Global Distribution of Equatorial Plasma Bubbles in the Pre-midnight Sector 3 Mar. 2005 Jaeheung...

Global Distribution of Equatorial Plasma Bubbles in the Pre-

midnight Sector

3 Mar. 2005Jaeheung PARK

What is EPB?

• Equatorial Plasma Bubble : sharp decrease of plasma density in equatorial region

-40 -30 -20 -10 0 10 20 300.0

2.0x105

4.0x105

6.0x105

8.0x105

Space Physics Package, STSAT-1Nov. 19, 2003

geographic latitude (deg)

pla

sma

de

nsi

ty (

cm-3)

h Km 400 800 Altitude

B gauss 0.5 0.4 Total intensity of Earth’s magnetic induction

no cm-3 2108 2106 Concentration of neutral particles

n+ cm-3 106 105 Concentration of positive ions

n+/no cm-3 510-3 510-2 The ratio of n+ to no

Tn K 1400 1400 Temperature of neutral gas

T+ K 1600 2200 Temperature of positive ions

Te K 2800 3000 Temperature of electrons

D cm 0.4 1 Electron Debye length

o cm 2106 2108 The neutral particle mean free path

e+ cm 1105 1106 The electron-ion mean free path

+ cm·sec-1 1.3105

1.8105

Mean positive ion thermal velocity

e cm·sec-1 3107 3107 Mean electron thermal velocity

+ cm 5102 7102 Mean positive ion Larmor radius

e cm 3 4 Mean electron Larmor radius

+o sec-1 610-2 910-4 The positive ion-neutral gas collision frequency

eo sec-1 2.5 210-2 The electron-neutral gas collision frequency

e+ sec-1 3102 3101 The electron-positive ion collision frequency

+ sec-1 2102 3102 The positive ion angular gyro-frequency

e sec-1 9106 7106 The electron angular gyro-frequency

General Features of EPB

• Scale lengths : several meters ~ several hundred kilometers

• Local time : sunset to sunrise

• Field-aligned structure

• Forming a vertical channel

• Adverse effects on the radio communication

micro-structure wave scattering

Rayleigh-Taylor instability

• When heavy fluid sits above lighter fluid in a gravitational field

• Bubbles of light fluid rise into the heavier medium

1( - ) -

FFgz F NP V U L

e mE F F F zNP eff

Generalized Rayleigh-Taylor instability

F-region Pedersen conductivity

F-region plasma density

; Kil et al. [2004]

vertical drift speed

F-region dynamo

; Fejer et al. [1999]

Recombination loss

Observational Instruments

• date of launch : Dec. 21, 1999 (near the solar maximum)

• sun-synchronous orbit : fixed at 2250 LT

• altitude : 685 km

• plasma density and electron temperature

(1) KOMPSAT-I ( KOREA )

(2) DMSP F15 (U.S.)

• sun-synchronous orbit : fixed at 2130 LT

• altitude : 840 km

• electron density, electron temperature, ion fraction, and drift speed

DMSP F15

KOMPSAT-1

Seasonal-Longitudinal distribution of EPBs

① ②③ ④ ⑤

Sunset-node theory of Tsunoda (1985)

1( - ) -

FFgz F NP V U L

e mE F F F zNP eff

Generalized Rayleigh-Taylor instability

F-region Pedersen conductivity

F-region plasma density

; Kil et al. [2004]


F-region dynamo


Global verification using in-situ measurements

Fig. GUVI disk-scan image in February and August, 2002.

evening prereversal enhancement (EPE)


F-region dynamo


0 60 120 180 240 300 3600

10

20

30

40

50

geographic longitude (deg)

