1. The Second International Space Weather Symposium
Relationship Between Magnetic Clouds and Earth-Directed CMEs: Contribution of Stanford Solar Group to Space Weather
Xuepu Zhao
The Second International Space Weather Symposium
Nanjing, Oct , 2009

2. 1. Introduction
I’ll talk, specifically, about the relationship of central axial directions between MCs and flux ropes underlying Earth-Directed (E-D) CMEs.
Stanford solar group is a member of CISM (It is a NSF’s Science and Technology Center, ) and involved in Space Weather research. We provide :
(a) WSO, MDI, and the coming-up HMI synoptic maps & synchronic frames to MAS & WSA coronal models as coronal boundary condition for predicting the ambient solar wind;
[Hoeksema et al, 2008; Yang et al, 2008]
(b) CC & ZEC cone model parameters to ENLIL heliospheric model as an inner boundary condition to predict the arrive time of shocks and ICMEs [Zhao et al, 2002, 2005, 2008].

3. Fig. 1 Predicted and observed ICME associated with
1997:05:12 E-D halo CMEs. [Odstrcil, Riley, Zhao,
2004]. The CME propagation speed can be well
predicted.

4. Fig. 2 Predicted and observed ICMEs associated with
E-D halo CME [Owen and Zhao, 2007].

5. (c) We also provide high-cadence MDI and HMI (vect
(c) We also provide high-cadence MDI and HMI (vect.) magnetograms for study of active regions.
(d) We develop algorithm for predicting storm intensities. According to Siscoe & Schwenn’ review report [Space Sci. Rev., 123: , 2006] the algorithm for forecasting intensities caused by ICME bodies is based on our early work (Zhao & Hoeksema, 1997), i.e.,
D(h) = (11.49 – 0.12 Le) ± (1)
Bg(θ)(nT) = (10.76 – 0.10 Le) ± (2)
Le(deg) = ( Fo) ± (3)
Here D-Bs duration, B-Bs intensity, Le-MC latitude,
Fo-DSF latitude. Fig. 3 shows the relationship between
Bs events and MCs.
We review here our efforts to improve Eqs. (1), (2) and espacially
(3) by investigate the relationship of the orientation between MCs
and E-D CMEs.

6. Figure 3. Dependence of Bs events’ duration and intensity on the central axial direction of MCs

7. 2. Multiple regression
The Eqs (1) & (2) have not included the effect of CME velocity, they are valid only for slow CMEs [Schwenn, 2005]. As shown in Figs. 1 & 2, the radial CME velocity can be predicted using code of MAS+ENLIL+WSA+ZEC.
We have developed a multiple regression to include the effect of CME velocity, and the
effect of rope central axial field strength (when it is available), as shown in Fig. 4 [Zhao & Hoeksema, 2006].

8. Fig. 4 Multiple correlation coefficients (“c” in panels) and multiple regressions of MC Bs event, (Duration,D, in left column and intensity B in right column), with MC parameters, i.e., ecliptic latitude of central axis Le, impact distance p, CME speed U, and central axial field strength Bax. The open (filled) circles denote the observed (predicted) duration and intensity of MC Bs events
[Zhao & oeksema, 2006].

9. 3. Improving the prediction of the central axial field direction of MCs
Bs events, long interval (>10 hrs) of strong (<-10 nT)
southward IMF component, have one-by-one correspondence with storms [Tsurutani et al, 1988].
Most Bs events occur within MCs. The central axial direction, CAD, of MCs determines the strength and duration of Bs events in MCs [Zhao & Hoeksema, 1998]. Thus, prediction of the CAD of MCs, Le in Eq (3), is one of key issues in the space weather.
We’ll show how to use heliospheric current sheet, HCS, EIT Post eruption Arcade, EPA, and E-D halo CMEs to predict MC’s orientation.

10. 3.1 MC and HCS
Fig. 5. The Magnetic cloud is a segment of huge interplanetary
magnetic flux ropes.

11. Fig. 6 HCS or Sector boundary has been suggested [Crooker et al, 1993] and confirmed [Zhao & Hoeksema, 1996] to be the conduit for the CME ropes’ propagation.
(a) Flux ropes form from helmet arcades; (b) Fields in rope legs match the polarity of adjacent sectors; (c) φb of ambient IMF is consistent with φb in two ends of MC.

12. Fig. 7 Determination of the central axial direction of MCs on the
basis of the local inclination of HCSs and N-S asymmetry of
the helicity [Zhao and Hoeksema, 2007].

13. Fig. 8. Local inclination of HCS near the source region of E-D halo CMEs. Dark lines denote HCSs, blue and red the outward and inward field polarity. Symbols * and + denote CME source & solar
disk center at CME onset. The
field polarities around local
HCS can be used to determine
the central axial direction of
MCs. Among 35 E-D CMEs,
there are 7 partially northward,
consistent with that 7 E-D CMEs have no storm associated, indicating that the local
inclination of HCSs is a good
predictor of MCs’ orientation.
(Zhao 7 Webb, 2003).

14. Fig. 9 The further confirmation of the correlation of the orientations between MCs and the local inclination of HCS.
Adopted from Yurchyshyn , 2008.

15. 3.2. Orientation between MCs & EPAs
Fig. 10 Oct. 29 and 31, 2003 MCs
S1 & ICME1 ~ 28 Oct 2003 halo CME N  S, left-handed MC (Hu et al, 2005) with low proton density & not-low temperature.
S2 & ICME2 ~ 29 Oct 2003 halo CME. There is no southward HMF component.
(Adopted from Farrugia et al.,
2005.)

