Solar Phase Research Articles

Radial evolution of interplanetary coronal mass ejection-associated particle acceleration observed by Solar Orbiter and ACE

On 2022 March 10 a coronal mass ejection erupted from the Sun, resulting in Solar Orbiter observations at 0.45 au of both dispersive solar energetic particles arriving prior to the interplanetary coronal mass ejection (ICME) and locally accelerated particles near the ICME-associated shock structure as it passed the spacecraft on 2022 March 11. This interplanetary shock was later detected on 2022 March 14 by the Advanced Composition Explorer (ACE), which was radially aligned with Solar Orbiter, at 1 au. Ion composition data from both spacecraft — via the Solar Orbiter Energetic Particle Detector/ Suprathermal Ion Spectrograph (EPD/SIS) and the Ultra Low Energy Isotope Spectrometer (ULEIS) on ACE — allowed for an in-depth analysis of the radial evolution of species-dependent ICME-driven shock-associated acceleration processes for this event. We present a study of the ion spectra observed at 0.45 and 1 au during both the gradual solar energetic particle and energetic storm particle phases of the event. The shapes of the spectra seen at each spacecraft differ significantly, likely due to the varying shock geometry: Solar Orbiter spectra tend to lack spectral breaks, and the higher-energy portions of the ACE spectra have a comparable average flux to the Solar Orbiter spectra. Through an analysis of rigidity effects on the spectral breaks observed by ACE, we conclude that the 1 au observations were largely influenced by a suprathermal pool of $ He $ ions that were enhanced due to propagation along a stream interaction region that was interacting with the ICME at the times of observation.

Energy and exergy analysis and performance optimization of buildings integrated with transpired solar collectors and phase change materials

Transpired solar collectors (TSCs) are one of the cost-effective air heating technologies that can be easily installed on building facades to provide heated fresh air to condition indoor space. The economics of TSCs can be further enhanced by integrating with phase change materials (PCMs). This study presents the performance investigation and optimization of a building-integrated TSC and PCM system (TSC-PCM). The interactions between PCM thermal properties, their locations in the building envelope, and TSC design parameters were investigated. Based on the modeling of the TSC-PCM by using energy balance and enhanced enthalpy method, a series of orthogonal tests, which varied PCM type, thickness, and location within building envelopes, and TSC suction flow rate were conducted. Multivariate testing, through the Taguchi method, was then applied to identify the optimal design combination. The results showed that the suction flow rate of the TSC-PCM on the external wall showed the highest influence on enhancing indoor thermal performance (up to 77.6%), followed by PCM location on the external wall (up to 9.2%). The optimized TSC-PCM system improved the thermal comfort increase index (TCI) to 3.7 and achieved a maximum thermal efficiency of 401.8%, with an exergy improvement of 26.9% in comparison with the use of the TSC-only. The optimized TSC-PCM system increased the average indoor room temperature to 18.8 oC, which was 6.8% and 18.2% higher than the use of the TSC-only and a baseline without using PCM and TSC, respectively.

A magnetohydrodynamic mechanism for the formation of solar polar vortices

Polar vortices are ubiquitous features of planetary atmospheric flows, from the Earth-like rocky planets to Jupiter- and Saturn-like gas giant planets. Very little is known about their existence or dynamics on the Sun. What should be expected near the Sun's pole for the upcoming solar multi-viewpoint and polar missions? Here, we report the magnetohydrodynamic (MHD) nonlinear simulations for the formation and evolution of solar polar vortices using a near-surface MHD shallow-water model. Our findings indicate that the rush to the poles, the migration of magnetic fields toward the pole following the Sun's magnetic cycle, can positively contribute to the formation of polar vortices. The mechanism proposed here for the formation of polar vortices involves the role of magnetic fields and may be relevant to any star with a magnetic cycle. The Sun's polar vortices resulting from this mechanism are predominantly MHD, consisting of a tight pair of cyclonic and anticyclonic swirls. This mechanism is likely to operate during all solar cycle phases except the peak, when the polar field reverses. Polar vortices can impact dynamical evolution of global flows and polar fields, which seed the next activity cycle, hence better knowledge of physics of polar regions may lead to improved solar cycle and space weather forecasts.

