Response of the Magnetosphere and Ionosphere to

Solar Wind Dynamic Pressure Pulse

Response of the Magnetosphere and Ionosphere to

Solar 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

2009 UN BSS & IHY Workshop, September 21-25, 2009

IntroductionIntroduction

The interaction of the solar wind with Earth’s magnetosphere produces various phenomena, such as substorms and aurora, in the polar region.

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.

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

Pure Northward By T. Ogino

θY

Z

Tilt angle 0°

Tilt angle 30°

Effect of the dipole tilt angleEffect of the dipole tilt angle

When the northern hemisphere is summer, the dayside reconnection occurred slightly below the magnetic equator in the start from 30 degree.

Dayside Reconnection rate :30 tilt ~ 0.84 times 0 tilt

Configuration of the magnetic field lines

Southward IMF (315°) + dipole tilt (30°)

Northward IMF (45°) + dipole tilt (30°)

Configuration of the magnetic field lines

[Park et al. 2006, 2009]

# A quasi-steady state configuration usually resulted after about 3 hours in real time.

X

Z

X

Y

1. Dusk sector (northern hemisphere)2. Move to dawn in the dayside 3. Come back to dusk in the tail4. Tail reconnection successively occurs in the slant and elevated plasma sheet.

Effect of the dipole tilt and IMF conditionEffect of the dipole tilt and IMF condition

Bz

By

Bz

By

Northward IMF (45°) + dipole tilt (30°)Southward IMF (315°) + dipole tilt (30°)

Electric field |E| and Resistivity electric field

0.1 times

E

ηJ

J|| J┴

E ηJ

J||

J┴

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].

Northward IMF (45°) + dipole tilt (30°)

In a view form the dusk

In a view form the top

In a view form the Sun

Northward IMF (45°) + dipole tilt (30°)Southward IMF (315°) + dipole tilt (30°)

The reason of different J|| in the reconnection region between the southward and northward IMF condition

Orientation of IMF and dipole tilt (30)Orientation of IMF and dipole tilt (30)

Electric field |E| (E = -VB+ J)

• EAPN > EAPS

The electric field in the northern hemisphere is almost 3 times larger than that in the southern hemisphere for 45 .

Polar cap potential saturation process and dayside magnetic reconnection enhancement [Boudouridis et. 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

The effect of sudden enhancements of solar wind dynamic pressure on the magnetosphere and ionosphere

Simulation MethodSimulation Method

The number of grid points (nx, ny, nz) = (300, 100, 100) with a grid spacing of 0.3 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

Simulation conditionSimulation condition

Condition 1 : constant Bz and variable dynamic pressure

Condition 4 : Bz south to northward

60 min t

5

10

[/cm-3]

Bz = -2 nT and -10 nTdensity

-2

-10

Density = 5 and 10 /cm-3

Bz[nT]

60 min t

Condition 2 : more southward Bz and constant dynamic pressure

Condition 3 : Bz change with dynamic pressure

60 min t

5

10

[/cm-3]

density

Bz =-2 nT

Bz =-10 nT

60 min t

5

10

[/cm-3]density

Bz =0nT

Bz =-10 nT

tpulse -5m

tpulse +5m

tpulse +10m

tpulse +15m

tpulse +20m

Bz = -2 nT Nsw = 5/cc

Bz = -2 nT Nsw = 10/cc

Red (dawn to dusk )Blue (dusk to dawn)

Time evolution of the electric field in XY planeSimulation ResultsSimulation Results

Bz = -10 nT Nsw = 5/cc

Bz = -10 nT Nsw = 10/cc

30 20

-60 X 0

-20

Y 0

(RE)

a) a large viscous cell near the magnetopause but very little convection in tail

b) large convection in tail

Condition 1

tpulse -5m

tpulse +5m

tpulse +10m

tpulse +15m

tpulse +20m

Time evolution of perpendicular current density

Bz = -2 nT Nsw = 5/cc

Bz = -2 nT Nsw = 10/cc

Bz = -10 nT Nsw = 5/cc

Bz = -10 nT Nsw = 10/cc

X=-15RE X=-15RE

large viscous cell

Cross section in tail

tpulse -5m

tpulse +5m

tpulse +10m

tpulse +15m

tpulse +20m

Time evolution of plasma pressure

Bz = -2 nT Nsw = 5/cc

Bz = -2 nT Nsw = 10/cc

Bz = -10 nT Nsw = 5/cc

Bz = -10 nT Nsw = 10/cc

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

X (RE)

Y

(RE)

20

-20

30 -60

Bz = -10 nT, Nsw = 5/cc

Bz = -10 nT, Nsw = 10/ccBz = -2 nT , Nsw = 5/ccBz = -2 nT, Nsw = 10/cc

Vx > 0 tailwardVx < 0 earthward

Tail reconnection 14~15 RE

Tail reconnection ~11 RE

Earthward flow has ~50 km/s, while the tailward flows ~150km/s (20 min)

Earthward flow has ~300 km/s, while the tailward flows ~400km/s (10min)

little change J (J~4) increases J ~ 3times J

(P~28)(P~100)

Bz = -10 nT Nsw = 10/cc

Bz = -2 nT Nsw = 5/cc

Condition 3

tpulse -5m

tpulse +5m

tpulse +10m

tpulse +15m

tpulse +20m

Time evolution of the electric field and plasma pressure in XY plane

Compress by dynamic pressure

Small convection in tail

Location of Bowshock : 14.8RE ->13.5RE

Location of Dayside Magnetopause :11RE -> 9RE

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)

(P~40)

little change J (J~6)

Vx > 0 tailwardVx < 0 earthward

SummarySummary

We have studied magnetospheric phenomena by 3D MHD simulation when the IMF Bz and solar wind components exist.

a) 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 1

Condition 3IMF 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

Thank you very much for your attention

tpulse -5m

tpulse +5m

tpulse +10m

tpulse +15m

tpulse +20m

Bz = -2 nT Nsw = 5/cc

Bz = -2 nT Nsw = 10/cc

Bz = -10 nT Nsw = 10/cc

Different pulse condition

tpulse -5m

tpulse +10m

tpulse +15m

tpulse +20m

Bz = -2 nT Nsw = 5/cc

Bz = -10 nT Nsw = 5/cc

Red (dawn to dusk )Blue (dusk to dawn)

Time evolution of the electric fieldSimulation ResultsSimulation ResultsBz = -2 nT Nsw = 10/cc

Bz = -10 nT Nsw = 10/cc

a) very little convection in tail

b) little convection in tail

30 20

-60 X 0

-20

Y 0

(RE)

Condition 2

Bz = -10 nT Nsw = 10/cc

Bz = -2 nT Nsw = 5/cc

Bz = 0 nT Nsw = 5/cc

Bz = -10 nT Nsw = 10/cc

Condition 3 Condition 4