The Swarm Initial Field Model for the 2014 geomagnetic field

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

show abstract

“…• The Swarm Initial Field Model (SIFM) using data only from Swarm at the single epoch of 2014.5 [37]; we used the SV to degree 11.…”

Section: Robustness Of Jet Accelerationmentioning

confidence: 99%

An accelerating high-latitude jet in Earth’s core

2016

View full text Add to dashboard Cite

show abstract

“…The Dst index (or its refined version, the RC index) and its time derivative are used to search magnetically quiet periods and to characterize time variations in the external field with its induction effect (Maus and Lühr 2005;Olsen et al 2005b). 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).…”

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%

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

et al. 2016

View full text Add to dashboard Cite

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

show abstract

“…We used freely available and widely used models, which are considered to be the most precise at the moment: CHAOS-6 (Finlay et al, 2016), SIFM (Olsen et al, 2015), and EMM2015 (Magnetic Crustal Field Model, 2017). All of them are constructed using the high-precision new-generation satellite observations.…”

Section: Absolute Baseline and Definitive Data Analysismentioning

confidence: 99%

Saint Petersburg magnetic observatory: from Voeikovo subdivision to INTERMAGNET certification

Сидоров

Soloviev

Krasnoperov

et al. 2017

Geosci. Instrum. Method. Data Syst.

View full text Add to dashboard Cite

Abstract. Since June 2012 the Saint Petersburg magnetic observatory is being developed and maintained by two institutions of the Russian Academy of Sciences (RAS) – the Geophysical Center of RAS (GC RAS) and the Saint Petersburg branch of the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of RAS (IZMIRAN SPb). On 29 April 2016 the application of the Saint Petersburg observatory (IAGA code SPG) for introduction into the INTERMAGNET network was accepted after approval by the experts of the first definitive dataset over 2015, produced by the GC RAS, and on 9 June 2016 the SPG observatory was officially certified. One of the oldest series of magnetic observations, originating in 1834, was resumed in the 21st century, meeting the highest quality standards and all modern technical requirements. In this paper a brief historical and scientific background of the SPG observatory foundation and development is given, the stages of its renovation and upgrade in the 21st century are described, and information on its current state is provided. The first results of the observatory functioning are discussed and geomagnetic variations registered at the SPG observatory are assessed and compared with geomagnetic data from the INTERMAGNET observatories located in the same region.

show abstract

The Swarm Initial Field Model for the 2014 geomagnetic field

Cited by 86 publications

References 24 publications

An accelerating high-latitude jet in Earth’s core

An accelerating high-latitude jet in Earth’s core

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

Saint Petersburg magnetic observatory: from Voeikovo subdivision to INTERMAGNET certification

Contact Info

Product

Resources

About