Global Navigation Satellite systems: omatics New oportunities for …swe.ssa.esa.int/TECEES/spweather/workshops/esww/proc/... · 2020. 8. 16. · New oportunities for scientific advances

1First European Space Weather Week, ESTEC/ESA, Nordwijk, The Netherlands, Nov.29-Dec.3, 2004 Hernández-Pajares, Juan and Sanz

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Global Navigation Satellite systems: New oportunities for scientific advances

in Space Weather

M. Hernández-Pajares, J.M.Juan, J.SanzResearch Group of Astronomy and Geomatics

Technical University of Catalonia (gAGE/UPC)E08034-Barcelona, Spain

Contact e-mail: [email protected]


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Global Navigation Satellite systems: New oportunities for scientific

advances in Space Weather

Outline1. Introduction2. GNSS and Space Weather3. Examples of GNSS improved techniques4. Examples of Space Weather Physical

phenomena detected with GNSS data5. Conclusions


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IntroductionThe Space Weather can be defined as “Conditions on the sun and in the solar wind, magnetosphere, ionosphere, and thermosphere that can influence the performance and reliability of space-borne and ground-based technological systems as well as endanger human life and health “.

GPS: A set of about 30 MEO transmitting at two L-band frequencies during the last 10 years codes for navigation purposes. This system is at the same time “victim” and “player” in the Space Weather arena, specially affected by the ionospheric conditions.


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Oct

ober

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th

TECGIM(UPC)TECGIM(UPC)

HPE 95%14-15 UT

HPE 95%21-22 UT

Example of Space Weather effect on GPS: single-frequency navigation based on broadcasted iono corrections (EGNOS Test Bed) during the

October 30 2003 superstorm

This talk will deal with some contributions of GPS and GNSS in general to increase the scientific understanding of Space WeatherThe effects on GNSS navigation will be covered in another talk. Anyway you can find here an example.


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The UV (and X) Solar radiation ionizes the region above 50-100 km: Ionosphere (to 1000 km) and Protonosphere/Plasmasphere (above 1000 km).

The GPS signals are affected by the free electrons: carrier phase advance and code/pseudorange delays, proportional (1st order, 99.99% of the total delay) to the ray-path integrated electron density (STEC) and to the inverse squared freq.

Global PositioningSystem (GPS): near 30 MEOs transmitting in twofrequencies at L-band.

GPS and the Ionosphere


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International GPS Service, IGS

IGS directly manages more than about 350 permanent GPS stations, observing some 4-10 satellites at 30 sec rate: more than 250,000 STEC worldwide observations/hour, but there is lack of

stations at the South and over the Seas.

A total number of more than 1000 permanent GPS receivers are available taken into account other networks.


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GPS+ IGS: Global Iono. scanner “Ionoscope”

GPS+ IGSSat. Rec.

Worldwide scanner of the Ionosphere that can be used to monitor the Space Weather signatures on VTEC, such as Storm Enhanced Densities (SED), X-Flares, Scintillation, Large Scale TIDs.

Low orbiting GPS receivers (CHAMP, SAC-C…) are also available adding 3D estimation capability (electron density) with great vertical resolution.


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Typical Vertical and Horizontal electron content distribution(estimated from LEO and ground based GPS data)

Global vertical TEC map computedfrom ~100 GPS dual frequencyreceivers (units: 0.1 TECU)

Electrondensity (Ne) profilecomputedfrom LEO GPS data (units: Te-/m**3)

•Typical horizontal distribution: Maximum values at bothsides of the geomagnetic equator (equatorial anomalies), correlated with the Sun position as well. •Typical vertical distribution: Maximum density height at 200-400 km (or higher during the night) with maximum electrondensities of 1011- 1012 e-/m3 (lower in the night).


