Moon Shadow Research Articles

Data quality control system and long-term performance monitor of LHAASO-KM2A

The KM2A is the largest sub-array of the Large High Altitude Air Shower Observatory (LHAASO). It consists of 5216 electromagnetic particle detectors (EDs) and 1188 muon detectors (MDs). The data recorded by the EDs and MDs are used to reconstruct primary information of cosmic-ray and gamma-ray showers. To ensure the reliability of the LHAASO-KM2A data, a three-level quality control system has been established. It is used to monitor the status of detector units, stability of reconstructed parameters and the performance of the array based on observations of the Crab Nebula and Moon shadow. This paper will introduce the control system and its application on the LHAASO-KM2A data collected from August 2021 to July 2023. During this period, the pointing and angular resolution of the array were stable. From the observations of the Moon shadow and Crab Nebula, the results achieved using the two methods are consistent with each other. For example, according to the observation of the Crab Nebula with KM2A at energies from 25 TeV to 100 TeV, the time averaged pointing errors are estimated to be −0.003°±0.005° and 0.001°±0.006° in the R.A. and Dec directions, respectively.

Ningaloo eclipse: moon shadow speed and land surface temperature effects from Himawari-9 satellite measurements

Ningaloo eclipse: moon shadow speed and land surface temperature effects from Himawari-9 satellite measurements

Analysis of Moon shadow from 2021-2022 LHAASO WCDA Data

The Large High Altitude Air Shower Observatory (LHAASO) is a major ground-based array of cosmic-ray (CR) detectors in the Sichuan Province in China. The Water Cherenkov Detector Array (WCDA) is an essential component of LHAASO, which is designed to measure ~1-50 TeV CRs and gamma rays. As observed on Earth, the Moon blocks some CRs to create a shadow. Although CRs are mostly protons, WCDA can probabilistically identify some constituents (mostly electrons and photons) of CRs which produce electromagnetic (EM) showers in the atmosphere, using the “compactness” (C) of the showers as the criterion for which the higher C indicates the higher probability of an event being EM. The observed CR Moon shadow positions must be shifted from that of the actual Moon due to the deflection of charged particles by the Earth’s magnetic field. We analyze the LHAASO WCDA data from March 2021 to December 2022 to study the properties of the CR Moon shadows for events with C < 10 and C > 10, such as the shifted position and the size of the shadow at different energies. We found that i) CR shadows’ shifts decrease when energy increases, and ii) the higher the energy, the size of the CR shadows are more compact. This analysis is useful for detector calibration, event selection study, and understanding CR trajectories in the geomagnetic field.

Update on the angular resolution of GRAPES-3 experiment based on Moon shadow analysis

GRAPES-3 is an extensive air shower array located at Ooty (11.6^\circ°N, 76.7^\circ°E, 2200 m a.s.l.) in southern India. Recently, the angular resolution of the GRAPES-3 array has been improved by correcting the shower front curvature based on the shower size and age. Here, we present the results of the angular resolution and pointing accuracy of the array through observation of the Moon shadow. We have analyzed the data for the period of 2014-2016 containing \sim∼ 3 \times× 10^99 air shower events with a median energy of 15 TeV. A significant improvement in the angular resolution has been observed compared to the earlier analysis by the group through the Moon shadow method and is comparable to the arrays located at a 2 km higher altitude than the GRAPES-3 experiment.

Ionospheric Changes over the Western Pacific Ocean near and after the End of Annular Solar Eclipse on 21 June 2020

The center path of the 21 June 2020 solar eclipse, which passed through Guam (13.62°N, 144.86°E, 94.6% obscuration), United States, at the end of its journey, provides a peculiar opportunity to study the ionospheric changes as the moon shadow moves into the nightside. In this study, remote-sensing observations of the ionosphere taken from the ionosonde, and total electron content from the International GNSS Service over Guam were analyzed to examine the related ionospheric changes. Independent in situ observations of electron density (Ne), electron (Te) and ion temperatures (Ti) from DMSP-F17 at ~850 km, and Ne and Te from Swarm-B at ~540 km were also studied. With a significant enhancement of the critical frequency and downward movement of F2-layer, the ionosphere was compressed as the moon shadow swept over Guam near its sunset hours. Neutral wind observations from the Ionospheric Connection Explorer (ICON) showed the westward reversed wind occurring in the F-region near sunset. The westward wind disturbance and downward press over the Western Pacific suggest changes in the electrodynamics in the ionosphere and thermosphere near sunset at the end of the solar eclipse, which further contributes to ~85% decrease of Ne and 157% enhancement of Te at ~540 km near midnight.

