Studying Solar Wind Magnetic Reconnection Events using Cluster

Studying Solar Wind Magnetic Reconnection Events using Cluster.

A.C. Foster1, C.J. Owen1, A.N. Fazakerley1, I. J. Rae1, C. Forsyth1, E. Lucek2, H. Rème3

1. UCL, Mullard Space Science Laboratory, Surrey, UK

2. Imperial College, London, UK

3. 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)

Magnetic rotation at current sheets

Previous study of reconnection event 02/02/2002

Data from Cluster 3 in GSE Total -- X --

Y -- Z --

|B| (

nT)

B (

nT)

|vel

ocity

| (km

/s)

|vel

ocity

| (km

/s)

velo

city

(km

/s)

Universal Time

• Study magnetic reconnection structures

–Test the consistency of the temporal and spatial structure of magnetic reconnection from large scales to small scales

–using the 4 Cluster spacecraft; multi-scale capacity

Aim of Project

Case Study: Event 2/3/2006

|B| (

nT)

B (

nT)

|Vel

ocity

| (km

/s)

Vel

ocity

_x (

km/s

)

Vel

ocity

_z (

nT)

Vel

ocity

_y (

km/s

)

Den

sity

Total -- X -- Y -- Z --

Event 2/3/2006: Consistency

• Consistent with previous results

•The changes in V and B are correlated on one edge of the exhaust and anti-correlated on the other.

•The Walen test has been satisfied.

Event 2/3/2006: Characteristics

• Magnetic rotation over the event: 550

• Angle between two main current sheets: 330

• Low plasma β either side of the event, increase of plasma β during the event

•Alfven speed approximately 43km/s

Event 2/3/2006: Visualisation

Maximum Variance DirectionMaximum Variance Direction

Min

imum

Var

ianc

e D

irect

ion

Min

imum

Var

ianc

e D

irect

ion

10000-10000 0

100

00-1

0000

0

-10000 100000

-100

000

100

00

Courtesy of C. Forsyth, C.Owen, I.J. Rae

CS1 -- CS2 – residual velocity B Field

CS1 -- CS2 – residual velocity B Field

Initial configuration

Configuration with 2% alteration in background

solar wind speed

Event 2/3/2006

|B| (

nT)

8

0

8

0

|B| (

nT)

|B| (

nT)

8

0 0

8

|B| (

nT)

37m30s 40m00s 37m30s 40m00s

37m30s 37m30s40m00s 40m00s

C4C3

C2C1

4

-2

4

44

-2 -2

-2

B (

nT)

B (

nT)

B (

nT)

B (

nT)

Universal Time Universal Time

Universal TimeUniversal Time

Total -- X -- Y -- Z --

Also seen at ACE

• Similar current sheets seen at ACE. Situated approximately 200RE away from the Cluster spacecraft

• Large overall structure (100s RE) but there are small scale differences on the 10,000km scale.

Discussion

Conclusions

• Small scale differences. In the solar wind the picture is of large scale, non patchy events

• Not all of the reconnection events fit the simple gosling bifurcated current sheet with the reconnection outflow between the two.

● 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

Cluster Configuration

2/3/2006