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GNSS & Space Weather

DATA

PHYSICAL PHENOMENA TECHNIQUES

APPLICATIONS

Ground GPSLEO/occultation GPSHigh frequencymeasurements (50-100 Hz)Galileo & Modernized GPS

TomographicmappingIGS IonosphereImproved Abel transformHigh precisiondSTEC estimationCombination ofgeodetic andIonosphericprocessing…

Solar X-FlaresStorm EnhancedDensities (SEDs)Large Scale TravellingIonosphericDisturbances (LSTIDs)Scintillation…

We are going to concentrate our talk in Scientific contributions of GNSS data and techniques to Space Weather.In another presentation next weekhere in ESTEC at NAVITEC, we willtreat WARTK for GPS & Galileo systems

Satellite Based Augmentation Systems(EGNOS, WAAS, MSAS…)Wide Area Sub-decimeter error-levelnavigation (WARTK)...


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Example 1 of GNSS improved techniques:

Vertical to slantionospheric mapping


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Relaxing the single-layer model

A significant reduction of the single-layer model mismodeling (typically used, Lanyi et al. 1988) can be obtained by relaxing it: for instance by introducing additional layers and solving for the ionospheric (geometry-free) carrier phase bias and electron density unknowns corresponding to each illuminated voxel.


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VTEC error: 1 layer vs. 2 layers

The VTEC missmodelling due tothe fixed height layermodel (blue andgreen), can rangefrom several TECU atmid latitude to more than 10 TECU in theEquator (Hernández-Pajares et al. 1999).

The VTEC missmodellingis reduced stillusing coarse3D models(red)


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Example 2 of GNSS improved techniques: Cooperative

computation of IGS Ionospheric Global TEC maps


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IGS Organization


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VTEC global maps: cooperative effort in IGS

IGSGPS data

IGSIonosphere

Analysis Centers

IGSIonosphere Validation Centers

IGSIonosphere

CombinationCenter

IGSIonosphere

The IGS Ionosphere Working group started its activities in June 1998 with the main goal of a routinely producing IGS Global TEC maps(IGTEC). This is being done now with a latency of 11 days (final product –official-) and with a latency of less than 24 hours (rapid product –still unofficial-).

The IGS ionosphere product is a result of the combination of different Analysis Centers Global TEC maps (which feasibility was shown by Mannucci et al. 1995) by using weights computed from GPS data by Validation Centers, in order to get a more accurate product.


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Example of IGS Final TEC map: 2003-347-00UT

Units: 0.1 TECUs

Four Analysis Centers (CODE, ESA, JPL and UPC) and 3 Validation Centers (JPL, ESA and UPC) have been providing maps (at 2 hours x 5 deg. x 2.5 deg in UT x Lon. x Lat.), weights and external (dual-frequency altimetry-derived) TEC data.

From such maps and weights the corresponding combination center (firstly ESA, and secondly UPC since Dec.2002) is producing the IGS TEC maps in standard IONEX format.


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Rapid / Final IGS vs. JASON TEC

The 4 Analysis Centers started to deliver the rapid maps regularly.

The generation of rapid IGS VTEC maps (latencies of less than 24 hours) started on Dec.2003. RMS’s: from 5 TECU (Dec’03) to 3 TECU (Aug’04).

During the last 6 months the Rapid IGS VTEC maps tends to similar levels of accuracy compared to Final IGS maps. This is coincident with the regular delivering of the 4 analysis centers.

IGS Final Ionosphere ionex files at ftp://cddisa.gsfc.nasa.gov/gps/products/ionex/

IGS rapid ionospheric map (ionex files and plots from ftp://gage152.upc.es/rapid_iono_igs/ )

You can find more details at the Position Paper (IGS Tech. Meeting, Bern, March 2004)

ftp://cddisa.gsfc.nasa.gov/gps/products/ionex/


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Example 3 of GNSS improved techniques:

Ionospheric tomography


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Estimating electron density in a 3D Voxelmodel (general / global)

Different kind of data are mixed: occultationand ground GPS data.

This is an example corresponding to the combination ofboth complementary type of GPS data (ground-based fromIGS network and space-based from GPS/MET LEO) in theframework of a 3D voxel tomographic model solved by means of a Kalman filter (Oct.18, 1995 geomagnetic storm, Hernández-Pajares et al. 1998).


