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TRANSCRIPT
Capability study of GNSS based ionospheric indices
Norbert Jakowski and M. Mainul Hoque German Aerospace Center (DLR), Institute for Solar-Terrestrial Physics, Neustrelitz, Germany
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 1
Outline
• Introduction
• Former work on indices at DLR
• GNSS based index approaches addressing customer needs
o Gradient Ionosphere indeX (GIX)
o Sudden Ionosphere Disturbance indeX (SIDX)
o Application example
• Summary
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 2
Motivation for developing application supporting indices
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 3
GNSS signal amplitude
5 April 2006
GNSSsignal loss
HMI: Hazardous Misleading Information
HMITime UT/ hrs.
ST
EC
/ T
EC
U
Aviation
• Degradation of accuracy, integrity, availability and continuity of signals
• HF Communication disturbed or interrupted
Needs:
• Operational detection and estimation of the ionospheric perturbation degree.
• Ionospheric “Threat-Model”X17 solar flare on October 28, 2003
GNSSsignal loss
Earlier index approaches at DLR
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 4
N. Jakowski et al. (2012) Introducing a Disturbance IonosphereIndex (DIX), Radio Science, 47, RS0L14
Disturbance Ionosphere Index (DIX)
Input data from a predefined area,
Combining calibrated or uncalibrated TEC
at different piercing points in the area,
Rate of vertical TEC
• Average temporal index
• Difference spatial index
Generation of actual maps of DIX
• Development of
approaches
that provide optimal
information on the current
state of the ionosphere
for specific users.
• Commercial customers
are not primarily
interested to understand
physical processes, they
need indices addressing
their concrete problems:
spatial gradients and
rapid signal (phase and
amplitude) fluctuations.
V., Wilken et al. (2018) J. Space Weather Space
Clim. 8 A19 DOI: 10.1051/swsc/2018008
Disturbance Ionosphere Index
Spatial Gradient (DIXSG)
Definition of dimensionless scale
N. Jakowski et al. (2006) Adv. Space Res., 38, 2596–2600
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 5
12
N: number of piercing points PPi and PPj
Central point CPij
∆𝑠𝑖𝑗: distance between piercing points
𝛻𝑇𝐸𝐶𝑥𝑖𝑗 : gradient East direction
𝛻𝑇𝐸𝐶𝑦𝑖𝑗 : gradient in North direction
𝜵𝑻𝑬𝑪𝒙𝒊𝒋 : total gradient between PPi and PPj
Gradient Ionosphere indeX
𝐺𝐼𝑋 = 𝛻𝑇𝐸𝐶 =1
𝑁𝐷
𝑖=1
𝑁𝐷
𝛻𝑇𝐸𝐶𝑖𝑗
𝐺𝐼𝑋𝑆 = σ =2𝛻𝑇𝐸𝐶2 − 𝛻𝑇𝐸𝐶 2
• Data base: calibrated slant TEC
data at N piercing points PPij.
• VTEC gradient computation
between all ionospheric piercing
points at any time possible,
ND=N(N-1)/2 PP pairs available.
• Computation of average gradients
and standard deviation
Spatial perturbation degree by the Gradient Ionosphere indeX GIX
Jakowski, N. and M. M. Hoque (2019), Estimation of spatial gradients and
temporal variations of the total electron content using ground based GNSS
measurements, Space Weather, doi: 10.1029/2018SW002119
GIX at quiet ionospheric conditions
• Upper part:
GIX, GIXS and GIXP computed over Europe
(30-70° N; 20°W-50° E) for quiet days
20–25 May 2015 at different spatial scales
Left panel: 30-250km
Right panel: 50-500 km
• Lower part:
Comparison of GIXx,y, and GIXP95± for
West- East components (left panel)
South-North (right panel)
The number of dipoles used for computation
NC ≤ ND is plotted at the bottom of the top
graphics with the scale shown to the right-
hand side.
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 6
GIX at quiet ionospheric conditions
• Zonal gradients from May 20 - 25, 2015 for different dipole lengths Δs showing positive values
(≈ 3-4 mTECU/km) before noon increasing towards lower latitudes.
• Negative values (≈ 3-4 mTECU/km) appear in the afternoon as expected.
