Response of the Magnetosphere and Ionosphere to Solar Wind Dynamic Pressure Pulse

1. 2009 UN BSS & IHY Workshop, September 21-25, 2009 Response of the Magnetosphere and Ionosphere toSolar Wind Dynamic Pressure Pulse KYUNG SUN PARK1, TATSUKI OGINO2, and DAE-YOUNG LEE3 1School of Space Research, Kyung Hee University, Korea2Solar-Terrestrial Environment Laboratory, Nagoya University, Japan 3Dept. Astronomy and Space Science, Chungbuk National University, Korea

2. Z Introduction θ Y The interaction of the solar wind with Earth’s magnetosphere produces various phenomena, such as substorms and aurora, in the polar region. The orientation of the IMF has significant effects on convection pattern and the FAC system in the magnetosphere. [Fairfied and Cahill, 1966; Reiff and Bursh, 1985: Cowley and Lockwood, 1992] . Pure Southward When the IMF turns southward, the energy of the solar wind is efficiently trapped by reconnection in the magnetosphere, and convection and currents within in the magnetosphere increase. Pure Northward By T. Ogino Pure Northward

3. Effect of the dipole tilt angle Configuration of the magnetic field lines Tilt angle 0° Dayside Reconnection rate : 30 tilt ~ 0.84 times 0 tilt Tilt angle 30° When the northern hemisphere is summer, the dayside reconnection occurred slightly below the magnetic equator in the start from 30 degree.

4. Effect of the dipole tilt and IMF condition Southward IMF (315°) + dipole tilt (30°) # A quasi-steady state configuration usually resulted after about 3 hours in real time. Z X [Park et al. 2006, 2009] X Configuration of the magnetic field lines Y 1. Dusk sector (northern hemisphere) 2. Move to dawn in the dayside 3. Come back to dusk in the tail 4.Tail reconnection successively occurs in the slant and elevated plasma sheet. Northward IMF (45°) + dipole tilt (30°)

5. Electric field |E| and Resistivity electric field Bz By Bz By Northward IMF (45°) + dipole tilt (30°) Southward IMF (315°) + dipole tilt (30°) E ηJ E J┴ ηJ J|| J┴ J|| 0.1 times EAPN (1.2)  EAPS (1.1) ≥ EME(0.2) ≥ ESS (0.1 mV/m) EAPN , EAPS (0.4) ≥ EME, ESS (0.15 mV/m) The parallel component of the current (J||) in the southern hemisphere is larger than northern hemisphere when the dipole tilt is positive. The feature is different result from the southward IMF condition [Park et al., 2006, 2009].

6. Northward IMF (45°) + dipole tilt (30°) In a view form the dusk In a view form the Sun In a view form the top

7. The reason of different J|| in the reconnection region between the southward and northward IMF condition Northward IMF (45°) + dipole tilt (30°) Southward IMF (315°) + dipole tilt (30°)

8. Orientation of IMF and dipole tilt (30) Electric field |E| (E = -VB+ J) • EAPN > EAPS The electric field in the northern hemisphere is almost 3 times larger than that in the southern hemisphere for 45.

9. The effect of sudden enhancements of solar wind dynamic pressure on the magnetosphere and ionosphere • Polar cap potential saturation process and dayside magnetic reconnection • enhancement [Boudouridiset. al., 2004] • Polar cap (PC) index enhancement [Lukianova, 2003] • Sawtooth oscillations in energetic particle flux and magnetic field at • geosynchronous orbit [Lee et. al., 2004] • Auroral-region disturbance [Lyons et al., 2005] • Substorm triggering Simulation Method • The number of grid points • (nx, ny, nz) = (300, 100, 100) with a grid spacing of0.3 RE. • Solar wind parameters: • IMF |B| = 0 nT, 2 nT and 10 nT • Solar wind density： nsw = 5/cc and 10/cc • Solar wind velocity： Vsw = 300 km/s

10. Simulation condition Condition 1 : constant Bz and variable dynamic pressure Condition 2 : more southward Bz and constant dynamic pressure Density = 5 and 10 /cm-3 [/cm-3] [/cm-3] [/cm-3] 10 10 10 -10 Bz = -2 nT and -10 nT density density 5 5 5 density Bz [nT] -2 60 min t 60 min t 60 min t Condition 3 : Bz change with dynamic pressure Condition 4 : Bz south to northward 60 min t Bz = -10 nT Bz = -10 nT Bz = 0nT Bz = -2 nT

11. Simulation Results Time evolution of the electric field in XY plane tpulse -5m Bz = -10 nT Nsw = 5/cc Condition 1 Bz = -2 nT Nsw = 5/cc Red (dawn to dusk ) Blue (dusk to dawn) tpulse +5m Bz = -10 nT Nsw = 10/cc Bz = -2 nT Nsw = 10/cc tpulse +10m • a large viscous cell near the magnetopause but very little convection in tail • large convection in tail tpulse +15m -20 tpulse +20m Y 0 (RE) 20 30 X 0 -60

