Ionospheric Research at SANSA using Ionosondes, HF Doppler ...

Ionospheric Monitoring: Africa
Workshop
24-25 January 2013
Ionospheric Research at
SANSA using Ionosondes, HF
Doppler Radar and GPS
Zama T Katamzi, Lee-Anne McKinnell, John Bosco
Habarulema, Nicholas Ssessanga and Vumile
Tyalimpi

Latitude [degrees]
Instruments - Ionosondes
-18
-20
-22
Madimbo
-24
-26
-28
-30
Louisvale
• Frequency range: 0.1 – 30 MHz
• Sampling period: 15 minutes
• Currently only three radars are
working
• Measures only bottomside
ionosphere
-32
-34
-36
Grahamstown
Hermanus
15 20 25 30 35
Longitude [degrees]

Instruments – HF Doppler Radar
• Three transmitter:
CPN, WCT, ARN
• 1 receiver: HER
• Operating freq:
3.594 MHz ± 4 Hz
• Sampling freq:
315.1 Hz
– 16384 data
samples per
minute
• Operation: since
May 2010
93 km
87 km
94 km
System developed at the Institute of Atmospheric Physics, Czech Republic;
Chum et al (2010) in JGR, 115, A11322

Spectrogram

Instruments – GPS Receivers
• About 60 GPS receivers in South Africa
• Data access through the National Geospatial Information’s Trignet server

Ionospheric wave structures
• Quasi periodic (wave-like) perturbations, e.g. traveling ionospheric
disturbances (TIDs) in ionospheric measurement a common feature, even
during geomagnetically quiet conditions
• Important questions relates to sources and energy transportation
• Questions can be answered by extensive observations and characterisations
• Characterisation will ultimately be good for space weather applications, such
as greater accuracy in predictions of useful frequencies.
• Continuous wavelet transform used to obtain temporal variation of period of
wave structures Morlet wavelet

fof2 [MHz]
Period [hours]
foF2 [MHz]
period [hours]
TIDs with Ionosondes
4
3
2
GRHM 31-Mar-2001
6
4
2
4
3
2
1
GRHM 18-Aug-2011
1.2
1
0.8
0.6
0.4
0.2
4 6 8 10 12 14 16 18 20
4 6 8 10 12 14 16 18 20
15
10
5
0
4
3
2
GRHM
31-Mar-2001
2 4 6 8 10 12 14 16 18 20 22 24
Time [UT]
4 6 8 10 12 14 16 18 20
8
6
6
4
4
2
2
4
3
2
1
GRHM
18-Aug-2011
2 6 8 10 12 14 16 18 20 22 24
4 6 8 10 12 14 16 18 20
Time [UT]
1.2
1
0.8
0.6
0.4
0.2
10
7
8
6
6 8 10 12 14
6
5
10 12 14

Statistics for year 2001
Grahamstown Hermanus Louisvale Madimbo Total %
Total data 240 ---------- 85 146 471 ----
Total wave activity 30 ---------- 3 16 39 8
Summer (Dec-Feb) 5 ---------- 1 0 6 15
Autumn (Mar-May) 6 ---------- 1 4 11 28
Winter (Jun-Aug) 14 ---------- 0 11 25 64
Spring (Sep-Nov) 5 ---------- 1 1 7 18
Average Periods Grahamstown Hermanus Louisvale Madimbo
Summer 2.0 – 3.0 ---------- 2.5 – 3.5 ----------
Autumn 2.5 – 3.5 ---------- 2.5 – 3.0 3.0 – 3.5
Winter 2.5 – 3.0 ---------- ----------- 2.5 – 3.5
Spring 2.0 – 3.0 ---------- 2.5 – 3.0 2.5 – 3.0
• Only large scale waves detected (i.e periods > 1 hr)
• Most wave activity in winter and longer periods in autumn

Statistics for year 2011
Days Grahamstown Hermanus Louisvale Madimbo Total %
Total data 179 175 145 134 633 ---
Total wave activity 26 21 09 15 71 11
Summer (Dec-Feb) 5 3 0 2 10 14
Autumn (Mar-May) 9 8 2 3 22 31
Winter (Jun-Aug) 12 8 7 9 36 51
Spring (Sep-Nov) 0 2 0 1 3 4
Average Periods Grahamstown Hermanus Louisvale Madimbo
Summer 2.0 – 3.5 2.5 – 3.5 --------- 3.0 – 3.5
Autumn 3.0 – 3.5 3.0 – 3.5 3.0 2.5 – 3.0
Winter 2.5 – 3.0 2.5 – 3.0 2.5 – 3.0 2.5 – 3.0
Spring ----------- 3.0 – 4.0 ----------- 3.0 – 4.0
Wave activity
slightly greater
at lower solar
activity
• Only large scale waves detected (i.e periods > 1 hr)
• Most wave activity in winter and longer periods in spring

foF2 [MHz]
period [hours]
• Distortion of results due to automatic scaling manual editing of data
needed
• Sampling period limits observations of large scale wave structures
• Propagation characteristics challenging
4
3
2
1
Limitations
Great distances between ionosonde stations (distances between roughly
680 km and 1755 km)
scarcity of observations of same structure (same period, same day) in
multi stations
GRHM 30-Mar-2011
4 6 8 10 12 14 16 18 20
2.5
2
1.5
1
0.5
12
8
4
0
0 2 4 6 8 10 12 14 16 18 20 22 24
time [UT]

