Internati
o
nal
Journal of Ele
c
trical
and Computer
Engineering
(IJE
CE)
V
o
l.
6, N
o
. 1
,
Febr
u
a
r
y
201
6,
pp
. 71
~81
I
S
SN
: 208
8-8
7
0
8
,
D
O
I
:
10.115
91
/ij
ece.v6
i
1.9
344
71
Jo
urn
a
l
h
o
me
pa
ge
: h
ttp
://iaesjo
u
r
na
l.com/
o
n
lin
e/ind
e
x.ph
p
/
IJECE
Analysis
of
Ion
o
s
pheric foF2 by
Solar Activity over the Korean
Peninsula
Mi
n-
Ho
Je
on
, Ch
an
g-H
e
on
Oh
Departm
e
nt o
f
E
l
ec
tric
al
, E
l
e
c
tro
n
ics
and
Commu
nication
Engineering, Kor
ea Univ
ersity
of
Techno
log
y
and
Edu
cation,
Choongnam, Korea
Article Info
A
B
STRAC
T
Article histo
r
y:
Received Aug 2, 2015
Rev
i
sed
No
v 5, 201
5
Accepted Nov 22, 2015
The F2 lay
e
r is the upper sector
of
the ionospheric F region, an
d it is ~250
km above sea level. I
t
has
a high
elec
tron d
e
nsity and thus play
s
an important
role in shortwave com
m
unicatio
ns. The va
ria
tion
s
of the critic
al frequenc
y o
f
the F2 lay
e
r (fo
F2) offer clues regarding th
e events happening
within th
e
entir
e F
2
l
a
yer
,
and
foF
2
an
al
y
s
is
is
es
s
e
ntial
for s
t
abl
e
s
hortwav
e
communications
. This stud
y
analy
zes th
e season
al and
annual v
a
riations of
the foF
2
as
well as
the react
ions
of the F
2
la
y
e
r
height at two l
o
cat
ions
in
S
outh Korea b
y
em
plo
y
ing the
m
ean a
nd stand
a
rd deviation
(SD) used in
previous
s
t
udies
. To
ens
u
re a
m
o
re elabor
ate
anal
ys
is
,
the
m
e
dian and
quartiles were used for analy
z
ing
the
ionosphere.
We thereb
y
compensate for
the l
i
m
itat
i
ons
of the m
ean
an
d S
D
in developing the SD,
despite
the
convenience of
the SD for pr
obability
analy
s
is. The app
lication of th
e
m
e
dian and qu
artiles for
the an
al
y
s
is of ionosp
h
eric d
a
t
a
l
e
d t
o
anal
y
s
is
results with grea
ter det
a
il
. Th
is was achiev
e
d b
y
determ
ining th
e
relat
i
ve SD
and con
c
urren
t
l
y
displa
yi
ng th
e o
u
tliers
and
range
of va
ria
tions.
Keyword:
Critical freque
n
cy
F2 layer
I
ono
sph
e
r
e
Sh
ort
w
ave
co
m
m
uni
cat
i
ons
So
lar activ
ity
Copyright ©
201
6 Institut
e
o
f
Ad
vanced
Engin
eer
ing and S
c
i
e
nce.
All rights re
se
rve
d
.
Co
rresp
ond
i
ng
Autho
r
:
C
h
an
g-
He
on
O
h
,
Depa
rt
m
e
nt
of
El
ect
ri
cal
, El
ect
ro
ni
cs an
d C
o
m
m
uni
cat
i
on E
ngi
neeri
n
g
Korea
University of Te
c
h
nol
o
g
y
an
d
Ed
ucat
i
o
n
,
G
a
j
e
on
-
R
i
3
07, Byun
g
c
hu
n-myu
n
,
C
h
on
an-
S
i, C
h
oon
gn
am
, 3
3
0
-
708
,
Ko
r
e
a.
Em
a
il: ch
o
h
@k
oreatech.ac.k
r
1.
INTRODUCTION
The F2 l
a
y
e
r i
s
t
h
e uppe
r sect
or o
f
t
h
e i
o
n
o
s
phe
ri
c F regi
o
n
. It
i
s
~
250
k
m
above sea l
e
vel
and pl
ay
s
an im
portant role in shor
twa
v
e comm
unications because i
t
has the hi
ghe
st electron
density in the ionosphere
.
The va
riations
in the critical f
r
eque
nc
y
(f
oF
2) o
f
t
h
e F
2
l
a
y
e
r i
ndi
cat
e t
h
e events occ
u
rring the
r
e. Ionospheric
vari
at
i
o
ns can
be di
vi
ded i
n
t
o
fo
ur t
y
pes:
di
ur
nal
,
s
eas
onal
,
l
a
t
i
t
udi
nal
,
an
d sol
a
r
-
cyclic. The foF2 above the
Ko
rea
n
Pe
ni
ns
ul
a i
s
t
h
e
m
a
xim
u
m
at
daw
n
and
m
i
nim
u
m
at
du
sk
, a
n
d
t
h
e t
i
m
e
s for
t
h
e
peak
an
d l
o
we
st
p
o
i
n
t
are subject to s
easonal variation a
nd
so
lar-activ
ity c
y
cles [
1
], [2
]. Resear
ch is conducte
d across the worl
d to
bet
t
e
r
un
der
s
t
a
nd
su
ch
f
o
F
2
v
a
ri
at
i
ons.
In
t
h
i
s
pape
r,
s
easo
n
al
an
d a
n
nual
va
ri
at
i
ons
i
n
t
h
e
f
o
F
2
a
n
d
hei
g
ht
o
f
t
h
e
pea
k
den
s
i
t
y
(
h
m
F
2) are
exam
ined at two l
o
cations
in
Ko
rea (
R
ep
.)
—Jej
u-d
o
and I
c
h
e
on
-
s
i—
during
d
i
fferen
t
so
lar-activ
ity p
e
ri
o
d
s
u
s
ing
t
h
e m
e
a
n
an
d stand
a
rd d
e
v
i
atio
n (SD).
In add
ition
t
o
th
e m
ean
and
SD, th
e m
e
d
i
an
and
qu
artiles are
u
s
ed
to exp
l
ain
th
e v
a
riatio
ns in
t
h
e fo
F2
.
