Solar Flux Measurements Research Articles

Bifacial Photovоltaic Sensor for Insolation Energy Resource Monitoring

Accurate and reliable measurements of the total solar radiation flux make it possible to evaluate the efficiency of using stand-alone photovaltaic systems in various meteorological conditions. These measurements allow more accurately predict in time the energy production volume, accumulator and capacitive storage devices parameters and the payback period. Research purpose was to study the possibility of creating a photoelectric sensor and a method of uninterrupted measurement based on this sensor which allows to measure total solar radiation flux including its direct, diffused and reflected components simultaneously. The photovaltaic sensor with bifacial photosensitivity was manufactured and applied, which is low-inertia comparing to traditional thermoelectric pyranometers, and its spectral sensitivity is quite close to the same parameter of photovoltaic power supply system. It creates the possibility to estimate the insolation level capable to be completely converted into electrical energy without an ineffective heat-generating long-wavelength part of the solar spectrum. A laboratory measuring stand was made to test the sensor's operability. Modeling and experiments’ the sensor parameters were carried out and confirmed its operability. The bifacial photosensitivity sensor allows to control simultaneously direct, diffused and reflected from the earth's surface components of solar radiation, what gives more complete information about the energy potential of the photovoltaic power supply system location.

Measurement of solar pp neutrino flux using electron recoil data from PandaX-4T commissioning run* *This project is supported in part by the grants from the National Science Foundation of China (12090060, 12090063, 12105052, 12005131, 11905128, 11925502), the Office of Science and Technology, Shanghai Municipal Government (22JC1410100), and the National Science Foundation of Sichuan Province, China (2024NSFSC1371). We are grateful for

The proton-proton ( ) fusion chain dominates the neutrino production in the Sun. The uncertainty of the predicted neutrino flux is at the sub-percent level, whereas that of the best measurement is (10%). In this study, for the first time, we measure solar neutrinos in the electron recoil energy range from 24 to 144 keV using the PandaX-4T commissioning data with 0.63 tonne year exposure. The neutrino flux is determined as , which is consistent with the Standard Solar Model and existing measurements, corresponding to an upper flux limit of at 90% C.L..

Search for Periodic Time Variations of the Solar B8 Neutrino Flux between 1996 and 2018 in Super-Kamiokande

We report a search for time variations of the solar B8 neutrino flux using 5804 live days of Super-Kamiokande data collected between May 31, 1996, and May 30, 2018. Super-Kamiokande measured the precise time of each solar neutrino interaction over 22 calendar years to search for solar neutrino flux modulations with unprecedented precision. Periodic modulations are searched for in a dataset comprising five-day interval solar neutrino flux measurements with a maximum likelihood method. We also applied the Lomb-Scargle method to this dataset to compare it with previous reports. The only significant modulation found is due to the elliptic orbit of the Earth around the Sun. The observed modulation is consistent with astronomical data: we measured an eccentricity of (1.53±0.35)%, and a perihelion shift of (−1.5±13.5) days. Published by the American Physical Society 2024

An uncertainty methodology for solar occultation flux measurements: ammonia emissions from livestock production

Abstract. Ammonia (NH3) emissions can negatively affect ecosystems and human health, so they should be monitored and mitigated. This study presents methodology for the estimation of uncertainties in NH3 emissions measurements using the solar occultation flux (SOF) method. The reactive nature of NH3 makes its measurement challenging, but SOF offers a reliable open-path passive method which utilizes solar spectrum data, thereby avoiding gas adsorption within the instrument. To compute NH3 gas fluxes, horizontal and vertical wind speed profiles, as well as plume height estimates and spatially resolved column measurements, are integrated. A unique aspect of this work is the first-time description of plume height estimations derived from ground and column NH3 concentration measurements aimed at uncertainty reduction. Initial validation tests indicated measurement errors between −31 % and +14 % on average, which was slightly larger than the estimated expanded uncertainty ranging from ± 12 % to ± 17 %. Application of the methodology to assess emission rates from farms of various sizes showed uncertainties between ± 21 % and ± 37 %, generally influenced by systematic wind uncertainties and random errors. The method demonstrates the capacity to measure NH3 emissions from both small (∼ 0.5–1 kg h−1) and large (∼ 100 kg h−1) sources in high-density farming areas. Generally, the SOF method provided an expanded uncertainty below 30 % in measuring NH3 emissions from livestock production, which could be further improved by adhering to best application practices. This paper's findings offer the potential for broader applications, such as measuring NH3 fluxes from fertilized fields and in the oil and gas sector. However, these applications would require further research to adapt and refine the methodologies for these specific contexts.

