Eclipse Day Research Articles

Impact of a solar eclipse on surface radiation and photovoltaic energy

We investigate the impact of annular solar eclipse (26 December 2019) on the surface radiation and photovoltaic (PV) energy generation observed at Gadanki (13.48° N, 79.18° E), located in southern peninsular India. Spectral and broadband irradiances are found to be sensitive to the solar obscuration, and follow the curvature resembling the fraction of non-obscured area of the Sun during the eclipse. Rapid changes are noticed in the spectral and broadband irradiances during the decreasing and increasing phases of solar obscuration. The diffuse fraction exhibits weak spectral dependence during the peak solar obscuration and under the influence of clouds. Although the deviation in the diffuse horizontal irradiance (DHI) at different wavelengths is highly sensitive, the deviations in the global horizontal irradiance (GHI) and direct normal irradiance (DNI) are found to be comparable among different wavelengths during the eclipse period. At peak obscuration, the reduction in both GHI and DNI shows an increasing trend from 414 nm to 671.2 nm. On the contrary, DHI decreases from 495.9 nm to 869 nm. Also, the deviation in broadband irradiances range between 72% and 98% with differing magnitudes of reduction at the peak obscuration. Apart from this, it is observed that the time of occurrence, strength of solar obscuration and prevailing sky conditions exhibit varying impact on the surface radiation components. The PV energy generated on the eclipse day is found to be reduced by 37% in comparison to that on a clear-sky day.

Global Positioning System Observations of Ionospheric Total Electron Content Variations During the 15th January 2010 and 21st June 2020 Solar Eclipse

AbstractThe dual‐frequency global positioning system (GPS) data acquired from the UNAVCO over different places of Nepal were processed to examine the eclipse‐triggered consequences on total electron content (TEC) in response to the annular solar eclipse of 15th January 2010 and 21st June 2020. These occasions were exceptional since they occurred during solar minimum, additionally as in a magnetically quiet period. The eclipse phase coincided with the peak ionization‐time at the equatorial and low latitude regions. The solar eclipse of 21st June 2020 was an annular solar eclipse with a magnitude of 0.994. Nepal has witnessed a partial eclipse, starting at ∼10:53 NST (05:08 UT), reached the maximum at ∼12:40 NST (6:55 UT), and ended at ∼14:24 NST (8:39 UT) with the total duration of 3 h and 31 min. The annular solar eclipse of 15th January 2010 had the magnitude of 0.919 and Nepal has witnessed a partial eclipse starting at ∼12:24 NST (6:39 UT), reached the maximum at ∼14:10 NST (8:25 UT), and ended at ∼15:40 NST (9:55 UT). The eclipse effect occurs as a trough‐like depression in the curve of TEC at all the GPS stations indicates the effect of sudden attenuation of solar extreme ultra‐violet irradiation on decayed electron content in the ionosphere over the region. Moreover, the extent of the exhaustion in ionospheric TEC was studied by comparing the eclipse day TEC with mean diurnal ionospheric TEC of five quietest days of the month to investigate the eclipse effect on the electron density of the ionosphere over the stations. The study additionally reveals that the measure of the decrease in vertical value of total electron content is proportional to the obscuration of the lunar disc, that is closely associated with the electron production via the photoionization process. Observing the values of TEC during the eclipse day and comparing it with other quiet days, our study showed an apparent variation during the time of the eclipse, which agrees with previous studies on ionospheric responses to the eclipse as well as theoretical assumptions.

