they help perform solar wind simulations in a genuinely time-dependent way. Interplanetary scintillation measurements from the Ooty Radio Astronomical Observatory in India provide directions to multiple stars and may assure better resolution of transient processes in the solar wind. In this paper, we present velocity distributions derived from Ooty observations and compare them with those obtained with the Wang-Sheeley-Arge (WSA) model. We also present our simulations of the solar wind flow from 0.1 AUmore » to 1 AU with the boundary conditions based on both Ooty and WSA data.« less

A lightweight solar array study

NASA Technical Reports Server (NTRS)

Josephs, R. H.

1977-01-01

A sample module was assembled to model a portion of a flexible extendable solar array, a type that promises to become the next generation of solar array design. The resulting study of this module is intended to provide technical support to the array designer for lightweight component selection, specifications, and tests. Selected from available lightweight components were 127-micron-thick wrap-around contacted solar cells, 34- micron-thick sputtered glass covers, and as a substrate a 13-micron-thick polyimide film clad with a copper printed circuit. Each component displayed weaknesses. The thin solar cells had excessive breakage losses. Sputtered glass cover adhesion was poor, and the covered cell was weaker than the cell uncovered. Thermal stresses caused some cell delamination from the model solar array substrate.

Modelling Magnetodisc Response to Solar Wind Events

NASA Astrophysics Data System (ADS)

Achilleos, N.; Guio, P.; Arridge, C. S.

2017-09-01

The Sun's influence is felt by planets in the solar system in many different ways. In this work, we use theoretical models of the magnetic fields of the Gas Giants (Jupiter and Saturn) to predict how they would change in response to compressions and expansions in the flow of charged particles ('solar wind') which continually emanates from the Sun. This in an example of 'Space Weather' - the interaction between the solar wind and magnetized planets, such as Jupiter, Saturn and even the Earth.

3DCORE: Forward modeling of solar storm magnetic flux ropes for space weather prediction

NASA Astrophysics Data System (ADS)

Möstl, C.; Amerstorfer, T.; Palmerio, E.; Isavnin, A.; Farrugia, C. J.; Lowder, C.; Winslow, R. M.; Donnerer, J. M.; Kilpua, E. K. J.; Boakes, P. D.

2018-05-01

3DCORE forward models solar storm magnetic flux ropes called 3-Dimensional Coronal Rope Ejection (3DCORE). The code is able to produce synthetic in situ observations of the magnetic cores of solar coronal mass ejections sweeping over planets and spacecraft. Near Earth, these data are taken currently by the Wind, ACE and DSCOVR spacecraft. Other suitable spacecraft making these kind of observations carrying magnetometers in the solar wind were MESSENGER, Venus Express, MAVEN, and even Helios.

Numerical modeling of the thin shallow solar dynamo

NASA Astrophysics Data System (ADS)

O'Bryan, J. B.; Jarboe, T. R.

2017-10-01

Nonlinear, numerical computation with the NIMROD code is used to explore and validate the thin shallow solar dynamo model [T.R. Jarboe et al. 2017], which explains the observed global temporal evolution (e.g. magnetic field reversal) and local surface structures (e.g. sunspots) of the sun. The key feature of this model is the presence and magnetic self-organization of global magnetic structures (GMS) lying just below the surface of the sun, which resemble 1D radial Taylor states of size comparable to the supergranule convection cells. First, we seek to validate the thin shallow solar dynamo model by reproducing the 11 year timescale for reversal of the solar magnetic field. Then, we seek to model formation of GMS from convection zone turbulence. Our computations simulate a slab covering a radial depth 3Mm and include differential rotation and gravity. Density, temperature, and resistivity profiles are taken from the Christensen-Dalsgaard model.

Two solar proton fluence models based on ground level enhancement observations

NASA Astrophysics Data System (ADS)

Raukunen, Osku; Vainio, Rami; Tylka, Allan J.; Dietrich, William F.; Jiggens, Piers; Heynderickx, Daniel; Dierckxsens, Mark; Crosby, Norma; Ganse, Urs; Siipola, Robert

2018-01-01

Solar energetic particles (SEPs) constitute an important component of the radiation environment in interplanetary space. Accurate modeling of SEP events is crucial for the mitigation of radiation hazards in spacecraft design. In this study we present two new statistical models of high energy solar proton fluences based on ground level enhancement (GLE) observations during solar cycles 19-24. As the basis of our modeling, we utilize a four parameter double power law function (known as the Band function) fits to integral GLE fluence spectra in rigidity. In the first model, the integral and differential fluences for protons with energies between 10 MeV and 1 GeV are calculated using the fits, and the distributions of the fluences at certain energies are modeled with an exponentially cut-off power law function. In the second model, we use a more advanced methodology: by investigating the distributions and relationships of the spectral fit parameters we find that they can be modeled as two independent and two dependent variables. Therefore, instead of modeling the fluences separately at different energies, we can model the shape of the fluence spectrum. We present examples of modeling results and show that the two methodologies agree well except for a short mission duration (1 year) at low confidence level. We also show that there is a reasonable agreement between our models and three well-known solar proton models (JPL, ESP and SEPEM), despite the differences in both the modeling methodologies and the data used to construct the models.

Computing diffuse fraction of global horizontal solar radiation: A model comparison.

PubMed

Dervishi, Sokol; Mahdavi, Ardeshir

2012-06-01

For simulation-based prediction of buildings' energy use or expected gains from building-integrated solar energy systems, information on both direct and diffuse component of solar radiation is necessary. Available measured data are, however, typically restricted to global horizontal irradiance. There have been thus many efforts in the past to develop algorithms for the derivation of the diffuse fraction of solar irradiance. In this context, the present paper compares eight models for estimating diffuse fraction of irradiance based on a database of measured irradiance from Vienna, Austria. These models generally involve mathematical formulations with multiple coefficients whose values are typically valid for a specific location. Subsequent to a first comparison of these eight models, three better performing models were selected for a more detailed analysis. Thereby, the coefficients of the models were modified to account for Vienna data. The results suggest that some models can provide relatively reliable estimations of the diffuse fractions of the global irradiance. The calibration procedure could only slightly improve the models' performance.

A review of the solar array manufacturing industry costing standards

NASA Technical Reports Server (NTRS)

1977-01-01

The solar array manufacturing industry costing standards model is designed to compare the cost of producing solar arrays using alternative manufacturing processes. Constructive criticism of the methodology used is intended to enhance its implementation as a practical design tool. Three main elements of the procedure include workbook format and presentation, theoretical model validity and standard financial parameters.

Application of a global solar wind/planetary obstacle interaction computational model: Earth, Venus, Mars, Jupiter and Saturn studies

NASA Technical Reports Server (NTRS)

Stahara, S. S.

1984-01-01

The investigations undertaken in this report relate to studies of various solar wind interaction phenomena with Venus, Earth, Mars, Jupiter and Saturn. A computational model is developed for the determination of the detailed plasma and magnetic field properties associated with various planetary obstacles throughout the solar system.

The development of an advanced generic solar dynamic heat receiver thermal model

NASA Technical Reports Server (NTRS)

Wu, Y. C.; Roschke, E. J.; Kohout, L.

1988-01-01

An advanced generic solar dynamic heat receiver thermal model under development which can analyze both orbital transient and orbital average conditions is discussed. This model can be used to study advanced receiver concepts, evaluate receiver concepts under development, analyze receiver thermal characteristics under various operational conditions, and evaluate solar dynamic system thermal performances in various orbit conditions. The model and the basic considerations that led to its creation are described, and results based on a set of baseline orbit, configuration, and operational conditions are presented to demonstrate the working of the receiver model.

An All Sky Instantaneous Shortwave Solar Radiation Model for Mountainous Terrain

NASA Astrophysics Data System (ADS)

Zhang, S.; Li, X.; She, J.

2017-12-01

In mountainous terrain, solar radiation shows high heterogeneity in space and time because of strong terrain shading effects and significant variability of cloud cover. While existing GIS-based solar radiation models simulate terrain shading effects with relatively high accuracy and models based on satellite datasets consider fine scale cloud attenuation processes, none of these models have considered the geometrical relationships between sun, cloud, and terrain, which are important over mountainous terrain. In this research we propose sky cloud maps to represent cloud distribution in a hemispherical sky using MODIS cloud products. By overlaying skyshed (visible area in the hemispherical sky derived from DEM), sky map, and sky cloud maps, we are able to consider both terrain shading effects and anisotropic cloud attenuation in modeling instantaneous direct and diffuse solar radiation in mountainous terrain. The model is evaluated with field observations from three automatic weather stations in the Tizinafu watershed in the Kunlun Mountains of northwestern China. Overall, under all sky conditions, the model overestimates instantaneous global solar radiation with a mean absolute relative difference (MARD) of 22%. The model is also evaluated under clear sky (clearness index of more than 0.75) and partly cloudy sky (clearness index between 0.35 and 0.75) conditions with MARDs of 5.98% and 23.65% respectively. The MARD for very cloudy sky (clearness index less than 0.35) is relatively high. But these days occur less than 1% of the time. The model is sensitive to DEM data error, algorithms used in delineating skyshed, and errors in MODIS atmosphere and cloud products. Our model provides a novel approach for solar radiation modeling in mountainous areas.

Evolution of Multiscale Multifractal Turbulence in the Heliosphere

NASA Astrophysics Data System (ADS)

Macek, W. M.; Wawrzaszek, A.

2009-04-01

The aim of this study is to examine the question of scaling properties of intermittent turbulence in the space environment. We analyze time series of velocities of the slow and fast speed streams of the solar wind measured in situ by Helios 2, Advanced Composition Explorer and Voyager 2 spacecraft in the inner and outer heliosphere during solar minimum and maximum at various distances from the Sun. To quantify asymmetric scaling of solar wind turbulence, we consider a generalized two-scale weighted Cantor set with two different scales describing nonuniform distribution of the kinetic energy flux between cascading eddies of various sizes. We investigate the resulting spectrum of generalized dimensions and the corresponding multifractal singularity spectrum depending on one probability measure parameter and two rescaling parameters, demonstrating that the multifractal scaling is often rather asymmetric. In particular, we show that the degree of multifractality for the solar wind during solar minimum is greater for fast streams velocity fluctuations than that for the slow streams; the fast wind during solar minimum may exhibit strong asymmetric scaling. Moreover, we observe the evolution of multifractal scaling of the solar wind in the outer heliosphere. It is worth noting that for the model with two different scaling parameters a much better agreement with the solar wind data is obtained, especially for the negative index of the generalized dimensions. Therefore we argue that there is a need to use a two-scale cascade model. Hence we propose this new more general model as a useful tool for analysis of intermittent turbulence in various environments. References [1] W. M. Macek and A. Szczepaniak, Generalized two-scale weighted Cantor set model for solar wind turbulence, Geophys. Res. Lett., 35, L02108, doi:10.1029/2007GL032263 (2008). [2] A. Szczepaniak and W. M. Macek, Asymmetric multifractal model for solar wind intermittent turbulence, Nonlin. Processes Geophys., 15, 615-620 (2008), http://www.nonlin-processes-geophys.net/15/615/2008/. [3] W. M. Macek and A. Wawrzaszek, Evolution of asymmetric multifractal scaling of solar wind turbulence in the outer heliosphere, J. Geophys. Res., A013795, doi:10.1029/2008JA013795, in press.

An Experimentalist's Overview of Solar Neutrinos

NASA Astrophysics Data System (ADS)

Oser, Scott M.

2012-02-01

Four decades of solar neutrino research have demonstrated that solar models do a remarkable job of predicting the neutrino fluxes from the Sun, to the extent that solar neutrinos can now serve as a calibrated neutrino source for experiments to understand neutrino oscillations and mixing. In this review article I will highlight the most significant experimental results, with emphasis on the latest model-independent measurements from the Sudbury Neutrino Observatory. The solar neutrino fluxes are seen to be generally well-determined experimentally, with no indications of time variability, while future experiments will elucidate the lower energy part of the neutrino spectrum, especially pep and CNO neutrinos.

Thermally Driven One-Fluid Electron-Proton Solar Wind: Eight-Moment Approximation

NASA Astrophysics Data System (ADS)

Olsen, Espen Lyngdal; Leer, Egil

1996-05-01

In an effort to improve the "classical" solar wind model, we study an eight-moment approximation hydrodynamic solar wind model, in which the full conservation equation for the heat conductive flux is solved together with the conservation equations for mass, momentum, and energy. We consider two different cases: In one model the energy flux needed to drive the solar wind is supplied as heat flux from a hot coronal base, where both the density and temperature are specified. In the other model, the corona is heated. In that model, the coronal base density and temperature are also specified, but the temperature increases outward from the coronal base due to a specified energy flux that is dissipated in the corona. The eight-moment approximation solutions are compared with the results from a "classical" solar wind model in which the collision-dominated gas expression for the heat conductive flux is used. It is shown that the "classical" expression for the heat conductive flux is generally not valid in the solar wind. In collisionless regions of the flow, the eight-moment approximation gives a larger thermalization of the heat conductive flux than the models using the collision-dominated gas approximation for the heat flux, but the heat flux is still larger than the "saturation heat flux." This leads to a breakdown of the electron distribution function, which turns negative in the collisionless region of the flow. By increasing the interaction between the electrons, the heat flux is reduced, and a reasonable shape is obtained on the distribution function. By solving the full set of equations consistent with the eight-moment distribution function for the electrons, we are thus able to draw inferences about the validity of the eight-moment description of the solar wind as well as the validity of the very commonly used collision-dominated gas approximation for the heat conductive flux in the solar wind.

Solar Effects on Global Climate Due to Cosmic Rays and Solar Energetic Particles

NASA Technical Reports Server (NTRS)

Turco, R. P.; Raeder, J.; DAuria, R.

2005-01-01

Although the work reported here does not directly connect solar variability with global climate change, this research establishes a plausible quantitative causative link between observed solar activity and apparently correlated variations in terrestrial climate parameters. Specifically, we have demonstrated that ion-mediated nucleation of atmospheric particles is a likely, and likely widespread, phenomenon that relates solar variability to changes in the microphysical properties of clouds. To investigate this relationship, we have constructed and applied a new model describing the formation and evolution of ionic clusters under a range of atmospheric conditions throughout the lower atmosphere. The activation of large ionic clusters into cloud nuclei is predicted to be favorable in the upper troposphere and mesosphere, and possibly in the lower stratosphere. The model developed under this grant needs to be extended to include additional cluster families, and should be incorporated into microphysical models to further test the cause-and-effect linkages that may ultimately explain key aspects of the connections between solar variability and climate.

