UPSC Prelims 2022 Q40: Solar Storm Effects on Earth — Explained

If a major solar storm (solar flare) reaches the Earth, which of the following are the possible effects on the Earth?

1. GPS and navigation systems could fail.

2. Tsunamis could occur at equatorial regions.

3. Power grids could be damaged.

4. Intense auroras could occur over much of the Earth.

5. Forest fires could take place over much of the planet.

6. Orbits of the satellites could be disturbed.

7. Shortwave radio communication of the aircraft flying over polar regions could be interrupted.

Select the correct answer using the code given below:

1, 2, 4 and 5 only
2, 3, 5, 6 and 7 only
1, 3, 4, 6 and 7 only
1, 2, 3, 4, 5, 6 and 7

Answer: (c) 1, 3, 4, 6 and 7 only

Statement-wise explanation

1: correct — A flare's X-ray burst adds extra ionisation to the lower ionosphere on the sunlit side of the Earth. A geomagnetic storm that follows a coronal mass ejection (CME) makes the ionosphere uneven and disturbed. GPS signals cross the ionosphere on their way to receivers, so positions drift or the receiver loses lock. NOAA reported that during the May 2024 storm some GPS receivers had trouble locking on and gave wrong positions.
2: incorrect — A tsunami needs a sudden shift of a large body of sea water. Undersea earthquakes, submarine landslides and volcanic eruptions cause this. Solar storm energy is absorbed about 80 km or more above the ground, in the ionosphere and magnetosphere. It cannot push the ocean, and nothing about it targets equatorial regions.
3: correct — A geomagnetic storm induces electric currents in long conductors such as transmission lines. These currents enter transformers through their grounding and can overheat or damage them. In March 1989 a storm collapsed the Hydro-Québec grid in about 90 seconds and left six million people without power for roughly nine hours (NOAA).
4: correct — Auroras form when charged particles guided by the Earth's magnetic field strike oxygen and nitrogen in the upper atmosphere. Normally they stay in ovals near the poles. In a major storm the ovals spread towards the equator. The 1859 Carrington storm produced auroras as far south as Hawaii and Central America (NOAA).
5: incorrect — Solar storm particles and X-rays are stopped high in the atmosphere. Their energy heats the thermosphere, not the surface, so they cannot ignite vegetation. Forest fires depend on fuel, dry weather and a source of ignition such as lightning or people. No mechanism links a solar storm to fires across much of the planet.
6: correct — A geomagnetic storm heats the thermosphere, and it expands. Denser air rises into low-Earth orbit, drag on satellites increases, and their orbits decay faster. In February 2022 SpaceX lost most of the 49 Starlink satellites it launched on 3 February. A storm raised drag by up to 50 per cent at their low deployment altitude, and up to 40 of them re-entered.
7: correct — Aircraft on polar routes depend on high-frequency (shortwave) radio, which reflects off the ionosphere. Energetic solar protons enter the atmosphere along magnetic field lines near the poles and add heavy ionisation, so the radio signal is absorbed instead of reflected. NOAA's solar radiation storm scale lists HF radio blackout through the polar regions as an effect of strong events.

How to eliminate

Statements 2 and 5 are false from basic geography. Tsunamis come from sudden movement of the sea floor or water mass, and forest fires need fuel and an ignition source on the ground. A solar storm does neither, because its energy stays in the upper atmosphere. The words 'at equatorial regions' and 'over much of the planet' make both claims even weaker. Once you drop 2, only one option is left, because the other three all include statement 2. You do not even need statement 5. Statement 4 also says 'over much of the Earth', which can look like an overstatement. The point to remember is that auroras spread far towards the equator during major storms. The 1859 Carrington storm and the May 2024 storm both showed this.

Know more

Space weather means changes in conditions near the Earth driven by the Sun. Three solar events matter, and they arrive at different times:

Event	What travels	Reaches Earth	Main effects
Solar flare	X-rays, UV (light)	~8 minutes	HF radio blackout on the sunlit side; GPS errors
Solar energetic particles	High-energy protons	Minutes to hours	Radiation risk to satellites, astronauts and polar flights; HF blackout over the poles
Coronal mass ejection (CME)	A billion-tonne cloud of magnetised plasma	~18 hours to a few days	Geomagnetic storm: currents induced in power grids, auroras, satellite drag

The question says 'solar flare', but most of the listed effects come from the CME that often follows a flare and the geomagnetic storm it triggers. The Earth's magnetosphere deflects most of the solar wind. A CME with a southward-pointing magnetic field links up with the Earth's field and pours energy in. This energy ends up in the ionosphere and thermosphere, 80 km or more above the ground. That is why a solar storm can disrupt technology but cannot affect sea level, weather on the ground or vegetation.

NOAA rates events on three five-step scales: R (radio blackouts, from flares), S (solar radiation storms) and G (geomagnetic storms).

The Sun's activity follows a roughly 11-year sunspot cycle. Solar Cycle 25 began in December 2019, so storms became more frequent in the years after.

India's Aditya-L1 was launched in September 2023 and sits at the Sun–Earth L1 point, about 1.5 million km from the Earth. It watches the Sun and measures the solar wind before it reaches the Earth.

In the news

In February 2022 a geomagnetic storm caused SpaceX to lose up to 40 of the 49 Starlink satellites launched on 3 February, through increased atmospheric drag. This was widely reported a few months before the June 2022 Prelims. Solar Cycle 25 was also climbing towards its maximum, and ISRO was preparing Aditya-L1, which kept space weather in the news.

NCERT Concepts to Revise

Geomagnetic storm: Most of the listed effects come from a geomagnetic storm, not from the flare's light alone.
Aurora: Statement 4 depends on how far auroras can spread from the poles during a storm.
Ionosphere: GPS errors and shortwave radio blackouts both depend on how the ionosphere changes during a storm.
Thermosphere: Heating of this layer during storms changes the drag on low-orbit satellites, which statement 6 is about.