Observations Of Solar Eclipse Research Articles

Education and observation of the 2023 hybrid solar eclipse in Southwest Papua

On April 20, 2023, the Southwest Papua region was the areas crossed by a hybrid solar eclipse. This outreach aims to enhance the community's understanding and awareness regarding the safety of solar eclipse observation by conducting observations at several locations in Southwest Papua. The Solar Gehana Education and Observation Program was successfully implemented in 6 Regencies/Cities in Southwest Papua. This activity was carried out using mini-lectures, pinhole training, and joint eclipse observations. In general, this program can increase public understanding and awareness regarding the safety of observing solar eclipses, with the training participants' response score being 79.92% in the good category. Apart from that, this program has succeeded in touching and opening people's insight into this fascinating natural phenomenon through widespread publication in the mass media, both regional and national.

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.

Retrievals of vertical distribution of Martian water vapor from combined day and night MGS TES nadir spectra

Vertical distribution of water vapor in the Martian lower atmosphere (0–40 km) is an important characteristic of the Martian water cycle. It reflects a complex interplay between various processes shaping the contemporary water cycle, including atmospheric transport, formation of water ice clouds, sublimation of surface frost, and possible interaction with the subsurface. Despite the growing dataset of water vapor observations, there is yet no comprehensive climatology of the vertical distribution of vapor. Limb and solar occultation observations that are typically used to retrieve vapor vertical distribution are much less numerous than nadir observations and are available for limited seasons and locations. We propose a new methodology to retrieve vertical distribution of water vapor in the Martian lower atmosphere using only nadir data. The methodology is based on the observation that infrared spectra collected over same location during different parts of day are sensitive to water vapor in different parts of the atmosphere. We validate our new methodology by applying it to infrared spectra simulated for realistic Mars environments created with Mars General Circulation Model (GCM). These tests show that vertical profiles of vapor can be recovered with accuracy ~20–40%, which is comparable to accuracy of limb and occultation observations. Importantly, the new retrieval algorithm can constrain near-surface (0–10 km) vapor abundances that cannot be observed by limb and occultation techniques. Application of this new methodology to a large dataset on Martian nadir spectra, such as the one collected by the Thermal Emission Spectrometer (TES) onboard Mars Global Surveyor (MGS) during its mission in 1999–2004, can result in the development of the detailed climatology of vapor vertical distribution on Mars. As an initial step toward this goal, we apply the new retrieval methodology to a subset of nadir spectra collected by MGS TES during one Martian year. The retrieved vapor profiles are qualitatively consistent with vapor distributions predicted by the GCM for different seasons. Differences between retrieved and simulated profiles can be interpreted as reflecting wetter Martian atmosphere and weaker atmospheric transport, during some seasons. Retrieved vapor distribution during southern summer suggests disruption of atmospheric vapor transport into southern extra-tropics following a global dust storm.

The solar eclipse of A.D. 1221 May 23 and the value of ΔT

A total solar eclipse was recorded in a classic Chinese book with the title The Travels of an Alchemist: the Journey of the Taoist Ch’ang Ch’un from China to the Hindukush at the Sumons of Chingiz Khan. In the present paper, possible locations of the solar eclipse observation are investigated, taking into account the geographical characteristics of local environments. With a modern astronomical planetary ephemeris, the authors confirm the observation records and derive an upper limit of +768 seconds for the Δ T value at the epoch A.D. 1221.

Lunar Solar Occultation Explorer (LunaSOX)

In the present decade and beyond, now 51 years after the last Apollo landing, the NASA Artemis human exploration program will offer abundant opportunities for heliophysics investigations from, by, and of the Moon from the vantage points of the lunar orbit and the surface. The Lunar Solar Occultation Explorer (LunaSOX) concept uses the lunar limb to occult the solar disk for high-resolution coronal observations at hourly, daily, to biweekly cadences from spacecraft either in the lunar orbit or at the surface. A 0.2 m diameter solar telescope in orbit with white light and narrow-band visible filters would provide arcsecond spectroscopic imaging of the low-to-high corona (1–10 R☉) with an upper limit of 10–12 B☉ on the local scattered light background from lunar atmospheric dust, as compared to 10–9 B☉ for Earth ground-based solar eclipse observations looking up through the atmosphere at totality. For eclipse observations from and by the Moon, there would be no significant atmospheric disturbances that otherwise limit seeing to arcsec resolution from Earth’s surface. The present eccentric orbits of the ARTEMIS P1 and P2 spacecraft are used as models for a 1 × 10 Rm orbit of LunaSOX to compute the times of solar eclipse intervals, up to 2 hours in duration between the east and west solar hemispheres at a daily cadence for coronal observations at 1–16 R☉ when the orbital aposelene is in anti-sunward directions. In a low-altitude circular orbit and from the surface, the observational cadences would, respectively, be hourly and biweekly. LunaSOX satellites also carrying in situ space environment instruments could integrate into a network of orbital platforms for space weather monitoring and communications relay to far-side surface lander and permanent base sites, e.g., for low-frequency radio cosmology and detection of exoplanet magnetospheres.

