title: A turbulence-driven model for heating and acceleration of the fastwind in coronal holes

authors: Verdini, A.

subjects: MHD

abstract: A model is presented for generation of fast solar wind in coronal holes, relying on heating that is dominated by turbulent dissipation of MHD fluctuations transported upward in the solar atmosphere. Scale-separated transport equations include large-scale fields, transverse Alfvénic fluctuations, and a small compressive dissipation due to parallel shears near the transition region. The model accounts for proton temperature, density, wind speed, and fluctuation amplitude as observed in remote sensing and in situ satellite data.

text: A turbulence-driven model for heating and acceleration of the fastwind in coronal holes A model is presented for generation of fast solar wind in coronal holes, relying on heating that is dominated by turbulent dissipation of MHD fluctuations transported upward in the solar atmosphere. Scale-separated transport equations include large-scale fields, transverse Alfvénic fluctuations, and a small compressive dissipation due to parallel shears near the transition region. The model accounts for proton temperature, density, wind speed, and fluctuation amplitude as observed in remote sensing and in situ satellite data.

year: 2010

title: A perturbative approach to a nonlinear advection-diffusion equation of particle transport

authors: Walter, Dominik

subjects: Science & Technology

abstract: We explore analytical techniques for modeling the nonlinear cosmic ray transport in various astrophysical environments which is of significant current research interest. While nonlinearity is most often described by coupled equations for the dynamics of the thermal plasma and the cosmic ray transport or for the transport of the plasma waves and the cosmic rays, we study the case of a single but nonlinear advection-diffusion equation. The latter can be approximately solved analytically or semi-analytically, with the advantage that these solutions are easy to use and, thus, can facilitate a quantitative comparison to data. In the present study, we extend our previous work in a twofold manner. First, instead of employing an integral method to the case of pure nonlinear diffusion, we apply an expansion technique to the advection-diffusion equation. We use the technique systematically to analyze the effect of nonlinear diffusion for the cases of constant and spatially varying advection combined with time-varying source functions. Second, we extend the study from the one-dimensional, Cartesian geometry to the radially symmetric case, which allows us to treat more accurately the nonlinear diffusion problems on larger scales away from the source.

text: A perturbative approach to a nonlinear advection-diffusion equation of particle transport We explore analytical techniques for modeling the nonlinear cosmic ray transport in various astrophysical environments which is of significant current research interest. While nonlinearity is most often described by coupled equations for the dynamics of the thermal plasma and the cosmic ray transport or for the transport of the plasma waves and the cosmic rays, we study the case of a single but nonlinear advection-diffusion equation. The latter can be approximately solved analytically or semi-analytically, with the advantage that these solutions are easy to use and, thus, can facilitate a quantitative comparison to data. In the present study, we extend our previous work in a twofold manner. First, instead of employing an integral method to the case of pure nonlinear diffusion, we apply an expansion technique to the advection-diffusion equation. We use the technique systematically to analyze the effect of nonlinear diffusion for the cases of constant and spatially varying advection combined with time-varying source functions. Second, we extend the study from the one-dimensional, Cartesian geometry to the radially symmetric case, which allows us to treat more accurately the nonlinear diffusion problems on larger scales away from the source.

year: 2020

title: 'Making its own history': New Zealand historical fiction for children,1862-2008

authors: Clark, Louise Henriette

subjects: children's literature

abstract: This thesis considers historical fiction for children and young people dealing with New Zealand history from the arrival of the first Polynesian settlers to the end of the nineteenth century.  It provides both a comprehensive survey of historical novels published between 1862 and the end of 2008, and an analysis of the way the same historical events and periods have been depicted in historical novels written at different times.  Individual chapters discuss books set during specific historical periods or dealing with particular events - the pre-European period, early contact, nineteenth century immigration, the New Zealand Wars, the gold rushes, and the colonial period - in chronological order of publication.  Since children's literature is particularly adept at reflecting and promoting the dominant ideas of the society in which it is produced, the chronological consideration of these texts reveals contemporary attitudes to such issues as race relations, gender roles, class, war and conflict, and concepts of national identity, as well as the way historical fiction has responded to societal changes since the 1860s.  