PENERAPAN FILSAFAT ILMU BIDANG PENDIDIKAN DI SEKOLAH DASAR

An action or activity that we carry out in a planned and earnest manner in achieving a certain goal is an application. It is an act that puts into practice a theory that has been prepared previously. Related to philosophy and science are two related words, substantially and historically, in which science cannot be separated from the role of philosophy. But on the contrary the development of science can strengthen the existence of philosophy. The birth of philosophy in Greece shows the pattern of thought of the Greeks in which mythological views eventually disappeared and rational statements were dominant. Where according to philosophy, the application is where the mindset that often depends on gods turns into a mindset that depends on ratios. Natural events, such as eclipses are no longer considered as activities of sleeping gods, but are natural occurrences caused by the sun, moon and earth being in parallel lines, so that the moon's shadow falls on part of the earth's surface.&#x0D; &#x0D; Keywords:

Reimagining Chinese American Identity: Postcolonial Perspectives on Cultural Negotiation and Transformation in Laurence Yep’s Dragonwings

The Chinese immigrant and Chinese American communities have faced a long history of stigmatisation and misrepresentation due to racial bias and discrimination. This article explores the transformative growth narrative of the child protagonist in Laurence Yep’s novel Dragonwings, set against the backdrop of historical anti-Asian sentiment in the early 1900s. By adopting Said’s “imaginative geography” and Bhabha’s “third space” as analytical perspectives, the study aims to shed light on how the child protagonist’s growth challenges passive Chinese stereotypes and confronts deeply ingrained adversities within the Asian American diaspora by offering an active anti-Oriental perspective. We argue that the transformative journey of the protagonist, Moon Shadow, contests racial biases and cultural boundaries, contributing to a reflective perspective that liberates writers of colour from complicit interrogations. The analysis underlines the transgressive aesthetic within the Chinese American diaspora, showcasing Dragonwings as a quintessential postcolonial bildungsroman that embraces compromise and accommodation in selfformation. Furthermore, the exploration of the child protagonist’s growth in the context of historical realist narrative and the postcolonial lens emphasises the transgressive enjoyment that subverts established norms and identities. The study thus acknowledges the resilience and agency exhibited by the characters in the face of adversity and by understanding the emancipatory potential of growth narratives, it contributes to the broader theme of overcoming adversity and embracing change in the context of language and culture in Asia.

Investigation on the cosmic-ray shadow of planets and asteroids

The moon shadow and sun shadow of cosmic rays are commonly used to calibrate the angular resolution of the instrument in extensive air shower experiments, measure the proton-antiproton ratio, and study the interplanetary magnetic field (IMF). The shadow effect of planets and asteroids in the solar system, on the other hand, has received little attention. If considerable shadow effects can be observed, a novel approach may be developed to calibrate the point spread function and investigate the IMF. In this work, we calculate the sensitivity of observing the shadow effects of planets and asteroids in the next hundred years using LHAASO’s instrumental response as an example. The result shows that the blocking impact of these celestial bodies is minimal; thus, their influence on the direction distribution of cosmic rays is negligible.

Validating the improved angular resolution of the GRAPES-3 air shower array by observing the Moon shadow in cosmic rays

Validating the improved angular resolution of the GRAPES-3 air shower array by observing the Moon shadow in cosmic rays

Enhancement of Electron Density in the Ionospheric F2 Layer Near the First Contact of the Total Solar Eclipse on 21 August 2017

AbstractIt can be expected that a moon shadow of solar eclipse can largely reduce the ionospheric electron density (Ne) during the obscuration. However, in this study, the total electron content (TEC) from the ground‐based Global Navigation Satellite System receivers recorded a significant Ne enhancement over the continental United States (CONUS) near the first contact of the total solar eclipse on 21 August 2017. The ionosonde observations of the F2‐layer peak density (NmF2) and its height (hmF2) over Idaho National Lab (43.81°N, 112.68°W, 99.6% obscuration), ID, and Boulder (40°N, 105.3°W, 93.1% obscuration), CO, verified the unexpected early enhancement. The ionospheric Ne starts to enhance at ∼1520 UT (before the obscuration) and increases by ∼25% to ∼80% at ∼1600 UT (near the first contact) in the F2 layer. The early enhancement reveals the ascension of the F2 layer that tilted east over the CONUS.

