Northern & Southern Lights

northern lights, or aurora borealis, at Hanle village in Ladakh early Saturday morning. Northern lights were also witnessed in other parts of the world, including in the United States and the United Kingdom. Meanwhile, southern lights, or aurora australis, were spotted in countries such as New Zealand and Australia. WHAT ARE AURORAS? Auroras are essentially natural lights that appear as bright, swirling curtains in the night sky and can be seen in a range of colours, including blue, red, yellow, green, and orange. These lights primarily appear near the poles of both the northern and southern hemispheres all year round but sometimes they expand to lower latitudes. As mentioned before, in the north, the display is called the aurora borealis; in the south, it is known as the aurora australis. WHY DO AURORAS OCCUR? It is due to activity on the surface of the Sun. The star continuously releases a stream of charged particles, mainly electrons and protons, and magnetic fields called the solar wind. As the solar wind approaches the Earth, it is deflected by the planet’s magnetic field, which acts like a protective shield. WHAT HAPPENS WHEN THE SOLAR WINDS APPROACH EARTH? However, some of the charged particles are trapped in the magnetic field and they travel down the magnetic field lines at the north and south poles into the upper atmosphere of the Earth. These particles then interact with different gases present there, resulting in tiny flashes that light up the night sky. When solar wind particles collide with oxygen, a green colour light is produced. Interaction with nitrogen produces shades of blue and purple. HOW DO THE AURORAS EXPAND TO MID LATITUDES? Auroras expand to midlatitudes when the solar wind is extremely strong. This happens when the activity on the Sun’s surface goes up, leading to solar flares and coronal mass ejections (CMEs), which are essentially extra bursts of energy in the solar wind. In such cases, the solar wind is so intense that it can result in a geomagnetic storm, also known as a magnetic storm — a temporary disturbance of the Earth’s magnetic field. It is during a magnetic storm that auroras can be seen in the mid-latitudes. One such geomagnetic storm was kicked off on Friday after a CME hit the Earth. That’s why auroras were visible in several parts of the world. The National Oceanic and Atmospheric Administration (NOAA) classified the storm as “extreme” and said more CME could hit the planet in the following days. IMPACT OF GEOMAGNETIC STORMS Geomagnetic storms can also affect space-dependent operations like:

• Global Positioning Systems (GPS).
• Radio and satellite communications.
• Flight operations.
• Power grids, and
• Space exploration programmes.