Solar Luminosity Research Articles

La luce della luna: lucifluus in Zenone di Verona (Tract. 1.2.19) e Isidoro di Siviglia (Nat. 18.1; Etym. 3.53.1)

Abstract In Etym. 3.53.1 and Nat. 18.1, Isidore of Seville describes the nature of moonlight, primarily drawing on Augustine’s commentary on Psalm 10. In the chapter of De natura rerum, he also explores specific allegorical meanings of the moon, already established in patristic exegesis, particularly referencing the symbolism of the resurrection of the dead. To indicate the shining part of the moon’s surface, Isidore employs the rare adjectival compound lucifluus, first attested in Juvencus’ Evangeliorum libri with reference to the sun and, metaphorically, to the Gospel. Significantly, this adjective is already used in a context similar to Isidore’s, in the second sermon (De resurrectione) of the first book of the Tractatus by Zeno of Verona (Tract. 1.2.19). In this sermon, the author offers a brief allegorical excursus on the moon, interpreting it as a symbol of mortal man and his future resurrection at the end of time. With some distinctions, he uses the same adjective to describe the brightness of the sun in relation to that of the moon. This close analogy in context and content suggests that Isidore, particularly in the passage from De natura rerum, might have considered Zeno’s sermon when reusing the term lucifluus.

Constraints on the early luminosity history of the Sun: applications to the Faint Young Sun problem

ABSTRACT Stellar evolution theory predicts that the Sun was fainter in the past, which can pose difficulties for understanding Earth’s climate history. One proposed solution to this Faint Young Sun (FYS) problem is a more luminous Sun in the past. In this paper, we address the robustness of the solar luminosity history using the yrec code to compute solar models including rotation, magnetized winds, and the associated mass-loss. We present detailed solar models, including their evolutionary history, which are in excellent agreement with solar observables. Consistent with prior standard models, we infer a high solar metal content. We provide predicted X-ray luminosities and rotation histories for usage in climate reconstructions and activity studies. We find that the Sun’s luminosity deviates from the standard solar model trajectory by at most 0.5 per cent during the Archean (corresponding to a radiative forcing of 0.849 W m$^{-2}$). The total mass-loss experienced by solar models is modest because of strong feedback between mass and angular momentum loss. We find a maximum mass-loss of $1.35 \times 10^{-3} \,{\rm M}_\odot$ since birth, at or below the level predicted by empirical estimates. The associated maximum luminosity increase falls well short of the level necessary to solve the FYS problem. We present compilations of paleotemperature and CO$_2$ reconstructions. One-dimensional ‘inverse’ climate models demonstrate a mismatch between the solar constant needed to reach high temperatures (e.g. 60–80 $^{\circ }$C) and the narrow range of plausible solar luminosities determined in this study. Maintaining a temperate Earth, however, is plausible given these conditions.

Intelligent and Optimal System for Monitoring Environmental Variables and Solar Luminosity, with solar path tracker and telemetry

In this proposed research are analyzed general solutions and techniques to optimize the solar luminosity measurement by a designed smart system, as well as its usability by the solar energy conversion and its storing. However, many times, this kind of systems have not an optimal solar path tracker and as a consequence it can not be measured the full solar luminosity during all the day, therefore, in this work are designed optimal mathematical models and algorithms to enhance the solar path tracker according to measure solar luminosity and getting optimal solar energy conversion/storing, which is useful to study geographical conditions before to build solar energy conversion centers. As well as, in this research also is studied and suggested some techniques to get wireless data communication regarding the measured environmental variables, measured solar luminosity and stored electrical energy as a consequence of the solar energy conversion, which can be transmitted, so far away, to a central monitoring center by Radio Frequency (RF) waves.

