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