Theoretical foundation of 3D Alfvén resonances : normal modes

We consider the resonant coupling of fast and Alfvén magnetohydrodynamic (MHD) waves in a 3D equilibrium. Numerical solutions to normal modes (∝ exp(−iωt)) are presented, along with a theoretical framework to interpret them. The solutions we find are fundamentally different from those in 1D and 2D. In 3D there exists an infinite number of possible resonant solutions within a “Resonant Zone," and we show how boundary conditions and locally 2D regions can favor particular solutions. A unique feature of the resonance in 3D is switching between different permissible solutions when the boundary of the Resonant Zone is encountered. The theoretical foundation that we develop relies upon recognizing that in 3D the orientation of the resonant surface will not align in a simple fashion with an equilibrium coordinate. We present a method for generating the Alfvén wave natural frequencies for an arbitrarily oriented Alfvén wave, which requires a careful treatment of scale factors describing the background magnetic field geometry.PostprintPeer reviewe

It's Just My History Isn't It? Understanding smart journaling practices

Smart journals are both an emerging class of lifelogging applications and novel digital possessions, which are used to create and curate a personal record of one's life. Through an in-depth interview study of analogue and digital journaling practices, and by drawing on a wide range of research around 'technologies of memory', we address fundamental questions about how people manage and value digital records of the past. Appreciating journaling as deeply idiographic, we map a broad range of user practices and motivations and use this understanding to ground four design considerations: recognizing the motivation to account for one's life; supporting the authoring of a unique perspective and finding a place for passive tracking as a chronicle. Finally, we argue that smart journals signal a maturing orientation to issues of digital archiving

The theoretical foundation of 3-D Alfvén resonances : time-dependent solutions

Both authors were funded in part by STFC (through Consolidated Grant ST/N000609/1) and The Leverhulme Trust (through Research Grant RPG-2016-071).We present results from a 3-D numerical simulation which investigates the coupling of fast and Alfvén magnetohydrodynamic (MHD) waves in a nonuniform dipole equilibrium. This represents the time-dependent extension of the normal mode (∝ exp(−iωt)) analysis of Wright and Elsden (2016), and provides a theoretical basis for understanding 3-D Alfvén resonances. Wright and Elsden (2016) show that these are fundamentally different to resonances in 1D and 2D. We demonstrate the temporal behavior of the Alfvén resonance, which is formed within the "Resonant Zone"; a channel of the domain where a family of solutions exists such that the natural Alfvén frequency matches the fast-mode frequency. At early times, phase mixing leads to the production of prominent ridges in the energy density, whose shape is determined by the Alfvén speed profile and the chosen background magnetic field geometry. These off resonant ridges decay in time, leaving only a main 3-D resonant sheet in the steady state. We show that the width of the 3-D resonance in time and in space can be accurately estimated by adapting previous analytical estimates from 1-D theory. We further provide an analytical estimate for the resonance amplitude in 3-D, based upon extending 2-D theory.Publisher PDFPeer reviewe

Deciphering satellite observations of compressional ULF waveguide modes

T. Elsden would like to thank STFC for financial support for a doctoral training grant, number AMC3 STFC12. A.N. Wright was supported by STFC grant ST/N000609/1.We present an analytical method for determining incident and reflection co- efficients for flank ULF compressional waveguide modes in Earth’s magnetosphere. In the flank magnetosphere, compressional waves propagate azimuthally, but exhibit a mixed standing/propagating nature radially. Understanding this radial dependence will yield information on the energy absorption and transport of these waves. We provide a step by step method that can be applied to observations of flank ULF waves, which separates these fluctuations into incident and reflected parts. As a means of testing, we apply the method to data from a numerical waveguide simulation, which shows the effect on the reflection coefficient when energy is absorbed at a field line resonance.Publisher PDFPeer reviewe

Getting our hands dirty: why academics should design metrics and address the lack of transparency

Metrics in academia are often an opaque mess, filled with biases and ill-judged assumptions that are used in overly deterministic ways. By getting involved with their design, academics can productively push metrics in a more transparent direction. Chris Elsden, Sebastian Mellor and Rob Comber introduce an example of designing metrics within their own institution. Using the metric of grant income, their tool ResViz shows a chord diagram of academic collaboration and aims to encourage a multiplicity of interpretations

Darkening Programmable Donations

Around 2019, a group of researchers working with a large international charity, developed an innovative system for ‘programmable donations’. Riding a wave of hype related to blockchain technologies, they envisaged a way to support conditional and data-driven giving. The researchers realised that they could use ‘smart contracts’ to create digital escrows that could securely hold an individual donation, and only release when they received data about specified real-world conditions. While a number of commercial players were looking at means to use similar technologies to hold charities to account, and make funding conditional on detailed impact reporting from the 'last mile', this project had sought to flip attention to the 'first-mile' of giving, and donors own motivations and triggers for giving to charity. Although the system was developed carefully, with good intentions, this paper provides a speculative account of series of unfortunate events taking place years later, as the technology evolved and became misguided in various ways

HCI for Blockchain: Studying, Designing, Critiquing and Envisioning Distributed Ledger Technologies

This workshop aims to develop an agenda within the CHI community to address the emergence of blockchain, or distributed ledger technologies (DLTs). As blockchains emerge as a general purpose technology, with applications well beyond cryptocurrencies, DLTs present exciting challenges and opportunities for developing new ways for people and things to transact, collaborate, organize and identify themselves. Requiring interdisciplinary skills and thinking, the field of HCI is well placed to contribute to the research and development of this technology. This workshop will build a community for human-centred researchers and practitioners to present studies, critiques, design-led work, and visions of blockchain applications

Designing Second-Screening Experiences for Social Co-Selection and Critical Co-Viewing of Reality TV

Public commentary related to reality TV can be overwhelmed by thoughtless reactions and negative sentiments, which often problematically reinforce the cultural stereotyping typically employed in such media. We describe the design and month-long evaluation of a mobile "second-screening" application, Screenr, which uses co-voting and live textual tagging to encourage more critical co-viewing in these contexts. Our findings highlight how Screenr supported interrogation of the production qualities and claims of shows, promoted critical discourse around the motivations of programmes, and engaged participants in reflecting on their own assumptions and views. We situate our results within the context of existing second-screening co-viewing work, discuss implications for such technologies to support critical engagement with socio-political media, and provide design implications for future digital technologies in this domain

Transitions in digital personhood:Making sense of online activity in early retirement

We present findings from a qualitative study about how Internet use supports self-functioning following the life transition of retirement from work. This study recruited six recent retirees and included the deployment of OnLines, a design research artifact that logged and visualized key online services used by participants at home over four-weeks. The deployment was supported by pre- and post-deployment interviews. OnLines prompted participants’ reflection on their patterns of Internet use. Position Exchange Theory was used to understand retirees’ sense making from a lifespan perspective, informing the design of supportive online services. This paper delivers a three-fold contribution to the field of human-computer interaction, advancing a lifespan-oriented approach by conceptualizing the self as a dialogical phenomenon that develops over time, advancing the ageing discourse by reporting on retirees’ complex identities in the context of their life histories, and advancing discourse on research through design by developing OnLines to foster participant-researcher reflection informed by Self Psychology