Finite Gyroradius Effect in Space and Laboratory 1. Radiation belt (Ring current) 2. Auroral...

Finite Gyroradius Effect in Space and Laboratory

1. Radiation belt (Ring current)

2. Auroral phenomena (Substorm current)

3. Shock acceleration and upstream

4. Ion pick-up and its acceleration

5. Reconnection

1. Foreshock ion: Earth≈Venus≠Mars.

2. Solitary structure maintained by ring current ions in the equatorial plane:

(1) same size as the auroral bulge at the ionosphere,

(2) yet gyroradius size of carrier ion, selectively 3000 km/s velocity (about 50 keV for H+, 200 keV for He+, and 750 keV for O+).

SW paraeter

BS size

nV2

(or PD)

B

(or RG)

MA c/pi

Venus 1 1 1 1 1

Earth ~ 5 ~ 0.7 ~ 0.7 ~ 1.2 ~ 2

Mars ~ 0.5 ~ 0.5 ~ 0.5 ~ 1.4 ~ 4

Gyroradius vs Bow-shock size

1. Bowshock

Earth=Venus≠Mars

(Cao et al., 2008)

V// V//

V V

cluster-3 cluster-1

SW SW

Earth Venus

Mars

IMAGE(FUV)

ions ≈ 3000 km/s

ions > 5000 km/s

2. Aurora06:42 06:46 06:4806:44

P/A

P/A

0.01~40 keV

Sudden change in fieldExB (>50 km/s) is observede.g., 57 km/s : He+ ~ 70 eV H+ ~ 17 eV

timing Sunward propagation of E

(1) single peak of E: lead by SC-3 by 1~10 sec

(2) Pi2-like rarefaction of B: simultaneous at all SC

1000~2000 km

increase in ion flux

decrease in ion flux

H+ < 90 keV

H+ > 160 keV

increase in ion flux

decrease in ion flux

He < 350 keV

He > 700 keV

O < 0.9 MeV

O > 1.4 MeV

3000 km/s = 50 keV (H), 190 keV (He), 740 keV (O) = Flux increase RB = 200 km (H), 800 km (He), 3200 km (O)

5000 km/s = 130 keV (H), 500 keV (He), 2 MeV (O) = Flux decrease

mass-dependent change

Westward moving auroral bulge at 19 MLT = a solitary structure in the magnetosphere.

This solitary structure is maintained by energetic ions of 3000 km/s speed for all ions.

Size (gradient < 500 km) of this solitary structure is comparable to the ion gyro radius of the carrier ions.

1000~2000 kmSummary

Qualitative difference within Rgyro

Distribution function Difference cannot be explained by the slight difference in effective energy between SC.

RB >> inter-SC distance cannot be due to finite gyroradius effect.

gradient is substantially large?

Energy-time dispersion (flux increase)

time-of-flight? (No) ∆T ~ 10 sec for ∆VD ~ 10 km/s source < 1000 km No

finite gyroradius? (Yes) ∆T ~ 10 sec for ∆RB ~ 100 km agree with propagation

VDB = 20~30 km/s

VDB = 10~20 km/s

VDB = 30~50 km/s

VDB = 50~100 km/s

End-Earth

ion-scale ?gradient is less than 500 km (5~10 km x 50 sec)

cf. RB (= mv/qB) for B ≈ 200 nT condition

50 keV 200 keV 1 MeV

H+ v = 3000 km/s

RB = 150 km

v = 6000 km/s

RB = 300 km

v = 14000 km/s

RB = 700 km

He+ v = 1500 km/s

RB = 300 km

v = 3000 km/s

RB = 600 km

v = 7000 km/s

RB = 1400 km

O+ v = 700 km/s

RB = 600 km

v = 1500 km/s

RB = 1200 km

v = 3500 km/s

RB = 3000 kmRB(H+) ≤ gradient ≤ RB(He+) << RB(O+)

Drift motionVB energy (mass independent)

VExB = constant (energy mass)

50 keV H+ drift = 15 km/s190 keV He+ drift = 60 km/s740 keV O+ drift = 220 km/s

Simultaneous appearance & much faster than the motion of the E-structure a solitary structure to maintain the flux peak

At around 06:44 UT, appearance of 7 keV // O+ from both hemisphere, within 40 sec difference

Aurora ion

Energetic electron vs B

observed flux

Synchronize with B field variation

|B|

µB = W/B conserved? not really

increasing flux

under µB = const df(µB) = 0

(∂f/∂W)B > 0 (∂f/∂B)W > 0

= real

Linear decoupling

observed flux after decoupling the conservation of µB = W/B