Modeling integrated photovoltaic–electrochemical devices using steady-state equivalent circuits

PubMed Central

Winkler, Mark T.; Cox, Casandra R.; Nocera, Daniel G.; Buonassisi, Tonio

2013-01-01

We describe a framework for efficiently coupling the power output of a series-connected string of single-band-gap solar cells to an electrochemical process that produces storable fuels. We identify the fundamental efficiency limitations that arise from using solar cells with a single band gap, an arrangement that describes the use of currently economic solar cell technologies such as Si or CdTe. Steady-state equivalent circuit analysis permits modeling of practical systems. For the water-splitting reaction, modeling defines parameters that enable a solar-to-fuels efficiency exceeding 18% using laboratory GaAs cells and 16% using all earth-abundant components, including commercial Si solar cells and Co- or Ni-based oxygen evolving catalysts. Circuit analysis also provides a predictive tool: given the performance of the separate photovoltaic and electrochemical systems, the behavior of the coupled photovoltaic–electrochemical system can be anticipated. This predictive utility is demonstrated in the case of water oxidation at the surface of a Si solar cell, using a Co–borate catalyst.

Solar plus: Optimization of distributed solar PV through battery storage and dispatchable load in residential buildings

DOE Office of Scientific and Technical Information (OSTI.GOV)

O'Shaughnessy, Eric; Cutler, Dylan; Ardani, Kristen

As utility electricity rates evolve, pairing solar photovoltaic (PV) systems with battery storage has potential to ensure the value proposition of residential solar by mitigating economic uncertainty. In addition to batteries, load control technologies can reshape customer load profiles to optimize PV system use. The combination of PV, energy storage, and load control provides an integrated approach to PV deployment, which we call 'solar plus'. The U.S. National Renewable Energy Laboratory's Renewable Energy Optimization (REopt) model is utilized to evaluate cost-optimal technology selection, sizing, and dispatch in residential buildings under a variety of rate structures and locations. The REopt modelmore » is extended to include a controllable or 'smart' domestic hot water heater model and smart air conditioner model. We find that the solar plus approach improves end user economics across a variety of rate structures - especially those that are challenging for PV - including lower grid export rates, non-coincident time-of-use structures, and demand charges.« less

Solar plus: Optimization of distributed solar PV through battery storage and dispatchable load in residential buildings

DOE PAGES

O'Shaughnessy, Eric; Cutler, Dylan; Ardani, Kristen; ...

2018-01-11

As utility electricity rates evolve, pairing solar photovoltaic (PV) systems with battery storage has potential to ensure the value proposition of residential solar by mitigating economic uncertainty. In addition to batteries, load control technologies can reshape customer load profiles to optimize PV system use. The combination of PV, energy storage, and load control provides an integrated approach to PV deployment, which we call 'solar plus'. The U.S. National Renewable Energy Laboratory's Renewable Energy Optimization (REopt) model is utilized to evaluate cost-optimal technology selection, sizing, and dispatch in residential buildings under a variety of rate structures and locations. The REopt modelmore » is extended to include a controllable or 'smart' domestic hot water heater model and smart air conditioner model. We find that the solar plus approach improves end user economics across a variety of rate structures - especially those that are challenging for PV - including lower grid export rates, non-coincident time-of-use structures, and demand charges.« less

Estimation of daily flow rate of photovoltaic water pumping systems using solar radiation data

NASA Astrophysics Data System (ADS)

Benghanem, M.; Daffallah, K. O.; Almohammedi, A.

2018-03-01

This paper presents a simple model which allows us to contribute in the studies of photovoltaic (PV) water pumping systems sizing. The nonlinear relation between water flow rate and solar power has been obtained experimentally in a first step and then used for performance prediction. The model proposed enables us to simulate the water flow rate using solar radiation data for different heads (50 m, 60 m, 70 m and 80 m) and for 8S × 3P PV array configuration. The experimental data are obtained with our pumping test facility located at Madinah site (Saudi Arabia). The performances are calculated using the measured solar radiation data of different locations in Saudi Arabia. Knowing the solar radiation data, we have estimated with a good precision the water flow rate Q in five locations (Al-Jouf, Solar Village, AL-Ahsa, Madinah and Gizan) in Saudi Arabia. The flow rate Q increases with the increase of pump power for different heads following the nonlinear model proposed.

A Summary Description of a Computer Program Concept for the Design and Simulation of Solar Pond Electric Power Generation Systems

NASA Technical Reports Server (NTRS)

1984-01-01

A solar pond electric power generation subsystem, an electric power transformer and switch yard, a large solar pond, a water treatment plant, and numerous storage and evaporation ponds. Because a solar pond stores thermal energy over a long period of time, plant operation at any point in time is dependent upon past operation and future perceived generation plans. This time or past history factor introduces a new dimension in the design process. The design optimization of a plant must go beyond examination of operational state points and consider the seasonal variations in solar, solar pond energy storage, and desired plant annual duty-cycle profile. Models or design tools will be required to optimize a plant design. These models should be developed in order to include a proper but not excessive level of detail. The model should be targeted to a specific objective and not conceived as a do everything analysis tool, i.e., system design and not gradient-zone stability.

NESSY: NLTE spectral synthesis code for solar and stellar atmospheres

NASA Astrophysics Data System (ADS)

Tagirov, R. V.; Shapiro, A. I.; Schmutz, W.

2017-07-01

Context. Physics-based models of solar and stellar magnetically-driven variability are based on the calculation of synthetic spectra for various surface magnetic features as well as quiet regions, which are a function of their position on the solar or stellar disc. Such calculations are performed with radiative transfer codes tailored for modeling broad spectral intervals. Aims: We aim to present the NLTE Spectral SYnthesis code (NESSY), which can be used for modeling of the entire (UV-visible-IR and radio) spectra of solar and stellar magnetic features and quiet regions. Methods: NESSY is a further development of the COde for Solar Irradiance (COSI), in which we have implemented an accelerated Λ-iteration (ALI) scheme for co-moving frame (CMF) line radiation transfer based on a new estimate of the local approximate Λ-operator. Results: We show that the new version of the code performs substantially faster than the previous one and yields a reliable calculation of the entire solar spectrum. This calculation is in a good agreement with the available observations.

E-beam deposited Ag-nanoparticles plasmonic organic solar cell and its absorption enhancement analysis using FDTD-based cylindrical nano-particle optical model.

PubMed

Kim, Richard S; Zhu, Jinfeng; Park, Jeung Hun; Li, Lu; Yu, Zhibin; Shen, Huajun; Xue, Mei; Wang, Kang L; Park, Gyechoon; Anderson, Timothy J; Pei, Qibing

2012-06-04

We report the plasmon-assisted photocurrent enhancement in Ag-nanoparticles (Ag-NPs) embedded PEDOT:PSS/P3HT:PCBM organic solar cells, and systematically investigate the causes of the improved optical absorption based on a cylindrical Ag-NPs optical model which is simulated with a 3-Dimensional finite difference time domain (FDTD) method. The proposed cylindrical Ag-NPs optical model is able to explain the optical absorption enhancement by the localized surface plasmon resonance (LSPR) modes, and to provide a further understanding of Ag-NPs shape parameters which play an important role to determine the broadband absorption phenomena in plasmonic organic solar cells. A significant increase in the power conversion efficiency (PCE) of the plasmonic solar cell was experimentally observed and compared with that of the solar cells without Ag-NPs. Finally, our conclusion was made after briefly discussing the electrical effects of the fabricated plasmonic organic solar cells.

Numerical Study of Solar Storms from the Sun to Earth

NASA Astrophysics Data System (ADS)

Feng, Xueshang; Jiang, Chaowei; Zhou, Yufen

2017-04-01

As solar storms are sweeping the Earth, adverse changes occur in geospace environment. How human can mitigate and avoid destructive damages caused by solar storms becomes an important frontier issue that we must face in the high-tech times. It is of both scientific significance to understand the dynamic process during solar storm's propagation in interplanetary space and realistic value to conduct physics-based numerical researches on the three-dimensional process of solar storms in interplanetary space with the aid of powerful computing capacity to predict the arrival times, intensities, and probable geoeffectiveness of solar storms at the Earth. So far, numerical studies based on magnetohydrodynamics (MHD) have gone through the transition from the initial qualitative principle researches to systematic quantitative studies on concrete events and numerical predictions. Numerical modeling community has a common goal to develop an end-to-end physics-based modeling system for forecasting the Sun-Earth relationship. It is hoped that the transition of these models to operational use depends on the availability of computational resources at reasonable cost and that the models' prediction capabilities may be improved by incorporating the observational findings and constraints into physics-based models, combining the observations, empirical models and MHD simulations in organic ways. In this talk, we briefly focus on our recent progress in using solar observations to produce realistic magnetic configurations of CMEs as they leave the Sun, and coupling data-driven simulations of CMEs to heliospheric simulations that then propagate the CME configuration to 1AU, and outlook the important numerical issues and their possible solutions in numerical space weather modeling from the Sun to Earth for future research.

Data-driven Model of the ICME Propagation through the Solar Corona and Inner Heliosphere

NASA Astrophysics Data System (ADS)

Yalim, M. S.; Pogorelov, N.; Singh, T.; Liu, Y.

2017-12-01

The solar wind (SW) emerging from the Sun is the main driving mechanism of solar events which may lead to geomagnetic storms that are the primary causes of space weather disturbances that affect the magnetic environment of Earth and may have hazardous effects on the space-borne and ground-based technological systems as well as human health. Therefore, accurate modeling of the SW is very important to understand the underlying mechanisms of such storms.Getting ready for the Parker Solar Probe mission, we have developed a data-driven magnetohydrodynamic (MHD) model of the global solar corona which utilizes characteristic boundary conditions implemented within the Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS) - a collection of problem oriented routines incorporated into the Chombo adaptive mesh refinement framework developed at Lawrence Berkeley National Laboratory. Our global solar corona model can be driven by both synoptic and synchronic vector magnetogram data obtained by the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) and the horizontal velocity data on the photosphere obtained by applying the Differential Affine Velocity Estimatorfor Vector Magnetograms (DAVE4VM) method on the HMI-observed vector magnetic fields.Our CME generation model is based on Gibson-Low-type flux ropes the parameters of which are determined from analysis of observational data from STEREO/SECCHI, SDO/AIA and SOHO/LASCO, and by applying the Graduate Cylindrical Shell model for the flux rope reconstruction.In this study, we will present the results of three-dimensional global simulations of ICME propagation through our characteristically-consistent MHD model of the background SW from the Sun to Earth driven by HMI-observed vector magnetic fields and validate our results using multiple spacecraft data at 1 AU.

A Solar-Pumped Fluorescence Model for Line-By-Line Emission Intensities in the B-X, A-X, and X-X Band Systems of 12C14N

NASA Technical Reports Server (NTRS)

Paganini, L.; Mumma, M. J.

2016-01-01

We present a new quantitative model for detailed solar-pumped fluorescent emission of the main isotopologue of CN. The derived fluorescence efficiencies permit estimation and interpretation of ro-vibrational infrared line intensities of CN in exospheres exposed to solar (or stellar) radiation. Our g-factors are applicable to astronomical observations of CN extending from infrared to optical wavelengths, and we compare them with previous calculations in the literature. The new model enables extraction of rotational temperature, column abundance, and production rate from astronomical observations of CN in the inner coma of comets. Our model accounts for excitation and de-excitation of rotational levels in the ground vibrational state by collisions, solar excitation to the A(sup 2)Pi(sub I) and B(sup 2)Sum(sup +) electronically excited states followed by cascade to ro-vibrational levels of X(sup 2)Sum(sup +), and direct solar infrared pumping of ro-vibrational levels in the X(sup 2)Sum(sup +) state. The model uses advanced solar spectra acquired at high spectral resolution at the relevant infrared and optical wavelengths and considers the heliocentric radial velocity of the comet (the Swings effect) when assessing the exciting solar flux for a given transition. We present model predictions for the variation of fluorescence rates with rotational temperature and heliocentric radial velocity. Furthermore, we test our fluorescence model by comparing predicted and measured line-by-line intensities for X(sup 2)Sum(sup +) (1-0) in comet C/2014 Q2 (Lovejoy), thereby identifying multiple emission lines observed at IR wavelengths.

New solar irradiances for use in space research

NASA Astrophysics Data System (ADS)

Tobiska, W.; Bouwer, D.; Jones, A.

Space environment research applications require solar irradiances in a variety of time scales and spectral formats We describe the development of research grade modeled solar irradiances using four models and systems that are also used for space weather operations The four models systems include SOLAR2000 S2K SOLARFLARE SFLR APEX and IDAR which are used by Space Environment Technologies SET to provide solar irradiances from the soft X-rays through the visible spectrum SFLR uses the GOES 0 1--0 8 nm X-rays in combination with a Mewe model subroutine to provide 0 1--30 0 nm irradiances at 0 1 nm spectral resolution at 1 minute time resolution and in a 6-hour XUV--EUV spectral solar flare evolution forecast with a 7 minute latency and a 2 minute cadence These irradiances have been calibrated with the SORCE XPS observations and we report on the inclusion of these irradiances in the S2K model There are additional developments with S2K that we discuss particularly the method by which S2K is emerging as a hybrid model empirical plus physics-based and real-time data integration platform Numerous new solar indices have been recently developed for the operations community and we describe their inclusion in S2K The APEX system is a real-time data retrieval system developed under contract to the University of Southern California Space Sciences Center SSC to provide SOHO SEM data processing and distribution SSC provides the updated SEM data to the research community and SET provides the operational data to the space operations community We

A Babcock-Leighton solar dynamo model with multi-cellular meridional circulation in advection- and diffusion-dominated regimes

NASA Astrophysics Data System (ADS)

Belucz, B.; Dikpati, M.; Forgacs-Dajka, E.

2014-12-01

Babcock-Leighton type solar dynamo models with single cell meridional circulation are successful in reproducing many solarcycle features, and recently such a model was applied for solarcycle 24 amplitude prediction. It seems that cycle 24 amplitudeforecast may not be validated. One of the reasons is the assumption of a single cell meridional circulation. Recent observations andtheoretical models of meridional circulation do not indicate a single-celledflow pattern. So it is nessecary to examine the role of complexmulti-cellular circulation patterns in a Babcock-Leighton solar dynamo model in the advection and diffusion dominated regimes.By simulating a Babcock-Leighton solar dynamo model with multi-cellularflow, we show that the presence of a weak, second, high-latitudereverse cell speeds up the cycle and slighty enhances the poleward branch in the butterfly diagram, whereas the presence of a second cellin depth reverses the tilt of the butterfly wing and leads to ananti-solar type feature. If, instead, the butterfly diagram isconstructed from the middle of the convection zone in that case, a solar-like pattern can be retrieved. All the above cases behavequalitatively similar in advection and diffusion-dominated regimes.However, our dynamo with a meridional circulation containing fourcells in latitude behaves distinctly different in the two regimes, producing a solar-like butterfly diagram with fast cycles indiffusion-dominated regime, and a complex branches in the butterflydiagram in the advection-dominated regime. Another interestingfinding from our studies is that a four-celled flow pattern containing two in radius and two in latitude always producesquadrupolar parity as the relaxed solution.

