title: Reduced MHD in Astrophysical Applications: Two-dimensional or Three-dimensional?

authors: Oughton, Sean

subjects: Science & Technology

abstract: Originally proposed as an efficient approach to computation of nonlinear dynamics in tokamak fusion research devices, reduced magnetohydrodynamics (RMHD) has subsequently found application in studies of coronal heating, flux tube dynamics, charged particle transport, and, in general, as an approximation to describe plasma turbulence in space physics and astrophysics. Given the diverse set of derivations available in the literature, there has emerged some level of discussion and a lack of consensus regarding the completeness of RMHD as a turbulence model, and its applicability in contexts such as the solar wind. Some of the key issues in this discussion are examined here, emphasizing that RMHD is properly neither 2D nor fully 3D, being rather an incomplete representation that enforces at least one family of extraneous conservation laws.

text: Reduced MHD in Astrophysical Applications: Two-dimensional or Three-dimensional? Originally proposed as an efficient approach to computation of nonlinear dynamics in tokamak fusion research devices, reduced magnetohydrodynamics (RMHD) has subsequently found application in studies of coronal heating, flux tube dynamics, charged particle transport, and, in general, as an approximation to describe plasma turbulence in space physics and astrophysics. Given the diverse set of derivations available in the literature, there has emerged some level of discussion and a lack of consensus regarding the completeness of RMHD as a turbulence model, and its applicability in contexts such as the solar wind. Some of the key issues in this discussion are examined here, emphasizing that RMHD is properly neither 2D nor fully 3D, being rather an incomplete representation that enforces at least one family of extraneous conservation laws.

year: 2017-04-10

title: For flux's sake: General considerations for energy-flux calculations in ecological communities

authors: Jochum, Malte

subjects: Science & Technology

abstract: Global change alters ecological communities with consequences for ecosystem processes. Such processes and functions are a central aspect of ecological research and vital to understanding and mitigating the consequences of global change, but also those of other drivers of change in organism communities. In this context, the concept of energy flux through trophic networks integrates food- web theory and biodiversity- ecosystem functioning theory and connects biodiversity to multitrophic ecosystem functioning. As such, the energy- flux approach is a strikingly effective tool to answer central questions in ecology and global- change research. This might seem straight forward, given that the theoretical background and software to efficiently calculate energy flux are readily available. However, the implementation of such calculations is not always straight forward, especially for those who are new to the topic and not familiar with concepts central to this line of research, such as food- web theory or metabolic theory. To facilitate wider use of energy flux in ecological research, we thus provide a guide to adopting energy- flux calculations for people new to the method, struggling with its implementation, or simply looking for background reading, important resources, and standard solutions to the problems everyone faces when starting to quantify energy fluxes for their community data. First, we introduce energy flux and its use in community and ecosystem ecology. Then, we provide a comprehensive explanation of the single steps towards calculating energy flux for community data. Finally, we discuss remaining challenges and exciting research frontiers for future energy- flux research.

text: For flux's sake: General considerations for energy-flux calculations in ecological communities Global change alters ecological communities with consequences for ecosystem processes. Such processes and functions are a central aspect of ecological research and vital to understanding and mitigating the consequences of global change, but also those of other drivers of change in organism communities. In this context, the concept of energy flux through trophic networks integrates food- web theory and biodiversity- ecosystem functioning theory and connects biodiversity to multitrophic ecosystem functioning. As such, the energy- flux approach is a strikingly effective tool to answer central questions in ecology and global- change research. This might seem straight forward, given that the theoretical background and software to efficiently calculate energy flux are readily available. However, the implementation of such calculations is not always straight forward, especially for those who are new to the topic and not familiar with concepts central to this line of research, such as food- web theory or metabolic theory. To facilitate wider use of energy flux in ecological research, we thus provide a guide to adopting energy- flux calculations for people new to the method, struggling with its implementation, or simply looking for background reading, important resources, and standard solutions to the problems everyone faces when starting to quantify energy fluxes for their community data. First, we introduce energy flux and its use in community and ecosystem ecology. Then, we provide a comprehensive explanation of the single steps towards calculating energy flux for community data. Finally, we discuss remaining challenges and exciting research frontiers for future energy- flux research.

year: 2021-09-14

title: Perceptions of coarse anglers and freshwater managers, and the impact of these perceptions on management of non-indigenous invasive fish

authors: Duggan, Kathryn S.

abstract: This report examines coarse angler attitudes and behaviours to determine the reasons for, and develop incentives to successfully discourage, deliberate spreads of coarse fish species. The perceptions of freshwater managers, and the ways in which these human perceptions influence management of non-indigenous invasive fish, are also explored. To achieve this two main methodological strategies were employed: (1) semi-structured interviews with representatives from management agencies, research providers, iwi, the New Zealand Federation of Coarse Anglers, and individual coarse anglers: and (2) an internet survey with individual coarse anglers. In contrast to many New Zealanders, coarse fish species are highly valued by coarse anglers and the practice of coarse fishing is an important part of their lives. While a large portion of coarse anglers state they would like more fishing opportunities (especially outside of the Auckland/Waikato region), they argue that they do not practice or support illegal spread of coarse fish.

text: Perceptions of coarse anglers and freshwater managers, and the impact of these perceptions on management of non-indigenous invasive fish This report examines coarse angler attitudes and behaviours to determine the reasons for, and develop incentives to successfully discourage, deliberate spreads of coarse fish species. The perceptions of freshwater managers, and the ways in which these human perceptions influence management of non-indigenous invasive fish, are also explored. To achieve this two main methodological strategies were employed: (1) semi-structured interviews with representatives from management agencies, research providers, iwi, the New Zealand Federation of Coarse Anglers, and individual coarse anglers: and (2) an internet survey with individual coarse anglers. In contrast to many New Zealanders, coarse fish species are highly valued by coarse anglers and the practice of coarse fishing is an important part of their lives. While a large portion of coarse anglers state they would like more fishing opportunities (especially outside of the Auckland/Waikato region), they argue that they do not practice or support illegal spread of coarse fish.

year: 2015