In prev
i
o
us
stud
ies, t
h
e m
ean
and
SD
were
u
s
efu
l
to ind
i
cate th
e
p
r
ob
ab
ility, b
u
t th
ere
were li
mita
tio
n
s
in
d
e
v
e
lop
i
ng
th
e
SD.
In
t
h
e
p
r
esen
t stud
y,
b
y
u
s
ing
th
e m
e
d
i
an
and
q
u
a
rtiles, wh
ich
facilitate SD calcu
lation
,
th
e
rang
e
o
f
v
a
riatio
n
s
i
n
th
e
foF2 du
e to
so
lar acti
v
ities is
dem
onstrated in
greater detail
[3].
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE Vo
l. 6
,
N
o
. 1
,
Febru
a
ry
2
016
: 7
1
–
81
72
2.
DAT
A AN
D METHO
D
O
F
A
NAL
YSI
S
Th
e
d
a
ta u
s
ed
in
th
is stud
y are th
e ho
urly p
e
ak
s of
fo
F2
an
d
h
m
F2
in
Ko
rea at two
lo
cation
s
: Jeju-do
(l
at
.:
33.
4
3
° N
;
l
on.:
12
6.
3°
E;
el
ev.:
68.
0 m
)
and Ic
heo
n
-
si
(l
at
.:
37.
14
° N;
l
on.:
1
2
7
.
54
° E;
el
ev.:
68.
0 m
)
.
Raw data provided by the Korea Space
W
e
a
t
her Center
(ht
t
p://www.spac
e
w
eathe
r.go.kr/) were
use
d
, a
nd the
an
alysis r
e
su
lt
s w
e
r
e
v
e
r
i
f
i
ed
u
s
i
n
g
th
e I
n
tern
ation
a
l Ref
e
r
e
n
ce
Io
no
sp
her
i
c mo
d
e
l (I
RI-
2012
). Th
e
i
o
n
o
s
phe
ri
c va
ri
at
i
ons
ha
ve
t
u
r
n
i
n
g
poi
nt
s d
u
ri
n
g
t
h
e s
u
m
m
e
r an
d
w
i
nt
er s
o
l
s
t
i
ces an
d s
p
ri
ng
a
n
d
fal
l
equi
noxes
[4], [5]. The
r
ef
ore, we
di
vide
d the ra
w
data
into
four
a
n
a
l
ysis datasets according t
o
Korea’s
seasonal chara
c
teristics: spring (Ma
r
ch–M
ay), summ
er (
J
une–August), fall (S
eptember–Novem
ber), and
winter (December–Fe
brua
ry). Additionally, the data we
re
arra
nge
d in line with th
e solar-activity cycles in
order t
o
a
n
alyze the ionosp
heric
variations accordi
ng t
o
the sola
r
activity. Thus,
we
ge
nerated differe
n
t
d
a
tasets fo
r so
lar activ
ity: th
e lo
w-so
lar-acti
v
ity (LSA
)
dat
a
set
usi
n
g t
h
e
20
0
9
a
n
d
2
0
1
0
dat
a
, m
e
di
um
-sol
ar
-
activ
ity (MSA) d
a
taset u
s
ing
t
h
e 201
1–2
013
d
a
ta, and
h
i
gh
-so
l
ar-activ
ity (HSA)
d
a
taset u
s
ing
th
e
20
14 d
a
ta.
Fig
u
re
1
illu
strates th
e so
lar-activ
ity cycles, an
d Tab
l
e 1
p
r
esen
ts the frequ
e
n
c
y
of so
lar
flares
for each year
in
th
e
p
e
riod
o
f
ou
r inv
e
stig
atio
n.
Fig
u
re
1
.
So
lar-activ
ity cycle
Tab
l
e 1
.
So
lar
f
l
ar
es 20
10
-201
4
2010
3 step : 2 tim
e
s
2011
3 step : 10 tim
e
s
4 step : 2 tim
e
s
2012
3 step : 11 tim
e
s
2013
3 step : 14 tim
e
s
2014
3 step : 17 tim
e
s
Although the
mean is useful as a
num
erical
represe
n
tative of an e
n
tir
e d
a
taset, its
maj
o
r
li
mitatio
n
is
th
at it lo
ses its represen
tativ
e v
a
lu
e if
ex
treme v
a
lu
es of t
h
e d
a
taset are
in
clu
d
e
d
i
n
its calcu
latio
n
.
In
su
ch
cases, to
id
en
ti
fy th
e d
a
ta d
i
stribu
tio
n
p
a
ttern
, it is essen
tial to
g
e
n
e
rate a scatter d
i
ag
ram in
wh
ich
th
e
m
i
d
d
l
e
p
o
s
ition
can
be id
en
tified
as a rep
r
esen
tativ
e v
a
l
u
e, wh
ereb
y o
t
h
e
r info
rm
atio
n
,
su
ch
as th
e d
e
g
r
ee of
dispe
r
sion of
t
h
e values
scattered
around t
h
e re
prese
n
tative val
u
e, ca
n
be
acq
ui
re
d.
The
r
e a
r
e m
a
ny
m
e
t
h
o
d
s
fo
r m
easuri
ng t
h
e de
gree o
f
di
spersi
o
n
, suc
h
as t
h
e devi
ation
and
SD. In
this p
a
p
e
r, th
e
mean
and
SD, relativ
e
SD, an
d
m
e
d
i
an
and
qu
artiles are u
s
ed
in an
in
tegrat
ed
m
a
n
n
e
r for an
alyzin
g
th
e i
o
no
sp
here. The SD is
mathe
m
atica
l
ly expresse
d as
[6]:
σ
∑
(1
)
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
An
al
ysi
s
of
Io
n
o
sp
heri
c f
o
F
2
by
Sol
ar Act
i
v
i
t
y over t
h
e K
o
r
e
an
Pe
ni
ns
ul
a
(
C
han
g
-
He
o
n
Oh)
73
whe
r
e (
μ
) is the arith
m
e
tic
m
e
an
tak
e
n as t
h
e d
a
ta av
erag
e,
is an
i
n
d
i
v
i
du
al
d
a
ta po
in
t,
is t
h
e
num
ber of dat
a
poi
nt
s,
a
nd (
μ
) i
s
t
h
e de
vi
at
i
on o
f
eac
h dat
a
poi
nt
fr
om
t
h
e avera
g
e [
4
]
,
[
7
]
.