A Shifting Shield Provides Protection Against Cosmic Rays

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-12-01

The Sun plays an important role in protecting us from cosmic rays, energetic particles that pelt us from outside our solar system. But can we predict when and how it will provide the most protection, and use this to minimize the damage to both pilotedand roboticspace missions?The Challenge of Cosmic RaysSpacecraft outside of Earths atmosphere and magnetic field are at risk of damage from cosmic rays. [ESA]Galactic cosmic rays are high-energy, charged particles that originate from astrophysical processes like supernovae or even distant active galactic nuclei outside of our solar system.One reason to care about the cosmic rays arriving near Earth is because these particles can provide a significant challenge for space missions traveling above Earths protective atmosphere and magnetic field. Since impacts from cosmic rays can damage human DNA, this risk poses a major barrier to plans for interplanetary travel by crewed spacecraft. And roboticmissions arent safe either: cosmic rays can flip bits, wreaking havoc on spacecraft electronics as well.The magnetic field carried by the solar wind provides a protective shield, deflecting galactic cosmic rays from our solar system. [Walt Feimer/NASA GSFCs Conceptual Image Lab]Shielded by the SunConveniently, we do have some broader protection against galactic cosmic rays: a built-in shield provided by the Sun. The interplanetary magnetic field, which is embedded in the solar wind, deflects low-energy cosmic rays from us at the outer reaches of our solar system, decreasing the flux of these cosmic rays that reach us at Earth.This shield, however, isnt stationary; instead, it moves and changes as the strength and direction of the solar wind moves and changes. This results in a much lower cosmic-ray flux at Earth when solar activity is high i.e., at the peak of the 11-year solar cycle than when solar activity is low. This visible change in local cosmic-ray flux with solar activity is known as solar modulation of the cosmic ray flux at Earth.In a new study, a team of scientists led by Nicola Tomassetti (University of Perugia, Italy) has modeled this solar modulation to better understand the process by which the Suns changing activity influences the cosmic ray flux that reaches us at Earth.Modeling a LagTomassetti and collaborators model uses two solar-activity observables as inputs: the number of sunspots and the tilt angle of the heliospheric current sheet. By modeling basic transport processes in the heliosphere, the authors then track the impact that the changing solar properties have on incoming galactic cosmic rays. In particular, the team explores the time lag between when solar activity changes and when we see the responding change in the cosmic-ray flux.Cosmic-ray flux observations are best fit by the authors model when an 8-month lag is included (red bold line). A comparison model with no lag (black dashed line) is included. [Tomassetti et al. 2017]By comparing their model outputs to the large collection of time-dependent observations of cosmic-ray fluxes, Tomassetti and collaborators show that the best fit to data occurs with an 8-month lag between changing solar activity and local cosmic-ray flux modulation.This is an important outcome for studying the processes that affect the cosmic-ray flux that reaches Earth. But theres an additional intriguing consequence of this result: knowledge of the current solar activity could allow us to predict the modulation that will occur for cosmic rays near Earth an entire 8 months from now! If this model is correct, it brings us one step closer to being able to plan safer space missions for the future.CitationNicola Tomassetti et al 2017 ApJL 849 L32. doi:10.3847/2041-8213/aa9373

FUPSOL: Modelling the Future and Past Solar Influence on Earth Climate

NASA Astrophysics Data System (ADS)

Anet, J. G.; Rozanov, E.; Peter, T.

2012-04-01

Global warming is becoming one of the main threats to mankind. There is growing evidence that anthropogenic greenhouse gases have become the dominant factor since about 1970. At the same time natural factors of climate change such as solar and volcanic forcings cannot be neglected on longer time scales. Despite growing scientific efforts over the last decades in both, observations and simulations, the uncertainty of the solar contribution to the past climate change remained unacceptably high (IPCC, 2007), the reasons being on one hand missing observations of solar irradiance prior to the satellite era, and on the other hand a majority of models so far not including all processes relevant for solar-climate interactions. This project aims at elucidating the processes governing the effects of solar activity variations on Earth's climate. We use the state-of-the-art coupled atmosphere-ocean-chemistry-climate model (AOCCM) SOCOL (Schraner et al, 2008) developed in Switzerland by coupling the community Earth System Model (ESM) COSMOS distributed by MPI for Meteorology (Hamburg, Germany) with a comprehensive atmospheric chemistry module. The model solves an extensive set of equations describing the dynamics of the atmosphere and ocean, radiative transfer, transport of species, their chemical transformations, cloud formation and the hydrological cycle. The intention is to show how past solar variations affected climate and how the decrease in solar forcing expected for the next decades will affect climate on global and regional scales. We will simulate the global climate system behavior during Dalton minimum (1790 and 1830) and first half of 21st century with a series of multiyear ensemble experiments and perform these experiments using all known anthropogenic and natural climate forcing taken in different combinations to understand the effects of solar irradiance in different spectral regions and particle precipitation variability. Further on, we will quantify the solar influence on global climate in the future by evaluating the simulations and using information from past analogs such as the Dalton minimum. In the end, the project aims at reducing the uncertainty of the solar contribution to past and future climate change, which so far remained high despite many years of analyses of observational records and theoretical investigations with climate models of different complexity.

The Effect of Solar Forcing on the Greenland Ice Sheet during the Holocene - A Model Study

NASA Astrophysics Data System (ADS)

Bügelmayer, Marianne; Roche, Didier; Renssen, Hans

2014-05-01

Abrupt climate changes did not only happen during glacials but also during interglacials such as the Holocene. Marine sediments provide evidence for the periodic occurrence of centennial-scale events with enhanced iceberg discharge during the past 11.000 years (Bond et al., 2001). These events were chronologically linked to reduced solar activity as reconstructed using cosmogenic isotopes (Bond et al., 2001), indicating that even an external forcing that is considered to be small, has a potential impact on climate due to several feedback mechanisms (Renssen et al., 2006). The interactions between climate and solar irradiance have been investigated using numerical models (e.g. Haigh, 1996; Renssen et al, 2006), but so far without dynamically computing the Greenland ice sheet and iceberg calving. Thus, the impact of solar variations on iceberg discharge and the underlying mechanisms have not been analysed so far. To analyse the effect of variations in solar activity on the Greenland ice sheet (GIS) and the iceberg calving, as well as possible feedback mechanisms that enhance the impact of the total solar irradiance, we use the earth system model of intermediate complexity (iLOVECLIM, Roche et al., 2013), coupled to the ice sheet/ice shelf model GRISLI (Ritz et al., 2001) and to a dynamic-thermodynamic iceberg module (Jongma et al., 2009, Bügelmayer et al., 2014) to perform transient experiments of the last 6000 years. The experiments are conducted applying reconstructed atmospheric greenhouse gas concentrations, volcanic aerosol loads, orbital parameters and variations in the total solar irradiance. We present the response of the coupled model to different solar irradiance scenarios to evaluate modeled GIS sensitivity to relatively modest variations in radiative forcing. Moreover, we investigate the dependence of the model results on the chosen model sensitivity. References: Bond, G., Kromer, B., Beer, J., Muscheler, R., Evans, M. N., Showers, W., … Bonani, G. (2001): Persistent solar influence on North Atlantic climate during the Holocene. Science (New York, N.Y.), 294(5549), 2130-6. doi:10.1126/science.1065680 Bügelmayer, M., Roche, D.M., Renssen, H. (2014): How do icebergs affect the Greenland ice sheet under pre-industrial conditions? - A model study with a fully coupled ice sheet-climate model. The Cryosphere Discussions 8, 187-228. Haigh, J. D. (1996): The Impact of Solar Variability on Climate. Science, 272, 981-984. Jongma, J.I., Driesschaert, E., Fichefet, T., Goosse, H., Renssen, H., (2009): The effect of dynamic-thermodynamic icebergs on the Southern Ocean climate in a three-dimensional model. Ocean Modelling 26, 104-113. Renssen, H., Goosse, H., Muscheler, R., & Branch, R. (2006): Coupled climate model simulation of Holocene cooling events: oceanic feedback amplifies solar forcing. Climate of the Past, 2, 79-90. Ritz, C., Rommelaere, V. and Dumas, C.(2001): Modeling the evolution of Antarctic ice sheet over the last 420,000 years: Implications for altitude changes in the Vostok region, Journal of Geophysical Research, 106, 31943-31964, doi:10.1029/2001JD900232. Roche, D.M., Dumas, C., Bügelmayer, M., Charbit, S., Ritz, C. (2013): Adding a dynamical cryosphere into iLOVECLIM (version 1.0) - Part 1: Coupling with the GRISLI ice-sheet model, Geoscientific Model Development Discussion, 6, 5215-5249.

Low-cost silicon solar array project environmental hail model for assessing risk to solar collectors

NASA Technical Reports Server (NTRS)

Gonzalez, C.

1977-01-01

The probability of solar arrays being struck by hailstones of various sizes as a function of geographic location and service life was assessed. The study complements parallel studies of solar array sensitivity to hail damage, the final objective being an estimate of the most cost effective level for solar array hail protection.

NREL: Renewable Resource Data Center - Solar Resource Information

Science.gov Websites

Solar Resource Information The Renewable Resource Data Center (RReDC) offers a collection of data and tools to assist with solar resource research. Learn more about RReDC's solar resource: Data Models siting. In addition, RReDC offers a solar resource glossary, unit conversion information, and an

Mapping magnetic field lines between the Sun and Earth

NASA Astrophysics Data System (ADS)

Li, B.; Cairns, Iver H.; Gosling, J. T.; Steward, G.; Francis, M.; Neudegg, D.; Schulte in den Bäumen, H.; Player, P. R.; Milne, A. R.

2016-02-01

Magnetic field topologies between the Sun and Earth are important for the connectivity to Earth of solar suprathermal particles, e.g., solar energetic particles and beam electrons in type III solar radio bursts. An approach is developed for mapping large-scale magnetic field lines near the solar equatorial plane, using near-Earth observations and a solar wind model with nonzero azimuthal magnetic field at the source surface. Unlike Parker's spiral model, which restricts the in-ecliptic angle ΦB in the Geocentric Solar Ecliptic coordinates to (90°-180°, 270°-360°) and so is unable to predict field configurations for the other ΦB values frequently observed in the solar wind, our approach can account for all the observed ΦB values. A set of predicted maps shows that near both minimal and maximal solar activity the field lines are typically open and that loops with both ends either connected to or disconnected from the Sun are relatively rare. The open field lines, nonetheless, often do not closely follow the Parker spiral, being less or more tightly wound, or strongly azimuthally or radially oriented, or inverted. The time-varying classes, e.g., bidirectional electrons, of suprathermal electron pitch angle distributions (PADs) at 1 AU are predicted from the mapped field line configurations and compared with Wind observations for two solar rotations, one each near solar minimum and solar maximum. PAD predictions by our approach agree quantitatively (≈90%) with the PAD observations and outperform (by ≈20%) PAD predictions using Parker's model.

Solar cycle variations in mesospheric carbon monoxide

NASA Astrophysics Data System (ADS)

Lee, Jae N.; Wu, Dong L.; Ruzmaikin, Alexander; Fontenla, Juan

2018-05-01

As an extension of Lee et al. (2013), solar cycle variation of carbon monoxide (CO) is analyzed with MLS observation, which covers more than thirteen years (2004-2017) including maximum of solar cycle 24. Being produced primarily by the carbon dioxide (CO2) photolysis in the lower thermosphere, the variations of the mesospheric CO concentration are largely driven by the solar cycle modulated ultraviolet (UV) variation. This solar signal extends down to the lower altitudes by the dynamical descent in the winter polar vortex, showing a time lag that is consistent with the average descent velocity. To characterize a global distribution of the solar impact, MLS CO is correlated with the SORCE measured total solar irradiance (TSI) and UV. As high as 0.8 in most of the polar mesosphere, the linear correlation coefficients between CO and UV/TSI are more robust than those found in the previous work. The photochemical contribution explains most (68%) of the total variance of CO while the dynamical contribution accounts for 21% of the total variance at upper mesosphere. The photochemistry driven CO anomaly signal is extended in the tropics by vertical mixing. The solar cycle signal in CO is further examined with the Whole Atmosphere Community Climate Model (WACCM) 3.5 simulation by implementing two different modeled Spectral Solar Irradiances (SSIs): SRPM 2012 and NRLSSI. The model simulations underestimate the mean CO amount and solar cycle variations of CO, by a factor of 3, compared to those obtained from MLS observation. Different inputs of the solar spectrum have small impacts on CO variation.

Theoretical analysis of improved efficiency of silicon-wafer solar cells with textured nanotriangular grating structure

NASA Astrophysics Data System (ADS)

Zhang, Yaoju; Zheng, Jun; Zhao, Xuesong; Ruan, Xiukai; Cui, Guihua; Zhu, Haiyong; Dai, Yuxing

2018-03-01

A practical model of crystalline silicon-wafer solar cells is proposed in order to enhance the light absorption and improve the conversion efficiency of silicon solar cells. In the model, the front surface of the silicon photovoltaic film is designed to be a textured-triangular-grating (TTG) structure, and the ITO contact film and the antireflection coating (ARC) of glass are coated on the TTG surface of silicon solar cells. The optical absorption spectrum of solar cells are simulated by applying the finite difference time domain method. Electrical parameters of the solar cells are calculated using two models with and without carrier loss. The effect of structure parameters on the performance of the TTG cell is discussed in detail. It is found that the thickness (tg) of the ARC, period (p) of grating, and base angle (θ) of triangle have a crucial influence on the conversion efficiency. The optimal structure of the TTG cell is designed. The TTG solar cell can produce higher efficiency in a wide range of solar incident angle and the average efficiency of the optimal TTG cell over 7:30-16:30 time of day is 8% higher than that of the optimal plane solar cell. In addition, the study shows that the bulk recombination of carriers has an influence on the conversion efficiency of the cell, the conversion efficiency of the actual solar cell with carrier recombination is reduced by 20.0% of the ideal cell without carrier recombination.

The 1973 solar occultation of the Crab Nebula pulsar

NASA Technical Reports Server (NTRS)

Weisberg, J. M.

