Solar Eclipse and Its Effects on Atmospheric Dynamics

Welcome to my blog wonderful Steemians. In furtherance of my previous post, I will be discussing solar eclipse and why it is important we understand it. These form the basis for my research as I will begin to review the link between this two vis: The ionosphere and eclipse events. Why is it important?


A solar eclipse happens on an average of once in every 2 years at different locations on the Earth, and its impact on the composition and dynamics of the atmosphere cannot be ignored. Remember the ionosphere (a part of the upper atmosphere) contains charged ions which aid communication? Yes, the dynamics and composition of the ionosphere are affected by various naturally occurring phenomenon, such as geomagnetic storm and solar eclipse. Let’s talk about eclipse now.

WHAT IS SOLAR ECLIPSE?

A solar eclipse is a complete or partial blockage of the rays of sunlight from reaching the Earth surface. Although solar eclipse occurs as frequently as stated, only a fraction of it is actually seen on land because the Earth is vastly composed of water. This is to say we can only observe, if at all, a limited number of solar eclipses and for a short period of time.

CELESTIAL COINCIDENCE

_{[image credits: Flickr: under the Creative Commons Attribution 2.0 Generic]}


Solar eclipse involves three celestial bodies which are the sun, the moon, and our planet Earth. Solar eclipses occur as a result of the moon moving in between the Earth and the Sun, completely or partially blocking the Sun from ‘smiling’ upon the Earth.

When will an eclipse occur?

If you go online to search for dates when an eclipse will occur, you will notice that you can find the timetable for the next couple of years. This is possible because the orbit of the Earth and the moon can be predicted. Scientist can, with greater accuracy predict when the moon will be between the Earth and the Sun during the course of its orbit around the Earth.

The sun is at the center of our solar system while the moon is revolving around the Earth. The moon is Earth’s natural satellite and is not luminous (does not produce its own light). A solar eclipse occurs when the Sun, moon and the earth align in perfect or nearly perfect syzygy, with the moon at the center. This is supposed to happen at least once in every month (Lunar month or new moon) right? How come we don’t see an eclipse every month since we have a new moon as frequent as that?

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This is because, for eclipse to occur, the new moon has to be near what is called a lunar node (a point in which the moon’s orbital path coincide with the Earth’s orbital plane around the sun). Lunar node occurs because the moon’s orbit is tilted a few degree north or south (approximately 5°) with respect to the Earth. Consequently, the moon casts two shadows on the Earth. The first one is a small darker shadow which is called the umbra. The second one is a bigger shadow, not as dark as the umbra, called the penumbra.
The Sun must also be close enough to a lunar node so it can align to form a perfect or near-perfect coplanar (lie on the same plane) with the Moon and Earth. This configuration happens in about 6-month interval and can last for an average of 34.5 days. Eclipse events can only take place during this time.

Will eclipse continue to happen forever?
The moon moves away from the Earth yearly at about 1.5 inches. Therefore, it is predicted that in about a billion years from now, the moon will be too far away and we won’t be able to see eclipse as they occur anymore. This is because as the moon moves farther away from the earth, the distance between the sun and the moon become apparently evident. So the moon will not be able to completely cover the Sun which is much bigger than it.

TYPES OF SOLAR ECLIPSE

Solar eclipses are divided into four. They are:

Total eclipse
Partial eclipse
Annular eclipse
Hybrid eclipse

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Total eclipse is the most remarkable of all the eclipses. It occurs when the moon completely blocks the sun, casting its shadow on it such that the part of the Earth which is supposed to receive sunlight at that time is in total darkness for the duration of this eclipse. This can only be seen by region on the earth that falls within the umbra (places where the moon is closest to the Earth) shadow at the particular time. This eclipse also creates an imaginary line called the path of totality. Regions which fall under the penumbra shadow at this time only see the second type of eclipse called a partial eclipse. This implies that outside the path of totality, the moon does not totally block the sun and light is still received.

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The third type of eclipse is called an annular eclipse. This occurs when the moon passes in front of the sun, and appear to be too small to fully cover the sun. Therefore, the outer edges of the sun can be seen. This produces what appears to be a ring of fire in the sky. The moon's orbit is elliptical. This implies that there are times when the moon can be observed to be closer to the Earth and at other times farther away.

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The fourth and last type of eclipse is the hybrid eclipse. Just as the name hybrid, it is a combination of total eclipse and annular eclipse. This happens when the position of the moon between the Sun and the Earth superbly balanced, such that the curvature of the Earth plays an important role. The moon will then appear to be farther away from some parts of the Earth and this part experiences an annular eclipse. It will also be very close to some other part which will result in total eclipse.

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PRECAUTION DURING ECLIPSE

While an eclipse event is a phenomenal beauty to behold, however, you should avoid looking directly at the sun when it happens. This could cause permanent damage to the eye. You are advised to put on certified eclipse-watching glasses, which are darker than normal sunglasses. These glasses are adequately shielded to provide eye protection during an eclipse. Also, the beautiful eclipse can be viewed using a pinhole viewer.

