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News December 2001

Movies
 Animation depicting various aspects of the
Sun-Earth system...the Sun, the corona and solar wind, space plasmas
flowing around the magnetosphere of Earth and funneling into the system
in places.  Cluster is designed to make multi-point measurements of
those flowing plasmas.
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Animation depicting various aspects of the Sun-Earth system...the Sun, the corona and solar wind, space plasmas flowing around the magnetosphere of Earth and funneling into the system in places. Cluster is designed to make multi-point measurements of those flowing plasmas. Courtesy of the European Space Agency

Animation of the Cluster spacecraft as they glide
over Earth's northern lights for a view.
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Animation of the Cluster spacecraft as they glide over Earth's northern lights for a view. Courtesy of the European Space Agency

Animation depicting the Cluster quarter of
spacecraft flying in formation and viewing Earth's magnetosphere from
different angles as it undulates in response to a space storm.
(1.6M)
Animation depicting the Cluster quarter of spacecraft flying in formation and viewing Earth's magnetosphere from different angles as it undulates in response to a space storm. Courtesy of the European Space Agency

Still Images
Artist's conception of the black aurora and its associated electric currents, as observed by the four Cluster
spacecraft.
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Artist's conception of the black aurora and its associated electric currents, as observed by the four Cluster spacecraft. Courtesy of the European Space Agency
View of the aurora over the Northern Hemisphere from the Polar
spacecraft
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View of the aurora over the Northern Hemisphere from the Polar spacecraft Courtesy of VIS/University of Iowa
View of the aurora over both poles of Earth (known as
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View of the aurora over both poles of Earth (known as "conjugate aurora") from the Polar spacecraft Courtesy of VIS/University of Iowa
Location and configuration of the Cluster satellite formation
passing over the northern hemisphere auroral oval between 4:20 and 4:40
UT on January 14, 2001, in the recovery phase of a weak substorm,
peaking at 04:00 UT. a) The nightside auroral oval as observed by the UV
imager on the IMAGE satellite at 04:30 UT. The ionospheric projection of
the Cluster orbit (between 4:20 and 04:45 UT) is shown by the white line
intersecting the auroral oval. b) Relative positions and time
differences between the Cluster 1, 2, and 4 spacecraft with respect to
the reference Cluster 3 (Samba) in a plane transverse to the magnetic
field. The four Cluster spacecraft are aligned nearly as pearls on a
string, with the separation transverse to the velocity vector being
small, and follow in the sequence 1-3-2-4.
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Location and configuration of the Cluster satellite formation passing over the northern hemisphere auroral oval between 4:20 and 4:40 UT on January 14, 2001, in the recovery phase of a weak substorm, peaking at 04:00 UT. a) The nightside auroral oval as observed by the UV imager on the IMAGE satellite at 04:30 UT. The ionospheric projection of the Cluster orbit (between 4:20 and 04:45 UT) is shown by the white line intersecting the auroral oval. b) Relative positions and time differences between the Cluster 1, 2, and 4 spacecraft with respect to the reference Cluster 3 (Samba) in a plane transverse to the magnetic field. The four Cluster spacecraft are aligned nearly as pearls on a string, with the separation transverse to the velocity vector being small, and follow in the sequence 1-3-2-4. Courtesy of the European Space Agency
Upward accelerated electron beam: evolution of energy and
width. Time energy spectrograms show electrons moving anti-parallel to
the magnetic field as measured by the PEACE instrument between 4:30 and
4:40 UT. The arrowheads at the top of the panels indicate the encounters
with the bipolar electric field structures, occurring at a transition
between two characteristically different electron populations, a
high-energy isotropic electron population characteristic of the central
plasma sheet to the south, and a lower-energy population characterized
by intermittent, bi-directional, and field-aligned electron bursts.
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Upward accelerated electron beam: evolution of energy and width. Time energy spectrograms show electrons moving anti-parallel to the magnetic field as measured by the PEACE instrument between 4:30 and 4:40 UT. The arrowheads at the top of the panels indicate the encounters with the bipolar electric field structures, occurring at a transition between two characteristically different electron populations, a high-energy isotropic electron population characteristic of the central plasma sheet to the south, and a lower-energy population characterized by intermittent, bi-directional, and field-aligned electron bursts. Courtesy of the European Space Agency
Acceleration structures within the auroral current circuit.
This schematic picture shows a negatively charged potential structure
representative of the aurora (left) and a positively charged potential
structure representative of the auroral return current (right). The two
branches of the equipotential contours close at typical altitudes of
5000-8000 km in the upward current region above the aurora and at
1500-3000 km in the auroral return current region, respectively, above
which they extend to very high altitudes along the geomagnetic field,
forming the characteristic U-shape. Together with the ionospheric
closure current and the magnetospheric generator these form the complete
auroral current circuit.
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Acceleration structures within the auroral current circuit. This schematic picture shows a negatively charged potential structure representative of the aurora (left) and a positively charged potential structure representative of the auroral return current (right). The two branches of the equipotential contours close at typical altitudes of 5000-8000 km in the upward current region above the aurora and at 1500-3000 km in the auroral return current region, respectively, above which they extend to very high altitudes along the geomagnetic field, forming the characteristic U-shape. Together with the ionospheric closure current and the magnetospheric generator these form the complete auroral current circuit. Courtesy of the European Space Agency

Artist's schematic of the position/observations of
the four Cluster spacecraft as they passed through the electric currents
of the black aurora.
(1.15M)
Artist's schematic of the position/observations of the four Cluster spacecraft as they passed through the electric currents of the black aurora. Courtesy of the European Space Agency



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