Changes between Version 35 and Version 36 of AstroBearProjects/resistiveMHD


Ignore:
Timestamp:
01/07/14 19:44:03 (11 years ago)
Author:
Shule Li
Comment:

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  • AstroBearProjects/resistiveMHD

    v35 v36  
    2929centered on the cell faces. Its curl therefore reside on the cell edges. Here is an example on calculating the diffusive current on the x direction, notice [[BR]]
    3030that the red arrow is where we are calculating the diffusive current, the green arrows are where the magnetic field originally resides: [[BR]]
    31 [[Image(resistive_diagram.png, 20%)]] [[BR]]
    32 [[Image(http://www.pas.rochester.edu/~shuleli/res_dia1.png, 20%)]] [[BR]]
     31[[Image(resistive_diagram.png, 20%)]][[Image(http://www.pas.rochester.edu/~shuleli/res_dia1.png, 20%)]] [[BR]]
    3332The actual code looks like the following in 2D (jy are initialized to 1): [[BR]]
    3433{{{
     
    112111where [[latex($\rho_0 = 1$)]] and [[latex($a = 0.5$)]]. The temperature is set to be constant as 0.5. [[BR]]
    113112The domain is set to be -6.4 < x < 6.4 and -12.8< y < 12.8, with fixed resolution 480 * 960. The boundaries are all open. The initial profile is plotted below: [[BR]]
    114 [[Image(http://www.pas.rochester.edu/~shuleli/hhc_plot.png, 20%)]][[BR]][[BR]]
     113[[Image(http://www.pas.rochester.edu/~shuleli/hhc_plot.png, 30%)]][[BR]][[BR]]
    115114The initial state is in pressure equilibrium though unstable. There are two ways to generate instabilities. The first way is to artificially increase the resistivity [[BR]]
    116115at the center of the domain. This increase will result in a higher reconnectivity, which will eventually bend magnetic field. This creates an X point where field [[BR]]
     
    118117to the direction of the sheer pinch. The box surrounding the X point where the outflows (Petschek shock) come out of is called the "Sweet-Parker Box". The following [[BR]]
    119118diagrams show how increased resistivity at the center of a sheer pinch drives Petschek shock.[[BR]]
    120 [[Image(http://www.pas.rochester.edu/~shuleli/multi_test/resistive_instab.png,20%)]] [[Image(http://www.pas.rochester.edu/~shuleli/hhc_flowpattern.png, 20%)]] [[BR]][[BR]]
     119[[Image(http://www.pas.rochester.edu/~shuleli/multi_test/resistive_instab.png,30%)]] [[Image(http://www.pas.rochester.edu/~shuleli/hhc_flowpattern.png, 30%)]] [[BR]][[BR]]
    121120The Mach number in 2D case is plotted in pseudo-color: [[BR]]
    122 [[Image(http://www.pas.rochester.edu/~shuleli/hhc_mach.png, 20%)]][[BR]][[BR]]
     121[[Image(http://www.pas.rochester.edu/~shuleli/hhc_mach.png, 30%)]][[BR]][[BR]]
    123122
    124123To test Sweet-Parker problem in AstroBEAR, we construct the sheer pinch using the above setup, and modify the resistivity at the center of the simulation box. [[BR]][[BR]]
     
    126125The following figure shows the Petschek shock from a reconnection spot at the center. Colored variable is the kinetic energy in log scale, magnetic field is illustrated [[BR]]
    127126by white lines. [[BR]]
    128 [[Image(http://www.pas.rochester.edu/~shuleli/multi_test/sp1_0020.png, 20%)]]
     127[[Image(http://www.pas.rochester.edu/~shuleli/multi_test/sp1_0020.png, 30%)]]
    129128[[BR]]
    130129A movie with 2-level AMR:[[BR]]
     
    139138of pressure imbalance, which creates periodical dense "islands".The growth rate and the size of the "islands" depend on resistivity and the strength of the perturbation.[[BR]][[BR]]
    140139
    141 [[Image(http://www.pas.rochester.edu/~shuleli/multi_test/mihr_0180.png,20%)]][[BR]][[BR]]
     140[[Image(http://www.pas.rochester.edu/~shuleli/multi_test/mihr_0180.png, 30%)]][[BR]][[BR]]
    142141
    143142To watch a full movie, [http://www.pas.rochester.edu/~shuleli/multi_test/mihr.gif click here][[BR]][[BR]]
     
    158157
    159158where T is the electron temperature in eV, Zeff is the effective ion charge.The Coulomb logarithm for interested number density is plotted below: [[BR]]
    160 [[Image(http://www.pas.rochester.edu/~shuleli/CoulombLog.png, 20%)]][[BR]]
     159[[Image(http://www.pas.rochester.edu/~shuleli/CoulombLog.png, 30%)]][[BR]]
    161160[[BR]][[BR]]
    162161