Mesoscale ionospheric tomography over Finland

Juha-Pekka Luntama

Finnish Meteorological Institute

Cathryn Mitchell, Paul Spencer

University of Bath

4th European Space Weather Week, 5 – 9 November, 2007

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Outline1) Introduction

2) MIDAS algorithm and Finnish GNSS network

3) Global and mesoscale retrievals

4) Validation of the results

5) Summary and next steps

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Introduction

• Currently many services are providing global TEC maps in NRT (IGS, SWACI, JPL, …) based on observations from globally distributed GNSS stations (e.g. IGS, EUREF, …)

• Number of IGS and EUREF GNSS stations is low at auroral region

=> resolution of the global maps is limited at the area where the ionosphere is very dynamic

• Dense GNSS networks available in Scandinavia – already used for NWP in the EUMETNET E-GVAP framework

• Our objective is to retrieve high resolution TEC and electron density maps based on these observations

• Test data collected in December 2006

• This work is done in collaboration between University of Bath and FMI

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Multi-Instrument Data Analysis System (MIDAS)• MIDAS is an advanced algorithm

developed by University of Bath for imaging the Earth's ionosphere using data from various ground and space-based instrumentation. 

• Line integral observations of the total electron content (TEC) obtained from a network of ground-based and space-based GPS receivers may be assimilated into the algorithm along with point estimates of the local electron density. 

• The resulting reconstructions provide a highly accurate three-dimensional image of the Earth's ionosphere and its evolution in time. 

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GPS network in Finland operated by Geotrim Ltd

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GPS ray path intersections within the grid

Level height = 300 km

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It was a dark and stormy night…

IMAGE Magnetogram on 14 - 15 Dec 2006

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IGS global TEC maps on 14 - 15 Dec 2006

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Resolution enhancement with regional

observationsRegionalIGS

15 December 2006, 02:00

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3D electron density distributions

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High resolution TEC maps 14 – 15 Dec, 2006

Question: Do these maps represent the real ionosphere?

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Validation opportunity:

Ionospheric Tomography Chain observations

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Intercomparison on 15 Dec 2006 at 02:45

Ionospheric TomographyChain projection plane

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Summary• These are the first results from a new ionospheric tomography testing

in Finland

• The results indicate that mesoscale ionospheric tomography can provide electron density distributions with very high horizontal and temporal resolution

• Current results are based on using only ground based GPS observations => vertical resolution and accuracy of the height information is limited

• Real time data streaming from the GNSS network will be started before the end of the year => development of NRT user service feasible

• Some potential application areas:

– ionospheric monitoring, storm warning, and correction service for GNSS applications

– GNSS ionospheric error and scintillation forecasting research

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Next steps• Improve vertical resolution:

– Use also GLONASS observations (routinely available from the Geotrim network)

– Ingest spaceborne RO soundings

– Combine with other types of observations

=> data assimilation

• Validation of the high resolution tomography maps is a challenge

=> processing of more test cases

=> a rigorous error analysis

=> analysis of the impacts on independent GNSS receivers (IGS, EUREF)

=> careful validation with independent observations (ionospheric tomography chain, ionosonde, EISCAT, …)