Bird Behaviour during the June 21, 2020 Solar Eclipse

Background: A solar eclipse is an occasional natural phenomenon that can alter the physical and biological processes of organisms. On 21 June 2020 a unique opportunity was offered to evaluate how birds change their behaviour during an eclipse. Bird behaviour was categorised using a scan-sampling technique before, during and after the solar eclipse, and at a different time of eclipse day. Results: Before the eclipse major activity categories were moving (52.45%), foraging (40.20%), and courtship (2.94%) respectively, but there were no roosting/resting observations at this time. These behaviours were much reduced during the eclipse, while roosting accounted for 14.6% of behaviour. When the eclipse began at 06:50, their calling and flying increased, and singing decreased. At maximum eclipse (07:20h), there was a profound decrease in calling, singing, foraging and moving, and courtship; while washing and floating were not observed. After the eclipse, most time was spent foraging (36.3%), followed by moving (flying), with roosting reduced to 2.4%. Conclusions: Clear and radical behavioural changes were observed when the eclipse was started and maximum. Responses of birds to the environmental factor changes associated with the solar eclipse might be the root cause of observed unusual behavioural change.

Decrement of secondary gamma radiation flux during lunar eclipse June 16, 2011

The lunar eclipse at Udaipur (27◦ 43’ 12.00” N, 75◦ 28’ 48.01” E), India was experimentally observed on June16, 2011 using ground based NaI (Tl) Scintillation detector. We interpret such decrement of secondary gamma radiation flux (SGRF) on the basis of obstruction effect produced by Earth and Moon during lunar eclipse on radiation. Objective: To observe secondary gamma radiation flux during lunar eclipse day on comparison to pre and post eclipse days. Methods: For this experimental study we used ground based NaI (Tl) Scintillation detector. The data files were stored in computer for thirty minutes duration from 1.00 AM to 2.00 AM (Indian Time) on pre-eclipse normal days June 14 and 15, 2011 as well as on post eclipse normal day June 17 and also on eclipse day June 16, 2011. Finding: The analyzed data reveal significant decrement of secondary gamma radiation flux (SGRF) on lunar eclipse day about 6% on comparison to pre and post lunar eclipse days. Novelty: In this experimental study first time we reported about 6% decrement of secondary gamma radiation flux on lunar eclipse day on comparison to pre and post lunar eclipse days. Keywords: Lunar eclipse; cosmic radiation; reflected solar radiation; secondary gamma radiation; obstruction effect by Earth and Moon

A study on TEC reduction during the tail phase of the 21st June 2020 annular solar eclipse

Ionospheric response during the annular solar eclipse of June 21, 2020, has been examined in terms of the Total Electron Content (TEC) obtained from six Global Positioning System (GPS) receivers positioned in the Chinese-Taiwanese region. We have shown TEC variation from satellites designated by PRNs (Pseudo-Random Noise code) 2, 6, and 19. PRN wise TEC trend was observed to depend upon satellite-pass trajectory to the receiver's location during the eclipse period. A time lag of ~15–30 min is also observed in maximum TEC decrement after the phase of maximum eclipse. Instead of the percentage of eclipse magnitude, a reduction in TEC is seen more for the station for which the orbital track of respective satellites was in closer view relative to receivers for more hours of eclipse window. Additionally, the eclipse day diurnal variations are compared with the pre-eclipse day TEC trend, and observed results show a clear decrease in TEC values at all chosen stations after the eclipse onset then reached the lowest value a few minutes afterward the maximum eclipse phase.

Ionospheric total electron content response to annular solar eclipse on June 21, 2020

The effects of physical events on the ionosphere structure is an important field of study, especially for navigation and radio communication. The paper presents the spatio-temporal ionospheric TEC response to the recent annular solar eclipse on June 21, 2020, which spans across two continents, Africa and Asia, and 14 countries. This eclipse took place on the same day as the June Solstice. The Global Navigation Satellite System (GNSS) based TEC data of the Global Ionosphere Maps (GIMs), 9 International GNSS Service (IGS) stations and FORMOSAT-7/COSMIC-2 (F7/C2) were utilized to analyze TEC response during the eclipse. The phases of the TEC time series were determined by taking the difference of the observed TEC values on eclipse day from the previous 5-day median TEC values. The results showed clear depletions in the TEC time series on June 21. These decreases were between 1 and 9 TECU (15–60%) depending on the location of IGS stations. The depletions are relatively higher at the stations close to the path of annular eclipse than those farther away. Furthermore, a reduction of about −10 TECU in the form of an equatorial plasma bubble (EPB) was observed in GIMs at ~20° away from the equator towards northpole, between 08:00–11:00 UT where its maximum phase is located in southeast Japan. Additionally, an overall depletion of ~10% was observed in F7/C2 derived TEC at an altitude of 240 km (hmF2) in all regions affected by the solar eclipse, whereas, significant TEC fluctuations between the altitudes of 100 km − 140 km were analyzed using the Savitzky-Golay smoothing filter. To prove TEC depletions are not caused by space weather, the variation of the sunspot number (SSN), solar wind (VSW), disturbance storm-time (Dst), and Kp indices were investigated from 16th to 22nd June. The quiet space weather before and during the solar eclipse proved that the observed depletions in the TEC time series and profiles were caused by the annular solar eclipse.