The rel
a
t
i
v
e
SD
(R
SD
) i
s
t
h
e a
b
sol
u
t
e
val
u
e o
f
t
h
e coe
f
f
i
ci
ent
of
vari
at
i
on
(C
V
)
.
It
i
s
obt
ai
ne
d
by
di
vi
di
n
g
t
h
e S
D
by
t
h
e
m
ean an
d m
u
lt
i
p
l
y
i
ng t
h
e
qu
ot
i
e
nt
by
10
0.
The R
S
D i
s
r
e
fer
r
ed t
o
as t
h
e C
V
. T
hus
,
a l
a
rge R
S
D,
whi
c
h
i
m
p
lies th
at th
e SD is
relatively larg
e co
m
p
ared
with
t
h
e
mean, indicates a large
de
gr
e
e
of
di
s
p
ersi
on
, an
d
v
i
ce
v
e
r
s
a. Becau
se t
h
e RSD
h
a
s
no
un
its, it is a conven
i
en
t m
ean
s
to
co
m
p
ar
e the d
i
sp
er
si
o
n
betw
een
d
a
tasets with differen
t
u
n
its.
Th
e RSD
of the fo
F2
u
s
ed in
th
is p
a
p
e
r is
d
e
n
o
t
ed
as
[8]
:
∙
100
(2
)
As pre
v
iously mentioned,
in cases
where
e
x
trem
e
values
are incl
ude
d i
n
its calculation, t
h
e m
ean
l
o
ses i
t
s
usef
ul
ness as a
rep
r
e
s
ent
a
t
i
v
e val
u
e
,
an
d a sca
t
t
e
r
di
ag
ram
shoul
d t
h
us be
use
d
t
o
est
i
m
a
t
e
t
h
e
deg
r
ee
o
f
d
i
spersi
o
n
. In
p
a
rticu
l
ar,
t
h
e
an
alysis
o
f
a
d
a
tase
t h
a
v
i
n
g
a symmetri
cal stru
cture
with
ou
tliers, such
as
foF2, is
greatl
y
influe
nce
d
by extrem
ely s
m
all or large
values
. In s
u
c
h
cases
,
because of the
m
e
a
n
’s
low
represe
n
tativeness of t
h
e e
n
tire sam
p
le, o
r
d
e
r statistics are often
u
s
ed
.
Qu
artiles are ob
tain
ed
b
y
d
i
v
i
d
i
ng
a d
a
taset i
n
to
qu
arters con
t
ain
i
ng
equ
a
l
o
r
qu
asi-equ
a
l
n
u
m
b
e
rs
of
d
a
ta po
in
ts, whereb
y th
e en
tire d
a
taset (1
00%) is cu
t
at 25%, 50%, and
75% (100%
= e
n
t
i
r
e di
st
ri
but
i
o
n
)
.
If a
d
a
taset is arrang
ed in
ascend
in
g ord
e
r, th
e
first (Q1)
,
second
(Q2
)
, an
d
t
h
i
r
d
(Q3)
q
u
a
rtiles correspo
n
d
t
o
the
d
a
ta po
in
ts at 2
5
%, 50
%
(m
e
d
ian), an
d
7
5
%, resp
ectiv
el
y. Th
e rang
e of th
e qu
artiles (IQR) is expressed
as
fo
llows:
Q3
Q1
(3
)
Figure
2. Average
foF2 obse
rved in
Jeju-do
according t
o
s
o
lar-aactivity cycles
3.
RESULTS
A
N
D
DI
SC
US
S
I
ONS
3.
1. I
o
n
o
s
pher
i
c foF
2
Obser
v
ations
Fig
u
r
e
2
d
e
p
i
cts th
e av
er
ag
e v
a
r
i
atio
n
s
in
th
e fo
F2
i
n
Jej
u
-d
o th
rou
ghou
t th
e
ob
serv
atio
n
p
e
r
i
od
(2
0
0
9
–
2
0
1
4
),
di
vi
de
d
i
n
t
o
l
o
w-,
m
e
di
um
-, and
hi
gh
-s
ol
ar
-act
i
v
i
t
y
peri
o
d
s:
t
h
e
LS
A
(
2
00
9 a
n
d
2
0
1
0
)
,
M
S
A
(
201
1–2
013
)
,
an
d H
S
A
(
2014
)
p
e
r
i
od
s,
r
e
sp
ectiv
ely. Figu
r
e
3
d
e
p
i
cts th
e av
er
ag
e v
a
r
i
atio
n
s
i
n
th
e f
o
F2
o
b
s
erv
e
d in
I
c
h
e
on-
si dur
ing
th
e LSA
(
201
0)
, MSA
(
201
1–2
013
), an
d HSA
(20
14)
p
e
r
i
od
s.
In
su
mm
er, foF2
falls to
a tro
ugh
at 04
:00–0
4
:
0
0
LT
(lo
c
al ti
m
e
), g
r
adu
a
lly rises to
a p
e
ak
at 15
:00–
16:
00
, a
nd
gr
a
dual
l
y
fal
l
s
f
r
o
m
19:
0
0
–
2
0
:
00
o
n
wa
r
d
s. T
h
i
s
re
fl
ect
s t
h
e
seaso
n
al
nat
u
re o
f
s
u
m
m
er, whe
n
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
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08
I
J
ECE Vo
l. 6
,
N
o
. 1
,
Febru
a
ry
2
016
: 7
1
–
81
74
day
l
i
ght
l
a
st
s l
o
n
g
e
r
t
h
a
n
i
n
ot
he
r seas
on
s [
9
]
–
[
1
1]
. I
n
wi
nt
er, t
h
e
fo
F2
fal
l
s
t
o
a t
r
o
u
g
h
at
0
6
:
0
0
,
g
r
a
dual
l
y
ri
ses t
o
a
peak
at
11:
0
0
–
1
2
:
0
0, a
nd
ra
pi
dl
y
fal
l
s
aft
e
rw
ar
d
s
. The
f
o
F
2
i
s
m
o
st
m
a
rkedl
y
i
n
fl
ue
nce
d
by
sol
a
r
act
i
v
i
t
y
i
n
wi
nter:
i
t
exhi
bi
t
s
decreased
vari
at
i
ons at
~
18:
00
un
de
r l
o
w s
o
l
a
r act
i
v
i
t
y
and at
~
22:
0
0
un
de
r
hi
g
h
sol
a
r act
i
v
i
t
y
. The va
ri
at
i
on
r
a
nge
bec
o
m
e
s
l
a
rge u
n
d
er
hi
gh s
o
l
a
r act
i
v
i
t
y
(3.
