1. THEMIS Dayside
Lessons learned from the coast phase and the 1st dayside season
Current plans for the 2nd dayside season and the extended phases

2. Orbit for Coast Phase Coast Phase: May-September 2007 Apogee: ~15 RE
Spacecraft Separation:
1-3 RE between leading and trailing S/C
100’s km between inner three S/C
Ideal for studying the structure and dynamics of the magnetopause and boundary layer:
Unique THEMIS contributions:
- Transmission of Hot Flow Anomalies through the bow shock [Eastwood et al., 2008]
- FTE structure and remote sensing {Sibeck et al.; Lui et al.; Liu et al., 2008]
- Thick subsolar LLBL during northward IMF and implications for dual-lobe reconnection [McFadden et al., 2008; Oieroset et al., 2008; Li et al., 2008]

3. Structures of Flux Transfer EventsB C D E A
Sibeck et al. [GRL, 2008]
Lui et al. [2008; JGR}

4. Orbit for Coast Phase Coast Phase: May-September 2007 Apogee: ~15 RE
Spacecraft Separation:
1-3 RE between leading and trailing S/C
100’s km between inner three S/C
Ideal for studying the structure and dynamics of the magnetopause and boundary layer:
Unique THEMIS contributions:
- Transmission of Hot Flow Anomalies through the bow shock [Eastwood et al., 2008]
- FTE structure and remote sensing {Sibeck et al.; Lui et al.; Liu et al., 2008]
- Thick subsolar LLBL during northward IMF and implications for dual-lobe reconnection [McFadden et al., 2008; Oieroset et al., 2008; Li et al., 2008]

5. what we wished we had during the coast phase
Burst data at the magnetopause and bow shock
3s full 3-D electron distributions for the determination of field line topology at the magnetopause and in FTE
24/7 onboard plasma moments
EFI on all spacecraft

6. 1st Dayside Season Dayside Science Phase: May-September 2008
1 S/C at 30 RE: pristine solar wind
1 S/C at 18 RE: solar wind/foreshock
3 S/C at RE: magnetopause/magnetosheath
ideal for studying the response of magnetopause
processes to various solar wind conditions
Unique THEMIS contributions:
MP-Bow Shock crossings 5-min apart due to arrival of solar wind discontinuities
[Hui Zhang, GSFC].
- Extreme MP motion (800 km/s) due to a Hot Flow Anomaly [Jacobsen, Oslo].

7. The deformation and expansion of the MP from 4-spacecraft measurements
MP moved outward by 4.8 RE in 71s
Bulge moved tailward along the MP at 350 km/s

8. what we wished we had during the dayside phase
More magnetopause crossings by the 3 inner spacecraft
Some passes have zero crossings even for THD (12 Re apogee)
THA (Apogee= 11 Re) had much fewer MP crossings
24/7 onboard plasma moments

9. what we wished we had during the dayside phase
More magnetopause crossings by the 3 inner spacecraft
Some passes have zero crossings even for THD (12 Re apogee)
THA (Apogee= 11 Re) had much fewer MP crossings
24/7 onboard plasma moments
More time to look at the data [Sibeck]

10. 2nd Dayside Season (July-Oct 2009)
Apogees=12.9, 11.6, 11.6, 19.5, 30.4 RE
Spacecraft alignment every 8 days
Science Objectives:
SW coupling

11. Extended Phase – 3rd Dayside (Sept-Nov 2010)
Apogee= 12 RE for all (should we go higher?)
24-hour orbital period
DZ= km, DR=1000km
Science Objectives: MHD scale
FTE:
Structure and evolution
Electron energization
Reconnection:
North-south structure
Role of cold magnetospheric plasma Z R
Diffusion region

12. Extended Phase – 4th Dayside (Oct 2011 - Feb 2011)
Apogee= 12 RE for all (should we go higher?)
24-hour orbital period
DZ= km, DR=200km
Science Objectives: Kinetic scale
FTE:
Structure and evolution
Electron energization
Reconnection:
North-south structure Z R
Diffusion region

13. Extended Phase – Dawn-Dusk (between dayside and nightside phases)
3-probes "string-of-pearls":
~100 km – 1 RE separations along-track
Science:
Strong E- field, wave effects
on particle source/losses

14. Dayside Science Phase:
Coast Phase:
FTE structure and remote sensing
Thick LLBL during northward IMF and implications for dual-lobe reconnection
Dayside Science Phase:
Extreme magnetopause motion caused by a Hot Flow Anomaly (HFA)

15. Dayside Science Phase:
Coast Phase:
FTE structure and remote sensing
Thick LLBL during northward IMF and implications for dual-lobe reconnection
Dayside Science Phase:
Extreme magnetopause motion caused by a Hot Flow Anomaly (HFA)

16. Remote Signatures of a FTE Jiang Liu et al. [GRL,2008]
While arrows: Flows
Black arrows: B perturbations
Color Background: Pressure

17. Two-spacecraft direct measurements of LLBL thickness
magnetopause
Oieroset et al. [2008, GRL]
TH-E
ion energy
LLBL
TH-A
ion energy
TH-A
TH-E
LLBL
LLBL
Inner edge of LLBL
TH-E and TH-A bordered the LLBL at 16:32 UT:
-> 0.9 RE (50 ion skin depths) thick at 13.5 MLT !

