Presentation on theme: "Cluster, THEMIS, & Geotail Conjunction Event on 11 July 2008 Hiroshi Hasegawa ISAS/JAXA."— Presentation transcript:
Cluster, THEMIS, & Geotail Conjunction Event on 11 July 2008 Hiroshi Hasegawa ISAS/JAXA
Overview (2008-07-11) TH-B monitoring the solar wind & IMF. Three intervals of interest: 1. 0100-1100 UT: Cluster on the dawn flank, Geotail on the dusk flank, under changing IMF direction (both south of equator). 2. 1600-2000 UT: TH-A, D, & E at the post- noon magnetopause, Geotail on the dusk flank, under northward IMF. 3. 2000-2200 UT: TH-C, D, & E downstream of or near the parallel shock, TH-A near the magnetopause, under Bx-dominant IMF.
Cluster & Geotail (02-05 UT) Magnetic dips in both dawn & dusk BLs
What could be pursued? Magnetic topology of the boundary layer? - What features do ion & electron velocity distributions have? Response of the boundary layer to temporal changes in the IMF orientation? - Some ground/aurora signatures? Latitudinal dependence of KH wave activity? - May be meaningful to report the absence of clear KH activity at those (somewhat high) latitudes.
IMF |B|: 4-14 nT By <~ 0 Bz Bx Density Total Velocity 123 ACE 0-24 UT
Quasi-periodic tailward-propagating Alfvén waves, possibly mode-converted from KH waves By Bz Vy Vz
Summary of NBZ interval Simultaneous operation of lobe reconnection and the KH instability? Southward flow from lobe reconnection in the summer hemisphere confirmed. - Dayside BL formed via lobe reconnection. KH-associated(?) oscillations at X~-25 Re. Reconnection jets when the IMF orientation is changing. In sheath or at magnetopause? Role(s) of KHI in further SW entry and/or in tailward/inward transport of the dayside CD plasma?
Weaker B fluctuations than near local noon. 20-22 UT TH-C at (x,y)~(6, 10)Re BS
MP 20-22 UT TH-A at (x,y)~(4, 9)Re Several MP crossings probably due to enhanced dynamic P in sheath. No or thin BL in later interval.
What could be pursued? Spatial dependence of magnetosheath magnetic fluctuations/turbulence? Correspondence between magnetosheath fluctuations and MP crossings? - Some sheath structures may have excess dynamic pressure. Disappearance/erosion of dayside CD BL when IMF Bz changed from northward to ~0.
1 st interval: 01-11 UT on 11 July 2008 Simultaneous observations of dawn (Cluster) & dusk (Geotail) tail-flank boundary layers under varying IMF orientation Yulia: analyze PEACE electron pitch-angle distributions, to clarify magnetic topology of the boundary layer. Qing-He: investigate SuperDARN data, to see response/change of ionospheric convection to IMF orientation change. Hiroshi: check CIS velocity distributions, to find additional signatures to reveal the topology.
2 nd interval: 16-21 UT on 11 July 2008 Simultaneous operation of lobe reconnection & KH instability under northward IMF? Qing-He?, Harald?: ionospheric/aurora signatures of lobe reconnection in the northern hemisphere? Jean: run simulation to compare with Themis (southward flow from northern lobe reconnection) & Geotail (stagnant, dense dusk-flank boundary layer) observations Yulia: analyze PEACE data from the dawn tail-flank Hiroshi: reconstruct Themis KH-like BL structures Who?: analyze particle (ion/ele) signatures of lobe reconnection
2 nd interval: 16-21 UT on 11 July 2008 Reconnection in the magnetosheath(?) under IMF orientation change Jue?: in-depth analysis of reconnection jets (Walen test, particle signatures, component/anti-parallel?) Hiroshi: reconstruct reconnection jets?
3 rd interval: 20-22 UT on 11 July 2008 Spatial structures of magnetosheath fluctuations/ turbulence under Bx-dominated IMF conditions Who could lead? Response of the magnetopause/boundary layer to magnetosheath fluctuations under Bx-dominated IMF conditions (Who could lead?) Correspondence between magnetosheath fluctuations and MP crossings? - Some sheath structures may have excess dynamic pressure. Disappearance/erosion of dayside CD BL when IMF Bz changed from northward to ~0.