Perturbations of atmospheric surface layer characteristics during the annular solar eclipse on 26 December 2019 over a semi-arid region Anantapur in southern India

The Annular Solar Eclipse (ASE) occurred on December 26, 2019, which was visible at most of the South Indian subcontinents with greater than 80% obscurity, particularly during the morning hours, and it played a crucial role in the atmospheric dynamics. For the first time, the ground-based measurements have used to investigate the fluctuations of air temperature, relative humidity, atmospheric pressure, wind speed and direction, UV-A radiation, and turbulence parameters on solar eclipse day over a semi-arid region, Anantapur, in Southern India. The Surface Layer (SL) meteorological parameters have abruptly changed on eclipse day (December 26, 2019) as compared to the control day (December 27, 2019). During eclipse day, the near-surface air temperature was significantly decreased (1.12 °C), and relative humidity increased (14.63%) after 60 min of the beginning of the eclipse, which mainly due to cooling the surface. The atmospheric pressure has reduced by 0.9 hPa during the eclipse period, and the winds speed also reduced to 0.92 ms−1 due to the stabilization of Atmospheric Boundary Layer (ABL) and cooling in the SL. The turbulence parameters, including those are Sensible Heat Flux (SHF), Momentum Flux (MF), and Turbulent Kinetic Energy (TKE) have also reduced from 99.37 to 0.91 Wm-2, 0.38 to 0.03 Nm−2, and 1.47 to 0.37 m2s-2, respectively during the eclipse day, which mainly due to eclipse cooling effect diminishing the turbulence in Atmospheric Surface Layer (ASL). The lowest values (0.18 ms−1) of friction velocity were observed during the eclipse day, and the Monin–Obukhov stability parameter showed a significant variation in the atmospheric from weakly unstable to neutral conditions during the eclipse day. The vertical wind speed showed downdrafts during the eclipse and even after the eclipse due to subsidence of air. The investigation revealed that the ABL dynamic process and turbulence processes are affected due to cut off of solar radiation and make the SL cooling.

Trace pollutant fluctuations observed in Calicut city, India, during the annular solar eclipse on 26 December 2019

Atmospheric boundary layer perturbations were monitored during an annular solar eclipse event on December 26, 2019 to understand its impact on the meteorological parameters (temperature, relative humidity, wind speed, and wind direction) and trace gas concentrations (O3, NO, NO2, NH3, CO, and HONO) at Calicut (11.24° N, 75.78° E), a tropical city along the coastal belt of Arabian Sea in the southwest coast of Indian Subcontinent. The solar eclipse started at 8:05 IST (5.5 h ahead of UTC), reached to a maximum coverage of 93.28% at 09:27 IST and ends at 11:07 IST. Eclipse day data were compared with the nearby days' records from this site. The rapid fall in the irradiance caused cooling of the surface air by ~0.7 °C and weakened the wind speed, whereas the relative humidity, as expected, was increased by 5.1%. A gradual decrease in the surface O3 along with the reduction in solar irradiance was observed during the eclipse, due to the decreased efficiency in the photochemical formation of ozone. There was a decrease in mixing ratios of NO2 during the eclipse period, which was a result of the fall in ozone concentrations. No significant variation was observed in HONO levels, whereas variations in concentrations of NO and NH3 have followed the night time chemistry. The NO3 radical mixing ratios were below the detection limit during the eclipse event.

