title: Generation of X-points and secondary islands in 2D magnetohydrodynamic turbulence

authors: Wan, Minping

abstract: We study the time development of the population of X-type critical points in a two-dimensional magnetohydrodynamic model during the early stages of freely decaying turbulence. At sufficiently high magnetic Reynolds number Rem, we find that the number of neutral points increases as Rem3/2, while the rates of reconnection at the most active sites decrease. The distribution of rates remains approximately exponential. We focus in particular on delicate issues of accuracy, which arise in these numerical experiments, in that the proliferation of X-points is also a feature of under-resolved simulations. The “splitting” of neutral points at high Reynolds number appears to be a fundamental feature of the cascade that has important implications for understanding the relationship between reconnection and turbulence, an issue of considerable importance for the Magnetospheric Multiscale and Solar Probe missions as well as observation of reconnection in the solar wind.

text: Generation of X-points and secondary islands in 2D magnetohydrodynamic turbulence We study the time development of the population of X-type critical points in a two-dimensional magnetohydrodynamic model during the early stages of freely decaying turbulence. At sufficiently high magnetic Reynolds number Rem, we find that the number of neutral points increases as Rem3/2, while the rates of reconnection at the most active sites decrease. The distribution of rates remains approximately exponential. We focus in particular on delicate issues of accuracy, which arise in these numerical experiments, in that the proliferation of X-points is also a feature of under-resolved simulations. The “splitting” of neutral points at high Reynolds number appears to be a fundamental feature of the cascade that has important implications for understanding the relationship between reconnection and turbulence, an issue of considerable importance for the Magnetospheric Multiscale and Solar Probe missions as well as observation of reconnection in the solar wind.

year: 2013

title: Relationship between meteoric ¹⁰Be and NO₃⁻ concentrations in soils along Shackleton Glacier, Antarctica

authors: Diaz, Melisa A.

abstract: Outlet glaciers that flow through the Transantarctic Mountains (TAM) experienced changes in ice thickness greater than other coastal regions of Antarctica during glacial maxima. As a result, ice-free areas that are currently exposed may have been covered by ice at various points during the Cenozoic, complicating our understanding of ecological succession in TAM soils. Our knowledge of glacial extent on small spatial scales is limited for the TAM, and studies of soil exposure duration and disturbance, in particular, are rare. We collected surface soil samples and, in some places, depth profiles every 5 cm to refusal (up to 30 cm) from 11 ice-free areas along Shackleton Glacier, a major outlet glacier of the East Antarctic Ice Sheet. We explored the relationship between meteoric ¹⁰Be and NO₃⁻ in these soils as a tool for understanding landscape disturbance and wetting history and as exposure proxies. Concentrations of meteoric ¹⁰Be spanned more than an order of magnitude across the region (2.9×108 to 73×108 atoms g⁻¹) and are among the highest measured in polar regions. The concentrations of NO₃⁻ were similarly variable and ranged from ∼ μg g⁻¹ to 15 mg g⁻¹. In examining differences and similarities in the concentrations of ¹⁰Be and NO₃⁻ with depth, we suggest that much of the southern portion of the Shackleton Glacier region has likely developed under a hyper-arid climate regime with minimal disturbance. Finally, we inferred exposure time using ¹⁰Be concentrations. This analysis indicates that the soils we analyzed likely range from recent exposure (following the Last Glacial Maximum) to possibly >6 Myr. We suggest that further testing and interrogation of meteoric ¹⁰Be and NO₃⁻ concentrations and relationships in soils can provide important information regarding landscape development, soil evolution processes, and inferred exposure durations of surfaces in the TAM.

