2024-03-28T18:38:12Zhttps://research-repository.st-andrews.ac.uk/oai/requestoai:research-repository.st-andrews.ac.uk:10023/84232023-04-18T10:07:24Zcom_10023_92com_10023_28com_10023_94com_10023_879com_10023_878col_10023_96col_10023_98col_10023_880
Effects of thermal conduction and compressive viscosity on the period ratio of the slow mode
Macnamara, Cicely Krystyna
Roberts, Bernard
PPARC - Now STFC
University of St Andrews. Applied Mathematics
University of St Andrews. Pure Mathematics
Sun: corona
Sun: oscillations
QB Astronomy
QC Physics
C.K.M. acknowledges financial support from the CarnegieTrust. Discussions with Dr. I. De Moortel and Prof. A. W. Hood are gratefully acknowledged
Aims: Increasing observational evidence of wave modes brings us to a closer understanding of the solar corona. Coronal seismology allows us to combine wave observations and theory to determine otherwise unknown parameters. The period ratio, P1/2P2, between the period P1 of the fundamental mode and the period P2 of its first overtone, is one such tool of coronal seismology and its departure from unity provides information about the structure of the corona. Methods: We consider analytically the effects of thermal conduction and compressive viscosity on the period ratio for a longitudinally propagating sound wave. Results: For coronal values of thermal conduction the effect on the period ratio is negligible. For compressive viscosity the effect on the period ratio may become important for some short hot loops. Conclusions: Damping typically has a small effect on the period ratio, suggesting that longitudinal structuring remains the most significant effect.
2016-03-16
2016-03-16
2010-06
Journal article
Macnamara , C K & Roberts , B 2010 , ' Effects of thermal conduction and compressive viscosity on the period ratio of the slow mode ' , Astronomy & Astrophysics , vol. 515 , A41 . https://doi.org/10.1051/0004-6361/200913409
0004-6361
PURE: 241566046
PURE UUID: 7b2d0981-a5ba-487d-8cbc-459360f156ff
Scopus: 77953277125
ORCID: /0000-0003-4961-6052/work/27162491
http://hdl.handle.net/10023/8423
https://doi.org/10.1051/0004-6361/200913409
PP/E001122/1
eng
Astronomy & Astrophysics
© 2010, Publisher / the Author(s). This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at www.aanda.org / https://dx.doi.org/10.1051/0004-6361/200913409
oai:research-repository.st-andrews.ac.uk:10023/102802022-04-05T15:31:37Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Forward modeling of gyrosynchrotron intensity perturbations by sausage modes
Reznikova, V. E.
Antolin, P.
Van Doorsselaere, T.
University of St Andrews. Applied Mathematics
Sun: flares
Sun: oscillations
Sun: radio radiation
Waves
QB Astronomy
QC Physics
To determine the observable radio signatures of the fast sausagestanding wave, we examine gyrosynchrotron (GS) emission modulation usinga linear three-dimensional magnetohydrodynamic model of a plasmacylinder. Effects of the line-of-sight angle and instrumental resolutionon perturbations of the GS intensity are analyzed for two models: a basemodel with strong Razin suppression and a low-density model in which theRazin effect was unimportant. Our finding contradicts previouspredictions made with simpler models: an in-phase variation of intensitybetween low (f <fpeak) and high (f > fpeak) frequencies is found for the low-density model and ananti-phase variation for the base model in the case of a viewing angleof 45°. The spatially inhomogeneous character of the oscillatingemission source and the spatial resolution of the model are found tohave a significant effect on the resulting intensity.
2017-02-13
2017-02-13
2014-03-28
Journal article
Reznikova , V E , Antolin , P & Van Doorsselaere , T 2014 , ' Forward modeling of gyrosynchrotron intensity perturbations by sausage modes ' , Astrophysical Journal , vol. 785 , no. 2 , 86 . https://doi.org/10.1088/0004-637X/785/2/86
0004-637X
PURE: 248970011
PURE UUID: 6376cf1e-1fae-4317-a4a8-778260b29438
BibCode: 2014ApJ...785...86R
Scopus: 84898005050
http://hdl.handle.net/10023/10280
https://doi.org/10.1088/0004-637X/785/2/86
http://adsabs.harvard.edu/abs/2014ApJ...785...86R
eng
Astrophysical Journal
© 2014. The American Astronomical Society. All rights reserved. Printed in the U.S.A. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at: https://dx.doi.org/10.1088/0004-637X/785/2/86
oai:research-repository.st-andrews.ac.uk:10023/36982022-04-14T15:30:43Zcom_10023_92com_10023_28com_10023_792com_10023_39com_10023_879com_10023_878col_10023_96col_10023_795col_10023_880
Two-dimensional magnetohydrodynamic turbulence in the small magnetic Prandtl number limit
Dritschel, David Gerard
Tobias, Steve
University of St Andrews. Applied Mathematics
University of St Andrews. Scottish Oceans Institute
University of St Andrews. Marine Alliance for Science & Technology Scotland
Computational methods
MHD turbulence
Turbulence simulation
QA Mathematics
In this paper we introduce a new method for computations of two-dimensional magnetohydrodynamic (MHD) turbulence at low magnetic Prandtl number $\Pra=\nu/\eta$. When $\Pra \ll 1$, the magnetic field dissipates at a scale much larger than the velocity field. The method we utilise is a novel hybrid contour--spectral method, the ``Combined Lagrangian Advection Method'', formally to integrate the equations with zero viscous dissipation. The method is compared with a standard pseudo-spectral method for decreasing $\Pra$ for the problem of decaying two-dimensional MHD turbulence. The method is shown to agree well for a wide range of imposed magnetic field strengths. Examples of problems for which such a method may prove invaluable are also given.
2013-06-13
2013-06-13
2012-07-01
2013-06-14
Journal article
Dritschel , D G & Tobias , S 2012 , ' Two-dimensional magnetohydrodynamic turbulence in the small magnetic Prandtl number limit ' , Journal of Fluid Mechanics , vol. 703 , pp. 85-98 . https://doi.org/10.1017/jfm.2012.195
0022-1120
PURE: 23838294
PURE UUID: ae81c8fa-eff4-4a68-bc84-e0f604a7ce03
Scopus: 84865490696
ORCID: /0000-0001-6489-3395/work/64697743
http://hdl.handle.net/10023/3698
https://doi.org/10.1017/jfm.2012.195
eng
Journal of Fluid Mechanics
Copyright (c) Cambridge University Press 2012
oai:research-repository.st-andrews.ac.uk:10023/116182022-05-10T10:30:37Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Spatial variation in boundary conditions can govern selection and location of eyespots in butterfly wings
Venkataraman, Chandrasekhar
Sekimura, Toshio
Sekimura, Toshio
Nijhout, Frederik H.
