Science News Updates
The Earth's magnetic field (or geomagnetic field) is an ever-changing phenomenon that influences human activity and the natural world in a myriad of ways. The geomagnetic field changes from place to place, and on time scales ranging from seconds to decades to eons. These changes can affect health and safety, and economic well-being. The geomagnetic field, along with its associated phenomena, can both assist and degrade navigation and surveying techniques; it can impede geophysical exploration; it can disrupt electric power utilities, and pipeline operations; and it can influence modern communications systems, spacecraft, and more
The Earth's magnetic field is shaped approximately like that of a bar magnet and, like a magnet, it has two magnetic poles, one in the Canadian arctic, referred to as the North Magnetic Pole, and one off the coast of Antarctica, south of Australia, referred to as the South Magnetic Pole. At the North Magnetic Pole the Earth's magnetic field is directed vertically downward relative to the Earth's surface. Consequently, magnetic dip, or inclination is 90° . In addition, the North Magnetic Pole is the eventual destination for a traveller who follows his or her compass needle from anywhere on Earth.
The North Magnetic Pole is slowly drifting across the Canadian Arctic. The Geological Survey of Canada keeps track of this motion by periodically carrying out magnetic surveys to redetermine the Pole's location. The most recent survey, completed in May, 2001, determined an updated position for the Pole and established that it is moving approximately northwest at 40 km per year. The observed position for 2001 and estimated positions for 2002 to 2005 are given in the table.
|Year||Latitude ( °N)||Longitude ( °W)|
What is space weather, and what influences it? It is the weather in the region above 100 km where electrically charged particles are abundant. Most of us have seen the beauty of the northern lights - the aurora borealis - and they result from charged particles striking the atmosphere about 100-250 km above ground. The northern lights are produced in exactly the same way as a television picture. At the back of a TV is an electron gun in which electrons are increased in speed by passing them through a voltage of about 15,000 Volts. By controlling the path of these electrons on their way to the screen, they can be made to hit the screen and produce light that is the TV picture. In the high atmosphere, the electrons and ions are also subjected to high voltages that speed them up. These charged particles then travel toward the Earth along the Earth's magnetic field lines. (The Earth is a giant magnet.) When they strike the atmosphere, the "picture" is the northern lights.
What causes the voltages that speed up the charged particles high above the Earth? The answer goes right back to the Sun, the ultimate source of energy for life on the Earth. We all know that the Sun gives out heat and light that makes plants grow and drive our weather systems near the ground. But the Sun is a star, and it is so hot that the electrically charged gas around the Sun rises and blows out into space. This blowing gas is called the "solar wind." It takes several days to travel from the Sun to the Earth. When it strikes the outer part of the Earth's atmosphere, called the magnetosphere, large voltages are generated (they can be over 100,000 Volts!) as the solar wind particles move across the outer magnetic field of the Earth. These voltages accelerate the charged particles in our outer atmosphere, called the magnetosphere, up to high speeds. Of course, if the speed becomes very high, then these particles can crash into the satellites and cause failures of the satellite electronics, rendering the satellite useless.
Space weather can also affect us at the ground, particularly during "magnetic storms," which occur when the solar wind is directly coupled with, and stores large amounts of energy in, the Earth's magnetic field. During these storms, the same charged particles in space that cause the northern lights also produce huge electrical currents about 100-130 km above the ground. These currents can, in turn, induce currents at ground level, which can lead to sparks and explosions in oil or natural gas pipelines. Worse still, large induced currents are produced on power lines. Sometimes, these induced currents are so large that transformers worth millions of dollars are irreparably damaged, causing complete failure of power grids. Such a blackout occurred in Quebec and the northeastern United States in March 1989, near the last peak of the 11-year "sunspot cycle."
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