Extreme-ultraviolet Polarimetric Diagnostics of the Solar Corona: The Hanle Effect of Ne viii 770 Å

Magnetic fields are the primary driver of the plasma thermodynamics in the upper solar atmosphere, especially in the corona. However, magnetic field measurements in the solar corona are sporadic, thereby limiting us from the complete understanding of physical processes occurring in the coronal plasma. In this paper, we explore the diagnostic potential of a coronal emission line in the extreme-ultraviolet, i.e., Ne viii 770 Å, to probe the coronal magnetic fields. We utilize 3D “Magnetohydrodynamic Algorithm outside a Sphere” models as input to the FORWARD code to model polarization in the Ne viii line produced as a result of resonance scattering, and we interpret its modification due to collisions and the magnetic fields through the Hanle effect. The polarization maps are synthesized both on the disk and off the limb. The variation of this polarization signal through the different phases of Solar Cycle 24 and the beginning phase of Solar Cycle 25 is studied in order to understand the magnetic diagnostic properties of this line owing to different physical conditions in the solar atmosphere. The detectability of the linear polarization signatures of the Hanle effect significantly improves with increasing solar activity, consistent with the increase in the magnetic field strength and the intensity of the mean solar brightness at these wavelengths. We finally discuss the signal-to-noise ratio requirements by considering realistic instrument designs.

Variability of Atomic Hydrogen Brightness in the Martian Exosphere: Insights From the Emirates Ultraviolet Spectrometer on Board Emirates Mars Mission

AbstractThe Emirates Mars Ultraviolet Spectrometer (EMUS), aboard the Emirates Mars Mission (EMM), has been conducting observations of ultraviolet emissions within the Martian exosphere. Taking advantage of the distinctive orbit of the EMM around Mars, EMUS utilizes a dedicated strafe observation strategy to scan the illuminated Martian exosphere at tangential altitudes ranging from 130 to over 20,000 km. To distinguish between emissions of Martian origin and those from the interplanetary background, EMUS conducts specialized background observations by looking away from the planet. This approach has allowed us to investigate the radial and seasonal variations in Martian coronal emission features at H Lyman‐α, β and γ wavelengths. Our analysis supports the previous studies indicating that Martian exospheric hydrogen Lyman emission brightness attains its highest levels around the southern summer solstice and reaches its lowest levels when Mars is near aphelion. Additionally, a secondary peak emission at all altitudes is observed after perihelion during Martian Year (MY) 36, which can be attributed to a Class C dust storm. Our study establishes a strong correlation between solar flux and coronal brightness for these emissions, highlighting the impact of solar activity on the visibility of Martian corona. In addition, we have examined interannual variability and found that emission intensities in MY 37 surpassed those in MY 36, primarily due to increased solar activity. These observations help to understand potential seasonal patterns of exospheric hydrogen, which is driven by underlying mechanisms in the lower atmosphere and solar activity, eventually suggesting an impact on water loss in the Martian atmosphere.

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Peranan Matahari Muda yang Malap dalam Kimia Pra-Biotik: Dari Perspektif Kimia tentang Polimerisasi Pra-Biotik

The faint young sun (FYS) was introduced as a paradox by prominent astronomer Carl Sagan dan George Mullen. This paradox posits that the luminosity of the sun 4.6 billion years ago (when it came into existence) was less than 30% of its current luminosity. The variation in solar radiance might have facilitated the Origin of Life (OOL) on Earth by influencing prebiotic chemistry, especially in the formation of prebiotic polyester. Polyester, synthesized from alpha hydroxy acids(ɑHAs), serves as a model studied as a framework that facilitates OOL. Studies indicate that polyester gels can form from dehydration reactions of ɑHAs in wet-dry cycles, potentially initiating prebiotic life. Moreover, various investigations have demonstrated that ultraviolet UV light has been known to initiate prebiotic chemical reactions, as well as produce polyester. However, experiments have been done, but none has truly explored broadband light from the FYS. Furthermore, prebiotic polymerization induced by FYS has not been shown. In this paper, we will discuss about FYS, some research conducted regarding prebiotic reactions induced by UV light, and the prospects of how FYS’ broadband light might be beneficial for prebiotic polymerization involving polyester.