Correlation analysis of solar flux absolute measurements at 161 and 245 MHz

Solar emission in meter waves originates from upper layers of the solar corona. We present absolute measurements of solar flux from Irkutsk Incoherent Scatter Radar (161 MHz frequency) and Learmonth Observatory (245 MHz frequency). We perform correlation analysis to investigate the relation between solar flux values at different frequencies. Background emission of the quiet Sun is within the expected limits. We examine the behavior of background and slowly-varying emission components during a solar cycle. By comparing the Pearson correlation coefficient with the Spearman rank correlation coefficient, we have found that the dependence of the meter flux on the F10.7 index is non-linear. The correlation between solar flux measurements at 161 and 245 MHz appeared to be lower than that with the F10.7 index. Analysis of daily correlation and autocorrelation shows a diurnal variation that introduces an error into the measurements.

Корреляционный анализ абсолютных измерений солнечного потока на частотах 161 и 245 МГц

Solar emission in meter waves originates from upper layers of the solar corona. We present absolute measurements of solar flux from Irkutsk Incoherent Scatter Radar (161 MHz frequency) and Learmonth Observatory (245 MHz frequency). We perform correlation analysis to investigate the relation between solar flux values at different frequencies. Background emission of the quiet Sun is within the expected limits. We examine the behavior of background and slowly-varying emission components during a solar cycle. By comparing the Pearson correlation coefficient with the Spearman rank correlation coefficient, we have found that the dependence of the meter flux on the F10.7 index is non-linear. The correlation between solar flux measurements at 161 and 245 MHz appeared to be lower than that with the F10.7 index. Analysis of daily correlation and autocorrelation shows a diurnal variation that introduces an error into the measurements.

GNSS Solar Astronomy in real-time during more than one solar cycle

This work presents a summary of the continuous non-stop (hereinafter 24/7) real-time measurement and warning system for EUV solar activity, which is based on worldwide multifrequency Global Navigation Satellite Systems (GNSS) observations. The system relies on continuous tracking of the intensity of expected global patterns in the Earth’s ionosphere’s free electron distribution, which are associated with solar flares. The paper includes a discussion on the foundations of GNSS Solar Astronomy, along with details on its real-time implementation that began in 2011. Furthermore, a summary of the corresponding validation is provided, comparing it to external and direct solar EUV flux measurements obtained from SOHO-SEM. Finally, there will be a brief mention of the ongoing efforts to extend this technique to detect huge extra-solar sources.

Recent results from Borexino on solar neutrinos

Borexino has been a neutrino detector based on ultrapure liquid scintillator, located at the Laboratori Nazionali del Gran Sasso, Italy. Its main scientific goal was the real-time measurement of solar neutrino fluxes, which play an irreplaceable role for the comprehension of the mechanisms powering our star. Over the past two years, the Borexino collaboration has pursued the improvement of the CNO flux measurement, obtaining further indications about the solar metallicity. In a parallel way, Borexino has demonstrated for the first time the possibility of exploiting the directional Cherenkov information, in a liquid scintillator detector, for the detection of sub-MeV solar neutrinos.

Modeling Solar Eclipses at Extreme Ultra Violet Wavelengths and the Effects of Nonuniform Eclipse Shadow on the Ionosphere‐Thermosphere System

