Modeling of CME-driven Shock propagation with ENLIL simulations using flux-rope and cone-model inputs

Using observations from STEREO/SECCHI and SOHO/LASCO, combined with WSA-Cone-ENLIL model simulations, we study the propagation and evolution of 17 CME-driven shock from Sun to Earth. We use flux-rope (FR) and cone-model fitting outputs of Vcme and width as spherical cloud speed and angular width inputs for the ENLIL model. We compared the simulated the shock arrival times Tenlil from two sets of inputs with the observed shock time by Wind Tobs. The results show that the predictions from ENLIL using FR-fit inputs are generally better those using cone-model fit inputs. However, both model inputs give decent prediction results. Overall, the FR-model fit to multi-view observations provides more accurate values of CME actual speeds and widths. There is no significant differences between the mean fit CME speed and width from two models.The difference of the mean speed and the mean width from two models are 45 km/s and 5°, respectively, and the mean prediction errors for the FR and cone-model are 5.4 hours and 6.1 hours. It is found that for the slow CME with speeds < 900 km/s , the mean prediction errors are improved to 4.1 hours (FR-fit) and 5.0 hours (Cone-fit) with dcld = 2 ( density enhancement factor of cloud to fast solar wind) compared to default dcld of 4. In addition, we study the predictions from the kmTII method, which is based on the kilometric Type II radio emissions measured by Wind/WAVES (Cremades, et al., 2007). It is found that the kmTII predictions can be improved by using the ENLIL model plasma density upstream the modeled CME/shock (compared to using the average density at 1 AU of n0 = 7.2 cm-3).

H. Xie1,2, C. St Cyr2, N. Gopalswamy2, and D. Odstrcil2,3

1Catholic University of America, Washington, D.C.; 2NASA-GSFC; and ;3George Mason University

Difference of prediction error: err = |Err_FR – Err_cone| as function of input speed difference Vfit = |Vfr - Vcone|: err = ~ 2.27+ 0.01* Vfit. In average, an input CME speed difference of 100 km/s results in a prediction error difference of 3.46 hours. Note that, however, relatively large scattering exists for individual events.

The selected event list includes earthward halo CMEs from 2010 to March 2012 with Vcme > 500 km/s. The table lists the shock date and time, CME date and time, source location, FR-fit and cone-fit speed and half width, ENLIL prediction error with two model fits: Err_f and Err_c, dcld, and the kmTII prediction errors for six kmTII CMEs, Err_km1 and Err_km2, using the ENLIL model density, n0_enlil, and the average solar wind plasma density, n0_avg, at 1 AU respectively. The mean Err_km1 = 4.88 hrs and mean Err_km2 = 6.0 hrs.

Top panels show that the mean cone-fit CME speed Vcone is slightly larger than the mean FR-fit speed Vfr but max( Vcone – Vfr ) can reach 601 km/s. Bottom panels show that the mean half width cone is slightly larger than fr and max(cone – fr ) = 13.

Prediction error DT= Tenlil-Tobs. Overall, the errors using cone-model fit inputs (Err_cone) are larger than those using FR-fit inputs (Err_FR).Comparison of Cone-model and FR-model

fitting: Vsky vs. Vfit. Red and blue diamonds denote Vfr and Vcone, over-plotted with solid line Vfit=Vsky.

Where Vsky and Vfit are the sky-plane speed and model fit Speed of the CMEs.

Type II dynamic spectrum detected by the Wind/Waves on January 23 2012. Red cross symbols in the figure mark the heights from COR2 observations and the ENLIL simulation results, with a simple density model n = n0/r2 (n0 is the plasma density at 1 AU in units of cm−3) we have r(t) = (9/18)sqrt(n0)/f(t), r(t) in units of AU.White X symbols are selected measurement points in the spectrum, with which we derive the shock speed to predict the shock arrival time: Vsh = (9/18) sqrt (n0) × slope(1/f) × 1.5e8 (km/ s).

Shkdate Time CMEdate Time Loc_sc FR-fit Cone-fit Err_f Err-c dcld Err_km1 Err_km2

          V w/2 V w/2       (n0_enlil) (n0_avg)

  (UT)   (UT)   (km/s) (deg) (km/s) (deg) (hr) (hr) 2 (hr) (hr)

02/11/10 00:00 02/07/10 02:45 N21E11 525 39 580 52 -10.9 -14.47 2 n/a n/a04/05/10 07:58 04/03/10 10:34 S25W03 1011 37 914 41 0.73 6.87 2 n/a n/a02/15/10 17:28 02/12/10 11:50 N21E07 752 38 791 40 0.65 1.74 2 n/a n/a04/11/10 12:18 04/08/10 03:15 N24E16 629 30 656 37 -4.51 -6.94 2 n/a n/a05/28/10 02:00 05/24/10 13:05 S15W18 650 38 611 48 -8.16 -5 2 n/a n/a02/18/11 00:40 02/15/11 02:36 S21W18 651 41 624 49 -3.78 -2.26 2 n/a n/a06/23/11 02:18 06/21/11 02:05 N16W00 1031 36 1211 39 6.92 2.42 4 n/a n/a07/11/11 08:05 07/09/11 00:15 S17E20 751 39 922 39 -1.47 -5.38 4 n/a n/a08/04/11 21:10 08/02/11 06:05 N14W01 1001 40 1099 42 -5.52 -10.1 4 n/a n/a08/05/11 17:23 08/04/11 04:05 N19W36 1722 50 1556 47 1.33 -0.56 4 -8.22 -3.92

09/09/11 11:49 09/06/11 22:22 N14W18 1033 45 832 39 -5.99 0.42 4 2.84 7.9911/12/11 05:10 11/09/11 13:21 N26E43 1288 38 1239 44 -3.02 -6.81 4 n/a n/a01/22/12 05:33 01/19/12 13:44 N33E27 1327 40 1494 48 -4.1 -6.55 4 3.77 9.9901/24/12 14:35 01/23/12 03:38 N33W21 2002 50 2456 53 3.91 -2.52 4 -5.71 -0.4203/08/12 10:30 03/07/12 00:02 N17E27 2349 40 2950 49 3.78 -5.08 4 1.87 12.7903/11/12 12:29 03/09/12 03:22 N17W03 1281 43 1168 53 -4.46 -3.21 4 n/a n/a03/12/12 08:30 03/10/12 17:15 N17W24 1705 44 1378 49 0.6 5.17 4 -6.91 -0.94