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

What is EPB? Equatorial Plasma Bubble : sharp decrease of plasma density in equatorial region

hKm Altitude Bgauss Total intensity of Earth’s magnetic induction nono cm -3 2   10 6 Concentration of neutral particles n+n+ cm Concentration of positive ions n + /n o cm -3 5   The ratio of n + to n o TnTn K1400 Temperature of neutral gas T+T+ K Temperature of positive ions TeTe K Temperature of electrons D cm0.41 Electron Debye length o cm 2   10 8 The neutral particle mean free path e+ cm 1   10 6 The electron-ion mean free path ++ cm·sec   10 5 Mean positive ion thermal velocity ee cm·sec -1 3  10 7 Mean electron thermal velocity ++ cm 5   10 2 Mean positive ion Larmor radius ee cm34 Mean electron Larmor radius +o sec -1 6   The positive ion-neutral gas collision frequency eo sec  The electron-neutral gas collision frequency e+ sec -1 3   10 1 The electron-positive ion collision frequency ++ sec -1 2   10 2 The positive ion angular gyro-frequency ee sec -1 9   10 6 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

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

①②③④⑤ Sunset-node theory of Tsunoda (1985)

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] Global verification using in-situ measurements

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

evening prereversal enhancement (EPE) vertical drift speed  F-region dynamo ; Fejer et al. [1999]

American Atlantic American Atlantic Magnetic declination angle?

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

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-dominated 2.June solstice : density-dominated 3.December solstice : possible dominated by bottomside phenomena

Plasma blobs? KOMPSAT-1 DMSP-F15

S/L distribution