1. 真夏の磁気圏界面磁束乗換現象 Flux transfer events and solar wind energy entry at Earth’s magnetopause Hiroshi Hasegawa （長谷川 洋） ISAS/JAXA Contributers: the ISSI team, J. P. McFadden (SSL, UCB), & V. Angelopoulos (IGPP, UCLA) STP seminar on 19 May 2010

2. Active objects (emitter) –Pulsars (spin period) –Sun: solar wind (½ spin period ~13.5 day at Earth) –Jupiter: radio wave, B induced in Europa, etc. (~spin period ~10-11 hours) Passive objects (receiver) –Earth’s magnetosphere: semi-annual variation (½ revolution period =0.5 year) Magnetic dipole tilt & periodic phenomena From Wikipedia

3. 13.5-day period in the solar wind Mursula & Zieger (JGR, 1996) V SW T SW N SW Kp Due to magnetic latitude dependence of the solar wind

4. Russell-McPherron effect at Earth McPherron et al., 2009 Semi-annual variation of geomagnetic activity Russell & McPherron, 1973

5. Outline Relationship between models of flux transfer events (FTEs) and solar wind energy entry. Possible role of an FTE generation process (multiple X-line reconnection) in the semi- annual variation of geomagnetic activity. Evidence for FTEs resulting from multiple X- line reconnection: THEMIS observations.

6. X Y Z Flux Transfer Event (FTE) at magnetopause B L: north-south BMBM BNBN |B| Bipolar B N & enhanced |B|. Believed to result from transient, localized, or multiple X-line reconnection, or their combination. Russell & Elphic, 1978

7. Models of FTE generation Localized & transient reconnection Russell & Elphic, 1978 Transient but ~2D reconnection Scholer, 1988; Southwood et al., 1988 Multiple X-line reconnection Lee & Fu, 1985; Sonnerup, 1987 Little is known about the FTE generation processes and effects on magnetospheric phenomena.

8. Differences among FTE models: spatio- temporal properties of reconnection TemporalSpatialTopology change Rate ( E RX ), continuity, and/or duration of reconnection. Length ( L ) of X- line. Number of X-line (not all X-lines change magnetic topology!). Time-averaged B flux per unit length Time-averaged B flux integrated over the tail width Closed to Open? (leading to transport and storage of B flux into the tail) Key factors to SW energy entry into the tail

9. Raeder, AnnGeo, 2006 FTE formation under large dipole tilt Sequential Multiple X-line Reconnection: SMXR

10. In the SMXR model, 1. Initial X forms between the subsolar point and B equator. 2. It moves into the winter hemisphere, and becomes inactive. 3. New X forms near the location of the old X formation, generating a flux rope between the two Xs. 1 23

11. Without dipole tilt, continuous topology change from closed to open can occur. Efficient energy entry With dipole tilt, new X-line first has to consume already open field lines to reconnect closed field lines. Less efficient energy entry

12. Russell & McPherron, 1973 Seasonal dependence of geomag activity Less efficient energy entry from SMXR may explain part of the lower geomag activity for larger dipole tilt.

13. FTEs (some bipolar, some tripolar) A, B, C, D, E THEMIS 2007-06-14 (10, 4, -2) Re in GSM

14. Evidence of FTE from MXR near solstice ~B N THEMIS data on 2007-06-14 (10, 4, -2) Re in GSM Northward then southward jets FTE between the jets

15. 2D field map recovered from TH-C & -D data Grad-Shafranov reconstruction (Hau & Sonnerup, 1999; Hasegawa et al., 2005) - Flux rope moving southward: V HT =(-46, 11, -103) km/s between the two jets - Elongation along N - Enhanced Bz & p consistent with compression by the two converging jets ~MP normal South-east ⇔ subsolar

16. B tension Centrifugal force Reconnection northward of the FTE Walén relation (Sonnerup et al., 1987) Walén test Negative slope ： consistent with jet southward of X, where flows are anti-field- aligned in the HT frame.

17. Particle signatures of reconnection on both sides of the FTE PA ~0 deg ion PA ~180 deg ion PA ~0 deg ele PA ~180 deg ele THB on sheath side saw both || and anti-|| electron beams, indicating that field lines are reconnected on both south and north sides of the FTE. FTE

18. The FTE is consistent with SMXR model Multiple X-line reconnection near solstice. Flux rope traveling into the winter hemisphere. Subsolar X-line activated later than southward X. South-east ⇔ subsolar

19. Summary Relationship between models of flux transfer events (FTEs) and solar wind energy entry. Possible role of an FTE generation process (multiple X-line reconnection) in the semi- annual variation of geomagnetic activity. Evidence for FTEs resulting from multiple X- line reconnection: THEMIS observations near solstice.

