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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