3
4
–
11 M
H
z)
, as ex
hi
bi
t
e
d by
th
e H
S
A
p
e
r
i
od
(
201
4)
, in
creasin
g
b
y
4.1
MHz com
p
ared with the va
ria
tio
n
s
du
r
i
ng
th
e LSA
p
e
r
i
od
(
3
.6
MHz) [12
]
. This d
i
screp
a
n
c
y
is attrib
u
t
ed
to th
e lo
ca
t
i
on
o
f
K
o
rea
,
w
h
i
c
h i
s
l
o
cat
ed
ne
ar t
h
e m
i
ddl
e of t
h
e
no
rt
he
rn
hem
i
sphe
re a
nd i
s
s
u
scept
i
b
l
e
t
o
t
h
e
i
n
fl
ue
nce
of s
o
l
a
r act
i
v
i
t
y
. C
o
m
p
ari
ng t
h
e f
o
F
2
va
ri
at
i
on
d
u
r
i
n
g
the LSA (2009) and
HSA (2014) periods
clearly reveals the reason for the
larger foF2 variation according to
so
lar activ
ity i
n
win
t
er. In
LSA wi
n
t
er, th
e fo
F2
exh
i
b
its su
mmer-lik
e v
a
riation
,
wh
ereb
y th
e du
rati
o
n
in
sum
m
er i
s
l
onger t
h
an i
n
wi
n
t
er, as a seas
on
al
fact
or.
H
o
w
e
ver
,
d
u
ri
ng
H
S
A
wi
nt
er
ni
g
h
t
s (2
2:
0
0
–
0
6
:
0
0)
, t
h
e
foF2 decreases
substa
ntially
com
p
ared with that in su
mmer, beca
use les
s
solar ra
diation reac
hes the
Earth,
wh
ich
is tilted
ag
ain
s
t t
h
e Sun.
Figure 3.
Average foF2
ob
se
rved in
Ic
heon-si accordin
g t
o
solar-activity cycles
During winter days,
the
fo
F2
increases t
o
a l
e
vel fa
r hi
ghe
r
than
t
h
at in s
u
mmer because
of i
n
crease
d
solar flares and the lowest
meridian
altitude
, whic
h increa
ses the solar ra
diation receive
d for the sam
e
l
e
ngt
h
o
f
tim
e. Th
is ten
d
e
n
c
y was
m
o
re rem
a
rk
ab
le in
Ich
e
on
-si th
an
in Jeju-do
.
Su
ch
a
d
i
fferen
ce is assu
m
e
d
to
becom
e
m
o
re
noticeable
at a
fre
que
nc
y
e
x
ce
eding 100 suns
pot
e
r
uptions.
3.
2.
V
a
ri
a
t
i
o
n
of
Rel
a
ti
ve
S
t
and
a
rd
De
vi
a
t
i
o
n
Fi
gu
res
4 an
d
5 sh
ow t
h
e R
S
Ds f
o
r t
h
e a
v
era
g
e f
o
F
2
v
a
l
u
es o
b
ser
v
e
d
i
n
Jej
u
-
do a
n
d Ic
heo
n
-
si
,
respect
i
v
el
y
,
w
h
i
c
h a
r
e s
h
ow
n
i
n
Fi
gu
res
2 a
n
d
3
.
Fig
u
re 4
sho
w
s th
at th
e RSDs for th
e av
erag
e fo
F2
v
a
lu
es in
Ju
ju-do
were 11
–28
% in
su
mm
er, 9
–
24
% i
n
wi
nt
e
r
,
an
d
9–
3
3
% i
n
t
h
e e
qui
no
xes
i
n
t
h
e
LS
A
pe
ri
o
d
(
2
00
9 a
n
d
2
0
1
0
)
.
In
t
h
e
M
S
A
peri
od
(
2
0
1
1
–
2
013
), th
ey w
e
r
e
1
3–2
1%, 9–2
7%, and
12
–30
%, r
e
sp
ectiv
ely, an
d
in
th
e H
S
A
p
e
r
i
o
d
(
2
0
14)
, th
ey w
e
re 1
2
–
2
0
%,
1
4–2
6
%
, an
d 15–
29
%, r
e
sp
ectiv
ely. Fig
u
r
e
5
sh
ow
s th
e
sam
e
v
a
lu
es
fo
r
I
c
heo
n
-
s
i. Th
e R
S
D
s
i
n
su
mm
er
, w
i
n
t
er
, an
d th
e equ
i
no
x
e
s w
e
r
e
1
1–1
8%,
9
–22%, and
9–
33%, r
e
sp
ectiv
el
y, in
th
e
LSA p
e
r
i
o
d
(
201
0)
.
I
n
t
h
e
MSA
p
e
r
i
od
(2
011
–20
13)
, t
h
ey w
e
r
e
9–2
5%, 11–
28
%, an
d
11
–29
%,
r
e
sp
ectiv
ely, and in
th
e
H
S
A
p
e
r
i
od (20
14)
, t
h
ey w
e
re 16
–25
%, 15–2
7%, and
1
7–32
%, r
e
sp
ectiv
ely.
