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Some progress on ‘linking together’ models

Nick AchilleosLecturer, Department of Physics

University College LondonWith thanks to Patrick Guio and Dugan Witherick

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Report from UCLWe have been pursuing activities which may produce some

useful ‘demonstrators’ and deliverables for the JRA3 Distributed Modelling Laboratory.

Modelling auroral dynamics at Jupiter (PhD project by J. N. Yates)

Coupling UCL Jovian magnetodisc model with a model of plasma flow (Achilleos, Guio)

Other possibilities ?

http://europlanet-ri.euAuroral Dynamics at Jupiter

• Model 1

- The UCL global, axisymmetric model of Jupiter’s thermosphere and ionosphere (e.g. Smith and Aylward, Ann. Geo., 2009).

- Solves equations of fluid flow for the neutral thermosphere.

- Needs an algorithm for computing ionospheric current, esp. in the auroral region.

- Uses Model 2: the theoretical profile by Grodent and Gerard (JGR 2001) for auroral ionosphere (ion density versus altitude)

http://europlanet-ri.euModel Linkage

• Architecture: Auroral profile is built into a subroutine of UCL code

UCL model reads auroral profile as a ‘template’ for auroral ionosphere

The ion density profile is scaled at all altitudes by the same factor, according to the conductance properties calculated by the disc dynamics routine - gives plasma rotation rate and corresponding M-I currents.

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• For more information, see paper submitted to PSS by Yates, Achilleos and Guio (2010, arxiv)

• Grodent / Gerard profile (ascii files?) may be added to JRA3 Catalogue

• We need more 1D theoretical profiles of auroral structure so that we may use the UCL Jovian and Kronian models as a ‘testbed’ - this should be emphasised as a useful goal of the DNML.

• Note also the work of Nicholson et al (MNRAS 2009) on precipitation at Mars, UCL are working on taking this further to a coupled model of Martian thermosphere and aurora.

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Example 1: UCL Magnetodisc model

What is it ? A model which calculates self-consistent magnetic field structure and plasma distributions for a `disc-like’, axisymmetric, rotating magnetosphere. Used for studies of magnetospheric structure at Saturn and Jupiter (giant rapid rotators) e.g. Achilleos, Guio and Arridge (MNRAS, 2010), Achilleos et al (GRL, 2010)

Giant Planet Magnetospheres

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• Present disc model assumes a fixed profile of plasma rotation (angular velocity M) versus radial distance.

• New configuration couples disc B-field model to an independent solver of plasma M

UCL Magnetodisc Model

M Solver

B Field Profile in Plasmadisc

M profile needed to

update force balance, re-compute B Field

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• New configuration links two independent Matlab codes on different nodes in a local network through a simple Java class using IP Sockets.• We could do a similar exercise for the magnetopause field model - at present we use average value from the formulae of Alexeev et al (Ann. Geo. 2005) (Catalogue entry ?)

UCL Magnetodisc Model

M Solver

B Field Profile in Plasmadisc

M profile needed to

update force balance, re-compute B Field

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A reminder of what JRA3 activities may foster in the long term:My feeling is that these are beyond the scope of Europlanet (not enough resource) but they may

indicate ‘where we are headed’ if we follow some of the more simple ideas.

Example A: A time-dependent MHD model of Jovian or Kronian plasmadisc to couple to the appropriate atmospheric GCMs, to study transient auroral response.

Example B: A time- and space-dependent model of auroral precipitation associated with the Io-Jupiter ‘current circuit’, to investigate the nature of wind systems driven by such a localised source of auroral energy input.

10JRA3 Workshop @ UCL: 22-24/04/2010

Progress on Catalogue-Linked Web Apps:• These are: (1) The H3+ cooling function calculator (code from S. Miller) (2) The VoiSe image segmentation tool (code from P. Guio)• These applications are being migrated to a new web server, we will notify the JRA3 team once this is complete (thanks to Dugan!)• URLs for web servers from UCL and other institutes could be inserted into JRA3 catalogue.

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Next steps? Action for all JRA3 Modellers: Think about whose work is relevant to what you are doing. Are they a

catalogue entry ? If yes, ok. If not, they should be. For the UCL work, we are interested in ‘testing’ 1D auroral models using a 3D global circulation model. There may also be a possibility that we could provide force-balance models for theoretical models of exoplanet plasmadiscs (e.g. work by Khodachenko et al)

Keep it simple, keep it realistic Modellers should compile a realistic ’wish list’ of model links for discussion. Is your desired algorithm /

model in the catalogue ? If no, could its owner’s contact details be placed in the catalogue ? From our meetings, it is clearer that IDIS ideally would provide a variety of databases which could be

queried - keep this in mind, and keep informed of IDIS progress.

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Next steps? Action for all JRA3 Modellers: Think about whose work is relevant to what

you are doing. Are they a catalogue entry ? Write down your thoughts and we could use this as a basis for a workshop at

UCL (April / May timescale ??)