Study on Secular Change of the Earth’s Rotation Rate Based on Solar Eclipse Observation Records on October 13, 443 BC

ABSTRACT An observation of a solar eclipse that occurred on October 13, 443 BC during the reign of the Duke Ligong of Qin was recorded in the Twenty-Four Histories (China’s dynastic histories from remote antiquity till the Ming Dynasty). With modern astronomical planetary ephemeris, the observation records were studied. The results showed that the eclipse probably occurred around sunset in Yongcheng, the capital of Qin, where the sunset time was exactly between the first contact stage (partial eclipse begins) and the fourth contact stage (partial eclipse ends) of the eclipse. Furthermore, secular change of the earth’s rotation rate at that time is investigated in this work.

Martian Atmospheric Temperature and Density Profiles During the First Year of NOMAD/TGO Solar Occultation Measurements

AbstractWe present vertical profiles of temperature and density from solar occultation (SO) observations by the “Nadir and Occultation for Mars Discovery” (NOMAD) spectrometer on board the Trace Gas Orbiter during its first operational year, which covered the second half of Mars Year 34. We used calibrated transmittance spectra in 380 scans, and apply an in‐house pre‐processing to clean data systematics. Temperature and CO2 profiles up to about 90 km, with consistent hydrostatic adjustment, are obtained, after adapting an Earth‐tested retrieval scheme to Mars conditions. Both pre‐processing and retrieval are discussed to illustrate their performance and robustness. Our results reveal the large impact of the MY34 Global Dust Storm (GDS), which warmed the atmosphere at all altitudes. The large GDS aerosols opacity limited the sounding of tropospheric layers. The retrieved temperatures agree well with global climate models (GCM) at tropospheric altitudes, but NOMAD mesospheric temperatures are wavier and globally colder by 10 K in the perihelion season, particularly during the GDS and its decay phase. We observe a warm layer around 80 km during the Southern Spring, especially in the Northern Hemisphere morning terminator, associated to large thermal tides, significantly stronger than in the GCM. Cold mesospheric pockets, close to CO2 condensation temperatures, are more frequently observed than in the GCM. NOMAD CO2 densities show oscillations upon a seasonal trend that track well the latitudinal variations expected. Results uncertainties and suggestions to improve future data re‐analysis are briefly discussed.

Calibration of NOMAD on ESA's ExoMars Trace Gas Orbiter: Part 2 – The Limb, Nadir and Occultation (LNO) channel

The Nadir and Occultation for MArs Discovery (NOMAD) instrument is a 3-channel spectrometer suite on the ESA ExoMars Trace Gas Orbiter. Since April 2018, when the nominal science mission began, it has been measuring the constituents of the Martian atmosphere. NOMAD contains three separate spectrometers, two of which operate in the infrared: the Solar Occultation (SO) channel makes only solar occultation observations, and therefore has the best resolving power (∼20,000) and a wider spectral region covering 2.2–4.3 ​μm. The Limb, Nadir and Occultation (LNO) channel covers the 2.2–3.8 ​μm spectral region and can operate in limb, nadir or solar occultation pointing modes. The Ultraviolet–VISible (UVIS) channel operates in the UV–visible region, from 200 to 650 ​nm, and can measure in limb, nadir or solar occultation modes like LNO. The LNO channel has a lower resolving power (∼10,000) than the SO channel, but is still typically an order of magnitude better than previous instruments orbiting Mars. The channel primarily operates in nadir-viewing mode, pointing directly down to the surface to measure the narrow atmospheric molecular absorption lines, clouds and surface features in the reflected sunlight. From the depth and position of the observed atmospheric absorption lines, the constituents of the Martian atmosphere and their column densities can be derived, leading to new insights into the processes that govern their distribution and transport. Surface properties can also be derived from nadir observations by observing the shape of the spectral continuum. Many calibration measurements were made prior to launch, on the voyage to Mars, and continue to be made in-flight during the science phase of the mission. This work, part 2, addresses the aspects of the LNO channel calibration that are not covered elsewhere, namely: the LNO ground calibration setup, the LNO occultation and nadir boresight pointing vectors, LNO detector characterisation and nadir/limb illumination pattern, instrument temperature effects, and finally the radiometric calibration of the LNO channel. An accompanying paper, part 1 (Thomas et al., 2021, this issue), addresses similar aspects for SO, the other infrared channel in NOMAD. A further accompanying paper (Cruz-Mermy et al., 2021, this issue) investigated the LNO radiometric calibration in more detail, approaching the work from a theoretical perspective. The two calibrations agree with each other to within 3%, validating each calibration method. • The LNO channel is 1 of 3 spectrometers in NOMAD on ExoMars Trace Gas Orbiter. • The LNO channel observes Mars in limb, nadir and solar occultation modes. • This article describes the operational modes and calibration of the LNO channel. • The boresight, detector illumination, slant, bad pixels and saturation were found. • The procedure for radiometrically calibrating nadir observations is described.