University of St Andrews. Applied Mathematics
Butterfly patterning
Eyespot pattern
Focus point formation
Turing patterns
Reaction-diffusion system
Surface reaction-diffusion system
Surface finite element method
QA Mathematics
QH301 Biology
QP Physiology
Despite being the subject of widespread study, many aspects of the development of eyespot patterns in butterfly wings remain poorly understood. In this work, we examine, through numerical simulations, a mathematical model for eyespot focus point formation in which a reaction-diffusion system is assumed to play the role of the patterning mechanism. In the model, changes in the boundary conditions at the veins at the proximal boundary alone are capable of determining whether or not an eyespot focus forms in a given wing cell and the eventual position of focus points within the wing cell. Furthermore, an auxiliary surface reaction diffusion system posed along the entire proximal boundary of the wing cells is proposed as the mechanism that generates the necessary changes in the proximal boundary profiles. In order to illustrate the robustness of the model, we perform simulations on a curved wing geometry that is somewhat closer to a biological realistic domain than the rectangular wing cells previously considered, and we also illustrate the ability of the model to reproduce experimental results on artificial selection of eyespots.
2017-09-07
2017-09-07
2017
Book item
Venkataraman , C & Sekimura , T 2017 , Spatial variation in boundary conditions can govern selection and location of eyespots in butterfly wings . in T Sekimura & F H Nijhout (eds) , Diversity and Evolution of Butterfly Wing Patterns . 1 edn , 6 , Springer , Singapore , pp. 107-118 . https://doi.org/10.1007/978-981-10-4956-9_6
9789811049552
9789811049569
PURE: 250980176
PURE UUID: fc0aced2-23e6-4c90-bae5-6ab3a4ebf6cb
Scopus: 85036579347
http://hdl.handle.net/10023/11618
https://doi.org/10.1007/978-981-10-4956-9_6
eng
Diversity and Evolution of Butterfly Wing Patterns
© The Author(s) 2017. This chapter is licensed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. The images or other third party material in this chapter are included in the chapter’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the chapter’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.
Springer
oai:research-repository.st-andrews.ac.uk:10023/77112023-04-25T23:42:10Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Stochastic modelling of chromosomal segregation : errors can introduce correction
Matzavinos, Anastasios
Roitershtein, Alexander
Shtylla, Blerta
Voller, Zachary
Liu, Sijia
Chaplain, Mark A.J.
University of St Andrews. Applied Mathematics
QA Mathematics
QH301 Biology
SDG 3 - Good Health and Well-being
Cell division is a complex process requiring the cell to have many internal checks so that division may proceed and be completed correctly. Failure to divide correctly can have serious consequences, including progression to cancer. During mitosis, chromosomal segregation is one such process that is crucial for successful progression. Accurate segregation of chromosomes during mitosis requires regulation of the interactions between chromosomes and spindle microtubules. If left uncorrected, chromosome attachment errors can cause chromosome segregation defects which have serious effects on cell fates. In early prometaphase, where kinetochores are exposed to multiple microtubules originating from the two poles, there are frequent errors in kinetochore-microtubule attachment. Erroneous attachments are classified into two categories, syntelic and merotelic. In this paper, we consider a stochastic model for a possible function of syntelic and merotelic kinetochores, and we provide theoretical evidence that merotely can contribute to lessening the stochastic noise in the time for completion of the mitotic process in eukaryotic cells.
2015-10-29
2015-10-29
2014-07
Journal article
Matzavinos , A , Roitershtein , A , Shtylla , B , Voller , Z , Liu , S & Chaplain , M A J 2014 , ' Stochastic modelling of chromosomal segregation : errors can introduce correction ' , Bulletin of Mathematical Biology , vol. 76 , no. 7 , pp. 1590-1606 . https://doi.org/10.1007/s11538-014-9969-z
0092-8240
PURE: 206440000
PURE UUID: cff512c0-3db2-41cc-ba7c-910634d496a6
RIS: urn:3EB2FD717E63D38628264A85A6CD1F3F
Scopus: 84906943997
ORCID: /0000-0001-5727-2160/work/55378972
http://hdl.handle.net/10023/7711
https://doi.org/10.1007/s11538-014-9969-z
eng
Bulletin of Mathematical Biology
© 2014, Publisher / the Author(s). This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at link.springer.com / https://dx.doi.org/10.1007/s11538-014-9969-z
oai:research-repository.st-andrews.ac.uk:10023/102912022-04-05T15:31:36Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Hα and EUV observations of a partial CME
Christian, Damian J.
Jess, David B.
Antolin, Patrick
Mathioudakis, Mihalis
University of St Andrews. Applied Mathematics
Sun: chromosphere
Sun: corona
Sun: coronal mass ejections: CMEs
Sun: filaments
Prominences
QB Astronomy
QC Physics
NDAS
We have obtained Hα high spatial and time resolution observations of the upper solar chromosphere and supplemented these with multi-wavelength observations from the Solar Dynamics Observatory (SDO) and the Hinode Extreme-ultraviolet Imaging Spectrometer. The Hα observations were conducted on 2012 February 11 with the Hydrogen-Alpha Rapid Dynamics Camera instrument at the National Solar Observatory's Dunn Solar Telescope. Our Hα observations found large downflows of chromospheric material returning from coronal heights following a failed prominence eruption. We have detected several large condensations ("blobs") returning to the solar surface at velocities of ≈200 km s−1 in both Hα and several SDO Atmospheric Imaging Assembly band passes. The average derived size of these "blobs" in Hα is 500 by 3000 km2 in the directions perpendicular and parallel to the direction of travel, respectively. A comparison of our "blob" widths to those found from coronal rain, indicate that there are additional, smaller, unresolved "blobs" in agreement with previous studies and recent numerical simulations. Our observed velocities and decelerations of the "blobs" in both Hα and SDO bands are less than those expected for gravitational free-fall and imply additional magnetic or gas pressure impeding the flow. We derived a kinetic energy of ≈2 orders of magnitude lower for the main eruption than a typical coronal mass ejection, which may explain its partial nature.
