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Multi-point in situ observations and geoeffects of the August 1-4 2010 events

Multi-point in situ observations and geoeffects of the August 1-4 2010 events. C. Möstl, C. J. Farrugia, R. Harrison, E.K.J. Kilpua, L. Jian, J. Davies, D. Odstrcil, N. Nitta, D. Webb, C. A. deKoning, M. Temmer, T. Rollett, A. Veronig, Y. Liu, T.L. Zhang, J.G. Luhmann, A. B. Galvin.

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Multi-point in situ observations and geoeffects of the August 1-4 2010 events

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  1. Multi-point in situ observations and geoeffects of the August 1-4 2010 events C. Möstl, C. J. Farrugia, R. Harrison, E.K.J. Kilpua, L. Jian, J. Davies, D. Odstrcil, N. Nitta, D. Webb, C. A. deKoning, M. Temmer, T. Rollett, A. Veronig, Y. Liu, T.L. Zhang, J.G. Luhmann, A. B. Galvin

  2. Overview of total magnetic field strength Messenger Bmax scaled to 1.06 AU (STB):STB: 33.2 nT Vshock=600 km/sVEX: 31.2 nTWind: 17.9 nT Vshock=510 km/sSTA: 8.6 nT IWF/ÖAW GRAZ

  3. Wind (Earth) What do we see? Shock S2, long sheath Two magnetic flux ropes, showing signs of interaction:heating and compression of the first one (M1) Low T region before S2 – another ICME? Three jumps in density D1-3 around or inside the magnetic flux ropesD2 could be filament material There are two minima in Dst, two Kp maxima – the 1st one due to the sheath, the 2nd due to magnetic cloud M2 S2 D3

  4. Filament material near Earth? • High alpha/proton densityat beginning of the magnetic cloud M2 couldindicate seldomly observedfilament material(e.g. Burlaga et al. 1998) • Field and flow fluctuations ahead of the first ICME can be shown to be approximately Alfvénic • This caused the strongest disturbance measured by the Dst when corrected for magnetopause currents (min. Dst ~ -100 nT). IWF/ÖAW GRAZ

  5. STEREO-B and VEX (east of Earth) STEREO–B and VEX show a richnessof features, at least two moderately strong shocks and three flux ropes Despite 18° separation there is notmuch difference between the magnetic field profiles

  6. „Pancaking“ of the M2 structure at STB and VEX Riley et al. 2004 ~1:6 M2 is the same structure at STB and VEX (similar field rotation) Assumptions • inclined flux rope • No deflection between 0.72 – 1 AU 18° corresponds to 0.314 AU along the 1 AU circle • 90° inclination to ecliptic:STB cross section should be 0.314 / 0.039 AU = 8:1 • 45° inclination: 0.222 /0.039 AU = 5.7:1 Sun 0.039 AU 18° STB VEX this indicates a strongly elongated cross-section (pancake) IWF/ÖAW GRAZ

  7. M3 M2 S2 M3 M2 S2 ? M1(earlier eruption) M1 S2 The big picture ? Low T region, ICME?(earlier eruption, no shock)

  8. Summary of results so far • At STEREO-B and VEX, temporal profiles of field and plasma parameters are ~ similar. Both saw 3 flux-rope type ICMEs and 2 moderately strong shocks. (but 1 shock-ICME pair was from a previous eruption) • Wind observed only 2 ICMEs, likely interacting, and 1 shock. At the beginning of the 2nd flux rope we very likely identified filament material from one of the Aug 1 eruptions. Geomagnetic response had two minima (sheath and magnetic cloud 2) • A paper for JGR (the “impact” paper) is in preparation, two major things left: (1) use results from shock and flux rope modeling to construct a geometrically “correct” global picture (so far only sketches)(2) Messenger data are available in September, but should be rather important to set constraints on what is happening west of the Earth (STEREO-A does not see anything) Conclusion • ICMEs and shock timing, location and parameters set strong constraints on the propagation directions and speeds of multiple CMEs leaving the Sun on 1 Aug 2010. • Together with the SDO observations, these may serve as boundary conditions for benchmark tests of numerical models for a sequence of CMEs erupting in close temporal proximity. IWF/ÖAW GRAZ

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