The Great American Eclipse of 2017 left ‘bow waves’ in Earth’s atmosphere

Credit: NASA

Researchers say: ‘Study of wave characteristics reveals complex interconnections between the Sun, Moon, and Earth’s neutral atmosphere and ionosphere.’

The waves in the upper atmosphere are similar to the V-shaped waves left behind by a ship moving through water, reports The IB Times.

The 21 August total solar eclipse that overshadowed the entire stretch from Oregon to South Carolina, not only offered some mind-boggling views, but also left a weird effect on Earth’s atmosphere.

The event created heat-energy ripples or “bow waves”, something akin to the V-shaped waves left behind by a ship moving through water, in Earth’s upper atmosphere, Gizmodo reports.

Scientists have long theorised the effect, but it proved too small to be detected until researchers from MIT’s Haystack Observatory and the University of Tromsø in Norway collaborated and tracked it down.

The team deployed as many as 2,000 sensors across different parts of the country, which came into action during the Great American Eclipse and spotted the ripples in our planet’s ionosphere, the part upper atmosphere containing charged as well neutral particles. The phenomenon was seen all over the Central and eastern US.

When the Moon comes in between the Sun and Earth and blocks its light, there is a sudden drop in the heat energy prevailing in the overshadowed area. However, the overshadowed zone keeps moving with the movement of the Moon taking the heat energy with it and creating the bow-wave effect.

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Plain Language Summary [from the paper]

During solar eclipses, the Moon’s shadow causes a large reduction in atmospheric energy input, including the stratosphere and both the thermosphere and ionosphere (∼100–1,000 km altitudes). Theoretical studies since the 1960s have predicted that the Moon’s supersonic shadow should generate atmospheric bow waves, similar to a fast-moving river boat. However, observations were geographically limited for these weak and complicated waves. In 2017, high fidelity and wide coverage ionospheric observations were made using a North American Global Navigation Satellite System (GNSS) ∼2,000 receiver network. Eclipse passage generated clear ionospheric bow waves in electron content disturbances emanating from totality primarily over central/eastern United States. Study of wave characteristics reveals complex interconnections between the Sun, Moon, and Earth’s neutral atmosphere and ionosphere.