However, over a very large region they can build up to apply a considerable voltage. The electric fields from auroras are small, and undetectable to human senses.
#Space weather generator
A generator effect takes place when dancing auroras make magnetic fields vary, but unlike in the generators that produce much of our electricity, the electric fields from auroras are uncontrolled. These processes can also produce bright auroras, whose beauty hides danger since they in turn produce magnetic fields. Earth's radiation belts can be greatly energized, endangering astronauts and even satellites.
In that case, a process known as "reconnection" allows much of the cloud's energy to be transferred to the region near Earth, and accumulate largely on the night side, despite the cloud hitting on the side facing the sun.īy secondary processes, usually involving further reconnection, this energy produces space weather effects. The effect of an interplanetary cloud is greatly enhanced if the direction of its magnetic field is opposite to Earth's own field where it hits the barrier of Earth's magnetosphere. Unlike the detectable, sometimes even visible, water content in the atmosphere that is so important in meteorology, the magnetic field of gas ejected from the sun, including in hot and denser clouds from explosions, is almost impossible to detect from afar. Much as with tornadoes on Earth, we know generally when conditions are favorable for these localized explosions, but precise prediction is difficult.Įven once an event is detected, if a large mass of fast, hot and dense gas is shot in our direction (and such a "cloud" in turn is difficult to detect, coming at us against the glare of the sun), there is a further complicating factor in predicting its danger. Magnetic fields are concentrated near sunspots, and produce electromagnetic phenomena like solar flares (the name says it all) and coronal mass ejections (opens in new tab). Much like a breeze that can barely move a thread can move a huge sailing ship when caught on the large sails, the effect of solar wind, through its direct pressure (like on a sail) or through its magnetic field interacting with Earth’s, can be enormous.Īs the origin point, the sun itself is a seething mass of hot gas and magnetic fields, and their interaction is complex, sometimes even explosive. The very thin solar wind, with a very weak magnetic field, can nevertheless affect Earth in part because it interacts with a large magnetic bubble around Earth, called the magnetosphere, over a very large area, at least a hundred times as big as the surface of our planet. This is much smaller than Earth's own field that we can detect with a compass at the surface, and vastly smaller than that near a fridge magnet, but it can interact with Earth, with an important role in space weather. Unlike winds on Earth, this solar wind carries along a magnetic field. Its outermost atmosphere blows into space at supersonic speeds, although at such low density that interplanetary space is more rarified than what is considered a vacuum in our laboratories. Most space weather originates from the sun (opens in new tab). In contrast, the prediction of space weather is only truly reliable about one hour in advance! Exploring the limits in weather forecasting gave rise to chaos theory, sometimes called the "butterfly effect." The buildup of error brings about the two-week practical limit. Other measurements are also be readily taken, for example, by the nearly 2,000 weather balloons launched each day.
Important aspects of weather, like moisture content, can be measured by satellites that monitor continuously. Meteorological prediction is based on a good knowledge of underlying theory, codified into massive computer programs running on the most advanced computers, with huge amounts of input data. Scientific weather forecasting originated about a century ago, with the term "front" being associated with the First World War (opens in new tab). We are now used to large-scale meteorological forecasts that are quite accurate for about a two-week timescale. An ability to predict space weather is an essential tool in providing warnings so that mitigation can be attempted, and to hopefully, in extreme cases, forestall a disaster.
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