CHAOS-a model of the Earth's magnetic field derived from CHAMP, Ørsted, and SAC-C magnetic satellite data

Olsen, Nils; Lühr, H.; Sabaka, Terence J.; Mandéa, Mioara; Rother, M.; Tøffner-Clausen, Lars; Choi, Sungchan

doi:10.1111/j.1365-246x.2006.02959.x

Cited by 243 publications

(222 citation statements)

References 31 publications

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“…Recent examples include the Pomme magnetic model (Maus et al, 2006), the CHAMP, Ørsted and SAC-C based CHAOS model (Olsen et al, 2006) and the GFZ Reference Internal Magnetic Model, GRIMM (Lesur et al, 2008). Such more sophisticated main field models are widely used in geomagnetism for studies of the dynamics of the earth's core (e.g.…”

Section: Introductionmentioning

confidence: 99%

NOAA/NGDC candidate models for the 11th generation International Geomagnetic Reference Field and the concurrent release of the 6th generation Pomme magnetic model

Maus

Manoj

Rauberg³

et al. 2010

Earth Planet Sp

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The International Geomagnetic Reference Field (IGRF) is updated every five years based on candidate model submissions by research institutions worldwide. In the call for the 11th generation of IGRF, candidates were requested for the definitive main field in 2005, the predicted main field in 2010, and the predicted secular variation from 2010 to 2015. The NOAA/NGDC candidate models for IGRF-11 were produced from parent models parameterized in the same way as the 6th generation of our Pomme magnetic model. All models were based on CHAMP satellite measurements, while Ørsted satellite measurements were used for model validation. The internal field in Pomme-6 is described by a 2nd degree Taylor time series of spherical harmonic expansion coefficients of a scalar magnetic potential. Magnetic fields of ionospheric origin are avoided by careful data selection. Instead of co-estimating magnetospheric fields, we subtract a magnetospheric field model estimated previously from a more extensive data set covering all local times. From comparison with Ørsted measurements and general considerations of magnetic field predictability, we attribute a root mean square (RMS) uncertainty of 1.3 nT to our candidate model for the main field in 2005, 2.5 nT to the predicted main field in 2010 and 26 nT/a to the predicted secular variation from 2010 to 2015.

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Section: Introductionmentioning

confidence: 99%

NOAA/NGDC candidate models for the 11th generation International Geomagnetic Reference Field and the concurrent release of the 6th generation Pomme magnetic model

Maus

Manoj

Rauberg³

et al. 2010

Earth Planet Sp

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“…Replacing magnetic londitudes with Magnetic Local Time (M LT ) helps in distinguishing such features in ionospheric currents that depend on the location of sub-solar point with respect to the magnetic pole (Baker and Wing 1989). QD-latitudes ± 60 or 55 are often used as the demarcation between polar and non-polar areas which are handled differently in data processing (Olsen et al 2006;Lesur et al 2010;Olsen et al 2015).…”

Section: Introductionmentioning

confidence: 99%

“…The Solar-Magnetic (SM) coordinate system has appeared to be the most suitable for ring current and magnetopause current parametrization while for magne-totail currents the Geocentric-Solar-Magnetospheric (GSM) coordinate frame is a more appropriate way for data modeling (Maus and Lühr 2005;Olsen et al 2006) (for the introduction of SM and GSM coordinates, see Kivelson and Russell (1995)). The Quasi-Dipolar (QD) coordinate system introduced by Richmond (1995) is a good framework to represent ionospheric currents and FACs which still at Low Earth Orbit (LEO) altitudes are organized according to the ambient magnetic field whose topology can be described accurately enough with IGRF models (Sabaka et al 2015).…”

Section: Introductionmentioning

confidence: 99%

“…Magnetically quiet times are associated with the conditions of |Dst| < 30 nT and |dDst/dt| or |dRC/dt| being less than 2 or 5 nT /h (Olsen et al 2014;Maus et al 2010;Sabaka et al 2015). CHAOS, CM-5 and SIFM characterize weak global activity with the condition Kp ≤ 2 o (Olsen et al 2006;Sabaka et al 2015;Olsen et al 2015). POMME-6 uses the am index instead of Kp with the limits am < 12 for mid latitudes and am < 27 for high latitudes (Maus et al 2010).…”