2017-02-14
2017-02-14
2015-05-12
Journal article
Christian , D J , Jess , D B , Antolin , P & Mathioudakis , M 2015 , ' Hα and EUV observations of a partial CME ' , Astrophysical Journal , vol. 804 , 147 . https://doi.org/10.1088/0004-637X/804/2/147
0004-637X
PURE: 248969636
PURE UUID: 5db3e463-9420-40bc-bb65-f1fb79cd4585
BibCode: 2015ApJ...804..147C
Scopus: 84929996408
http://hdl.handle.net/10023/10291
https://doi.org/10.1088/0004-637X/804/2/147
http://adsabs.harvard.edu/abs/2015ApJ...804..147C
eng
Astrophysical Journal
© 2015 The American Astronomical Society. All rights reserved. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at: https://dx.doi.org/10.1088/0004-637X/804/2/147
oai:research-repository.st-andrews.ac.uk:10023/47622023-04-18T09:51:41Zcom_10023_92com_10023_28com_10023_792com_10023_39com_10023_879com_10023_878col_10023_96col_10023_795col_10023_880
Shallow-water vortex equilibria and their stability
Płotka, H.
Dritschel, D.G.
University of St Andrews. University of St Andrews
University of St Andrews. Applied Mathematics
University of St Andrews. Marine Alliance for Science & Technology Scotland
University of St Andrews. Scottish Oceans Institute
QA Mathematics
We first describe the equilibrium form and stability of steadily-rotating simply-connected vortex patches in the single-layer quasi-geostrophic model of geophysical fluid dynamics. This model, valid for rotating shallow-water flow in the limit of small Rossby and Froude numbers, has an intrinsic length scale L called the "Rossby deformation length" relating the strength of stratification to that of the background rotation rate. Specifically, L = c/f where c = √gH is a characteristic gravity-wave speed, g is gravity (or "reduced" gravity in a two-layer context where one layer is infinitely deep), H is the mean active layer depth, and f is the Coriolis frequency (here constant). We next introduce ageostrophic effects by using the full shallow-water model to generate what we call "quasi-equilibria". These equilibria are not strictly steady, but radiate such weak gravity waves that they are steady for all practical purposes. Through an artificial ramping procedure, we ramp up the potential vorticity anomaly of the fluid particles in our quasi-geostrophic equilibria to obtain shallow-water quasi-equilibria at finite Rossby number. We show a few examples of these states in this paper.
2014-05-12
2014-05-12
2011-01-01
Journal article
Płotka , H & Dritschel , D G 2011 , ' Shallow-water vortex equilibria and their stability ' , Journal of Physics: Conference Series , vol. 318 , no. Section 6 , 062019 . https://doi.org/10.1088/1742-6596/318/6/062019
1742-6588
PURE: 117826100
PURE UUID: 54e18963-aff1-4af9-b32d-0333b798bfb4
Scopus: 84856344196
ORCID: /0000-0001-6489-3395/work/64697727
http://hdl.handle.net/10023/4762
https://doi.org/10.1088/1742-6596/318/6/062019
http://www.scopus.com/inward/record.url?eid=2-s2.0-84856344196&partnerID=8YFLogxK
eng
Journal of Physics: Conference Series
© 2012 Plotka et al. This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 3.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited.
oai:research-repository.st-andrews.ac.uk:10023/89592023-04-18T10:03:44Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_859col_10023_880
Spontaneous reconnection at a separator current layer : I. Nature of the reconnection
E. H. Stevenson, Julie
E. Parnell, Clare
University of St Andrews. Applied Mathematics
University of St Andrews. School of Mathematics and Statistics
QB Astronomy
QC Physics
NDAS
BDC
R2C
Magnetic separators, which lie on the boundary between four topologically-distinct flux domains, are prime locations in three-dimensional magnetic fields for reconnection, especially in the magnetosphere between the planetary and interplanetary magnetic fields and also in the solar atmosphere. Little is known about the details of separator reconnection and so the aim of this paper, which is the first of two, is to study the properties of magnetic reconnection at a single separator. Three-dimensional, resistive magnetohydrodynamic numerical experiments are run to study separator reconnection starting from a magnetohydrostatic equilibrium which contains a twisted current layer along a single separator linking a pair of opposite-polarity null points. The resulting reconnection occurs in two phases. The first is short involving rapid reconnection in which the current at the separator is reduced by a factor of around 2.3. Most 75% of the magnetic energy is converted during this phase, via Ohmic dissipation, directly into internal energy, with just 0.1% going into kinetic energy. During this phase the reconnection occurs along most of the separator away from its ends (the nulls), but in an asymmetric manner which changes both spatially and temporally over time. The second phase is much longer and involves slow impulsive-bursty reconnection. Again Ohmic heating dominates over viscous damping. Here the reconnection occurs in small localized bursts at random anywhere along the separator.
2016-06-09
2016-06-09
2015-12
2016-06-10
Journal article
E. H. Stevenson , J & E. Parnell , C 2015 , ' Spontaneous reconnection at a separator current layer : I. Nature of the reconnection ' , Journal of Geophysical Research: Space Physics , vol. 120 , no. 12 , pp. 10334-10352 . https://doi.org/10.1002/2015JA021730
2169-9402
PURE: 225630555
PURE UUID: 8f1ddba5-4c44-4cba-97ed-410fd6f56d36
ArXiv: http://arxiv.org/abs/1509.07729v2
Scopus: 84956932603
ORCID: /0000-0002-5694-9069/work/73700740
WOS: 000369180200015
http://hdl.handle.net/10023/8959
https://doi.org/10.1002/2015JA021730
eng
Journal of Geophysical Research: Space Physics
© 2015, Publisher / the Author(s). This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at onlinelibrary.wiley.com / https://dx.doi.org/10.1002/2015JA021736
oai:research-repository.st-andrews.ac.uk:10023/40842024-03-02T00:43:00Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Magnetohydrodynamics dynamical relaxation of coronal magnetic fields : IV. 3D tilted nulls
Fuentes-Fernandez, Jorge
Parnell, Clare E.
