daily real-time MHD simulation of global solar corona and solar wind

[ Gallery contents ] [ Publication/Presentation ] [ Daily real-time coronal MHD simulation ]

[ Japanese version of this page ] [ daily-update prediction of total eclipse (July 22, 2009) ]

The real-time Sun, the global solar corona and solar wind
derived with time-dependent three-dimensional MHD simulation
using daily-updated SOHO/MDI magnetic field synoptic data

Please visit the SOI website for information about MDI magnetogram.
Simulation with choice O
The density and temperature are fixed at the base of the open-field coronal hole. The plots are usually replaced with new ones around 5AM (Pacific Time) every day.

lat-lon map at various distances click here to enlarge.	line-of-sight integration of coronal density

java applet animation : recent 27 plots	recent 27 plots
flow speed and magnetic field at 30 Rs in csv (plain text) format Vr (in km/s) and Br (in nT) Please contact us for details of the simulation and data. volume data of 8 MHD variables, from 1.01Rs to 5.01Rs* click here (gzipped plain text, but 20Mb or more) latitude-longitude maps, since Feb. 08, 2008. : CR2090, CR2089, CR2088, CR2087, CR2086, CR2085, ~~CR2084, CR2083, CR2082, CR2081, CR2080, CR2079, CR2078~~ ~~CR2077, CR2076, CR2075, CR2074, CR2073, CR2072,~~ ~~CR2071, CR2070, CR2069, CR2068, (part of) CR2067~~ 2008 Feb. 08∼29 (simulated without polar field correction). * Carrington numbers here are approximated (based on the date the simulation was conducted). mpeg movies combining plots part of 2008 (CR2067 to 2077+) latitude-longitude maps (8.3MB), LoS-integration of coronal density (1.5MB) first half of 2009 (approx. CR2078 to 2084) latitude-longitude maps (4.6MB), LoS-integration of density and base of open/closed field (1.0MB)

Observations / Measurements SOHO's corresponding images (taken two days before the simulations).

Simulations with other choices of boundary treatment (c.f. Hayashi (2005) ApJS vol. 161 pp. 480)
The daily quasi-real-time simulation shown above assumes fixed density and temperature at the coronal hole base (labeled choice O in my paper (2005)). The plot(s) below show the simulation results with other choices.

With choice AB'
Density and bulk velocity at the base of the coronal hole can vary under the constraints; the fixed temperature and the limited mass flux. The new plots are usually made 7AM (Pacific Time) every day.


recent 27 plots	recent 27 plots
flow speed and magnetic field at 30 Rs in csv (plain text) format Vr (in km/s) and Br (in nT) latitude-longitude maps, CR2073∼ : CR2090, CR2089, CR2088, CR2087, CR2086, CR2085, ~~CR2084, CR2083, CR2082, CR2081, CR2080, CR2079, CR2078~~ ~~CR2077, CR2076, CR2075, CR2074, CR2073, CR2072~~ mpeg movies combining plots part of 2008 (CR2072 to 2077+) latitude-longitude maps (6.4MB), LoS-integration of density and base of open/closed field (1.4MB) first half of 2009 (approx. CR2078 to 2084) latitude-longitude maps (4.6MB), LoS-integration of density and base of open/closed field (1.0MB)

With choice A
Density, temperature and bulk velocity at the base of the coronal hole can vary under the constraints; the fixed specific enthalpy and the limited mass flux. The new plots are usually made 7AM (Pacific Time) every day. *) The corona simulated with choice A may not be sufficiently time-relaxed: This choice allows the boundary coronal-hole temperature to decrease, resulting in the slower solar wind and time-relaxation process.


recent 27 plots	recent 27 plots
flow speed and magnetic field at 30 Rs in csv (plain text) format Vr (in km/s) and Br (in nT) latitude-longitude maps, CR2069∼ : CR2090, CR2089, CR2088, CR2087, CR2086, CR2085, ~~CR2084, CR2083, CR2082, CR2081, CR2080, CR2079, CR2078~~ ~~CR2077, CR2076, CR2075, CR2074, CR2073, CR2072,~~ ~~CR2071, CR2070, CR2069~~ mpeg movies combining plots part of 2008 (CR2069 to 2077+) latitude-longitude maps (6.4MB), LoS-integration of density and base of open/closed field (1.4MB) first half of 2009 (approx. CR2078 to 2084) latitude-longitude maps (4.6MB), LoS-integration of density and base of open/closed field (1.0MB)

Modification / change / history

2009 ∼ : no major changes so far
July 1, 2008 : Newkirk filter and other modifications are applied to synthetic LoS images for choice O.
June 15 : Newkirk filter and other modifications are applied to synthetic LoS images for choice A and AB'.
May 11 : This page starts.
May 1 : Simulations with boundary treatment choice A and AB' are started.
April 21 : Test plots of line-of-sight coronal density integration are added.
March 1 : Polar field correction is introduced.
Feb. 8, 2008 : Daily simulation starts.