1975-01-01

The mean electron density of the solar corona was determined by measuring the dispersion of radiofrequency pulses from pulsar NP 0532 during the June 1973 solar occultation. Trends continued which were noticed in 1971 as solar activity declined. Model fitting results suggest that the corona continued to become even more concentrated toward the equator in 1973 than in 1971. The number density of electrons in most regions decreased. The best model of the distribution of corona electrons is suggested to be one with zero density at the poles. K-corona isophotes and contours of equal path-integrated density are presented for several models. Electron density versus date and position in the corona are tabulated. It is seen that there is no simple relationship between the onset of major solar activity and density or scattering enhancements.

Reliability models applicable to space telescope solar array assembly system

NASA Technical Reports Server (NTRS)

Patil, S. A.

1986-01-01

A complex system may consist of a number of subsystems with several components in series, parallel, or combination of both series and parallel. In order to predict how well the system will perform, it is necessary to know the reliabilities of the subsystems and the reliability of the whole system. The objective of the present study is to develop mathematical models of the reliability which are applicable to complex systems. The models are determined by assuming k failures out of n components in a subsystem. By taking k = 1 and k = n, these models reduce to parallel and series models; hence, the models can be specialized to parallel, series combination systems. The models are developed by assuming the failure rates of the components as functions of time and as such, can be applied to processes with or without aging effects. The reliability models are further specialized to Space Telescope Solar Arrray (STSA) System. The STSA consists of 20 identical solar panel assemblies (SPA's). The reliabilities of the SPA's are determined by the reliabilities of solar cell strings, interconnects, and diodes. The estimates of the reliability of the system for one to five years are calculated by using the reliability estimates of solar cells and interconnects given n ESA documents. Aging effects in relation to breaks in interconnects are discussed.

Statistical validation of a solar wind propagation model from 1 to 10 AU

NASA Astrophysics Data System (ADS)

Zieger, Bertalan; Hansen, Kenneth C.

2008-08-01

A one-dimensional (1-D) numerical magnetohydrodynamic (MHD) code is applied to propagate the solar wind from 1 AU through 10 AU, i.e., beyond the heliocentric distance of Saturn's orbit, in a non-rotating frame of reference. The time-varying boundary conditions at 1 AU are obtained from hourly solar wind data observed near the Earth. Although similar MHD simulations have been carried out and used by several authors, very little work has been done to validate the statistical accuracy of such solar wind predictions. In this paper, we present an extensive analysis of the prediction efficiency, using 12 selected years of solar wind data from the major heliospheric missions Pioneer, Voyager, and Ulysses. We map the numerical solution to each spacecraft in space and time, and validate the simulation, comparing the propagated solar wind parameters with in-situ observations. We do not restrict our statistical analysis to the times of spacecraft alignment, as most of the earlier case studies do. Our superposed epoch analysis suggests that the prediction efficiency is significantly higher during periods with high recurrence index of solar wind speed, typically in the late declining phase of the solar cycle. Among the solar wind variables, the solar wind speed can be predicted to the highest accuracy, with a linear correlation of 0.75 on average close to the time of opposition. We estimate the accuracy of shock arrival times to be as high as 10-15 hours within ±75 d from apparent opposition during years with high recurrence index. During solar activity maximum, there is a clear bias for the model to predicted shocks arriving later than observed in the data, suggesting that during these periods, there is an additional acceleration mechanism in the solar wind that is not included in the model.

The Large-scale Coronal Structure of the 2017 August 21 Great American Eclipse: An Assessment of Solar Surface Flux Transport Model Enabled Predictions and Observations

NASA Astrophysics Data System (ADS)

Nandy, Dibyendu; Bhowmik, Prantika; Yeates, Anthony R.; Panda, Suman; Tarafder, Rajashik; Dash, Soumyaranjan

2018-01-01

On 2017 August 21, a total solar eclipse swept across the contiguous United States, providing excellent opportunities for diagnostics of the Sun’s corona. The Sun’s coronal structure is notoriously difficult to observe except during solar eclipses; thus, theoretical models must be relied upon for inferring the underlying magnetic structure of the Sun’s outer atmosphere. These models are necessary for understanding the role of magnetic fields in the heating of the corona to a million degrees and the generation of severe space weather. Here we present a methodology for predicting the structure of the coronal field based on model forward runs of a solar surface flux transport model, whose predicted surface field is utilized to extrapolate future coronal magnetic field structures. This prescription was applied to the 2017 August 21 solar eclipse. A post-eclipse analysis shows good agreement between model simulated and observed coronal structures and their locations on the limb. We demonstrate that slow changes in the Sun’s surface magnetic field distribution driven by long-term flux emergence and its evolution governs large-scale coronal structures with a (plausibly cycle-phase dependent) dynamical memory timescale on the order of a few solar rotations, opening up the possibility for large-scale, global corona predictions at least a month in advance.

DATA ASSIMILATION APPROACH FOR FORECAST OF SOLAR ACTIVITY CYCLES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kitiashvili, Irina N., E-mail: irina.n.kitiashvili@nasa.gov

Numerous attempts to predict future solar cycles are mostly based on empirical relations derived from observations of previous cycles, and they yield a wide range of predicted strengths and durations of the cycles. Results obtained with current dynamo models also deviate strongly from each other, thus raising questions about criteria to quantify the reliability of such predictions. The primary difficulties in modeling future solar activity are shortcomings of both the dynamo models and observations that do not allow us to determine the current and past states of the global solar magnetic structure and its dynamics. Data assimilation is a relativelymore » new approach to develop physics-based predictions and estimate their uncertainties in situations where the physical properties of a system are not well-known. This paper presents an application of the ensemble Kalman filter method for modeling and prediction of solar cycles through use of a low-order nonlinear dynamo model that includes the essential physics and can describe general properties of the sunspot cycles. Despite the simplicity of this model, the data assimilation approach provides reasonable estimates for the strengths of future solar cycles. In particular, the prediction of Cycle 24 calculated and published in 2008 is so far holding up quite well. In this paper, I will present my first attempt to predict Cycle 25 using the data assimilation approach, and discuss the uncertainties of that prediction.« less

A three-dimensional model of solar radiation transfer in a non-uniform plant canopy

NASA Astrophysics Data System (ADS)

Levashova, N. T.; Mukhartova, Yu V.

2018-01-01

A three-dimensional (3D) model of solar radiation transfer in a non-uniform plant canopy was developed. It is based on radiative transfer equations and a so-called turbid medium assumption. The model takes into account the multiple scattering contributions of plant elements in radiation fluxes. These enable more accurate descriptions of plant canopy reflectance and transmission in different spectral bands. The model was applied to assess the effects of plant canopy heterogeneity on solar radiation transmission and to quantify the difference in a radiation transfer between photosynthetically active radiation PAR (=0.39-0.72 μm) and near infrared solar radiation NIR (Δλ = 0.72-3.00 μm). Comparisons of the radiative transfer fluxes simulated by the 3D model within a plant canopy consisted of sparsely planted fruit trees (plant area index, PAI - 0.96 m2 m-2) with radiation fluxes simulated by a one-dimensional (1D) approach, assumed horizontal homogeneity of plant and leaf area distributions, showed that, for sunny weather conditions with a high solar elevation angle, an application of a simplified 1D approach can result in an underestimation of transmitted solar radiation by about 22% for PAR, and by about 26% for NIR.

Effect of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal solar cells

NASA Astrophysics Data System (ADS)

Sahin, Mehmet

2018-05-01

In this study, the effects of the shell material and confinement type on the conversion efficiency of core/shell quantum dot nanocrystal (QDNC) solar cells have been investigated in detail. For this purpose, the conventional, i.e. original, detailed balance model, developed by Shockley and Queisser to calculate an upper limit for the conversion efficiency of silicon p–n junction solar cells, is modified in a simple and effective way to calculate the conversion efficiency of core/shell QDNC solar cells. Since the existing model relies on the gap energy () of the solar cell, it does not make an estimation about the effect of QDNC materials on the efficiency of the solar cells, and gives the same efficiency values for several QDNC solar cells with the same . The proposed modification, however, estimates a conversion efficiency in relation to the material properties and also the confinement type of the QDNCs. The results of the modified model show that, in contrast to the original one, the conversion efficiencies of different QDNC solar cells, even if they have the same , become different depending upon the confinement type and shell material of the core/shell QDNCs, and this is crucial in the design and fabrication of the new generation solar cells to predict the confinement type and also appropriate QDNC materials for better efficiency.

The response of middle atmospheric ozone to solar UV irradiance variations with a period of 27 days

NASA Technical Reports Server (NTRS)

Chen, LI; Brasseur, Guy; London, Julius

1994-01-01

A one-dimensional photochemical-dynamical-radiative time-dependent model was used to study the response of middle atmospheric temperature and ozone to solar UV irradiance variations with the period of 27 days. The model solar UV O(x), HO(x), NO(x), and CIO(x)families and modeled solar UV variations. The amplitude of the primary temperature response to the solar UV variation is plus 0.4 K at 85-90 km with a phase lag of about 6 days. A secondary maximum response of plus 0.3 K at 45-50 km appears with a phase lag of 1 day. There is a maximum positive ozone response to the 27-day solar UV oscillation of 2.5 percent at 80-90 km with a phase lag of about 10 days after the solar irradiance maximum. At 70 km the ozone response is about 1.2 percent and is out of phase with the solar variation. In the upper stratosphere (40-50 km) the relative ozone variation is small, about 0.2 percent to 0.3 percent, and there is a negative phase of about 4 days between the ozone and solar oscillations. These oscillations are in phase in the middle stratosphere (35-40 km) where there is again a maximum relative response of about 0.6 percent. The reasons for these ozone amplitude and phase variations are discussed.

A theoretical model of the variation of the meridional circulation with the solar cycle

NASA Astrophysics Data System (ADS)

Hazra, Gopal; Choudhuri, Arnab Rai

2017-12-01

Observations of the meridional circulation of the Sun, which plays a key role in the operation of the solar dynamo, indicate that its speed varies with the solar cycle, becoming faster during the solar minima and slower during the solar maxima. To explain this variation of the meridional circulation with the solar cycle, we construct a theoretical model by coupling the equation of the meridional circulation (the ϕ component of the vorticity equation within the solar convection zone) with the equations of the flux transport dynamo model. We consider the back reaction due to the Lorentz force of the dynamo-generated magnetic fields and study the perturbations produced in the meridional circulation due to it. This enables us to model the variations of the meridional circulation without developing a full theory of the meridional circulation itself. We obtain results which reproduce the observational data of solar cycle variations of the meridional circulation reasonably well. We get the best results on assuming the turbulent viscosity acting on the velocity field to be comparable to the magnetic diffusivity (i.e. on assuming the magnetic Prandtl number to be close to unity). We have to assume an appropriate bottom boundary condition to ensure that the Lorentz force cannot drive a flow in the subadiabatic layers below the bottom of the tachocline. Our results are sensitive to this bottom boundary condition. We also suggest a hypothesis on how the observed inward flow towards the active regions may be produced.

Inclusion of Solar Elevation Angle in Land Surface Albedo Parameterization Over Bare Soil Surface.

PubMed

Zheng, Zhiyuan; Wei, Zhigang; Wen, Zhiping; Dong, Wenjie; Li, Zhenchao; Wen, Xiaohang; Zhu, Xian; Ji, Dong; Chen, Chen; Yan, Dongdong

2017-12-01

Land surface albedo is a significant parameter for maintaining a balance in surface energy. It is also an important parameter of bare soil surface albedo for developing land surface process models that accurately reflect diurnal variation characteristics and the mechanism behind the solar spectral radiation albedo on bare soil surfaces and for understanding the relationships between climate factors and spectral radiation albedo. Using a data set of field observations, we conducted experiments to analyze the variation characteristics of land surface solar spectral radiation and the corresponding albedo over a typical Gobi bare soil underlying surface and to investigate the relationships between the land surface solar spectral radiation albedo, solar elevation angle, and soil moisture. Based on both solar elevation angle and soil moisture measurements simultaneously, we propose a new two-factor parameterization scheme for spectral radiation albedo over bare soil underlying surfaces. The results of numerical simulation experiments show that the new parameterization scheme can more accurately depict the diurnal variation characteristics of bare soil surface albedo than the previous schemes. Solar elevation angle is one of the most important factors for parameterizing bare soil surface albedo and must be considered in the parameterization scheme, especially in arid and semiarid areas with low soil moisture content. This study reveals the characteristics and mechanism of the diurnal variation of bare soil surface solar spectral radiation albedo and is helpful in developing land surface process models, weather models, and climate models.

Hindcast and forecast of grand solar minina and maxima using a three-frequency dynamo model based on Jupiter-Saturn tidal frequencies modulating the 11-year sunspot cycle

NASA Astrophysics Data System (ADS)

Scafetta, Nicola

2016-04-01

The Schwabe frequency band of the Zurich sunspot record since 1749 is found to be made of three major cycles with periods of about 9.98, 10.9 and 11.86 years. The two side frequencies appear to be closely related to the spring tidal period of Jupiter and Saturn (range between 9.5 and 10.5 years, and median 9.93 years) and to the tidal sidereal period of Jupiter (about 11.86 years). The central cycle can be associated to a quasi-11-year sunspot solar dynamo cycle that appears to be approximately synchronized to the average of the two planetary frequencies. A simplified harmonic constituent model based on the above two planetary tidal frequencies and on the exact dates of Jupiter and Saturn planetary tidal phases, plus a theoretically deduced 10.87-year central cycle reveals complex quasi-periodic interference/beat patterns. The major beat periods occur at about 115, 61 and 130 years, plus a quasi-millennial large beat cycle around 983 years. These frequencies and other oscillations appear once the model is non-linearly processed. We show that equivalent synchronized cycles are found in cosmogenic records used to reconstruct solar activity and in proxy climate records throughout the Holocene (last 12,000 years) up to now. The quasi-secular beat oscillations hindcast reasonably well the known prolonged periods of low solar activity during the last millennium such as the Oort, Wolf, Sporer, Maunder and Dalton minima, as well as the 17 115-year long oscillations found in a detailed temperature reconstruction of the Northern Hemisphere covering the last 2000 years. The millennial cycle hindcasts equivalent solar and climate cycles for 12,000 years. Finally, the harmonic model herein proposed reconstructs the prolonged solar minima that occurred during 1900- 1920 and 1960-1980 and the secular solar maxima around 1870-1890, 1940-1950 and 1995-2005 and a secular upward trending during the 20th century: this modulated trending agrees well with some solar proxy model, with the ACRIM TSI satellite composite and with the global surface temperature modulation since 1850. The model forecasts a new prolonged solar minimum during 2020-2045, which would be produced mostly by the minima of both the 61 and 115-year reconstructed cycles. Finally, the model predicts that during low solar activity periods, the solar cycle length tends to be longer, as some researchers have claimed. These results clearly indicate that both solar and climate oscillations are linked to planetary motion and, furthermore, their timing can be reasonably hindcast and forecast for decades, centuries and millennia. Scafetta, N.: Multi-scale harmonic model for solar and climate cyclical variation throughout the Holocene based on Jupiter-Saturn tidal frequencies plus the 11-year solar dynamo cycle. J. Atmos. Sol.- Terr. Phys. 80, 296-311 (2012). Scafetta, N.: Does the Sun work as a nuclear fusion amplifier of planetary tidal forcing? A proposal for a physical mechanism based on the mass-luminosity relation. J. Atmos. Sol.-Terr. Phys. 81-82, 27-40 (2012). Scafetta, N.: Discussion on the spectral coherence between planetary, solar and climate oscillations: a reply to some critiques. Astrophys. Space Sci. 354, 275-299 (2014).

