Total Solar Eclipse - 2020 Dec 14

On December 14, 2020, a total eclipse of the sun occurred. ( NASA , 2021;  Carlowicz  M, 2020). It was a memorable event, which we were able to observe from our own homes. In addition, this eclipse was visible in much of South America. 

Image. Total eclipse of the sun. Sun, Moon and Earth lined up. Image: ( Timeanddate.com , 2021b)

Eclipses are sporadic phenomena that occur when a perfect alignment occurs between the Sun, Moon, and Earth. This alignment is rare because the moon's orbit is inclined at an angle of 5 degrees to the Earth orbit. This type of phenomenon arouses interest in the population in addition to attracting tourism ( Araya-Pizarro , 2020).

Image. Lunar nodes where the Moon crosses the Earth's orbital plane. Image:  Timeanddate.com , 2021b

Eclipses are rarely repeated in the same place. For example, in Junín de los Andes, 6 eclipses have been visible in the last 2020 years

Image. Elaboration from data from  Nasa Eclipse , 2021

But eclipses also provide a rare opportunity that scientists take advantage of to conduct research in multiple scientific areas that could not be performed otherwise ( Gerasopoulos , et al, 2008). For example, the total eclipse of the sun of August 21, 2017 helped test predictive models of the solar corona ( Mikić , et al, 2018)

 Image . Prediction of the Sun’s corona during the August 21, 2017 total solar eclipse. Cooper Downs, Zoran Mikic, Predictive Science Inc.

 Image . Filtered photograph of the observed August 21, 2017 total solar eclipse. Alson Wong, Riverside Astronomical Society

The total eclipse of the sun of May 29, 1919 helped experimentally verify Einstein's theory of relativity. ( Dyson , et al, 1920).

Image. The curvature of light was demonstrated as it passed through the sun.  Classic history 

In a total eclipse of the Sun, the Moon crosses in front of the Sun casting its shadow on Earth for a few minutes. This causes alterations in the luminosity, wind temperature, pressure and chemistry of the atmosphere ( Aplin , et al., 2016;  Dodson , et al, 2019), pollutant movement ( Pakkattil , et al., 2020) with different response according to different ecosystems ( Wood , et al., 2019,  Penaloza-Murillo , et al., 2020).

 Image : The time-lapse video on December 14, GOES-16. Shadow of the eclipse over South America. NOAA

The Sun also emits low-energy cosmic rays, although most cosmic rays reach from multiple directions of space and even some pass-through Earth. Most of these particles are usually protons from other close enough galaxies or supernova explosions, which expel large amounts of charged particles. Some particles can be very energetic. When a particle reaches the atmosphere, it collides with others producing many secondary particles that share the same energy as the original primary particle. These primary particles also collide with air molecules producing billions of particles, some disintegrate rapidly, and others reach the Earth's surface. ( Benitez de Lugo , 2011;  CONICET , 2021;  Kaya, & Atakisi , 2021;  ITeDA , 2021;  Pierre Auger Observatory , 2021).

Image. Scheme of the cosmic ray “showers” on the Earth's surface. Background photo: Lake Tromen, its own source. Secondary cosmic ray cascade diagram ( Kaya, & Atakisi , 2021).

1. What changes occur on the Earth's surface during a total eclipse of the sun?

• 1.1. How much do luminosity, temperature, atmospheric pressure, winds and cosmic radiation change on the Earth's surface?

• 1.2. How much does cloud cover influence?

Image. Path of the eclipse and total and partial coverage. Base map ( Timeanddate.com  2021a).

Records were made in:

1) City of Junín de los Andes

2) Information was collected on the path of totality

Image. Junín de los Andes city and path of totality. Base map ( Timeanddate.com  2021a).

Equipment and websites used.

• a) GLOBE Visualization System,
• b) Weather station near the measurement site,
• c) cloud recording with GLOBE Observer app,
• d) maximum and minimum thermometers (left) and alcohol (right),
• e) GLOBE Observer Eclipse app,
• f ) PASCO temperature sensor,
• g) digital infrared thermometer,
• h) Phyphox app,
• i) Eclipse 2.0 app,
• j) Cosmic Watch cosmic ray detector and
• k) cosmic ray display and recording.

All measurements were made in the pre-eclipse periods, the eclipse day (December 14th) and post-eclipse Time: 11:30 at 3 pm - local time.

The path of the eclipse crossed areas with low population density.

 GLOBE Observer  measurements were concentrated in the area of totality in the localities near the Los Andes mountain range.

Data were taken from meteorological stations of the Servicio Meteorológico Nacional ( SMN , 2021), SIGA/INTA ( INTA , 2021) and the Wunderground Network ( Wunderground , 2021b). GOES 16 satellite images were also used for temperature and cloud cover data ( Modelo experimental WRF , 2021).

Results in Junín de los Andes

Temperature variation in Junín de los Andes on December 14, 2020.

Image. Total solar eclipse. Air temperature data in Junín de los Andes and nearby areas reported through the GLOBE Observer app. ( The GLOBE Program , 2021b)

Before eclipse

On December 13, during the recording hours, the cloud cover was 90-100% and almost at the end of the recording it was reduced by 25-50%. This caused the decrease in air temperature, which increased as cloud cover decreased.