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High resolutiontomography: Benefits ofseparability

With the TEC (computed from ground GPS data) modelling the horizontal variation, the electron density at tangent point A (green) is estimated from the GPS LEO occultation data better (red) that assuming spherical symmetry (blue). More details at Hernández-Pajares et al. 2000.


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75km-125km

125km-175km

175km-250km

250km-650km

250km-2000km

REFERENCE VALUES Ground GPS+Ionosondes Ground GPS

The mean electron densities obtained with 7 GPS receivers in theground and with 1 ionosonde are in good agreement. This is not thecase using just the ground GPS data (typical correlated solution).More experiments and details at García-Fernández et al. 2003.

One ionosondeat EBRE, and 7 ground GPS receivers, estimating electron densities from STEC generated by IRI.

Electron density combining ground GPS and Ionosonde data

in a 3D voxel model


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Example 4 of GNSS improved techniques: High precision VTEC variation for

permanent receivers


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High precision STEC variation estimation in permanent ground-based GPS stations

Thanks to the sidereal-day repeatability of the GPS transmitter-to-receiver geometry, a straightforward, simple and precise computation of the STEC variation can be done (Hernández-Pajares et al. 1997).


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Example 1 of Space WeatherPhysical phenomena detected

with GNSS data: X-Flares


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Detection of large Solar X-flares in terms of Global and sudden STEC increase in the daylit hemisp. (28Oct03)

1120UT

1040UT

1103UT1112UT

Sudden TEC increase of 10+ TECU were experienced in the daylit hemisphereGPS receivers due to the arrival of a Solar X-flare X-rays/UV extra radiation(event during 28 Oct. 2003, 11UT approx, preceding superstorms).


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Recent example of GNNS-detection of Solar X-flares: high (X) intensity (10Nov04)

USUD, Japan

0205UT aprox.

ALIC, Australia

0205UT aprox.

Several authors (Zhang et al. 2002, Zhang & Xiao 2003, Liu et al. 2004) have demonstrated the feasibility of using GNSS for detecting Solar X-flares, thanks in particular to recent GNSS techniques (such as the high precision STEC variation estimation described above) detecting the sudden extra-ionization (UV and X) happened in the daylit hemisphere, correlated with the cosinus of the solar-zenith angle.


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Recent example of GNNS-detection of Solar X-flares: lower intensity (M, 08Nov04)

Though an extensive study of the GNSS sensitivity to the X-flare intensity is still pending, it can be seen that a non so-energetic X-flare (M-level) seems to be detected as well.

GODE, USA, 1040LT approx

1546UT aprox.


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Example 2 of Space WeatherPhysical phenomena detected

with GNSS data: Storm-Enhanced Density (SED)


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SED during the Oct.2003 Superstorm (30Oct03) 1840UT 1920UT 2000UT

It has been possible to image with an unprecedented detailed evolution of the SEDs (Foster et al. 2002), thanks to the high temporal and spatial resolution of the GPS permanent networks, in particular over North America, with more than 400 permanent receivers (CORS network in addition to IGS network). Several authors points to the SED distribution origin as superfountain effect (Tsurutani et al. 2004). But Kelley et al. (2004) have pointed out the need of an additional poleward penetrating electric field as a way to empty the nightside and dumping it into the dayside, building up the TEC by advection close to the terminator.


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High STEC variation and Ne uplift

High STEC variation and Ne uplift (obtained fromCHAMP LEO GPS receiver) during the StormEnhancement of Density (superstorm 30 Oct. 2003)


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Recent SED example: Superstorm 8-10Nov04 (quickglance, rapid IGS maps, latencies of ~17 hours)


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Day 09Nov04, ~03-05UT: Night regions(NA, Europe) practicallyempty of free electrons

Day 10Nov04, ~18UT: A typical SED structure appears overNorthAmerica (not so intense such as in other superstorms).

Some details SED Superstorm 8-10Nov04 (from 5-minutes rapid IGS maps, with 1000+ rec.)