Description

general :
The simulation is scheduled to start 1 AM Pacific Time. It usually takes about 6 hours (in wall clock time, depending on the computational choices such as the boundary treatment and the computation resources available) to conduct this near real-time MHD solution. New plots may appear around 7 AM (P.T.) at earliest.
data input :
The simulation uses the EOF (Experiment Operations Facility) version of SOHO/MDI solar surface magnetic field synoptic data so that the recent state of the corona can be determined. The EOF magnetic field map is regularly updated using the measurement data made 24 hours prior, and the dashed rectangle in the plots above approximately shows the Earth-side heliographic region in which the data is updated.
The simulation script uses "wget" command to get the magnetic field data that is located at the web-accessible place above, and, for sake of maintaining the regular basis, uses the second newest synoptic data that contains the measurement data from 24 hours to 28 days prior to the start time of the simulation.
polar field correction :
Because of variety of factors such as the apparent inclination of the solar rotation axis, the measurement of the polar field is generally of low quality. The polar field correction is needed to to enhance studies on the solar corona and solar wind.
Our correction is based on those proposed and tested by Liu, Y. and is implemented with great helps and assists by Sun, X. The correction is based on the spline extrapolation with respect to both time and space. This strategy works pretty well, at least today at the minimum phase of the solar activity, as the differences between results with and without the correction are significant.
initial and boundary values of magnetic field :
The boundary value and the three-dimensional initial value of the magnetic field are then calculated with the potential-field source-surface (PFSS) model. In this daily simulation, the spherical harmonics decomposition is used in the PFSS model, and the polynomial up to 5th order is used to give the initial and boundary values.
MHD simulation :
To obtain the steady state of the sub/trans-alfvénic solar corona, the time-dependent three-dimensional MHD simulation is conducted. The simulation scheme here is based on the Lax-Friedrichs method that is a simplified version of the TVD Roe/Godunov method; the Lax-Friedrichs method is much much faster than the Roe/Godunov method. The number of grids are 72, 32 and 64 for the radial, latitudinal and longitudinal direction, respectively. The inner boundary of the simulation is set at 1.01 solar radii, so that we will handle the coronal plasma already heated up to the order of 1 MK though the solar transition region. The daily MHD simulation will solve the time-relaxation process of the sub/trans-alfvénic solar corona over 40 hours.
   The boundary values of the eight MHD variables at this height are controlled by using the normal projected characteristics method, so that the obtained time-relaxed solution can be fully consistent with the given boundary map, the basic nonlinear hyperbolic MHD equations, and the concept of the characteristics. This is a quite capable mathematical method applicable to any computation scheme; this method re-distribute the calculated temporal derivatives in accordance with the given constraints and the direction of the characteristics curvature. In this method, all three components of plasma flow and the two tangential components of magnetic field can vary in accordance with the concept of the characteristics. The radial component of surface magnetic field is fixed all through the computation with any choices above.
   Some choices are selected and used in the daily MHD simulations to treat the open field region (coronal hole). The choices other than O limit the mass flux at the coronal hole base. For the closed-field region (base of coronal streamer), the plasma density and temperature can vary responding to the plasma precipitation from the stagnant closed field regions. Whether the plasma will be flowing outward or stagnant is determined by the simulated nonlinear interaction with the magnetic field, thus small or weak closed-field can be open up to the interplanetary space.
   The polytrope plasma with specific heat ratio of 1.05 is assumed to mimic the near-isothermal coronal situation due to the high thermal conduction. This assumption yields somehow small contrast in flow speed and density, and the absolute values of plasma (velocity and density) are less realistic. However, the magnetic field quantities and the trends of these plasma variables would be well retrieved. Because of the simplicity, we assumed the polytrope. Note that the specific enthalpy is a conservative quantities along the stream and that the values differ from place to place.

Last major modification: July 25, 2009
K. Hayashi

The real-time Sun, the global solar corona and solar wind derived with time-dependent three-dimensional MHD simulation using daily-updated SOHO/MDI magnetic field synoptic data

The real-time Sun, the global solar corona and solar wind
derived with time-dependent three-dimensional MHD simulation
using daily-updated SOHO/MDI magnetic field synoptic data