Academic Reading — Test 199

Reading passage

SOLAR STORMS AND THE VULNERABILITY OF MODERN INFRASTRUCTURE A. The Sun is not the placid, unchanging disc it appears to be from Earth. Beneath its visible surface, powerful magnetic fields twist and tangle as the star rotates unevenly at different latitudes. When these fields become so distorted that they can no longer hold their configuration, they snap and reconnect in a violent release of energy known as a solar flare. Within minutes, a flare can radiate as much energy as billions of nuclear bombs, sending out a surge of X-rays and ultraviolet radiation that reaches Earth in roughly eight minutes, the time light takes to cross the distance separating the two bodies. Often, though not always, a flare is accompanied by a coronal mass ejection, or CME, an enormous bubble of magnetised plasma hurled outward from the Sun's corona at speeds that can exceed two thousand kilometres per second. Whereas the radiation from a flare arrives almost instantly, a CME is a more leisurely traveller, typically taking one to three days to reach our planet, which gives forecasters a valuable window to issue warnings. B. The first documented instance of a solar storm affecting human technology occurred in 1859, when the astronomer Richard Carrington observed an intensely bright flare and, less than a day later, telegraph systems across Europe and North America began to fail. Operators reported sparks leaping from their equipment and, in some cases, found that they could send messages even after disconnecting the batteries, as induced currents in the wires were strong enough to carry a signal alone. This event, now known as the Carrington Event, remains the benchmark against which scientists measure the potential severity of future storms. Although nothing on that scale has struck Earth since the dawn of the electrical age, a comparable eruption in 2012 narrowly missed the planet, passing through the orbital path Earth had occupied only days earlier. Researchers estimate that a direct hit could have cost trillions of dollars and taken years to repair fully. C. Satellites are amongst the most exposed assets in a solar storm, since they orbit beyond the thick blanket of atmosphere that ordinarily absorbs the worst of the Sun's radiation. The X-rays and energetic particles released during a flare can interfere directly with a satellite's electronics, corrupting data, scrambling navigation signals, or, in severe cases, permanently damaging delicate circuitry. Global positioning systems are particularly susceptible because their accuracy depends on precise timing signals that travel through the ionosphere, an upper atmospheric layer that becomes turbulent during a geomagnetic disturbance. Pilots flying polar routes, where coverage is already sparse, may have to switch to older methods of dead reckoning. Meanwhile, the increased density of the outer atmosphere caused by solar heating raises drag on satellites in low orbit, gradually pulling them closer to Earth unless controllers expend precious fuel to compensate. D. The threat to power grids arises through a different, though related, mechanism. When the charged particles of a CME collide with Earth's magnetic field, they distort it and induce electric currents in the ground itself. These geomagnetically induced currents, abbreviated to GICs, seek out the path of least resistance, which frequently happens to be the long metal conductors of high-voltage transmission lines. Although the currents are direct rather than alternating, and therefore cannot be used by the grid, they still flow into transformers, where they can saturate the iron core and cause overheating. In the most famous instance of this process, a geomagnetic storm in March 1989 induced currents strong enough to trip protective relays across the Hydro-Québec network in Canada, plunging six million people into darkness within ninety seconds. Engineers needed roughly nine hours to restore power, and the financial losses ran into hundreds of millions of dollars. E. Because the consequences of a major storm can be so far-reaching, several national agencies now operate dedicated space weather forecasting centres that monitor the Sun continuously for signs of an impending eruption. Spacecraft positioned between the Sun and Earth provide early measurements of an approaching CME's speed, density, and magnetic orientation, information fed into models predicting how forcefully the storm will strike. Grid operators who receive sufficient warning can take precautionary measures, such as reducing the load on vulnerable transformers, while satellite operators can place spacecraft into a protective mode that shuts down non-essential systems until the danger has passed. Critics note, however, that forecasting can rarely predict the precise orientation of a CME's magnetic field until it is already close to Earth, leaving only a brief interval, sometimes as little as fifteen minutes, in which to confirm whether a strike will be glancing or direct. F. As society grows more dependent on satellite navigation, digital communication, and an electricity supply that increasingly relies on computerised control systems, the economic stakes of a severe solar storm continue to rise. Some researchers argue that a Carrington-scale event occurring today would expose interdependencies that did not exist in 1859, since a prolonged blackout would also disable the pumps, refrigeration, and communication networks that modern societies depend upon for water and food. Consequently, engineers are increasingly examining ways to harden transformers against induced currents and to design satellites with components that can better withstand radiation. Whether such measures will be implemented widely before the next severe storm arrives remains an open question.