Exploring Cool Pavement Technologies: A Lab-Based Experimental Analysis of Temperature and Reflectivity

Urban heat islands (UHI) have become an increasingly pressing issue owing to the global warming trend and a steady growth of urban areas. Revegetation, shading, or the reduction of sealed surfaces is not always possible in cities. Therefore, one way to fight UHIs is through adapting currently used pavements. This study assesses the thermal behavior of 12 different pavement materials in a custom-made test stand. The materials include mastic asphalt ( MA 8, MA 8 white), porous asphalt ( PA 4, PA 4 abraded, PA 4 white, PA 8, PA 8 abraded, PA 8 white), asphalt concrete ( AC 11 transparent, AC 8 yellow), and semi-flexible pavements ( SFP 8, SFP 8 zeolite). The albedo was assessed using pyranometer. Sensors and thermal imaging were used to measure temperatures during two simulated heat cycles. Both the temperatures underneath the test specimens and at the surface were considered, as well as the cooling times of the materials. The results showed high maximum temperatures for PA and MA, as well as low maxima for the white painted materials, with differences in maxima of up to 15°C. Porous asphalt, like PA 8, cools faster than MA 8 from roughly 47°C to 28°C, taking 3.7 h compared with MA 8’s 5.1 h. This highlights the importance of considering cooling times and regional solar phases in experimental setups. Through the wide range of tested materials, a significant linear correlation between the measured albedo and surface temperature was proven. Ultimately, a foundation for thermal comparability between these materials was established.

Comparative study on a solar-assisted ground source heat pump with CPC solar collector and phase change heat storage

To address the challenges of low solar energy utilization, soil temperature imbalance, and excessive energy consumption in traditional heating systems, a novel solar-assisted ground source heat pump (SAGSHP) with phase change heat storage is proposed. It integrates a compound parabolic concentrator (CPC) solar collector and a buried pipe heat exchanger for combined heating, using RT52, Na₂S₂O₃·5H₂O, and paraffin as phase change materials (PCM) to store excess heat. A TRNSYS model is developed to analyze its performance under different CPC concentration ratios and PCM configurations. Results show that the CPC collector can save approximately 33% collection area compared to evacuated tube and flat plate collectors, with heat collection efficiencies of 75.5% and 65.1% at 2 times and 5 times of the concentration ratios, respectively. The SAGSHP reduces annual energy consumption by about 2000 kWh and improves the average soil temperature stability. The heating time corresponding to RT52, Na2S2O3·5H2O, and Paraffin is 123.75 h, 80.75 h and 75 h, respectively. The average coefficient of performance of SAGSHP with RT52 reaches 3.096, and the energy consumption is reduced by about 24.3% after ten-year operation. Results confirms the SAGSHP’s potential to enhance heating efficiency, optimize solar energy use, and save energy in long-term operation.

Solar cycle phase and occurrence of intense geomagnetic storms

Solar cycles have an asymmetrical shape with a fast rise and a slow decline, which varies from cycle to cycle. This makes it difficult to study the solar cycle phase dependence of the occurrence of intense solar-terrestrial events such as intense geomagnetic storms. In the previous works, differences in the rise and fall time lengths of each solar cycle were not fully considered. We normalized the asymmetric shape of each solar cycle using the rise and fall time lengths and showed the solar cycle phase dependence of occurrence of the intense geomagnetic storms selected using the Dst index for solar cycles 19−24 and using the aa index for solar cycles 12−24. The previous works noted that the occurrence of geomagnetic disturbances shows double peaks before and after solar maximum. Our results showed that the occurrence of the intense geomagnetic storms selected using the Dst and aa indices does not always show clear double peaks and increased more in the earlier half of the fall time than in the other time periods. The Dst and aa indices have been used to select geomagnetic storms in the previous studies. We pointed out that the solar cycle phase dependence of occurrence of the geomagnetic storms selected using the aa index is slightly different from those selected using the Dst index. We showed the geomagnetic storm on 4 August 1972 as an extreme case, which showed difference between Dst and aa. We also showed that intense geomagnetic storms associated with eruptive flares from the active sunspot groups occurred around the solar minima of cycles 17, 19, 20, and 21.Graphical

