 What is "space weather"? |
| Space weather originates from the Sun. It generally refers to all solar activities such as sunspots and solar flares, and the effects they may have on the Earth. The intensity varies from time to time, sometimes strong and sometimes weak. "Good weather" means a calm period of solar activities, while "bad weather" is a period of frequent and disturbed activities which may affect telecommunications, navigation and power systems on Earth and the operations of satellites or spacecraft. |
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| Effects of Space Weather |
Effects on Satellites and Spacecraft
Satellites and spacecraft are vulnerable to space weather.
Increased radiation from the Sun and occurrence of geomagnetic storms (i.e. severe distortion of geomagnetic field of the Earth) may cause disturbances such as increases in density in the Earth's upper atmosphere. These result in a greater drag on the movement of satellites and spacecraft, causing a slow-down or even a change in orbit. Their useful life may also be reduced. Operators of these facilities are highly concerned because of these high operation and maintenance costs.
Charged particles from the Sun may strike the spacecraft and satellites and make direct physical damage to the equipment. Also, charge accumulation may occur on the electronics on board satellites and spacecraft, resulting in a build-up of the electric field. When an electrical discharge eventually happens, the electronics may be damaged, hence affecting the operation of the satellites and spacecraft.
In May of 1998, intense electron fluxes were released from the Sun. During that time, an American communication satellite, Galaxy-4, failed, leading to the suspension of paging service for 45 million people. It was believed that electrical discharge between electronic components onboard the satellite was the main cause of the failure.
Effects on human body
The intense radiation from violent space weather can affect human DNA or cell replications. Astronauts in space, if not properly protected from the dangerous radiation, may be adversely affected. Flight at high altitudes may also result in a higher dose of radiation at the height of solar activity.
• Effects on Communication and Navigation Systems
To enable long-distance communication, many telecommunication systems transmit radio signals via the ionosphere. Electromagnetic waves produced by solar flares may disturb the ionosphere and interfere with radio signals, resulting in degraded communication quality.
Maritime and aviation navigation systems use low frequency signals to locate vessels or aircraft. Intense solar activity may generate inaccuracy in information in these systems, causing errors in the positioning of vehicles.
• Effects on Electric Power and Pipelines
Occurrence of geomagnetic storms (i.e. severe distortion of geomagnetic field of the Earth) can induce electric current in oil pipelines and electric cables. Flow meters may be affected, giving incorrect reading. The rate of corrosion of pipeline may also increase. The abnormal current induced in power grids may damage transformers because of overheating. During the great geomagnetic storm in 1989, transformer failures resulted in electricity suspension in Quebec for 9 hours. |
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| How space weather is monitored? |
Solar phenomena, such as the sun spots and solar flares, provide good indications of space weather. In particular, the intensity of x-ray and ultraviolet radiation from the Sun provide valuable information for space weather forecasting.
Space weather can be observed from the ground and from space. On the ground, telescopes and optical instruments are used to record the number of sun spots, as well as to observe aurora, which provide evidence of geomagnetic storms.
Observation from the ground is affected by the Earth's atmosphere and weather. Observation from space does not have such a limitation. In recent years, satellites and spacecraft have been used to monitor the space weather. These include: Advanced Composition Explorer (ACE), Solar and Heliospheric Observatory (SOHO), Transition Region And Coronal Explorer (TRACE), and Geosynchronous Operational Environmental Satellite (GOES). Details are as follows.
ACE was launched in 1997 by the United States . It is capable of measuring the composition of charged particle from the Sun and the interplanetary magnetic field. It gives us important information on the materials released during solar events.
A cooperation between European Space Agency (ESA) and National Aeronautics and Space Administration (NASA), SOHO was launched in 1995 to study solar wind and the internal structure of the Sun.
TRACE was launched in 1998 by the United States . It aims at studying the evolution of magnetic field structures of the Sun.
The GOES Solar X-ray Imager operated by the United States is capable of monitoring solar flare events.
Knowledge of the Sun's structure and the solar system's formation gives us clues to space weather. The Genesis spacecraft was launched in 2001 to collect the solar wind particles. Its sample-collection capsule returned to the Earth on 8 September 2004. Despite a crash due to failure of the parachute system, a significant amount of the samples were recovered. Study of the solar wind particles will help our understanding of the origin and evolution of the solar system.
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| What is a "solar cycle"? |
| Solar activity is periodic. A solar cycle (also called a sunspot cycle) is an approximately 11-year period with increasing and decreasing sunspot numbers. Each cycle starts from the time of minimum activity. The cycle numbering system dates back to the eighteenth century and the current solar cycle is cycle 23.
Annual mean sunspot numbers (1900 - 2002)
(Source/Credits: National Geophysical Data Center , US Department of Commerce) |
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| What are "sunspots"? |
Sunspots are dark areas on the Sun's surface with relatively low temperatures (compared with other parts of the Sun) and strong magnetic fields. They normally appear in groups. The number of sunspots is usually taken as an indicator of solar activity. It increases significantly and can reach hundreds at the peak of a solar cycle.
A huge sunspot group may cover an area 13 times or more the Earth's entire surface
(Source/Credits: SOHO (ESA & NASA)) |
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| What is a "solar flare"? |
Solar flare is a violent solar activity. Its occurrence is related to a sudden burst of electromagnetic waves and a vast amount of charged particles (mostly electrons) from the Sun. These electromagnetic waves can affect telecommunications, radio broadcast and navigation system on Earth. Sometimes, charged particles can also endanger the operations of spacecraft and satellites in space, and expose astronauts to higher amounts of radiation.
A solar flare (Source/Credits: Space Environment Center, Boulder, CO, National Oceanic and Atmospheric Administration, US Dept. of Commerce) |
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| What is a "solar wind"? |
The Sun releases tremendous energy. Solar wind refers to this released energy in the form of charged particles at high speed, reaching several hundred kilometres per second. While the magnetic field on the Earth (which traps charged particles encircling the Earth into radiation belts called the Van Allen belts) normally protects our planet from the solar wind, it may be deformed in the event of violent solar wind, resulting in a geomagnetic storm on Earth.
Illustration of the influence on the Earth's magnetic field when solar wind approaches the Earth. White lines represent the solar wind and the blue lines surrounding the Earth represent its magnetic field.
(Source/Credits: SOHO (ESA & NASA)) |
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| What is a "geomagnetic storm"? |
| A geomagnetic storm occurs when a violent solar wind hits the Earth and severely distorts the Earth's magnetic field. Geomagnetic storms can seriously affect radio broadcasts and navigation systems, and paralyze electric grids on Earth. During the great geomagnetic storm in 1989, electricity was suspended for 9 hours in Quebec and a number of American satellites were taken out of service. The last significant geomagnetic storm occurred in October 2003 when intense solar flares erupted from the Sun. Among other incidents, the geomagnetic storm caused a Japanese communications satellite to shut down temporarily. |
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| What are "auroras"? |
Auroras are most commonly visible at high latitudes. They are associated with geomagnetic activity brought about by solar wind. Auroras occur as a result of charged particles (mostly electrons) from the Sun colliding with gas particles in the Earth's atmosphere, producing a glow in different colours. The patterns and shapes of the aurora are related to the flow of charged particles and the magnetic fields. In respect of the auroral colour, oxygen molecules produce green and red colours while nitrogen molecules produce purplish-red and blue colours.
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