12. Time evolution of perpendicular current density Bz = -2 nT Nsw = 5/cc Bz = -10 nT Nsw = 5/cc tpulse -5m Bz = -2 nT Nsw = 10/cc Bz = -10 nT Nsw = 10/cc tpulse +5m tpulse +10m large viscous cell tpulse +15m tpulse +20m X=-15RE X=-15RE Cross section in tail

13. Time evolution of plasma pressure Bz = -2 nT Nsw = 5/cc Bz = -10 nT Nsw = 5/cc tpulse -5m Bz = -2 nT Nsw = 10/cc Bz = -10 nT Nsw = 10/cc tpulse +5m Location of Bowshock : 15.4 -> 14RE Location of Dayside Magnetopause : 11.5RE -> 10RE Location of Bowshock : 14.8RE ->13RE Location of Dayside Magnetopause : 11RE -> 9RE tpulse +10m tpulse +15m -20 Y (RE) 20 tpulse +20m 30 X (RE) -60

14. Bz = -10 nT, Nsw = 5/cc Bz = -2 nT , Nsw = 5/cc Bz = -2 nT, Nsw = 10/cc Bz = -10 nT, Nsw = 10/cc Vx > 0 tailward Vx < 0 earthward Tail reconnection ~11 RE Tail reconnection 14~15 RE Earthward flow has ~300 km/s, while the tailward flows ~400km/s (10min) Earthward flow has ~50 km/s, while the tailward flows ~150km/s (20 min) (P~100) (P~28) little change J (J~4) increases J ~ 3times J

15. Condition 3 Time evolution of the electric field and plasma pressure in XY plane Bz = -2 nT Nsw = 5/cc tpulse -5m Bz = -10 nT Nsw = 10/cc tpulse +5m tpulse +10m Compress by dynamic pressure Small convection in tail tpulse +15m Location of Bowshock : 14.8RE ->13.5RE Location of Dayside Magnetopause : 11RE -> 9RE tpulse +20m

16. Bz = -2 nT , Nsw = 5/cc Bz = -10 nT, Nsw = 10/cc Tail reconnection ~12 RE Earthward flow has ~75 km/s, while the tailward flows ~150km/s (20 min) Vx > 0 tailward Vx < 0 earthward (P~40) little change J (J~6)

17. Summary We have studied magnetospheric phenomena by 3D MHD simulation when the IMF Bz and solar wind components exist. Condition 1 • IMF Bz=-2nT, density=5/cm-3 -> IMF Bz =-2nT, density =10/cm-3 • A large viscous cell near the magnetopause but very little convection in tail Tail reconnection occur at 14-15RE after 20 min Earthward flow ~ 40 km/s and tailward flow ~150km/s) • Location of Bowshock ~14RE and Magnetopause location ~ 10RE • Small tail current • b) IMF Bz=-10nT, density=5/cm-3 -> IMF Bz=-10nT, density = 10/cm-3 • A large convection in tail (after 15 min) Tail reconnection occur at ~11 RE • Earthward flow ~300 km/s, while the tailward flows ~400km/s (10min) • Bowshock ~ 13RE and Magnetopause ~9RE • Tail current increase about 3times Condition 3 IMF Bz=-2nT, density=5/cm-3 -> IMF Bz=-10nT, density = 10/cm-3 very little convection in tail (after 20 min) Tail reconnection occur at ~12 RE Earthward flow ~70 km/s, while the tailward flows ~150km/s Location of Bowshock ~ 13.5RE and Magnetopause ~9RE Small tail current

18. Thank you very much for your attention

19. Different pulse condition Bz = -2 nT Nsw = 5/cc tpulse -5m Bz = -10 nT Nsw = 10/cc tpulse +5m Bz = -2 nT Nsw = 10/cc tpulse +10m tpulse +15m tpulse +20m

20. Simulation Results Time evolution of the electric field Condition 2 tpulse -5m Bz = -2 nT Nsw = 10/cc Bz = -2 nT Nsw = 5/cc Bz = -10 nT Nsw = 10/cc Bz = -10 nT Nsw = 5/cc tpulse +10m tpulse +15m tpulse +20m -20 Y 0 (RE) • very little convection in tail • little convection in tail Red (dawn to dusk ) Blue (dusk to dawn) 20 30 -60 X 0

21. Condition 3 Condition 4 Bz = -2 nT Nsw = 5/cc Bz = -10 nT Nsw = 10/cc Bz = -10 nT Nsw = 10/cc Bz = 0 nT Nsw = 5/cc