Coronal Holes

Context: Recently, NASA’s Solar Dynamics Observatory caught the Sun “smiling.” Seen in ultraviolet light, these dark patches on the Sun are known as coronal holes and are regions where fast solar wind gushes out into space.

About Coronal holes:

• These are regions on the sun’s surface from where fast solar wind gushes out into space.
• Because they contain little solar material, they have lower temperatures and thus appear much darker than their surroundings.
• Here, the magnetic field is open to interplanetary space, sending solar material out in a high-speed stream of solar wind.
• Coronal holes can last between a few weeks to months.
• They can last much longer during solar minimum – a period of time when activity on the Sun is substantially diminished
• These coronal holes are important to understand the space environment around the earth.
• While it is unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, without looping back down to the surface as they do elsewhere.

Geomagnetic Storm:

• Geomagnetic storms relate to earth’s magnetosphere – the space around a planet that is influenced by its magnetic field.
• When a high-speed solar stream arrives at the earth, in certain circumstances it can allow energetic solar wind particles to hit the atmosphere over the poles.
• Such geomagnetic storms cause a major disturbance of the magnetosphere as there is a very efficient exchange of energy from the solar wind into the space environment surrounding earth.
• In cases of a strong solar wind reaching the earth, the resulting geomagnetic storm can cause changes in the ionosphere, part of the earth’s upper atmosphere.
• Radio and GPS signals travel through this layer of the atmosphere, and so communications can get disrupted.