Summary of part of L2 session
• Tools e.g. for data selection
• Products, including models
– Mostly based on magnetic data
– Both dedicated and comprehensive models
• Validation
• Enhancing return from mission
Quiet time definition
• Magnetosphere-ionosphere system
reconfigures in 10-20 minutes
• Use SUPERMAG vector data to quantify
external field
• SMDL characterises field, value in nT
• Quiet time – about 50% data overlap with
definition used by Nils Olsen for data selection
Testing SUPERMAG definition
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Compare with previous CHAOS model
Use SMDL to select quiet time data
Same amount of data at high latitudes
Same amount at mid/low latitudes, and ± 20%
Fit as good as or better than for CHAOS (e.g. <
2nT rms misfit to Bϕ)
• Larger residuals near poles though overall
misfit the same
IBI, TEC and FAC
• FAC and ionospheric radial currents: good agreement
between satellites, and between original and mapped
data
• Also undertook in-orbit comparison
• Comparison between TEC from GPS and electron
density measured by Langmuir probe
• Obtain VTEC from slant TEC – reasonable agreement
with electron density
• Ionospheric bubble indices – investigated seasonal
variations
• Some ionospheric bubbles don’t have a magnetic
signature – use electron density instead
FAC – Swarm A, B, and C
High-Latitude (01 May 2014 – 31 May 2015)
Northern Hemisphere
Swarm A
Swarm B
Swarm C
Southern Hemisphere
TEC: Vertical TEC & Electron Density
VTEC
Swarm A
Swarm B
Swarm C
 Statistical Distribution of VTEC and Ne: good agreement
Ne
IBI: Seasonal Variations (18-04 MLT)
Swarm A
Event detection threshold = 0.15 nT
Swarm B
Swarm C
December Solstice
Equinox
June Solstice
Ionospheric irregularity index based on plasma density
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IBI and Ne (constant and variable) indices
 Both: use high-pass filter
 IBI Index: constant threshold on magnetic field
 Ne Index: threshold on density
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Ne Index
 Constant threshold: not yet sufficient for quantitative bubble description
 Variable threshold
o Better coincidence with plasma density maximum: enhanced symmetry about the equator
o sensitive to data quality
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New approach is necessary
 direct detection of depletions and enhancements (work in progress)
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Preliminary results of the new approach
Dedicated core field model
• Based on GRIMM methodology
• No observatory data
• Data selection went well beyond using data
flags
• SV agrees with other models to degree 10
• Euler angles (estimated from quaternions)
show LT dependencies
Dedicated lithospheric field model
• Several models investigated for removing core
field – none perfect
• Some along-track filtering, resulting in slight loss
of power visible in power spectrum comparisons
• Developed new orbit filtering based on similar
track recognition
• Included gradient data in inversion
• Problems near poles – FACs?
• Good resolution to degree ~75
PRESENTATION AND VALIDATION OF THE DIFI L2 PRODUCT
• First DIFI model released to ESA on July 24, 2015
• Second DIFI model calculated from satellite data until July 2015 and with new Q matrix
based on more recent 1-D conductivity profile (Puethe et al.)
• Change of Q matrix has a (very) small effect on the model
• Overall performance of the DIFI chain is close to the requirement
• DIFI and CI models have noticeable differences (but CI soon to be updated)
DIFI, Spring (Apr 1)
Equivalent current function of the ionospheric primary currents
Ocean tides
• Comparison with numerical model
• Used residual night-time data, CHAMP and
Swarm
• Modelled to degree and order 40
• Tidal periods imposed
• Investigated M2, S2, K1 and N2
• Some non-physical features (signal on land)
• Some amplitudes too big
Conductivity
Comprehensive modelling
• Improved lithospheric field in latest version
• Described how model was obtained, although
not clear why it is an improvement
• Scalar and vector sums and differences used
(restrictions on use of vector s/d)
• Definition of M2 as good from 18 months of
Swarm as 10 years of CHAMP
• Ionospheric field over-regularised
Time-variable gravity field from Swarm
GPSR data
Aleš Bezděk
Josef Sebera
Jaroslav Klokočník
Astronomical Institute,
Czech Academy of Sciences,
Czech Republic
Swarm 5th Data Quality Workshop,
Institut de Physique du Globe de Paris,
France, 7 – 10 September 2015
GPS monthly solutions: GRACE A/B & Swarm
KBR monthlies: CSR and GFZ
GPS monthlies: GRACE A/B (2004-2013)
GPS monthlies: Swarm (12/2013-3/2015)
Time series of GRACE A/B GPS-based
monthly solutions is successfully
continued by Swarm
• both seasonal and secular variations
• Note: this is mm precision in all data,
transformations & background models
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Swarm GPS orbits are accurate
enough to track the mm-level timevariable gravity signal
Other groups (ITSG, AIUB) obtained
similar results by using different
inversion methods
Validation
• Cross-validation between comprehensive and
dedicated models
• Compare with auxiliary models (e.g. IGRF)
• Compare with observatory data
BGS Validation Summary
• The purpose is primarily to:
– ensure no grievous errors
– give confidence to ESA and users products have
been independently verified
BOU
HUA
• Validation procedure is active and effective
• Products deemed valid and suitable for release
AUX_OBS_2_ residuals; Dedicated MIO models
Enhancing return
• Add-ons and improvements to existing
products
• Improvements to processing and modelling
chains
• New products
• Lots of possible examples cited by Nils