Demarcation of solar cycle 24 and characterization of ionospheric GPS-TEC towards the western part of India

We analyze the behavior of Total Electron Content (TEC) in the Ionosphere using the GPS data between 2009 and 2017 towards the western part of India. The GPS data used in the present study consists of 22 Continuously Operating Reference Sites (CORS), bounded between 200- 240 N Latitude and 680 - 740 E Longitude. All the GPS data used in the study are generated using the Leica 1200 receivers and AX1202GG antennas with a sampling interval of 0.03 Hz. The TEC value of this study is calculated using the L-band GPS frequencies L1 (1575.42 MHz) and L2 (1227.36 MHz). The results reveal maximum TEC values during the daytime (03.30–04.30 IST) for all the years and a maximum of 120 TECu (TEC unit) was observed during the year 2014. The reflection of seasonal variation was visible in the time-series of TEC in all the years, while E season (March, April, September and October) observed maximum TEC values in all the stations. The mean monthly TEC values of the present study illustrate the solar cycle-24 and the coefficient of correlation (r2) of 0.74 indicates a close relationship between the sunspot number and TEC values. A fall of 35% TECu was observed on the annular solar eclipse day on 15 January 2010.

Remote sensing ionospheric variations due to total solar eclipse, using GNSS observations

For years great interest has been taken in the effects of physical phenomena on ionosphere structure. A total solar eclipse was visible in North America on August 21st, 2017. This event offered a great opportunity for remote sensing the ionospheric behavior under the eclipse condition. In this study we investigated the effects of total solar eclipse on variations of Total Electron Content (TEC), and consequently deviations on regional models of Vertical TEC (VTEC), as well as variations in ionospheric scintillation occurrence. Although variations of TEC due to total solar eclipse are studied thoroughly by many authors, but the effect of solar eclipse on ionospheric scintillation has never been considered before. Our study is based on measurements from a high-rate GPS network over North America on the day of eclipse, a day before and after its occurrence, on the other hand, GPS measurements from ground-based stations on similar days were used to model TEC on the day of event, and also one day before and after it. The results of this study demonstrate that solar eclipse reduced scintillation occurrence at the totality region up to 28 percent and TEC values showed a decrease of maximum 7 TECU. Considering TEC models, our study showed apparent variations in the regional models, which confirms previous studies on ionospheric responses to eclipse as well as theoretical assumptions.

Ionospheric responses to the 21 August 2017 great American solar eclipse – A multi-instrument study

Herein, we report on the ionospheric responses to a total solar eclipse that occurred on 21 August 2017 over the US region. Ground-based GPS total electron content (TEC) data along with ground-based measurements (Millstone Hill Observatory (MHO) and digital ionosondes) and space-based measurements (COSMIC radio occultation (RO) technique) allowed us to identify eclipse-associated ionospheric responses. TEC data at ~20°, ~30°, and ~40°N latitudes from the west to east longitudes show not only considerable depression but also wave-like characteristics in TEC both in the path of totality and away from it, exclusively on the day of eclipse. Interestingly, the observed depressions are associated with lesser (higher) magnitudes at stations over which the solar obscuration percentage was meager (significant), a clear indication of bow-wave-like features. The MHO observes a 30% reduction in F2-layer electron densities between 180 and 220 km on eclipse day. Ionosonde-scaled parameters over Boulder (40.4°N, 100°E) and Austin (30.4°N, 94.4°E) show a significant decrease in critical frequencies while an altitude elevation is seen in the virtual heights of the F-layer only during the eclipse day and that decreases are associated with wave-like signatures, which could be attributed to eclipse-generated waves. The estimated vertical electron density profile from the COSMIC RO-based technique shows a maximum depletion of 40%. Relatively intense and moderate depths of TEC depression, considerable reductions in the F2-layer electron densities measured by the MHO and COSMIC RO-measured densities at the F2-layer peak, and elevations in virtual heights and reduction in the critical frequencies measured by ionosondes during the eclipse day could be due to the eclipse-induced dynamical effects such as gravity waves (GWs) and their associated electro-dynamical effects (modification of ionospheric electric fields due to GWs).