16. Fig. 11 The 29 & 31 Oct. 2003 MCs and WSO CR2009 HCS . The symbols * + + * *
Fig The 29 & 31 Oct MCs and WSO CR2009 HCS . The symbols *
around Carrington longitudes of 303 and 275 degs denote Oct 28 X17
flare & CME and Oct 29 X10 Flare & CME. They are underlying HCS.

17. BCRs are located underlying the HCS. [Zhao and Webb, 2003].
UCR
UCR
UCR
Fig. 12 The unipolar and bipolar coronal closed field regions, UCR & BCR.
BCRs are located underlying the HCS. [Zhao and Webb, 2003].

18. Fig.13 Calculated
magnetic arcades
anchored all pixes
with different top
ranges.
AR0486 is located
in a UCR;
The highest arcade
top is 1.10 Rs

19. left-handed EIT bright structure, predicting a MC with a leading
Fig. 14 The locus of arcade tops above the X17 flare is parallel to the
left-handed EIT bright structure, predicting a MC with a leading
northward HMF component, consistent with ACE obs.

20. handed arcade, predicting a MC with a northward HMF component,
EIT _22.00 (20.37)
Fig. 15 The locus of arcade tops above the X10 flare is parallel to the EIT left-
handed arcade, predicting a MC with a northward HMF component,
consistent with ACE observation.

21. 3.3 MCs and E-D Halo CMEs
The orientation of MCs may be rotated W.R. to that of DSFs or EPA by the physical processes taking place near the solar surface, such as magnetic reconnection and various Instabilities
Fig. 16 Magnetic reconnection near the solar surface before eruptions. Adopted from N. Crooker, 2007.

22. Fig. 17 Kink instability.
Adopted from
Y. Fan, 2007.

23. Yurchyshyn et al
[2007; 2008; 2009]
Investigate the
Relationship of MCs
With the orientation
Of halo CMEs.
Fig. 18 shows the
definition of the
orientation angle.

24. Fig. 19 Adopted
From Yurchyshyn
Et al., 2009

25. Fig. 20

26. 4. Summary
4.1 We have shown that AR486 occurred in an unipolar closed field region. The top of calculated magnetic arcades in UCR is significantly lower than in BCR.
4.2 Combining with the observed handedness of the EIT post-flare bright arcade, the magnetic arcade calculated using the PFSS model and the MDI synoptic frame can be used to predict the central axis direction of the 29 and 31 Oct 2003 MCs. This method may be used for BCR- as well as UCR-CME associated MCs.
4.3 High quality arcade images from AIA/SDO & KuaFu are expected to be able to more accurately determine the handedness of magnetic arcades.

27. Thank you!

28. Many Earth-directed CMEs are flux-rope-like with two ends anchored on the solar surface. To determine whether or not the CMEs are geoeffective, we need to know the radial propagation direction and speed of the CMEs, and the size and direction of the central axial field of the ropes, so that we can predict when and which part of the rope-like structures will hit the Earth, and whether or not this part of rope-like structures contains
southward IMF component. We have developed the elliptic cone model (ZEC)
for inverting the 3-D geometric and kinematic properties mentioned above
from observed halo parameters of 2-D frontside full halo CMEs (Zhao, J.
Geophys. Res., 113, A02101). We firstly determine the halo parameters for 10 frontside full halo CMEs that have magnetic clouds associated (See J. Zhang et al., J. Geophys. Res., 112, A10102); secondly invert the propagation direction and speed, the angular width and orientation of rope-like structures for the 3 CMEs using the ZEC; and thirdly
compare the inverted orientation of the rope-like CMEs with that of
corresponding magnetic clouds and post-eruption arcades.
Finally we discuss the potential contribution of the elliptic cone
model to the space weather forecasting by combining the inversion solution with 3-D MHD models of the heliosphere.

29. Symptoms of Space Weather and Solar Causes
The symptoms of space weather: Magnetic disturbances and energetic particle disturbances.
Magnetic disturbances: CMEs, Flares, High Speed Streams
Energetic particle disturbances: CMEs, Flares

30. Forecasting Magnetic Disturbances
Arrive time of shocks and ICMEs
Empirical models: Schwenn et al., 2005
Gopalswamy et al., 2001
Physics-based models: STOA, ISPM, HAFv2,……
CORHEL+WSA+cone
2. Intensities
ICME Sheaths: Cliver et al., 1990; Owens et al., 2005.
ICME Bodies: Zhao & Hoeksema , 1997

32. Figure 2.2 Prediction algorithm

36. Fig. 4 The –Bz event, i.e., the long intervals (> 10 hrs) of strong ( < - 10 nT) southward IMF component, has one-to-one correspondence with intense geomagnetic storms. Most, if not all, of –Bz events occur within MCs. But not all MCs have –Bz events.
(Zhao & Hoeksema, 1997)

37. Fig. 5

38. Fig. 5 MC is a segment
Of the huge magnetic
Flux rope. Accepted
From P. Demoulin,
2009

39. The existence of the correlation between the CAD of
MCs and the CAD of SDFs (Marubashi, 1986; Bothmer &
Schwenn, 1994) suggests that the CAD of coronal
flux ropes remains basically constant while expanding
into the heliosphere.
The CAD of coronal flux ropes is expected to be
aligned with the locus of the outmost arcade tops
2.1 Magnetic clouds are a segment of coronal flux ropes expanding into the
heliosphere as a loop of nested coils connected to the Sun at both ends.
The coronal flux ropes are believed to be formed above the polarity inverse
line in 3D arcades due to flux cancellation, emergency, or shearing and
converging photospheric motions.