Want to make one?

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Simply make around small hole on a piece of cardboard. Then hold the cardboard up to the sun such that the sun’s image can be projected onto a flat surface. Ensure that you only look at the flat surface and not directly into the cardboard. There you have it! You can view this remarkable event without collateral damage.

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Before the moon completely covers the sun, the rays of light will still be seen through the low line valleys at the edges of the moon. These remaining lines of rays through the edges are known as Baily’s beads. These are several of diamond rings that break up into ‘beads’ created before a single beam remains, as the moon completely blocks the sun. These Baily’s beads will begin to disappear one by one. Then, a single beam that remains before experiencing totality is called diamond ring. Once this occurs, it is a signal that you are about to experience total darkness.

When the diamond ring disappears and the moon completely covers the sun, the view through the eclipse glasses or the pinhole eclipse viewer becomes peach black. This means that no rays from the sun are reaching the eyes and the eclipse glasses can be taken off to watch the beautiful view. Before the moon begins to move away again, do ensure that the glasses are worn and all necessary precautions are taken to prevent the rays of the sun from entering into the eye. Any rays finding its way into your eye, even for a flint second can cause serious damage to the eye. Even though eclipse can last for hours, totality can only last for about 3 minutes on the average.

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THE SUN IS OBSCURE, SOME THINGS BECOMES MORE VISIBLE

During a total eclipse, the outer surface of the Sun known as the corona becomes visible. This provides an opportunity for scientist to observe and study the corona in fine details. Although the corona can be studied from outer space through an instrument called coronagraph. The coronagraph produces artificial eclipses by using a metal block to obscure the Sun, making the corona visible for scientific observation. However, there are still some regions of the corona that are only visible during a total eclipse. This is in fact due to diffraction of light which happens as a result of the coronagraph blocking not only the Sun's surface but also a larger part of the corona so as to get a sharp and clearly defined image. However, diffraction is not an issue during a total eclipse because the moon is far away from the Earth (about 230,000 miles), so scientists are able to observe the corona in details. Stars and planets also become visible during eclipse events. A solar eclipse also presents an opportunity to study the effect of the Sun on the upper atmosphere.

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EFFECTS OF ECLIPSE

Eclipse events have various effects on man, plants, and our planet. Even other animal respond to this natural stimulus.
Many living things modify their behavior during a total solar eclipse. Sunbirds may stop singing, crickets may stop chirping and flowers may start closing up in response to the eclipse.

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EFFECT ON ATMOSPHERIC DYNAMICS

Space Weather
The sun is an active star which produces streams of fast-moving plasma and magnetic field. The magnetic field interacts with the Earth’s magnetic field and when intense, could have an impact on satellite and communication. Although this eruption can be track and prediction of when it will happen can be known by studying the corona, an opportunity adequately presented more during a total solar eclipse.

In my last post, I discussed the ionosphere and why radio communication is possible.(see my post on it here The Ionosphere and How Radio Communication is Possible).

Since the ionosphere owes its existence primarily to solar radiation, it is therefore plausible that during eclipse event, the total electron content (TEC), which is available for radio propagation, is adversely affected. The distribution and dynamics of various ionospheric parameters are also affected. Therefore, eclipse events introduce a perturbation to the structure of the atmosphere in general.
The ionosphere is a pathway for long range, very low frequency (VLF) telecommunications transmissions around the world. This region of the Earth’s atmosphere is constantly affected by processes in regions outside it, as well as the solar radiation and particles. The free electrons and atoms in the ionosphere are constantly perturbed by traveling ionospheric disturbances. These ionosphere disturbances are often as a result of atmospheric gravity waves, which can be triggered by eclipses. These disturbances move in ripples through the charged particles which are ionized by the sun’s UV and X-ray light.

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CONCLUSION

During eclipse events, the moon completely or partially blocks rays from the sun from reaching the Earth, therefore causing many changes that are still not fully understood. The ionosphere plays an active role in our everyday lives. The distribution and dynamics of the ionosphere during the eclipse will affect our communication systems.
During totality, the moon completely blocks direct solar radiation, consequently decreasing the total amount of radiation that reaches the surface, as well as the radiation that reaches the Earth’s atmosphere. These changes are noticeable by Earth’s changing radiation estimates, which is the absolute solar irradiance the planet’s sunny side gets. Determination of this budget is important for accurate estimation of atmospheric and surface temperatures during such variations. A total solar eclipse presents a unique opportunity for investigating how the radiation budget changes.
Eclipse events, therefore, provide the opportunity to understand how the ionosphere responds to changes in solar radiation.

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References

What Are Solar Eclipses?
What Is a Solar Eclipse?
Eclipse: Who? What? Where? When? and How?
Studying the Sun’s Atmosphere with the Total Solar Eclipse of 2017

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