Perturbations in Earth’s Atmosphere over An Indian Region during the Total Solar Eclipse on 22 July 2009

During a total solar eclipse (TSE) on 22 July 2009, atmospheric perturbations were monitored from the surface to thermosphere to understand TSE’s impact on the meteorological (temperature, relative humidity, wind speed, and wind direction) and chemical (O3 and NOx) parameters around Kadapa (14.28°N, 78.42°E), a tropical semi-arid region of India. For this purpose, an experiment was conducted at Yogi Vemana University Campus, Kadapa, India, to measure the temperature, wind speed, wind direction, and concentrations of ozone (O3), NO, NO2, and NOx by using the automatic weather station (AWS) and O3 analyzer. On the eclipse day (22 July 2009), the surface observations at Kadapa showed a reduction in temperature (about 1.1°C) because of the solar insulation. Comparison of the thermal, dynamical (wind), and chemical parameters on the TSE day with control days [preceding (21 July 2009) and succeeding (23 July 2009) the TSE] illustrated the influence of solar eclipse. During the eclipse period, the O3 mixing ratio decreased, while NO2 and NOx increased; however, NO remained unchanged. In addition, radio occultation (RO) temperature profiles from Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/Formosat Satellite Mission (FORMOSAT-3) and Thermosphere, Ionosphere, and Mesosphere Energetics and Dynamics (TIMED) satellites were utilized to understand the impact of TSE on dynamics of the middle and upper atmosphere from tropopause to the thermosphere. High vertical resolution COSMIC observations revealed that during the solar eclipse, tropopause was cooler with twin peaks (double tropopause). The lower thermosphere between 110 and 130 km became warmer during the TSE, which might be caused by the dynamical response of the atmosphere in this region to the solar eclipse. The experimental data have provided very fine-scale variations of the atmospheric parameters both in time and height and also constituted a new set of results on TSE for further research.

Observation and characterization of traveling ionospheric disturbances induced by solar eclipse of 20 March 2015 using incoherent scatter radars and GPS networks

We present the results of a comprehensive study of traveling ionospheric disturbances (TIDs) occurring over Europe during the total solar eclipse of 20 March 2015. For detection of wave structures and estimation of TID parameters, two remote sensing techniques were combined: incoherent scatter (IS) radars and European and Finnish dense GPS receiver networks. Similar procedures were applied for processing both IS and GPS data. We developed a new method enabling to analyze TEC data separately in the temporal and spatial domain. For the first time, we produced maps of band-pass filtered TEC variations and reported both large- and medium-scale prevailing TIDs observed during this solar eclipse, both having similar periods of about 50 – 60 min. The downward phase progression indicates that TIDs were induced by atmospheric gravity waves generated at lower altitudes. The variations in IS power attained peak relative amplitudes of 0.22 (22%) at 220 km over Tromsø and of 0.17 (17%) at 200 km over Kharkiv. The vertical phase velocity was about 57 m/s over Tromsø. It increased from 25 to 170 m/s over Kharkiv with altitude increasing from 120 to 310 km. Over Western Europe, large-scale TIDs (LSTIDs) had prevailing north-east direction over the region from 45°to 50°N and 2°W to 8°E. Here, their average horizontal phase velocity Vm was 803±281m∕s and the absolute amplitudes of TEC variations usually do not exceed 0.17 TECU. For this region, we found strong differences in LSTID propagation azimuth between the solar eclipse day and the two adjacent days of 19 and 21 March 2015, used as reference. This most likely indicates that these LSTIDs were directly caused by the solar eclipse through local heating/cooling processes occurring during the passing of the Moon penumbra. Over another region, limited by 44°–50°N and 13°–19°E, the LSTIDs had south-east propagation. Over Finland, the LSTIDs also propagated southeastward having Vm=774±202m∕s and TEC amplitudes up to 0.6 TECU. A possible evidence of LSTID generation at high latitudes indirectly by this solar eclipse through an excitation of slow magnetosonic waves was experimentally detected. Medium-scale TIDs (MSTIDs) propagated southeastward over both regions having Vm values of 144±54m∕s over Western Europe and of 104±43m∕s over Finland. Over Northern Europe, the maximum MSTID amplitudes were greater by a factor of 5 compared to those over Western Europe and reached 0.4 TECU. We did not detect a clear difference in MSTID propagation between solar eclipse and reference days. The IS and GPS results are in consistency with each other. The detected TID parameters of predominant periods, relative amplitudes, altitude range and MSTID horizontal propagation direction generally correspond to the results of other studies.

