Aurora
Aurorae are created when some violent events on the Sun’s surface throw up a mass of charged particles into space.
A geomagnetic storm happens on the earth when these particles become trapped in the planet’s magnetic field and interact with atoms in the upper atmosphere.
These interactions finally produce aurorae.
These storms are rare, occurring around once every few decades.
The last time charged particles from the Sun blew into the earth with similar energy and intensity was in 2003.
And both events happened as the Sun was nearing the peak of its solar cycle — an 11-year period during which the star’s magnetic field flips.
The peak is when the flip actually happens, creating magnetically active patches on the star’s surface called sunspots.
These sunspots grow and shrink as solar cycles begin and end.
The charged particles that struck the earth on May 10 are rooted in events at these sunspots
Magnetic fields deflect charged particles, but the earth’s couldn’t prevent many of the particles from slipping through to locations close to the planet’s magnetic poles.
Here, their interactions with oxygen atoms in the upper atmosphere produced vivid red light, and with oxygen, and nitrogen in the lower atmosphere producing green and purple light, respectively.
Thus, the world had its aurorae
An aurora also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis)
Recent events
In the last solar cycle, which spanned the 2010s, no sunspot gave rise to a geomagnetic storm that matched the intensity of that on Friday.
Since early May, scientists have been monitoring the sunspot AR 3664.
It was growing in size: by May 7, it was 16-times as wide as the earth and brimming with magnetic energy.
The supercharged magnetic fields in such sunspots sometimes disconnect and reconnect in fractions of a second, releasing a great burst of energy that sends plumes of charged particles called coronal mass ejections (CMEs) into space.
On May 10, three CMEs struck the earth.
CMEs happen together with solar flares — powerful flashes of radiation — and all these active events are collected under the term ‘solar storms’
On May 10, a few space-weather forecasters — including the Center of Excellence in Space Sciences India (CESSI) at IISER Kolkata (CESSI is the only Indian institute that provides timely updates on space weather) — warned of potential power disruptions.
The fluctuations in the earth’s magnetic field during a geomagnetic storm can send currents surging through cables
These storms can also affect satellites in orbit on which our communication and GPS navigation networks depend
This is not the worst geomagnetic storm to have ever struck the earth.
In 1859, the Sun spouted a strong solar flare and triggered a super-geomagnetic storm on the earth, the most powerful in history.
Telegraph wires either caught fire or were able to operate without a power supply
Recent Aurorae appeared even in places where aurorae aren’t usually visible.
For instance, people at the Indian Astronomical Observatory spotted an aurora over Hanle in Ladakh — far away from places near the poles, where they are a more common sight.
Beautiful though the aurorae are, the events on the Sun that produce them can trigger blackouts on the earth, knock out satellites in space, endanger the lives of astronauts, and affect space weather throughout the Solar System.
Studying, understanding, and, in future, predicting them is thus a key goal of solar physics research.
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