Eclipse Effects Research Articles

Effects of the annular eclipse on the surface O3 in yunnan province, China

The impact of the annual solar eclipse, starting on 21st June 2020, attributable to surface ozone concentration (O3) has been investigated in this study. To estimate the influence of the solar eclipse on O3 better, the variations of one reaction precursor of ozone production [nitrogen dioxide (NO2)], coupled with the meteorological factors (including Total Solar Irradiance (TSI), Temperature (T), and Relative Humidity (RH)), were analyzed in Yunnan Province, China. The results show observed O3 decreases from the beginning of the eclipse, reaching its minimum value when the eclipse left Yunnan province. During the period of the solar eclipse, the O3 decrease lasted for 20 h with a reduction of more than 40%. The reduction of TSI lasted for 5 h with a maximum at -90%. Simultaneously, the temperature decreased but the relative humidity increased during the reduction in solar radiation. O3 exhibits a significantly positive correlation with temperature and a negative correlation with relative humidity. However, NO2 did not show a clear response with changes lasting for 4 h. O3 and NO2 show a negative correlation. The influence of CO on O3 is minor except for Kunming. Thus, O3 in seriously polluted cities is more sensitive to NO2 and CO during the eclipse, such as in Kunming.

Effects of Total Solar Eclipse on Ionospheric Total Electron Content over Antarctica on 2021 December 4

The effects of a total solar eclipse that occurred on 2021 December 4 on ionospheric total electron content (TEC) over Antarctic stations were studied. The study was based on GPS data obtained over Antarctica on the day of the eclipse and the days before and after the eclipse over six GPS stations. The findings of this study show that a total solar eclipse lowers the amount of ionization reaching the Earth’s surface with TEC values dropping across the stations. Finally, the enhancement of ΔTEC is quite different from one station to another station. This may also be due to the effect of solar heating conditions and the density of the Sun as exerted over the stations with the Sun side over one station and the clouded part over the others.

Locally optimal control laws for Earth-bound solar sailing with atmospheric drag

Solar sailing is a spacecraft propulsion method relying solely on solar radiation pressure to provide thrust and is therefore propellantless by nature. Although it represents a practical and promising propulsion system particularly suited for heliocentric flight regimes, the majority of sailcraft missions flown to date have remained Earth-bound and more Earth-bound missions are scheduled for the near future. However, the fundamental dynamics and trajectory optimization of a solar sail around the Earth have only been investigated to a limited extent, often neglecting the effect of non-negligible perturbations in the dynamics and the optimal control problem. Among these perturbations are the effect of eclipses, non-spherical gravity, and aerodynamic drag. Their magnitude can be comparable to, or even exceed that of solar radiation pressure and their effect on the solar-sail dynamics should be investigated to ensure the sailcraft's transfer capabilities and controllability. This article does so by including these perturbations in the dynamics and by considering aerodynamic drag in the optimal control problem. Using this formulation, it is shown that the optimal control problem is independent of the solar-sail loading parameter and that, by solving it, locally optimal steering laws can be derived to effectively change individual orbital elements. These newly derived steering laws form an extension to the laws found by McInnes for unperturbed solar-sail Earth-bound motion. By accounting for the perturbations in the derivation of the steering laws, it is possible to characterize how the perturbations affect the solar-sail maneuvering capabilities. This is quantified based on the established increase of the targeted orbital element. Furthermore, a range of different starting orbits will be considered to analyze the effects of perturbations in different orbital regimes. As demonstration of the real need for this investigation, NASA's Advanced Composite Solar Sail System (ACS3) mission will be considered as real-case scenario. This mission is scheduled for launch in mid-2022 and may benefit from the steering laws derived in this article to prove the maneuverability of solar sails in Earth orbit.