Local and conjugate ionospheric total electron content variation during the 21 June 2020 solar eclipse

• Ionospheric TEC showed an asymmetric latitudinal depletion around totality path. • Ionospheric disturbances in both local and conjugate eclipse regions were analyzed. • Eclipse-induced ionospheric bow wave structures and TIDs were identified. This paper studies the ionospheric response to a low-latitude annular solar eclipse event on 21 June 2020 at both eclipse and conjugate regions using a dense network of Global Navigation Satellite Systems receivers, Defense Meteorological Satellite Program and Swarm satellites data, as well as ionosonde measurements over the Asian-Oceania sector. The large scale ionospheric variation and small scale wave-like perturbations during the eclipse were analyzed by using high-resolution Total Electron Content (TEC) maps and in-situ electron density/temperature data. The main results are as follows: (1) A local TEC reduction of 4–7 TEC Unit ( ∼ 30–50%) was identified along the totality path, with larger depletion in the southern edge of totality path than the northern edge. (2) The equatorial ionization anomaly in the Asian sector exhibited a complicated variation pattern with a slightly different longitudinal/local time and altitudinal response, which showed considerable TEC/ Ne depletion in the East Asian sector and at ∼ 850 km close to local afternoon during the eclipse, but a slight TEC/ Ne enhancement around the Indian sector and at ∼ 500 km in the post-eclipse periods. (3) Large ionospheric perturbations were identified that traveled at approximately the same velocity as the supersonic moon shadow, and the ionospheric bow wave features were also triggered by the solar eclipse. (4) The Oceania TEC in the Southern Hemisphere conjugate location experienced a coincident minor reduction and wave-like fluctuations during the eclipse, likely indicating some possible interconnections between the eclipse and the conjugate ionospheres.

Calibration of the air shower energy scale of the water and air Cherenkov techniques in the LHAASO experiment

The Wide Field-of-View Cherenkov Telescope Array (WFCTA) and the Water Cherenkov Detector Arrays (WCDA) of LHAASO are designed to work in combination for measuring the energy spectra of various cosmic ray species over a very wide energy range from a few TeV to 10 PeV. The energy calibration of WCDA can be achieved with a proven technique of measuring the westward shift of the Moon shadow of galactic cosmic rays due to the geomagnetic field. This deflection angle $\Delta$ is inversely proportional to the energy of the cosmic rays. The precise measurements of the shifts by WCDA allows us to calibrate its energy scale for energies as high as 35 TeV. The energy scale measured by WCDA can be used to cross calibrate the energy reconstructed by WFCTA, which spans the whole energy range up to 10 PeV. In this work, we will demonstrate the feasibility of the method using the data collected from April 2019 to January 2020 by the WFCTA array and WCDA-1 detector, the first of the three water Cherenkov ponds, already commissioned at LHAASO site.

Restoring the top-of-atmosphere reflectance during solar eclipses: a proof of concept with the UV absorbing aerosol index measured by TROPOMI

