title: Current singularities at Quasi-separatrix layers and three-dimensional magnetic nulls

authors: Craig, Ian J.D.

subjects: Science & Technology

abstract: The open problem of how singular current structures form in line-tied, three-dimensional magnetic fields is addressed. A Lagrangian magneto-frictional relaxation method is employed to model the field evolution toward the final near-singular state. Our starting point is an exact force-free solution of the governing magnetohydrodynamic equations that is sufficiently general to allow for topological features like magnetic nulls to be inside or outside the computational domain, depending on a simple set of parameters. Quasi-separatrix layers (QSLs) are present in these structures and, together with the magnetic nulls, they significantly influence the accumulation of current. It is shown that perturbations affecting the lateral boundaries of the configuration lead not only to collapse around the magnetic null but also to significant QSL currents. Our results show that once a magnetic null is present, the developing currents are always attracted to that specific location and show a much stronger scaling with resolution than the currents that form along the QSL. In particular, the null-point scalings can be consistent with models of "fast" reconnection. The QSL currents also appear to be unbounded but give rise to weaker singularities, independent of the perturbation amplitude.

text: Current singularities at Quasi-separatrix layers and three-dimensional magnetic nulls The open problem of how singular current structures form in line-tied, three-dimensional magnetic fields is addressed. A Lagrangian magneto-frictional relaxation method is employed to model the field evolution toward the final near-singular state. Our starting point is an exact force-free solution of the governing magnetohydrodynamic equations that is sufficiently general to allow for topological features like magnetic nulls to be inside or outside the computational domain, depending on a simple set of parameters. Quasi-separatrix layers (QSLs) are present in these structures and, together with the magnetic nulls, they significantly influence the accumulation of current. It is shown that perturbations affecting the lateral boundaries of the configuration lead not only to collapse around the magnetic null but also to significant QSL currents. Our results show that once a magnetic null is present, the developing currents are always attracted to that specific location and show a much stronger scaling with resolution than the currents that form along the QSL. In particular, the null-point scalings can be consistent with models of "fast" reconnection. The QSL currents also appear to be unbounded but give rise to weaker singularities, independent of the perturbation amplitude.

year: 2014-11-10

title: Evaluating soil and landscape models to predict liquefaction susceptibility in the Hinuera Formation, Hamilton Basin

authors: McKay, Aleesha

subjects: liquefaction

abstract: Cone Penetration Tests (CPT) derived from the Hamilton section of the Waikato Expressway were analysed within CLiqTM software. The derived Liquefaction Potential Index (LPI) from each CPT was then combined with LIDAR, pedological and geological maps for statistical analysis. A soil model that incorporates the conditions of modern soil development with these derived LPI values was developed as a preliminary assessment tool for liquefaction potential within Hamilton Basin soils. The model shows that liquefaction is more likely to occur on interfluvial areas where there is little topographical relief. Pedological soils with high organic component are also a likely indicator of high liquefaction susceptibility.

text: Evaluating soil and landscape models to predict liquefaction susceptibility in the Hinuera Formation, Hamilton Basin Cone Penetration Tests (CPT) derived from the Hamilton section of the Waikato Expressway were analysed within CLiqTM software. The derived Liquefaction Potential Index (LPI) from each CPT was then combined with LIDAR, pedological and geological maps for statistical analysis. A soil model that incorporates the conditions of modern soil development with these derived LPI values was developed as a preliminary assessment tool for liquefaction potential within Hamilton Basin soils. The model shows that liquefaction is more likely to occur on interfluvial areas where there is little topographical relief. Pedological soils with high organic component are also a likely indicator of high liquefaction susceptibility.

year: 2017

title: Planning for the protection and enhancement of marine environments' wellbeing

authors: Barnsdall, Aaron

subjects: marine

abstract: The wellbeing of marine environments has a direct relationship with the types of whenua (land, placenta) use and management practices that go from the mountains to the sea. In Aotearoa, activities that are carried out in this land-marine interface, including those related to Nature-based Solutions (NbSs), are regulated by national, regional, and district policies (e.g., New Zealand Coastal Policy Statement, regional plans, and district plans). However, due to its novel character, not all current policies account for the realisation of NbSs nor are NbSs’ potential for addressing the wellbeing of our marine environments well understood.

This dissertation focuses on Tauranga Moana (the seas of Tauranga) as the chosen locality for the case study area, to:

i) investigate how the Ngapeke 7 Trust’s community participants in the Ngāti Pūkenga area of Tauranga Moana understand and value NbSs for addressing the wellbeing of their marine systems; and,
ii) review current planning policies and mechanisms to identify barriers, enablers, and gaps that support or hinder the implementation of NbSs in Tauranga Moana, observing through a Kaupapa Māori lens.

Findings emphasize that integrating mātauranga Māori and Māori Ecological Knowledge (MEK) with scientific knowledge offers a holistic approach to environmental management, enhancing decision-making, education, and policy. Key Māori values, including whakapapa, mauri, and kaitiakitanga, are central to this approach.

The research identifies gaps in policies regarding NbS realization and a need for greater understanding of NbS potential and Māori perspectives. Implications include the necessity of integrating MEK into environmental practices and policies, and the value of NbSs for effective and equitable environmental outcomes. Limitations include sample size and scope, which focused on the Ngapeke 7 block. This research contributes valuable insights for environmental planning and management by centring mātauranga Māori and values in NbS implementation for marine health.

text: Planning for the protection and enhancement of marine environments' wellbeing The wellbeing of marine environments has a direct relationship with the types of whenua (land, placenta) use and management practices that go from the mountains to the sea. In Aotearoa, activities that are carried out in this land-marine interface, including those related to Nature-based Solutions (NbSs), are regulated by national, regional, and district policies (e.g., New Zealand Coastal Policy Statement, regional plans, and district plans). However, due to its novel character, not all current policies account for the realisation of NbSs nor are NbSs’ potential for addressing the wellbeing of our marine environments well understood.

This dissertation focuses on Tauranga Moana (the seas of Tauranga) as the chosen locality for the case study area, to:

i) investigate how the Ngapeke 7 Trust’s community participants in the Ngāti Pūkenga area of Tauranga Moana understand and value NbSs for addressing the wellbeing of their marine systems; and,
ii) review current planning policies and mechanisms to identify barriers, enablers, and gaps that support or hinder the implementation of NbSs in Tauranga Moana, observing through a Kaupapa Māori lens.

Findings emphasize that integrating mātauranga Māori and Māori Ecological Knowledge (MEK) with scientific knowledge offers a holistic approach to environmental management, enhancing decision-making, education, and policy. Key Māori values, including whakapapa, mauri, and kaitiakitanga, are central to this approach.

The research identifies gaps in policies regarding NbS realization and a need for greater understanding of NbS potential and Māori perspectives. Implications include the necessity of integrating MEK into environmental practices and policies, and the value of NbSs for effective and equitable environmental outcomes. Limitations include sample size and scope, which focused on the Ngapeke 7 block. This research contributes valuable insights for environmental planning and management by centring mātauranga Māori and values in NbS implementation for marine health.

year: 2025-04-16