Third generation of the Potsdam Magnetic Model of the Earth (POMME)

Abstract

[1] The Potsdam Magnetic Model of the Earth (POMME) is a geomagnetic field model providing an estimate of the Earth's core, crustal, magnetospheric, and induced magnetic fields. The internal field is represented to spherical harmonic (SH) degree 90, while the secular variation and acceleration are given to SH degree 16. Static and time-varying magnetospheric fields are parameterized in Geocentric SolarMagnetospheric (GSM) and Solar-Magnetic (SM) coordinates and include Disturbance Storm-Time (Dst index) and Interplanetary Magnetic Field (IMF-By) dependent contributions. The model was estimated from five years of CHAMP satellite magnetic data. All measurements were corrected for ocean tidal induction and night-side ionospheric F-region currents. The model is validated using an independent model from a combined data set of Ørsted and SAC-C satellite measurements. For the core field to SH degree 13, the root mean square (RMS) vector difference between the two models at the center of the model period is smaller than 4 nT at the Earth's surface. The RMS uncertainty increases to about 100 nT for the predicted field in 2010, as inferred from the difference between the two models.

Theory and Modeling of Planetary Dynamos

“…This definition is somewhat arbitrary (Wicht et al 2009) but nevertheless demonstrates that the Earth-like regime occupies only a small part of the parameter space. Figure 5 compares time averaged magnetic energy spectra of cases in regimes D, E, and M for E = 3×10 −4 with the spectrum of a geomagnetic field model for the year 2000 (Maus et al 2006). The spectra show the magnetic energy carried by the spherical harmonic contributions of degree l at the outer boundary (cmb).…”

“…Transparent colored bands in the with of the standard deviation illustrate the time variability. The thick black line shows the spectrum for the geomagnetic field model POMME for the year 2000 (Maus et al 2006) changes from a dipole dominated regime D to a multipolar regime M where the dipole component has lost its special character (Kutzner and Christensen 2002;Christensen and Aubert 2006;Olson and Christensen 2006;Wicht et al 2009). While the dipole never reverses in regime D it continuously switches polarity in regime M. Earth like reversing behavior (regime E), where the dipole still dominates in a time mean sense and polarity transitions, are relatively rare events can be found at the transition.…”

The magnetic field changing over the southern African continent: a unique behaviour

“…Separating these contributions is not an easy task (e.g. Mandea and Purucker, 2005;Maus and Lühr, 2005;Maus et al, 2006;Olsen et al, 2006;Thomson and Lesur, 2007). However, using a spherical harmonic expansion of the geomagnetic field potential, a separation between internal and external contributions to the field can be obtained.…”

An algorithm for deriving core magnetic field models from the Swarm data set

“…Depending on the interest of the modelers and the time period in focus, several approaches with different model designs are available, e.g. CM4 (Sabaka et al, 2004), POMME (Maus et al, 2006), CHAOS (Olsen et al, 2010) and GRIMM (Lesur et al, 2008(Lesur et al, , 2010 series.…”