The predominant themes of historical fiction set prior to 1900 are: the arrival of settlers in New Zealand; encounters with the country's indigenous inhabitants; the taming of the often hostile landscape; the assertion of the settlers' claims to 'belong' in their new land; and the establishment of New Zealand as a nation with distinctive characteristics.  There are perceptible nuances and differences in the way these themes are discussed depending on the historical moment in which individual authors are writing.  Novels of the Victorian period and early twentieth century reflect the imperialistic and evangelistic ethos of the time, and present the British settlers' right to colonize the land and the ensuing dispossession of Māori as largely unproblematic.  Subsequent historical novels, particularly those written since the 1960s, offer a more inclusive version of New Zealand history, although the lack of historical fiction for children by Māori writers means that Eurocentric views of history continue to dominate, and that all representations of Māori and their history are mediated through Pakeha writers.

Shifts in social attitudes have resulted in changes in the treatment of Māori in historical novels for children, and similar changes have occurred in the portrayal of gender, class, and ethnicity.  The passage of time has seen increased agency and a wider variety of roles allocated to Māori, female and working class characters, as well as greater ethnic diversity.  Developments in New Zealand historiography are also reflected in fiction, although at times historical fiction prefigures written histories, or provides alternative views by depicting the experience of women, children and Māori, who often did not feature in conventional histories.  While many historical novels for children, especially the earlier texts, are adventure stories set in the past and are not necessarily concerned with historical verisimilitude, an increasing number attempt to present authentic recreations of historical periods, including accounts of actual people and events, based on extensive research, and reinforced with peritextual material in the form of historical notes, bibliographies, maps and photographs.  

The role of New Zealand historical fiction for children and young people has been not only to entertain young readers and inform them about their country's past, but to create and foster a sense of national identity.

text: 'Making its own history': New Zealand historical fiction for children,1862-2008 This thesis considers historical fiction for children and young people dealing with New Zealand history from the arrival of the first Polynesian settlers to the end of the nineteenth century.  It provides both a comprehensive survey of historical novels published between 1862 and the end of 2008, and an analysis of the way the same historical events and periods have been depicted in historical novels written at different times.  Individual chapters discuss books set during specific historical periods or dealing with particular events - the pre-European period, early contact, nineteenth century immigration, the New Zealand Wars, the gold rushes, and the colonial period - in chronological order of publication.  Since children's literature is particularly adept at reflecting and promoting the dominant ideas of the society in which it is produced, the chronological consideration of these texts reveals contemporary attitudes to such issues as race relations, gender roles, class, war and conflict, and concepts of national identity, as well as the way historical fiction has responded to societal changes since the 1860s.  

The predominant themes of historical fiction set prior to 1900 are: the arrival of settlers in New Zealand; encounters with the country's indigenous inhabitants; the taming of the often hostile landscape; the assertion of the settlers' claims to 'belong' in their new land; and the establishment of New Zealand as a nation with distinctive characteristics.  There are perceptible nuances and differences in the way these themes are discussed depending on the historical moment in which individual authors are writing.  Novels of the Victorian period and early twentieth century reflect the imperialistic and evangelistic ethos of the time, and present the British settlers' right to colonize the land and the ensuing dispossession of Māori as largely unproblematic.  Subsequent historical novels, particularly those written since the 1960s, offer a more inclusive version of New Zealand history, although the lack of historical fiction for children by Māori writers means that Eurocentric views of history continue to dominate, and that all representations of Māori and their history are mediated through Pakeha writers.

Shifts in social attitudes have resulted in changes in the treatment of Māori in historical novels for children, and similar changes have occurred in the portrayal of gender, class, and ethnicity.  The passage of time has seen increased agency and a wider variety of roles allocated to Māori, female and working class characters, as well as greater ethnic diversity.  Developments in New Zealand historiography are also reflected in fiction, although at times historical fiction prefigures written histories, or provides alternative views by depicting the experience of women, children and Māori, who often did not feature in conventional histories.  While many historical novels for children, especially the earlier texts, are adventure stories set in the past and are not necessarily concerned with historical verisimilitude, an increasing number attempt to present authentic recreations of historical periods, including accounts of actual people and events, based on extensive research, and reinforced with peritextual material in the form of historical notes, bibliographies, maps and photographs.  

The role of New Zealand historical fiction for children and young people has been not only to entertain young readers and inform them about their country's past, but to create and foster a sense of national identity.

year: 2010