0

1x105

2x105

3x105

correlation coefficient : 0.79

0.0

0.2

0.4

0.6

0.8

1.0


vz (

m/s

)ni

(cm

-3)

frac

tiona

l en

coun

ter

of E

PB

s

vernal equinoxKOMPSAT-1

0 60 120 180 240 300 3600

10

20

30

40

50


0

1x105

2x105

3x105

0.0

0.2

0.4

0.6

0.8

1.0

vz (

m/s

)ni

(cm

-3)

frac

tiona

l en

coun

ter

of E

PB

s

vernal equinoxDMSP F15



0 60 120 180 240 300 3600

10

20

30

40

50

0

1x105

2x105

3x105

0.0

0.2

0.4

0.6

0.8

1.0


June solsticeKOMPSAT-1



frac

tiona

l en

coun

ter

of E

PB

sni

(cm

-3)

vz (

m/s

)

0 60 120 180 240 300 3600

10

20

30

40

50

0

1x105

2x105

3x105

0.0

0.2

0.4

0.6

0.8

1.0


June solsticeDMSP F15

frac

tiona

l en

coun

ter

of E

PB

sni

(cm

-3)

vz (

m/s

)



0 60 120 180 240 300 3600

10

20

30

40

50

0

1x105

2x105

3x105

frac

tiona

l en

coun

ter

of E

PB

sni

(cm

-3)

vz (

m/s

)


0.0

0.2

0.4

0.6

0.8

1.0

December solsticeKOMPSAT-1



0 60 120 180 240 300 3600

10

20

30

40

50

0

1x105

2x105

3x105

frac

tiona

l en

coun

ter

of E

PB

sni

(cm

-3)

vz (

m/s

)


0.0

0.2

0.4

0.6

0.8

1.0

December solsticeDMSP F15



American

Atlantic American

Atlantic

Magnetic declination angle?

Fig. Composite GUVI 135.6-nm scan image at 2150 LT on Jan. 29, 2002.

The background plasma density is higher in the south

But the northern anomaly is stronger than the southern anomaly

TIMED/GUVI disk-scan images at nighttime show large longitudinal and seasonal variations in the OI 135.6-nm radiance. The intensity of the anomaly does not precisely conform to the intensity of the background. The GUVI observations indicate that the F-region morphology near the F peak can be different from the morphology on the topside that has been extensively studied using DMSP data.

0.0 0.2 0.4 0.6 0.8 1.0

1x105

2x105

3x105

correlation coefficient: 0.58

pla

sma

de

nsi

ty (

cm-3)

fractional EPB encounter

DMSP F15

green : vernal equinoxred : June solsticeblue : December solstice

0.0 0.2 0.4 0.6 0.8 1.010

20

30

40

50

DMSP F15

green : vernal equinoxred : June solsticeblue : December solstice

fractional EPB encounterve

rtic

al d

rift

sp

ee

d (

m/s

)

correlation coefficient: 0.69

Conclusions

1. The S/L distribution of EPBs was common to both KOMPSAT-1 and DMSP F15, whose orbits have different local times and altitudes.

2. The importance of ambient plasma density and vertical drift speed was verified globally.

3. Their relative influences were proved to be dependent on the season.

1. March equinox : drift-dominated2. June solstice : density-dominated3. December solstice : possible dominated by bottomside

phenomena

Plasma blobs?

-40 -30 -20 -10 0 10 20-1

0

1

2

3

1000

1200

1400

1600

1800

ele

ctro

n te

mp

era

ture

(K

)

pla

sma

de

nsi

ty (

105

/cc)

geographic latitude (deg)26 Feb 2001

plasma blob

-40 -30 -20 -10 0 10 20-100000

0

100000

200000

300000

1000

1200

1400

1600

1800

10 Feb 2001

plasma blob

ele

ctro

n te

mp

era

ture

(K

)

pla

sma

de

nsi

ty (

/cc)

geographic latitude (deg)

KOMPSAT-1 DMSP-F15

S/L distribution

Global Distribution of Equatorial Plasma Bubbles in the Pre-midnight Sector 3 Mar. 2005 Jaeheung...

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