Abstract. During a solar eclipse the solar irradiance reaching the top of the atmosphere (TOA) is reduced in the Moon shadow. The solar irradiance is commonly measured by Earth observation satellites before the start of the solar eclipse and is not corrected for this reduction, which results in a decrease in the computed TOA reflectances. Consequently, air quality products that are derived from TOA reflectance spectra, such as the ultraviolet (UV) absorbing aerosol index (AAI), are distorted or undefined in the shadow of the Moon. The availability of air quality satellite data in the penumbral and antumbral shadow during solar eclipses, however, is of particular interest to users studying the atmospheric response to solar eclipses. Given the time and location of a point on the Earth's surface, we explain how to compute the obscuration during a solar eclipse, taking into account wavelength-dependent solar limb darkening. With the calculated obscuration fractions, we restore the TOA reflectances and the AAI in the penumbral shadow during the annular solar eclipses on 26 December 2019 and 21 June 2020 measured by the TROPOMI/S5P instrument. We compare the calculated obscuration to the estimated obscuration using an uneclipsed orbit. In the corrected products, the signature of the Moon shadow disappeared, but only if wavelength-dependent solar limb darkening is taken into account. We find that the Moon shadow anomaly in the uncorrected AAI is caused by a reduction of the measured reflectance at 380 nm, rather than a colour change of the measured light. We restore common AAI features such as the sunglint and desert dust, and we confirm the restored AAI feature on 21 June 2020 at the Taklamakan Desert by measurements of the GOME-2C satellite instrument on the same day but outside the Moon shadow. No indication of local absorbing aerosol changes caused by the eclipses was found. We conclude that the correction method of this paper can be used to detect real AAI rising phenomena during a solar eclipse and has the potential to restore any other product that is derived from TOA reflectance spectra. This would resolve the solar eclipse anomalies in satellite air quality measurements in the penumbra and antumbra and would allow for studying the effect of the eclipse obscuration on the composition of the Earth's atmosphere from space.

From Bow Waves to Traveling Atmospheric Disturbances: Thermospheric Perturbations Along Solar Eclipse Trajectory

AbstractIn this study, we investigate the characteristics of thermospheric perturbations triggered by a set of four solar eclipses, using the Thermosphere Ionosphere Electrodynamics General Circulation Model. Simulations show that temperature and horizontal wind perturbations have different wave rears but similar wavefronts, due to the coupling of energetic and dynamic processes. The perturbations are closely related to the eclipse trajectory, and their phase speed is modulated by the eclipse speed. As the eclipse shadow sweeps through the upper atmosphere, traveling atmospheric disturbances (TADs) are launched in the eclipse region and they, moving along with their moon shadow source, form bow wavefronts of thermospheric disturbances. The perturbations at a particular time are superimposed by preexisting waves and newly excited waves. With the termination of the eclipse near the sunset terminator, individual sequences are not any more organized along a specific alignment to form a bow wave. Instead, they evolve into freely propagating large‐scale TADs. The large‐scale TADs remain propagating in the direction perpendicular to the wavefronts, which is determined by history of the eclipse trajectory and thermospheric conditions. These conditions include specifically season and the latitudinal location of the eclipse trajectory.

Multilayered Sporadic‐E Response to the Annular Solar Eclipse on June 21, 2020

AbstractA moon shadow of annular solar eclipse passed through East Asia in the afternoon on June 21, 2020, which was a good opportunity to study the rapid ionospheric response to the solar radiation variations. In the study, the high‐frequency echoes recorded by the ionosondes at Wuhan (82.4% obscuration), Xiamen (97.8% obscuration), and Nanning (81.1% obscuration) are analyzed to examine the variations in sporadic‐E (Es) during the obscuration over the East China area. The echoes show not only the variations in the typical signal Es layer below 130 km, but for the first time also the multilayered Es at much higher altitudes (130–190 km) during the eclipse. Specifically, the multilayered Es is only observed over Nanning, while different Es behaviors are observed in the other two stations. The relationship between the formation of the multilayered Es and the uplifted Es near the center path of the moon shadow are examined in the study. The small‐scale atmospheric gravity waves play a key role in modulating the Es behaviors during the eclipse.

Wave Steepening in Ionospheric Total Electron Density due to the 21 August 2017 Total Solar Eclipse

AbstractThis study shows that a supersonic moon shadow of a total solar eclipse can steepen the ionospheric total electron content (TEC) wave on August 21, 2017. A data‐adaptive method named Hilbert‐Huang transform is employed to examine the nonlinear and non‐stationary evolution of the waves. The results show that the TEC wave behaves as a traveling ionospheric disturbance before the totality appearance, turns later into steepening, and breaks eventually. A TEC wave with a period of ∼40 min and wavelength of ∼1,000 km propagates mainly in an east‐southward direction before the totality appearance. The wave amplitude and scales, respectively, increases and reduce by near ∼50% as the moon shadow approaches the western coast of the continental United States. The short‐period TEC waves (period ∼2 min) reveal that the wave may break eventually when the wave gets steeper. The steepness of the TEC wave is reconstructed according to the constructive interference.