Forecast and Specification of Radiation Belt Electrons Based on Solar Wind Measurements

NASA Astrophysics Data System (ADS)

Li, X.; Barker, A.; Burin Des Roziers, E.

2003-12-01

Relativistic electrons in the Earth's magnetosphere are of considerable practical importance because of their effect on spacecraft and because of their radiation hazard to astronauts who perform extravehicular activity. The good correlation between solar wind velocity and MeV electron fluxes at geosynchronous orbit has long been established. We have developed a radial diffusion model, using solar wind parameters as the only input, to reproduce the variation of the MeV electrons at geosynchronous orbit. Based on this model, we have constructed a real-time model that forecasts one to two days in advance the daily averaged >2 MeV electron flux at geosynchronous orbit using real-time solar wind data from ACE. The forecasts from this model are available on the web in real time. A natural extension of our current model is to create a system for making quantitative forecasts and specifications of radiation belt electrons at different radial distances and different local times based on the solar wind conditions. The successes and obstacles associated with this extension will be discussed in this presentation.

Nonlinear data assimilation: towards a prediction of the solar cycle

NASA Astrophysics Data System (ADS)

Svedin, Andreas

The solar cycle is the cyclic variation of solar activity, with a span of 9-14 years. The prediction of the solar cycle is an important and unsolved problem with implications for communications, aviation and other aspects of our high-tech society. Our interest is model-based prediction, and we present a self-consistent procedure for parameter estimation and model state estimation, even when only one of several model variables can be observed. Data assimilation is the art of comparing, combining and transferring observed data into a mathematical model or computer simulation. We use the 3DVAR methodology, based on the notion of least squares, to present an implementation of a traditional data assimilation. Using the Shadowing Filter — a recently developed method for nonlinear data assimilation — we outline a path towards model based prediction of the solar cycle. To achieve this end we solve a number of methodological challenges related to unobserved variables. We also provide a new framework for interpretation that can guide future predictions of the Sun and other astrophysical objects.

Improvements in Modeling Thruster Plume Erosion Damage to Spacecraft Surfaces

NASA Technical Reports Server (NTRS)

Soares, Carlos; Olsen, Randy; Steagall, Courtney; Huang, Alvin; Mikatarian, Ron; Myers, Brandon; Koontz, Steven; Worthy, Erica

2015-01-01

Spacecraft bipropellant thrusters impact spacecraft surfaces with high speed droplets of unburned and partially burned propellant. These impacts can produce erosion damage to optically sensitive hardware and systems (e.g., windows, camera lenses, solar cells and protective coatings). On the International Space Station (ISS), operational constraints are levied on the position and orientation of the solar arrays to mitigate erosion effects during thruster operations. In 2007, the ISS Program requested evaluation of erosion constraint relief to alleviate operational impacts due to an impaired Solar Alpha Rotary Joint (SARJ). Boeing Space Environments initiated an activity to identify and remove sources of conservatism in the plume induced erosion model to support an expanded range of acceptable solar array positions ? The original plume erosion model over-predicted plume erosion and was adjusted to better correlate with flight experiment results. This paper discusses findings from flight experiments and the methodology employed in modifying the original plume erosion model for better correlation of predictions with flight experiment data. The updated model has been successful employed in reducing conservatism and allowing for enhanced flexibility in ISS solar array operations.

Photocatalytic mineralization of commercial herbicides in a pilot-scale solar CPC reactor: photoreactor modeling and reaction kinetics constants independent of radiation field.

PubMed

Colina-Márquez, Jose; Machuca-Martínez, Fiderman; Li Puma, Gianluca

2009-12-01

The six-flux absorption-scattering model (SFM) of the radiation field in the photoreactor, combined with reaction kinetics and fluid-dynamic models, has proved to be suitable to describe the degradation of water pollutants in heterogeneous photocatalytic reactors, combining simplicity and accuracy. In this study, the above approach was extended to model the photocatalytic mineralization of a commercial herbicides mixture (2,4-D, diuron, and ametryne used in Colombian sugar cane crops) in a solar, pilot-scale, compound parabolic collector (CPC) photoreactor using a slurry suspension of TiO(2). The ray-tracing technique was used jointly with the SFM to determine the direction of both the direct and diffuse solar photon fluxes and the spatial profile of the local volumetric rate of photon absorption (LVRPA) in the CPC reactor. Herbicides mineralization kinetics with explicit photon absorption effects were utilized to remove the dependence of the observed rate constants from the reactor geometry and radiation field in the photoreactor. The results showed that the overall model fitted the experimental data of herbicides mineralization in the solar CPC reactor satisfactorily for both cloudy and sunny days. Using the above approach kinetic parameters independent of the radiation field in the reactor can be estimated directly from the results of experiments carried out in a solar CPC reactor. The SFM combined with reaction kinetics and fluid-dynamic models proved to be a simple, but reliable model, for solar photocatalytic applications.

Validation of Solar Sail Simulations for the NASA Solar Sail Demonstration Project

NASA Technical Reports Server (NTRS)

Braafladt, Alexander C.; Artusio-Glimpse, Alexandra B.; Heaton, Andrew F.

2014-01-01

NASA's Solar Sail Demonstration project partner L'Garde is currently assembling a flight-like sail assembly for a series of ground demonstration tests beginning in 2015. For future missions of this sail that might validate solar sail technology, it is necessary to have an accurate sail thrust model. One of the primary requirements of a proposed potential technology validation mission will be to demonstrate solar sail thrust over a set time period, which for this project is nominally 30 days. This requirement would be met by comparing a L'Garde-developed trajectory simulation to the as-flown trajectory. The current sail simulation baseline for L'Garde is a Systems Tool Kit (STK) plug-in that includes a custom-designed model of the L'Garde sail. The STK simulation has been verified for a flat plate model by comparing it to the NASA-developed Solar Sail Spaceflight Simulation Software (S5). S5 matched STK with a high degree of accuracy and the results of the validation indicate that the L'Garde STK model is accurate enough to meet the potential future mission requirements. Additionally, since the L'Garde sail deviates considerably from a flat plate, a force model for a non-flat sail provided by L'Garde sail was also tested and compared to a flat plate model in S5. This result will be used in the future as a basis of comparison to the non-flat sail model being developed for STK.

COMPARISON OF CORONAL EXTRAPOLATION METHODS FOR CYCLE 24 USING HMI DATA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arden, William M.; Norton, Aimee A.; Sun, Xudong

2016-05-20

Two extrapolation models of the solar coronal magnetic field are compared using magnetogram data from the Solar Dynamics Observatory /Helioseismic and Magnetic Imager instrument. The two models, a horizontal current–current sheet–source surface (HCCSSS) model and a potential field–source surface (PFSS) model, differ in their treatment of coronal currents. Each model has its own critical variable, respectively, the radius of a cusp surface and a source surface, and it is found that adjusting these heights over the period studied allows for a better fit between the models and the solar open flux at 1 au as calculated from the Interplanetary Magneticmore » Field (IMF). The HCCSSS model provides the better fit for the overall period from 2010 November to 2015 May as well as for two subsets of the period: the minimum/rising part of the solar cycle and the recently identified peak in the IMF from mid-2014 to mid-2015 just after solar maximum. It is found that an HCCSSS cusp surface height of 1.7 R {sub ⊙} provides the best fit to the IMF for the overall period, while 1.7 and 1.9 R {sub ⊙} give the best fits for the two subsets. The corresponding values for the PFSS source surface height are 2.1, 2.2, and 2.0 R {sub ⊙} respectively. This means that the HCCSSS cusp surface rises as the solar cycle progresses while the PFSS source surface falls.« less

Probalistic Models for Solar Particle Events

NASA Technical Reports Server (NTRS)

Adams, James H., Jr.; Xapsos, Michael

2009-01-01

Probabilistic Models of Solar Particle Events (SPEs) are used in space mission design studies to describe the radiation environment that can be expected at a specified confidence level. The task of the designer is then to choose a design that will operate in the model radiation environment. Probabilistic models have already been developed for solar proton events that describe the peak flux, event-integrated fluence and missionintegrated fluence. In addition a probabilistic model has been developed that describes the mission-integrated fluence for the Z>2 elemental spectra. This talk will focus on completing this suite of models by developing models for peak flux and event-integrated fluence elemental spectra for the Z>2 element

Numerical Simulation of a Solar Domestic Hot Water System

NASA Astrophysics Data System (ADS)

Mongibello, L.; Bianco, N.; Di Somma, M.; Graditi, G.; Naso, V.

2014-11-01

An innovative transient numerical model is presented for the simulation of a solar Domestic Hot Water (DHW) system. The solar collectors have been simulated by using a zerodimensional analytical model. The temperature distributions in the heat transfer fluid and in the water inside the tank have been evaluated by one-dimensional models. The reversion elimination algorithm has been used to include the effects of natural convection among the water layers at different heights in the tank on the thermal stratification. A finite difference implicit scheme has been implemented to solve the energy conservation equation in the coil heat exchanger, and the energy conservation equation in the tank has been solved by using the finite difference Euler implicit scheme. Energy conservation equations for the solar DHW components models have been coupled by means of a home-made implicit algorithm. Results of the simulation performed using as input data the experimental values of the ambient temperature and the solar irradiance in a summer day are presented and discussed.

Solar Week 2000: Using role models to encourage an interest in science

NASA Astrophysics Data System (ADS)

Alexander, D.

2000-12-01

Solar Week 2000 is a week-long set of games and activities allowing students to interact directly with solar science and solar scientists. The main goal of Solar Week was to provide young women, primarily in grades 6-8, with access to role models in the sciences. The scientists participating in Solar Week are women from a variety of backgrounds and with a variety of scientific expertise. An online bulletin board was used to foster discussion between the students and the scientists about both science and career issues. In this presentation I will discuss the successes and failures of the first run of Solar Week which occurred on 9-13 October 2000. Our aim is to provide some insight into doing activity-based space science on the web and to discuss the lessons-learned from tailoring to a specific group of participants.

Solar nebula chemistry - Implications for volatiles in the solar system

NASA Technical Reports Server (NTRS)

Fegley, Bruce, Jr.; Prinn, Ronald G.

1989-01-01

Current theoretical models of solar nebula chemistry which take into account the interplay between chemistry and dynamics are presented for the abundant reactive volatile elements including hydrogen, carbon, nitrogen, oxygen, and sulfur. Results of these models indicate that, in the solar nebula, the dominant carbon and nitrogen gases were CO and NO, whereas, in giant planet subnebulae, the dominant carbon and nitrogen gases were CH4 and NH3; in the solar nebula, the Fe metal grains catalyzed the formation of organic compounds from CO and H2 via the Fischer-Tropsch-type reaction. It was also found that, in solar nebula, bulk FeS formation was kinetically favorable, while FeO incorporation into silicates and bulk Fe3O4 formation were kinetically inhibited. Furthermore, clathrate formation was kinetically inhibited in the solar nebula, while it was kinetically favorable in giant planet subnebulae.

A technique for global monitoring of net solar irradiance at the ocean surface. I - Model

NASA Technical Reports Server (NTRS)

Frouin, Robert; Chertock, Beth

1992-01-01

An accurate long-term (84-month) climatology of net surface solar irradiance over the global oceans from Nimbus-7 earth radiation budget (ERB) wide-field-of-view planetary-albedo data is generated via an algorithm based on radiative transfer theory. Net surface solar irradiance is computed as the difference between the top-of-atmosphere incident solar irradiance (known) and the sum of the solar irradiance reflected back to space by the earth-atmosphere system (observed) and the solar irradiance absorbed by atmospheric constituents (modeled). It is shown that the effects of clouds and clear-atmosphere constituents can be decoupled on a monthly time scale, which makes it possible to directly apply the algorithm with monthly averages of ERB planetary-albedo data. Compared theoretically with the algorithm of Gautier et al. (1980), the present algorithm yields higher solar irradiance values in clear and thin cloud conditions and lower values in thick cloud conditions.

Prediction of the solar modulation of galactic cosmic rays and radiation dose of aircrews up to the solar cycle 26

NASA Astrophysics Data System (ADS)

Miyake, S.; Kataoka, R.; Sato, T.

2016-12-01

The solar modulation of galactic cosmic rays (GCRs), which is the variation of the terrestrial GCR flux caused by the heliospheric environmental change, is basically anti-correlated with the solar activity with so-called 11-year periodicity. In the current weak solar cycle 24, we expect that the flux of GCRs is getting higher than that in the previous solar cycles, leading to the increase in the radiation exposure in the space and atmosphere. In order to quantitatively evaluate the possible solar modulation of GCRs and resultant radiation exposure at flight altitude during the solar cycles 24, 25, and 26, we have developed the time-dependent and three-dimensional model of the solar modulation of GCRs. Our model can give the flux of GCRs anywhere in the heliosphere by assuming the variation of the solar wind velocity, the strength of the interplanetary magnetic field, and its tilt angle. We solve the curvature and gradient drift motion of GCRs in the heliospheric magnetic field, and therefore reproduce the 22-year variation of the solar modulation of GCRs. It is quantitatively confirmed that our model reproduces the energy spectra observed by BESS and PAMELA. We then calculate the variation of the GCR energy spectra during the solar cycles 24, 25, and 26, by extrapolating the solar wind parameters and tilt angle. We also calculate the neutron monitor counting rate and the radiation dose of aircrews at flight altitude, by the air-shower simulation performed by PHITS (Particle and Heavy Ion Transport code System). In this presentation, we report the quantitative forecast values of the solar modulation of GCRs, neutron monitor counting rate, and the radiation dose at flight altitude up to the cycle 26, including the discussion of the charge sign dependence on those results.