Calibration of the NOMAD-UVIS data

The Ultraviolet and VIsible Spectrometer (UVIS), covering the 200–650 ​nm range, is one of three spectrometers that comprise the NOMAD instrument on the ExoMars 2016 Trace Gas Orbiter (TGO). UVIS can operate in solar occultation, nadir and limb viewing mode and was designed to monitor ozone and aerosols in the Martian atmosphere. Here, we describe the calibration procedure to convert the UVIS raw data into a calibrated data product ready for scientific exploitation. The calibration includes the CCD offset and dark current subtraction, the wavelength assignment, the noise identification and removal, the smearing removal, and the radiance or transmittance conversion. A straylight correction, critical for some parts of the UVIS spectral range, is also applied during the data reduction process, which is described in more detail in two companion papers [Mason et al., 2022; Depiesse et al., In prep] corresponding to two different and independent methods giving consistent results. The solar occultation observations are converted into transmittance and are therefore self-calibrating, while nadir and limb measurements require an absolute radiometric calibration. A comparison with coincident nadir MRO/MARCI measurements is provided as a final validation and generally shows a ±10% agreement on the radiances measured by both instruments. • Description of the calibration of UVIS measurements to produce level 1 data from raw data • CCD non-linearity correction, offset removal, dark current removal, Bad pixel removal, Smearing removal. • A straylight correction is also applied but described in companion papers. • Conversions: Pixel-wavelength assignment, Radiance (nadir) or Transmittance (occultation) conversion. • Radiometric comparison with coincident MRO/MARCI measurements, serving as validation for the radiance calibrated data.

Solar occultation observations of Saturn's rings with Cassini UVIS

The Ultraviolet Imaging Spectrograph (UVIS) instrument onboard the Cassini spacecraft observed 41 solar occultations by Saturn's rings through its extreme ultraviolet (56–118 nm) spectrographic channel. These solar occultations complement the set of stellar occultations measured by the broadband UVIS High Speed Photometer in the far ultraviolet (110–190 nm). We provide a uniform calibration of all of the UVIS solar occultation data across the full ring system. We have compiled complete catalogs of these occultations as high-level data products delivered to the Planetary Data System (PDS) Ring Moon Systems Node. This manuscript serves as a guide to this dataset and the corresponding high-level data products outlining their value for analysis of Saturn's rings. These products include light curves and optical depth profiles as functions of ring radius. In addition to providing key parameters of interest obtained through each of these occultations, we show that the optical depths of various ring regions derived from solar occultations are consistent with those from stellar occultations. We also demonstrate that fits to self-gravity wake parameters are similar for solar and stellar occultations. Lastly, we identify a variety of potential spectral trends at various ring locations that future investigations may further explore to address key questions pertaining to the properties of Saturn's rings.

Why total solar eclipses are important to science?

Abstract Despite today we have plenty of opportunities for high-quality observations of the Sun from both Earth and space, total solar eclipses remain a rare chance to explore the corona, its features and various atmospheric phenomena. Members of our team took part of 5 out of 6 Bulgarian expeditions for total solar eclipse observations ever realized. In the current paper we summarize the tasks we fulfilled and the scientific results we obtained. Special attention is paid to the investigation of the shadow bands that accompanied the last eclipse we witnessed – on 2019 July 2.