20. An addition: correct interpretation of Lui et al. (JGR, 2008) Three serious mistakes: The coordinate system is wrong. The chosen flux rope orientation is not optimal. Magneto-hydrostatic force balance is not at all satisfied in their composite map.

21. In p.4 of Lui et al. (GRL, 2008): In p.6-7 of Lui et al. (JGR, 2008): Coordinate system This should be “GSE”.

22. Orientation of flux rope (z) axis A spurious magnetic island, resulting from incorrect choice of the flux rope axis Our result

23. Recovered structure is not in a magneto-hydrostatic equilibrium No sufficient pressure gradient to balance the spurious kink (tension) of the field lines. If the map was right, the GS method could not and should not be used.

24. GSM comp. of the GS axes X = (0.3991, -0.8363, 0.3758) Y = (0.7389, 0.5361, 0.4082) Z = (-0.5428, 0.1148, 0.8320) VHT = (-102.8, 124.9, 22.1) km/s VHT*x = -137.2 km/s Our more reasonable result

25. TH-A ion Pitch angle (PA) ~0 deg PA ~180 deg Escaping Msp ions (SC north of X) electron PA ~0 deg PA ~180 deg Bi-dir ele (multiple X) Top: sheath ions Bottom: MSBL

26. References: Hasegawa, H., et al. (2005), Optimal reconstruction of magnetopause structures from Cluster data, Ann. Geophys., 23, 973-982. Hau, L.-N., and B. U. O. Sonnerup (1999), Two-dimensional coherent structures in the magnetopause: Recovery of static equilibria from single-spacecraft data, JGR, 104, 6899-6917. Lee, L. C., and Z. F. Fu (1985), A theory of magnetic flux transfer at the Earth ’ s magnetopause, GRL, 12, 105-108. Lui, A. T. Y., et al. (2008), Reconstruction of a magnetic flux rope from THEMIS observations, Geophys. Res. Lett., 35, L17S05, doi:10.1029/2007GL032933. Lui, A. T. Y., et al. (2008), Reconstruction of a flux transfer event based on observations from five THEMIS satellites, J. Geophys. Res., 113, A00C01, doi:10.1029/2008JA013189. McPherron, R. L., et al. (2009), Role of the Russell-McPherron effect in the acceleration of relativistic electrons, JASTP, 71, 1032-1044. Mursula, K., and B. Zieger (1996), The 13.5-day periodicity in the Sun, solar wind, and geomagnetic activity: The last three solar cycles, J. Geophys. Res., 101(A12), 27,077-27,090. Raeder, J. (2006), Flux Transfer Events: 1. generation mechanism for strong southward IMF, Ann. Geophys., 24, 381-392. Russell, C. T., and R. L. McPherron (1973), The magnetotail and substorms, Space Sci. Rev., 15, 205-266. Russell, C. T., and R. C. Elphic (1978), Initial ISEE magnetometer results: magnetopause observations, Space Sci. Rev., 22, 681-715. Scholer, M. (1988), Magnetic flux transfer at the magnetopause based on single X-line bursty reconnection, Geophys. Res. Lett., 15, 291-245. Sonnerup, B. U. O. (1987), On the stress balance in flux transfer events, JGR, 92(A8), 8613-8620. Sonnerup, B. U. O., et al. (1987), Magnetopause properties from AMPTE/IRM observations of the convection electric field: Method development, J. Geophys. Res., 92, 12,137-12,159. Southwood, D. J., et al. (1988), What are flux transfer events?, Planet. Space Sci., 36, 503-508.

27. Grad-Shafranov reconstruction technique (Hau & Sonnerup, 1999) (A spatial initial value problem) Assumptions Plasma structures are: in magnetohydrostatic equilibria (time-independent). ×× P t, p, & B z are functions of A only (constant on same field lines). 2-D (no spatial gradient in the z direction) Grad-Shafranov (GS) equation (e.g., Sturrock, 1994) Magnetic field tension balances with force from the gradient of total (magnetic + plasma) pressure.

28. X A 2D structure X Y Z (invariant axis) Reconstruction procedure Y Reconstruction plane Lx = V ST_X * T (analyzed interval) X axis: sc trajectory in x-y plane V ST_X Spatial integration V ST (V HT ) (in the x-z plane)

29. Spatial initial value problem (Sonnerup & Guo, 1996) Grad-Shafranov equation spatial integration in  y direction (2nd order Taylor exp.) (1st order Taylor exp.) GS eq.