Transcript Slant TEC data ingestion in the Modified NeQuick

Slant TEC data ingestion in the
Modified NeQuick
ionosphere electron density model
B. Nava, S.M. Radicella, R. Leitinger and P.Coïsson
The Abdus Salam ICTP, Trieste, Italy
IGAM, Graz, Austria
XXVIII General Assembly of International Union of Radio Science
New Delhi, India
October 23-29, 2005
Outline
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Introduction
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Slant TEC data ingestion
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Electron density reconstruction technique (concepts)
The Modified NeQuick performance
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NeQuick model and Modified NeQuick model description
Evaluation criteria
Data used
Data analysis
Conclusions
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Introduction (NeQuick)
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NeQuick is an ionospheric electron concentration model able to
give the electron density distribution on both the bottomside and
topside of the ionosphere.
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The model formulation includes 6 semi-Epstein layers with
modeled thickness parameters and is based on anchor points
defined by foE, foF1, foF2 and M(3000)F2 values.
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These values can be modeled (e.g. ITU-R coefficients for foF2,
M(3000)F2) or experimentally derived.
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The NeQuick topside formulation is based on an empirical k
parameter, that controls the topside profile shape and depends
on the month of the year.
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NeQuick inputs are: position, time and solar flux; the output is the
electron concentration at the given location and time.
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Introduction (modified NeQuick)
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The Modified NeQuick topside formulation is based on an
empirical k’ parameter that does not depend on the month of the
year and therefore it is a simplification of the previous one
(ICTP).
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foF2 and hmF2 (instead of foF2 and M(3000)F2) are modeled
using a new mapping procedure, based on simplified ITU-R
maps “CCsim” (IGAM University of Graz).
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M(3000)F2 is recovered “inverting” the Dudeney formula for
hmF2 and it is used only as internal parameter.
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Slant TEC data ingestion
NeQuick + ITU-R [or “CCsim”] coefficients + F10.7
Climate representation of the ionosphere
NeQuick + ITU-R [or “CCsim”] coefficients + effective ionization level
Weather specification of the ionosphere
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Slant TEC data ingestion
At a given epoch
m sTECexp (several stations & satellites)
Minimize each
mismodeling
Scattered Az
j
Interpolate to get regularly spaced grid
Use NeQuick to reconstruct the 3D
electron density of the ionosphere
Reconstruct TEC along any
given ray-path
Reconstruct any foF2 value
(foF2 map)
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Model performance evaluation
Criteria:
comparison between experimental and reconstructed
sTEC (self consistency of the reconstruction method)
comparison between experimental and reconstructed
foF2 (independent crosscheck with ionosonde data)
Data used:
Super-truth sTEC data from 25 ground stations &
foF2 data from 6 ionosondes at 15 min. time interval
for the days 27 March, 5 April, 6 June 2000
(undisturbed days in high solar activity)
Data analysis:
cumulative distributions of the absolute values of the
differences between experimental and reconstructed
sTEC data and foF2 data
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Stations & ionosondes locations
Super-truth stations
Ionosondes
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Modip isolines
Results: sTEC & foF2, day 000327
NeQuick
NeQuick
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Modified NeQuick
Modified NeQuick
Results: NmF2, day 000327
NeQuick
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Modified NeQuick
Results: sTEC & foF2, day 000405
NeQuick
NeQuick
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Modified NeQuick
Modified NeQuick
Results: NmF2, day 000405
NeQuick
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Modified NeQuick
Results: sTEC & foF2, day 000607
NeQuick
NeQuick
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Modified NeQuick
Modified NeQuick
Results: NmF2, day 000607
NeQuick
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Modified NeQuick
Conclusions
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NeQuick model has been modified. The impact of the changes
has been tested using an electron density reconstruction
technique previously developed by the authors. This technique,
based on slant TEC data ingestion, has been applied to
NeQuick and Modified NeQuick models.
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The results obtained show that the Modified NeQuick model
allows a better reconstruction of the ionosphere in terms of
TEC, if compared with NeQuick model. Not substantial changes
are observed in terms of foF2.
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Since NeQuick has been developed to be used in single
frequency positioning applications, where TEC is the most
important parameter to be modeled, the Modified NeQuick
model can be considered an improvement with respect to
Nequick.
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Acknowledgments
The authors are grateful to the WAAS community from whom
they received the “Supertruth” data used for the present study
and to the Center for Atmospheric Research of the University of
Massachusetts at Lowell, for providing access to the digital
ionogram data base (DIDBase).
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Thank you for your attention
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