text: Relationship between meteoric ¹⁰Be and NO₃⁻ concentrations in soils along Shackleton Glacier, Antarctica Outlet glaciers that flow through the Transantarctic Mountains (TAM) experienced changes in ice thickness greater than other coastal regions of Antarctica during glacial maxima. As a result, ice-free areas that are currently exposed may have been covered by ice at various points during the Cenozoic, complicating our understanding of ecological succession in TAM soils. Our knowledge of glacial extent on small spatial scales is limited for the TAM, and studies of soil exposure duration and disturbance, in particular, are rare. We collected surface soil samples and, in some places, depth profiles every 5 cm to refusal (up to 30 cm) from 11 ice-free areas along Shackleton Glacier, a major outlet glacier of the East Antarctic Ice Sheet. We explored the relationship between meteoric ¹⁰Be and NO₃⁻ in these soils as a tool for understanding landscape disturbance and wetting history and as exposure proxies. Concentrations of meteoric ¹⁰Be spanned more than an order of magnitude across the region (2.9×108 to 73×108 atoms g⁻¹) and are among the highest measured in polar regions. The concentrations of NO₃⁻ were similarly variable and ranged from ∼ μg g⁻¹ to 15 mg g⁻¹. In examining differences and similarities in the concentrations of ¹⁰Be and NO₃⁻ with depth, we suggest that much of the southern portion of the Shackleton Glacier region has likely developed under a hyper-arid climate regime with minimal disturbance. Finally, we inferred exposure time using ¹⁰Be concentrations. This analysis indicates that the soils we analyzed likely range from recent exposure (following the Last Glacial Maximum) to possibly >6 Myr. We suggest that further testing and interrogation of meteoric ¹⁰Be and NO₃⁻ concentrations and relationships in soils can provide important information regarding landscape development, soil evolution processes, and inferred exposure durations of surfaces in the TAM.

year: 2021

title: Tangi and State Funeral: Te Arikinui Dame Te Atairangikaahu and Prime Minister Norman Kirk

authors: McRae, Karyn Okeroa

subjects: Tangi

abstract: The tangi of Te Arikinui Dame Te Atairangikaahu (Te Arikinui) in 2006 paralleled the State funerals for New Zealand Prime Ministers like Norman Kirk who died in 1974. State funerals require the huge mobilization of people and resources and always attract the attention of the national and international media. The death of a Prime Minister is news worthy, but what of a minority indigenous fourth world leader like Te Arikinui? Why did her passing attract so much media attention? In this study I argue that media representation of the tangi of Te Arikinui was largely about social, cultural and symbolic capital. In media saturated societies such as Aotearoa/New Zealand, through mainstream media outlets like TV One News and the Waikato Times, Te Arikinui’s tangi event claimed a dominant space in the lives of Maori and non Maori alike. The data source includes print news media coverage of the tangi of Te Arikinui and the State funeral of Norman Kirk. Descriptive narrative and abductive analysis inform the methodology used in this study. As expected, print media reporting of both events progressed through the three stages identified by Durkheim, those of, separation, liminality and reincorporation. The ownership of death, the deceased and the continued possession of their mortal remains, itself a cultural object with symbolic and cultural capital, reflected the actual power and control of the possessor. State funerals and tangi are about the ritualized performance of grief and mourning, and require the appropriate social, cultural and symbolic capital for its enactment.

text: Tangi and State Funeral: Te Arikinui Dame Te Atairangikaahu and Prime Minister Norman Kirk The tangi of Te Arikinui Dame Te Atairangikaahu (Te Arikinui) in 2006 paralleled the State funerals for New Zealand Prime Ministers like Norman Kirk who died in 1974. State funerals require the huge mobilization of people and resources and always attract the attention of the national and international media. The death of a Prime Minister is news worthy, but what of a minority indigenous fourth world leader like Te Arikinui? Why did her passing attract so much media attention? In this study I argue that media representation of the tangi of Te Arikinui was largely about social, cultural and symbolic capital. In media saturated societies such as Aotearoa/New Zealand, through mainstream media outlets like TV One News and the Waikato Times, Te Arikinui’s tangi event claimed a dominant space in the lives of Maori and non Maori alike. The data source includes print news media coverage of the tangi of Te Arikinui and the State funeral of Norman Kirk. Descriptive narrative and abductive analysis inform the methodology used in this study. As expected, print media reporting of both events progressed through the three stages identified by Durkheim, those of, separation, liminality and reincorporation. The ownership of death, the deceased and the continued possession of their mortal remains, itself a cultural object with symbolic and cultural capital, reflected the actual power and control of the possessor. State funerals and tangi are about the ritualized performance of grief and mourning, and require the appropriate social, cultural and symbolic capital for its enactment.

year: 2010