Hell’s Bells: Notes on Tone

Hell’s Bells: Notes on Tone Mary Ruefle (bio) In early spring, in Croatia, old men and young men get up in the dark and get dressed in sheepskins, they don huge sheepskin masks and around their waists they tie giant sheep-bells. They proceed to parade through remote villages, making a racket. They are the Halubian bell-ringers, and their job is to ward off the evil spirits of winter so that the benevolent spirits of spring can arrive safely. This is their warm welcome, a ritual no less bizarre than writing a poem. Here we are in early spring. We have survived the winter. Some of us; those who have not are not, strictly speaking, here. Sooner than you think, it will be summer. Last summer I went back to a state park I had not visited in twenty-five years; I wanted, suddenly, to swim in the lake which is its centerpiece. And so I went, but left after fifteen minutes, without swimming, though I sat on a towel in the grass staring at the lake. Something was missing. It took me those fifteen minutes to figure it out — the old concession shack was no more, it had been shut down. And though I loved the sound of splashing water and airborne shouts, what I loved most [End Page 206] was the sound of the little bell that rang every time a kid went into or came out of the concession shack, opening or closing its screen door. Kids in wet suits who went in to buy Creamsicles and came out licking them as the orange and white goo dripped. The bell! The bell! I missed the constant sound of that dinky bell, and my heart was broken. The sound of that bell was gone forever. You see, I am not really interested in tone; I am interested in bells. Here’s something intriguing: when I asked poets under the age of fifty what tone was (in a poem) they all said more or less it was the contextual inflection or attitude that helped determine meaning in a poem. When I asked poets over the age of fifty, they all said more or less that tone was a presence that was helplessly itself. I am not pitting these groups against each other, for both answers are relevant and meaningful, but being over fifty I do gravitate toward the helpless presence of a voice. At the same time, there are instances of the other I find riveting. On the day of the total eclipse of the sun in August 2017, a group of people in Oregon standing under the direct path of the solar event cheered and shouted during the minutes of totality. Cheered and shouted as if it were the stroke of midnight on New Year’s Eve. A group of people in Idaho, witnessing the same event, went dead silent in unison. I take these as two tones in response to the identical subject. The event was the subject, and the response was the tone. What would you have done? To which group do you belong? One older poet I asked about tone said, “Tone? My inner ear senses it, it’s just a feeling. There are a lot of writers I can’t read because I don’t yet have a sense of their tone. It’s not a criticism, it just means I don’t have the immediate affinity I have with someone like, say, Vallejo. And he’s one among a hundred.” [End Page 207] What is Vallejo’s tone, I asked, and he said, “I’ve never tried to put it into words. It’s in my ear. I used to say about Vallejo that I felt the poem was handed to me on a silver platter — it felt, sounded like a gift. With other writers, I sometimes feel like I am supposed to give them something. I know I’m not, but it can feel that way.” Does that have to do with the poet, or with you, I asked. “It’s a two-way street. An example for me is Borges. For some reason, I’m not there yet...

'The sun without a permit': Serbian solar politics, informational risk cascades, and the Great Disappearing Act of August 1999.