Thr
o
ug
h
out
t
h
e peri
o
d
of
ob
servat
i
o
n, t
h
e hi
g
h
est
R
S
Ds
occu
rre
d at
da
wn
(0
4:
0
0
-
0
7
:
00 L
T
). T
h
i
s
im
plies that
the electron de
nsity in the F2 layer va
ries
greatly around da
wn
because of the increased
vari
at
i
o
ns i
n
t
h
e i
oni
zat
i
on
du
e t
o
sol
a
r ra
di
at
i
on,
s
o
l
a
r wi
n
d
, ge
om
agnet
i
c
act
i
v
i
t
y
, neut
ral
atm
o
sphe
re
, an
d
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
An
al
ysi
s
of
Io
n
o
sp
heri
c f
o
F
2
by
Sol
ar Act
i
v
i
t
y over t
h
e K
o
r
e
an
Pe
ni
ns
ul
a
(
C
han
g
-
He
o
n
Oh)
75
electrody
nam
i
cs. The low RSD (11–12% on ave
r
age at
1
3
:
0
0–
1
5
:
0
0 LT
) i
n
sum
m
er 201
4 (
H
S
A
) i
n
d
i
cat
es
th
at h
i
gh
so
lar
activ
ity an
d
a lo
ng
du
ration
yi
eld
a sm
all v
a
riatio
n
in th
e fo
F2
.
Figure 4.
Relative
standard de
viation of
foF2
accordi
n
g to s
o
lar-acti
v
ity cycles in Je
ju-do
Figure
5. Relative standard
de
vi
ation
of foF2 accordi
n
g to s
o
la
r-acti
v
ity cycles in Ic
he
on-si
3.
3.
An
al
ysi
s
o
f
f
o
F
2
V
a
ri
ati
o
ns
acc
o
rdi
n
g
t
o
S
o
l
a
r
-
Fl
ar
e Freque
ncy
b
y
Medi
a
n
and
Quar
ti
l
e
s
The s
o
lar-flare
fre
quencies
di
splayed in Ta
ble 1 are
closel
y associated
with the s
o
lar-ac
tivity cycle.
Und
e
r low so
lar activ
ity, less th
an
10
so
lar flares
o
c
cu
rr
e
d
. T
h
e
fre
quency of
flares i
n
creased with t
h
e s
o
lar
activity. The ionos
pheric elect
ron
de
nsity increased
i
n
p
r
o
p
o
rt
i
o
n t
o
t
h
e
f
r
e
que
ncy
of
sol
a
r fl
a
r
es.
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE Vo
l. 6
,
N
o
. 1
,
Febru
a
ry
2
016
: 7
1
–
81
76
Figure
6. Va
riations
of foF2 i
n
Je
ju
-do according to s
o
lar-flare fre
que
ncy
(m
ed
ian
,
qu
arti
les, ou
tliers, and
wh
isk
e
rs)
Fi
gu
re
7.
Va
ri
at
i
ons
of
f
o
F
2
i
n
Iche
o
n
-si
acc
or
di
n
g
t
o
s
o
l
a
r
-fl
are
f
r
eq
ue
nc
y
(m
ed
ian
,
qu
arti
les, ou
tliers, and
wh
isk
e
rs)
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
An
al
ysi
s
of
Io
n
o
sp
heri
c f
o
F
2
by
Sol
ar Act
i
v
i
t
y over t
h
e K
o
r
e
an
Pe
ni
ns
ul
a
(
C
han
g
-
He
o
n
Oh)
77
Figures 6 a
n
d 7 illustrate the iono
sphe
ric electron de
nsity
according to the
solar-
flare fre
que
ncy. The
electro
n-den
s
it
y d
i
strib
u
tion
s
in
th
e io
no
sp
here were estimated
u
s
ing
th
e
med
i
an
an
d
q
u
artiles. In
th
e graph
s
o
f
Figu
res
5
an
d
6
,
th
e t
h
ick tran
sv
erse lines with
in th
e
b
o
x
e
s
rep
r
esent th
e m
e
d
i
an
, an
d th
e
2
5
th
a
nd
7
5
th
p
e
rcen
tiles are th
e p
a
rts
b
e
low and
ab
ov
e th
e m
e
d
i
an
lin
e, resp
ectiv
ely. Th
at is, th
e
u
p
p
e
r 25
% (Q3
)
and
lowe
r 25% (Q1)
from
the
median c
o
m
p
rise the middle
50%. T
h
e ve
rtical dotted lines are re
ferred to as
whi
s
kers
. Fo
r
t
h
e up
pe
r w
h
i
s
ker
,
o
n
e of t
h
e
t
w
o val
u
e
s
i
s
t
a
ken.
In t
h
e
p
r
esence
of t
h
e
m
a
xim
u
m
val
u
e or
o
u
tliers, th
e larg
est v
a
l
u
e is tak
e
n
fro
m
th
e v
a
lu
es larg
er th
an
th
e 75
th
p
e
rcen
tile o
r
sm
a
ller th
an
t
h
e 1
.
5
in
terqu
a
rtile ran
g
e
s (1.5
× IQR). Th
e
v
a
lu
e
o
f
1.5
× IQR ap
pro
x
i
m
a
tes t
h
e SD. Th
e IQR is d
e
fin
e
d
as th
e
d
i
fferen
ce b
e
t
w
een
Q1
an
d
Q3. An
o
u
tlie
r
is d
e
fined
as a
v
a
lu
e
fallin
g
ou
tsid
e, eith
er t
h
e upp
er
or lower
1
.
5
×
IQ
R
b
ound
aries and
is ex
pressed
as an
i
n
d
i
v
i
du
al v
a
l
u
e
on
th
e
graph
.
Th
erefore, i
n
the ab
sen
ce
o
f
ou
tliers,
wh
isk
e
rs ind
i
cate o
n
l
y th
e h
i
gh
est and lo
west
v
a
lues. Moreov
er, o
u
tliers are v
a
lu
es t
h
at
d
e
v
i
ate
d
i
spropo
rtion
a
l
l
y fro
m
th
e d
i
strib
u
tion
an
d
are exp
r
essed
as p
o
i
n
t
s on
th
e g
r
ap
h. Ou
tliers in
clu
d
e
v
a
lu
es th
at
are
o
v
e
rly ex
tre
m
e, in
v
a
lid for th
e d
a
taset, or
u
n
realistic.
