Continuous geomagnetic field models for the past 7 millennia: 1. A new global data compilation

Abstract

[1] A global data set of archeomagnetic and paleomagnetic data covering the past 7000 years has been compiled. It consists of 16,085 results of inclination, 13,080 of declination, and 3188 of intensity for the time span 5000 BC to 1950 AD. Declination and inclination data come partly from existing databases and partly from original literature. A new global compilation of intensity data for the millennial scale is included. Data and dating uncertainties are discussed as we attempted to obtain an internally coherent data set. The global distribution of the data is very inhomogeneous in both time and space. All the data are compared to predictions from the previous 3000 year global model, CALS3K.1. This collection of data will be useful for global secular variation studies and geomagnetic field modeling, although southern hemisphere data are still underrepresented. In particular, we will use it in a further study to update and extend the existing global model, CALS3K.1. The huge increase in data compared to the previous compilation will result in significant changes from current models. As we might have missed some suitable data, we encourage the reader to notify us about any data that have not been included yet and might fit in, as improving our global millennial scale models remains our aim for the future. The data files described in this paper are available from the EarthRef Digital Archive (ERDA) at http://earthref.org/cgi-bin/ erda.cgi?n=331.

Variational data assimilation for the initial-value dynamo problem

“…Variations of the magnetic field have been recorded either by direct human observation for the last few hundred years [6] or through the magnetization of rocks and artifacts over the last few thousand years [7]. These observations have sensitivity to the magnetic field originating in the core of the Earth.…”

“…The Earth's dynamo system continuously creates a magnetic field, which is recorded in rocks, lavas, and sediments and also observed by observatories and satellites. These observations are represented by two models: gufm1 (for the past 400 years) [6] and cals7k (for past 7000 years) [7]. For Earth, the electrical conductivity of the mantle is several orders of magnitude weaker than that of the core; hence Earth's mantle is assumed as an insulator and thus, the surface observed data represented by gufm1 and cals7k can be downward projected onto the core mantle boundary (CMB).…”

Arqueomagnetismo e datação arqueomagnética: princípios e métodos

“…Atualmente, as curvas de referência estão disponíveis para os últimos 2.000 a 3.000 anos em várias regiões do planeta, incluindo a América do Norte (Stenberg 1989;Labelle e Eighmy 1997;Yu et al 2000), América Central (Morales et al 2001;Bowles et al 2002;Soler-Arechalde et al 2006), Leste da Ásia (Cong e Wei 1989), Leste e Oeste da Europa (Bucur 1994;Kovacheva 1997;Kovacheva et al 1998;Chauvin et al 2000;Genevey e Gallet 2002;Genevey et al 2003;Kovacheva et al 2004;Schnepp e Lanos 2005;Gómez-Paccard et al 2006). Existem também compilações globais, como aquelas de Valet (2003); e Korte et al (2005). No entanto, a área em que uma dada curva de referência pode ser aplicada à datação arqueomagnética é da ordem de 200.000 km 2 , visto que há sutis diferenças de variação do campo magnético da Terra para locais que são um pouco distantes entre si.…”

The HISTMAG database: combining historical, archaeomagnetic and volcanic data

“…Korte et al 2005;Donadini et al 2006;Genevey et al 2008;Korhonen et al 2008). The most up to date compilation is provided by the GEOMAGIA50.v3 database (Brown et al 2015a,b).…”