1. Cutting-Edge Results from Formation Flying Observations Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause Hiroshi Hasegawa （長谷川 洋） ISAS/JAXA Meeting on “Opportunity for Collaboration on ERG and SCOPE Missions & Community Input” (16-17 March 2009)

2. We hope to reach a complete understanding of fundamental physical processes (reconnection, shock, & turbulence) in the Plasma Universe. How does it start? How does it evolve? What feedbacks/consequences does it bring about? In the future SCOPE era

3. As data analysts or theorists, We should prepare well enough for the future missions, by learning from “currently” available data from on-going multi-satellite missions. We should not just wait

4. >10 satellites in near-Earth space Geotail Cluster (4 sc) THEMIS (5 sc) KAGUYA, & SW monitor Most of the data are publicly available.

5. How does it start? How does it evolve? What feedbacks/consequences does it bring about? As a demonstration, Here we address the Kelvin-Helmholtz instability (KHI) that can be excited at the magnetopause (it = KHI). What we can do with available data

6. Shocked solar wind M agnetopause KHI Hasegawa et al., 2004; Nakamura et al., 2004 Kelvin-Helmholtz vortices may play a role in transport of solar wind into the magnetosphere, in other words, anomalous transport of collision-less plasma.

7. How does it start? How does it evolve? What feedbacks/consequences does it bring about? What we can do with available data

8. C1 electron C1 ion density Cluster event on 20 Nov 2001 (19 LT) (Hasegawa et al., 2004; Chaston et al., 2007; Foullon et al., 2008) temperature velocity magnetic field

9. Total-P perturbation in the vortex streamline Force balance

10. Total-P perturbation in the vortex Dominant-mode period ~200 s (Wavelength ~6 Re) Power also at ~400 s: Beginning of vortex pairing?

11. Spatial initial value problem Assumptions: MHD, d/dt =0, 2D, & B along invariant axis z. Dominant-mode wavelength ~6 Re Vortex structure from Grad-Shafranov-like reconstruction of streamlines (Sonnerup et al., 2006; Hasegawa et al., 2007) C1 C3 Two vortices within one dominant-mode wavelength. Breakup of a parent MHD-scale vortex (cascade)? The KHI seen by Cluster was fully in a nonlinear phase, characterized by merging/breakup (inverse- cascade/cascade) of the vortices.

12. How does it start? How does it evolve? What feedbacks/consequences does it bring about? The observed KHI wavelength (~6 Re) is much longer than predicted by theory. Why??? What we can do with available data

13. Simultaneous observations of the magnetopause at different longitudes Cluster @ 19 MLT (X ~ -4 Re) saw nonlinear KH wave. Geotail @ 15 MLT (X ~ +8 Re) saw what??? Geotail Cluster

14. Fluctuation in the dayside boundary Magnetic fluctuations had a period similar to that of the KH waves. Geotail Cluster The KHI was generated by the mechanism that generated the magnetic fluctuations.

15. Reconnection @ the dayside boundary B tension Centrifugal force Walén relation satisfied (Sonnerup et al., 1987) Reconnection (or sheath fluctuations) generated the seed perturbations for the KHI excitation. Reconnection generated the B fluctuations?

16. How does it start? How does it evolve? What feedbacks/consequences does it bring about? What we can do with available data

17. 4-satellite timing method → Vn ~ 80 km/s Crossing took ~3 sec. Current Sheet thickness ~250 km = 2-3 times ion inertia length (~100 km) 1 min converging vortex flow 25 min BLBL Ion-scale CSs at the edge of KH vortices BLBL

18. Reconnection signatures in the thin CS Bifurcated Current Sheet Bn < 0 Outflow jet (  V = 60 km/s ~ Alfven speed in sheath = 90 km/s) Ne BLBL jMjM VLVL 20 sec Plasma Sheet Sheath VLVL Consistent with reconnection triggered in the thin CS at the vortex edge

19. closest to Earth 0600 UT 1000 UT X (sunward) Y (dusk) THEMIS string-of-pearls observation of a dayside boundary layer (BL) @16 MLT 8 June 2007

20. THEMIS obs. of a dayside BL Surface waves activity with 1-2 min period Simultaneous BL encounters by 2-4 SC, at several times. SC separated in X by ~1.5 Re. ↓ BL width ~0.5 Re 40 min closest to Earth Eriksson et al., JGR, 2009

21. Bipolar B N, at BL-to-sheath transitions, i.e., at the sunward-side edge of the surface wave. Bipolar B oscillations on the surface wave BNBN 80 min

22. streamline B-field streamline Recovery of 2D MHD structure Sonnerup & Teh, JGR, 2008 Magnetic island & small vortex between two large-scale vortices Local reconnection leading to the magnetic island formation sheath side Plasma sheet N T

23. What we can do with available data How does it start? How does it evolve? What feedbacks/consequences does it bring about? Nonlinear KHI growth can lead to the formation of thin (ion inertia-length scale) current sheets and magnetic islands.

24. Geotail TH-B TH-C TH-A,D,E Cluster An ideal satellite distribution in 2008

25. Summary With currently available satellite data, How it starts & how it evolves can partly be addressed for some processes/phenomena. We can get some glimpse of what consequences arise from it. Feedback & fast processes (electron dynamics, etc.) will be pursued by SCOPE. Prepare for the future, by analyzing data from on-going missions, or by developing & testing novel data analysis techniques.

27. Nakamura et al., 2004 Matsumoto & Hoshino, 2004 (Inverse-) cascade Miura, PoP, 1997

28. Nakamura et al., GRL, 2006 Interpretation of THEMIS & Cluster events Thin current sheet can form at the edge of KH vortex where the CS is compressed, and may become subject to reconnection. KH-induced reconnection can lead to the flux rope formation. Can it lead to large-scale plasma transport???

29. Anisotropy in ion V distribution sheath Plasma sheet Perp heating: consistent with diffusive transport via KAW (Johnson & Cheng, 2001)