Swedish National Graduate School of Space Technology Cluster multi-spacecraft measurements:...
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Swedish National Graduate School of Space Technology
Cluster multi-spacecraft measurements: applications on transition layer development and location of the
reconnection site
Lars-Göran Westerberg1, Hans O. Åkerstedt1 and Hans Nilsson2
1Division of Fluid Mechanics
Luleå University of Technology2Swedish Institute of Space Physics, Kiruna
Swedish National Graduate School of Space Technology
Outline
• Introduction
- Objective of present paper.- The magnetosphere and Cluster spacecraft orbit.- Magnetic reconnection and the Cluster mission.
• Cluster in situ measurements coupled with a 3D analysis.
• Conclusions and future work.
Swedish National Graduate School of Space Technology
Objective of present paper
Combine results from a 3D analysis covering the plasma flow near a reconnection site with in situ Cluster observations, in order to study:
Development of the magnetopause transition layer.
Values on the anomalous transport coefficients (ν + ηd), where ν is the kinematic viscosity and ηd the magnetic diffusivity.
Also estimate the distance from the observing spacecraft to the reconnection site.
Swedish National Graduate School of Space Technology
The magnetosphere and Cluster spacecraft orbit
Swedish National Graduate School of Space Technology
Magnetic reconnection
• Main mechanism for the transfer of mass and momentum in space and astrophysical applications.
• Magnetic field seize to be frozen in the plasma. The resistivity is locally finite.
Credit: European Space Agency
Swedish National Graduate School of Space Technology
Results from 3D analysis
To be coupled with data from the Cluster spacecraft*
*Grammatical notation: One spacecraft, several spacecraft
Swedish National Graduate School of Space Technology
y
z
x
Cluster spacecrafts
Magnetopause
~8 RE
~9 RE
Earth
Bow shock
zx
Magnetosheath
y
Sub-Solar point
a
b
c
sc1
sc4
sc3
-0.5 0 0.5 1-0.1
0
0.1
0.2
0.3
y (RE)
z
(RE)
-0.5 0 0.5 1-0.1
0
0.1
0.2
0.3
x (RE)
z
(RE)
sc1
sc4
sc3
sc1
sc4
sc3
Joint position on the 13th of January 2002
Sub-solar region
Swedish National Graduate School of Space Technology
Cluster sc1 data during 14:50-15:50
Time (UT)
Swedish National Graduate School of Space Technology
70
90
110
130
150
170
190
210
-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5-30
-25
-20
-15
-10
-5
0
5
10
15
Results from Cluster and theory
x (RE)
B (
nT)
V (
km/s
)
Swedish National Graduate School of Space Technology
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.80
0.5
1
1.5
2
2.5
3
3.5
4
(distance to reconnection line)
y
z Z
x
UHT
reconnection line
Z0
satellite
a
Z (Distance from reconnection site)
b
δ(Z)
sc4 sc3 sc1
Location of reconnection line and transition layer development
Solid line: Theoretical expression. Cross marks: Measured thickness by respective spacecraft
Swedish National Graduate School of Space Technology
Conclusions and future work
Maximum value of anomalous transport coefficients ~ 104 km2/s.
Cluster satellites pass the magnetopause ~ 0.5 RE
from the reconnection site.
Magnetopause transition layer increases when moving away from the reconnection site.
Enhance the data analysis – statistical study of magnetopause crossings.
Develop the theory by including Hall terms as non-ideal effects.
Swedish National Graduate School of Space Technology
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