Regression-based gap-filling methods show air temperature reductions and wind pattern changes during the 2019 total eclipse in Chile

Singular disruptive events like solar eclipses affect the measured values of meteorological variables at the earth’s surface. To quantify such an impact, it is necessary to estimate what value the parameter would have taken had the event not occurred. We design and compare several methods to perform such an estimate based on longer observational timeseries from individual meteorological surface stations. Our methods are based on regularised regressions (including a Bayesian variant) and provide both a point an associated error estimate of the disruptive event’s impact. With their help, we study the effect of the total solar eclipse of July 2nd, 2019, in the Coquimbo Region of Chile, on near-surface air temperatures and winds. The observational data used have been collected by the meteorological surface station network of the Centro de Estudios Avanzados en Zonas Áridas (CEAZA). Most stations inside the eclipse’s umbra registered a temperature drop of 1–2 ^{circ }C, while the most extreme estimated temperature drop surpassed 6 ^{circ }C. The presence of an ‘eclipse cyclone’ can neither be proven nor refuted. Application of the regression methods to other comparable problems like volcanic eruptions, forest fires, or simply gap filling of observational data, are conceivable.

Meteorological effects and impacts of the 10 June 2021 solar eclipse over the British Isles, Iceland and Greenland

We present a pioneering report of the meteorological effects of a partial solar eclipse across a wide region. Using large networks of official weather stations and a regional climate model simulation, we detected meteorological effects of the 10 June 2021 eclipse in the UK, Iceland and Greenland. A meteorological model was used to show that the eclipse decreased the daily Greenland Ice Sheet surface melt by ~10%. Solar photovoltaic and wind renewable energy production across the UK were also affected.

Application of a dynamic thermoelastic coupled model for an aerospace aluminium composite panel

An analytical-numerical coupled model has been derived to predict the effects of dynamic thermo-mechanical loading on aluminium composite panels specifically in the form of metallic skin sandwich structures, for the purposes of enhanced design of spacecraft structures where the environmental conditions comprise combined mechanical and thermal loading. The mechanical loading can arise as a consequence of localised structural dynamics, and the thermal loading is attributable principally to the effects of solar irradiation and eclipse during a satellite’s orbit, and together they have the potential to influence de-point adversely, in particular. On this basis a combined physics model is required to deal with the generalised thermoelastic problem and this paper reports on the theoretical work done to achieve that. The research has considered the literature in detail and a refined model has been proposed for an aerospace application which results in an analytical-numerical solution for the thermoelastic problem in aluminium composite panels. The model is explored for a panel under a range of centrally located static mechanical loads, in conjunction with thermal loading provided in the form of various controlled and elevated environmental temperature functions, all for prescribed physical boundary conditions. Both forms of loading are shown to influence the displacement of the panel significantly, thereby confirming the importance of a combined physics model for analysing structures in this context.

Effect of total lunar eclipse of 27th July 2018 on the D-region ionosphere by using VLF observations

• Total Lunar Eclipse of 27 July 2018 is investigated for its impact on lower ionosphere. • Change in D-region electron density is inferred from VLF observations and modeling. • Nighttime lower ionospheric density during the Total Lunar Eclipse was found to decrease. In this report, an effort for the first time has been made to investigate the effect of the total Lunar Eclipse that occurred on 27th July 2018 (the longest lunar eclipse in the 21st century) on the D-region ionosphere. Very Low Frequency (VLF) navigational transmitter signals recorded at Prayagraj (formally Allahabad) station in India is the primary dataset used. The signals from two VLF transmitters: NWC (19.8 kHz) from Australia, and JJI (22.2 kHz) from Japan, have been utilized. When compared to unperturbed night, NWC signal amplitude showed an anomalous decrease of ∼0.86 dB, while JJI amplitude showed an anomalous increase ∼0.26 dB during the lunar eclipse. The Wait’s lower ionospheric parameters: reflection height ( H’ ) and sharpness factor ( β ) are estimated by using a rather coarse method of modeling of VLF signals anomalies on eclipse day, which comes out to be H’ = 85.25 km & β = 0.689 km −1 and H’ = 84.59 km & β = 0.683 km −1 respectively for NWC and JJI path. Using wait parameters, the electron density ( N e ) profile is estimated and this showed a decrease in N e during eclipse time with reference to the nighttime ambient values. The N e values for the NWC path, showed relatively higher decrease compared to the JJI path. The plausible reasons for observed N e decrease on lunar eclipse night could be due to the reflected lunar Lyman‐α and X-ray’s radiation which may contribute to the nighttime ionization is blocked during the lunar eclipse, thereby decreasing the nighttime lower ionospheric N e .

