Norbert Jakowski and M. Mainul Hoquebss2019.uwm.edu.pl/sites/default/files/uploads/2... ·...

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


Motivation for developing application supporting indices


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


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


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.


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.


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


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


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, N. and M. M. Hoque (2019) doi: 10.1029/2018SW002119

Comparison of indices SIDX and GIX with maps of ΔTEC and TEC


• 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.


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.


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.


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


• 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).


/ 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.


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