Modeling the Jovian magnetic field and its secular variation using all available magnetic field observations

We present new models of Jupiter's internal magnetic field and secular variation from all available direct measurements from three decades of spacecraft observation. A regularized minimum norm approach allows the creation of smooth, numerically stable models displaying a high degree of structure. External field from the magnetodisk is modeled iteratively for each orbit. Jupiter's inner magnetosphere is highly stable with time, with no evidence for variation with solar activity. We compare two spherical harmonic models, one assuming a field constant in time and a second allowing for linear time variation. Including secular variation improves data fit with fewer additional parameters than increasing field complexity. Our favored solution indicates a ∼0.012% yr−1 increase in Jupiter's dipole magnetic moment from 1973 to 2003; this value is roughly one quarter of that for Earth. Inaccuracies in determination of the planetary reference frame cannot explain all the observed secular variation. Should more structure be allowed in the solutions, we find the northern hemispherical configuration resembles recent models based on satellite auroral footprint locations, and there is also evidence of a possible patch of reversed polar flux seen at the expected depth of the dynamo region, resembling that found at Earth and with implications for the Jovian interior. Finally, using our preferred model, we infer flow dynamics at the top of Jupiter's dynamo source. Though highly speculative, the results produce several gyres with some symmetry about the equator, similar to those seen at Earth's core-mantle boundary, suggesting motion on cylinders aligned with the rotation axis

Developing an understanding of coherent approaches between primary and secondary teachers:a case study within the design and technology curriculum in Scotland

This study is based around Education Scotland’s ambition to create a coherent learning framework for pupils aged 3–18, with particular focus on the technologies curricular area, and more specifically the subject of design and technology (D&T). The study investigates the views, definitions, and approaches adopted by primary and secondary educators applied to the D&T curricular area. Furthermore, the research explores curricular understanding and pedagogical approaches in addition to individual teacher’s understanding of technology education. A mixed method research approach was utilised and applied within one local authority region in Scotland. Data was collected from primary teachers and secondary design and technology teachers using online questionnaires and interviews. Findings reveal that there is a varied approach to teaching design and technology across primary and secondary schools with educators recognising different definitions and pedagogical approaches in the subject. This indicates that pupils transitioning from primary to secondary learning will have to cope with these differing teaching approaches when studying design and technology. However, participants agree on the importance of the design element and application of the subject to real world scenarios. It is recommended that school communities find opportunities to collaborate further with the aim of creating a more continuous, coherent learning journey for young people in the design and technology curriculum area. These findings provide a basis for future professional discussion and critical reflection for practitioners in both primary and secondary sectors, and for leaders and administrators across Scotland, the UK and around the world

Robust estimators reveal changing geomagnetic field behaviour through the Cenozoic

The Fisher distribution is central to palaeomagnetism but presents several problems when used to characterize geomagnetic field directions as observed in sequences of volcanic rocks. First, it introduces a shallowing effect when used to define the mean of any group of directional unit vectors. This is problematic because it can suggest the presence of persistent non-axial dipole components when none are present. More importantly, it fails to capture the observed ‘long tail’ in distributions of both directions and associated virtual geomagnetic poles in terms of angular distance from a central direction. To achieve a good fit to data, it therefore requires the introduction of a second distribution (and therefore the estimation of additional parameters) or the arbitrary removal of data. Here we present a new distribution to describe palaeomagnetic directions and demonstrate that it overcomes both of these problems, generating robust indicators of both the central direction (or pole position) and the spread of palaeomagnetic data as defined by unit vectors. Starting from the assumption that poles (or directions) have an expected colatitude, rather than a mean location, we derive the spherical exponential distribution. We demonstrate that this new distribution provides a good fit to palaeomagnetic data sets from seven large igneous provinces between 15 and 65 Ma and also those produced by numerical dynamo models. We also use it to derive a new shape parameter which may be used as a diagnostic tool for testing goodness of fit of models to data and use this to argue for a shift in geomagnetic behaviour between 5 and 15 Ma. Furthermore, we point out that this new statistic can be used to determine the most appropriate distribution to be used when constructing confidence limits for poles

Low-diffusivity lattice-gas models of mixtures

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.Includes bibliographical references (leaves 46-48).by Richard T. Holme.M.S

Can the Comprehensive Model (CM4) predict global features of sudden commencements?

We investigate the capability of the Comprehensive model CM4 to predict features of geomagnetic sudden commencements (SCs) focusing on observations from five ground-based observatories along the African chain. A list of 153 SC events has been selected within the period 2011–2015 to compare between modelled and observed SCs at different seasons and local times. The study reflects the degree of consistency between the CM4 model and the real physics occurring at each ground station. It also compares the characteristics of observed and modelled SC field to show how well the model performs for predicting the SC field variation. Results of feeding the CM4 model by the SYMH index data shows that the CM4 model provides a reasonable fit of the observed SC field at stations located closer to the average latitude of Dst index stations. Positive SC field variations during the day and night times for both CM4 modelled and observed fields are expected to be a signature of the magnetopause and field aligned currents rather than the axial ring current. The dawn-dusk asymmetry of the SC modelled field, which resembles the observed field at stations located poleward of the equatorial region, reveals a significant contribution from the partial ring current. At the magnetic equator, the equatorial ionospheric electrojet current plays a significant role in enhancing the observed SC field during daytime hours, which is not parameterized in the CM4 model. The latitudinal profile of the modelled field exhibits its maximum variation at the magnetic equator, decreasing towards the poles. This latitudinal profile resembles the observed field but is weaker. The modelled field at the latitudes of the Dst index stations has the same local time features of the observed field, but its strength is much smaller than the observed field and also it does not exceed its corresponding SYMH variations. In addition, the modelled SC field has a weak smooth variation with respect to local time, unlike the broad scattering of the observed field. Despite the substantial correlation between the modelled SC field and its associated SYMH field variations, the model always under-estimates the SYMH variations even at the magnetic equatorial station. Also, the CM4 model has no information about the SC seasonal variation, even at stations located within the same latitudes of the Dst index stations. These limitations should be considered when using the CM4 model to describe the external magnetospheric field

The contribution of Teacher education to universities:a case study for international teacher educators

This paper reports on the initial stage of a research project which aims to develop deeper understanding of the contribution teacher education, as a sub-discipline within Education, makes to Higher Education in England. The study is located in the intersection between the domains of teacher education and higher education scholarship, which in England represents a contested and ambiguous professional space. Tensions between competing accountability measures, pulling away from university-based to exclusively school-based teacher education, are exacerbated by proposed policy changes arising from the government's recent market review. Findings drawn from analysis of qualitative data from a national survey are discussed in the context of Elizabeth Povinelli's critique of late liberalism and previous scholarship on the nature of teacher educators’ work. Evidence from the study demonstrates numerous benefits to higher education of hosting teacher education departments, including contributions to standard metrics, regional development and knowledge exchange within a strategic social justice agenda. However, teacher educators themselves may find articulating these benefits difficult, because of marginalisation from the dominant ways of achieving and accounting for excellence in the modern university. These findings offer a cautionary tale to international colleagues whose governments may be embarking on equivalent paths of teacher education reform.<br/