Relationship Between Magnetic Clouds and Earth-Directed CMEs:Space Weather Research in Stanford Solar Group Xuepu Zhao The Second International Space Weather Symposium Nanjing, Oct. 17-21, 2009
1. Introduction • Stanford solar group is a member of LWS & CISM, and involved in Space Weather research in four aspects: (a) Provide WSO, MDI, and the coming-up HMI synoptic maps & synchronic frames to coronal models as coronal boundary condition for predicting the corona & ambient solar wind [Hoeksema et al, 2008; Yang et al, 2008; Zhao et al, 1997; 2009] (b) Provide high-cadence MDI and HMI (vect) magnetogrm. for study of active regions & activity index [Yang et al. 2007] (c) Provide ZEC cone model parameters to heliospheric models to launch plasma clouds and to predict the arrive time of shocks and ICMEs [Zhao et al, 2002; 2005; 2008; Hayashi et al, 2006].
(d) Develop & improve algorithm for predicting storm intensities. According to Siscoe & Schwenn’ review report [Space Sci. Rev., 123: 453, 2006] the only existing 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) ± 4.70 (1) Bg(θ)(nT) = (10.76 – 0.10 Le) ± 5.12 (2) Le(deg) = (-1.4 + 0.7 Fo) ± 17.8 (3) Here D-Bs duration, B-Bs intensity, Le-MC latitude, Fo-DSF latitude. Fig. 1 shows how Bs events [ i.e., the long (> 10 hrs) interval of strong (< -10 nT) southward IMF component] depend on the MC’s central axial field direction. We review here our efforts to improve Eqs. (1), (2) and especially (3) by investigate the relationship of the orientation between MCs and E-D CMEs.
Figure 1. There is no Bs events when MCs point to northward. The duration and intensity of Bs events strongly depend on the MCs’ central axial direction.
2. Improving the prediction of Bs events: 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. 2, the radial CME velocity can be well predicted using the code of MAS+ENLIL+WSA+ZEC. We have developed a multiple regression [Zhao & Hoeksema, 2006], as shown in Fig. 3, to include the effect of CME velocity, and the effect of rope central axial field strength (when it is available).
Fig. 2. Predictedand observed ICME associated with the 1997:05:12 (left column, Odstrcil, Riley, Zhao, 2004 ) and 2006:12:13 (right column, Owen , Zhao, 2008) E-D halo CME. The CME propagation speed & arrival time can be well predicted.
Fig. 3 Multiple regressions for the duration, T, and intensity, I, of Bs events are shown at the top of each panel. Symbols La, U, and Ba in the expressions denote, respectively, the ecliptic latitude of central axis, speed, and central axial field strength of MCs. The symbols + and * denote the observed and predicted duration and intensity of Bs events [Zhao & Hoeksema, 2006]. Correlation coefficients for intensity (“coe” in panels) increase from 0.69 to 0.82, 0.87.
3. Improving the prediction of the central axial field direction of MCs • Bs events have one-to-one correspondence with storms [Tsurutani et al, 1988]. The central axial field direction, CAD, of MCs determines the strength and duration of most of Bs events [Zhao & Hoeksema, 1998]. Thus, prediction of the CAD of MCs is one of key issues in the space weather. However, there is no space observations of Ha filaments! • 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.
3.1 MCs and local HCS 3a 3b 3c Fig. 3. (a) TheMagnetic cloud is a segment of huge interplanetary magnetic flux ropes. (b) HCS is the conduit for the CME propagation [Crooker et al, 1993; Zhao & Hoeksema, 1996]. (c) The north-south hemispheric rule of the handedness of the magnetic helicity.
Fig. 4a. Local inclination of HCS near the source region of E-D halo CMEs. Symbols *and + denote CME source & solar disk center at CME onset. Dark lines denote HCSs, blue and red the outward and inward field polarity. Near minimum phase, MCs orientated horizontally because HCS is nearly parallel to the solar equator.
Fig. 4b Determination of the central axial direction of MCs on the basis of the local inclination of HCSs and N-S asymmetry of the handedness of helicity [Zhao and Hoeksema, 2007].
Fig. 4c 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’ orienta. (Zhao 7 Webb, 2003)
Fig. 5 The further confirmation of the correlation of the orientations between MCs and the local inclination of HCS. Adopted from Yurchyshyn , 2008.
3.2. MCs & EPAs Fig. 6 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.) The two MCs are not originated in closed regions underlying HCS.
+ + * * Fig. 7 The 29 & 31 Oct. 2003 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 not underlying HCS.
BCR UCR UCR UCR Fig. 8 The unipolar and bipolar coronal closed field regions, UCR & BCR. Only BCRs are located underneath the HCS. [Zhao and Webb, 2003].
Fig.9 Calculated magnetic arcades anchored all pixes with different top ranges. AR0486 is located in a UCR; The Highest arcade top is 1.10 Rs 0486
EIT 195 2003.10.28_13.13 (11.00) Fig. 10. 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.
EIT 195 2003.10.29_22.00 (20.37) Fig. 11 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.
Fig. 12 Kink instability. Adopted from Y. Fan, 2007. Question of hemispheric role of handedness & possible answer.
4. Summary 4.1 We have tried to improve the prediction of arrival time of shocks and ICMEs using ENLIL+WSA+EZC. The next step is to find a way to rather objectively determine the outline of observed full halo CMEs. 4.2 We have tried to improve the algorithm for predicting the duration & intensity of Bs events by using the multiple regression together with the predicted CME speed and the new observations of magnetic vector field by HMI/SDO. 4.3 We have tried to improve the prediction of MC’s orientation by using the local inclination of HCS and the N-S asymmetry of the handedness of helicity for CMEs originated in Bipolar closed regions underneath the HCS.
4.4 We develop a way to predict the MC’s orientation using observed orientation and handedness of EPA’s for CMEs originated in unipolar closed regions. The AIA/SDO observations of EPAs are expected to be much better than EIT/SOHO so that improving the prediction. 4.5 The orientation of flux ropes predicted on the basis of the ZEC model and full halos observed by AIA/SDO is expected to be more accurate than that obtained from Yurchyshyn et al’ technique. 4.6 It is expected that the coming-up high-cadence, high-resolution HMI/SDO and AIA/SDO observations will make significant contribution to the space weather research and forecasting. --END--