Application of NASA core Flight System to Telescope Control Software for 2017 Total Solar Eclipse Observation

The core Flight System (cFS), developed by NASA, is a reusable software framework and a set of pluggable software applications that take advantage of the rich heritage of NASA’s successful space missions. We applied the cFS to the development of telescope control software for the observation of the 2017 total solar eclipse. Four main modules were developed: imaging control, mechanism control, data handling, and automated observation. Other modules, such as communication and scheduler, were reused from the cFS. Using an integrated observation system, we successfully observed the total solar eclipse, in which the linearly polarized brightness of the solar corona and sky background were measured at four different wavelengths. In this study, we demonstrated the usefulness of the cFS to develop telescope control software through an eclipse observation system, the so-called DICE (DIagnostic Coronagraph Experiment) mission. Our experience and knowledge of the cFS were expanded to a flight software BITSE (Balloon-borne Investigation of Temperature and Speed of Electrons in the corona), the high-altitude scientific balloon mission in 2019. We plan to apply this approach to future solar coronagraph observations, such as CODEX (COronal Diagnostic EXperiment), on the International Space Station. We expect that the cFS can also be applied in telescope control software for ground-and space-based observations.

Isotopic Composition of CO2 in the Atmosphere of Mars: Fractionation by Diffusive Separation Observed by the ExoMars Trace Gas Orbiter

AbstractIsotopic ratios in atmospheric CO2 are shaped by various processes throughout Mars' history, and can help understand what the atmosphere of early Mars was like to sustain liquid water on its surface. In this study, we monitor the O and C isotopic composition of CO2 between 70 and 130 km for more than half a Martian year using solar occultation observations by the Atmospheric Chemistry Suite onboard the ExoMars Trace Gas Orbiter. We find the vertical trends of the isotopic ratios to be consistent with the expectations from diffusive separation above the homopause, with average values below this altitude being consistent with Earth‐like fractionation (δ13C = −3 ± 37‰; δ18O = −29 ± 38‰; and δ17O = −11 ± 41‰). Using these measurements, we estimate that at least 20%–40% of primordial C on Mars has escaped to space throughout history. The total amount of C lost from the atmosphere is likely to be well in excess of this lower limit, due to carbonate formation and further sink processes. In addition, we propose a photochemical transfer of light O from H2O to CO2 to explain the larger enrichment in the ratio in H2O than in CO2.

TOTAL SOLAR ECLIPSES THEN AND NOW

I describe the new equipment and observations of the major total solar eclipse that passed from Mexico (where we observed it, in Miahuatlán, Oaxaca) on 7 March 1970, to the improved imaging and other capabilities we applied to the recent total solar eclipses of 2 July 2019 (from Chile), and 4 December 2021 (from on and near Antarctica, including airborne observations).

Processing of Observations of the Partial Solar Eclipse on June 21, 2020, in the 3.2- and 4.9-cm Wavelength Regions at the Mountain Astronomical Station of the Central Astronomical Observatory

Processing of Observations of the Partial Solar Eclipse on June 21, 2020, in the 3.2- and 4.9-cm Wavelength Regions at the Mountain Astronomical Station of the Central Astronomical Observatory

Serendipitous observation of a coronal mass ejection during the total solar eclipse of 14 December 2020

We report observations of the total solar eclipse of 14 December 2020, during which a coronal mass ejection was seen to propagate. A comprehensive set of photographs covering a high dynamic range of exposure enabled characterization of its dimensions. Displacement of the front can be seen during the few minutes of totality.

Identifying the Coronal Source Regions of Solar Wind Streams from Total Solar Eclipse Observations and in situ Measurements Extending over a Solar Cycle

Abstract This letter capitalizes on a unique set of total solar eclipse observations acquired between 2006 and 2020 in white light, Fe xi 789.2 nm (T fexi = 1.2 ± 0.1 MK), and Fe xiv 530.3 nm (T fexiv = 1.8 ± 0.1 MK) emission complemented by in situ Fe charge state and proton speed measurements from Advanced Composition Explorer/SWEPAM-SWICS to identify the source regions of different solar wind streams. The eclipse observations reveal the ubiquity of open structures invariably associated with Fe xi emission from Fe10+ and hence a constant electron temperature, T c = T fexi, in the expanding corona. The in situ Fe charge states are found to cluster around Fe10+, independently of the 300–700 km s−1 stream speeds, referred to as the continual solar wind. Thus, Fe10+ yields the fiducial link between the continual solar wind and its T fexi sources at the Sun. While the spatial distribution of Fe xiv emission from Fe13+ associated with streamers changes throughout the solar cycle, the sporadic appearance of charge states >Fe11+ in situ exhibits no cycle dependence regardless of speed. These latter streams are conjectured to be released from hot coronal plasmas at temperatures ≥T fexiv within the bulge of streamers and from active regions, driven by the dynamic behavior of prominences magnetically linked to them. The discovery of continual streams of slow, intermediate, and fast solar wind characterized by the same T fexi in the expanding corona places new constraints on the physical processes shaping the solar wind.

