Space Weather - History of The Concept

History of The Concept

For centuries, people have noticed the aurora, which is caused by space weather, but did not understand it. Navigators in the Medieval Ages in Europe using a lodestone as a magnetic compass noted that occasionally the stone's direction was deflected from magnetic north. This was described in 1600 in De Magnete but was not understood to be caused by space weather until the 19th century. Space weather affected the first electrical telegraphs in the 1840 in various areas at various times. The great solar storm of 1859 disrupted telegraph operations around the world, causing articles to be published in many major newspapers at that time. Richard Carrington correctly connected the disruption with a solar flare observed the day before and a great deflection of the Earth's magnetic field (or geomagnetic storm) simultaneous with the telegraph disruption. With this connection, space weather, as we now know it, became a subject of academic research within the study of solar physics. Kristian Birkeland explained the physics of aurora by creating artificial aurora in his laboratory and predicted the solar wind. With the introduction of radio for commercial and military uses, it was noted that periods of extreme static or noise occurred. Severe radar jamming during a large solar event in 1942 led to the discovery of solar radio bursts (radio waves which cover a broad frequency range created by a solar flare), another aspect of space weather.

In the 20th century, the interest in space weather has expanded as military and commercial systems have come to depend on systems affected by space weather. Communications satellites are a vital part of global commerce. Weather satellite systems provide information about terrestrial weather. The signals from satellites of the Global Positioning System are used in a wide variety of commercial products and processes. Space weather phenomena can interfere with or damage these satellites or interfere with the radio signals to and from these satellites. Space weather phenomena can cause damaging surges in long electrical transmissions lines and expose passengers and crew of aircraft travel to radiation, especially on polar routes.

The International Geophysical Year (IGY), created an enormous increase in research into space weather. Ground-based data obtained during IGY demonstrated that the aurora occurred in an auroral oval, a permanent region of luminescence 15 to 25 degrees in latitude from the magnetic poles and 5 to 20 degrees wide. In 1958, the Explorer I satellite discovered the Van Allen belts or regions of radiation particles trapped by the Earth's magnetic field. In January 1959, the Soviet satellite Luna 1 first directly observed the solar wind and measured its strength. In 1969, INJUN-5 (a.k.a. Explorer 40) made the first direct observation of the electric field impressed on the Earth's high latitude ionosphere by the solar wind. In the early1970's, Triad data demonstrated that permanent electric currents flowed between the auroral oval and the magnetosphere. From these and other fundamental discoveries, research into space weather has grown exponentially.

Within our own solar system, space weather is greatly influenced by the speed and density of the solar wind and the interplanetary magnetic field (IMF) carried by the solar wind plasma. A variety of physical phenomena are associated with space weather, including geomagnetic storms and substorms, energization of the Van Allen radiation belts, ionospheric disturbances and scintillation of satellite-to-ground radio signals and long-range radar signals, aurora and geomagnetically induced currents at Earth's surface. Coronal mass ejections and their associated shock waves are also important drivers of space weather as they can compress the magnetosphere and trigger geomagnetic storms. Solar energetic particles, accelerated by coronal mass ejections or solar flares, are also an important driver of space weather as they can damage electronics onboard spacecraft (e.g. Galaxy 15 failure), and threaten the life of astronauts.

The term space weather came into usage in the 1990s when it became apparent that the impact of the space environment on human systems demanded a more coordinated research and application framework. The purpose of the National Space Weather Program in the USA is to focus research on the needs of the commercial and military communities which are affected by space weather, to connect the research community to the user community, to create coordination between operational data centers and to create better definitions of what the user community needs are. The concept was turned into an action plan in 2000, an implementation plan in 2002, an assessment in 2006 and a revised strategic plan in 2010. A revised action plan will be released in 2011 and a revised implementation plan will be release in 2012. One part of the National Space Weather Program is to make users aware that space weather affects their business.