- 4516 - EARTH'S MAGNETIC FIELD? - When I got my first boy scout compass I became aware that Earth's magnetic field pointed towards the North Pole. However, today the needle is changing. The Earth's changing, irregular magnetic field is causing headaches for polar navigation.
------------------------------------ 4516 - EARTH'S MAGNETIC FIELD?
- Changes in the Earth's global magnetic
field over six months in 2014 as measured by the European Space Agency's
three-satellite Swarm constellation.
The Earth's liquid molten outer core, composed mostly of iron and
nickel, exerts an electromagnetic field extending from the north and south pole
that protects the planet from harmful solar particle radiation.
-
- Fluctuations in the strength of Earth's
magnetic field is caused by daily changes in solar wind structure and
intermittent solar storms. This can
impact the use of geomagnetic field models which are essential for navigation
in satellites, planes, ships, cars, and my boy scout compass..
-
- Magnetic field models differ based on the
location of data collection, either on or near the Earth's surface or low Earth
orbiting satellites. Past research has attributed model differences to space
weather activity levels, but a recent analysis of six years of Earth and
satellite magnetic field models found model discrepancies are also driven by
modeling errors rather than geophysical phenomena alone.
-
- The research team assessed differences
between observations from the Swarm mission's low-Earth orbit satellites and a
Earth magnetic field model, the thirteenth generation of the International
Geomagnetic Reference Field or “IGRF-13”. They focused on differences during
low to moderate geomagnetic conditions which encompasses 98.1% of the time
between the years 2014 and 2020.
-
- Satellite observations collected at
different locations above Earth are sensitive to magnetic field fluctuations,
whereas Earth magnetic field models use observations to estimate the Earth's
internal magnetic field without accounting for the influence of solar storms.
Internal magnetic field models like IGRF-13 are used to track changes in the
Earth's magnetic poles, like the North pole's shift of about 45 kilometers
north-northwest each year.
-
- Understanding these large differences are
important for satellite operation when using IGRF-13 as a reference and for
research on the physics of the Earth's magnetosphere, ionosphere and
thermosphere.
-
- Model uncertainty was highest in the north
and south polar regions, and a statistical analysis revealed that the asymmetry
between the north and south polar regions was a major factor driving model
differences.
-
- We often assume a nearly symmetrical
magnetic field between the northern and southern polar regions, but they are
actually very different. The two
geographic poles map to different geomagnetic coordinates. The North pole maps
to around 84° Magnetic Latitude (MLAT) and 169° Magnetic Longitude (MLON) and
the South pole maps to around −74° MLAT and 19° MLON.
-
- The Swarm satellites' polar orbit track
creates a sampling bias with a high concentration of measurements around the
geographic poles, which exacerbates the model differences. Understanding that what has been attributed
to geophysical disturbances is really due to the asymmetry of the Earth's
magnetic field will help us better create geomagnetic field models as well as
help with satellite and aviation navigation.
-
- Another issue that is causing the
navigation community concern, is that the polar magnetic field has been
changing rapidly over the past decade or so.
This adds further complexity to creating accurate magnetic field models
and my boy scout compass.
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-
June 30, 2024 EARTH'S
MAGNETIC FIELD? 4516
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