Studying Solar Wind Magnetic Reconnection Events using the Cluster 4-point
Measurement Capability
A.C. Foster1, C.J. Owen1, A.N. Fazakerley1, C. Forsyth1 E. Lucek2, H. Rème3
1. UCL, Mullard Space Science Laboratory, Surrey, UK2. Imperial College, London, UK3. CNRS, IRAP, Toulouse, France
UCL DEPARTMENT OF SPACE & CLIMATE PHYSICSMULLARD SPACE SCIENCE LABORATORY
Magnetic Reconnection Observables
•First study of solar wind reconnection made by Gosling, 2005.•Bifurcated current sheet•Magnetic field rotations over current sheets•Enhanced plasma jet / reconnection exhaust
Reconnection Exhaust
Reconnection Exhaust
Adapted from Gosling, J.T. (2005)
Inflow
Inflow
Inflow
Inflow
Magnetic Field LinesCurrent Sheet
A1 A2
B
B
Phan,T.D (2006)
•Unconstrained boundary conditions•Multiple spacecraft observations •Time scales ≤ few hours•Length scales ~100s RE
•Different plasma conditions than frequently studied (e.g. Magnetopause / magnetotail)
Advantages in studying Reconnection in the Solar Wind
Earth
ACE
Cluster
Wind
Exhaust
To Sun
Jet
Jet
BM
Solar Wind
Direction
Phan,T.D (2006)
131211109
5
0
-10
-5
20
0
-20
-40
-340
-350
-360
32m00s 34m00s02h 30m00s
|B| (
nT)
B (n
T)
Ion
Velo
city
(km
s-1)
Magnetic rotation at current sheets
Previous study of reconnection event 02/02/2002
Data from Cluster 3 in GSE
Total -- X --Y -- Z --
Phan,T.D (2006)
131211109
5
0
-10
-5
20
0
-20
-40
-340
-350
-360
32m00s 34m00s02h 30m00s
|B| (
nT)
B (n
T)
Ion
Velo
city
(km
s-1)
Magnetic rotation at current sheets
Previous study of reconnection event 02/02/2002
Data from Cluster 3 in GSE
Total -- X --Y -- Z --
Using Cluster’s 4 point-measurement capability it was not possible to reproduce these results.
Small scale features (e.g. Ripples in the current sheets) in these reconnection events?
•My study will initially look at the magnetic reconnection structures on a relatively small scale using the 4 Cluster spacecraft.
•This is in order to test more detailed reconnection models: is it possible to predict the outflow conditions given the inflow conditions?
•The extended study will look at the events on a larger scale using ACE and Wind.
Aim of Project
7
53h30m
6
6
40
20
0
52h30m 53h00m 54h00mUT
|B|
(nT)
Ion
Velo
city
En
hanc
emen
t (k
m s
-1)
Total -- X --Y -- Z --
Reconnection Exhaust
Magnetic Field and Ion Velocity Enhancement (GSE)
Cluster 3
54
2
-2
18
16
14
12
B (n
T)D
ensi
ty
(par
ticle
s cm
-3)
7
53h30m
6
6
40
20
0
52h30m 53h00m 54h00mUT
|B|
(nT)
Ion
Velo
city
En
hanc
emen
t (k
m s
-1)
Total -- X --Y -- Z --
Reconnection Exhaust
Magnetic Field and Ion Velocity Enhancement (GSE)
Cluster 3
54
2
-2
18
16
14
12
B (n
T)D
ensi
ty
(par
ticle
s cm
-3)
• Inflow 1 speed = 48kms-1
• Inflow 2 speed = 42kms-1
• Average exhaust speed = 45kms-
1
Minimum Variance Technique
•Results were consistent between spacecraft.
•In all cases:
•Normal direction vector taken as minimum variance direction
Current Sheet Orientation Determination
Sheet 1 Sheet 2
Earth
To the Sun
X-Line
Sheet 1Sheet 2
Solar Wind Direction
4min
int
Sheet 1 Sheet 2
Earth
To the Sun
X-Line
Sheet 1Sheet 2
Solar Wind Direction
X-line Direction•Cross product of the normal direction vector of each current sheet•Point on plane – position that Cluster 3 encounterssheet.•Right handed system for each current sheet
Assumption made: Current sheets can be
considered as flat planes
Current Sheet Co-ordinate System Determination
•Average velocity lies between current sheets•Perpendicular to X-direction
Exhaust Velocity Determination
Sheet 1
Reconnection Exhaust
Sheet 2
X-Point Cluster 3 trajectory through exhaust
• Comparing the data to more detailed reconnection models
• Looking at the small scale features in these large scale structures
• Comparing the Cluster data with data from ACE and Wind which also saw the event.
Ongoing Work
● Baumjohann, W. (1997): Wolfgang Baumjohann and Rudolf A. Treumann. Basics of Space Plasma Physics. Imperial College Press, 1997.
● Priest, E. R. (1984): Priest, E. R. (1984), Solar Magneto-Hydrodynamics, Geophys. Astrophys.Monogr. Ser., Springer, New York.
● Gosling, J.T (2005): J.T. Gosling, R.M. Skoug, D.J. McComas, C.W. Smith, J. Geophys. Res. 110, A01107, 2005
● Phan, T. D. (2006): T. D. Phan, J. T. Gosling, M. S. Davis, R. M. Skoug, M. Øieroset, R. P. Lin, R. P. Lepping, D. J.McComas, C. W. Smith, H. Reme, and A. Balogh. A magnetic reconnection X-line extending more than 390 Earth radii in the solar wind. Nature, 439:175–178, January 2006.
● Gosling (2007): J. T. Gosling, S. Eriksson,L. M. Blush,T. D. Phan,J. G. Luhmann,D. J. McComas,R. M. Skoug,M. H. Acuna,C. T. Russell, and K. D. Simunac. Five spacecraft observations of oppositely directed exhaust jets from a magnetic reconnection X-line extending > 4.26 106km in the solar wind at 1 AU
References
UCL DEPARTMENT OF SPACE & CLIMATE PHYSICSMULLARD SPACE SCIENCE LABORATORY
UCL DEPARTMENT OF SPACE & CLIMATE PHYSICSMULLARD SPACE SCIENCE LABORATORY
Minimum Variance Analysis
Cluster Configuration
B (n
T)
C1
C2
C3
C4
UT
Total -- X --Y -- Z --
Reconnection Event Interval
Magnetic Field (GSE)
Max R = 0.92 (x)Min R = 0.75 (y)
Max R = 0.99 (z)Min R = 0.76 (y)
Max R = 0.94 (z)Min R = 0.77 (y)
Max R = 0.99 (x)Min R = 0.36 (y)
Max R = 0.99 (z)Min R = 0.73 (y)
Max R = 0.99 (y)Min R = 0.58 (x)
4
0
-4
4
0
-4
4
0
-4
4
0
-4
52m00s 52m30s 53m00s 53m30s 54m00s 54m30s 55m00s
B (n
T)
C1
C2
C3
C4
UT
Total -- X --Y -- Z --
Reconnection Event Interval
Magnetic Field (GSE)
7654
7654
7654
7654
52m30s 53m00s 53m30s 54m00s 54m30s