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Two-spacecraft reconstruction of a magnetic cloud and comparison to its solar source 1Institute of Physics, University of Graz, Universitätsplatz 5, A-8010 Graz, Austria 2Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz, Austria 3Space Science Center and Dept. of Physics, University of New Hampshire, Durham, NH 03824, USA 4Hvar Observatory, Faculty of Geodesy, Kačićeva 26, HR-10000 Zagreb, Croatia e-mail: moestlch@stud.uni-graz.at C. Möstl1,2, C. Miklenic1, C. J. Farrugia3, M. Temmer2,4, A. Veronig1, A. Galvin3 and H.K. Biernat1,2 COMPARISON. Original MC flux Φp = 6.5 x 1021 Mx vs. ribbon flux Φr = 3.6 x 1021 Mx. Reconnection is certainly highly relevant for an in-situ formation of the twisted-flux rope, but uncertainties still large (parts pre-existing?). Consistent with Leamon et al. (2004, 12 events, suggest that MCs are formed by reconnection from the AR with the overlying coronal field). Qiu et al. (2007, 9 events) also Φp ~ Φr hinting at a in-situ formation of flux ropes. Orientation change (90° for post-flare arcades, 30° for filament apex) maybe through interaction with the highly curved heliospheric current sheet (MC is at sector boundary at 1 AU). INTRODUCTION. The interplanetary coronal mass ejection (ICME) containing a magnetic cloud (MC) on November 20, 2003 elicited the strongest geomagnetic storm of solar cycle 23 (1995-2006) with a minimum Dst= - 472 nT, about two weeks after the massive eruptions known as ''Halloween'' events resulted in comparable geo-effects. We apply an advanced methodology to study the event from a M4 flare on Nov 18, 2003 and the corresponding halo CME to the ICME and magnetic cloud observed at Earth and search for quantitative links. We pay special attention to the orientations and the fluxes involved. These kind of studies are expected to enhance knowledge useable for space weather forecasting. Had the severe geo-effects been predictable from the current state of research? Upcoming STEREO-WIND/ACE coordinated observations will help in clarifying some of the issues raised here. Acknowledgements. C. M. is supported by a research scholarship of the University of Graz and by the young researchers fund of the Steiermärkische Sparkasse. C.J.F. is a co-Investigator on STEREO/PLASTIC. This work is supported by NASA WIND/SWE and MFI grant NNG06GC75G, and NNG06GD41G. It is also supported by the Austrian Fonds zur Förderung der wissenschaftlichen Forschung under projects P20145-N16, P17100-N08, and J2512-N02 (Erwin Schrödinger Fellowship of M.T.). REFERENCES. Bothmer, V. and Schwenn, R.: Ann. Geophys. 16, 1, 1998. Dasso, S., Mandrini, C. H., Démoulin, P., and Luoni, M. L., A&A, 455, 349–359, 2006. Gopalswamy, N., S. Yashiro, G. Michalek, H. Xie, R. P. Lepping, R. A. Howard, Geophys. Res. Lett., 32, L12509, 2005. Hasegawa, H., B. U. Ö. Sonnerup, et al., Ann. Geophys., 23, 973, 2005. Handy et al., Sol. Phys., 187, 229–260, 1999. Hu, Q., B. U. Ö. Sonnerup, J. Geophys. Res., 107, 10 -1, 2002. Leamon, R. J., Canfield, R. C., Jones, et al., J. Geophys. Res., 109, 5106, 2004. Leamon, R. J., Canfield, R. C., and Pevtsov, A. A.: J. Geophys. Res. 107(A9), 10.1029/2001JA000313; 2002. Lepping, R. P., et al., Space Sci. Rev., 71, 207, 1995. Miklenic, C., A. M. Veronig, B. Vrsnak, and A. Hanslmeier, A&A 461, 697-706, 2007. McComas, D. J., et al., Space Sci Rev., 86, 563, 1998. Ogilvie, K. W., et al., Space Sci. Rev., 71, 55, 1995. Qiu, J., Q. Hu, T. A. Howard, V. B. Yurchyshyn, ApJ 659, 758, 2007. Smith, C. W., et al., Space Science Rev., 86, 613, 1998. Yurchyshyn, V., Hu, Q., and Abramenko, V., Space Weather, 3, 8, 2005. ACE data: Magnetic field (Smith et al., 1998) and proton plasma (McComas et al., 1998) data.  WIND data: magnetic field and plasma (proton) from the MFI (Lepping et al., 1995) and SWE (Ogilvie et al., 1995) instruments.  SOLAR SOURCE REGION. The Nov 20 ICME is connected with the Nov 18 08:50 UT halo CME, which originated from AR 10501 (Gopalswamy et al., 2005) . The CME linear speed was 1660 km/s and decelerated down to ~740 km/s (sheath) at 1 AU. It is associated with the Nov 18 GOES M3.9/2N flare event, which occurred in the vicinity of AR 10501 at S02E37. A dark U-shaped filament is erupting to the south west. The prominent halo CME front is also south-west bound. Temporal evolution of the flare in the impulsive phase in the TRACE 1600 Å UV channel (Handy et al., 1999). FOV 320'‘x 250''. Two bright separating flare ribbons are observable.  