Analytical analysis of solar thermal collector with glass and Fresnel lens glazing

NASA Astrophysics Data System (ADS)

Zulkifle, Idris; Ruslan, Mohd Hafidz Hj; Othman, Mohd Yusof Hj; Ibarahim, Zahari

2018-04-01

Solar thermal collector is a system that converts solar radiation to heat. The heat will raise the temperature higher than the ambient temperature. Absorber and glazing are two important components in order to increase the temperature of the collector. The thermal absorber will release heat by convection and as radiation to the surrounding. These losses will be reduced by glazing. Other than that, glazing is beneficial for protecting the collector from dust and water. This study discusses about modelling of solar thermal collector effects of different mass flow rates with different glazing for V-groove flat plate solar collectors. The glazing used was the glass and linear Fresnel lens. Concentration ratio in this modelling was 1.3 for 0.1m solar collector thickness. Results show that solar collectors with linear Fresnel lens has the highest efficiency value of 71.18% compared to solar collectors with glass which has efficiency 54.10% with same operation conditions.

Solar origins of solar wind properties during the cycle 23 solar minimum and rising phase of cycle 24

PubMed Central

Luhmann, Janet G.; Petrie, Gordon; Riley, Pete

2012-01-01

The solar wind was originally envisioned using a simple dipolar corona/polar coronal hole sources picture, but modern observations and models, together with the recent unusual solar cycle minimum, have demonstrated the limitations of this picture. The solar surface fields in both polar and low-to-mid-latitude active region zones routinely produce coronal magnetic fields and related solar wind sources much more complex than a dipole. This makes low-to-mid latitude coronal holes and their associated streamer boundaries major contributors to what is observed in the ecliptic and affects the Earth. In this paper we use magnetogram-based coronal field models to describe the conditions that prevailed in the corona from the decline of cycle 23 into the rising phase of cycle 24. The results emphasize the need for adopting new views of what is ‘typical’ solar wind, even when the Sun is relatively inactive. PMID:25685422

Studying the Impact of Distributed Solar PV on Power Systems using Integrated Transmission and Distribution Models: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jain, Himanshu; Palmintier, Bryan S; Krad, Ibrahim

This paper presents the results of a distributed solar PV impact assessment study that was performed using a synthetic integrated transmission (T) and distribution (D) model. The primary objective of the study was to present a new approach for distributed solar PV impact assessment, where along with detailed models of transmission and distribution networks, consumer loads were modeled using the physics of end-use equipment, and distributed solar PV was geographically dispersed and connected to the secondary distribution networks. The highlights of the study results were (i) increase in the Area Control Error (ACE) at high penetration levels of distributed solarmore » PV; and (ii) differences in distribution voltages profiles and voltage regulator operations between integrated T&D and distribution only simulations.« less

Predicting solar radiation based on available weather indicators

NASA Astrophysics Data System (ADS)

Sauer, Frank Joseph

Solar radiation prediction models are complex and require software that is not available for the household investor. The processing power within a normal desktop or laptop computer is sufficient to calculate similar models. This barrier to entry for the average consumer can be fixed by a model simple enough to be calculated by hand if necessary. Solar radiation modeling has been historically difficult to predict and accurate models have significant assumptions and restrictions on their use. Previous methods have been limited to linear relationships, location restrictions, or input data limits to one atmospheric condition. This research takes a novel approach by combining two techniques within the computational limits of a household computer; Clustering and Hidden Markov Models (HMMs). Clustering helps limit the large observation space which restricts the use of HMMs. Instead of using continuous data, and requiring significantly increased computations, the cluster can be used as a qualitative descriptor of each observation. HMMs incorporate a level of uncertainty and take into account the indirect relationship between meteorological indicators and solar radiation. This reduces the complexity of the model enough to be simply understood and accessible to the average household investor. The solar radiation is considered to be an unobservable state that each household will be unable to measure. The high temperature and the sky coverage are already available through the local or preferred source of weather information. By using the next day's prediction for high temperature and sky coverage, the model groups the data and then predicts the most likely range of radiation. This model uses simple techniques and calculations to give a broad estimate for the solar radiation when no other universal model exists for the average household.

Empirical model of TEC response to geomagnetic and solar forcing over Balkan Peninsula

NASA Astrophysics Data System (ADS)

Mukhtarov, P.; Andonov, B.; Pancheva, D.

2018-01-01

An empirical total electron content (TEC) model response to external forcing over Balkan Peninsula (35°N-50°N; 15°E-30°E) is built by using the Center for Orbit Determination of Europe (CODE) TEC data for full 17 years, January 1999 - December 2015. The external forcing includes geomagnetic activity described by the Kp-index and solar activity described by the solar radio flux F10.7. The model describes the most probable spatial distribution and temporal variability of the externally forced TEC anomalies assuming that they depend mainly on latitude, Kp-index, F10.7 and LT. The anomalies are expressed by the relative deviation of the TEC from its 15-day mean, rTEC, as the mean value is calculated from the 15 preceding days. The approach for building this regional model is similar to that of the global TEC model reported by Mukhtarov et al. (2013a) however it includes two important improvements related to short-term variability of the solar activity and amended geomagnetic forcing by using a "modified" Kp index. The quality assessment of the new constructing model procedure in terms of modeling error calculated for the period of 1999-2015 indicates significant improvement in accordance with the global TEC model (Mukhtarov et al., 2013a). The short-term prediction capabilities of the model based on the error calculations for 2016 are improved as well. In order to demonstrate how the model is able to reproduce the rTEC response to external forcing three geomagnetic storms, accompanied also with short-term solar activity variations, which occur at different seasons and solar activity conditions are presented.

Parameter optimization for surface flux transport models

NASA Astrophysics Data System (ADS)

Whitbread, T.; Yeates, A. R.; Muñoz-Jaramillo, A.; Petrie, G. J. D.

2017-11-01

Accurate prediction of solar activity calls for precise calibration of solar cycle models. Consequently we aim to find optimal parameters for models which describe the physical processes on the solar surface, which in turn act as proxies for what occurs in the interior and provide source terms for coronal models. We use a genetic algorithm to optimize surface flux transport models using National Solar Observatory (NSO) magnetogram data for Solar Cycle 23. This is applied to both a 1D model that inserts new magnetic flux in the form of idealized bipolar magnetic regions, and also to a 2D model that assimilates specific shapes of real active regions. The genetic algorithm searches for parameter sets (meridional flow speed and profile, supergranular diffusivity, initial magnetic field, and radial decay time) that produce the best fit between observed and simulated butterfly diagrams, weighted by a latitude-dependent error structure which reflects uncertainty in observations. Due to the easily adaptable nature of the 2D model, the optimization process is repeated for Cycles 21, 22, and 24 in order to analyse cycle-to-cycle variation of the optimal solution. We find that the ranges and optimal solutions for the various regimes are in reasonable agreement with results from the literature, both theoretical and observational. The optimal meridional flow profiles for each regime are almost entirely within observational bounds determined by magnetic feature tracking, with the 2D model being able to accommodate the mean observed profile more successfully. Differences between models appear to be important in deciding values for the diffusive and decay terms. In like fashion, differences in the behaviours of different solar cycles lead to contrasts in parameters defining the meridional flow and initial field strength.

The Space Weather Modeling Framework (SWMF): Models and Validation

NASA Astrophysics Data System (ADS)

Gombosi, Tamas; Toth, Gabor; Sokolov, Igor; de Zeeuw, Darren; van der Holst, Bart; Ridley, Aaron; Manchester, Ward, IV

In the last decade our group at the Center for Space Environment Modeling (CSEM) has developed the Space Weather Modeling Framework (SWMF) that efficiently couples together different models describing the interacting regions of the space environment. Many of these domain models (such as the global solar corona, the inner heliosphere or the global magneto-sphere) are based on MHD and are represented by our multiphysics code, BATS-R-US. SWMF is a powerful tool for coupling regional models describing the space environment from the solar photosphere to the bottom of the ionosphere. Presently, SWMF contains over a dozen components: the solar corona (SC), eruptive event generator (EE), inner heliosphere (IE), outer heliosphere (OH), solar energetic particles (SE), global magnetosphere (GM), inner magnetosphere (IM), radiation belts (RB), plasmasphere (PS), ionospheric electrodynamics (IE), polar wind (PW), upper atmosphere (UA) and lower atmosphere (LA). This talk will present an overview of SWMF, new results obtained with improved physics as well as some validation studies.

Baseline and target values for regional and point PV power forecasts: Toward improved solar forecasting

DOE PAGES

Zhang, Jie; Hodge, Bri -Mathias; Lu, Siyuan; ...

2015-11-10

Accurate solar photovoltaic (PV) power forecasting allows utilities to reliably utilize solar resources on their systems. However, to truly measure the improvements that any new solar forecasting methods provide, it is important to develop a methodology for determining baseline and target values for the accuracy of solar forecasting at different spatial and temporal scales. This paper aims at developing a framework to derive baseline and target values for a suite of generally applicable, value-based, and custom-designed solar forecasting metrics. The work was informed by close collaboration with utility and independent system operator partners. The baseline values are established based onmore » state-of-the-art numerical weather prediction models and persistence models in combination with a radiative transfer model. The target values are determined based on the reduction in the amount of reserves that must be held to accommodate the uncertainty of PV power output. The proposed reserve-based methodology is a reasonable and practical approach that can be used to assess the economic benefits gained from improvements in accuracy of solar forecasting. Lastly, the financial baseline and targets can be translated back to forecasting accuracy metrics and requirements, which will guide research on solar forecasting improvements toward the areas that are most beneficial to power systems operations.« less

Cosmic ray modulation and radiation dose of aircrews during the solar cycle 24/25

NASA Astrophysics Data System (ADS)

Miyake, Shoko; Kataoka, Ryuho; Sato, Tatsuhiko

2017-04-01

Weak solar activity and high cosmic ray flux during the coming solar cycle are qualitatively anticipated by the recent observations that show the decline in the solar activity levels. We predict the cosmic ray modulation and resultant radiation exposure at flight altitude by using the time-dependent and three-dimensional model of the cosmic ray modulation. Our galactic cosmic ray (GCR) model is based on the variations of the solar wind speed, the strength of the heliospheric magnetic field, and the tilt angle of the heliospheric current sheet. We reproduce the 22 year variation of the cosmic ray modulation from 1980 to 2015 taking into account the gradient-curvature drift motion of GCRs. The energy spectra of GCR protons obtained by our model show good agreement with the observations by the Balloon-borne Experiment with a Superconducting magnetic rigidity Spectrometer (BESS) and the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) except for a discrepancy at the solar maximum. Five-year annual radiation dose around the solar minimum at the solar cycle 24/25 will be approximately 19% higher than that in the last cycle. This is caused by the charge sign dependence of the cosmic ray modulation, such as the flattop profiles in a positive polarity.

An examination of astrophysical habitats for targeted SETI

NASA Technical Reports Server (NTRS)

Doyle, Laurance R.; Mckay, Christopher P.; Reynolds, Ray T.; Whitmire, Daniel P.; Matese, John J.

1991-01-01

Planetary atmospheric radiative transfer models have recently given valuable insights into the definition of the solar system's ecoshell. In addition, however, results have indicated that constraints on solar evolution also need to be addressed, with even minor solar variations, (mass loss, for example), having important consequences from an exobiological standpoint. Following the definition of the solar system's ecoshell evolution, the ecoshells around different stellar spectral types can then be modeled. In this study the astrophysical constraints on the definition of ecoshells and possible exobiological habitats includes: (1) the investigation of the evolution of the solar system's ecoshell under different initial solar/stellar model conditions as indicated by both solar abundance considerations as well as planetary evidence; (2) an outline of considerations necessary to define the ecoshells around the most abundant spectral-type stars, the K and M stars looking at the effects on exobiological habitats of planetary rotational tidal locking effects, and stellar flare/chromospheric-activity cycles, among other effects; (3) a preliminary examination of the factors defining the expected ecoshells around binary stars determining the of regular stellar eclipses, and the expected shortening of the semi-major axis. These results can then be applied to the targeted microwave search for extraterrestrial intelligent signals by constraining the ecoshell space in the solar neighborhood.

Advanced interface modelling of n-Si/HNO3 doped graphene solar cells to identify pathways to high efficiency

NASA Astrophysics Data System (ADS)

Zhao, Jing; Ma, Fa-Jun; Ding, Ke; Zhang, Hao; Jie, Jiansheng; Ho-Baillie, Anita; Bremner, Stephen P.

2018-03-01

In graphene/silicon solar cells, it is crucial to understand the transport mechanism of the graphene/silicon interface to further improve power conversion efficiency. Until now, the transport mechanism has been predominantly simplified as an ideal Schottky junction. However, such an ideal Schottky contact is never realised experimentally. According to literature, doped graphene shows the properties of a semiconductor, therefore, it is physically more accurate to model graphene/silicon junction as a Heterojunction. In this work, HNO3-doped graphene/silicon solar cells were fabricated with the power conversion efficiency of 9.45%. Extensive characterization and first-principles calculations were carried out to establish an advanced technology computer-aided design (TCAD) model, where p-doped graphene forms a straddling heterojunction with the n-type silicon. In comparison with the simple Schottky junction models, our TCAD model paves the way for thorough investigation on the sensitivity of solar cell performance to graphene properties like electron affinity. According to the TCAD heterojunction model, the cell performance can be improved up to 22.5% after optimizations of the antireflection coatings and the rear structure, highlighting the great potentials for fabricating high efficiency graphene/silicon solar cells and other optoelectronic devices.

A GENERALIZED TWO-COMPONENT MODEL OF SOLAR WIND TURBULENCE AND AB INITIO DIFFUSION MEAN-FREE PATHS AND DRIFT LENGTHSCALES OF COSMIC RAYS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiengarten, T.; Fichtner, H.; Kleimann, J.