Science & Technology Facilities Council
University of St Andrews. Applied Mathematics
astro-ph.SR
Magnetohydrodynamics (MHD)
Sun: corona
Sun: magnetic topology
Magnetic reconnection
QB Astronomy
In this paper we study current accumulations in 3D "tilted" nulls formed by a folding of the spine and fan. A non-zero component of current parallel to the fan is required such that the null's fan plane and spine are not perpendicular. Our aims are to provide valid magnetohydrostatic equilibria and to describe the current accumulations in various cases involving finite plasma pressure.To create our equilibrium current structures we use a full, non-resistive, magnetohydrodynamic (MHD) code so that no reconnection is allowed. A series of experiments are performed in which a perturbed 3D tilted null relaxes towards an equilibrium via real, viscous damping forces. Changes to the initial plasma pressure and to magnetic parameters are investigated systematically.An initially tilted fan is associated with a non-zero Lorentz force that drives the fan and spine to collapse towards each other, in a similar manner to the collapse of a 2D X-point. In the final equilibrium state for an initially radial null with only the current perpendicular to the spine, the current concentrates along the tilt axis of the fan and in a layer about the null point with a sharp peak at the null itself. The continued growth of this peak indicates that the system is in an asymptotic regime involving an infinite time singularity at the null. When the initial tilt disturbance (current perpendicular to the spine) is combined with a spiral-type disturbance (current parallel to the spine), the final current density concentrates in three regions: one on the fan along its tilt axis and two around the spine, above and below the fan. The increased area of current accumulation leads to a weakening of the singularity formed at the null. The 3D spine-fan collapse with generic current studied here provides the ideal setup for non-steady reconnection studies.
2013-10-16
2013-10-16
2013-09-12
Journal article
Fuentes-Fernandez , J & Parnell , C E 2013 , ' Magnetohydrodynamics dynamical relaxation of coronal magnetic fields : IV. 3D tilted nulls ' , Astronomy & Astrophysics , vol. 554 , A145 . https://doi.org/10.1051/0004-6361/201220346
0004-6361
ArXiv: http://arxiv.org/abs/1309.3019v1
ORCID: /0000-0002-5694-9069/work/73700753
https://hdl.handle.net/10023/4084
10.1051/0004-6361/201220346
ST/K000950/1
eng
Astronomy & Astrophysics
oai:research-repository.st-andrews.ac.uk:10023/52322023-04-18T09:53:11Zcom_10023_92com_10023_28com_10023_94com_10023_792com_10023_39com_10023_879com_10023_878col_10023_96col_10023_98col_10023_795col_10023_880
The effect of slip length on vortex rebound from a rigid boundary
Sutherland, D.
Macaskill, C.
Dritschel, D.G.
University of St Andrews. University of St Andrews
University of St Andrews. Pure Mathematics
University of St Andrews. Applied Mathematics
University of St Andrews. Marine Alliance for Science & Technology Scotland
University of St Andrews. Scottish Oceans Institute
QC Physics
The problem of a dipole incident normally on a rigid boundary, for moderate to large Reynolds numbers, has recently been treated numerically using a volume penalisation method by Nguyen van yen, Farge, and Schneider [Phys. Rev. Lett.106, 184502 (2011)]. Their results indicate that energy dissipating structures persist in the inviscid limit. They found that the use of penalisation methods intrinsically introduces some slip at the boundary wall, where the slip approaches zero as the Reynolds number goes to infinity, so reducing to the no-slip case in this limit. We study the same problem, for both no-slip and partial slip cases, using compact differences on a Chebyshev grid in the direction normal to the wall and Fourier methods in the direction along the wall. We find that for the no-slip case there is no indication of the persistence of energy dissipating structures in the limit as viscosity approaches zero and that this also holds for any fixed slip length. However, when the slip length is taken to vary inversely with Reynolds number then the results of Nguyen van yen et al. are regained. It therefore appears that the prediction that energy dissipating structures persist in the inviscid limit follows from the two limits of wall slip length going to zero, and viscosity going to zero, not being treated independently in their use of the volume penalisation method.
2014-08-25
2014-08-25
2013-09-23
Journal article
Sutherland , D , Macaskill , C & Dritschel , D G 2013 , ' The effect of slip length on vortex rebound from a rigid boundary ' , Physics of Fluids , vol. 25 , no. 9 , 093104 . https://doi.org/10.1063/1.4821774
1070-6631
PURE: 143238593
PURE UUID: 345d91b2-3bd8-4a8a-a9b0-19adebe4f74e
Scopus: 84885026819
ORCID: /0000-0001-6489-3395/work/64697799
http://hdl.handle.net/10023/5232
https://doi.org/10.1063/1.4821774
http://www.scopus.com/inward/record.url?eid=2-s2.0-84885026819&partnerID=8YFLogxK
eng
Physics of Fluids
© 2013 AIP Publishing LLC
oai:research-repository.st-andrews.ac.uk:10023/52332022-04-05T14:30:50Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_859col_10023_880
Resistive magnetohydrodynamic reconnection : resolving long-term, chaotic dynamics
Keppens, R.
Porth, O.
Galsgaard, K.
Frederiksen, J.T.
Restante, A.L.
Lapenta, G.
Parnell, C.
European Commission
University of St Andrews. School of Mathematics and Statistics
University of St Andrews. Applied Mathematics
QC Physics
We acknowledge financial support from the EC FP7/2007-2013 Grant Agreement SWIFF (No. 263340) and from project GOA/2009/009 (KU Leuven). This research has been funded by the Interuniversity Attraction Poles Programme initiated by the Belgian Science Policy Office (IAP P7/08 CHARM). Part of the simulations used the infrastructure of the VSC-Flemish Supercomputer Center, funded by the Hercules Foundation and the Flemish Government-Department EWI. Another part of the simulations was done at the former Danish Center for Scientific Computing at Copenhagen University which is now part of DeIC Danish e-Infrastructure Cooperation.
In this paper, we address the long-term evolution of an idealised double current system entering reconnection regimes where chaotic behavior plays a prominent role. Our aim is to quantify the energetics in high magnetic Reynolds number evolutions, enriched by secondary tearing events, multiple magnetic island coalescence, and compressive versus resistive heating scenarios. Our study will pay particular attention to the required numerical resolutions achievable by modern (grid-adaptive) computations, and comment on the challenge associated with resolving chaotic island formation and interaction. We will use shock-capturing, conservative, grid-adaptive simulations for investigating trends dominated by both physical (resistivity) and numerical (resolution) parameters, and confront them with (visco-)resistive magnetohydrodynamic simulations performed with very different, but equally widely used discretization schemes. This will allow us to comment on the obtained evolutions in a manner irrespective of the adopted discretization strategy. Our findings demonstrate that all schemes used (finite volume based shock-capturing, high order finite differences, and particle in cell-like methods) qualitatively agree on the various evolutionary stages, and that resistivity values of order 0.001 already can lead to chaotic island appearance. However, none of the methods exploited demonstrates convergence in the strong sense in these chaotic regimes. At the same time, nonperturbed tests for showing convergence over long time scales in ideal to resistive regimes are provided as well, where all methods are shown to agree. Both the advantages and disadvantages of specific discretizations as applied to this challenging problem are discussed.
