Space Weather

Earth is not only enlightened by the Sun. Our planet is also continuously swept by a flux of particles emitted from the star with embedded “frozen” magnetic fields which confines the Earth’s magnetosphere in a drop shaped envelope in the radial direction from the Sun to the Earth.

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Artist’s rendering of the solar wind which interacts with the Earth’s magnetosphere. Credit: NASA.

Generally this solar plasma, known as travels at a speed of 400 km/s and takes 4 days to reach our planet. During intense periods of solar activity, in coincidence with the 11-year solar cycle, a sequence of giant events like solar flares and coronal mass ejections (CMEs) may affect all the planets and bodies of the solar system, including the Earth.

X-rays and ultraviolet radiations from flares travel at the speed of light and with sunlight affect the dayside of our planet about 8 minutes after their emissions. Solar energetic particles can reach Earth in 15 minutes since they travel at relativistic speeds, affecting satellite operations, communications, navigation and electric power distribution grids. Finally CMEs, travelling at supersonic speed (1000-1200 km/s), reach Earth in less a day and cause geomagnetic storms. In some adverse conditions, astronauts in space missions and pilots and flight attendants of commercial airline in polar routes are exposed to radiations which may exceed the safe levels assigned by aviation authorities.

Solar Flares. Credit: Nasa's Solar Dynamic Observatory (SDO).
Solar Flares. Credit: Nasa’s Solar Dynamic Observatory (SDO)

Images of the Sun during eleven-year cycle of progressive activity from solar minimum (upper left) to maximum condition (middle picture) an back to minimum (upper right). Credit: NASA.
Images of the Sun during eleven-year cycle of progressive activity from solar minimum (upper left) to maximum condition (middle picture) an back to minimum (upper right). Credit: NASA.

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Coronal mass ejection (CME). Credit: Nasa’s Solar Dynamic Observatory (SDO).

X-rays and ultraviolet radiations from flares travel at the speed of light and with sunlight affect the dayside of our planet about 8 minutes after their emissions. Solar energetic particles can reach Earth in 15 minutes since they travel at relativistic speeds, affecting satellite operations, communications, navigation and electric power distribution grids. Finally CMEs, travelling at supersonic speed (1000-1200 km/s), reach Earth in less a day and cause geomagnetic storms. In some adverse conditions, astronauts in space missions and pilots and flight attendants of commercial airline in polar routes are exposed to radiations which may exceed the safe levels assigned by aviation authorities.

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Dynamic and constant solar effects on Earth. The two solar constants, sunlight and solar wind, takes 8 minutes and 4 days, respectively, to reach Earth. Arrival times of dynamic solar events such as flares, solar energetic particles and CMEs, are approximated and range from immediate effect to several days. Credit: NASA/Berkley.

All these aspects and related issues including fundamental scientific researches and practical applications for assessing, predicting and mitigating the effects on technological systems are the prime topics dealt by a new branch of space physics called Space Weather.

Extreme space weather condition can impact on modern critical technological infrastructures whose  electric power failure and disruption remains a primary concern and, as secondly effects, intermittent loss of HF and similar sky wave radio systems, loss of communication satellite services and GNSS navigation and timing signals degradation. Given the technological interdependencies of modern societies such critical conditions can imply significant economic losses as the one faced by the Canadian authorities in 1989, caused by an extreme geomagnetic storm that collapsed the Hydro Quebec power grid. In recent years a deeper interest from the scientific and emergency management communities for a better understanding  of the potential hazards and vulnerabilities both at space and ground-base infrastructure levels is rising.