Answer:
Both satellites and ground-based magnetometers are
important for making measurements of the Earth’s
magnetic field. They are not redundant, but are,
instead, complementary. After executing several orbits
of the Earth, satellites can provide good geographical
coverage for data collection. On the other hand,
ground-based magnetometers are much less expensive
than satellites, they are much easier to install and
control than satellites, and, with an array of
magnetometers, they can provide coverage from numerous
locations simultaneously. Another consideration is
that satellites orbit the Earth either inside or above
the ionosphere, the electrically conducting part of
the Earth’s atmosphere. Since currents in the
ionosphere contribute to the magnetic field, this
means that the field measured by a satellite is
somewhat different than the field measured at the
surface. Finally, don’t forget that it is at the
surface of the Earth, where we live, that many of the
effects of space weather are most important, so
measurements from ground-based observatories will
always play a critical role in space-weather studies.
