title: MHD‐driven kinetic dissipation in the solar wind and corona

authors: Leamon, R. J.

subjects: MHD

abstract: Mechanisms for the deposition of heat in the lower coronal plasma are discussed, emphasizing recent attempts to reconcile the fluid and kinetic perspectives. Structures at magnetohydrodynamic (MHD) scales may drive a nonlinear cascade, preferentially exciting high perpendicular wavenumber fluctuations. Relevant dissipative kinetic processes must be identified that can absorb the associated energy flux. The relationship between the MHD cascade and direct cyclotron absorption, including cyclotron sweep, is discussed. We conclude that for coronal and solar wind parameters the perpendicular cascade cannot be neglected and may be more rapid than cyclotron sweep. Solar wind observational evidence suggests the relevance of the ion inertial scale, which is associated with current sheet thickness during reconnection. We conclude that a significant fraction of dissipation in the corona and solar wind likely proceeds through a perpendicular cascade and small-scale reconnection, coupled to kinetic processes that act at oblique wavevectors.

text: MHD‐driven kinetic dissipation in the solar wind and corona Mechanisms for the deposition of heat in the lower coronal plasma are discussed, emphasizing recent attempts to reconcile the fluid and kinetic perspectives. Structures at magnetohydrodynamic (MHD) scales may drive a nonlinear cascade, preferentially exciting high perpendicular wavenumber fluctuations. Relevant dissipative kinetic processes must be identified that can absorb the associated energy flux. The relationship between the MHD cascade and direct cyclotron absorption, including cyclotron sweep, is discussed. We conclude that for coronal and solar wind parameters the perpendicular cascade cannot be neglected and may be more rapid than cyclotron sweep. Solar wind observational evidence suggests the relevance of the ion inertial scale, which is associated with current sheet thickness during reconnection. We conclude that a significant fraction of dissipation in the corona and solar wind likely proceeds through a perpendicular cascade and small-scale reconnection, coupled to kinetic processes that act at oblique wavevectors.

year: 2000

title: The energy cultures framework: Exploring the role of norms, practices and material culture in shaping energy behaviour in New Zealand

authors: Stephenson, Janet

subjects: Energy behaviour

abstract: The energy cultures framework was developed in 2009 to support interdisciplinary investigation into energy behaviour in New Zealand. In this paper, we discuss the framework in light of 5 years of empirical application and conceptual development. The concept of culture is helpful in seeking to better understand energy behaviour because it conveys how behaviours are embedded within the physical and social contexts of everyday life, and how they are both repetitive and heterogeneous. The framework suggests that the energy culture of a given subject (e.g. an individual, a household, a business, a sector) can be studied by examining the interrelationships between their norms, practices and material culture, and how these, in turn, are shaped by external influences. We discuss the key theoretical influences of the framework, and how the core concepts of the framework have evolved as we have applied them in different research situations. We then illustrate how we have applied the framework to a range of topics and sectors, and how it has been used to support interdisciplinary research, in identifying clusters of energy cultures, in examining energy cultures at different scales and in different sectors, and to inform policy development.

text: The energy cultures framework: Exploring the role of norms, practices and material culture in shaping energy behaviour in New Zealand The energy cultures framework was developed in 2009 to support interdisciplinary investigation into energy behaviour in New Zealand. In this paper, we discuss the framework in light of 5 years of empirical application and conceptual development. The concept of culture is helpful in seeking to better understand energy behaviour because it conveys how behaviours are embedded within the physical and social contexts of everyday life, and how they are both repetitive and heterogeneous. The framework suggests that the energy culture of a given subject (e.g. an individual, a household, a business, a sector) can be studied by examining the interrelationships between their norms, practices and material culture, and how these, in turn, are shaped by external influences. We discuss the key theoretical influences of the framework, and how the core concepts of the framework have evolved as we have applied them in different research situations. We then illustrate how we have applied the framework to a range of topics and sectors, and how it has been used to support interdisciplinary research, in identifying clusters of energy cultures, in examining energy cultures at different scales and in different sectors, and to inform policy development.

year: 2015

title: Two-step human−environmental impact history for northern New Zealand linked to late-Holocene climate change

authors: Newnham, Rewi M.

subjects: New Zealand

abstract: Following resolution of a long-standing debate over the timing of the initial settlement of New Zealand from Polynesia (late 13th century), a prevailing paradigm has developed that invokes rapid transformation of the landscape, principally by fire, within a few decades of the first arrivals. This model has been constructed from evidence mostly from southern and eastern regions of New Zealand, but a more complicated pattern may apply in the more humid western and northern regions where forests are more resilient to burning. We present a new pollen record from Lake Pupuke, Auckland, northern New Zealand, that charts the changing vegetation cover over the last 1000 years, before and after the arrival of people. Previous results from this site concurred with the rapid transformation model, although sampling resolution, chronology and sediment disturbance make that interpretation equivocal. Our new record is dated principally by tephrochronology together with radiocarbon dating, and includes a cryptotephra deposit identified as Kaharoa tephra, a key marker for first settlement in northern New Zealand. Its discovery and stratigraphic position below two Rangitoto-derived tephras enables a clearer picture of environmental change to be drawn. The new pollen record shows an early phase (step 1) of minor, localised forest clearance around the time of Kaharoa tephra (c. 1314 AD) followed by a later, more extensive deforestation phase (step 2) commencing at around the time of deposition of the Rangitoto tephras (c. 1400‒1450 AD). This pattern, which needs to be corroborated from other well-resolved records from northern New Zealand, concurs with an emerging hypothesis that the ‘Little Ice Age’ had a significant impact on pre-European Māori with the onset of harsher conditions causing a consolidation of populations and later environmental impact in northern New Zealand.

text: Two-step human−environmental impact history for northern New Zealand linked to late-Holocene climate change Following resolution of a long-standing debate over the timing of the initial settlement of New Zealand from Polynesia (late 13th century), a prevailing paradigm has developed that invokes rapid transformation of the landscape, principally by fire, within a few decades of the first arrivals. This model has been constructed from evidence mostly from southern and eastern regions of New Zealand, but a more complicated pattern may apply in the more humid western and northern regions where forests are more resilient to burning. We present a new pollen record from Lake Pupuke, Auckland, northern New Zealand, that charts the changing vegetation cover over the last 1000 years, before and after the arrival of people. Previous results from this site concurred with the rapid transformation model, although sampling resolution, chronology and sediment disturbance make that interpretation equivocal. Our new record is dated principally by tephrochronology together with radiocarbon dating, and includes a cryptotephra deposit identified as Kaharoa tephra, a key marker for first settlement in northern New Zealand. Its discovery and stratigraphic position below two Rangitoto-derived tephras enables a clearer picture of environmental change to be drawn. The new pollen record shows an early phase (step 1) of minor, localised forest clearance around the time of Kaharoa tephra (c. 1314 AD) followed by a later, more extensive deforestation phase (step 2) commencing at around the time of deposition of the Rangitoto tephras (c. 1400‒1450 AD). This pattern, which needs to be corroborated from other well-resolved records from northern New Zealand, concurs with an emerging hypothesis that the ‘Little Ice Age’ had a significant impact on pre-European Māori with the onset of harsher conditions causing a consolidation of populations and later environmental impact in northern New Zealand.

year: 2018