Three-dimensional high-resolution
plasma bubble modeling
Tatsuhiro Yokoyama,Hiroyuki Shinagawa, and Hidekatsu Jin
National Institute of Information andCommunications Technology, Japan

Altitude

Equatorial Spread F

Frequency
Booker and Wells (1938)

ScintillationFresnel diffraction
2 DF = 2λz ≈ 400m
Serious problem forcommunication andnavigation.

Plasma Bubble
Woodman and LaHoz (1976)

Otsuka et al. (2002)

Kelley et al. (1981)

99% density depletion causes
severe scintillation.

NICT’s SEALION Observatories

Numerical Modeling of Plasma Bubbles
What we have not known:– Day-to-day variability– Precursor

We need to understand:– Background conditions to drive plasma bubble– Initial seeding at the bottomside F regionVarious observations (radars, optical imagers, rockets,satellites) have been conducted, but not answered yet(for more than 70 years!)
We are developing a new high-resolution model andintegrating it to a global ionosphere model.

Equations

Plasma density is solved from (1).

Polarization electrostatic potential is solved from (2)-(4).

Other Models

Zalesak et al. (1982)

Huba et al. (2008)Aveiro et al. (2012)Retterer (2010)

Numerical Model for Plasma Bubble



Dipole orthogonal coordinateLongitudinal coverage is 3.4° with 0.01° resolution (~1km).

O+ (F region), NO+ (E region), Fe+ (Es layer [not yet])Initial Condition

Day: March 24, 2005, Time: 20LT, Longitude: 135°
 Apply sinusoidal perturbation by lifting the density
profile to mimic LSWS.
Results (no neutral wind)

Yokoyama et al. (2014)

Vertical/Horizontal Density Distribution

Yokoyama et al. (2014)

Eastward Propagation by Neutral Wind

Eastward E field turns to be westward after 1800 s.
 Eastward neutral wind produces dynamo electric field tomove the bubble eastward.
LSWS at the Bottomside, Plumes at the Topside

Tsunoda et al. (1982)

Western Wall Unstable

Whole Atmosphere-Ionosphere Coupled Model

Ground-to-topside modelof Atmosphere andIonosphere for Aeronomy(GAIA) model Coupling with the highresolution bubble model
enables us to understandthe day-to-day variabilityof plasma bubbles.
Summary

A new three-dimensional high-resolution numerical model
to study equatorial plasma bubble (EPB) has beendeveloped with a spatial resolution of as fine as 1 km.
Turbulent plume-like irregularities can be spontaneously
generated only from large-scale perturbation at thebottomside.
Western wall is more unstable than eastern wall.
Future work: Collaboration with a global model (GAIA) for
background initial conditions (n, E, U, etc.)

Appendix

Magnetized or Unmagnetized Plasma?
(b)magnetized

(c)

(a)
unmagnetized

The lower E region consists of magnetized electrons andunmagnetized ions. → Complicated electrodynamics!

Altitude

Linear Growth Rate of Rayleigh-Taylor Instability∇n1 ∂n0  E g  −  − β L
γL =n0 ∂z  B ν in Local

 E geΣ −γ FT = EF 
Σ P + Σ P  B ν eff

Flux-tube integratedFPLarge-Scale Wave Structure (LSWS)

Tsunoda and White (1981)

Tsunoda et al. (1982)

Forming Turbulent Structures

Equipotential contours can be regarded as streamlinesof plasma in the F region.
 The top of the bubble becomes flat, where thebifurcation occurs.
Forming Turbulent Structures

After bifurcation, high density region between thetwo bubbles moves downward due to westward
polarization electric field, then pinch off the westbubble.

Forming Turbulent StructuresSecondary instability occurs along the bubble wall,
whereas pinched-off bubble stops growing.

Dependence on Zonal Resolution
1km

2km

4km

3km

5km

Dependence on Zonal Resolution

1km

3km

5km

Zonal Cut
1km

3km

5km

Topside structure depends
on the grid sizes.
 Bottomside structure andvertical velocity is similar.