Thermal processing of primordial pebbles in evolving protoplanetary disks

During protoplanetary disk formation, dust grains located in the outer disk retain their pristine icy composition, while solids in the inner stellar-heated disk undergo volatile loss. This process may have left a fossil record in Solar System material, showing different nucleosynthetic imprints that have been attributed to different degrees of thermal processing. However, it remains unclear how a large mass fraction of thermally processed inner-disk pebbles is produced and how these grains are subsequently transported throughout the disk. In this work, we numerically investigate the evolution in time of a two-component pebble disk consisting of both pristine pebbles and those that underwent ice sublimation. We find that stellar outbursts exceeding 1000 times the solar luminosity are efficient in thermally altering, through ice sublimation, a large mass fraction of pebbles (around 80%). After the establishment of this initial radial dust composition gradient throughout the disk, the subsequent mixing and inward drift of pristine outer-disk pebbles alter the inner disk bulk composition from processed to more unprocessed in time. Therefore, if processed pebbles without ice mantles have an isotopic composition similar to ureilite meteorites from the inner Solar System, inner-disk minor bodies forming from the early pebble flux (<1 Myr) will be isotopically ureilite-like, while later-formed bodies will be increasingly admixed with the signature of the lateincoming, CI chondrite-like unprocessed pebbles. This appears to be largely consistent with the trend seen between the accretion age of different meteoric classes and their different stable isotope composition anomalies (in μ54Cr, μ48Ca, μ30Si, and μ58Ni), but further work may be needed to explain the role of isotopically anomalous refractory inclusions and anomaly trends in other elements. Our findings further support an early thermal processing of ice mantles via stellar outbursts that are common around young Sun-like stars.

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Context. The Sun is an extraordinary workbench, on which several fundamental astronomical parameters can be measured with high precision. Among these parameters, the solar radius R⊙ plays an important role in several aspects, for instance, in evolutionary models. Moreover, it conveys information about the structure of the different layers that compose the solar interior and its atmosphere. Despite the efforts to obtain accurate measurements of R⊙, the subject is still debated, and measurements are puzzling and/or lacking in many frequency ranges. Aims. We determine the mean, equatorial, and polar radii of the Sun (Rc, Req, and Rpol) in the frequency range 18.1 − 26.1 GHz. We employed single-dish observations from the newly appointed Medicina Gavril Grueff Radio Telescope and the Sardinia Radio Telescope (SRT) in five years, from 2018 to mid-2023, in the framework of the SunDish project for solar monitoring. Methods. Two methods for calculating the radius at radio frequencies were employed and compared: the half-power, and the inflection point. To assess the quality of our radius determinations, we also analysed the possible degrading effects of the antenna beam pattern on our solar maps using two 2D models (ECB and 2GECB). We carried out a correlation analysis with the evolution of the solar cycle by calculating Pearson’s correlation coefficient ρ in the 13-month running means. Results. We obtained several values for the solar radius, ranging between 959 and 994 arcsec, and ρ, with typical errors of a few arcseconds. These values constrain the correlation between the solar radius and solar activity, and they allow us to estimate the level of solar prolatness in the centimeter frequency range. Conclusions. Our R⊙ measurements are consistent with the values reported in the literature, and they provide refined estimates in the centimeter range. The results suggest a weak prolateness of the solar limb (Req > Rpol), although Req and Rpol are statistically compatible within 3σ errors. The correlation analysis using the solar images from the Grueff Radio Telescope shows (1) a positive correlation between solar activity and the temporal variation in Rc (and Req) at all observing frequencies, and (2) a weak anti-correlation between the temporal variation of Rpol and solar activity at 25.8 GHz.

Study of solar brightness profiles in the 18–26 GHz frequency range with INAF radio telescopes