A
n
alyses
o
f
the io
no
sp
h
e
r
i
c data f
o
r
Jej
u
-
d
o
yield
e
d
th
e
f
o
ll
o
w
i
n
g f
i
nd
ing
s
. In
th
e
LSA
per
i
od
(2009
and
2
0
1
0
)
wi
t
h
fewe
r t
h
an
t
e
n s
o
l
a
r
fl
ares
,
a
di
st
ri
b
u
t
i
o
n
pat
t
e
r
n
of
de
nsel
y
cl
ust
e
re
d
el
ect
ro
ns a
r
ou
nd
t
h
e
m
e
di
an was
o
b
s
erve
d.
Si
nce t
h
e dat
a
fo
r
20
09 a
r
e i
n
c
o
m
p
l
e
t
e
—m
i
ssi
ng d
a
t
a
for
t
h
e
fi
rst
hal
f
of t
h
e y
ear—a
larg
er
n
u
m
b
e
r of
ou
tliers were co
m
p
ared
with
t
h
e
resu
lt
s
of
an
an
alysis p
e
rfo
r
m
e
d
o
n
a co
m
p
lete
an
nu
al
d
a
taset fo
r 2010
. M
o
r
e
ov
er, at 1
8
:
0
0–20
:00
LT in 200
9 w
i
th
m
i
ssin
g
d
a
t
a
and
i
n
2
010—an
LSA
year
w
ith
fewer t
h
an 10
so
lar flares—th
e
qu
artiles were
foun
d to
be wi
d
e
ly d
i
sp
ersed arou
nd the m
ean
, with
o
u
tliers
rarely
o
ccurri
ng
.
If th
is resu
lt is su
b
s
titu
ted
in
to
t
h
e
resu
lts presen
ted
un
der Section 3.2, it can b
e
assumed
th
at 1
8
:
00–
20
:
0
0
LT is a ti
me slo
t
in
wh
ich v
a
riatio
n
s
in
t
h
e electron
d
e
n
s
ity o
ccu
r
with
m
o
re in
ten
s
ity th
an
in
o
t
h
e
r ti
m
e
slo
t
s throug
hou
t
th
e so
lar-activ
i
t
y cycle.
A
n
alyses of
ion
o
s
ph
er
ic
d
a
ta f
o
r
20
11–
2014
, in
w
h
ich
over
10
so
lar
f
l
ares o
ccur
r
e
d
,
r
e
su
lted
in
th
e
following findi
ngs
. A large num
b
er
of outliers were
found am
ong the 2012
a
nd
2013 data points, but whe
n
the outliers were
elevate
d
, sim
ilar
ionos
pheric
elect
ron-density distribution
patterns
we
re c
o
nfirm
e
d
for
2
011
–20
13
.
In 2
014
,
wh
en
so
lar flares
o
c
cu
rred
m
o
st
freq
u
e
n
tly, ou
tliers o
c
curre
d
less frequ
en
tly, an
d
t
h
e
in
terqu
a
rtile ran
g
e
was bro
a
der th
an
t
h
at in
o
t
h
e
r years. This sig
n
i
fies th
at
th
e iono
sph
e
ric v
a
riatio
n
s
b
e
co
m
e
m
o
re intense i
n
cases
whe
r
e
solar fla
r
es
occur ove
r
15
t
i
m
e
s, owi
n
g
t
o
t
h
e
br
oade
r
di
st
ri
b
u
t
i
o
n
of
t
h
e
F
2
layer. Ich
e
on
-si ex
h
i
b
ited
similar io
no
sph
e
ric v
a
riation
s
,
bu
t ou
tliers o
c
cu
rred
m
o
re freq
u
e
n
tly. Th
is
allo
ws
the assum
p
tion that the ionos
phe
ric vari
ations are predicte
d m
o
re easily in
Jeju-do and with m
o
re diffi
culties
in
Ich
e
o
n
-si
owing
to frequ
e
n
t
ou
tlier
o
ccurren
ces.
Fig
u
re
8
.
Variatio
n
s
o
f
fo
F2
i
n
iono
sp
h
e
re ab
ov
e
Ko
rea und
er low so
lar activ
ity
(m
ed
ian
,
qu
arti
les, ou
tliers, and
wh
isk
e
rs)
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE Vo
l. 6
,
N
o
. 1
,
Febru
a
ry
2
016
: 7
1
–
81
78
3.
4. An
al
ysi
s
o
f
Se
as
on
al
f
o
F
2
Vari
ati
o
ns a
ccordi
n
g to
S
o
l
a
r
Ac
ti
vi
t
y
b
y
Medi
a
n
and
Quar
ti
l
e
s
In order to ana
l
yze seasonal foF2 variations
accord
ing to the solar activity, we deri
ved the
m
e
dian,
q
u
a
rtiles, wh
isk
e
rs, an
d ou
tliers for
2
010
(LSA), 201
2 (MSA), an
d 201
4 (HSA).
Fig
u
r
e
8
sh
ows th
e seaso
n
al f
o
F2
v
a
r
i
ations in
201
0 (
L
SA
)
ob
serv
ed
in I
c
h
e
on
-
s
i and Jeju
-do
.
A
t
bot
h l
o
cat
i
o
ns,
no
i
n
t
e
n
s
e i
o
n
o
sp
he
ri
c va
ri
at
i
ons
wer
e
o
b
se
rve
d
a
r
o
u
nd t
h
e m
e
di
an. Part
i
c
ul
arl
y
i
n
su
m
m
e
r,
in
creased
fo
F2 v
a
riation
s
were v
e
ri
fied
i
n
Ich
e
on-si. Th
is
is ascrib
ed
to
t
h
e fre
q
u
e
n
t
o
c
cu
rren
ce of
o
u
tliers
com
p
ared
with Jeju-do, wh
ere less in
ten
s
e
fo
F2
v
a
riations were
ob
served
owing
to
t
h
e low frequ
e
n
c
y o
f
o
u
tliers. Th
is
su
ppo
rts t
h
e resu
lt d
e
riv
e
d
in
Section
3
.
