Aurora vs Sheffield

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An aurora (plural: auroras or aurorae), sometimes referred to as polar lights (aurora polaris), northern lights (aurora borealis), or southern lights (aurora australis), is a natural light display in the Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras are the result of disturbances in the magnetosphere caused by solar wind. These disturbances are sometimes strong enough to alter the trajectories of charged particles in both solar wind and magnetospheric plasma. These particles, mainly electrons and protons, precipitate into the upper atmosphere (thermosphere/exosphere).

The resulting ionization and excitation of atmospheric constituents emit light of varying color and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of acceleration imparted to the precipitating particles. Precipitating protons generally produce optical emissions as incident hydrogen atoms after gaining electrons from the atmosphere. Proton auroras are usually observed at lower latitudes.

Source: Wikipedia

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Sheffield is a city and metropolitan borough in South Yorkshire, England. Historically part of the West Riding of Yorkshire its name derives from the River Sheaf which runs through it. With some southern suburbs annexed from Derbyshire, the city has grown from its largely industrial roots to encompass a wider economic base. The population of the City of Sheffield is 584,853 (mid-2019 est.) and it is one of the eight largest regional English cities that make up the Core Cities Group. Sheffield is the second-largest city in the Yorkshire and the Humber region and the third-largest English district by population. The metropolitan population of The city of Sheffield is 1,569,000.The city is in the eastern foothills of the Pennines, and the valleys of the River Don and its four tributaries, the Loxley, the Porter Brook, the Rivelin and the Sheaf. Sixty-one per cent of Sheffield's entire area is green space, and a third of the city lies within the Peak District national park. There are more than 250 parks, woodlands and gardens in the city, which is estimated to contain around 4.5 million trees.Sheffield played a crucial role in the Industrial Revolution, with many significant inventions and technologies having developed in the city.

In the 19th century, the city saw a huge expansion of its traditional cutlery trade, when stainless steel and crucible steel were developed locally, fuelling an almost tenfold increase in the population. Sheffield received its municipal charter in 1843, becoming the City of Sheffield in 1893. International competition in iron and steel caused a decline in these industries in the 1970s and 1980s, coinciding with the collapse of coal mining in the area. The 21st century has seen extensive redevelopment in Sheffield, along with other British cities. Sheffield's gross value added (GVA) has increased by 60% since 1997, standing at £11.3 billion in 2015. The economy has experienced steady growth averaging around 5% annually, greater than that of the broader region of Yorkshire and the Humber.The city has a long sporting heritage and is home to both the world's oldest football club, Sheffield F.C., and the world's oldest football ground, Sandygate. Games between the two professional clubs, Sheffield United and Sheffield Wednesday, are known as the Steel City derby. The city is also home to the World Snooker Championship and the Sheffield Steelers, the UK's first professional ice hockey team.

Source: Wikipedia