Composite magnetic field map. Black contours are transverse field lines, Bz is color coded. Upper trajectory ACE, lower WIND.  Correlation between observations and predictions from the composite map. FILAMENT AND ARCADE ORIENTATION. The filament and the associated post-flare loops span a tilt angle from ~35° (bright southern loops) until ~335° (weaker post-flare arcade associated with the apex). The leading magnetic field orientation is obtained from the underlying magnetic field (SOHO/MDI). From the shearing direction of the post-flare loops and the axial magnetic field of the erupting filament the filament should be right-handed. Consistent with Yurchyshyn et al. (2005) who calculated the direction of the axial magnetic field from a LFFF model. It also fits in the pattern that MCs originating from active regions of the southern hemisphere are right-handed in 3 out of 4 cases (Leamon et al., 2002; cf. Bothmer and Schwenn, 1998). However, for this event the shearing direction includes an ambiguity and should be kept in mind when determining the orientation of flux rope axes. FLARE RECONNECTION FLUX. The reconnected magnetic flux at a particular time is determined separately for each magnetic polarity domain. Bn is the magnetic field strength component perpendicular to the solar surface in the newly brightened area da that is swept by the flare ribbons (red positive, blue negative fields ). A TRACE 1600 Å image sequence (64 images, pixel size 0.5”, cadence 23 s) was used to determine da in an image compared to the preceding images. The TRACE obs-ervations covered a good portion of the impulsive phase (RHESSI non-thermal hard X-ray (HXR) emission). The longitudinal photospheric magnetic field was taken from SOHO/MDI before flare onset (06:23:02 UT, 1 pixel=2.0''). The total reconnected flux Φr is the sum of all fluxes in all pixels that brightened during  any period of the flare (details in Miklenic et al., 2007). Φ+ = 1.7 x 1021 Mx and Φ- = -1.9 x 1021 Mx (~ equal shares). Thus Φr = 3.6 x 1021 Mx. Lower limit as the very end of the flare impulsive phase, as indicated by the RHESSI HXR flux, was not covered by TRACE observations.   Combined Pt(A) fitting function (red ACE, blue WIND).  ACE SWEPAM electron pitch angle distributions for Nov 20 2003, 12-24 UT.  Wilcox HCS map (classic 2.5 solar radii) TWO-SPACECRAFT RECONSTRUCTION OF THE MAGNETIC CLOUD ON NOV 20, 2003. . Proceeds in the steps (see Hu and Sonnerup, 2002 and Hasegawa et al., 2005): deHoffman-Teller analysis of combined set of magnetic field and velocity measurements (VHT=623 km/s cc=0.996, Walén slope= 0.0045). Combined fit for Pt(A) and Bz(A) by a 3rd order polynomial with exponential tails. Numerical integration of the Grad-Shafranov equation with known right-handside through Pt(A) fit and spacecraft observations as initial values: results in magnetic field maps for ACE and WIND. Merging into one composite map (Gaussian window). Correlation coefficient cc=0.9902 between observed and predicted magnetic field components is maximized at θ= -50° and Φ=85° (GSE latitude and longitude). The ICME consists of a shock (1st solid line), the sheath, a flux rope MC (2nd + 3rd solid lines) and the back region (dashed lines). The back region consists of reconnected MC field lines with the solar wind IMF (Dasso et al., 2006). It shows smooth field lines but no rotation and higher beta as the MC, <V> = 540 km/s. Estimated time since reconnection started is 30h (cf. 50h from Sun to 1 AU) and 50 % of the original flux at the Sun has been reconnected. FLUXES. toroidal (axial) flux: Poloidal flux: Am corresponds to center (white dot), Ab outer boundary (white contour line in map and solid line in Pt(A)). L is length in z dimension. Here L= 1.5 - 2.5 AU, because inter-mittent BDEs are visible in the 2nd MC half. Original poloidal flux at the Sun is MC flux at Earth + reconnected flux ~ 6.5 x 1021 Mx.  Hα filtergrams (Kanzelhöhe Solar Observatory, Austria) showing the global flare evolution and the erupting filament. Right: Temporal evolution of the associated CME in SOHO/LASCO C2 and C3. Hα: Evolution of the filament from Nov. 15 – Nov. 18  MDI magnetogram overlaid with filament contours. White and yellow arrows indicate the leading and the axial field direction. BBSO Hα after the eruption.  TRACE 171 Å post-flaring arcade at 9:18 UT overlaid with filament contour lines. White asterisks are the location of the northern filament (not erupted).