2016-12-10

We extend a two-component model for the evolution of fluctuations in the solar wind plasma so that it is fully three-dimensional (3D) and also coupled self-consistently to the large-scale magnetohydrodynamic equations describing the background solar wind. The two classes of fluctuations considered are a high-frequency parallel-propagating wave-like piece and a low-frequency quasi-two-dimensional component. For both components, the nonlinear dynamics is dominanted by quasi-perpendicular spectral cascades of energy. Driving of the fluctuations by, for example, velocity shear and pickup ions is included. Numerical solutions to the new model are obtained using the Cronos framework, and validated against previous simpler models. Comparing results frommore » the new model with spacecraft measurements, we find improved agreement relative to earlier models that employ prescribed background solar wind fields. Finally, the new results for the wave-like and quasi-two-dimensional fluctuations are used to calculate ab initio diffusion mean-free paths and drift lengthscales for the transport of cosmic rays in the turbulent solar wind.« less

Data challenges in estimating the capacity value of solar photovoltaics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gami, Dhruv; Sioshansi, Ramteen; Denholm, Paul

We examine the robustness of solar capacity-value estimates to three important data issues. The first is the sensitivity to using hourly averaged as opposed to subhourly solar-insolation data. The second is the sensitivity to errors in recording and interpreting load data. The third is the sensitivity to using modeled as opposed to measured solar-insolation data. We demonstrate that capacity-value estimates of solar are sensitive to all three of these factors, with potentially large errors in the capacity-value estimate in a particular year. If multiple years of data are available, the biases introduced by using hourly averaged solar-insolation can be smoothedmore » out. Multiple years of data will not necessarily address the other data-related issues that we examine. Our analysis calls into question the accuracy of a number of solar capacity-value estimates relying exclusively on modeled solar-insolation data that are reported in the literature (including our own previous works). Lastly, our analysis also suggests that multiple years’ historical data should be used for remunerating solar generators for their capacity value in organized wholesale electricity markets.« less

Data Challenges in Estimating the Capacity Value of Solar Photovoltaics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gami, Dhruv; Sioshansi, Ramteen; Denholm, Paul

We examine the robustness of solar capacity-value estimates to three important data issues. The first is the sensitivity to using hourly averaged as opposed to subhourly solar-insolation data. The second is the sensitivity to errors in recording and interpreting load data. The third is the sensitivity to using modeled as opposed to measured solar-insolation data. We demonstrate that capacity-value estimates of solar are sensitive to all three of these factors, with potentially large errors in the capacity-value estimate in a particular year. If multiple years of data are available, the biases introduced by using hourly averaged solar-insolation can be smoothedmore » out. Multiple years of data will not necessarily address the other data-related issues that we examine. Our analysis calls into question the accuracy of a number of solar capacity-value estimates relying exclusively on modeled solar-insolation data that are reported in the literature (including our own previous works). Our analysis also suggests that multiple years' historical data should be used for remunerating solar generators for their capacity value in organized wholesale electricity markets.« less

Analysis of each branch current of serial solar cells by using an equivalent circuit model

NASA Astrophysics Data System (ADS)

Yi, Shi-Guang; Zhang, Wan-Hui; Ai, Bin; Song, Jing-Wei; Shen, Hui

2014-02-01

In this paper, based on the equivalent single diode circuit model of the solar cell, an equivalent circuit diagram for two serial solar cells is drawn. Its equations of current and voltage are derived from Kirchhoff's current and voltage law. First, parameters are obtained from the I—V (current—voltage) curves for typical monocrystalline silicon solar cells (125 mm × 125 mm). Then, by regarding photo-generated current, shunt resistance, serial resistance of the first solar cell, and resistance load as the variables. The properties of shunt currents (Ish1 and Ish2), diode currents (ID1 and ID2), and load current (IL) for the whole two serial solar cells are numerically analyzed in these four cases for the first time, and the corresponding physical explanations are made. We find that these parameters have different influences on the internal currents of solar cells. Our results will provide a reference for developing higher efficiency solar cell module and contribute to the better understanding of the reason of efficiency loss of solar cell module.

Data challenges in estimating the capacity value of solar photovoltaics

DOE PAGES

Gami, Dhruv; Sioshansi, Ramteen; Denholm, Paul

2017-04-30

We examine the robustness of solar capacity-value estimates to three important data issues. The first is the sensitivity to using hourly averaged as opposed to subhourly solar-insolation data. The second is the sensitivity to errors in recording and interpreting load data. The third is the sensitivity to using modeled as opposed to measured solar-insolation data. We demonstrate that capacity-value estimates of solar are sensitive to all three of these factors, with potentially large errors in the capacity-value estimate in a particular year. If multiple years of data are available, the biases introduced by using hourly averaged solar-insolation can be smoothedmore » out. Multiple years of data will not necessarily address the other data-related issues that we examine. Our analysis calls into question the accuracy of a number of solar capacity-value estimates relying exclusively on modeled solar-insolation data that are reported in the literature (including our own previous works). Lastly, our analysis also suggests that multiple years’ historical data should be used for remunerating solar generators for their capacity value in organized wholesale electricity markets.« less

Solar activity simulation and forecast with a flux-transport dynamo

NASA Astrophysics Data System (ADS)

Macario-Rojas, Alejandro; Smith, Katharine L.; Roberts, Peter C. E.

2018-06-01

We present the assessment of a diffusion-dominated mean field axisymmetric dynamo model in reproducing historical solar activity and forecast for solar cycle 25. Previous studies point to the Sun's polar magnetic field as an important proxy for solar activity prediction. Extended research using this proxy has been impeded by reduced observational data record only available from 1976. However, there is a recognised need for a solar dynamo model with ample verification over various activity scenarios to improve theoretical standards. The present study aims to explore the use of helioseismology data and reconstructed solar polar magnetic field, to foster the development of robust solar activity forecasts. The research is based on observationally inferred differential rotation morphology, as well as observed and reconstructed polar field using artificial neural network methods via the hemispheric sunspot areas record. Results show consistent reproduction of historical solar activity trends with enhanced results by introducing a precursor rise time coefficient. A weak solar cycle 25, with slow rise time and maximum activity -14.4% (±19.5%) with respect to the current cycle 24 is predicted.

Helioseismology: A probe of the solar interior, atmosphere, and activity cycle

NASA Technical Reports Server (NTRS)

Rhodes, E. J., Jr.

1995-01-01

Helioseismology began in earnest in the mid 1970's. In the two decades which have elapsed since that time this branch of solar physics has become a mature field of research. Helioseismology has demonstrated that the solar convection zone is about twice as deep as was generally thought to be the case before 1977. Helioseismology has also provided measurements of the solar internal angular velocity over much of the sun's interior. Helioseismology has also ruled out models which would solve the solar neutrino problem by a lowering of the temperature of the core. Recently, some of the seismic properties of the sun have been demonstrated to vary with changing levels of solar activity. Also, helioseismology has recently provided evidence for helical flow patterns in the shallow, sub-photosphere layers. The techniques of helioseismology are also expanding to include seismic probes of solar active regions. Some work is also being conducted into the possible contributions of the solar acoustic models to the heating of the solar atmosphere. In this talk I will highlight a few of the above results and concentrate on current areas of research in the field.

Combining Remote and In Situ Observations with MHD models to Understand the Formation of the Slow Solar Wind

NASA Astrophysics Data System (ADS)

Viall, N. M.; Kepko, L.; Antiochos, S. K.; Lepri, S. T.; Vourlidas, A.; Linker, J.

2017-12-01

Connecting the structure and variability in the solar corona to the Heliosphere and solar wind is one of the main goals of Heliophysics and space weather research. The instrumentation and viewpoints of the Parker Solar Probe and Solar Orbiter missions will provide an unprecedented opportunity to combine remote sensing with in situ data to determine how the corona drives the Heliosphere, especially as it relates to the origin of the slow solar wind. We present analysis of STEREO coronagraph and heliospheric imager observations and of in situ ACE and Wind measurements that reveal an important connection between the dynamics of the corona and of the solar wind. We show observations of quasi-periodic release of plasma into the slow solar wind occurring throughout the corona - including regions away from the helmet streamer and heliospheric current sheet - and demonstrate that these observations place severe constraints on the origin of the slow solar wind. We build a comprehensive picture of the dynamic evolution by combining remote imaging data, in situ composition and magnetic connectivity information, and MHD models of the solar wind. Our results have critical implications for the magnetic topology involved in slow solar wind formation and magnetic reconnection dynamics. Crucially, this analysis pushes the limits of current instrument resolution and sensitivity, showing the enormous potential science to be accomplished with the Parker Solar Probe and Solar Orbiter missions.

Improved Statistical Model Of 10.7-cm Solar Radiation

NASA Technical Reports Server (NTRS)

Vedder, John D.; Tabor, Jill L.

1993-01-01

Improved mathematical model simulates short-term fluctuations of flux of 10.7-cm-wavelength solar radiation during 91-day averaging period. Called "F10.7 flux", important as measure of solar activity and because it is highly correlated with ultraviolet radiation causing fluctuations in heating and density of upper atmosphere. F10.7 flux easily measureable at surface of Earth.

Organic and Hybrid Organic Solid-State Photovoltaic Materials and Devices

DTIC Science & Technology

2014-03-06

Microscopy Research, 2012, 7, 158-169. Organic photovoltaic materials, hybrid organic devices, solar cells 6 1 FINAL TECHNICAL REPORT 1... hybrids have potential applications in solar cells and may thus provide mobile energy sources for aircraft and soldier technologies. Modeling and...modeling and simulation developed in this project are encouraging further development. 2. Technical Activities Hybrid organic solar cells are an

Improved Solar-Radiation-Pressure Models for GPS Satellites

NASA Technical Reports Server (NTRS)

Bar-Sever, Yoaz; Kuang, Da

2006-01-01

A report describes a series of computational models conceived as an improvement over prior models for determining effects of solar-radiation pressure on orbits of Global Positioning System (GPS) satellites. These models are based on fitting coefficients of Fourier functions of Sun-spacecraft- Earth angles to observed spacecraft orbital motions.

Virtual Solar System Project: Building Understanding through Model Building.

ERIC Educational Resources Information Center

Barab, Sasha A.; Hay, Kenneth E.; Barnett, Michael; Keating, Thomas

2000-01-01

Describes an introductory astronomy course for undergraduate students in which students use three-dimensional (3-D) modeling tools to model the solar system and develop rich understandings of astronomical phenomena. Indicates that 3-D modeling can be used effectively in regular undergraduate university courses as a tool to develop understandings…

Similarity Rules for Scaling Solar Sail Systems

NASA Technical Reports Server (NTRS)

Canfield, Stephen L.; Peddieson, John; Garbe, Gregory

2010-01-01

Future science missions will require solar sails on the order of 200 square meters (or larger). However, ground demonstrations and flight demonstrations must be conducted at significantly smaller sizes, due to limitations of ground-based facilities and cost and availability of flight opportunities. For this reason, the ability to understand the process of scalability, as it applies to solar sail system models and test data, is crucial to the advancement of this technology. This paper will approach the problem of scaling in solar sail models by developing a set of scaling laws or similarity criteria that will provide constraints in the sail design process. These scaling laws establish functional relationships between design parameters of a prototype and model sail that are created at different geometric sizes. This work is applied to a specific solar sail configuration and results in three (four) similarity criteria for static (dynamic) sail models. Further, it is demonstrated that even in the context of unique sail material requirements and gravitational load of earth-bound experiments, it is possible to develop appropriate scaled sail experiments. In the longer term, these scaling laws can be used in the design of scaled experimental tests for solar sails and in analyzing the results from such tests.

An Update to the NASA Reference Solar Sail Thrust Model

NASA Technical Reports Server (NTRS)

Heaton, Andrew F.; Artusio-Glimpse, Alexandra B.

2015-01-01

An optical model of solar sail material originally derived at JPL in 1978 has since served as the de facto standard for NASA and other solar sail researchers. The optical model includes terms for specular and diffuse reflection, thermal emission, and non-Lambertian diffuse reflection. The standard coefficients for these terms are based on tests of 2.5 micrometer Kapton sail material coated with 100 nm of aluminum on the front side and chromium on the back side. The original derivation of these coefficients was documented in an internal JPL technical memorandum that is no longer available. Additionally more recent optical testing has taken place and different materials have been used or are under consideration by various researchers for solar sails. Here, where possible, we re-derive the optical coefficients from the 1978 model and update them to accommodate newer test results and sail material. The source of the commonly used value for the front side non-Lambertian coefficient is not clear, so we investigate that coefficient in detail. Although this research is primarily designed to support the upcoming NASA NEA Scout and Lunar Flashlight solar sail missions, the results are also of interest to the wider solar sail community.

Solar Irradiance Data Products at the LASP Interactive Solar IRradiance Datacenter (LISIRD)

NASA Astrophysics Data System (ADS)

Ware Dewolfe, A.; Wilson, A.; Lindholm, D. M.; Pankratz, C. K.; Snow, M. A.; Woods, T. N.

2010-12-01

The Laboratory for Atmospheric and Space Physics (LASP) has developed the LASP Interactive Solar IRradiance Datacenter (LISIRD) to provide access to a comprehensive set of solar irradiance measurements. LISIRD has recently been updated to serve many new datasets and models, including data from SORCE, UARS-SOLSTICE, SME, and TIMED-SEE, and model data from the Flare Irradiance Spectral Model (FISM). The user interface emphasizes web-based interactive visualizations, allowing users to explore and compare this data before downloading it for analysis. The data provided covers a wavelength range from soft X-ray (XUV) at 0.1 nm up to the near infrared (NIR) at 2400 nm, as well as wavelength-independent Total Solar Irradiance (TSI). Combined data from the SORCE, TIMED-SEE, UARS-SOLSTICE, and SME instruments provide continuous coverage from 1981 to the present, while Lyman-alpha measurements, FISM daily data, and TSI models date from the 1940s to the present. LISIRD will also host Glory TSI data as part of the SORCE data system. This poster provides an overview of the LISIRD system, summarizes the data sets currently available, describes future plans and capabilities, and provides details on how to access solar irradiance data through LISIRD’s interfaces.

Global Magnetohydrodynamic Modeling of the Solar Corona

NASA Technical Reports Server (NTRS)

Linker, Jon A.