A correlation between sunspot observations and solar Ca ii H&K activity proxies

ABSTRACT The magnetic phenomena on the solar surface have been the subject of several investigations over the last 400 yr. An early indicator of solar magnetic activity was sunspot counting. Currently, the main sunspot indicators are the international sunspot number, the sunspot group number, the total sunspot area, and the photometric sunspot index. Several improvements in observational techniques have allowed magnetic activity to be measured using solar/stellar spectra. Standard spectroscopic activity indicators are the $S_{\rm MW}$ index, based on the Ca ii H&K emission lines, and the chromospheric component $R^{\prime }_{\rm HK}$ index. In this context, we present a correlation between sunspot observations and solar Ca ii H&K activity proxies. We present our comparisons between the spectroscopic chromospheric activity proxies ($S_{\rm MW}$ and $R^{\prime }_{\rm HK}$) and the sunspot indicators over the last decades, using solar measurements (spectroscopic and spot proxy) performed on the same day. In general, our results indicate a linear fit between the chromospheric proxies and sunspot indicators. In addition, using the long-term sunspot group number records, we estimate an average spectroscopic proxy along the solar Maunder minimum (MM) phase, corresponding to $\mathinner {\langle {S_{\rm MW}}\rangle } = 0.167 \pm 0.013$ and $\mathinner {\log \langle {R^{\prime }_{\rm HK}}\rangle } = -4.913 \pm 0.363$. The estimated variability is $\sigma _{S_{\rm MW}} = 1.137 \times 10^{-7}$ and $\sigma _{\log R^{\prime }_{\rm HK}} = 2.704 \times 10^{-6}$. Our linear regression analysis, applied annually, suggests that the variability level of the chromospheric activity in the MM phase is significantly lower than in the normal period of activity and that this could be the result of linear regression on annually averaged data, combined with minimal sunspot activity during the solar MM phase. Further observations of MM analogues will be needed to test this hypothesis.

Simulation and experimental study on the performance of vacuum tube phase change collector with combined heat exchange of flat tubes and fins

This paper establishes a solar vacuum tube collector with flat tubes and fins as the heat transfer unit, and the thermal performance was tested under different environmental conditions. The results indicate that the paraffin in the vacuum tube collector showed the phenomenon of temperature stratification at the region of the high and low temperature when the system absorbed heat. Secondly, the daily average heat-taking efficiency can reach 30–45 % when the irradiance is 822.5 W/m2, 555.0 W/m2, and it only about 6 % under the irradiance 111.6 W/m2. In addition, the energy storage system was simulated, and the thermal storage stage was analyzed according to the different temperature distribution curves, temperature distribution nephogram and liquid fraction. The results show that when the running time is about 2500 s, the paraffin temperature reached the melting point, the paraffin begins to melt; when to 4500 s, the solid–liquid phase conversion is complete, after this time the temperature rise is relatively smooth; when the time is run to 14,000 s, energy-storage type solar vacuum collector has reached a stable state, the temperature tends to level off, then the temperature increase is not obvious. It will provide some theoretical and data support for the later combination of solar phase change energy storage technology and heat pump technology.