Geomagnetic effect of the solar eclipse on June 10, 2021

Geomagnetic effect of the solar eclipse on June 10, 2021

Eclipsed: Emergence-return activity of two pteropodid bat species during lunar eclipse

Lunar eclipses are known to influence flight activity of tropical bats at foraging sites. However, little is known about the onset and offset of flight activity from the roost during lunar eclipses compared to other full moon nights. Emergence from and return to the roost were observed during a total lunar eclipse at a colony of the fruit bat Rousettus leschenaultii and during a partial lunar eclipse at a Pteropus giganteus colony in southern India. In addition, on the same partial eclipse night, a single male P. giganteus was tracked using GPS telemetry. Flight activity in both species was compared between the eclipse night and other full moon nights. In both cases, bats emerged before the eclipse and fewer R. leschenaultii individuals returned to the roost during the hours of the total eclipse, compared to the corresponding hours during other full moon nights. No such difference in return activity was observed in the P. giganteus colony or in the GPS tracked individual between the partial eclipse and other nights. This is the first attempt to study temporal flight activity of bats during lunar eclipses at their roosting sites. More roosting site observations, especially on species that roost in the open, are required to understand the effects of lunar eclipses on bat activity.

Ionospheric and geomagnetic response to the total solar eclipse on 21 August 2017

Solar eclipses provide an excellent opportunity to study the effects of a sudden localized change in photoionization flux in the Earth's ionosphere and its consequent repercussion in the Geomagnetic field. We have focused on a subset of the data available from the North American 2017 eclipse in order to study VTEC measurements from GNSS data and geomagnetic field estimations from INTERMAGNET observatories near the eclipse path. Our simultaneous analysis of both datasets allowed us to quantify the ionosphere and magnetic field reaction to the eclipse event with which allowed us to compare how differently these take place in time. We found that studying the behaviour of VTEC differences with respect to reference values provides better insight of the actual eclipse effect and were able to characterize the dependence of parameters such as time delay of maximum depletion and recovery phase. We were also able to test models that link the ionospheric variations in a quantitative manner. Total electron content depletion measured from GNSS were fed into an approximation of Ashour-Chapman model at the locations of geomagnetic observatories and its predictions match the behaviour of magnetic field components in time and magnitude strikingly accurately.