Eclipse day

On December 14, the cloud cover was 10-25% and did not cover the sun. The decrease in air temperature of 5ºC was produced by the effect of the eclipse.

After eclipse

On December 15, no clouds were recorded, the air temperature increased progressively throughout the measurement period.

Image. Results of the registrations with the GLOBE Observer app on December 13, 14 and 15, 2020 in Junín de los Andes.

Before eclipse

The luminosity decreased due to the effect of cloud cover, influencing the decrease in air temperature.

The surface temperature also decreased but less than that of the air.

Soil temperature was not affected by the change in cloud cover.

Eclipse day

During totality a rapid decrease in luminosity is observed.

The surface temperature decreases rapidly coinciding with the luminosity, while the air temperature registers its minimum values a few minutes after totality.

Soil temperature was affected by the eclipse.

After eclipse

Small variations in luminosity were recorded due to the absence of clouds.

Air and surface temperatures increased progressively during the recording period.

Soil temperature had a small increase during the recording period.

Image. Luminosity and air, surface and soil temperatures in Junín de los Andes. The gray bar indicates the time of totality to compare the eclipse with the days before and after the eclipse.

Before eclipse

Wind speeds and gusts were low the day before the eclipse. The atmospheric pressure was stable. On the day of the eclipse, the atmospheric pressure was lower.

Eclipse day

Wind speeds ranged from 10 to 18 mph (meters per hour) but gusts were high especially after totality with maximums near 30 mph.

After eclipse

The day after the eclipse the atmospheric pressure was higher and the wind speed decreased. 

Image. Wind speed, maximum gusts and atmospheric pressure, in Junín de los Andes, recorded before, during and after the eclipse. The gray bar indicates the moment of totality. Nearby weather station data. ( Wunderground , 2021a).

Cosmic ray flux on the Earth's surface was stable during the recorded time. There are no differences due to the effect of the eclipse and neither in the days before and after the eclipse.

Image above. Cosmic ray flux in Junín de los Andes, recorded before, during and after the eclipse. The gray bar indicates the totality of the eclipse.

Image below. Comparison of cosmic ray flux before, during and after the eclipse in Junín de los Andes. Average values (left) and table with the variation from 13:03 to 13:09 local time. The cosmic ray flux during totality is pointed out.

Results in the path of totality

Image. Air temperature and cloud cover ( Modelo experimental WRF , 2021) 

The path of the eclipse was covered with clouds from 11 a.m. to 3 p.m. (local time).

In many localities it prevented the observation of the phenomenon or it was partially observed.

In the GOES-16 images, a decrease in temperature is observed with a minimum at 1:00 p.m. coinciding with the totality and then an increase in the following images.

Image. Air temperature and cloud cover ( Modelo experimental WRF , 2021) and the eclipse path ( Timeanddate.com , 2021a).

The air temperature decreased a few minutes after totality in the localities near the eclipse path. The difference in the decrease in temperature could be influenced by cloud cover, being less in the areas with greater coverage at 1:00 p.m. (local time)

Image. Terrain elevation profile on the path of the eclipse made with Google Earth. Graphs of air temperature in nearby locations during the eclipse. The lines indicate the time of the totality of the eclipse. Sources: Servicio Meteorológico Nacional ( SMN , 2021), EEA - Estación Meteorológica Automática SIGA ( INTA , 2021) and Wundergroud ( Wundergroud , 2021b).

In the city of Junín de los Andes, the eclipse influenced the decrease in luminosity, surface temperature and air temperature.

Luminosity and surface temperature decrease when totality occurs, while air temperature decreases a few minutes later.

Atmospheric pressure decreases and wind speed increases after totality with greater increase in gusts. But fluctuations in atmospheric pressure could be influenced by other variables

The ground temperature does not reflect any influence of the eclipse, possibly because the duration of totality at the measurement site was very short (1:02 minutes).

It was not possible to measure the influence of the cloud cover during the eclipse in Junín de los Andes because the clouds did not cover.

The cosmic ray flux did not change due to the eclipse, possibly because: 1) most of the cosmic rays that reach the surface come from sources other than the Sun, or 2) they come from the Sun, but the Moon does not stop them because its size is very small.

In the path of the eclipse, the GOES-16 images show the abundant cloud cover throughout the eclipse path, which in some locations was not possible to observe the phenomenon. This occurred in Chile and much of Argentina, it could only be observed in some localities ( The Washington Post , 2020).

The temperature decreased at the time of totality on the path of the eclipse.

Eclipses are rare phenomena that can be considered a natural experiment; therefore, it was an opportunity to know the effect of the Sun on the Earth's temperature. In a very short period of time it caused large changes in air and surface temperatures.

Thanks to measurements from different sources, it was possible to know the variations in the impact of the eclipse in different locations.

In addition to traditional data recording methods (weather stations, satellites, etc.), cell phone applications made it possible to collect data of value for science, providing the opportunity for society to participate as citizen scientists.

Due to the covid-19 pandemic, local governments established many restrictions to travel to the eclipse zone, limiting the amount of measurements and scientific investigations.

The latest eclipses generated public interest, and helped spread citizen science. In the future, it is recommended to carry out previous campaigns in the next eclipses in different parts of the world to better understand the meteorology of the eclipses.

Mentors work provided a lot of information about the eclipse and astronomy in general. The mentors also assisted in the selection of data and the processing of the same for the research.