Scaling Law of Flow and Heat Transfer Characteristics in Turbulent Radiative Rayleigh-Bénard Convection of Optically Thick Media

Radiative natural convection is of vital importance in the process of energy storage, power generation, and thermal storage technology. As the attenuation coefficients of many heat transfer media in these fields are high enough to be considered as optically thick media, like nanofluids or molten salts in concentrated solar power or phase change thermal storage, Rosseland approximation is commonly used. In this paper, we delve into the impact of thermal radiation on the Rayleigh-Bénard (RB) convection. Theoretical analysis has been conducted by modifying the Grossmann-Lohse (GL) model. Based on turbulent dissipation theory, the corresponding scaling laws in four main regimes are proposed. Direct numerical simulation (DNS) was also performed, revealing that radiation exerts a notable influence on both flow and heat transfer, particularly on the formation of large-scale circulation. By comparing with DNS results, it is found that due to the presence of radiation, the modified Nu scaling law in small Pr range of the GL model is more suitable for predicting the transport characteristics of optical thick media with large Pr. The maximum deviation between the results of DNS and prediction model is about 10%, suggesting the summarized scaling law can effectively predict the Nu of radiative RB convection.

Lifetime of Long-Lived Sunspot Groups

Studies of active region (AR) lifetimes are mostly restricted to short-lived ARs. The aim of this paper is to include recurrent ARs, which should be identified unambiguously. The first step is the algorithmic listing of possible returns; then, the candidates are visually checked using the unique HTML-feature of the Debrecen sunspot database. The final step is application of an asymmetric Gaussian function, introduced in previous articles, for short-lived ARs. This function has a surprisingly good fit to the data on correctly identified recurrent sunspot groups over several rotations enabling the reconstruction of the development on the far side of the sun. The Gnevyshev–Waldmeier rule for the area–lifetime relationship is not applicable for recurrent ARs; however, as a novel approach, a linear regression analysis extended to long lifetimes made it possible to recognize two populations of sizes for which two different area–lifetime relationships can be obtained. The lifetimes exhibit weak dependencies on the heliographic latitude and solar cycle phase. If an asymmetric Gaussian cannot be fit to the data, then they presumably belong to consecutive members of an active nest.

Enhancing water heater efficiency with aluminum and zinc-coated steel systems for energy solutions

Solar collector plates are integral components for efficient solar heat transfer. While various metallic materials can serve as collector plates, aluminum stands out as a commonly employed choice with thermal conductivity comparable to copper and zinc. The material's thermal conductivity significantly impacts the heat transfer efficiency from sunlight to the collector. Moreover, the surface configuration of the plate is a crucial factor affecting solar heat absorption. This study investigates the utilization of corrugated collector plates made from two materials, aluminum and zinc-coated steel. The solar collector testing phase covers the dry and rainy seasons in Indonesia, thereby providing a comprehensive evaluation in various weather conditions. There are two stages of solar collector testing, namely testing before it is used to heat water and testing to heat water. Radiation data show seasonal variations, with higher radiation observed in the dry season. Evaluation of the performance of the solar collector before being used to heat water resulted in an average efficiency of 41.45 % for aluminum and 33.94 % for zinc-coated steel. Meanwhile, evaluation of the performance of solar collectors used to heat water produces an average efficiency of 20.40 % for aluminum and 10.47 % for zinc-coated steel. Corrugated aluminum solar collectors exhibited promising absorber potential, while zinc-coated steel demonstrated economic viability due to its lower cost compared to aluminum. The research underscores the potential applicability of solar collectors made from both materials throughout different seasons.

Para-Aminoazobenzenes-Bipolar Redox-Active Molecules.

Azobenzenes (ABs) are versatile compounds featured in numerous applications for energy storage systems, such as solar thermal storages or phase change materials. Additionally, the reversible one-electron reduction of these diazenes to the nitrogen-based radical anion has been used in battery applications. Although the oxidation of ABs is normally irreversible, 4,4'-diamino substitution allows a reversible 2e- oxidation, which is attributed to the formation of a stable bis-quinoidal structure. Herein, we present a system that shows a bipolar redox behaviour. In this way, ABs can serve not only as anolytes, but also as catholytes. The resulting redox potentials can be tailored by suitable amine- and ring-substitution. For the first time, the solid-state structure of the oxidized form could be characterized by X-ray diffraction.

