A statistical study of equatorial plasma
bubble observed by GPS ROTImeasurement along 100oE – 118oE
longitude over the years 2008 – 2013.

Suhaila M Buhari1,2, Mardina Abdullah2, Tatsuhiro
Yokoyama1, Alina Marie Hasbi2, Yuichi Otsuka3, Michi
Nishioka1 and Takuya Tsugawa1
1 National Institute of Information and Communications Technology
2 Space Science Centre, Universiti Kebangsaan Malaysia
3 Solar-Terrestrial Environment Laboratory, Nagoya University

Outline• Two-dimensional structure of EPB.
• Climatology of EPB from previous studies• Data and observation• Results1) Occurrence day of EPB vs the successive EPBs

2) The dependency of EPB with solar activity, seasons,latitude and longitude.
• Summary• Future work

EQUATORIAL PLASMA BUBBLE (EPB)

Tsunoda, 2015*• EPB is 3D structure of depleted plasma density associated with ionosphericirregularities that and could degrade radio and GPS navigation or any system.

• EPB is initiated near the magnetic dip equator through Rayleigh Taylor instability
mechanism and drift zonally.

• Rayleigh Taylor instability – perturbation acting at the bottomside of the F layer.
• The seeds of EPB can be the convection of gravity waves from troposphere or thepropagating waves (Kelley at al 1981) such as large scale wave structure(Tsunoda, 2005 & 2008).

• The seeds is responsible for the day-to-day variability of EPB occurrence is still notcompletely understood.

Climatology of EPB from previous studies

EPBs from 1989-1992 - Global
UltravioletImager(GUVI)
onboard of TIMED satellite.
(Gentile et al., 2006)

EPBs observed from GUVI (20022007) with SSN. (Comberiate &Paxton , 2010)

EPB observed from JULIA radar in Peru (1996-2000) withsolar flux, φ. (Hysell and Burcham, JASTP, 2006

The
observation
opticalimager in Brazil (Sahai etal.,
2000)
shows
theoccurrence of EPB has
similar characteristics for
HSA and LSA

Occurrence rate of EPB using GPSreceiver• The global occurrence rate ofEPB observed by a single GPS
receiverfrom
2000-2006.
[Nishioka et al. 2008]• The different climatology due
to the longitudinal orientationsof magnetic equator.
• EPB tends to occur during thealignmentofthesolar
terminator with the magneticfield lines. [Tsunoda, 1985]• In this study we present theoccurrence rate of EPB using
high-density GPS receivers inSoutheast Asia.

THE TWO-DIMENSIONAL OBSERVATIONOF EPB IN SOUTHEAST ASIA●●●The GPS data was collected from theDepartment of Survey and Mapping,
Malaysia for the years 2008 – 2013
The receivers network called Malaysia
Real-Time Kinematics GNSS Network(MyRTKnet) has 78 GPS receivers are
distributed along 100oE to 120oE with
~50-100 km spacing.
TEC - the integrated electron density
along the signal path ~ the amount ofphase advances cause by the ionosphere.

2  f1  f 2 TEC = L1  λ1  L2  λ2 22k  f1  f 2 2●The irregularities in ionosphere can cause
rapid change in amplitude and phase ofthe TEC

TEC t + Δt   TEC t ROT =Δt

ROTI KEOGRAM AT 4oN• Obtain time-continuous
observation of EPB with highspatial resolution and broad
geographical coverage.
• East-west ROTI keogram iscreated by taking one slice ofROTI (e.g. at 4oN) and arrange
it for every 5 minutes.
• ROTI keogram shows the timelongitudinal variations of EPB
over 92oE – 120oE.

Buhari et al., 2014

EPB & SSN

Solar activity

EPBs tend to occur in all longitude during the high solar activity

Summary• We have shown the occurrence rate of EPB using high-density
GPS receivers in SEA.
• We found high occurrence rate (>90%) during high solar
activity, which is consistent with past observation by single
GPS receiver in SEA.

• We found a considerably high occurrence rate during low solar
activity (60%-80%) and is consistent with past ground based
observation from Brazil (>60%) and Peru (>50%).
• The occurrence rate observed by TIMED satellite might have
low spatial resolution or too high to observe the EPB at lowaltitude• The occurrence day of successive EPBs are in agreement withsolar activity shows the EPB tends to propagate in theionosphere during high solar activity.

EPB & Kp Index

Solar activity

EPBs tends to occur in all longitude during the high solar activity