1998-01-01

The coronal magnetic field defines the structure of the solar corona, the position of the heliospheric current sheet, the regions of fast and slow solar wind, and the most likely sites of coronal mass ejections. There are few measurements of the magnetic fields in the corona, but the line-of-sight component of the global magnetic fields in the photosphere have been routinely measured for many years (for example, at Stanford's Wilcox Solar Observatory, and at the National Solar Observatory at Kitt Peak). The SOI/MDI instrument is now providing high-resolution full-disk magnetograms several times a day. Understanding the large-scale structure of the solar corona and inner heliosphere requires accurately mapping the measured photospheric magnetic field into the corona and outward. Ideally, a model should not only extrapolate the magnetic field, but should self-consistently reconstruct both the plasma and magnetic fields in the corona and solar wind. Support from our NASA SR&T contract has allowed us to develop three-dimensional magnetohydrodynamic (MHD) computations of the solar corona that incorporate observed photospheric magnetic fields into the boundary conditions. These calculations not only describe the magnetic field in the corona and interplanetary spice, but also predict the plasma properties as well. Our computations thus far have been successful in reproducing many aspects of both coronal and interplanetary data, including the structure of the streamer belt, the location of coronal hole boundaries, and the position and shape of the heliospheric current sheet. The most widely used technique for extrapolating the photospheric magnetic field into the corona and heliosphere are potential field models, such as the potential field source-surface model (PFSS),and the potential field current-sheet (PFCS) model

Model predictive control of a solar-thermal reactor

NASA Astrophysics Data System (ADS)

Saade Saade, Maria Elizabeth

Solar-thermal reactors represent a promising alternative to fossil fuels because they can harvest solar energy and transform it into storable and transportable fuels. The operation of solar-thermal reactors is restricted by the available sunlight and its inherently transient behavior, which affects the performance of the reactors and limits their efficiency. Before solar-thermal reactors can become commercially viable, they need to be able to maintain a continuous high-performance operation, even in the presence of passing clouds. A well-designed control system can preserve product quality and maintain stable product compositions, resulting in a more efficient and cost-effective operation, which can ultimately lead to scale-up and commercialization of solar thermochemical technologies. In this work, we propose a model predictive control (MPC) system for a solar-thermal reactor for the steam-gasification of biomass. The proposed controller aims at rejecting the disturbances in solar irradiation caused by the presence of clouds. A first-principles dynamic model of the process was developed. The model was used to study the dynamic responses of the process variables and to identify a linear time-invariant model used in the MPC algorithm. To provide an estimation of the disturbances for the control algorithm, a one-minute-ahead direct normal irradiance (DNI) predictor was developed. The proposed predictor utilizes information obtained through the analysis of sky images, in combination with current atmospheric measurements, to produce the DNI forecast. In the end, a robust controller was designed capable of rejecting disturbances within the operating region. Extensive simulation experiments showed that the controller outperforms a finely-tuned multi-loop feedback control strategy. The results obtained suggest that our controller is suitable for practical implementation.

Simulations of Solar Jets

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-02-01

Formation of a coronal jet from twisted field lines that have reconnected with the ambient field. The colors show the radial velocity of the plasma. [Adapted from Szente et al. 2017]How do jets emitted from the Suns surface contribute to its corona and to the solar wind? In a recent study, a team of scientists performed complex three-dimensional simulations of coronal jets to answer these questions.Small ExplosionsCoronal jets are relatively small eruptions from the Suns surface, with heights of roughly 100 to 10,000 km, speeds of 10 to 1,000 km/s, and lifetimes of a few minutes to around ten hours. These jets are constantly present theyre emitted even from the quiet Sun, when activity is otherwise low and weve observed them with a fleet of Sun-watching space telescopes spanning the visible, extreme ultraviolet (EUV), and X-ray wavelength bands.A comparison of simulated observations based on the authors model (left panels) to actual EUV and X-ray observations of jets (right panels). [Szente et al. 2017]Due to their ubiquity, we speculate that these jets might contribute to heating the global solar corona (which is significantly hotter than the surface below it, a curiosity known as the coronal heating problem). We can also wonder what role these jets might play in driving the overall solar wind.Launching a JetLed by Judit Szente (University of Michigan), a team of scientists has explored the impact of coronal jets on the global corona and solar wind with a series of numerical simulations. Szente and collaborators used three-dimensional, magnetohydrodynamic simulations that provide realistic treatment of the solar atmosphere, the solar wind acceleration, and the complexities of heat transfer throughout the corona.In the authors simulations, a jet is initiated as a magnetic dipole rotates at the solar surface, winding up field lines. Magnetic reconnection between the twisted lines and the background field then launches the jet from the dense and hot solar chromosphere, and erupting plasma is released outward into the solar corona.A second comparison of simulated observations based on the authors model (left panels) to actual EUV observations of jets (right panels). [Szente et al. 2017]Global InfluencesAfter demonstrating that their models could successfully lead to jet production and propagation, Szente and collaborators compared their results to actual observations of solar jets. The authors constructed simulated EUV and X-ray observations of their modeled events, and they verified that the behavior and structures in these simulated observations were very similar to real observations of coronal jet events from telescopes like SDO/AIA and Hinode.With this confirmed, the authors then used their models to determine how the jets influence the global solar corona and the solar wind. They found that the large-scale corona is significantly affected by the plasma waves from the jet, which travel across 40 in latitude and out to 24 solar radii. In spite of this, the simulated jets contributed only a few percent to the steady-state solar-wind energy outflow.These simulations represent an important step in realistic modeling of the quiet Sun. Because the models make specific predictions about temperature and density gradients within the corona, we can look forward to testing them with upcoming missions like Solar Probe Plus, which should be able to explore the Sun all the way down to ninesolar radii.CitationJ. Szente et al 2017 ApJ 834 123. doi:10.3847/1538-4357/834/2/123

A Model for Optimizing the Combination of Solar Electricity Generation, Supply Curtailment, Transmission and Storage

NASA Astrophysics Data System (ADS)

Perez, Marc J. R.

With extraordinary recent growth of the solar photovoltaic industry, it is paramount to address the biggest barrier to its high-penetration across global electrical grids: the inherent variability of the solar resource. This resource variability arises from largely unpredictable meteorological phenomena and from the predictable rotation of the earth around the sun and about its own axis. To achieve very high photovoltaic penetration, the imbalance between the variable supply of sunlight and demand must be alleviated. The research detailed herein consists of the development of a computational model which seeks to optimize the combination of 3 supply-side solutions to solar variability that minimizes the aggregate cost of electricity generated therefrom: Storage (where excess solar generation is stored when it exceeds demand for utilization when it does not meet demand), interconnection (where solar generation is spread across a large geographic area and electrically interconnected to smooth overall regional output) and smart curtailment (where solar capacity is oversized and excess generation is curtailed at key times to minimize the need for storage.). This model leverages a database created in the context of this doctoral work of satellite-derived photovoltaic output spanning 10 years at a daily interval for 64,000 unique geographic points across the globe. Underpinning the model's design and results, the database was used to further the understanding of solar resource variability at timescales greater than 1-day. It is shown that--as at shorter timescales--cloud/weather-induced solar variability decreases with geographic extent and that the geographic extent at which variability is mitigated increases with timescale and is modulated by the prevailing speed of clouds/weather systems. Unpredictable solar variability up to the timescale of 30 days is shown to be mitigated across a geographic extent of only 1500km if that geographic extent is oriented in a north/south bearing. Using technical and economic data reflecting today's real costs for solar generation technology, storage and electric transmission in combination with this model, we determined the minimum cost combination of these solutions to transform the variable output from solar plants into 3 distinct output profiles: A constant output equivalent to a baseload power plant, a well-defined seasonally-variable output with no weather-induced variability and a variable output but one that is 100% predictable on a multi-day ahead basis. In order to do this, over 14,000 model runs were performed by varying the desired output profile, the amount of energy curtailment, the penetration of solar energy and the geographic region across the continental United States. Despite the cost of supplementary electric transmission, geographic interconnection has the potential to reduce the levelized cost of electricity when meeting any of the studied output profiles by over 65% compared to when only storage is used. Energy curtailment, despite the cost of underutilizing solar energy capacity, has the potential to reduce the total cost of electricity when meeting any of the studied output profiles by over 75% compared to when only storage is used. The three variability mitigation strategies are thankfully not mutually exclusive. When combined at their ideal levels, each of the regions studied saw a reduction in cost of electricity of over 80% compared to when only energy storage is used to meet a specified output profile. When including current costs for solar generation, transmission and energy storage, an optimum configuration can conservatively provide guaranteed baseload power generation with solar across the entire continental United States (equivalent to a nuclear power plant with no down time) for less than 0.19 per kilowatt-hour. If solar is preferentially clustered in the southwest instead of evenly spread throughout the United States, and we adopt future expected costs for solar generation of 1 per watt, optimal model results show that meeting a 100% predictable output target with solar will cost no more than $0.08 per kilowatt-hour.

Curve fitting methods for solar radiation data modeling

NASA Astrophysics Data System (ADS)

Karim, Samsul Ariffin Abdul; Singh, Balbir Singh Mahinder

2014-10-01

This paper studies the use of several type of curve fitting method to smooth the global solar radiation data. After the data have been fitted by using curve fitting method, the mathematical model of global solar radiation will be developed. The error measurement was calculated by using goodness-fit statistics such as root mean square error (RMSE) and the value of R2. The best fitting methods will be used as a starting point for the construction of mathematical modeling of solar radiation received in Universiti Teknologi PETRONAS (UTP) Malaysia. Numerical results indicated that Gaussian fitting and sine fitting (both with two terms) gives better results as compare with the other fitting methods.

Curve fitting methods for solar radiation data modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karim, Samsul Ariffin Abdul, E-mail: samsul-ariffin@petronas.com.my, E-mail: balbir@petronas.com.my; Singh, Balbir Singh Mahinder, E-mail: samsul-ariffin@petronas.com.my, E-mail: balbir@petronas.com.my

2014-10-24

This paper studies the use of several type of curve fitting method to smooth the global solar radiation data. After the data have been fitted by using curve fitting method, the mathematical model of global solar radiation will be developed. The error measurement was calculated by using goodness-fit statistics such as root mean square error (RMSE) and the value of R{sup 2}. The best fitting methods will be used as a starting point for the construction of mathematical modeling of solar radiation received in Universiti Teknologi PETRONAS (UTP) Malaysia. Numerical results indicated that Gaussian fitting and sine fitting (both withmore » two terms) gives better results as compare with the other fitting methods.« less

Incorporating photon recycling into the analytical drift-diffusion model of high efficiency solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lumb, Matthew P.; Naval Research Laboratory, Washington, DC 20375; Steiner, Myles A.

The analytical drift-diffusion formalism is able to accurately simulate a wide range of solar cell architectures and was recently extended to include those with back surface reflectors. However, as solar cells approach the limits of material quality, photon recycling effects become increasingly important in predicting the behavior of these cells. In particular, the minority carrier diffusion length is significantly affected by the photon recycling, with consequences for the solar cell performance. In this paper, we outline an approach to account for photon recycling in the analytical Hovel model and compare analytical model predictions to GaAs-based experimental devices operating close tomore » the fundamental efficiency limit.« less

Recent Developments in Smart Adaptive Structures for Solar Sailcraft

NASA Technical Reports Server (NTRS)

Whorton, M. S.; Kim, Y. K.; Oakley, J.; Adetona, O.; Keel, L. H.

2007-01-01

The "Smart Adaptive Structures for Solar Sailcraft" development activity at MSFC has investigated issues associated with understanding how to model and scale the subsystem and multi-body system dynamics of a gossamer solar sailcraft with the objective of designing sailcraft attitude control systems. This research and development activity addressed three key tasks that leveraged existing facilities and core competencies of MSFC to investigate dynamics and control issues of solar sails. Key aspects of this effort included modeling and testing of a 30 m deployable boom; modeling of the multi-body system dynamics of a gossamer sailcraft; investigation of control-structures interaction for gossamer sailcraft; and development and experimental demonstration of adaptive control technologies to mitigate control-structures interaction.

Improving Soft X-Ray Spectral Irradiance Models for Use Throughout the Solar System

NASA Astrophysics Data System (ADS)

Eparvier, F. G.; Thiemann, E.; Woods, T. N.

2017-12-01

Understanding the effects of solar variability on planetary atmospheres has been hindered by the lack of accurate models and measurements of the soft x-ray (SXR) spectral irradiance (0-6 nm). Most measurements of the SXR have been broadband and are difficult to interpret due to changing spectral distribution under the pass band of the instruments. Models that use reference spectra for quiet sun, active region, and flaring contributions to irradiance have been made, but with limited success. The recent Miniature X-ray Solar Spectrometer (MinXSS) CubeSat made spectral measurements in the 0.04 - 3 nm range from June 2016 to May 2017, observing the Sun at many different levels of activity. In addition, the Solar Dynamics Observatory (SDO) EUV Variability Experiment (EVE) has observed the Sun since May 2010, in both broad bands (including a band at 0-7 nm) and spectrally resolved (6-105 nm at 0.1 nm resolution). We will present an improved model of the SXR based on new reference spectra from MinXSS and SDO-EVE. The non-flaring portion of the model is driven by broadband SXR measurements for determining activity level and relative contributions of quiet and active sun. Flares are modeled using flare temperatures from the GOES X-Ray Sensors. The improved SXR model can be driven by any sensors that provide a measure of activity level and flare temperature from any vantage point in the solar system. As an example, a version of the model is using the broadband solar irradiance measurements from the MAVEN EUV Monitor at Mars will be presented.

Seismological comparisons of solar models with element diffusion using the MHD, OPAL, and SIREFF equations of state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guzik, J.A.; Swenson, F.J.

We compare the thermodynamic and helioseismic properties of solar models evolved using three different equation of state (EOS) treatments: the Mihalas, D{umlt a}ppen & Hummer EOS tables (MHD); the latest Rogers, Swenson, & Iglesias EOS tables (OPAL), and a new analytical EOS (SIREFF) developed by Swenson {ital et al.} All of the models include diffusive settling of helium and heavier elements. The models use updated OPAL opacity tables based on the 1993 Grevesse & Noels solar element mixture, incorporating 21 elements instead of the 14 elements used for earlier tables. The properties of solar models that are evolved with themore » SIREFF EOS agree closely with those of models evolved using the OPAL or MHD tables. However, unlike the MHD or OPAL EOS tables, the SIREFF in-line EOS can readily account for variations in overall Z abundance and the element mixture resulting from nuclear processing and diffusive element settling. Accounting for Z abundance variations in the EOS has a small, but non-negligible, effect on model properties (e.g., pressure or squared sound speed), as much as 0.2{percent} at the solar center and in the convection zone. The OPAL and SIREFF equations of state include electron exchange, which produces models requiring a slightly higher initial helium abundance, and increases the convection zone depth compared to models using the MHD EOS. However, the updated OPAL opacities are as much as 5{percent} lower near the convection zone base, resulting in a small decrease in convection zone depth. The calculated low-degree nonadiabatic frequencies for all of the models agree with the observed frequencies to within a few microhertz (0.1{percent}). The SIREFF analytical calibrations are intended to work over a wide range of interior conditions found in stellar models of mass greater than 0.25M{sub {circle_dot}} and evolutionary states from pre-main-sequence through the asymptotic giant branch (AGB). It is significant that the SIREFF EOS produces solar models that both measure up to the stringent requirements imposed by solar oscillation observations and inferences, and are more versatile than EOS tables. {copyright} {ital 1997} {ital The American Astronomical Society}« less