Para‐Aminoazobenzole – Bipolare Redoxaktive Verbindungen

AbstractAzobenzole (AB) sind vielseitige Verbindungen mit zahlreichen Anwendungsgebieten. Eines dieser Gebiete ist die Energiespeicherung, wie zum Beispiel molekulare organischen Solarthermie (MOST) Speicher, oder Phasenwechselmaterial. Batterien sind eine weitere Applikation von AB als elektrochemische Energiespeicher, die auf der reversiblen 1e− Reduktion zu Radikalanion beruhen. Oxidationen von AB sind üblicherweise irreversibel, können jedoch durch eine 4,4‘‐Diaminosubstitution reversibel werden. Diese Reversibilität ist auf die Bildung eine stabile Chinonstruktur zurückzuführen. Hier präsentieren wir ein System, das bipolares Redoxverhalten von AB zeigt. Dadurch können AB nicht nur als Anolyte, sondern auch als Katholyte eingesetzt werden. Die erhaltenden Redoxpotentiale können durch geeignete Amin‐ oder Ringsubstitutionen angepasst werden. Des Weiteren wurde die Festkörperstruktur der oxidierten Chinonform zum ersten Mal mittels Röntgenbeugung charakterisiert.

A holistic methodology for designing novel flat plate evacuated solar thermal collectors: Modelling and experimental assessment

This paper presents a comprehensive analysis of the design, implementation, experimentation, and optimization of a novel evacuated flat-plate solar thermal collector characterized by a vacuum level between the glass cover and the absorber plate. The paper addresses different research themes, primarily focusing on developing a low-cost evacuated solar thermal collector with a high innovation level. Additionally, it introduces a comprehensive approach for the conceptualization, design, fabrication, testing, and optimization of solar thermal collectors. Specifically, this study aims to highlight the characteristics of a vacuum-enhanced solar thermal collector and demonstrate a step-by-step process involved in its design, fabrication, testing, and optimization. The proposed methodology is based on the adoption of two software tools and an extensive experimental analysis: the commercial software ANSYS is utilized for structural analysis, while MatLab is employed to develop a suitable mathematical tool for assessing the energy performance of the system and optimizing it. The outcomes show the reliability of the methodology and the performance of the low-cost evacuated solar thermal collector under different vacuum levels, providing insights into energy, economic, and environmental aspects. This work innovates by presenting a thorough analysis covering all solar thermal collector production phases, from conceptualization to optimization. The conclusions highlight the production of a reliable approach, and proof-of-concept results demonstrate how increasing the vacuum level enhances the thermal efficiency of a solar collector.

Quantifying Extreme Values in Geomagnetic Perturbations Using Ground Magnetic Records

AbstractWe comprehensively analyzed geomagnetic perturbations using ground magnetic records from over 400 stations spanning four solar cycles, from 1976 to 2023. We assess the perturbations in the three magnetic components separately. Our study covers low, middle, and high magnetic latitudes in the northern magnetic hemisphere, with the primary objective of quantifying extreme values and evaluating their variability on magnetic latitude, local time, and solar cycle phases “minimum, ascending, maximum, and declining.” Our findings reveal spatial patterns to be less discernible as perturbations intensify, with distinct responses at middle and high latitudes. The extreme values, defined as percentiles 0 and 100, were observed to be localized and randomly distributed in local time, especially in the east magnetic component. Additionally, we observed dusk‐dawn asymmetries in the magnitude of perturbations related to the auroral electrojets, indicating complex interactions between the magnetosphere and ionosphere. Furthermore, the results reveal a preference for the most significant extreme values to occur in the declining phase of the solar cycle. These insights deepen our understanding of geomagnetic perturbations and their variability, contributing to space weather forecasting and mitigation strategies.

