CM5, a pre-Swarm comprehensive geomagnetic field model derived from over 12 yr of CHAMP, Ørsted, SAC-C and observatory data

Sabaka, Terence J.; Olsen, Nils; Tyler, Robert H.; Kuvshinov, Alexey

doi:10.1093/gji/ggu493

Cited by 146 publications

(179 citation statements)

References 47 publications

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“…6a). Furthermore, this offset is in the range of recently reported offsets amounting to −9.1 nT needed for the RCE to match annual averages of CHAMP Z M values (Lühr et al 2017) and −10 nT needed to match the −q 0 1 SH coefficient of the CM5 geomagnetic model (Sabaka et al 2015). The significance of both these comparisons is partially restricted by the fact that AMC includes secondary induced signals in addition to the direct external field and did not undergo any subjective quiet-time selection procedure.…”

Section: Amc Absolute Levelmentioning

confidence: 69%

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An annual proxy for the geomagnetic signal of magnetospheric currents on Earth based on observatory data from 1900–2010

Pick

Korte

2017

Geophysical Journal International

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S U M M A R YWe introduce the Annual Magnetospheric Currents index as long-term proxy for the geomagnetic signal of magnetospheric currents on Earth valid within the time span 1900-2010. Similar to the widely used disturbance storm time and 'Ring Current' indices, it is based on geomagnetic observatory data, but provides a realistic absolute level and uncertainty estimates. Crucial aspects to this end are the revision of observatory crustal biases as well as the implementation of a Bayesian inversion accounting for uncertainties in the main field estimate, both required for the index derivation. The observatory choice is based on a minimization of index variance during a reference period spanning 1960-2010. The new index is capable of correcting observatory time series from large-scale external signals in a user-friendly manner. At present the index is only available as annual mean values. An extension to hourly values for the same time span is in progress.

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Section: Amc Absolute Levelmentioning

confidence: 69%

“…Further options apart from these are the CHAOS (Finlay et al 2016, version six) and CM (Sabaka et al 2015, version five) model series. We reject both in order to preserve independence of the RC index, which is used in the latest versions of both these series.…”

Section: Large-scale External Field Modelmentioning

confidence: 99%

An annual proxy for the geomagnetic signal of magnetospheric currents on Earth based on observatory data from 1900–2010

Pick

Korte

2017

Geophysical Journal International

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“…Their technique is suitable to include satellite data as well as ground measurements. Sabaka et al (2002) used a "comprehensive approach", which simultaneously determines the magnetic potentials for magnetospheric, ionospheric, and underground sources by the use of satellite and ground data. The ionospheric source represents the Sq-EEJ current system.…”

Section: Spherical Harmonic Analysismentioning

confidence: 99%

“…The ionospheric source represents the Sq-EEJ current system. Figure 25 shows the ionospheric current system derived from the latest version of their model, CM5 (Sabaka et al 2015). Note how the currents are constrained by the magnetic equator.…”

Section: Spherical Harmonic Analysismentioning

confidence: 99%

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

2016

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A record of the geomagnetic field on the ground sometimes shows smooth daily variations on the order of a few tens of nano teslas. These daily variations, commonly known as Sq, are caused by electric currents of several μA/m 2 flowing on the sunlit side of the Eregion ionosphere at about 90-150 km heights. We review advances in our understanding of the geomagnetic daily variation and its source ionospheric currents during the past 75 years. Observations and existing theories are first outlined as background knowledge for the nonspecialist. Data analysis methods, such as spherical harmonic analysis, are then described in detail. Various aspects of the geomagnetic daily variation are discussed and interpreted using these results. Finally, remaining issues are highlighted to provide possible directions for future work.

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“…• The Comprehensive Inversion (CM) family, of which the latest published version is CM5 [34]. The Swarm Level 2 Data Product: Comprehensive Inversion (CI) [38] has been produced using a similar method but using only Swarm data.…”

Section: Robustness Of Jet Accelerationmentioning

confidence: 99%

An accelerating high-latitude jet in Earth’s core

2016

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Observations of the change in Earth's magnetic field, the secular variation, provide information on the motion of liquid metal within the core that is responsible for its generation. The very latest high-resolution observations from ESA's Swarm satellite mission show intense field change at high-latitude localised in a distinctive circular daisy-chain configuration centred on the north geographic pole. Here we explain this feature with a localised, non-axisymmetric, westwards jet of 420 km width on the tangent cylinder, the cylinder of fluid within the core that is aligned with the rotation axis and tangent to the solid inner core.We find that the jet has increased in magnitude by a factor of three over the period 2000-2016 to about 40 km/yr, and is now much stronger than typical large-scale flows inferred for the core. The current accelerating phase may be a part of a longer term fluctuation of the jet causing both eastwards and westwards movement of magnetic features over historical

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CM5, a pre-Swarm comprehensive geomagnetic field model derived from over 12 yr of CHAMP, Ørsted, SAC-C and observatory data

Cited by 146 publications

References 47 publications

An annual proxy for the geomagnetic signal of magnetospheric currents on Earth based on observatory data from 1900–2010

An annual proxy for the geomagnetic signal of magnetospheric currents on Earth based on observatory data from 1900–2010

Sq and EEJ—A Review on the Daily Variation of the Geomagnetic Field Caused by Ionospheric Dynamo Currents

An accelerating high-latitude jet in Earth’s core

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