Context. One of the most important objectives of solar physics is to gain a physical understanding of the solar atmosphere, whose structure can also be described in terms of the density (N) and temperature (T) distributions of the atmospheric matter. Several multi-frequency analyses have shown that the characteristics of these distributions are still under debate, especially for outer coronal emission. Aims. We aim to constrain the T and N distributions of the solar atmosphere through observations in the centimetric radio domain. We employed single-dish observations from two of the INAF radio telescopes at the K-band frequencies (18–26 GHz). We investigated the origin of the significant brightness temperature (TB) detected up to the upper corona (at an altitude of ∼800 mm with respect to the photospheric solar surface). Methods. To probe the physical origin of the atmospheric emission and to constrain instrumental biases, we reproduced the solar signal by convolving specific 2D antenna beam models. We performed an analysis of the solar atmosphere by adopting a physical model that assumes the thermal bremsstrahlung as the emission mechanism, with specific T and N distributions. We compared the modelled TB profiles with those observed by averaging solar maps obtained at 18.3 and 25.8 GHz during the minimum of solar activity (2018–2020). Results. We probed any possible discrepancies between the T and N distributions assumed from the model and those derived from our measurements. The T and N distributions are compatible (within a 25% of uncertainty) with the model up to ∼60 mm and ∼100 mm in altitude, respectively. Conclusions. Our analysis of the role of the antenna beam pattern on our solar maps proves the physical nature of the atmospheric emission in our images up to the coronal tails seen in our TB profiles. Our results suggest that the modelled T and N distributions are in good agreement (within 25% of uncertainty) with our solar maps up to altitudes of ≲100 mm. A subsequent, more challenging analysis of the coronal radio emission at higher altitudes, together with the data from satellite instruments, will require further multi-frequency measurements.

High-latitude platform carbonate deposition constitutes a climate conundrum at the terminal Mesoproterozoic

During the Mesoproterozoic Era, 1600 to 1000 million years ago, global climate was warm with very little evidence of glaciation. Substantial greenhouse warming would have been required to sustain this ice-free state given 5-18% lower solar luminosity. Paleomagnetic data reported here place voluminous ca. 1.2 Ga shallow marine carbonate deposits from India at an unexpectedly high latitude of around 70° from the equator. Previous studies noted high latitudes, but their implication was never considered. Here, we evaluate the temporal-latitudinal distribution of neritic carbonate deposits across the Proterozoic and identify similar deposits from North China that together with those from India are seemingly unique to the late Mesoproterozoic. A uniformitarian interpretation implies that this is cold-water carbonate deposition, but facies similarity with low-latitude neritic deposits rather suggests a hotter climate and elevated polar ocean temperatures of 15–20° or higher. This interpretation represents a climate conundrum that would require much greater greenhouse warming than documented for the Mesoproterozoic.

Physiological adaptations of the Japanese plum tree for agricultural productivity: A promising crop for high altitude tropics

The Japanese plum tree is of great importance in the productive development of Colombian fruit growers due to its nutritional contribution to human health, its great adaptability in the tropical highlands, and its good yields. This review presents the current investigative state of physiology of this plant and its management in tropical highlands, including aspects such as its ecophysiology, forced production, gas exchange, flowering, pollination, and fruit development. In Colombia, Japanese plum production systems are adapted between 1,670 and 2,900 m a.s.l., average solar brightness of 1,400 h per year, 12 h photoperiods, temperatures between 14 and 20°C during the day and 6 and 8°C during the night, and rainfall between 700 and 1,600 mm per year. Under these conditions, management can be implemented to produce cyclical crops of the Japanese plum. This management consists of the selection of varieties with low chilling requirement, chemical defoliation, proper fertilization, fruit and green pruning, and the application of chemical substances that promote the breaking of flower buds. Flowering and pollination require a high specificity so that they do not present incompatibility. The growth and development of the fruit requires 1,538 degree days until harvest. This review indicates the great adaptability, management, and production of Japanese plum in the Colombian high tropics.

Status of direct determination of solar neutrino fluxes after Borexino

We determine the solar neutrino fluxes from the global analysis of the most up-to-date terrestrial and solar neutrino data including the final results of the three phases of Borexino. The analysis are performed in the framework of three-neutrino mixing with and without accounting for the solar luminosity constraint. We discuss the independence of the results on the input from the Gallium experiments. The determined fluxes are then compared with the predictions provided by the latest Standard Solar Models. We quantify the dependence of the model comparison with the assumptions about the normalization of the solar neutrino fluxes produced in the CNO-cycle as well as on the particular set of fluxes employed for the model testing.