18. Northward IMF: Evidence for Single and Dual-Lobe Reconnection
Song and Russell [1992]
12.5 MLT
THEMIS E
BGSM
(nT)
M’sphere MP
Ions
(eV)
electrons 0o
electrons
180o
- Uni-directional heated electrons
-> single lobe reconnection
- Bi-directional heated electrons
-> dual lobe reconnection
McFadden et al. [GRL, 2008]
[Onsager et al., 2001; Lavraud et al., 2006]

19. Multispacecraft Observations of single and dual lobe reconnection
TH-B B C E
TH-C
TH-E
All spacecraft detected unidirectional heated magnetosheath electrons further
upstream of the magnetopause and bi-directional electrons closer to the magnetopause
-> the ordering of uni-directional and bi-directional electrons is spatial

20. - Nearly stagnant (different from standard flowing LLBL)
Evidence for deep solar wind entry across the dayside magnetopause during northward IMF with strong By
Oieroset et al. [2008, GRL]
13.5 MLT 16 UT 17
Mixed magnetosheath-magnetospheric ion region earthward of magnetopause
- On closed field lines
- Density ~ 6 cm-3
- Nearly stagnant (different from standard flowing LLBL)

21. - Leads to substantial solar wind entry across the dayside MP
TH-A
TH-E
LLBL
- Dual-lobe reconnection occurs even with a significant IMF By (> Bz)
- Leads to substantial solar wind entry across the dayside MP

22. Sibeck et al. [GRL, 2008] A
|B| B E C
|B| D E A D
|B| C
|B| B
|B|

23. THEMIS Orbits on the Dayside
Coast Phase: May-September 2007
All probes in the same orbit
Prime Science Phase: After September 2007
1 S/C at 30 RE
1 S/C at 18 RE
3 S/C at RE
ideal for studying the response of magnetopause
processes to various solar wind conditions

24. Magnetopause moving at extreme velocity (vN~ 800 km/s)
Caused by a Hot Flow Anomaly
Knut Jacobsen, University of Oslo

25. Magnetopause expanding outward at a speed of 800 km/s
THEMIS D
Ions
electrons VN
VLMN
BLMN

26. The bulk flow is perpendicular to the magnetic field
Vperp
Vpara (km/s)

27. What caused the extremely fast outward expansion of the magnetopause?
Nothing in the pristine solar wind pressure (measured by ACE and Geotail) could account for this motion
THEMIS B, located just upstream of the bow shock, observed a hot flow anomaly and associated drop in the dynamic pressure

28. 5 THD V ACE B THB B Density V_x V_y V_z Temp. Ppla+ Pmag
Ppla+ Pmag+ Pram
Hot Flow Anomaly

29. Interpretation:
The dramatic drop of the upstream pressure associated with a hot flow
anomaly causes the outward expansion of the magnetopause
Conclusion:
Kinetic effects (not present in MHD) can have global consequences on
the magnetosphere

30.
Dayside Science Phase: May-September 2008
1 S/C at 30 RE: pristine solar wind
1 S/C at 18 RE: solar wind/foreshock
3 S/C at RE: magnetopause/magnetosheath
ideal for studying the response of magnetopause
processes to various solar wind conditions

31. Burst Mode (High Resolution) Data at the Magnetopause and Bow Shock
Wave bursts:
- 4 KHz E and B
THEMIS C
BGSM
(nT)
Ions
(eV)
magnetosheath
M’sphere
Density
(cm-3)
Particle Bursts:
3D ion and electron distributions every 3s
128 DC magnetic field vectors/s
256 DC electric field vectors/s

32. 36 Full 3D Ion and Electron Distributions Sampled in the Reconnection Layer!
BGSM
(nT)
Ions
(eV)
VGSM
(km/s)
Reconnection jet
VExB
VExB
V||
Triple counterstreaming ion beams!

33. Summary
The 5-spacecraft THEMIS mission is great for magnetopause investigations
The complete THEMIS data and software is open to the world at:
themis.ssl.berkeley.edu

34. - Cold-dense plasma sheet on closed field lines
- Presence of mixed magnetosheath-magnetospheric electrons in the layer

35. Thickness of CDPS: THEMIS-E and THEMIS-A
magnetopause A E C D
THEMIS-E
ion energy B
THEMIS-A
ion energy
Inner edge of CDPS
THEMIS-E and THEMIS-A borders cold dense plasma sheet at 16:32 UT
→ thickness can be measured
Cold dense plasma sheet was 0.9 RE thick at 16:30 UT, 0.65 Re 30 minutes earlier