Combined spin orientation and phase function of asteroids

Context. Large sky surveys provide numerous non-targeted observations of small bodies of the Solar System. The upcoming LSST of the Vera C. Rubin Observatory will be the largest source of small body photometry in the next decade. With non-coordinated epochs of observation, colors – and therefore taxonomy and composition – can only be computed by comparing absolute magnitudes obtained in each filter by solving the phase function (evolution of brightness of the small body against the solar phase angle). Current models in use in the community (HG, HG12*, and HG1G2), however, fail to reproduce the long-term photometry of many targets due to the change in the aspect angle between apparitions. Aims. We aim to derive a generic yet simple phase function model accounting for the variable geometry of the small bodies over multiple apparitions. Methods. As a spinoff of the HG1 G2 model, we propose the sHG1G2 phase function model in which we introduce a term describing the brightness changes due to spin orientation and polar oblateness. We applied this new model to 13 245 908 observations of 122 675 Solar System objects (SSOs). These observations were acquired in the g and r filters with the Zwicky Transient Facility between November 1, 2019 and December 1, 2023. We retrieved them and implemented the new sHG1G2 model in FINK, a broker of alerts designed for the LSST. Results. The sHG1G2 model leads to smaller residuals than other phase function models, providing a better description of the photometry of asteroids. We determined the absolute magnitude, H, and phase function coefficients (G1, G2) in each filter, the spin orientation (α0, δ0), and the polar-to-equatorial oblateness, R, for 95 593 SSOs, which constitutes about a tenfold increase in the number of characterized objects compared to the current census. Conclusions. The application of the sHG1 G2 model to ZTF alert data using the FINK broker shows that the model is appropriate for extracting physical properties of asteroids from multi-band and sparse photometry, such as the forthcoming LSST survey.

Height profile variations of ionospheric conductivity: A case study in Addis Ababa, Ethiopia

Ionospheric conductivity is the ability to conduct ionospheric current and is impacted by a variety of current system flows in height profiles, which increase ionosphere conductivity. In this study, we have analyzed the height profiles of the ionospheric conductivity daily and monthly variations in Addis Ababa, Ethiopia, during a very low solar activity phase in the year 2020. The daily height profile variations of ionospheric conductivity in Addis Ababa with geographic latitude 9o N and longitude 39o E are estimated at midnight (00:00 UT), morning (09:00 UT), mid-day (12:00 UT), and early nighttime (18:00 UT). The monthly variations of ionospheric conductivity (parallel, Pedersen, and Hall conductivity) are also presented for all months, with the highest ionospheric variability occurring after noon (14.00 UT). At midnight (00:00 UT) and early nighttime (18:00 UT), the ionospheric conductivity shows more fluctuation than in the morning (09:00 UT) and midday (12:00 UT) in diurnal variation. The monthly variations of ionospheric conductivity (parallel, Pedersen, and Hall conductivity) in the daytime at 14:00 UT increase steeply to reach their peak values and keep the sharpness of their variability.

Effects of local time on the variations of the total electron contents at an American and Asian longitudes and their comparison with IRI-2016, IRI-Plas2017 and NeQuick-2 models during solar cycle 24

Ionospheric modelling is one of the major tools to study the behavior of the ionosphere. Ionospheric models have been useful in predicting the true state of the ionosphere particularly in regions where Global Positioning System (GPS) are not readily available. This research paper aims to study the longitudinal variations and the effects of local time on the total electron content (TEC) recorded in two different sectors (Asia and America) during the ascending, maximum and descending phases of solar cycle 24 (2011–2017) and also to compare its values to IRI-2016, IRI-Plas2017 and NeQuick-2 models in order to evaluate their performances. An hourly interval profile computed on seasonal basis were used to study the behaviors of TEC diurnally and seasonally. A monthly interval error profile plotted on annual basis was also used to investigate the deviations of the models from the GPS values. Our results showed that the peak values of TEC in the Asian and American sectors were recorded around the dawn,06:00UT (13:00LT) and dusk, 18:00UT (15:00LT) respectively. We also affirmed from our results that seasonal/winter anomalies were recorded in all the phases of the solar cycle in both sectors. Equinoctial Asymmetry was also observed to be predominant during different phases of the solar cycle in both sectors except during ascending and descending phases in the Asian and American sectors respectively. Out of the 168 months of data collated for this study, only 162 months of data were available. The IRI-2016, IRI-Plas2017 and NeQuick-2 models have 11.7%, 23.5% and 64.8% better performance in all the months under consideration. Therefore, the NeQuick-2 model had the best performance in both the Asian and American sectors. Finally, from the results of our statistical analysis, Mean Absolute Error (MAE) has ∼3 TECU lower than the Root Mean Square Error (RMSE) values in both sectors and in all the solar cycle phase. Hence, MAE can evaluate the performance of ionospheric models better than RMSE.