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 7
TID structure
Temporal perturbation degree by Sudden Ionospheric Disturbance indeX - SIDX
• SIDX – Basic approach:
Average rate of TEC of all PP
in a selected area
• SIDX response to solar flares may differ
from X ray classification due to spectral
dependence of ionization
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 8
𝑺𝑰𝑫𝑿 =𝝏𝑻𝑬𝑪
𝝏𝒕
𝑺𝑰𝑫𝑿𝑺 =𝟐
(𝝏𝑻𝑬𝑪
𝝏𝒕
𝟐
−𝝏𝑻𝑬𝑪
𝝏𝒕
𝟐
)
𝜕𝑇𝐸𝐶
𝜕𝑡=∆𝑆𝑇𝐸𝐶
𝑀 ∆𝑡−𝜕𝑇𝐸𝐶
𝜕𝑢𝑣
𝜕𝑇𝐸𝐶
𝜕𝑡≈1
𝑁
𝑖=1
𝑁∆𝑆𝑇𝐸𝐶
𝑀 ∆𝑡𝑖
Jakowski, N. and M. M. Hoque (2019), Space Weather,
doi: 10.1029/2018SW002119
Solar Flare events in September 2017
J. Berdermann et al. (2018). Ionospheric response to the X9.3 Flare on 6
September 2017 and its implication for navigation services over Europe. Space
Weather, 16. https://doi.org/10.1029/2018SW001933
X-ray
EUVGNSS user need EUV
related flare information
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 9
GIX at perturbed ionospheric conditions (Halloween storm)
• GIX, GIXS and GIXP95 analysis of the
Halloween storm on 28 October -1 November
2003 at ranges 30-250 km and 50-500 km (top
panels). Components of GIX and GIXP95± over
Europe (30-70° N; 20° W-50° E) in comparison
with the geomagnetic Dst index for 50-500 km
range (lower panels).
• GIXS is correlated with the Dst index but shows
individual characteristics.
• This clearly indicates that geomagnetic indices
like Kp and Dst cannot describe ionospheric
features in detail.
• DIX and DIXS should have the potential to
indicate crucial situations for precise GNSS
positioning.
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 10
Jakowski, N. and M. M. Hoque (2019) doi: 10.1029/2018SW002119
Comparison of indices SIDX and GIX with maps of ΔTEC and TEC
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 11
• SIDX corresponds
with ionization
patches
• GIXP95 corresponds
clearly with an
ionization front
characterized by
strong TEC gradients
• European maps of GIX, GIXS and GIXP95
(averaged over 1 hour between 17 and 18UT on
March 17, 2015, dipole length range from 50-
1000 km) indicate the location of enhanced
gradients.
• GNSS users over Europe could exclude those
GNSS links which go through perturbed areas.
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 12
GIX at St. Patrick storm on 17 March 2015
Applicability of GIX and SIDX indices
• Horizontal gradients of
ionospheric ionization may cause
problems in GNSS applications
for aviation (e.g. EGNOS)
• GIX is able to characterize
crucial situation concerning
horizontal gradients (left panel).
• A GIX based service could
provide apprpopriate warning for
EGNOS or other aviation related
applications.
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 13
Definition of user specific
thresholds possible
• Rapid temporal changes of the
ionospheric ionization may cause
problems at GNSS receiver level
if receivers cannot follow rapid
changes of the ionospheric
ionization (right panel)
Aalborg
57°N;10°E
Summary & conclusions
• Ionospheric research and numerous GNSS applications indicate the need to
characterize the ionospheric perturbation degree specifically
• Two new approaches for estimating rapid temporal variations and spatial gradients of
the Total Electron Content (TEC) in near real time are discussed.
• It has been shown that the approaches may serve as objective ionospheric indices for
scaling horizontal TEC gradients and detecting rapid solar flare effects for GNSS
application in positioning and navigation
• Further work is needed to address concrete needs of customers and fix appropriate
approaches and thresholds.
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 14
Ionosphere from space
Thank you!
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, Polandwww.DLR.de • t
Contact:
Dr. Norbert Jakowski
Kalkhorstweg 53
D-17235 Neustrelitz
Germany
Email: [email protected]
Web: http://impc.dlr.de
Comparison of indices SIDX and GIX with maps of ΔTEC and TEC
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 16
• SIDX corresponds
with ionization
patches
• GIXP95 corresponds
clearly with an
ionization fronts
characterized by
strong TEC gradients
UT / hour
28-29 October 2003
Simulation of a Gradient Ionosphere Index (GIX) option
• South-North horizontal gradient of electron density introduced in 3D electron densitymodel of DLR: Neustrelitz Electron Density Model (NEDM) (top-left + middel)
• Gradient components South-North and Itotal gradientI (mid-left)
• West-East and Itotal gradientI (bottom-left)
• 2 Sigma values + and - dashed lines (mid- and bottom-left)
• Location and orientation of the station pair provides information on the location of thestrongest gradients in the map (left panel)
• The computed gradients are able to localize and track the maximum gradient in nearreal time if sufficient IPPs are available (top right).
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 17
/ a.u.
Receiving system: electric antenna, Perseus receiver (10 -100
kHz), Internet connection
Installation at mid-latitude sites
in Germany, Poland, USA,Taiwan
GIFDS Installation – experimental setup
D. Wenzel, N. Jakowski, J. Berdermann, Chr. Mayer, C. Valladares, B. Heber, "Global Ionospheric Flare Detection System (GIFDS)", : Journal of Atmospheric and Solar-Terrestrial Physics (2016), pp. 233-242 DOI information: 10.1016/j.jastp.2015.12.011.
> Jakowski & Hoque • GNSS based ionospheric indices - BSS 2019, August 19-23, 2019, Olsztyn, PolandDLR.de • Chart 18