Identification of Variables Affecting Levels of Salt Concentrations in Shatt Al-Arab Water Using Modified Kernel Principal Component Analysis

This study paper is an attempt to bring to light a new approach in the treatment of the Gaussian function. The Gaussian function is considered the basis for building the elements of the kernel matrix within the methodology of the kernel principal components that aims to reduce the dimensions and then determine the most influential variables. Besides, it works on reducing the mathematical complexity that can arise because of multidimensionality, especially if it is the data suffers from a non-linear problem in describing the relationships. This research paper has included processing the introductory parameter matrix (H) by adopting two types of matrices, namely (H 1 diagonal, and H 2 hybrid diagonal). For achieving the benefit of this paper, it has been applied to the phenomenon of salt concentrations in Shatt al-Arab water in Basra Governorate through a number of climatic variables for identification of the most influential variables. The modified Gaussian function (MGK) was used and compared with the traditional method (TGK) by adopting two methods of estimating the introductory parameter matrix H. The simulation results brought to light that the (MGK) could not achieve better results than the (TGK) for any type of matrices (H 1 & H 2), estimated by the two methods (NS-R, ROT). Despite this fact, the (MGK) and (TGK) were consistent in determining the climatic variables most affected by the rise in salt concentrations when adopting the (NS-R) method, which are (air temperature, minimum temperature, maximum temperature, and solar brightness). While when adopting the (ROT), the (MGK) determined other variables, while the traditional method identified the same variables mentioned above.

Solar Evolution Models with a Central Black Hole

Hawking proposed that the Sun may harbor a primordial black hole (BH) whose accretion supplies some of the solar luminosity. Such an object would have formed within the first 1 s after the Big Bang with the mass of a moon or an asteroid. These light BHs are a candidate solution to the dark matter problem, and could grow to become stellar-mass BHs if captured by stars. Here we compute the evolution of stars having such a BH at their center. We find that such objects can be surprisingly long-lived, with the lightest BHs having no influence over stellar evolution, while more massive ones consume the star over time to produce a range of observable consequences. Models of the Sun born about a BH whose mass has since grown to approximately 10−6 M ⊙ are compatible with current observations. In this scenario, the Sun would first dim to half its current luminosity over a span of 100 Myr as the accretion starts to generate enough energy to quench nuclear reactions. The Sun would then expand into a fully convective star, where it would shine luminously for potentially several gigayears with an enriched surface helium abundance, first as a sub-subgiant star, and later as a red straggler, before becoming a subsolar-mass BH. We also present results for a range of stellar masses and metallicities. The unique internal structures of stars harboring BHs may make it possible for asteroseismology to discover them, should they exist. We conclude with a list of open problems and predictions.

Using Partial Solar Eclipse for the 14-Metre Radio Telescope Calibration

Abstract A partial solar eclipse occurred on 25 October 2022, in the central and northern parts of Europe. The partial solar eclipse was observed at Aalto University Metsähovi Radio Observatory, Finland at the radio wavelength of 8 mm (37 GHz). In Finland, the magnitude of the partial solar eclipse was 62.7 %. Solar radio maps at the time cadence of about 9 minutes were observed over the whole eclipse. The solar eclipse observations could be used for instrument calibration purposes. This paper investigates the solar brightness temperature, the limb brightening effect, the height of the chromosphere and the location of radio brightening using the aforementioned partial solar eclipse observations. We got the confirmation that our earlier results are consistent, e.g., the solar brightness temperature matches with 8100 K ± 300 K. It was also possible to detect limb brightening effect. However, the prevailing solar activity might have distorted the final conclusions. The Moon should operate as a focusing element and the location of radio brightenings could be defined more carefully than in the normal conditions. We investigated this feature. Our results are in some parts unexpected and need further investigations.

Mars' atmosphere, volatiles, and climate as the sun heats up over the next 6 billion years

As the solar luminosity continues to increase over the next 6 billion years, the Martian surface will heat up to above the melting temperature of water ice. Water ice currently in the polar caps and ground ice will melt, potentially repopulating crater lakes or a very small ocean, with the abundance possibly enhanced due to diffusion upward of water currently locked in the deep crust. CO2 adsorbed in the regolith and locked up in the south-polar ice cap will diffuse into the atmosphere, providing up to 50 mbar total pressure; this will further increase the temperature via greenhouse warming. There are two end-member scenarios for the climate under these conditions: (i) Surface water could drive an atmospheric water cycle somewhat analogous to present-day Earth's, which would create a global clement climate conducive to the existence of widespread surface life. (ii) The widespread presence of liquid water could cause CO2 to form carbonate minerals and H2O to hydrate surface/subsurface minerals (or allow H released from water to escape to space), and CO2 and H2O could be lost to space, leaving Mars with a dry environment. The climate could end up between these end-members and also could vary with time. This uncertain climate end state informs our view that exoplanet evolution and habitability can be driven by endogenous processes associated with a terrestrial planet as well as by the ability of EUV and a stellar wind from the host star to strip away atmosphere.