Multicolour photometry of LEO mega-constellations Starlink and OneWeb

ABSTRACT The development of low earth orbit (LEO) mega-constellation fundamentally threatens ground-based optical astronomical observations. To study the photometric properties of the LEO mega-constellations, we used the Xinglong 50 cm telescope to conduct a large-sample, high-precision, and multicolour target-tracking photometry of two typical LEO mega-constellations: Starlink and OneWeb. Over a three-month observation period starting on 2022 January 1, we collected 1447 light curves of 404 satellites in four typical versions: Starlink v1.0, DarkSat, VisorSat, Starlink v1.5, and OneWeb. According to data statistics, Starlink v1.0 has the smallest median magnitude at clear and Sloan Digital Sky Survey gri band, and OneWeb is the dimmest bus. The brightness of Starlink v1.5 is slightly brighter than VisorSat. We construct a detailed photometric model with solar phase angle variations by calculating the illumination-visibility geometry based on the orbital parameters. Our data analysis shows that the solar phase angle is the significant characteristic which influencing Starlink satellites’ brightness, but it is not sensitive to OneWeb satellites. VisorSat and Starlink v1.5 versions, which are equipped with deployable visors, have significantly reduced scattered light compared to the previous Starlink v1.0 version. The multiband LOWESS and colour index are analysed in characterizing the energy and colour features of LEO mega-constellation satellites. This work found that the proportion of scattered sunlight mitigation achieved with VisorSat and Starlink v1.5 was 55.1 and 40.4 per cent, respectively. The colour index of different buses shows an evident clustering feature. Our observation and analysis could provide valuable quantitative data and photometric models, which can contribute to assessing the impact of LEO mega-constellations on astronomical observations.

Exploring ionospheric dynamics: a comprehensive analysis of GNSS TEC estimations during the solar phases using linear function model

Abstract The modeling and forecasting of Total Electron Content (TEC) play a major role in influencing signals from satellite-based navigation systems and impact the performance of diverse satellite-dependent technologies. The intensity of solar ionizing radiation and the state of geomagnetic field activity influence the Global Navigation Satellite System (GNSS)-TEC. This paper uses a Linear TEC Function (LTF) climatology model to understand ionospheric behavior under solar and geomagnetic activities that cause variations in the electron distribution of the ionosphere medium. The LTF model integrates representations of solar EUV photon (MgII) and geomagnetic (SYMH) activities, incorporating solar-modulated oscillations (periodic variations) at four seasonal cycles and a linear trend. The LTF model examined the time series of GPS-TEC at a location (geographic 34.95° N, 134.05° E) with a time resolution of 1 h, from 1997 to 2016, covering solar cycles 23 and 24. The Root Mean Square Deviation (RMSD) and correlation coefficient between the GNSS-TEC and model TEC (LTF) was 5.30 TECU and 95 %. The results indicate that solar components, as well as annual and semi-annual variations, have a significant impact on the daily average TEC. Solar activity appears to be the predominant determining factor of TEC during the solar phases of cycles 23 and 24. In contrast, periodic influences primarily outline TEC during periods characterized by minimal solar activity. The geomagnetic component presents an increased influence, particularly during storm periods. The model demonstrates superior performance in Total TEC modeling compared to other state-of-the-art approaches.