ЕФЕКТИ СОНЯЧНОГО ЗАТЕМНЕННЯ 10 ЧЕРВНЯ 2021 р. В ІОНОСФЕРІ ВИСОКИХ ШИРОТ: РЕЗУЛЬТАТИ GPS-СПОСТЕРЕЖЕНЬ

Subject and Purpose. The unique natural phenomena which solar eclipses are can activate coupling between the subsystems of the Earth–atmosphere–ionosphere–magnetosphere system. Following an eclipse, disturbances may get induced in all the subsystems and their associated geophysical fields. It is important that a subsystem’s response does not depend on the phase of the eclipse alone, but also on the state of space weather and the observation site coordinates. The majority of solar eclipses occur at middle and low latitudes. The maximum phase of the June 10, 2021 annular eclipse was observed at high latitudes, including the North Pole. The highlatitude ionosphere is fundamentally different from the mid- and low-latitude ionosphere as it stays in a metastable state, such that any impact may be capable of activating subsystem coupling. The relevance of this study is conditioned by the diversity of the solar eclipse effects in the high-latitude ionosphere. The purpose of this work is to present observational results concerning variations in the total electron content (TEC) in the high-latitude ionosphere in the course of the June 10, 2021 solar eclipse. Methods and Methodology. An array of eleven terrestrial GPS receive stations and eight GPS satellites were used for the observations. Results. The effects from the solar eclipse were distinctly observable at all eleven reception sites and from all the eight satellites. On the average, i.e. with random fluctuations neglected, changes in illumination at ionospheric heights were followed by decreases in the TEC. All of the observation records demonstrated a decrease in the TEC at the early stage of the eclipse. Some 60 to 100 min later the TEC attained a minimum and then returned to virtually the initial value. The lowest observed magnitude of the TEC was 1.0–5.1 TEC units, while, on the average, it was found to be 2.7 ± 1.6 TEC units, or 35 ± 18%. The greatest decrease in the TEC lagged behind the maximum phase of the solar eclipse (lowest illumination at the heights of the ionosphere) by 5–30 min, or 15.7 ± 6.8 min on the average. A few TEC records obtained at different stations showed quasi-periodic variations with the periods ranging from 5 to 19 min and amplitudes of 1 to 12%. Conclusions. The annular eclipse of June 10, 2021 acted to significantly disturb the high-latitude ionosphere where aperiodic and quasi-periodic disturbances of the TEC took place.

Effects from the June 10, 2021 solar eclipse in the ionosphere over Kharkiv: results from ionosonde measurements

Background. Ionospheric effects from solar eclipses (SEs) have been studied for over a century. The studies intensified in the 1960–1970, when rockets, satellites, ionosonde networks, and incoherent scatter radars became actively involved in the investigations. The following basic features of SEs displayed in the ionosphere have been established: a decrease in the electron density and the electron, ion, and neutral temperatures, changes in the dynamics of the ionosphere, and the generation of acoustic and atmospheric gravity waves. The recurring regular features are observed together with the features pertaining to each individual SE. Therefore, the study of the effects of each new solar eclipse is an urgent task. The purpose of this paper is to present the results of analysis of the ionogram measurements acquired by the digisonde located at the Radiophysical Observatory, V. N. Karazin Kharkiv National University. Techniques and Methodology. The observations of the state of the ionosphere were made using the digisonde specifically developed by the V. N. Karazin Kharkiv National University and located at the V. N. Karazin Kharkiv National University Radiophysical Observatory (49°38' N, 36°20' E). The data processing included the following. First, the time series of critical F2-layer frequencies, foF2, of the minimum frequency, fmin, observed on an ionogram, and of the virtual height were plotted. Second, the trends and the differences between the initial series and the trends were calculated. Third, given the foF2(t) values, the electron densities N(t) and their increments ΔN(t) were calculated, and fourth, the systems spectral analysis of ΔN(t) dependences was conducted to determine the spectral content. Results. A maximum decrease of 3.7–3.8% in the F2 peak electron density has been detected. This value agrees very well with the calculated value of 3.5–3.8%. The time delay between the minimum in the electron density observed and the maximum value of the phase of the solar eclipse was determined to be 12.5 min, which is in good agreement with the calculated value of 12.8 min. The time delay suggests that the linear loss coefficient was 1.3´10–3 s–1 and the production rate was (3.8–3.9)×108 m–3∙s–1. The SE was associated with the generation of quasi-periodic oscillations in the electron density and the F2 layer virtual height, within the period range of 10–15 min, and with amplitudes of 1.7–4% and 9.1–11.4%, respectively. The fluctuations in the minimum frequency observed on the ionograms showed a factor of 3–4 times decrease in the course of the SE. In addition, a decrease in the averaged values was observed to occur from 3 to 2.85 MHz (by 5%), which suggested that the radio wave attenuation by absorption decreased due to a decrease in the lower-ionosphere electron density below 100 km altitude. This decrease was estimated to be about 2%, while the decrease determined from the observations gave 2.2%. Conclusions. The partial solar eclipse with a very small value of the maximum magnitude (0.112) and obscuration of 4.4% acted to produce a few effects observed in the ionosphere with the ionosonde.