AbstractThe impacts of solar eclipses on the ionosphere‐thermosphere system particularly the composition, density, and transport are studied using numerical simulation and subsequent model‐data comparison. We introduce a newly developed model of a solar eclipse mask (shadow) at extreme ultraviolet (EUV) wavelengths—PyEclipse—that computes the corresponding shadowing as a function of space, time, and wavelength of the input solar image. The current model includes interfaces for Solar Dynamics Observatory and Geostationary Operational Environmental Satellites EUV telescopes providing solar images at nine different wavelengths. We show the significance of the EUV eclipse shadow spatial variability and that it varies significantly with wavelength owing to the highly variable solar coronal emissions. We demonstrate geometrical differences between the EUV eclipse shadow compared to a geometrically symmetric simplification revealing changes in occultation vary ±20%. The EUV eclipse mask is validated with in situ solar flux measurements by the PRoject for Onboard Autonomy 2/Large Yield Radiometer instrument suite showing the model captures the morphology and amplitudes of transient variability while the modeled gradients are slower. The effects of spatially EUV eclipse masks are investigated with Global Ionosphere Thermosphere Model for the 21 August 2017 eclipse. The results reveal that the modeled EUV eclipse mask, in comparison with the geometrically symmetric approximation, causes changes in the Total Electron Content in order of ±20%, 5%–20% in F‐region plasma drift, and 20%–30% in F‐region neutral winds.

Over seven decades of solar microwave data obtained with Toyokawa and Nobeyama Radio Polarimeters

AbstractMonitoring observations of solar microwave fluxes and their polarization began in Japan during the 1950s at Toyokawa and Mitaka. At present (April 2022), monitoring observations continues with the Nobeyama Radio Polarimeters (NoRP) at the Nobeyama campus of the National Astronomical Observatory of Japan (NAOJ). In this paper, we present a brief history of the solar microwave monitoring observations preceding those now carried out by NoRP. We then review the solar microwave flux and polarization measurements obtained at Toyokawa and Nobeyama, and their metadata. The datasets are publicly provided by the Solar Data Archive System (SDAS) operated by the Astronomy Data Center of the NAOJ, via http (https://solar.nro.nao.ac.jp/norp/) and FTP (ftp://solar‐pub.nao.ac.jp/pub/nsro/norp/) protocols.

Solar constraints on captured electrophilic dark matter

Dark matter captured by interaction with electrons inside the Sun may annihilate via long-lived mediator to produce observable gamma ray signals. We utilize solar gamma ray flux measurements from the Fermi Large Area Telescope and the High Altitude Water Cherenkov observatory to put bounds on the dark matter electron-scattering cross section. We find that our limits are four to six orders of magnitude stronger than the existing limits for dark matter masses ranging between GeV to PeV scale.

Slow-fluor scintillator for low energy solar neutrinos and neutrinoless double beta decay

The potential for using slow-fluor liquid scintillators to study low energy solar neutrinos and neutrinoless double beta decay (0nbb) is explored through a series of simulations. The fluorescence model assumed for the primary fluor has characteristics similar to acenaphthene, recently used to demonstrate Cherenkov separation at energies around 1 MeV. Results here indicate notably better directional reconstruction in large-scale detectors than has previously been suggested by other approaches, allowing better identification of low energy solar neutrinos. These studies indicate that a detector with as little as ~30% coverage using currently available photomultiplier tubes could be able to make a measurement of the CNO solar neutrino flux to a precision of better than 10% (enough to distinguish metallicity models) with a few kiloton-years of exposure. In terms of 0nbb studies here suggest that the ability to separate mechanisms based on angular distributions is weak, but that the rejection of solar neutrino backgrounds with such a technique might potentially approach a factor of 10 for endpoint energies near 2.5 MeV in the angular hemisphere defined by the solar direction.

RMCSat: An F10.7 Solar Flux Index CubeSat Mission

The F10.7 solar flux index is a measure of microwave solar emissions at a wavelength of 10.7 cm or 2800 MHz. It is widely used in thermosphere and ionosphere models as an indicator of solar activity and is recorded at only one terrestrial observatory in Penticton, Canada during daylight hours. The lack of geographical and temporal coverage of F10.7 measurements and no external redundancy to the existing system has led to the development of the RMCSat mission, which seeks to demonstrate the feasibility of collecting microwave solar flux emissions from a space-based platform. RMCSat is the first CubeSat mission by the Royal Military College of Canada. It offers a training environment for personnel in space mission analysis and design, satellite assembly, integration and testing, and satellite operations. This paper introduces the mission concept and preliminary design of a space-based solution that captures solar density flux measurements during each orbit as the Sun passes through the boresight of the primary payload antenna. In addition to two channels recording the 2800 MHz frequency (2785 MHz and 2815 MHz), a third channel records 2695 MHz using the same calibration standard to determine if the United States Radio Solar Telescope Network (RSTN) could be leveraged to supplement the existing F10.7 solar flux measurements and improve solar flux approximations. The RMCSat mission, satellite design, and system budgets are demonstrated here as being viable. Future design considerations pertain to the payload antennas and achievable launch orbits.

