title: Simulations of 3D Magnetic Merging: Resistive Scalings for Null Point and QSL Reconnection

authors: Effenberger, Frederic

subjects: Science & Technology

abstract: Starting from an exact, steady-state, force-free solution of the magnetohydrodynamic (MHD) equations, we investigate how resistive current layers are induced by perturbing line-tied three-dimensional magnetic equilibria. This is achieved by the superposition of a weak perturbation field in the domain, in contrast to studies where the boundary is driven by slow motions, like those present in photospheric active regions. Our aim is to quantify how the current structures are altered by the contribution of so-called quasi-separatrix layers (QSLs) as the null point is shifted outside the computational domain. Previous studies based on magneto-frictional relaxation have indicated that despite the severe field line gradients of the QSL, the presence of a null is vital in maintaining fast reconnection. Here, we explore this notion using highly resolved simulations of the full MHD evolution. We show that for the null-point configuration, the resistive scaling of the peak current density is close to  J∼η−¹, while the scaling is much weaker, i.e.  J∼η⁻⁰.⁴, when only the QSL connectivity gradients provide a site for the current accumulation.

text: Simulations of 3D Magnetic Merging: Resistive Scalings for Null Point and QSL Reconnection Starting from an exact, steady-state, force-free solution of the magnetohydrodynamic (MHD) equations, we investigate how resistive current layers are induced by perturbing line-tied three-dimensional magnetic equilibria. This is achieved by the superposition of a weak perturbation field in the domain, in contrast to studies where the boundary is driven by slow motions, like those present in photospheric active regions. Our aim is to quantify how the current structures are altered by the contribution of so-called quasi-separatrix layers (QSLs) as the null point is shifted outside the computational domain. Previous studies based on magneto-frictional relaxation have indicated that despite the severe field line gradients of the QSL, the presence of a null is vital in maintaining fast reconnection. Here, we explore this notion using highly resolved simulations of the full MHD evolution. We show that for the null-point configuration, the resistive scaling of the peak current density is close to  J∼η−¹, while the scaling is much weaker, i.e.  J∼η⁻⁰.⁴, when only the QSL connectivity gradients provide a site for the current accumulation.

year: 2016

title: “It gave me a much more personal connection”: Student generated podcasting and assessment in teacher education

authors: Forbes, Dianne Leslie

subjects: teacher education

abstract: This paper reports on a qualitative case study of an online initial teacher education class in New Zealand, exploring the potential of student-generated podcasts as a form of interactive formative assessment. Findings from interviews with teaching staff indicate that podcasting was useful for supporting multimodal learning valuing student voice and reflections. Podcasting enhanced the affective and relational connections in the online class, and empowered students to develop technical skills and confidence relevant in their teaching careers. As such, this study positions educators as future makers and as leaders in a climate of change. We suggest implications for student-generated podcasts in similar contexts.

text: “It gave me a much more personal connection”: Student generated podcasting and assessment in teacher education This paper reports on a qualitative case study of an online initial teacher education class in New Zealand, exploring the potential of student-generated podcasts as a form of interactive formative assessment. Findings from interviews with teaching staff indicate that podcasting was useful for supporting multimodal learning valuing student voice and reflections. Podcasting enhanced the affective and relational connections in the online class, and empowered students to develop technical skills and confidence relevant in their teaching careers. As such, this study positions educators as future makers and as leaders in a climate of change. We suggest implications for student-generated podcasts in similar contexts.

year: 2012

title: Te kaumoana Poronīhia: Ngā terenga onamata

authors: Tuaupiki, Jackie Whetumarama

subjects: Kōrero nehe

abstract: Tā tēnei tuhinga e whai ake nei, he wānanga i ngā pūtake o te whanaketanga mai o ngā iwi, nāna ngā motu o Poronīhia i whakakāinga, ka utaina te karangatanga ki runga ki a rātou, he iwi Poronīhia. Ko te pātai matua, i ahu mai ngā iwi Poronīhia i whea? Tēnei, ka hahaina ngā whakaaro Māori me ngā whakaaro Tauiwi e pā ana ki te pūtakenga mai o te iwi tāngata ki te ao. I konei, ka kitea te rerekē o te titiro ā-ao a ēnei iwi tāngata.

Ka ū te titiro ki Hawaiki, e tau ana ngā kōrero tuku iho a te ao Māori, ki te ao Poronīhia hoki. E mea ana te Māori, he tūrangawaewae taurikura a Hawaiki, he pā whakawairua hoki. Ka riariakina e au ngā whakapae mō tēnei karangatanga kāinga i mau roa ai i ōna iwi kōrero.

Ka huri rā ki te āta whakatewhatewha i ngā rangahau mō te horanga haeretanga o te iwi tāngata mai i whirika, ki  hia ki te tonga mā rāwhiti, ā, tau atu rā ki roto i ngā whaitua moana o Poronīhia. I konei, kua āta wānangahia e au ngā whakapae huhua mō ngā take i horapa haere ai ēnei iwi ki roto o Poronīhia, ka tahi. Ka rua, ka tirohia ngā tohe e pā ana ki tō rātou āheinga ki te whakatere i ō rātou waka. Ko ēnei kōrero, he whakatuwhera i te pūtea mātauranga mō runga i ngā mahi whakatere waka a ngā tūpuna Poronīhia.

text: Te kaumoana Poronīhia: Ngā terenga onamata Tā tēnei tuhinga e whai ake nei, he wānanga i ngā pūtake o te whanaketanga mai o ngā iwi, nāna ngā motu o Poronīhia i whakakāinga, ka utaina te karangatanga ki runga ki a rātou, he iwi Poronīhia. Ko te pātai matua, i ahu mai ngā iwi Poronīhia i whea? Tēnei, ka hahaina ngā whakaaro Māori me ngā whakaaro Tauiwi e pā ana ki te pūtakenga mai o te iwi tāngata ki te ao. I konei, ka kitea te rerekē o te titiro ā-ao a ēnei iwi tāngata.

Ka ū te titiro ki Hawaiki, e tau ana ngā kōrero tuku iho a te ao Māori, ki te ao Poronīhia hoki. E mea ana te Māori, he tūrangawaewae taurikura a Hawaiki, he pā whakawairua hoki. Ka riariakina e au ngā whakapae mō tēnei karangatanga kāinga i mau roa ai i ōna iwi kōrero.

Ka huri rā ki te āta whakatewhatewha i ngā rangahau mō te horanga haeretanga o te iwi tāngata mai i whirika, ki  hia ki te tonga mā rāwhiti, ā, tau atu rā ki roto i ngā whaitua moana o Poronīhia. I konei, kua āta wānangahia e au ngā whakapae huhua mō ngā take i horapa haere ai ēnei iwi ki roto o Poronīhia, ka tahi. Ka rua, ka tirohia ngā tohe e pā ana ki tō rātou āheinga ki te whakatere i ō rātou waka. Ko ēnei kōrero, he whakatuwhera i te pūtea mātauranga mō runga i ngā mahi whakatere waka a ngā tūpuna Poronīhia.

year: 2017