‘Coronal holes’ phenomenon
Recently, NASA has taken a picture of dark spots on the surface of the Sun which looks like eyes and smile. These spots are called ‘coronal holes’.
- NASA’s Solar Dynamics Observatory has observed the phenomenon of coronal holes in ultraviolet light.
- These holes can usually be seen in ultraviolet light, usually they cannot be seen with the normal eye.
- Coronal holes are areas on the Sun’s surface from where strong solar winds enter space.
- Since they contain less solar-matter, they have a lower temperature. Because of this they appear darker than their surroundings.
- Coronal holes are not a unique phenomenon. It is visible during almost the entire solar cycle of 11 years.
- These coronal holes can cause solar storms on Earth, as they emit a complex stream of solar winds.
- These strong solar wind currents interact with the Earth’s magnetic field and generate geomagnetic storms (GMS).
- GMS is a disturbance in the Earth’s magnetosphere. The magnetosphere is the area around the Earth. It is controlled by the Earth’s magnetic field.
- Earth’s magnetosphere shields Earth from most of the particles emitted by the Sun.
- Coronal holes are important in understanding the space environment around the Earth through which our technology and astronautics are facilitated.
- Solar storms occur during the release of magnetic energy associated with sunspots (the ‘dark’ regions on the Sun that are cooler than the surrounding photosphere – the lowest layer of the solar atmosphere) and can last for minutes or hours.
- Geomagnetic storms are related to the irregularities of Earth’s magnetic field that occur when there is an efficient exchange of energy from the solar wind to the Earth’s surrounding space environment.
Effect of Geomagnetic Storms
- These disrupt high-frequency radio transmissions and Global Positioning System equipment. They damage the electronic structure of the satellite and expose the astronauts to more radiation.
- The power supply to earth may be affected by a voltage rise due to changes in magnetic activity.
Source – The Hindu