Langevin's influence on relativity theories

A century ago, Paul Langevin [C. R. 173, 831 (1921)], through his influence, convinced the scientific community that Einstein's theories of relativity were correct and could explain the Sagnac effect. A simple note in Comptes Rendus was all it took to silence many prominent skeptical scientists. The relativity skeptics had pointed to Sagnac's experiment [C. R. 157, 1410 (1913)] with the interference of counter rotating light beams as proof that the speed of light was not the same in both directions, contrary to the key postulate in Einstein's theory. Langevin showed that the result was also explained by relativity. The rest is history, and relativity has remained a center piece of theoretical physics ever since. Langevin had been captivated by solar eclipse observations of a shifted star pattern near the sun as reported by Eddington [Report on the Relativity Theory of Gravitation (Fleetway Press, Ltd., London, 1920)]. This was taken as proof positive for Einstein's General Theory of Relativity. The case of a light beam split into two beams, which propagate in opposite directions around a circuit, has an analog in a simple thought experiment—a speed test for runners. Two runners can be timed on a running track with the runners going around the track in opposite directions. Two stop watches will display the time for each runner's return to the starting position. The arithmetic difference in time shown on each stop watch will provide the differences in speed between the two runners. If the two speeds are the same, the time difference will be zero. It would not make any sense for one of the stop watches to measure a negative time, that is, time moving into the past. In fact, the idea is absurd! However, Langevin did just that, assigned the time for light to travel in one direction as positive while the time for the light to traverse in the opposite direction as negative, moving into the past! By so doing, Langevin reproduced Sagnac's expression and declared that relativity explains Sagnac's experiment. Langevin was wrong!

Properties of Water Ice and Dust Particles in the Atmosphere of Mars During the 2018 Global Dust Storm as Inferred From the Atmospheric Chemistry Suite

AbstractThe properties of Martian aerosols are an integral part of the planetary climatology. Global dust storms (GDS) significantly alter spatial and vertical distributions of dust and water ice aerosols and their microphysical properties. We explored the 2018/Martian year 34 GDS with the Atmospheric Chemistry Suite instrument onboard the ESA‐Roscosmos Trace Gas Orbiter mission. Solar occultation observations of thermal infrared and near infrared channels in the 0.7–6 μm spectral range with >103 signal‐to‐noise ratio are used to constrain the vertical dependence and the temporal evolution of the particle properties of water ice and dust (effective radius, effective variance, number density, and mass loading) before the 2018 GDS and during its onset and decay phases. In most of the observations, the particle size of dust and water ice decreases with altitude. The effective radius of dust and water ice particles ranges in 0.1−3.5 μm and 0.1–5.5 μm, respectively. The largest aerosol particles (> 2.5 μm for dust and > 3.5 μm for water ice) are present below 10 km before the onset and during the GDS decay phase. During the peak of the GDS, dust reached altitudes of 85 km; the most frequently observed effective radius is 1–2 μm with 0.1–1 cm−3 number density and 0.1 effective variance. Detached layers of water ice composed of 0.1–1 μm particles are systematically observed at 50–100 km during this period. Below, at 0–50 km, we see the dust mixed with the main water ice layer comprising 1–4 μm particles.

Total Solar Eclipse Observations: A Treasure Trove from the Source and Acceleration Regions of the Solar Wind

A comprehensive exploration of the inner corona, namely the spatial span starting from the solar surface out to a few solar radii, is essential for investigating the physical processes responsible for its quiescent and dynamic state. Such an exploration encompasses the source regions of the solar wind, and is thus essential for reliably establishing their link to in-situ measurements, including those from the more recent Parker Solar Probe mission. Total solar eclipses are the only platform available at present to fulfill these requirements, as they offer a spatially uninterrupted diagnosis of the inner corona through multi-wavelength imaging and spectroscopy. This review highlights results from almost two decades of eclipse observations. Particular emphasis is placed on the discovery of the complexity of coronal structures, in particular at the source regions of the solar wind, directly connected to prominences. Complex structures include different manifestations of waves and plasma instabilities. Imaging in coronal emission lines yields the only diagnostic tool, known to date, for the empirical inference of the freeze-in distance of heavy ions. Imaging also enables the mapping of the electron temperature in the inner corona, and its changes in response to the passage of a coronal mass ejection (CME). Furthermore, spectroscopic observations reveal that cool prominence material associated with a CME, travels in tandem, unscathed, into interplanetary space. Multi-wavelength imaging and spectroscopy during total solar eclipses thus yield a treasure trove from the sources and acceleration regions of the solar wind, which beg continued exploitation in search of signatures of coronal heating and solar wind acceleration processes.