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Example 3 of Space WeatherPhysical phenomena detectedwith GNSS data: Large Scale

Travelling IonosphericDisturbances (LSTIDs)


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Large Scale TIDs (22/23 Sept 1999)

(Figure extracted from Tsuwaga et al 2003)

Thanks to the existence of very dense GPS networks (such as GEONET with 1000+ receivers at Japan) it has been posible to quantify the highcorrelation of the Large Scale TIDs (period of ~1 hour, λ ~2000 km) withthe geomagnetic storms: 75% of occurrence probability of one LSTID in 3 hours for Kp=9, in front of 1% for Kp=4 (Tsugawa et al. 2004).


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Recent example of Large Scale TIDs (09Nov04)


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Example 4 of Space Weather Physical phenomena detected with GNSS data: Scintillation

at mid latitudes


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Scintillation: Very rapid VTEC variations

The scintillations are veryuncommon at midlatitudes, associated thento geomagnetic activity. Can produce the lost oflock of GPS satellites.


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Recent example of mid.-low. Lat. scintillation during geomagnetic Storms (10Nov04)

Thanks to the deploiment of scintillation receivers, being able ofmeasuring the observables of all the GPS satellites in view 50-100 times per second, it has been recently demonstrated the existence ofscintillation (in particular in amplitude) at mid-latitudes duringgeomagnetic storms (Ledvina et al. 2002).


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Strong scintillation associated with SED (20Nov03)

Figure courtesy of Dr. Anthea Coster and Dr. Susan Skone

Thanks to the deploiment of several scintillation receivers in Canada, ithas been posible to detect high scintillation events (pink circles) coinciding with SEDs (see figure) as far as with auroral substorms(Skone et al. 2004).


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•We have shown several contributions of Global Navigation Satellite System (GPS) data and techniques to the Space Weather physical phenomena study.•In particular some examples of GNSS techniques have been shown: improvement of GPS ionospheric modelling, tomography, accurate dSTECestimation and the cooperative IGS global VTEC maps.•Such advances in GNSS ionospheric techniques, among others, are contributing positively to the study and modelling of Storm Enhanced Densities (SEDs), Solar X-flares, Large Scale TIDs and Scintillation.•We could envisaged in the future: (1) Thousands of grounds GNSS receivers and tens of LEO GNSS receivers will be hopefully available providing continuous global 3D ionospheric sounding, many of them in real-time.(2) Global Assimilation Ionospheric Models, combining any kind of ionosphericdata and physics at global scale, can play a fundamental role, not only in nowcasting but in forescasting as well (topic of research of several groups).(3) Galileo constellation could be operational at ~2009. Thus an overall GNSS constellation with ~60 satellites can provide typically instantaneous STEC for each GNSS receiver at 10-25 different directions.


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ReferencesTHANK YOU!Foster J.C., P. J. Erickson, A. J. Coster, J. Goldstein, F. J. Rich, Ionospheric signatures of plasmaspheric tails, Geophysical Research Letters, Vol. 29, No. 13, 1623, 10.1029/2002GL015067, 2002

García-Fernández M., Hernández-Pajares, M., J.M. Juan, J. Sanz, P. Coisson, B. Nava, S.M. Radicella, Combining Ionosonde with ground GPS data forElectron Density Estimation, Journal of Atmospheric & Solar-Terrestrial Physics, Vol. 65 Pag. 683 691, 2003.

Hernández-Pajares M., J.M. Juan and J. Sanz, High resolution TEC monitoring method using permanent ground GPS receivers, Geophysical ResearchLetters, Vol. 24, N. 13 Pag. 1643 – 1646, 1997.

Hernández-Pajares M., J.M. Juan and J. Sanz, Global observation of the ionospheric electronic response to solar events using ground and LEOGPS data, Journal of Geophysical Research-Space Physics, Vol. 103, N. A9 Pag. 20789 – 20796, 1998.

Hernández-Pajares M., J.M. Juan and J. Sanz, New approaches in global ionospheric determination using ground GPS data, Journal of Atmospheric andSolar Terrestrial Physics. Vol 61, 1237-1247, 1999.