Global Effects of a Polar Solar Eclipse on the Coupled Magnetosphere‐Ionosphere System

AbstractIt is well‐known that solar eclipses can significantly impact the ionosphere and thermosphere, but how an eclipse influences the magnetosphere‐ionosphere system is still unknown. Using a coupled magnetosphere‐ionosphere‐thermosphere model, we examined the impact on geospace of the northern polar‐region eclipse that occurred on June 10, 2021. The simulations reveal that the eclipse‐induced reduction in polar ionospheric conductivity causes large changes in field‐aligned current, cross‐polar cap potential and auroral activity. While such effects are expected in the northern hemisphere where solar obscuration occurred, they also occurred in the southern hemisphere through electrodynamic coupling. Eclipse‐induced changes in monoenergetic auroral precipitation differ significantly between the northern hemisphere and southern hemisphere while diffuse auroral precipitation is interhemispherically symmetric. This study demonstrates that the geospace response to a polar‐region solar eclipse is not limited just to the eclipse region but has global implications.

ОСОБЛИВОСТІ ІОНОСФЕРНИХ ЕФЕКТІВ ЧАСТКОВОГО СОНЯЧНОГО ЗАТЕМНЕННЯ НАД ХАРКОВОМ 10 ЧЕРВНЯ 2021 Р.

Purpose: Solar eclipses pertain to high-energy sources of disturbance in the subsystems of the Sun–interplanetary-medium–magnetosphere–ionosphere–atmosphere–Earth and the Earth–atmosphere–ionosphere–magnetosphere systems. During the solar eclipse, the coupling between the subsystems in these systems activates, and the parameters of the dynamic processes become disturbed. Investigation of these processes contributes to understanding of the structure and dynamics of the subsystems. The ionospheric response to the solar eclipse depends on the season, local time, magnitude of the solar eclipse, phase of the solar cycle, the observation site, the state of space weather, etc. Therefore, the study of the effects, which each new solar eclipse has on the ionosphere remains an urgent geophysics and radio physics problem. The purpose of this paper is to describe the radio wave characteristics and ionospheric parameters, which accompanied the partial solar eclipse of 10 June 2021 over the City of Kharkiv. Design/methodology/approach: To make observations, the means of the HF Doppler measurements at vertical and oblique incidence available at the V. N. Karazin Kharkiv National University Radiophysical Observatory were employed. The data obtained at the “Lviv” Magnetic Observatory were used for making intercomparison. Findings: The radiophysical observations have been made of the dynamic processes acting in the ionosphere during the solar eclipse of 10 June 2021 and on the reference days. The temporal variations in the Doppler frequency shift observed at vertical and oblique radio paths have been found to be, as a whole, similar. Generally speaking, the Doppler spectra over these radio propagation paths were different. Over the oblique radio paths, the number of rays was greater. The solar eclipse was accompanied by wave activity enhancement in the atmosphere and ionosphere. At least three wave trains were observed. The values of the periods (about 5–12 min) and the relative amplitudes of perturbations in the electron density (δN≈0.3–0.6 %) give evidence that the wave disturbances were caused by atmospheric gravity waves. The amplitude of the 6–8-min period geomagnetic variations has been estimated to be 0.5–1 nT. Approximately the same value has been recorded in the X component of the geomagnetic field at the nearest Magnetic Observatory. The aperiodic effect of the solar eclipse has appeared to be too small (less than 0.01 Hz) to be observed confidently. The smallness of the effect was predetermined by an insignificant magnitude of the partial eclipse over the City of Kharkiv (no more than 0.11). Conclusions: The features of the solar eclipse of 10 June 2021 include an insignificant magnitude of the aperiodic effect and an enhancement in wave activity in the atmosphere and ionosphere. Key words: solar eclipse; ionosphere; Doppler spectrum; Doppler frequency shift; electron density; geomagnetic field; atmospheric gravity wave