3
th
at io
no
sp
h
e
ri
c v
a
riation
s
can
b
e
pred
icted
m
o
re
easily in
Jeju
-do
th
an
i
n
Ich
e
on
-si.
Fi
gu
re
9.
Va
ri
at
i
ons
of
f
o
F
2
i
n
i
o
n
o
s
phe
re a
b
o
v
e
K
o
rea
u
n
d
er
m
e
di
u
m
sol
a
r act
i
v
i
t
y
(m
ed
ian
,
qu
arti
les, ou
tliers, and
wh
isk
e
rs)
Fi
gu
re 9 s
h
o
w
s t
h
e seasonal
f
o
F
2
vari
at
i
o
ns
i
n
20
1
2
(M
S
A
). The s
u
m
m
er
grap
hs s
h
o
w
t
h
at
t
h
e foF
2
slig
h
tly in
creased
with
sim
i
l
a
r v
a
riab
ility t
o
20
10
.
Sim
ila
rly, th
e g
r
aph
s
fo
r t
h
e equ
i
nox
es and
wi
n
t
er sh
ow
t
h
at
t
h
e overal
l
foF
2
i
n
crease
d
sl
i
ght
l
y
, wi
t
h
a st
ronge
r t
e
n
d
ency
i
n
wi
nt
e
r
and e
qui
no
xe
s at
08:
00
–
18:
00 a
n
d
06:
00
–
20:
00
, respect
i
v
el
y
,
un
de
r l
o
w sol
a
r act
i
v
i
t
y
. The fo
F2
vari
a
t
i
ons bec
o
m
e
far
m
o
re i
n
t
e
nse at
eq
u
i
n
o
x
e
s co
mp
ared
with
th
e LSA
(2
010
).
As in
t
h
e LS
A p
e
ri
o
d
(Fi
g
ure 8
)
, ou
tliers
occu
rred frequ
e
n
tly in
Ishe
o
n
-si i
n
th
e M
S
A
pe
rio
d
(Fig
ure
9
)
.
Fig
u
r
e
10
show
s th
e seasonal f
o
F2
v
a
r
i
atio
n
s
in
20
1
4
(
H
S
A
). Here,
c
o
m
p
ared with
the LSA and
MSA p
e
riod
s, o
u
tliers o
c
curred
with
a h
i
gh
er
freq
u
e
n
c
y. Th
e in
terq
u
a
rtile ran
g
e
s were also
larg
er. The
d
i
stin
ct feature o
f
an
alyzing
th
e iono
sph
e
ric v
a
riation
s
u
s
i
n
g
m
e
d
i
an
an
d q
u
artiles is the id
en
tification o
f
t
h
e
di
st
ri
b
u
t
i
o
n
.
I
n
sum
m
e
r, whi
l
e hei
g
ht
vari
at
i
ons
occ
u
r
ove
r
t
h
e ent
i
r
e i
o
n
o
sp
he
re, t
h
e i
o
nos
p
h
eri
c
vari
at
i
ons
h
a
v
e
a m
o
re co
n
s
isten
t
d
i
stri
b
u
tion
co
m
p
ared
with
tho
s
e in
o
t
h
e
r seasons. During
th
e an
alysis of th
e
critica
l
fre
que
nci
e
s o
f
t
h
e ent
i
r
e i
onos
p
h
ere
,
gra
d
ual
l
y
i
n
creasi
n
g t
e
nde
nci
e
s are ob
ser
v
e
d
as t
h
e sol
a
r act
i
v
i
t
y
increases
, a
nd
vice ve
rsa. T
h
e bar gra
p
h in
Figure
11
s
h
ows the
correlat
i
ons
between t
h
e critical frequencie
s
at
ho
url
y
i
n
t
e
r
v
al
s usi
ng t
h
i
s
feat
ure
.
T
h
e
gra
p
h sh
o
w
s t
h
e 2
0
14
o
u
t
p
u
t
resul
t
s
f
o
r
Je
ju
-
d
o
,
i
n
di
cat
i
ng t
h
at
v
e
ry st
rong
time-series correlatio
n
s
ex
ist
b
e
tween
th
e re
sidual se
ries,
with
decreasi
n
g tende
n
cy as
the tim
e
Evaluation Warning : The document was created with Spire.PDF for Python.
I
J
ECE
I
S
SN
:
208
8-8
7
0
8
An
al
ysi
s
of
Io
n
o
sp
heri
c f
o
F
2
by
Sol
ar Act
i
v
i
t
y over t
h
e K
o
r
e
an
Pe
ni
ns
ul
a
(
C
han
g
-
He
o
n
Oh)
79
in
terv
al i
n
creases. Th
e an
alysis of th
is
d
i
stin
ct feat
u
r
e reveals similaritie
s b
e
t
w
een
2
and
2
and
usi
n
g t
h
i
s
fi
n
d
i
n
g
,
a
n
u
n
m
easure
d
dat
a
p
o
i
n
t
2
can
be
i
n
cl
ud
ed
usi
n
g
E
q
.
(
3
).
If
E
q
.
(
3
) i
s
em
pl
oy
ed
f
o
r
pre
d
i
c
t
i
n
g
i
o
n
o
sp
he
ri
c va
ri
at
i
ons a
n
d
obt
ai
ni
n
g
m
i
ssi
ng d
a
t
a
fo
r
past
i
o
nos
p
h
eri
c
va
ri
at
i
ons
usi
n
g t
h
e dat
a
-
assim
i
l
a
t
i
on t
e
chni
que
, m
o
re
rel
i
a
bl
e anal
y
s
i
s
res
u
l
t
s
m
a
y
be de
ri
ve
d.
Fi
gu
re
1
0
.
Vari
at
i
ons
of
f
o
F
2
i
n
i
o
n
o
s
phe
re a
b
o
v
e
K
o
rea
u
n
d
er
hi
gh
sol
a
r
act
i
v
i
t
y
(m
ed
ian
,
qu
arti
les, ou
tliers, and
wh
isk
e
rs)
Figu
re
1
1
.
Inte
r-
foF
2
co
rrelation
g
r
a
p
h
at h
o
u
rly
inter
v
als
Evaluation Warning : The document was created with Spire.PDF for Python.
