Killer electrons in space are now less mysterious


The Sun-Earth connection
 
This composite image shows a SOHO image of the Sun and an artist's impression of Earth's magnetosphere.

Earth’s magnetic field
 
The diagram shows magnetic field lines generated by Earth’s magnetic field. As shown in the picture, the axis of the magnetic field is tilted with respect to Earth’s axis of rotation by 11.5 degrees.

Alignment of satellites on 25 November 2001
 
This animation shows the positions of the satellites during the event on 25 November 2001.

During an opportune alignment that occurred during the recovery phase of a large geomagnetic storm, observations with different instruments from several different points were carried out.

A low frequency type of ULF wave, comparable to a beep every 10 minutes, was recorded continuously for many hours by the CARISMA magnetometer chain in Northern Canada. The waves were picked up by more than a dozen scientific satellites including the four ESA Cluster satellites, NASA’s Polar spacecraft and four of the Geostationary Operational Environmental Satellites (GOES).

Map of simultaneous observations
 
The above is a map of all the observatories on ground, combined with ground footprints of satellite measurements taken on 25 November 2001.

Ionospheric footprints in pink for ESA’s Cluster, in purple for NASA’s Polar and green for the GOES satellites. The projection looks down on the northern hemisphere. The field-of-view of radars of the SuperDARN network is underlined in black. In red, the positions of the CARISMA (University of Alberta, Canada) and SAMNET (Lancaster University, UK) magnetometers chains have been indicated.

12 MLT indicates noon, Magnetic Local Time, or the direction of the Sun, the source of solar wind. 24 MLT indicates the direction opposite to noon, Magnetic Local Time, least affected by solar wind.

Influence of solar wind on Earth's magnetosphere
 
This picture is an artist's impression of the influence of solar wind on Earth's magnetosphere. It results in the creation of instabilities in the magnetic field due to interaction between two superimposed fluids of differing densities and velocities along the magnetopause (Kelvin-Helmholtz surface waves). These surface waves waves create ULF waves, which in turn generate killer electrons. ESA’s Cluster constellation is depicted flying across.



Release date: 30 August 2010