2014-08-25
2014-08-25
2013-09-13
Journal article
Keppens , R , Porth , O , Galsgaard , K , Frederiksen , J T , Restante , A L , Lapenta , G & Parnell , C 2013 , ' Resistive magnetohydrodynamic reconnection : resolving long-term, chaotic dynamics ' , Physics of Plasmas , vol. 20 , no. 9 , 092109 . https://doi.org/10.1063/1.4820946
1070-664X
PURE: 143241697
PURE UUID: ce255d88-22a0-4f07-a2d5-579f5ad8ae2f
Scopus: 84885027542
ORCID: /0000-0002-5694-9069/work/73700718
http://hdl.handle.net/10023/5233
https://doi.org/10.1063/1.4820946
http://www.scopus.com/inward/record.url?eid=2-s2.0-84885027542&partnerID=8YFLogxK
263340
eng
Physics of Plasmas
© 2013 AIP Publishing LLC
oai:research-repository.st-andrews.ac.uk:10023/115432024-02-26T00:43:09Zcom_10023_92com_10023_28com_10023_196com_10023_39com_10023_879com_10023_878col_10023_96col_10023_197col_10023_859col_10023_880
Erwin Schrödinger and quantum wave mechanics
O'Connor, John J.
Robertson, Edmund F.
University of St Andrews. School of Mathematics and Statistics
University of St Andrews. Centre for Interdisciplinary Research in Computational Algebra
University of St Andrews. Applied Mathematics
QC Physics
T-NDAS
The fathers of matrix quantum mechanics believed that the quantum particles are unanschaulich (unvisualizable) and that quantum particles pop into existence only when we measure them. Challenging the orthodoxy, in 1926 Erwin Schrödinger developed his wave equation that describes the quantum particles as a packet of quantum probability amplitudes evolving in space and time. Thus, Schrödinger visualized the unvisualizable and lifted the veil that has been obscuring the wonders of the quantum world.
2017-08-25
2017-08-25
2017-08-22
Journal article
O'Connor , J J & Robertson , E F 2017 , ' Erwin Schrödinger and quantum wave mechanics ' , Quanta , vol. 6 , no. 1 , pp. 48-52 . https://doi.org/10.12743/quanta.v6i1.60
1314-7374
crossref: 10.12743/quanta.v6i1.60
https://hdl.handle.net/10023/11543
10.12743/quanta.v6i1.60
eng
Quanta
oai:research-repository.st-andrews.ac.uk:10023/90372023-04-18T10:10:49Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Solar cycle variation of magnetic flux ropes in a quasi-static coronal evolution model
Yeates, A. R.
Constable, J. A.
Martens, P. C. H.
Science & Technology Facilities Council
University of St Andrews. Applied Mathematics
Coronal mass ejections, theory
Magnetic fields, corona
Magnetic fields, models
Solar cycle, models
QB Astronomy
QC Physics
The structure of electric current and magnetic helicity in the solar corona is closely linked to solar activity over the 11-year cycle, yet is poorly understood. As an alternative to traditional current-free "potential field" extrapolations, we investigate a model for the global coronal magnetic field which is non-potential and time-dependent, following the build-up and transport of magnetic helicity due to flux emergence and large-scale photospheric motions. This helicity concentrates into twisted magnetic flux ropes, which may lose equilibrium and be ejected. Here, we consider how the magnetic structure predicted by this model-in particular the flux ropes-varies over the solar activity cycle, based on photospheric input data from six periods of cycle 23. The number of flux ropes doubles from minimum to maximum, following the total length of photospheric polarity inversion lines. However, the number of flux rope ejections increases by a factor of eight, following the emergence rate of active regions. This is broadly consistent with the observed cycle modulation of coronal mass ejections, although the actual rate of ejections in the simulation is about a fifth of the rate of observed events. The model predicts that, even at minimum, differential rotation will produce sheared, non-potential, magnetic structure at all latitudes.
2016-06-22
2016-06-22
2010-05
Journal article
Yeates , A R , Constable , J A & Martens , P C H 2010 , ' Solar cycle variation of magnetic flux ropes in a quasi-static coronal evolution model ' , Solar Physics , vol. 263 , no. 1 , pp. 121-134 . https://doi.org/10.1007/s11207-010-9546-z
0038-0938
PURE: 243585732
PURE UUID: e6a0abc3-6e02-4959-9edc-ff38fd5f170f
ArXiv: http://arxiv.org/abs/1003.4653v1
Scopus: 77951975057
http://hdl.handle.net/10023/9037
https://doi.org/10.1007/s11207-010-9546-z
ST/H008799
eng
Solar Physics
© 2010, Springer. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at link.springer.com / https://dx.doi.org/10.1007/s11207-010-9546-z
oai:research-repository.st-andrews.ac.uk:10023/96112022-04-22T15:30:20Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
The usage of a three-compartment model to investigate the metabolic differences between hepatic reductase null and wild-type mice
Hill, Lydia
Chaplain, Mark Andrew Joseph
Wolf, Roland
Kapelyukh, Yury
University of St Andrews. Applied Mathematics
cytochrome P450 enzymes
compartment models
hepatic reductase null mice
drug metabolism
QA Mathematics
RM Therapeutics. Pharmacology
NDAS
L.H. is currently funded by the Research Foundation Flanders (FWO) and the Belgian Science Policy Office under Grant No. IAP-VI/10.
The Cytochrome P450 (CYP) system is involved in 90% of the human body’s interactions with xenobiotics and due to this, it has become an area of avid research including the creation of transgenic mice. This paper proposes a three-compartment model which is used to explain the drug metabolism in the Hepatic Reductase Null (HRN) mouse developed by the University of Dundee (Henderson, C. J., Otto, D. M. E., Carrie, D., Magnuson, M. A., McLaren, A. W., Rosewell, I. and Wolf, C. R. (2003) Inactivation of the hepatic cytochrome p450 system by conditional deletion of hepatic cytochrome p450 reductase. J. Biol. Chem. 278, 13480–13486). The model is compared with a two-compartment model using experimental data from studies using wild-type and HRN mice. This comparison allowed for metabolic differences between the two types of mice to be isolated. The three sets of drug data (Gefitinib, Midazolam and Thalidomide) showed that the transgenic mouse has a decreased rate of metabolism.