I
S
SN
:
2
088
-87
08
I
J
ECE Vo
l. 6
,
N
o
. 1
,
Febru
a
ry
2
016
: 7
1
–
81
80
2
2
2
/2
( t
-
2 <
N <
t
)
(3
)
4.
CO
NCL
USI
O
N
The F
2
l
a
y
e
r i
s
t
h
e up
pe
r sect
or
of t
h
e i
o
n
o
s
phe
ri
c F re
gi
o
n
,
an
d i
t
i
s
~
250
km
above sea
l
e
vel
.
It
ha
s
a hi
g
h
el
ect
r
o
n
de
nsi
t
y
and
t
h
us
pl
ay
s an
i
m
po
rt
ant
rol
e
i
n
sho
r
t
w
a
v
e c
o
m
m
uni
cat
i
ons. I
o
n
o
s
p
h
e
ri
c
var
i
at
i
ons
can be di
vide
d
into fo
ur ty
pe
s: diur
nal, seas
onal,
latitudi
na
l, and sola
r-cy
c
lic. The critical-fre
q
u
ency
(
f
o
F
2
)
vari
at
i
o
ns ab
o
v
e t
h
e K
o
rean
Peni
n
s
ul
a reac
h a pea
k
at
da
wn a
n
d fal
l
t
o
a t
r
ou
g
h
at
du
s
k
, a
nd t
h
e t
i
m
ing
fo
r
t
h
e pea
k
a
n
d t
r
o
u
gh
di
f
f
er
a
ccor
d
i
n
g t
o
se
aso
n
al
va
ri
ab
il
ity an
d
so
lar-activ
ity cycl
e. We a
n
alyzed s
easonal
and a
n
n
u
al
f
o
F
2
vari
at
i
o
ns an
d react
i
o
ns o
f
t
h
e F2 l
a
y
e
r hei
ght
at
t
w
o l
o
ca
t
i
ons i
n
Korea
(Rep.), Je
ju-do and
Ich
e
on
-si b
y
em
p
l
o
y
in
g
th
e mean
an
d
SD, wh
ich
were
u
s
ed
in
prev
iou
s
d
a
ta an
alyses. Ad
d
ition
a
lly, th
e
med
i
an
and
q
u
artiles were
u
s
ed
to
d
e
scrib
e
th
e v
a
riab
ility o
f
t
h
e fo
F2
in
th
e ion
o
s
ph
eri
c
an
alysis. Th
e
m
ean
an
d SD
u
s
ed
i
n
p
r
ev
iou
s
stud
ies
h
a
v
e
th
e ad
v
a
n
t
ag
e
o
f
easy an
alysis of
p
r
ob
ab
ility b
u
t
exh
i
b
it limitat
i
o
n
s
in
d
e
v
e
l
o
p
i
n
g
t
h
e SD. Th
e m
e
d
i
an
and
qu
artiles u
s
ed
i
n
th
e presen
t stud
y can
ind
i
cate th
e relativ
e SD and th
u
s
d
e
scri
b
e
th
e
ran
g
e
of v
a
riation
s
in
t
h
e fo
F2
d
u
e
t
o
so
lar activ
ity in
g
r
eater d
e
tail. Add
itio
n
a
lly, m
easu
r
es to
en
h
a
n
ce t
h
e reliab
ility o
f
ion
o
s
ph
eric
d
a
ta b
a
sed
o
n
th
e d
i
stin
ct feat
ure of t
h
e range o
f
v
a
riatio
n
s
were
p
r
esen
ted.
In a fo
llo
w-u
p
stud
y, t
h
e
p
r
esen
t
stud
y w
ill
b
e
ex
tend
ed
b
y
usin
g th
e equ
a
tio
n for en
su
ring
t
h
e
reliab
ility o
f
ion
o
s
ph
eric
d
a
ta
an
d co
m
p
aring th
e an
alysis resu
lts with th
e
IRI-2
012
m
o
d
e
l.
ACKNOWLE
DGE
M
ENTS
Thi
s
pa
per de
s
c
ri
bes t
h
e res
u
l
t
s
of researc
h
con
d
u
ct
ed i
n
f
u
l
f
i
l
l
m
e
nt
of wo
rk c
o
m
m
i
ssi
one
d by
t
h
e
20
1
4
I
n
f
o
rm
ati
on a
nd C
o
m
m
uni
cat
i
on Techn
o
l
o
gy
(
I
C
T
) an
d B
r
oa
dca
s
t
i
ng R
&
D P
r
og
ram
of t
h
e
Ko
rea
n
Electro
n
i
cs and
Teleco
mm
u
n
i
catio
n
s
Research
Institu
te
(ETRI),
wh
ich was
fund
ed
b
y
th
e Min
i
st
ry of
Sci
e
nce,
IC
T,
and
F
u
t
u
re Pl
a
nni
ng
(M
S
I
P
)
.
REFERE
NC
ES
[1]
A.D. Danilov
,
"Variat
i
ons in foF2 at the end of
the
1990s and beginning of th
e
2000s accordin
g to m
e
dian dat
a
"
,
Geomagnetism a
nd Aeronomy
, v
o
l. 51
, pp
. 753-7
61, dec 2011
.
[2]
D. Panchev
aa
an
d P. Mukhtarov, "A si
ngle-statio
n spectral model of the mont
hly
median foF2 an
d M (3000) F2",
Studia Geoph
ysica et Geoda
etica
, vol. 42
, pp
183
-196, Apr 1998
.
[3]
A.D. Danilov
an
d A.V. Konsta
n
t
inova, "Variatio
ns in foF2 at
the end of
th
e 1990
s and th
e b
e
ginn
ing of
the 2000s
accord
ing to
th
e
S
P
I
DR s
y
s
t
em
d
a
ta",
Geomagnetism and Aerono
my
, vol. 52
, pp
.
350-355, May
2
012.
[4]
D. Bilit
za, et al
,
"Variabil
i
t
y
of
f
o
F2 in the equ
a
t
o
rial ionosph
ere",
Advan
ces
in S
pace R
e
s
e
ar
ch
,
vol. 34, pp
. 190
1-
1906, 2004
.
[5]
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