Introduction to Space Weather

Solar Activity Geomagnetic Activity Space Weather Observations Space Weather Warning Information

Geomagnetic Activity

Geomagnetic Activity images
1. Earth's Magnetosphere
The Earth's magnetic field, which is generated by convection of liquid metals in the outer core of the Earth, plays a pivotal role in shielding the Earth from risks of space weather such as electromagnetic waves and plasma flowing out of the Sun and cosmic rays scattered in space. The boundary between solar wind and the Earth's magnetosphere is called ‘magnetopause’ and, from that boundary toward the interior, the Earth is being protected against dangers of space weather. The shape of the Earth's magnetosphere is not a round dipole due to plasma and interplanetary magnetic field flowing out of the Sun. Instead, it has the shape that the part near the Sun is compressed and the opposite part is long loosened. Because of this, the shape of the Earth's magnetosphere is incredibly variable depending on the status of solar wind. The Earth's magnetosphere is disturbed by space weather conditions. Magnetopause compression and magnetic storms are the two main interruptions.
2. Magnetopause Compression
When a colossal coronal mass ejection and high speed solar wind develop from the Sun, the Earth's magnetic field to shield the Earth from risks of space weather gets more compressed than usual. If the magnetopause gets more compressed than a geostationary orbit does, the geostationary orbit satellite will be exposed to the danger of solar wind, not being able to be protected by the Earth's magnetic field. Also, if a satellite is positioned outside of the magnetopause, the overall operation of the satellite can be affected by communications disruption and damages on the satellite itself by the solar high energy particles.
3. Geomagnetic Storm
A geomagnetic storm is a temporary disturbance of the Earth's magnetism on a large scale all over the world. This disturbance can be for some hours or for some days depending on its scale. The direct cause of the geomagnetic storm is an electric current produced by enormous quantities of plasma injected from the Sun. The electric current is called ‘ring current’ and it drastically decreases the strength of the horizontal component of the Earth's magnetic field. The Kp Index and the Dst Index monitor this strength change. When a geomagnetic storm occurs and significantly decreases the strength of the Earth's magnetic field, it makes a change in electromagnetism of satellite orbits and affects the satellites themselves and their operation. It also causes injection of radiation into the vicinity of polar airways. If this change in the Earth's magnetic field has an impact on the ionosphere, it will disturb GPS signal receptions and telecommunications which can cause interruptions in satellite communications and aeronautical operational communications.