Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause
description
Transcript of Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause
![Page 1: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/1.jpg)
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)
![Page 2: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/2.jpg)
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
![Page 3: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/3.jpg)
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
![Page 4: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/4.jpg)
>10 satellites in near-Earth space
Geotail
Cluster (4 sc)
THEMIS (5 sc)
KAGUYA, & SW monitor
Most of the data are publicly available.
![Page 5: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/5.jpg)
• 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
![Page 6: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/6.jpg)
Shocked solar wind
Magnetopause 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.
![Page 7: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/7.jpg)
• How does it start?
• How does it evolve?
• What feedbacks/consequences does it bring about?
What we can do with available data
![Page 8: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/8.jpg)
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
![Page 9: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/9.jpg)
TotalPvv
)(
Total-P perturbation in the vortex
streamline
Force balance
![Page 10: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/10.jpg)
Total-P perturbation in the vortex
• Dominant-mode period ~200 s (Wavelength ~6 Re)• Power also at ~400 s: Beginning of vortex pairing?
![Page 11: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/11.jpg)
• Spatial initial value problem• Assumptions: MHD, d/dt =0, 2D, & B along invariant axis z.
Dominant-mode wavelength ~6 Re
Vortex structurefrom 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.
![Page 12: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/12.jpg)
• 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
![Page 13: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/13.jpg)
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
![Page 14: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/14.jpg)
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.
![Page 15: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/15.jpg)
Reconnection @ the dayside boundary
0
BVV HT
B tensionCentrifugal 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?
![Page 16: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/16.jpg)
• How does it start?
• How does it evolve?
• What feedbacks/consequences does it bring about?
What we can do with available data
![Page 17: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/17.jpg)
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 minBL
Ion-scale CSs at the edge of KH vortices
BL
![Page 18: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/18.jpg)
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
BL
jM
VL
20 sec
Plasma Sheet Sheath
VL
Consistent with reconnection triggered in the thin CS at the vortex edge
![Page 19: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/19.jpg)
closest to Earth0600 UT
1000 UT
X (sunward)
Y (dusk)
THEMIS string-of-pearls observation of a dayside boundary layer (BL) @16 MLT
8 June 2007
![Page 20: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/20.jpg)
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 Xby ~1.5 Re.
↓BL width ~0.5 Re40 min
closest to Earth
Eriksson et al., JGR, 2009
![Page 21: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/21.jpg)
• Bipolar BN, at BL-to-sheath transitions, i.e., at the sunward-side edge of the surface wave.
Bipolar B oscillations on the surface wave
BN
80 min
![Page 22: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/22.jpg)
streamline
B-field
streamline
Recovery of 2D MHD structureSonnerup & Teh, JGR, 2008
• Magnetic island & small vortex between two large-scale vortices
• Local reconnectionleading to the magnetic island formation
sheath side
Plasma sheet
N
T
![Page 23: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/23.jpg)
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.
![Page 24: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/24.jpg)
Geotail TH-BTH-C
TH-A,D,E
Cluster
An ideal satellite distribution in 2008
![Page 25: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/25.jpg)
SummaryWith 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.
![Page 26: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/26.jpg)
![Page 27: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/27.jpg)
Nakamura et al., 2004
Matsumoto & Hoshino, 2004
(Inverse-) cascade
Miura, PoP, 1997
![Page 28: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/28.jpg)
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???
![Page 29: Cutting-Edge Results from Formation Flying Observations near Earth’s magnetopause](https://reader035.fdocuments.net/reader035/viewer/2022062518/5681458c550346895db2753b/html5/thumbnails/29.jpg)
Anisotropy in ion V distribution
sheath
Plasma sheet
Perp heating: consistent with diffusive transport via KAW (Johnson & Cheng, 2001)