Effect of CME Interactions on SEP Intensity Modeling

Effect of CME Interactions on SEP Intensity: Modeling the 2012 -March-07 SEP Event with ENLIL NASA/GSFC H. Xie, N. Gopalswamy, and C. St. Cyr

2012 March 07 SEP event: with the 2 nd Largest Intensity during Cycle 24 and Two CMEs in Quick Succession SEP onset SEP peak SHOCK ESP 1500/6000 (SEP/EPS peak) 00: 02/pk: 00: 24/X 5. 4 01: 05/pk: 01: 14/X 1. 1 AR 11429/N 17 E 27

Two eruptions are seen distinctly in SDO AIA/193 A movie: CME 1 : N 17 E 27 AR 11429 CME 2: N 10 E 17 inter-loop btw two ARs with a time separation of ~ 1 hour.

Flux-rope fitting CME 1 : N 27 E 27 V = 2376 km/s W_(broad, edge) = (40 , 36 ) Loc: N 17 E 27 CME 2: V= 2203 km/s W_(broad, edge) = (50 , 28 ) Loc: N 00 E 17 CME 1 CME 2 Two CMEs had similar speeds and were separated by <10 Rs.

Two-CME Interaction Seen in COR 2 Images and DH Type II Dynamic Spectrum CME 1 CME 2 TII_CME 1

Ne vs. CME heights Diamonds: Density derived from TII frequency (ne = (f/9. )^2) Solid lines: curves fitted from data points Dash lines: Saito density model (1977) with: Nbase = 8. 4 x 108 & 4. 2 x 108 cm-3

WSA_Cone_ENLIL Model Hybrid Model combining the 3 D MHD simulation with observationbased inputs. Simulation domain: 21. 5 Rs ~ 2 AU 1)Set up background solar wind based on WSA or MAS models. 2) Insert a plasma cloud at 21. 5 Rs based on CME fit parameters: time, location, size and speed.

WSA_Cone_ENLIL Simulation: 2012 -03 -07 CME 2 CME 1 Run 1: Two CMEs CME 1: 2349, 40 , (17, -27) at 01: 55 UT CME 2: 2203, 50 , (0, 17) at 02: 40 UT Run 2: Only CME 1 same parameters as run 1

2 D Density Contour (Top ) Run 1: Lateral Shock formation along well-connected field line: ~03/07 15: 00 UT CME 2 CME 1 Hong_Xie_101812_SH_1 (Bottom) Run 2: No lateral Shock along well-connected field line was formed CME 1 Hong_Xie_041212_SH_2

Enhanced shock intensity caused by CME interaction Run 2 Run 1 Run 2 1 -D density cut along the Sun-Ear line: Normalized density (nr 2) vs. distance (r)

Larger shock speed were obtained when CME interaction was included Run 1: Vsk_fit = 1317 km/s Run 2: Vsk_fit = 988 km/s Time-distance profile from the simulation along the Sun-Ear line (height vs. time).

Discussion Role of two-CME interaction: 1. Perpendicular shock 2. Higher shock speed 3. Enhanced shock intensity Role of the preceding CME: seed particles enhanced turbulence level (Li et al. , 2012) Interchange reconnection between open and close magnetic fields can release particles to the turbulence-enhanced downstream of the 1 st CME shock, which can be subsequently accelerated by the 2 nd CME shock (Li et al. , 2012).

Discussion Perpendicular shock favors efficient high energy SEP acceleration: 1) If is much smaller than //, SEP can gain much more energy at quasi_perpendicular shocks. 2) Perpendicular shock requires higher injection speed thus can preferentially accelerate flare suprathermals (Jokipii et al. , 1987, APJ, 313, 842).

Movie of AIA/193 A Movie URL

Metric type II in the 2012/03/07 Event NOAA-Events-list EVENT ID: 20120307_0109 from 01: 09 – 01: 29 LEA CRSP 025 -180 II/2 1329

2012 March 07 SEP event: Two CMEs in Quick Succession! SHOCK

Two CMEs - same speed, <1 -hr apart CME 1 CME 2

Type II Burst & Shock 2012/03/08 35 h SHOCK

TNR Shock 20120308 10: 53 UT

Omni data from 20120308 to 20120309 SHOCK

Summary The two largest events in cycle 24 involve interacting CMEs. The preceding CME may enhance the turbulence upstream the second shock and increase the acceleration efficiency of the particles at the second shock.

Solar Cycle 24 SEP events CMEdate Time Vcme 2010/08/14 09: 38: 00 1056 2011/03/07 19: 43: 00 2175 2011/03/21 02: 00 1594 2011/06/07 06: 16: 00 1289 2011/08/04 03: 41: 00 2198 2011/08/09 07: 48: 00 1732 2011/09/22 10: 00 1901 2011/11/26 06: 09: 00 977 2012/01/23 02: 30: 00 1997 2012/01/27 17: 37: 00 2350 2012/03/07 00: 02: 00 2709 2012/03/13 17: 12: 41 1881 2012/05/17 01: 25: 30 1673 SEP-Int Flare_pk Loc Size 14 10: 05 N 12 W 56 C 4. 4/1093 50 20: 12 N 24 W 59 M 3. 7/1164 14 ----N 24 W 129 backside 72 06: 41 S 21 W 54 M 2. 5/1226 96 03: 57 N 16 W 38 M 9. 3/1261 26 08: 05 N 17 W 69 X 6. 9/1263 35 11: 01 N 09 E 89 X 1. 4/1302 80 07: 10 N 08 W 49 C 1. 2/1353 3000 03: 59 N 28 W 36 M 8. 7/1261 800 18: 36 N 33 W 85 X 1. 7/1263 1500 00: 24 N 17 E 27 X 5. 4/1261 500 17: 41 N 19 W 59 M 7. 9/1263 255 01: 47 N 11 W 76 M 5. 1/1476