Physical, Sensorial, and Physicochemical Characteristics of Arabica Coffee Dried under Two Solar Brightness Conditions

The solar drying process is a critical postharvest stage for preserving coffee quality and is widely used in coffee-producing countries. A descriptive exploratory study was carried out in zones with different annual solar brightness to determine the climate variability influence on solar drying. Variables related to the evolution of drying, physical and sensory quality, and the physicochemical characteristics of the Castillo® coffee variety were analyzed. Coffee quality was assessed by means of SCA protocol. An automatic system was designed to record variables inside the dryers and mass loss. The drying rates were different by climatic zone above and below 0.52%∙h−1. Drying time was significantly longer in less solar brightness zones (Wilcoxon test). An inverse linear relationship between rewetting percentage and bean moisture was observed. Regarding coffee quality, the average scores were 81.37 and 80.93 SCA points for the climatic zones with the lowest and highest solar brightness, respectively. The bean color, water activity, acidity, and fat content did not vary between climatic zones. The coffee quality was not affected by solar drying in contrasting climatic conditions, despite the differences in drying time. Solar drying behaviors were identified that allow for the development of strategies for improving the process efficiency and management of coffee.

The Calibration of the 35–40 GHz Solar Radio Spectrometer with the New Moon and a Noise Source

Calibrating solar radio flux has always been a concern in the solar community. Previously, fluxes were calibrated by matching load or the new Moon for relative calibration, and at times with the assistance of other stations’ data. Moreover, the frequency coverage seldom exceeded 26 GHz. This paper reports the upgraded and calibrated Chashan Broadband Solar millimeter spectrometer (CBS) working from 35 to 40 GHz at the Chashan Solar Observatory (CSO). Initially, the calibration of the solar radiation brightness temperature is accomplished using the new Moon as the definitive source. Subsequently, the 35–40 GHz standard flux is achieved by establishing the correlation between the solar radio flux, brightness temperature, and frequency. Finally, the calibration of the solar radio flux is implemented by utilizing a constant temperature-controlled noise source as a reference. The calibration in 2023 February and March reveals that the solar brightness temperature is 11,636 K at 37.25 GHz with a standard deviation (STD) of 652 K. The solar radio flux’s intensity is ∼3000–4000 solar flux units (SFU) in the range of 35–40 GHz with a consistency bias of ±5.3%. The system sensitivity is about ∼5–8 SFU by a rough evaluation, a noise factor of about 200 K, and the coefficient of variation of the system transmission slope of 6.5% @ 12 hr at 37.25 GHz. It is expected that the upgraded CBS will capture more activity during the upcoming solar cycle.

A brief overview of solar cycle variability effects on climate

Among interesting areas of scientific research is the study of the relationship between solar cycle variability and climate change. For centuries now, speculations on the influence of variations in the sunlight intensity on climate have been on going. It is without exaggeration to state that generally the earth has gotten warmer over the past centuries. Over the years, studies have shown that there is a very strong correlation between earth’s surface temperature and sunlight intensity variability. Some scholars argue that the main effect on the weather is not a change in the luminosity of the Sun during the period of maximum activity, but an increase in the flow of charged particles (solar wind). These act on the Earth’s magnetosphere and ionosphere. This action plays a role of the trigger that starts the processes, the energy of which is contained in the Earth’s atmosphere. The periodicity of these processes (hurricanes, floods, epidemics) often correlates with the period of solar activity. Nevertheless, it is quite possible that there may be the processes with a much longer period (hundreds and thousands of years). Some researchers suggest, that the observed increase in the Earth’s temperature is part of this long-term process. Thus, this piece of work compares these two views in an attempt to check the effects of solar cycle variability on climate.