1 Tsegaye Kassa and 2 Pierre Cilliers 1 Associate Professor of Space Physics Bahir Dar University Bahir Dar Ethiopia 2 South African National Space Agency Hermanus South Africa 1518 July ID: 810608
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Slide1
Suppression of ionospheric scintillation during the 2015 St. Patrick’s Day geomagnetic super storm as observed over, Ethiopian GPS network
1Tsegaye Kassa and 2Pierre Cilliers1Associate Professor of Space Physics, Bahir Dar University, Bahir Dar, Ethiopia2 South African National Space Agency, Hermanus, South Africa15-18 July 2019
Ionospheric Scintillation Workshop,
15-18
July 2019, South African National Space Agency Hermanus, Cape Town, South Africa
Slide2Organization
Background
Data and
methods
Results
Conclusions
Slide3Background
Global occurrence characteristics of scintillation (P.
Kintner
et.al 2009).
Slide4Background
Slide5Objectives
Slide6B
ZEyDstindexSolar proxyGeomagnetic storm proxy
vTEC
and ROTI mapping we used GPS networks over Ethiopia
Data
S
4
index
Slide71. The Rate of TEC (
dTEC/dt) calculation 2. The Rate of TEC Index (ROTI) estimation Standard deviation of ROT (on 5 min intervals)
ROTI Computation
=
Amplitude Scintillation Index Computation
where
I
represents the detrended
signal intensity
Slide8Results
Fig. Monthly
vTEC
(top), Annual
vTEC
(middle)
and Map of
vTEC
(bottom)
on 2015.
The radial values refers days whereas the azimuth values are universal time
Slide9Ionospheric scintillation mapping
Fig. Monthly S4 (top), ROTI (middle)
and Map of ROTI (bottom)
on 2015.
The radial values refers days whereas the azimuth values are universal time
Slide10Event description
As we can see from the right-bottom panel of this Fig., the arrival of Shock at the Earth produced a sudden storm commencement (SSC) at 04:45 UT.
The value of
Dst
started decreasing right after the IMF turned south-ward. The storm intensified (
Dst
dropped to
-
80
nT
at ∼10:00 UT) during the passage of the sheath (a region between the shock and the driver of the shock). Later, the storm recovered slightly (i.e.,
Dst
dropped to ∼
-
50
nT
), shortly after the IMF turned northward.
A few hours later, the IMF turned southward again due to the strongly negative
Bz
in the magnetic cloud (MC) and caused the second storm intensification, reaching
Dst
=
-
223
nT
on 17 March.
Fig. Evolution of CME on 15 March 2015 (top) and its average speed (bottom).
Fig. Monthly values of
Dst
(top) and solar and geomagnetic parameters (bottom).
Slide11Results and discussions
Fig.
Dst
(top) ,
vTEC
(middle) and S4 index (bottom)
on
11-21 March 2015.
Fig. Daily
Dst
March
2015.
Dst
, VTEC & S4
11-21 March 2015
Slide12Results and discussions
Fig. S4 (top)
and
ROTI
index (bottom)
on
13-20
March 2015
.
S4 and ROTI
13-20 March 2015
14
15
16
20
19
18
17
13
Slide13Storm-time analysis
Fig.
vTEC
(top) and S
4
index (bottom) on 14-17 March 2015. Fig. Effects of PPEF over Ethiopian and Indian longitudes on 17 March 2015.
Ethiopia
India
Slide14Storm-time analysis
Fig. Daily variations of
vTEC
(top) and ROTI (bottom) on 14-19 March 2015 2015.
The radial values
refer to
geographic latitude whereas the azimuth values are local time
16 Mar 2015
15 Mar 2015
14 Mar 2015
17 Mar 2015
18 Mar 2015
18 Mar 2015
17 Mar 2015
14 Mar 2015
15 Mar 2015
16 Mar 2015
VTEC
VTEC
VTEC
VTEC
VTEC
ROTI
ROTI
ROTI
ROTI
ROTI
Slide15Storm-time analysis
Fig. The
thermospheric
O/N2 ratio obtained from the GUVI/TIMED during 13-20 March 2015.
Slide16Conclusions
Can we use ROTI to detect morphology of scintillation in the absence of SCINDA receivers?
Is there a consistence mechanism to explicitly tell the effect of storm on scintillation other than Aarons (1991)’s approach?
Thank you for your attention!
Slide17Using data from a number of magnetic storms with dates ranging from December 1971 to November 1981 primarily in years of high solar flux, the following categories were found. If the maximum ring current energy as shown by
Dst occurred during the midnight to postmidnight time period, irregularities were generated. If the maximum Dst, the period before recovery set in, occurred in the early afternoon, irregularities were inhibited. If the maximum occurred around sunset or shortly after sunset, then there was no effect on the generation of irregularities that night. Aarons J 1991 The role of the ring current in the generation and inhibition ofequatorial F-layer irregularities during magnetic storms; Radio Sci. 26 1131–1149