Corona of Sun Meaning
Our Sun is surrounded by an atmosphere, which is a layer of gases. The corona is the Sun's atmosphere's outermost layer. The brilliant brightness of the Sun's surface frequently obscures the corona. This makes it impossible to see without the use of specialised equipment. The corona, on the other hand, may be observed during a total solar eclipse. The moon passes between the Earth and the Sun during a complete solar eclipse. When this occurs, the moon conceals the Sun's strong brightness. The eclipsed Sun is then surrounded by a dazzling white corona. In this post, we'll look at what coronal meaning is, how solar eclipses affect the corona and solar wind.
Corona of Sun
The corona is the outermost portion of the Sun's atmosphere, made mostly of plasma (hot ionised gas). It has a temperature of around two million kelvins and a very low density. As a result of the Sun's magnetic field, the corona's size and form change all the time. The solar wind, which sweeps radially outward through the whole solar system, is created by coronal gas expansion and only reaches the heliopause. Despite its high temperature, the corona generates very little heat due to its low density; that is, the component gas molecules are so sparse that the energy content per cubic centimetre is significantly less than that of the Sun's core.
The corona radiates only about half as brilliantly as the Moon and is generally invisible to the naked eye due to the brilliance of the solar surface. During a total solar eclipse, the Moon blocks out the light from the photosphere, allowing for naked-eye observations of the corona and this is one of the major effects of solar eclipse on corona. The corona may also be observed under non-eclipse conditions using a coronagraph, which is a specialised telescopic equipment.
Reason for the Hotness of the Corona of the Sun
The high temperatures of the corona are a bit of a mystery. Assume you're sitting close to a bonfire. It's comfortable and toasty. However, as you move away from the fire, you feel a lot better. This appears to be the reverse of what appears to occur on the Sun. For a long time, astronomers have been attempting to answer this puzzle. The corona is located in the Sun's outer atmosphere, far from its surface. The corona, on the other hand, is hundreds of times hotter than the Sun's surface.
One conceivable solution might have come from a NASA project named IRIS. The expedition detected "heat bombs," which are packets of extremely hot material that flow from the Sun into the corona. The heat bombs burst in the corona, releasing their energy as heat. However, scientists believe that this is merely one of several ways in which the corona is heated.
Solar Wind
The solar wind is a stream of particles that flows throughout the solar system at roughly one million miles per hour after leaving the sun. The solar wind, initially proposed by University of Chicago professor Eugene Parker in the 1950s, is visible in the halo encircling the sun during an eclipse and, on rare occasions, when the particles collide with the Earth's atmosphere, resulting in the aurora borealis, or northern lights. While the solar wind protects Earth from potentially harmful space particles, storms may also damage our satellite and communications networks.
The Sun, like all stars, loses material by a stellar wind. Stellar winds are fast-moving material flows that are ejected from stars (protons, electrons, and atoms of heavier metals). These winds are distinguished by a continuous outflow of material flowing at velocities ranging from 20 to 2,000 km/sec. In the case of the Sun, wind speeds range from 200 to 300 km/sec in tranquil parts to 700 km/sec in coronal holes and active regions.
Stellar winds have different sources, ejection rates, and velocity depending on the mass of the star. The extraordinarily high temperature (millions of degrees Kelvin) of the corona causes the wind in comparatively cold, low-mass stars like the Sun. This high temperature is thought to be the result of magnetic field interactions at the star's surface, giving enough energy for coronal gas to escape the star's gravitational pull as a wind.
Although stars of this sort release a small proportion of their mass as a stellar wind each year (for example, only 1 part in 1014 of the Sun's mass is ejected in this fashion each year), this nevertheless implies material losses of millions of tonnes each second. Stars like our Sun lose only a fraction of a percent of their mass through stellar winds during their entire lifespan.
When the solar wind interacts with the Earth's upper atmosphere and magnetic field, it produces a variety of phenomena, the most visible of which are the aurorae (Borealis and Australis). These are formed when solar wind particles propelled by the Earth's magnetic field clash with upper-atmosphere atoms and molecules. Light at specific wavelengths is emitted as atoms and molecules de-excite. A similar effect may be witnessed at Jupiter's magnetic poles.
FAQs on Corona of Sun
1. What is the Sun's corona?
The Sun's corona is the outermost layer of its atmosphere. It is a vast, tenuous region of plasma (an extremely hot, ionised gas) that extends millions of kilometres into space. Although it is incredibly hot, its density is very low, which is why it is much fainter than the Sun's visible surface.
2. How is the Sun's corona visible from Earth?
The corona is normally invisible because it is overwhelmed by the bright light from the Sun's main surface, the photosphere. It can only be seen from Earth under two specific conditions:
- During a total solar eclipse, when the Moon blocks the photosphere, the faint, wispy corona becomes visible as a halo.
- Using a specialised instrument called a coronagraph, which artificially blocks the Sun's disc to allow observation of the corona.
3. What is the difference between the Sun's corona and its photosphere?
The corona and the photosphere are two distinct layers of the Sun with key differences:
- Location: The photosphere is the visible 'surface' of the Sun, while the corona is the outermost, extended atmosphere.
- Temperature: The photosphere has a temperature of about 5,500°C. In contrast, the corona is shockingly hotter, reaching temperatures of 1 to 2 million °C, or even higher.
- Density: The photosphere is relatively dense, whereas the corona is extremely tenuous, with a much lower density.
- Visibility: The photosphere is the source of most of the Sun's light and is always visible, while the corona is only visible during a total solar eclipse or with a coronagraph.
4. Why is the Sun's corona so much hotter than its surface?
This is a major, unresolved question in astrophysics known as the coronal heating problem. While the Sun's core is the source of its energy, it's a paradox that the temperature drops to about 5,500°C at the surface (photosphere) and then skyrockets to millions of degrees in the corona further away. The leading theories suggest energy is transferred to the corona through mechanisms like:
- Nanoflares: A continuous storm of tiny, unobservable explosions that release energy into the corona.
- Wave Heating: Energy carried upwards from below the photosphere by various types of plasma waves that dissipate in the corona, converting their energy into heat.
5. What is the primary role or importance of the Sun's corona?
The primary importance of the Sun's corona is that it is the source of the solar wind. The plasma in the corona is so hot and energetic that the Sun's gravity cannot hold onto it. This plasma constantly flows outward, streaming through the solar system as the solar wind, affecting planets, comets, and spacecraft.
6. Is the Sun's corona the same as the halo sometimes seen around the Sun or Moon?
No, they are two completely different phenomena.
- The Sun's Corona is the actual outer atmosphere of the Sun, made of plasma and located millions of kilometres away in space.
- An atmospheric halo is an optical illusion that occurs within Earth's own atmosphere. It is created when sunlight or moonlight refracts through ice crystals in high-altitude cirrus clouds, forming a ring of light.
7. What are the main components of the corona?
The corona is primarily composed of plasma, which is the fourth state of matter. This plasma consists of highly ionised atoms, mainly hydrogen and helium, that have been stripped of their electrons due to the extreme temperatures. This mix of free-floating electrons and ions is what makes the corona electrically conductive and creates the solar wind.