2016-10-05
2016-10-05
2015-10-05
2016-10-05
Journal article
Hill , L , Chaplain , M A J , Wolf , R & Kapelyukh , Y 2015 , ' The usage of a three-compartment model to investigate the metabolic differences between hepatic reductase null and wild-type mice ' , Mathematical Medicine and Biology , vol. Advance Access . https://doi.org/10.1093/imammb/dqv029
1477-8602
PURE: 240466818
PURE UUID: 2a330f49-8a90-4a7f-8620-b8a8ed340980
Scopus: 85026692501
ORCID: /0000-0001-5727-2160/work/55379070
http://hdl.handle.net/10023/9611
https://doi.org/10.1093/imammb/dqv029
eng
Mathematical Medicine and Biology
© 2015, the Author(s). Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at http://imammb.oxfordjournals.org/content/early/2015/10/04/imammb.dqv029.full
oai:research-repository.st-andrews.ac.uk:10023/39782022-04-14T11:32:06Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Magnetohydrodynamics dynamical relaxation of coronal magnetic fields : III. 3D spiral nulls
Fuentes-Fernandez, Jorge
Parnell, Clare E.
University of St Andrews. Applied Mathematics
Magnetohydrodynamic (MHD)
Corona
Magnetic topology
Magnetic reconnection
QC Physics
Context: The majority of studies on stressed 3D magnetic null points consider magnetic reconnection driven by an external perturbation, but the formation of a genuine current sheet equilibrium remains poorly understood. This problem has been considered more extensively in two-dimensions, but lacks a generalization into 3D fields. Aims: 3D magnetic nulls are more complex than 2D nulls and the field can take a greater range of magnetic geometries local to the null. Here, we focus on one type and consider the dynamical non-resistive relaxation of 3D spiral nulls with initial spine-aligned current. We aim to provide a valid magnetohydrostatic equilibrium, and describe the electric current accumulations in various cases, involving a finite plasma pressure. Methods: A full MHD code is used, with the resistivity set to zero so that reconnection is not allowed, to run a series of experiments in which a perturbed spiral 3D null point is allowed to relax towards an equilibrium, via real, viscous damping forces. Changes to the initial plasma pressure and other magnetic parameters are investigated systematically. Results: For the axi-symmetric case, the evolution of the field and the plasma is such that it concentrates the current density in two cone-shaped regions along the spine, thus concentrating the twist of the magnetic field around the spine, leaving a radial configuration in the fan plane. The plasma pressure redistributes in order to maintain the current density accumulations. However, it is found that changes in the initial plasma pressure do not modify the final state significantly. In the cases where the initial magnetic field is not axi-symmetric, a infinite-time singularity of current perpendicular to the fan is found at the location of the null.
2013-08-22
2013-08-22
2012-06
Journal article
Fuentes-Fernandez , J & Parnell , C E 2012 , ' Magnetohydrodynamics dynamical relaxation of coronal magnetic fields : III. 3D spiral nulls ' , Astronomy & Astrophysics , vol. 544 , A77 . https://doi.org/10.1051/0004-6361/201219190
0004-6361
PURE: 66348475
PURE UUID: 9a71ccf9-43db-41f7-ab70-bd6d75044611
ArXiv: http://arxiv.org/abs/1206.5527v1
Scopus: 84864739472
ORCID: /0000-0002-5694-9069/work/73700737
http://hdl.handle.net/10023/3978
https://doi.org/10.1051/0004-6361/201219190
eng
Astronomy & Astrophysics
Copyright, ESO 2012.
oai:research-repository.st-andrews.ac.uk:10023/33972023-04-18T09:44:51Zcom_10023_92com_10023_28com_10023_792com_10023_39com_10023_879com_10023_878col_10023_96col_10023_795col_10023_880
Instability in internal solitary waves with trapped cores
Carr, Magda
King, Stuart Edward
Dritschel, David Gerard
EPSRC
University of St Andrews. Applied Mathematics
University of St Andrews. Scottish Oceans Institute
University of St Andrews. Marine Alliance for Science & Technology Scotland
Flow instability
Solitons
Stratified flow
Vortices
QA Mathematics
A numerical method that employs a combination of contour advection and pseudo-spectral techniques is used to investigate instability in internal solitary waves with trapped cores. A three-layer configuration for the background stratification in which the top two layers are linearly stratified and the lower layer is homogeneous is considered throughout. The strength of the stratification in the very top layer is chosen to be sufficient so that waves of depression with trapped cores can be generated. The flow is assumed to satisfy the Dubriel-Jacotin-Long equation both inside and outside of the core region. The Brunt-Vaisala frequency is modelled such that it varies from a constant value outside of the core to zero inside the core over a sharp but continuous transition length. This results in a stagnant core in which the vorticity is zero and the density is homogeneous and approximately equal to that at the core boundary. The time dependent simulations show that instability occurs on the boundary of the core. The instability takes the form of Kelvin-Helmholtz billows. If the instability in the vorticity field is energetic enough, disturbance in the buoyancy field is also seen and fluid exchange takes place across the core boundary. Occurrence of the Kelvin-Helmholtz billows is attributed to the sharp change in the vorticity field at the boundary between the core and the pycnocline. The numerical scheme is not limited by small Richardson number unlike the other alternatives currently available in the literature which appear to be.
2013-03-15
2013-03-15
2012-01
Journal article
Carr , M , King , S E & Dritschel , D G 2012 , ' Instability in internal solitary waves with trapped cores ' , Physics of Fluids , vol. 24 , no. 1 , 016601 . https://doi.org/10.1063/1.3673612
1070-6631
PURE: 17779963
PURE UUID: 577c5194-26c2-449e-ae1a-639c38c4e28a
Scopus: 84856437578
ORCID: /0000-0001-6489-3395/work/64697826
http://hdl.handle.net/10023/3397
https://doi.org/10.1063/1.3673612
EP/F030622/1
eng
Physics of Fluids
This is the author's version of this article. The published version © 2012 American Institute of Physics is available at http://link.aip.org/link/doi/10.1063/1.3673612
oai:research-repository.st-andrews.ac.uk:10023/116662022-05-05T15:30:29Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Wave of chaos in a spatial eco-epidemiological system : generating realistic patterns of patchiness in rabbit-lynx dynamics
Upadhyay, Ranjit
Roy, Parimita
Venkataraman, C.