In the summer of 1999, the Serbian Ministry of Health issued a public health warning about the environmental risks associated with the total solar eclipse to took place on 11 August. The warning contained a list of phantom symptoms unknown to medical profession. Some of these included severe itching, hypertension, cardiac palpitation and frequent urination. Despite the warning's patent absurdity, the Serbian public widely observed it by seeking indoor and underground shelter from the lunar shadow, participating in what I term a 'great public disappearing act'. By contrast, the rest of Europe and the Middle East embraced the event as a public spectacle, with millions thronging the streets and observation posts. This paper raises two key questions: Why did the Serbian government issue the odd warning? And why did the Serbian public observe it? In contrast to the conventional readings of the event as a compound effect of a political manipulation and a lack of public scientific education, I argue that the public behavior on the eclipse day was a meaningful response to the social, political and environmental circumstances in the worn-torn Serbia. Using insights from the social amplification of risk framework, I demonstrate that the great disappearing act was a paradigmatic example of herd behavior governed by the media-driven informational cascades. I further argue that the actors involved in the production and reproduction of phantom ecliptic risks - doctors, journalists, government officials, ordinary citizens - jointly enhanced their plausibility in a way that eventually eliminated the possibility of any behavior not mediated by the cascading processes of risk production.

Shining light on sky cover during a total solar eclipse

Sky cover is a unique parameter because its quantification is subject to the perspective of the observer or characteristics of the observing instrumentation. Forecasting sky cover provided a professional challenge to operational meteorologists seeking to offer a refined forecast beyond numerical weather prediction guidance along the path of totality resulting from a solar eclipse traversing North America on August 21, 2017. A routine analysis with which to monitor subtle trends in sky cover and compare sky cover forecasts is also not widely available. This contribution reviews 1-h gridded forecasts of sky cover from the United States National Weather Service (NWS) on the eclipse day and compares them with hourly satellite and surface sky observations for an area of interest over the southeastern United States. An inconsistency between the real-time mesoscale analysis (RTMA) and the NWS National Digital Forecast Database is revealed during the eclipse totality. A satellite-to-satellite comparison of the adjusted average cloud top emissivity over this same area reveals how resolution and algorithm improvements to next-generation satellite imagers may alter the RTMA of total cloud cover in the latest era of Geostationary Operational Environmental Satellites (GOES), starting with the GOES-16 Advanced Baseline Imager.

Geomagnetic field variations observed by INTERMAGNET during 4 total solar eclipses

We investigate variations of the geomagnetic field observed by INTERMAGNET geomagnetic observatories over which the totality path passed during a total solar eclipse. As a result, we have presented results of examining the geomagnetic field data observed by 6 geomagnetic observatories during the 4 total solar eclipses (11 August 1999, 1 August 2008, 11 July 2010, and 20 March 2015). These total solar eclipses are the only total solar eclipse, since 1991 when the INTERMAGNET began to work, during which the umbra of the Moon swept an INTERMAGNET geomagnetic observatory and simultaneously variations of the geomagnetic field are recorded at the geomagnetic observatory. We have confirmed previous reports that, at least on average, during the solar eclipse characteristic increase of Y component of the geomagnetic field Y and decreases of X,Z and F are conspicuous. Interestingly, we have noted that variations of X,Y,Z and F observed during the total solar eclipse at Isla de Pascua Mataveri (Easter Island) in Chile (IPM) in the southern hemisphere show distinct decrease of Y and increases of X and Z on the contrary. We have found, however, that variations of X,Y,Z and F observed at Hornsund in Norway (HRN) at 77°N in latitude seem to be dominated by other geomagnetic occurrence since the solar activity is near maximum, and the geomagnetic field is disturbed on the day of eclipse. We further discuss a possibility of exploring an effect of the solar eclipse on the amplitude of harmonic components of the geomagnetic field using the wavelet analysis technique, which has revealed suppression in the amplitude during the middle of a solar eclipse. Finally, we conclude by discussing implications of what we have found.

