Why measure the magnetic field at the Earth's surface? Wouldn't satellites be better suited for space-weather studies?
Satellites and ground-based magnetometers are both important for making measurements of the Earth’s magnetic field. They are not redundant but are instead complementary:
- Satellites provide good geographical coverage for data collection.
- Ground-based magnetometers are much less expensive and much easier to install than satellites. An array of magnetometers provides coverage from numerous locations simultaneously.
Another consideration is that satellites orbit the Earth either inside or above the ionosphere, which is the part of the Earth’s atmosphere that's electrically conductive. Since currents in the ionosphere contribute to the magnetic field, this means that the field measured by a satellite is somewhat different from the field measured at the Earth's surface.
Many of the effects of space weather are most important at the surface of the Earth--where we live--so measurements from ground-based observatories will always play a critical role in space-weather studies.
Learn more: USGS Geomagnetism Program
Related
Do animals use the magnetic field for orientation? Do animals use the magnetic field for orientation?
Yes. There is evidence that some animals, like sea turtles and salmon, have the ability to sense the Earth's magnetic field (although probably not consciously) and to use this sense for navigation.
Do any mass extinctions correlate with magnetic reversals? Do any mass extinctions correlate with magnetic reversals?
No. There is no evidence of a correlation between mass extinctions and magnetic pole reversals. Earth’s magnetic field and its atmosphere protect us from solar radiation. It’s not clear whether a weak magnetic field during a polarity transition would allow enough solar radiation to reach the Earth's surface that it would cause extinctions. But reversals happen rather frequently--every million...
Could magnetic reversals be caused by meteorite or comet impacts? Could magnetic reversals be caused by meteorite or comet impacts?
Although extremely unlikely, it might be possible for a reversal of the Earth's magnetic field to be triggered by a meteorite or comet impact, or even for it to be caused by something more "gentle," such as the melting of the polar ice caps. Self-contained dynamic systems like Earth’s dynamo can have reversals without any outside influence. Reversals of Earth's magnetic field can simply happen...
Is it true that Earth's magnetic field occasionally reverses its polarity? Is it true that Earth's magnetic field occasionally reverses its polarity?
Yes. We can see evidence of magnetic polarity reversals by examining the geologic record. When lavas or sediments solidify, they often preserve a signature of the ambient magnetic field at the time of deposition. Incredible as it may seem, the magnetic field occasionally flips over! The geomagnetic poles are currently roughly coincident with the geographic poles, but occasionally the magnetic...
Are earthquakes associated with variations in the geomagnetic field? Are earthquakes associated with variations in the geomagnetic field?
Electromagnetic variations have been observed after earthquakes, but despite decades of work, there is no convincing evidence of electromagnetic precursors to earthquakes. It is worth acknowledging that geophysicists would actually love to demonstrate the reality of such precursors, especially if they could be used for reliably predicting earthquakes! Learn more: USGS Geomagnetism Program
Related
Do animals use the magnetic field for orientation? Do animals use the magnetic field for orientation?
Yes. There is evidence that some animals, like sea turtles and salmon, have the ability to sense the Earth's magnetic field (although probably not consciously) and to use this sense for navigation.
Do any mass extinctions correlate with magnetic reversals? Do any mass extinctions correlate with magnetic reversals?
No. There is no evidence of a correlation between mass extinctions and magnetic pole reversals. Earth’s magnetic field and its atmosphere protect us from solar radiation. It’s not clear whether a weak magnetic field during a polarity transition would allow enough solar radiation to reach the Earth's surface that it would cause extinctions. But reversals happen rather frequently--every million...
Could magnetic reversals be caused by meteorite or comet impacts? Could magnetic reversals be caused by meteorite or comet impacts?
Although extremely unlikely, it might be possible for a reversal of the Earth's magnetic field to be triggered by a meteorite or comet impact, or even for it to be caused by something more "gentle," such as the melting of the polar ice caps. Self-contained dynamic systems like Earth’s dynamo can have reversals without any outside influence. Reversals of Earth's magnetic field can simply happen...
Is it true that Earth's magnetic field occasionally reverses its polarity? Is it true that Earth's magnetic field occasionally reverses its polarity?
Yes. We can see evidence of magnetic polarity reversals by examining the geologic record. When lavas or sediments solidify, they often preserve a signature of the ambient magnetic field at the time of deposition. Incredible as it may seem, the magnetic field occasionally flips over! The geomagnetic poles are currently roughly coincident with the geographic poles, but occasionally the magnetic...
Are earthquakes associated with variations in the geomagnetic field? Are earthquakes associated with variations in the geomagnetic field?
Electromagnetic variations have been observed after earthquakes, but despite decades of work, there is no convincing evidence of electromagnetic precursors to earthquakes. It is worth acknowledging that geophysicists would actually love to demonstrate the reality of such precursors, especially if they could be used for reliably predicting earthquakes! Learn more: USGS Geomagnetism Program