Section: Introductionmentioning

confidence: 99%

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On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

et al. 2016

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We present a review on geomagnetic indices describing global geomagnetic storm activity (Kp, am, Dst and dDst/dt) and on indices designed to characterize high latitude currents and substorms (PC and AE-indices and their variants). The focus in our discussion is in main field modelling, where indices are primarily used in data selection criteria for weak magnetic activity. The publicly available extensive data bases of index values are used to derive joint conditional Probability Distribution Functions (PDFs) for different pairs of indices in order to investigate their mutual consistency in describing quiet conditions. This exercise reveals that Dst and its time derivative yield a similar picture as Kp on quiet conditions as determined with the conditions typically used in internal field modelling. Magnetic quiescense at high latitudes is typically searched with the help of Merging Electric Field (MEF) as derived from solar wind observations. We use in our PDF analysis the PC-index as a proxy for MEF and estimate the magnetic activity level at auroral latitudes with the AL-index. With these boundary conditions we conclude that the quiet time conditions that are typically used in main field modelling (P C < 0.8, Kp < 2 and |Dst| < 30 nT ) correspond to weak auroral electrojet activity quite well: Standard size substorms are unlikely to happen, but other type of activations

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“…To avoid the problem of the evident model heterogeneity we finally resorted to two couples of more homogeneous models, in terms of model construction and data selection. In particular, we analysed the differences between POMME 3.0 and POMME 6.0 (Maus et al, 2006; and between CHAOS-1 and CHAOS-2 from 2006 to 2010 (Olsen et al, 2006;2009), where the older versions of each couple of models acts as a predictive model and the most recent one as the definitive one; POMME models and CHAOS-1 model include their MF, SV and SA terms, so we considered, together with MF and SV terms, all SA terms (case a -empty squares in Fig.4) or without them (case b -empty circles in Fig.4) for POMME analyses, and all SA terms for CHAOS analysis (case c-full squares in Fig.4). Both analyses of POMME models (cases a and b) were extended up to N=10, but no significant change appears with lower and higher degrees (verified for N=8 and 16); the analysis of CHAOS models was limited to N=14.…”

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confidence: 99%

Ergodicity of the recent geomagnetic field

Santis

Qamili

Cianchini

2011

Physics of the Earth and Planetary Interiors

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Please cite this article as: De Santis, A., Qamili, E., Cianchini, G., Ergodicity of the recent geomagnetic field, Physics of the Earth and Planetary Interiors (2011), doi: 10.1016/j.pepi.2011 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. AbstractThe geomagnetic field is a fundamental property of our planet: its study would allow us to understand those processes of Earth's interior, which act in its outer core and produce the main field. Knowledge of whether the field is ergodic, i.e., whether time averages correspond to phase space averages, is an important question since, if this were true, it would point out a strong spatiotemporal coupling among the components of the dynamical system behind the present geomagnetic field generation. Another consequence would be that many computations, usually undertaken with many difficulties in the phase space, can be made in the conventional time domain. We analyse the temporal behaviour of the deviation between predictive and definitive geomagnetic global models for successive intervals from 1965 to 2010, finding a similar exponential growth with time. Also going back in time (at around 1600 and 1900 by using the GUFM1 model) confirms the same findings. This result corroborates previous chaotic analyses made in a reconstructed phase space from geomagnetic observatory time series, confirming the chaotic character of the recent geomagnetic field with no reliable prediction after around 6 years from definitive values, and disclosing the potentiality of estimating important entropic quantities of the field by time averages.Although more tests will be necessary, some of our analyses confirm the efforts to improve the representation of the geomagnetic field with more detailed secular variation and acceleration.

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CHAOS-a model of the Earth's magnetic field derived from CHAMP, Ørsted, and SAC-C magnetic satellite data

Cited by 243 publications

References 31 publications

NOAA/NGDC candidate models for the 11th generation International Geomagnetic Reference Field and the concurrent release of the 6th generation Pomme magnetic model

NOAA/NGDC candidate models for the 11th generation International Geomagnetic Reference Field and the concurrent release of the 6th generation Pomme magnetic model

On the Usage of Geomagnetic Indices for Data Selection in Internal Field Modelling

Ergodicity of the recent geomagnetic field

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