Madzvamuse, Anotida
University of St Andrews. Applied Mathematics
Eco-epidemiological model
Bifurcation analysis
Diffusion-driven instability
Turing patterns
QA Mathematics
QH301 Biology
NDAS
AM and CV would like to acknowledge support from the Engineering and Physical Sciences Research Council grant (EP/J016780/1) and the Leverhulme Trust Research Project Grant (RPG-2014-149).
In the present paper, we propose and analyse an eco-epidemiological model with diffusion to study the dynamics of rabbit populations which are consumed by lynx populations. Existence, boundedness, stability and bifurcation analyses of solutions for the proposed rabbit-lynx model are performed. Results show that in the presence of diffusion the model has the potential of exhibiting Turing instability. Numerical results (finite difference and finite element methods) reveal the existence of the wave of chaos and this appears to be a dominant mode of disease dispersal. We also show the mechanism of spatiotemporal pattern formation resulting from the Hopf bifurcation analysis, which can be a potential candidate for understanding the complex spatiotemporal dynamics of eco-epidemiological systems. Implications of the asymptotic transmission rate on disease eradication among rabbit population which in turn enhances the survival of Iberian lynx are discussed.
2017-09-14
2017-09-14
2016-11
2017-09-14
Journal article
Upadhyay , R , Roy , P , Venkataraman , C & Madzvamuse , A 2016 , ' Wave of chaos in a spatial eco-epidemiological system : generating realistic patterns of patchiness in rabbit-lynx dynamics ' , Mathematical Biosciences , vol. 281 , pp. 98-119 . https://doi.org/10.1016/j.mbs.2016.08.014
0025-5564
PURE: 245646544
PURE UUID: 373997f8-2728-4091-8fbd-2fe02b50d770
Scopus: 84990188798
WOS: 000387191900011
http://hdl.handle.net/10023/11666
https://doi.org/10.1016/j.mbs.2016.08.014
eng
Mathematical Biosciences
© 2016, Elsevier. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at www.sciencedirect.com / https://dx.doi.org/10.1016/j.mbs.2016.08.014
oai:research-repository.st-andrews.ac.uk:10023/52362023-04-18T09:50:15Zcom_10023_92com_10023_28com_10023_792com_10023_39com_10023_879com_10023_878col_10023_96col_10023_795col_10023_880
Vortical control of forced two-dimensional turbulence
Fontane, Jerome Jacob Louis
Dritschel, David Gerard
Scott, Richard Kirkness
European Commission
University of St Andrews. Applied Mathematics
University of St Andrews. Marine Alliance for Science & Technology Scotland
University of St Andrews. Scottish Oceans Institute
Two-dimensional turbulence
QC Physics
Jérôme Fontane is supported by the European Community in the framework of the CONVECT project under Grant No. PIEF-GA-2008-221003.
A new numerical technique for the simulation of forced two-dimensional turbulence[D. Dritschel and J. Fontane, “The combined Lagrangian advection method,” J. Comput. Phys.229, 5408–5417 (Year: 2010)10.1016/j.jcp.2010.03.048] is used to examine the validity of Kraichnan-Batchelor scaling laws at higher Reynolds number than previously accessible with classical pseudo-spectral methods, making use of large simulation ensembles to allow a detailed consideration of the inverse cascade in a quasi-steady state. Our results support the recent finding of Scott [R. Scott, “Nonrobustness of the two-dimensional turbulent inverse cascade,” Phys. Rev. E75, 046301 (Year: 2007)10.1103/PhysRevE.75.046301], namely that when a direct enstrophy cascading range is well-represented numerically, a steeper energy spectrum proportional to k−2 is obtained in place of the classical k −5/3 prediction. It is further shown that this steep spectrum is associated with a faster growth of energy at large scales, scaling like t −1 rather than Kraichnan's prediction of t −3/2. The deviation from Kraichnan's theory is related to the emergence of a population of vortices that dominate the distribution of energy across scales, and whose number density and vorticity distribution with respect to vortex area are related to the shape of the enstrophy spectrum. An analytical model is proposed which closely matches the numerical spectra between the large scales and the forcing scale.
2014-08-25
2014-08-25
2013-01-14
Journal article
Fontane , J J L , Dritschel , D G & Scott , R K 2013 , ' Vortical control of forced two-dimensional turbulence ' , Physics of Fluids , vol. 25 , no. 1 , 015101 . https://doi.org/10.1063/1.4774336
1070-6631
PURE: 93444500
PURE UUID: ccb8d4a8-0c81-4599-8969-3d1294da867a
Scopus: 84873438755
ORCID: /0000-0001-5624-5128/work/55378711
ORCID: /0000-0001-6489-3395/work/64697779
http://hdl.handle.net/10023/5236
https://doi.org/10.1063/1.4774336
http://dx.doi.org/10.1063/1.4774336
PIEF-GA-2008-221003
eng
Physics of Fluids
© 2013 American Institute of Physics
oai:research-repository.st-andrews.ac.uk:10023/102822022-04-06T15:32:05Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Detection of supersonic downflows and associated heating events in the transition region above sunspots
Kleint, L.
Antolin, P.
Tian, H.
Judge, P.
Testa, P.
De Pontieu, B.
Martínez-Sykora, J.
Reeves, K. K.
Wuelser, J. P.
McKillop, S.
Saar, S.
Carlsson, M.
Boerner, P.
Hurlburt, N.
Lemen, J.
Tarbell, T. D.
Title, A.
Golub, L.
Hansteen, V.
Jaeggli, S.
Kankelborg, C.
University of St Andrews. Applied Mathematics
Sun: transition region
Sunspots
QB Astronomy
QC Physics
Interface Region Imaging Spectrograph data allow us to study the solar transition region (TR) with an unprecedented spatial resolution of 0″33. On 2013 August 30, we observed bursts of high Doppler shifts suggesting strong supersonic downflows of up to 200 km s–1 and weaker, slightly slower upflows in the spectral lines Mg II h and k, C II 1336, Si IV 1394 Å, and 1403 Å, that are correlated with brightenings in the slitjaw images (SJIs). The bursty behavior lasts throughout the 2 hr observation, with average burst durations of about 20 s. The locations of these short-lived events appear to be the umbral and penumbral footpoints of EUV loops. Fast apparent downflows are observed along these loops in the SJIs and in the Atmospheric Imaging Assembly, suggesting that the loops are thermally unstable. We interpret the observations as cool material falling from coronal heights, and especially coronal rain produced along the thermally unstable loops, which leads to an increase of intensity at the loop footpoints, probably indicating an increase of density and temperature in the TR. The rain speeds are on the higher end of previously reported speeds for this phenomenon, and possibly higher than the free-fall velocity along the loops. On other observing days, similar bright dots are sometimes aligned into ribbons, resembling small flare ribbons. These observations provide a first insight into small-scale heating events in sunspots in the TR.