Conjugate Ionospheric Perturbation During the 2017 Solar Eclipse

AbstractWe report new findings of total electron content (TEC) perturbations in the southern hemisphere at conjugate locations to the northern eclipse on August 21, 2017. We identified a persistent conjugate TEC depletion by 10%–15% during the eclipse time, elongating along magnetic latitudes with at least ∼5° latitudinal width. As the Moon's shadow swept southward, this conjugate depletion moved northward and became most pronounced at lower magnetic latitudes (&gt;−20°N). This depletion was coincident with a weakening of the southern crest of the equatorial ionization anomaly (EIA), while the northern EIA crest stayed almost undisturbed or was slightly enhanced. We suggest these conjugate perturbations were associated with dramatic eclipse initiated plasma pressure reductions in the flux tubes, with a large portion of shorter tubes located at low latitudes underneath the Moon's shadow. These short L‐shell tubes intersect with the F region ionosphere at low and equatorial latitudes. The plasma pressure gradient was markedly skewed northward in the flux tubes at low and equatorial latitudes, as was the neutral pressure. These effects caused a general northward motion tendency for plasma within the flux tubes, and inhibited normal southward diffusion of equatorial fountain plasma into the southern EIA region. We also identified posteclipse ionospheric disturbances likely associated with the global propagation of eclipse‐induced traveling atmospheric disturbances in alignment with the Moon's shadow moving direction.

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From a monarch mystery unlocked with the help of Indigenous people to an environmental disaster averted by a chemist who was not afraid of a fight, this year's finalists for the AAAS/Subaru (SB&amp;F) Prize for Excellence in Science Books highlight how diverse perspectives, grit, and a healthy dose of hope are essential to the effective practice of science. Read on for reviews of the finalists written by the staff of the Science family of journals, with help from a few friends.

Multiple Technique Observations of the Ionospheric Responses to the 21 June 2020 Solar Eclipse

AbstractWe investigate the ionospheric response to the 21 June 2020 annular solar eclipse using the multiinstrument observations including ionosondes, Global Navigation Satellite System (GNNS) receivers, COSMIC2, and DMSP and SWARM satellites. During the course of the eclipse, total electron content (TEC) decreased slightly in the morning at 20–70°E and largely in the afternoon at 80–150°E. However, maximum TEC depletion did not occur at the maximum obscuration, but stayed close to the southern edge of the running totality during the eclipse and near the northern edge of the elapsed totality after the eclipse. NmF2 showed the similar variation as TEC around 110°E. Meanwhile, a northward disturbance field‐aligned plasma drift was observed in the eclipse region and the disturbance became strong in the southern side of the totality around 120°E. The TEC and Swarm data revealed that the crests of the equatorial ionization anomaly (EIA) enhanced on both sides of the equator around noon in ~50–100°E although the northern crest was still in the Moon's shadow. The COSMIC2 profiles displayed the enhanced electron density in ~300–500 km altitudes and decreased density below ~300 km altitudes around the EIA crests in ~70°E. The Swarm observations recorded a drop in the electron temperature both in eclipse region and in conjugate hemisphere in 77°E and 96°E. The combined effect from the electric field, neutral wind, thermal conduction, and interhemispheric photoelectron transport might result in the complicated space and time variations of ionospheric responses to the eclipse.

Atmospheric Gravity Waves Observed in the Nightglow Following the 21 August 2017 Total Solar Eclipse

AbstractNighttime airglow images observed at the low‐latitude site of São João do Cariri (7.4°S, 36.5°W) showed the presence of a medium‐scale atmospheric gravity wave (AGW) associated with the 21 August 2017 total solar eclipse. The AGW had a horizontal wavelength of ∼1,618 km, observed period of ∼152 min, and propagation direction of ∼200° clockwise from the north. The spectral characteristics of this wave are in good agreement with theoretical predictions for waves generated by eclipses. Additionally, the wave was reverse ray‐traced, and the results show its path crossing the Moon's shadow of the total solar eclipse in the tropical North Atlantic ocean at stratospheric altitudes. Investigation about potential driving sources for this wave indicates the total solar eclipse as the most likely candidate. The optical measurements were part of an observational campaign carried out to detect the impact of the August 21 eclipse in the atmosphere at low latitudes.