1. Extremely Fast Coronal Mass Ejection on 23 July 2012 1 Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland,20723, USA 2 NOAA Space Weather Prediction Center (Ret.), Boulder, CO, 80305, USA 3 Naval Research Laboratory, Washington, DC, 20375, USA 4 CSPAR, University of Alabama, Huntsville, Alabama, 35899, USA 5 Exploration Physics International, Inc., Huntsville, Alabama,35806, USA 6 NASA/GSFC, Greenbelt, MD, USA AOGS-AGU(WPGM), Singapore, August 13-17, 2012 K. Liou 1, M. Dryer 2, C.-C. Wu 3, S. T. Wu 4, N. Rich 3, S. Plunkett 3, L. Simpson 3, C. D. Fry 5, and K. Schenk 6 ST21-A011

2. The July 23, 2012 CME Event: Why It's Important? 1) The Sun has been active for a few years; however, the Earth is still “quiet” geomagnetically 2) This CME Initiated on the Sun's back side: no warning sign (no flare observed at the Earth); can pose danger to spacecraft 3) Extremely fast: CME-driven shock arrived at STEREO-A in ~20 h (typical 2-3 days, ~19h for the Halloween 2003 event) 4) Extremely large magnetic cloud field

3. Positions of STEREO A & B on 2012-07-23 Heliographic (HEEQ) longitude -114.819 0.000 121.246 Heliographic (HEEQ) latitude -6.979 5.088 1.750 From NASA STEREO SCIENCE CENTER STEREO-B Earth STEREO-A

4. STEREO OBSERVATIONS STEREO-A COR2 Halo CME STEREO-B COR2

5. OBSERVATION

6. 6 Global Three-dimensional MHD simulation Hakamada-Akasofu-Fry code (HAFv.2) [Fry et al., 2001] : simulating data from the Sun (2.5 solar radii, Rs) to 0.08 AU (18 Rs). A fully three-dimensional (3D), time-dependent magnetohydrodynamic (MHD) simulation code [Han et al., 1988; Detman et al., 1991, 2006] : simulating data from 0.08 AU (18 Rs) to > 1 AU Simulation model: HAF+3DMHD (H3DMHD) [Wu et al., JGR, 112,A09104, 2007; Adv. Space Rev., 40, 1827, 2007]

7. 7 Coordinates - Sun-centered spherical coordinate system (r, θ, φ) -87.5° ≤ θ ≤ 87.5° 0° ≤ ϕ ≤ 360° 2.5 R s ≤ r ≤ 18 R s (HAF) & 18 R s ≤ r ≤ 345 R s (MHD) Earth at (r, θ, ϕ ) = (215 R s, 0°, 0°) in the ecliptic plane Uniform grids and o pen boundary condition > Uniform grid step size ∆r = 3 R s, ∆θ = 5° and ∆ ϕ = 5° > θ = ±87.5° (no reflective disturbances) Simulation Domain Simulation procedure > Pre-event steady state solar wind based on solar magnetic maps > Apply a Gaussian velocity pulse at the flare site at r = 2.5 R SUN to drive the > CME (free parameters: the peak and the width of the pulse)

8. 8 Governing Equations Conservation of mass Conservation of energy* Conservation of momentum Induction equation In conservation of energy: we ignored the Coriolis force, Joule heating, thermal conduction, and viscous items. In the equations, D/Dt denotes the total derivative, ρ is the mass density, V is the velocity of the flow, p is the gas pressure, B is the magnetic field, e is the internal energy per unit mass (e = p/(γ-1)ρ), GM(r) is solar gravitational force, and γ is the specific heat ratio. For this research, we applied an adiabatic gas assumption (i.e.,γ =5/3).