Expected sensitivity to test of standard solar models with future solar CNO neutrino flux measurement

Standard solar models built from spectroscopy and from the helioseismology predicted inconsistent solar metallicity. Solar neutrino fluxes can be used to test two models. Hypothesis test was performed using 7Be, 8B CNO neutrino fluxes. Current experimental results already disfavored the low metallicity standard solar model at a significance of 2.1 σ. Considering new experiments that can improve the precision of the measured CNO neutrino flux are being planned, it is important to study their potentiality to discriminating two standard solar models. We evaluated the expected significance to reject the low metallicity solar model where the assumed central value and uncertainty of the measured CNO neutrino flux vary within the range of 3.5 × 108 -- 8 × 108 s−1cm−2 and 1%--20%, respectively. It was found that the potentiality of future experiments to reject the low metallicity standard solar model strongly depends on the central value of the CNO neutrino flux measurement. When the central value is the same as the value measured by Borexino in 2020, the required precision to reach 3 σ and 5 σ are 20% and 8%, respectively, which are both achievable.

Response of Mars's Topside Ionosphere to Changing Solar Activity and Comparisons to Venus

AbstractStudying how planetary ionospheres respond to changes in solar irradiance can inform our understanding of how planetary atmospheres have reacted to our changing Sun over the course of solar system history. The response of Mars's main ionospheric peak to changing solar irradiance has been well‐studied. Less well understood are the altitudes above the main peak. We use radio occultation observations by Mars Global Surveyor and ground‐based solar radio flux measurements to quantify the response of Mars's electron densities to changing solar irradiance at these altitudes. This analysis shows that the electron densities respond modestly at and just above the main peak, with the response increasing above or below the peak. We use a one‐dimensional photochemical equilibrium model to reproduce the observed electron densities and investigate the influence of minor ions, changing electron temperatures, and changing neutral densities and composition on the resultant electron density. We find that the neutral atmosphere is primarily responsible for the observed behavior. We also make comparisons to Venus, which shows a more dramatic increase in its ionospheric response as a function of altitude. We show that while the ionospheric responses of Mars and Venus as a function of altitude are markedly different, recasting the analysis in terms of number of scale heights above the main peak brings the two planets into closer agreement, especially at the main peak. The agreement is worse at higher altitudes and this is attributed to Venus's larger proportion of atomic oxygen.

Sensitivity to neutrinos from the solar CNO cycle in Borexino

Neutrinos emitted in the carbon, nitrogen, oxygen (CNO) fusion cycle in the Sun are a sub-dominant, yet crucial component of solar neutrinos whose flux has not been measured yet. The Borexino experiment at the Laboratori Nazionali del Gran Sasso (Italy) has a unique opportunity to detect them directly thanks to the detector’s radiopurity and the precise understanding of the detector backgrounds. We discuss the sensitivity of Borexino to CNO neutrinos, which is based on the strategies we adopted to constrain the rates of the two most relevant background sources, pep neutrinos from the solar pp-chain and ^{210}Bi beta decays originating in the intrinsic contamination of the liquid scintillator with ^{210}Pb. Assuming the CNO flux predicted by the high-metallicity Standard Solar Model and an exposure of 1000 days times 71.3 t, Borexino has a median sensitivity to CNO neutrino higher than 3 sigma . With the same hypothesis the expected experimental uncertainty on the CNO neutrino flux is 23%, provided the uncertainty on the independent estimate of the ^{210}text {Bi} interaction rate is 1.5 hbox {cpd}/100~hbox {ton} . Finally, we evaluated the expected uncertainty of the C and N abundances and the expected discrimination significance between the high and low metallicity Standard Solar Models (HZ and LZ) with future more precise measurement of the CNO solar neutrino flux.