2017-02-13
2017-02-13
2014-06-27
Journal article
Kleint , L , Antolin , P , Tian , H , Judge , P , Testa , P , De Pontieu , B , Martínez-Sykora , J , Reeves , K K , Wuelser , J P , McKillop , S , Saar , S , Carlsson , M , Boerner , P , Hurlburt , N , Lemen , J , Tarbell , T D , Title , A , Golub , L , Hansteen , V , Jaeggli , S & Kankelborg , C 2014 , ' Detection of supersonic downflows and associated heating events in the transition region above sunspots ' , Astrophysical Journal Letters , vol. 789 , no. 2 , L42 . https://doi.org/10.1088/2041-8205/789/2/L42
2041-8205
PURE: 248969928
PURE UUID: 62a0ecf5-5e44-463a-bd98-b3ca01a53025
BibCode: 2014ApJ...789L..42K
Scopus: 84903955110
http://hdl.handle.net/10023/10282
https://doi.org/10.1088/2041-8205/789/2/L42
http://adsabs.harvard.edu/abs/2014ApJ...789L..42K
eng
Astrophysical Journal Letters
© 2014. The American Astronomical Society. All rights reserved. This work is made available online in accordance with the publisher’s policies. This is the final published version of the work, which was originally published at: https://dx.doi.org/10.1088/2041-8205/789/2/L42
oai:research-repository.st-andrews.ac.uk:10023/94262022-04-08T15:30:35Zcom_10023_92com_10023_28com_10023_879com_10023_878col_10023_96col_10023_880
Study of the three-dimensional shape and dynamics of coronal loops observed by Hinode/EIS
Syntelis, P.
Gontikakis, C.
Georgoulis, M. K.
Alissandrakis, C. E.
Tsinganos, K.
University of St Andrews. Applied Mathematics
Active regions
Structure
Velocity field
Magnetic fields
QB Astronomy
QC Physics
We study plasma flows along selected coronal loops in NOAA Active Region 10926, observed on 3 December 2006 with Hinode’sEUVImaging Spectrograph (EIS). From the shape of the loops traced on intensity images and the Doppler shifts measured along their length we compute their three-dimensional (3D) shape and plasma flow velocity using a simple geometrical model. This calculation was performed for loops visible in the Fe viii 185 Å, Fe x 184 Å, Fe xii 195 Å, Fe xiii202 Å, and Fe xv 284 Å spectral lines. In most cases the flow is unidirectional from one footpoint to the other but there are also cases of draining motions from the top of the loops to their footpoints. Our results indicate that the same loop may show different flow patterns when observed in different spectral lines, suggesting a dynamically complex rather than a monolithic structure. We have also carried out magnetic extrapolations in the linear force-free field approximation using SOHO/MDI magnetograms, aiming toward a first-order identification of extrapolated magnetic field lines corresponding to the reconstructed loops. In all cases, the best-fit extrapolated lines exhibit left-handed twist (α<0), in agreement with the dominant twist of the region.
2016-09-05
2016-09-05
2012-10
Journal article
Syntelis , P , Gontikakis , C , Georgoulis , M K , Alissandrakis , C E & Tsinganos , K 2012 , ' Study of the three-dimensional shape and dynamics of coronal loops observed by Hinode /EIS ' , Solar Physics , vol. 280 , no. 2 , pp. 475-489 . https://doi.org/10.1007/s11207-012-0026-5
0038-0938
PURE: 245502797
PURE UUID: 66de5129-231c-4827-9486-6ea85f64db8a
BibCode: 2012SoPh..280..475S
Scopus: 84867520639
ORCID: /0000-0002-6377-0243/work/77131793
http://hdl.handle.net/10023/9426
https://doi.org/10.1007/s11207-012-0026-5
http://adsabs.harvard.edu/abs/2012SoPh..280..475S
eng
Solar Physics
© 2012, Springer. This work is made available online in accordance with the publisher’s policies. This is the author created, accepted version manuscript following peer review and may differ slightly from the final published version. The final published version of this work is available at link.springer.com / https://dx.doi.org/10.1007/s11207-012-0026-5
oai:research-repository.st-andrews.ac.uk:10023/43312023-04-18T09:40:38Zcom_10023_92com_10023_28com_10023_792com_10023_39com_10023_879com_10023_878col_10023_96col_10023_795col_10023_880
Boundary layer flow beneath an internal solitary wave of elevation
Carr, Magda
Davies, P A
University of St Andrews. Applied Mathematics
University of St Andrews. Scottish Oceans Institute
Rotating flows
Flow instabilities
Internal waves
Ocean waves
Reynolds stress modeling
The wave-induced flow over a fixed bottom boundary beneath an internal solitary wave of elevation propagating in an unsheared, two-layer, stably stratified fluid is investigated experimentally. Measurements of the velocity field close to the bottom boundary are presented to illustrate that in the lower layer the fluid velocity near the bottom reverses direction as the wave decelerates while higher in the water column the fluid velocity is in the same direction as the wave propagation. The observation is similar in nature to that for wave-induced flow beneath a surface solitary wave. Contrary to theoretical predictions for internal solitary waves, no evidence for either boundary layer separation or vortex formation is found beneath the front half of the wave in the adverse pressure gradient region of the flow.
2014-01-09
2014-01-09
2010-02
Journal article
Carr , M & Davies , P A 2010 , ' Boundary layer flow beneath an internal solitary wave of elevation ' , Physics of Fluids , vol. 22 , no. 2 , 026601 . https://doi.org/10.1063/1.3327289
1070-6631
PURE: 471128
PURE UUID: ac2c693b-5133-400d-9e07-8041f27c263c
standrews_research_output: 32388
Scopus: 77949327354
http://hdl.handle.net/10023/4331
https://doi.org/10.1063/1.3327289
http://www.scopus.com/inward/record.url?scp=77949327354&partnerID=8YFLogxK
eng
Physics of Fluids
Copyright 2010, American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Fluids, Vol 22, Issue 2, and may be found at: http://scitation.aip.org/content/aip/journal/pof2/22/2/10.1063/1.3327289