Hernández-Pajares M., J.M. Juan and J. Sanz, Improving the Abel inversion by adding ground data LEO to radio occultations in the ionospheric sounding, Geophysical Research Letters, Vol. 27 No.16 Pag. 2743 – 2746, 2000.

Kelley M.C., M.N. Vlasov, J.C. Foster, A.J. Coster, A quantitative explanation for the phenomenon known as storm-enhancement density, GeophysicalResearch Letters, Vol. 31, L19809, 2004.

Ledvina B.M., J.J. Makela and P.M. Kintner, First observations of intense GPS L1 amplitude scintillations at midlatitude, Geophysical Research Letters, Vol. 29, No. 14, 1659, 2002

Liu J.Y., C.H.Lin, H.F.Tsai, Y.A.Liou, Ionospheric solar flare effects monitored by the ground-based GPS receivers: Theory and observation, Journal ofGeophysical Research, Vol. 109, A01307, 2004.

Skone S., A.Coster, J.Foster, W.Rideout, Correlating Scintillation and Storm Enhanced Density in the mid- to high- latitudes, Beacon Satellite Symposium, Trieste, Italy, October 2004.

Tsurutani B., A. Mannucci, B.Iijima, M. Ali Abdu, J.H.A. Sobral, W. Gonzalez, F. Guarnieri, T. Tsuda, A. Saito, K. Yumoto, B. Fejer, T. Fuller-Rowell, J. Kozyra, J.C. Foster, A. Coster, V.M. Vasyliunas, Global dayside ionospheric uplift and enhancement associated with interplanetary electric fields, Journal ofGeophysical Research, Vol.109, A08302, 2004.

Zhang D.H, Z.Xiao, K.Igarashi, G.Y.Ma, GPS-derived ionospheric total electron content response to a solar flare that occurred on 14 July 2000, Radio Science, Vol.37, No.5, 1086, 2002.

Zhang D.H., Z.Xiao, Study of the ionospheric total electron content response to the great flare on 15 April 2001 using the International GPS Service networkfor the whole sunlit hemisphere, Journal of Geophysical Research, Vol.108, No.A8, 1330, 2003.

Global Navigation Satellite systems: New oportunities for scientific advances in Space WeatherOutlineTypical Vertical and Horizontal electron content distribution (estimated from LEO and ground based GPS data)GNSS & Space WeatherExample 1 of GNSS improved techniques: Vertical to slant ionospheric mappingRelaxing the single-layer modelVTEC error: 1 layer vs. 2 layersExample 2 of GNSS improved techniques: Cooperative computation of IGS Ionospheric Global TEC mapsExample of IGS Final TEC map: 2003-347-00UTRapid / Final IGS vs. JASON TECExample 3 of GNSS improved techniques: Ionospheric tomographyEstimating electron density in a 3D Voxel model (general / global)High resolution tomography: Benefits of separabilityElectron density combining ground GPS and Ionosonde data in a 3D voxel modelExample 4 of GNSS improved techniques: High precision VTEC variation for permanent receiversExample 1 of Space Weather Physical phenomena detected with GNSS data: X-FlaresDetection of large Solar X-flares in terms of Global and sudden STEC increase in the daylit hemisp. (28Oct03)Example 2 of Space Weather Physical phenomena detected with GNSS data: Storm-Enhanced Density (SED)SED during the Oct.2003 Superstorm (30Oct03)Day 302, 2003, 2240UTExample 3 of Space Weather Physical phenomena detected with GNSS data: Large Scale Travelling Ionospheric Disturbances (LSTIDsExample 4 of Space Weather Physical phenomena detected with GNSS data: Scintillation at mid latitudesScintillation: Very rapid VTEC variationsReferences

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Global Navigation Satellite systems: omatics New oportunities for …swe.ssa.esa.int/TECEES/spweather/workshops/esww/proc/... · 2020. 8. 16. · New oportunities for scientific advances