Stable Auroral Arc (SAR)

About Stable Auroral Arc

• It is a rare atmospheric phenomenon which was observed during a strong G3-class geomagnetic storm.
• Unlike auroras, which occur when charged particles from space hit the atmosphere causing it to glow, SAR arcs form differently.
• They are an indication of heat energy leaking into the upper atmosphere from Earth's ring current system, a donut-shaped circuit carrying millions of amps around our planet.
• During the recent geomagnetic storm, the ring current was energised by hours of intense geomagnetic activity, with energy dissipating into these SAR arcs.
• This global event was registered in many parts of the world.

How does Aurora form?

• It is formed when the sun is ejecting charged particles from its corona, creating solar wind. When that wind slams into Earth's ionosphere, the aurora is born.
• In the Northern Hemisphere, the phenomenon is called the northern lights (aurora borealis), while in the Southern Hemisphere, it's called the southern lights (aurora australis).
• The hemispheric asymmetry of the aurora is due in part to the sun's magnetic field interfering with Earth's magnetic field.

 Q1) What is ionosphere?

It is a region of Earth's upper atmosphere, extending from about 48 kilometers to up to 600 kilometers above the Earth's surface. It is a region where the atmosphere becomes ionized, meaning that the atoms and molecules in this part of the atmosphere lose or gain electrons, resulting in the presence of charged particles called ions.

Source: IIA’s observatory captures red-hued Aurora from Hanle, Merak