Overview of solar eclipse of 21st June 2020 and its impact on solar irradiance, surface ozone and different meteorological parameters over eight cities of India

• First time study of annular solar eclipse effect simultaneously at eight stations of India. • Stations are located nearly perpendicular to the eclipse axis with magnitude 98.6% to 77.2%. • Substantial reduction in solar radiation, surface ozone & temperature is evident. • Atmospheric cooling from eclipse induced dynamical changes to the meteorological parameters. The present study is aimed to investigate the variation in solar radiance, surface ozone, temperature, relative humidity and wind velocity during the most recent and one of the most significant annular solar eclipses of 21st June 2020. Effects of solar eclipse have been analyzed first time at eight different cities of India located nearly perpendicular to the eclipse axis having an eclipse magnitude from 98.6 % to 77.2 %. Significant reductions in solar irradiance at different stations were found during the maximum phase of the solar eclipse due to the occultation of the Sun by the Moon. With the progression of the solar eclipse, surface ozone concentrations were also found to be decreasing and reached to its minimum value during the maximum phase of eclipse and then after the end of the eclipse started regaining their original behavior. Overall, the change in ozone was found to be proportional to eclipse magnitude. A decrease of ozone levels ranged from 30 % to 65 % over all the stations. In addition to the above, atmospheric cooling from the solar eclipse of 21st June 2020 induced dynamical changes to the meteorological parameters (temperature, relative humidity and wind speed) with the change being most prominent during the maximum phase of the solar eclipse.

REACTION PARAMETERS FOR ‘O+ + N2 ' COLLISION RESPONSE TO SOLAR ECLIPSE

The ionosphere is the part of the earth's atmosphere that extends from about 75 km to 1000 km. The sun is the main factor in shaping and dividing the ionosphere according to electron density. Therefore, the investigation and examination of solar-induced events is of great importance in understanding the structure of the ionosphere. The solar eclipses are one of the most important solar-induced events that cause sudden and medium-scale changes on the ionosphere. The solar eclipse of 29 March 2006 was observed as a total eclipse in some places and as a partial eclipse in some places. One of the regions recorded as a partial eclipse is Kharkov/Ukraine. In this study, the variations of reaction dynamics such as rate constant and cross section of the ‘O+ + N2’ collision, which is one of the ionosphere reaction processes, were investigated according to altitude (187 km) and local time during the 29 March 2006 solar eclipse over the city of Kharkov. The findings revealed that the changes in the reaction rate constant were similar to the changes in temperature, but the same similarities were not observed in the collision cross-section changes. According to another result obtained from this study, it has been determined that the use of experimental-based sources such as Kharkov incoherent scatter radar will give more effective results in investigating the effects of solar eclipses on the ionosphere.

Analyzing Regional and Local Changes in Irradiance during the 2019 Total Solar Eclipse in Chile, Using Field Observations and Analytical Modeling

Solar eclipses are astronomic phenomena in which the Earth’s moon transits between the planet and the Sun, projecting a shadow onto the planet’s surface. As solar power installed capacity increases, detailed studies of this region-wide phenomenon’s effect in irradiance is of interest; however, the literature mainly reports its effects on localized scales. A measurement campaign spanning over 1400 km was pursued for the 2 July 2019 total solar eclipse in Chile, to register the event and establish a modeling framework to assess solar eclipse effects in irradiance over wide regional scales. This work describes the event and presents an estimation framework to decompose atmospheric and eclipse effects on irradiance. An analytical model was applied to study irradiance attenuation throughout the Chilean mainland territory, using satellite-derived and astronomical data as inputs compared to ground measurements in eight stations. Results showed good agreement between model and observations, with Mean Bias Errors of −0.008 to 0.98 W/m2 for Global Horizontal Irradiance and −0.004 to −4.664 W/m2 for Direct Normal Irradiance, with Normalized Root Mean Squared Errors of 0.7–5.8% and 1.4–12.2%, respectively. Energy losses due to obscuration corresponded between 20–40% for Global Horizontal Irradiance and 25–50% for Direct Normal Irradiance over Chilean territory.