9. Initial speed of Shock/CME from COR2-A (STEREO-A) Bottom: 3606 km/s Center: 2964 km/s Averages: ~3285 km/s This simulation: V peak = 3100 km/s Δ τ = 3.5 hours

10. H3DMHD Simulation Results

12. Results of H3DMHD in situ solar wind at 1 AU ~2300UT on 2012-07-23 SHOCK arrived at STEREO-A ~1000UT on 2012-07-24 SHOCK arrived at STEREO-B ~2300UT on 2012-07-25 SHOCK arrived at ACE It takes ~18 hours for Shock propagating from Sun to STEREO-A It takes ~42 hours for shock propagating from the Sun to the Earth

13. STEREO-A in situ solar wind at 1 AU STEREO-B in situ solar wind at 1 AU H3DMHD

14. STEREO-B in situ solar wind at 1 AU Density

15. 15 Discussion The CME on July 23 2012 is extremely fast, the fastest CME in cycle 24 so far The initial speed of the CME (at 2.5 solar radii) could exceed 3000 km/s > What would be the storm size if the CME hit the Earth head on? For this event B z min ~ -50 nT (Dst) p = 0.83 + 7.85×B z min (nT) ~ -392 nT [Wu & Lepping, 2005] (Dst) p = 31.9 + 6.67×B s (nT) ~ -365 nT [Bakare & Chukwuma, 2010] For the Halloween event: Dst min = -383 nT > Magnetic field at 1 AU (STEREO-A) is largest (~100 nT) |B| ~80 nT for the Halloween event.

16. Fe 0.64-0.91 MeV/n CNO 7-10 MeV/n 07/16 07/18 07/20 07/22 07/24 07/26 ~06 UT 04 UT 00 UT

17. SpacecraftCNO SEP Onset hh UT dd/mm/yy Delay (hr) CNO Magnitude (1/cm2-s-sr-MeV/n.) STEREO-A04 UT 07/23/121~10 (10 4 inc.) STEREO-B00 UT 07/24/1221~10 -3 (10 inc.) ACE06 UT 07/23/122~3x10 -4 (30 inc.) Some possibilities: 1) SEP source (shock)-STEREO connection 2) Shock strength weaken away from the CME nose 3) Efficiency of shock type (parallel and perpendicular)

18. SEP Source Connection Assume Parker Spiral At 04 UT, the CME was inside of 20 Rs 5 hours after the onset (03 UT), the CME had expanded radially and azimuthally and covered ~120° E and W of the CME onset At 08 UT, the CME had expanded over the Earth's solar foot point, consistent with the SEP observations at ACE At 12 UT, the CME and the STEREO-B are well connected but no SEP was observed until 12 hours later

19. Shock Strength Shock nose 50° E of shock Fast shock Mach no. Distance from Sun (R SUN ) Fast shock Mach no. is larger at the shock nose (9-12) than at the shock flank (5-9) No information about the shock within 18 Rs because of the limitation of the HAF code (no Temperature) Beyond 18 R SUN, shock Mach number decreases with the distance from the Sun, implying that the shock reached its maximum strength with 18 R SUN. 06 UT 23/07

20. The July 23 CME event produced a large SEP event with MeV Helium flux 30 times larger than those associated with the Halloween 2003 epoch Comparison with the Halloween CME

21. 21 Conclusions We have demonstrated that H3DMHD is capable of simulating extremely fast CMEs with speed > 3000 km/s > Good timing and magnitude match in total B and V but not n > Lack of solar wind density jump at STEREO-A at shock? The CME-associated magnetic field at 1 AU is the largest (|B| ~100 nT) in record Our preliminary and qualitative study of the SEP events at multiple spacecraft locations suggests: – Largest SEP fluxes are magnetically connected to the nose of the CME-driven shock – Azimuthal expansion of the CME caney to understand the SEP onset Large solar events do exist when no one is looking; Initiation location of CMEs is an important factor that determines geomagnetic activity Dst min vs. Longitude has a few source on backside. Required high model velocity input suggests the need for flare energy output evaluation for SWx objectives

22. THE END

23. 45º West of source location 2º West of source location 50º East of source location Background speed is faster in the west than in the nose

26. C fast = Speed of Fast Wave Δt = t 2 - t 1 Δr = r 2 - r 1 V shock = Δr/Δt M fast-shock = |V shock -V solar-wind |/C fast t = t 1 t = t 2 Wave Tracing Method (Wu et al., 1996)

27. 45º West of source location 2º West of source location 50º East of source location

28. Comparison with the Halloween CME The July 23 CME event produced a large SEP event with MeV helium fluxes 30 times larger than those associated with the Halloween epoch Peak ~30 298300302304 DOY of 2003