A Scinda-Gpsstudy Ofequatorialplasma Bubblesover Kisumu, Kenyaduring2013 -2014 Period

ABSTRACT

The ionosphere is the ionized portion of the atmosphere that stretches from about 50 km to

1000 km above the ground. It plays a very important role in the solar effects felt on Earth.

Despite various studies having been carried out on occurrence of Equatorial plasma

bubbles (EPBs) in Africa, more research needs to be done within East Africa since the

ionosphere is a highly variable medium resulting from ionizing radiation from the Sun and

changes from region to region. The problem in this study was to investigate the occurrence

of EPBs over Kisumu, Kenya during selected quiet and storm days between 1st January

2013 to 31st December 2014, which was a high solar activity period for solar cycle 24

using TEC and amplitude scintillation (S4) data. This study was carried out by analyzing

Receiver Independent Exchange (RINEX) Total Electron Content (TEC) data retrieved

from the Kisumu high data rate NovAtel GSV4004B SCINDA-GPS receiver situated at

Maseno University (Geographic coordinates: 0.02oS, 34.6oE; geomagnetic coordinates,

9.64oS, 108.59oE). The TEC data was unzipped using WinRAR program and processed

using Gopi software. The resulting output data was used to plot Vertical Total Electron

Content (VTEC) & S4 plots and ROT & ROTI plots all against universal time (UT) for

selected quiet and storm days of the year 2013 and 2014. The results obtained from this

study shows notable TEC depletions followed by TEC enhancement which corresponded

with enhanced S4 after local sunset for most of the selected quiet and storm days of 2013

and 2014. An average TEC value of 59 TECU was attained in the equinoctial period

(March, April, August and September) while an average TEC value of 55 TECU was

attained in the solstice period (June, July, November and December). There was an

increased ROT fluctuation which corresponded with high ROTI values after local sunset

for most selected quiet and storm days. The percentage EPB occurrence was 6.49% in the

year 2013 and 4.32% in the year 2014. The storm days had EPB occurrence of 21.42% in

the year 2013 and 21.88% in the year 2014 while the quiet days which had 18.75% in the

year 2013 and 7.89% in the year 2014. The storm period had a higher percentage EPB

occurrence than the quiet period and was attributed to the effect of prompt penetration

electric field (PPEF) which is enhanced during storms, hence increasing the vertical E x B

drift. Seasonal EPB occurrence pattern during quiet and disturbed geomagnetic period was

also brought out with March equinox having higher percentage EPB occurrence of 33.33%

in the year 2013 and 30.76% in the year 2014 while June solstice had the lowest

percentage of EPB occurrence with 6.67% in the year 2013 and 7.69% in the year 2014. In

conclusion, this study confirms the presence of EPBs over Kisumu, Kenya in both quiet

and storm days of 2013 and 2014. This study was limited to data from a single SCINDAGPS

station in Kenya, hence future work should involve more SCINDA stations in East

Africa and an extension of this study should involve correlation between ROTI daily

variability of E x B vertical plasma drift and F2 layer changes.