TIDs with GPS: SADM-GPS technique
• To first approximation, assume wave structures are represented as plane solitary
travelling wave
where A is the wave amplitude, k x , k y are the x and y projections of the wave vector k, Ω,
and are the angular disturbance frequency and initial disturbance phase respectively
• The azimuthal propagation direction of the phase wave front and TID’s
horizontal phase velocity, v h (t) can be computed using:
Where I’ x (t), I’ y (t) and I’ t (t) are the spatial
and time derivatives, u x (t), u y (t) are the
propagation velocities of the phase front
along the x and y axes (assumed in east and
north directions) in the frame of reference,
and w x (t), w y (t), are the x and y projections
of the sub-ionospheric intersection velocity.
Afraimovich et al, 2003, JASTP, 65, 1245-1262

where A H , A K and A P are the TEC perturbations of 3 GPS receivers respectively, x P ,
y P , and x K and y K are the coordinate distances of the receivers in a Cartesian system

Preliminary results
• KRUG – HRAO-PRET: 26 September 2011

TIDs with HF Doppler
• Propagation of medium scale TIDs:
– Wavelengths less than 1000 km
– Periods between 15 and 1 hour
– Average horizontal speeds of ~ 150 m/s

Propagation Characterisation
• Time delays obtained by cross-correlating a pair of traces:
• Periods obtained from wavelet analysis
• Horizontal wavelengths and velocities calculated from distances between
transmitters and time delays of traces
– Unrealistic velocities and wavelengths results, need more work.
dt/[min] dx/[km] vx/[m/s] dy/[km] vy/[m/s] dd/[km] v/[m/s] T/[min] λ/[km]
Wor-Cpt: -1.5167 -44.95 +493.93 -16.28 +178.88 +47.80 +525.32 +39.89 +1257.38
Wor-Arn: +0.8500 39.54 +775.27 -53.23 -1043.82 +66.31 +1300.23 +41.53 +3240.14
Cpt-Arn: +2.4667 +84.16 +568.68 -36.96 -249.71 +91.92 +621.09 +36.16 +1347.67

Electron density irregularities during
storm conditions
• Magnetic storm is an extreme event of space weather which drive/generate
ionospheric irregularities/disturbances, which in turn might cause signal
scintillation
• Magnetic storms cause significant deviations of electron densities from their
normal behaviour by modifying the thermospheric composition
• The ionospheric response to the storm is mainly positive and negative
referring to the increase and decrease in electron density respectively
• Magnetic storm of interest: 06-12 November 2004

Storm indicators: 6-12 Nov 2004
• Red arrows: Approximate times of sudden storm commencements (SSC)
• SSC: abrupt increase/decrease in the H component

Location of Instruments Used
• GPS/IGS: NKLG, MBAR, MALI, SBOK, SUTH
• Ionosonde: MDBO, GRTN
• magnetometers: BNG, AAE

Equatorial and midlatitude regions
• TEC peaks over NKLG occurred at ~ 12:00 and 18:00 UT for 08 and 10 Nov 2004
respectively indication that driving mechanism could have been oriented in
the westward direction

• Taking into account time delay of the occurrence of
the wavelike structure, propagation velocity was
computed as ~ 407 m/s and 440 m/s for MALI-MBAR
and MBAR-NKLG observation TID
• Observed structure with estimated average max
amplitude of 6 and 7 TECU (7-11 Nov 2004): partly
responsible for shift in TEC enhancement

• Intense joule and particle heating cause by storm lead to wind driven motion of the
atmosphere around the auroral oval
• Strong upwelling transports N2 rich (O2 depleted) air from lower thermosphere to the F-
region
• Neutral winds then redistribute the N2 rich air over the high and part of the midlatitude
which later causes a reduction in electron density

Africa Ionospheric Map (AIM)
• Ionospheric map: essentially a computer program that shows
spatial and temporal representation of ionospheric parameters,
e.g. electron density, etc
• Data sources/input: ionosonde network, South African Bottomside
Ionospheric Model (SABIM), International Reference Ionosphere
(IRI) Model
• Best fit between data and models used to produce the interface
map over Africa

Interface of the map
A
B
C
D
E

Results: foF2 Map

Results: M3000F2 determination

Results: TEC Map

Future Work
• Installation of more
ionosonde over Africa is
needed
• Include GPS data
• Accessibility of real time
data
– Occultation data, for
horizontal spatial
distribution of
ionosphere
Original Ionosonde stations

Thank You