Understanding shock dynamics in the inner heliosphere with modeling and type II radio data: A statistical study. Issue 8 (1st August 2013)

• Record Type: Journal Article
• Authors: Xie, H.; St. Cyr, O. C.; Gopalswamy, N.; Odstrcil, D.; Cremades, H.
• Is Part Of: Journal of geophysical research. Volume 118:Issue 8(2013:Aug.)
• Page Start: 4711
• Page End: 4723
• Publication Date: 2013-08-01
• Subjects: coronal mass ejection -- interplanetary shock -- ENLIL model -- type II burst; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/jgra.50444
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract : [1] We study two methods of predicting interplanetary shock location and strength in the inner heliosphere: (1) the ENLIL simulation and (2) the kilometric type II (kmTII) prediction. To evaluate differences in the performance of the first method, we apply two sets of coronal mass ejections (CME) parameters from the cone‐model fitting and flux‐rope (FR) model fitting as input to the ENLIL model for 16 halo CMEs. The results show that the ENLIL model using the actual CME speeds from FR‐fit provided an improved shock arrival time (SAT) prediction. The mean prediction errors for the FR and cone‐model inputs are 4.90±5.92 h and 5.48±6.11 h, respectively. A deviation of 100 km s −1 from the actual CME speed has resulted in a SAT error of 3.46 h on average. The simulations show that the shock dynamics in the inner heliosphere agrees with the drag‐based model. The shock acceleration can be divided as two phases: a faster deceleration phase within 50 R s and a slower deceleration phase at distances beyond 50 R s . The linear‐fit deceleration in phase 1 is about 1 order of magnitude larger than that in phase 2. When applying the kmTII method to 14 DH‐km CMEs, we found that combining the kmTII method with the ENLIL outputs improved the kmTII prediction. Due to a better modeling of plasma density upstream of shocks and the kmTII location, we are able to provide a more accurate shock time‐distance and speed profiles. The mean kmTII prediction error using the ENLIL model density is 6.7±6.4 h; it is 8.4±10.4 h when the average solar wind plasma density is used. Applying the ENLIL density has reduced the mean kmTII prediction error by ∼2 h and the standard deviation by 4.0 h. Especially when we applied the combined approach to two interacting events, the kmTII prediction error was drastically reduced from 29.6 h to −4.9 h in one case and 10.6 h to 4.2 h in the other. Furthermore, the results derived from the kmTII method and the ENLIL simulation, together with white‐light data, provide a valuable validation of shock formation location and strength. Such information has important implications for solar energetic particle acceleration. Key Points: ENLIL using FR‐fit inputs improved performance than using cone‐fit inputs. Using the ENLIL model density improves the kilometric type II prediction. ENLIL reproduced the likely CME‐CME and CME‐streamer interactions.