The Solar Eclipse Effects on the Upper Thermosphere

AbstractTheoretical studies have shown that the solar eclipse can have significant impacts on the thermospheric mass density, which, however, has not been confirmed from the observational perspective. In this study, we present direct observations of the thermospheric density responses to three solar eclipses based on the measurements of Gravity Recovery and Climate Experiment (GRACE) and Gravity field and steady state Ocean Circulation Explorer (GOCE). It was observed that the eclipses induced about 20% and 25% density depletions at GRACE altitudes (360 and 480 km, respectively) and about 10% depletions at GOCE altitudes (∼270 km). Moreover, the eclipse could generate large‐scale traveling atmospheric disturbances (TADs), which propagate globally even from the duskside to the dawnside after the eclipse ended. Those thermospheric responses could be generally reproduced by Thermosphere Ionosphere Electrodynamics General Circulation Model (TIEGCM). However, the simulated densities recover more rapidly than the observations at the duskside. This study provides observational evidence to validate the results from theoretical models and further bring insights into the mechanism of eclipse effects on the ionosphere‐thermosphere system.

Atmospheric boundary layer response sequence to the 2019 annular solar eclipse over a tropical rural terrain

ABSTRACT Transient alterations in the surface meteorological parameters and atmospheric boundary layer (ABL) due to annual solar eclipse occurred on 26 December 2019 have been investigated using collocated ground-based remote-sensing and in situ measurements over a tropical rural station, Gadanki (13.5 ºN, 79.2 ºE). This event had provided an opportunity to assess the eclipse effect on atmospheric parameters as it occurred during initial hours of the boundary layer evolution (between 08:07 IST and 11:15 IST with peak at 09:32 IST over Gadanki). As eclipse commenced, the observations showed a dramatic reduction in the incoming shortwave radiation and consequent changes in air temperature and wind patterns throughout the ABL. Nevertheless, the amplitude of the changes in various parameters is not analogous to the obscuration proportions but is significantly dictated by the background meteorological conditions such as prevalence of dense fog and cloudiness during the eclipse timings. Ceilometer and wind profiler observations have provided the high-resolution continuous signatures of clouds and fog, strong subsidence, thick layers above the ABL, and a clear change in ABL height (ABLH) during the eclipse epoch. Interestingly, the delay in the evolution of ABL due to the eclipse is clearly manifested. The ABLH, which remained shallow even after the eclipse peak, has shown a rapid increase by more than 1000 m within a short span of an hour just before and after the eclipse culmination. However, significant delay (of about 2 hours after the eclipse) is observed in the surface variables to fall in the range of their climatological values. The observations elusively suggest that commence and termination phases of eclipse analogously influenced the surface and boundary layer parameters in descending sequence (eclipse effect is subtly seen first in Ceilometer and wind profiler attributes followed by surface state variables).

Optimal Q-laws via reinforcement learning with guaranteed stability

Closed-loop feedback-driven control laws can be used to solve low-thrust many-revolution trajectory design and guidance problems with minimal computational cost. Lyapunov-based control laws offer the benefits of increased stability whilst their optimality can be increased by tuning their parameters. In this paper, a reinforcement learning framework is used to make the parameters of the Lyapunov-based Q-law state-dependent, increasing its optimality. The Jacobian of these state-dependent parameters is available analytically and, unlike in other optimisation approaches, can be used to enforce stability throughout the transfer. The results focus on GTO–GEO and LEO–GEO transfers in Keplerian dynamics, including the effects of eclipses. The impact of the network architecture on the behaviour is investigated for both time- and mass-optimal transfers. Robustness to navigation errors and thruster misalignment is demonstrated using Monte Carlo analyses. The resulting approach offers potential for on-board autonomous transfers and orbit reconfiguration.