Effect of a total solar eclipse on the surface crowding of zooplankton in a freshwater lake ecosystem

Zooplankton surface crowding in a freshwater lake ecosystem during a total solar eclipse (maximum eclipse at 06:28:43 Indian Standard Time, 22 July 2009) was studied in relation to ambient physicochemical conditions and compared with the crowding that occurred during pre- and post-eclipse days. Rapid light attenuation on the eclipse day led to changes in zooplankton surface crowding, which manifested as alterations to community structure and statistical parameters. Zooplankton diversity and density varied depending on the day (either the pre-eclipse day, the eclipse day, or the post-eclipse day) and the sampling time considered. A total of 20 zooplankton species were recorded during the study. On the day of the eclipse, the highest zooplankton density in the surface water was recorded just after the end of totality at 06:30 IST. The populations of two adult cladoceran species (Alona rectangula rectangula and Chydorus sphaericus) were particularly prominent in the zooplankton, whereas rotifers were almost absent from the surface water during the eclipse. Rather than decreasing, the primary production of the phytoplankton increased on the day of the TSE compared to that seen on the control days. Comparatively high Lindeman’s efficiency values were observed during the eclipse, indicating particularly efficient utilization of photons in photosynthesis.

Statistical analysis of geomagnetic field variations during solar eclipses

We investigate the geomagnetic field variations recorded by INTERMAGNET geomagnetic observatories, which are observed while the Moon’s umbra or penumbra passed over them during a solar eclipse event. Though it is generally considered that the geomagnetic field can be modulated during solar eclipses, the effect of the solar eclipse on the observed geomagnetic field has proved subtle to be detected. Instead of exploring the geomagnetic field as a case study, we analyze 207 geomagnetic manifestations acquired by 100 geomagnetic observatories during 39 solar eclipses occurring from 1991 to 2016. As a result of examining a pattern of the geomagnetic field variation on average, we confirm that the effect can be seen over an interval of 180 min centered at the time of maximum eclipse on a site of a geomagnetic observatory. That is, demonstrate an increase in the Y component of the geomagnetic field and decreases in the X component and the total strength of the geomagnetic field. We also find that the effect can be overwhelmed, depending more sensitively on the level of daily geomagnetic events than on the level of solar activity and/or the phase of solar cycle. We have demonstrated it by dividing the whole data set into subsets based on parameters of the geomagnetic field, solar activity, and solar eclipses. It is suggested, therefore, that an evidence of the solar eclipse effect can be revealed even at the solar maximum, as long as the day of the solar eclipse is magnetically quiet.

Contrasting behavior of slow and fast photoreactive gases during the August 21, 2017, solar eclipse

The total solar eclipse on August 21, 2017, provided a rare opportunity to observe and test our understanding of atmospheric dynamics and photochemical dependency on solar irradiance. Here, we utilize observations from the continuous monitoring of both slow and fast photochemically reacting trace gases near Boulder, Colorado, for evaluating the unique dynamic and photochemical forcings on the eclipse day. The monitoring station saw a 93% solar obstruction during the peak of the eclipse. Eclipse day data are contrasted with the full month’s record from this site. The loss of irradiance caused cooling of the surface air by ~3°C, and weakened convective and turbulent mixing. This resulted in a buildup of slow photoreactive gases (methane, short-chain non-methane hydrocarbons), as well as total nitrogen oxides (the sum of nitric oxide (NO) + nitrogen dioxide (NO2)) in the surface layer. In contrast, ozone (O3) declined by ~15 ppb during the first phase of the eclipse compared to median August diurnal mixing ratios. Similar O3 signatures were observed at a series of network stations along the Northern Colorado Front Range. With the loss of irradiance, the initial ratio of NO/(NO + NO2) of ~0.2 dropped steadily, bottoming out at <0.01, but rebounded to approximately two times above August median levels for this time of day towards the end of the eclipse. Above average O3 enhancements were seen in the afternoon hours following the eclipse at this and a series of other nearby surface O3 monitoring sites. The contrasting behavior of these slow and fast photoreactive gases, and comparison with other published eclipse data, allow characterizing these responses as more typical for an urban/polluted environment.