LONG-TERM SOLAR FLUX OBSERVATIONS WITH IRKUTSK INCOHERENT SCATTER RADAR (IISR) IN 2011–2019

Irkutsk incoherent scatter radar (IISR) is an oblongish horn antenna that operates in a meter waveband (154–162 MHz), has a 0.5°×20° beam, and a frequency steering allowing us to tilt the beam by 30° to the south. Besides active measurements of ionospheric conditions and monitoring of space objects, the radar is regularly used for passive radio astronomical observations. From May to August, the Sun crosses the radar field of view and can be in the maximum of the radiation pattern for about two hours. The known shape of the radiation pattern and the high sensitivity of the receiver allow us to conduct calibrated measurements of the solar flux in solar flux units during this period. We have developed a new approach to the calibration, which can be applied to all IISR archival passive data. In the paper, we present long-term observations (2011–2019) of the solar flux in May and summer. We describe the measurement method, present daily average values of the solar flux for this period of passive measurements, and compare it with the solar activity F10.7 index and solar flux measurements made at the Australian observatory Learmonth at 245 MHz. We show that the daily average flux for the period of observations at a frequency of ~161 MHz generally has values from 5 to 10 sfu.

Длительные наблюдения солнечного потока в 2011–2019 гг. на Иркутском радаре некогерентного рассеяния (ИРНР)

Irkutsk incoherent scatter radar (IISR) is an oblongish horn antenna that operates in a meter waveband (154–162 MHz), has a 0.5°×20° beam, and a frequency steering allowing us to tilt the beam by 30° to the south. Besides active measurements of ionospheric conditions and monitoring of space objects, the radar is regularly used for passive radio astronomical observations. From May to August, the Sun crosses the radar field of view and can be in the maximum of the radiation pattern for about two hours. The known shape of the radiation pattern and the high sensitivity of the receiver allow us to conduct calibrated measurements of the solar flux in solar flux units during this period. We have developed a new approach to the calibration, which can be applied to all IISR archival passive data. In the paper, we present long-term observations (2011–2019) of the solar flux in May and summer. We describe the measurement method, present daily average values of the solar flux for this period of passive measurements, and compare it with the solar activity F10.7 index and solar flux measurements made at the Australian observatory Learmonth at 245 MHz. We show that the daily average flux for the period of observations at a frequency of ~161 MHz generally has values from 5 to 10 sfu.

Assessing Rapid Variability in Atmospheric Apparent Optical Depth with an Array Spectrometer System

A method for determining rapid variations in atmospheric optical depth is proposed. The method is based upon computation of the ratio between close-time spectral measurements of solar direct flux. Use of the ratio avoids the need for absolute calibration of the instruments and minimizes the effects of changes in instrumental conditions (such as temperature or mechanical adjustments) and in air mass. The technique has been applied to some campaigns of measurement for sky conditions ranging from clear skies to scattered-to-broken cloudiness, performed at high frequency (~1Hz) with a system of three array spectrometers, capable of performing very rapid spectral acquisitions, in the 400 to 1700 nm band, thus covering the visible and extending to the near-infrared spectral ranges. Results demonstrate the capacity of this instrumentation and method to detect rapid variation of optical depth, as well as rapid changes in its spectral pattern. The optical depth variability depends on the particular state of the sky and is connected to particle condensation and evaporation processes and to the changes in water vapor content in the transition region between cloud-free and cloudy regions. Thus, the method is suitable for analyzing rapid processes involving particles, either aerosol or cloud droplets, and water vapor, in the cloud boundaries.

Background analysis for the SNO+ experiment

SNO+ is a large multi-purpose liquid scintillator based experiment, with the main physics goal of searching for the neutrinoless double-beta decay of 130Te. The first of the three SNO+ phases started in May 2017, with the detector filled with ultra-pure water. The deep underground location (6000 m.w.e.) and the low background levels allowed new physics searches, together with the measurement of the 8B solar neutrino flux in the 5-15 MeV energy range. Recently, SNO+ has began the transition to the scintillator phase. The double-beta decay phase is expected to start in early 2020, when the ultra-pure liquid scintillator will be loaded with 3.9 tonnes of natural tellurium, for a half-life sensitivity larger than 2×1026 years in 5 years of data taking. This article focuses on the low background measurement of the initial water phase.