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Magnetospheric regions automatic identification with AMDA and TOPCAT

Change Log [Science Use Case](#Science Use Case)


V. Génot , October 2012 , V2

Change Log

Science Use Case

  • Based on Jelinek et al., JGR 2012 (paper1)
  • Uses AMDA for the analysis
  • Uses TOPCAT for visualisations
  • Uses IVOA SAMP to exchange data between AMDA and TOPCAT


  • Reproduce two papers results in a few steps

    • Identify solar wind / magnetosheah / magnetosphere
    • Identify bow shock and magnetopause
  • Explore AMDA/TOPCAT enhanced functionalities

    • AMDA conditional parameters
    • TOPCAT weighted density maps
  • Propose new research perspectives


Magnetospheric region identification in Paper1


THEMIS A magnetospheric sampling over ~3 years


Magnetospheric regions
In both cases, the bin/contour represents the number of events
Jelinek et al., JGR 2012


Magnetospheric Regions


Bow shock and magnetopause identification


In both case, each bin represents the probability (less than 1) for this location to be in the magnetosheath
In TOPCAT this is automatically computed from the flag_msh values
Jelinek et al., JGR 2012

Step by step AMDA TOPCAT analysis

Magnetospheric region identification

  • define rB and rn in AMDA (create new parameters, see slide for exact definition)
    • time delay between ACE and THEMIS A is taken constant
    • for instance : shift(param,4000) shifts ACE data from 4000s forward
    • here : param=BACE or nACE
    • a better approach would use (see plot) : T=|XACE-XTHEMIS_A|/VSW
    • a much better approach would use an iterative algorithm to compute T
    • for instance see
  • launch TOPCAT ; it automatically opens a SAMP hub
  • in AMDA click interoperability and open a SAMP connection
  • download rB and rn on 2007/03/01 to 2009/10/01 at 60s resolution (all in one file)
  • in AMDA : in the Download Results window choose Send to TOPCAT
  • the table is automatically loaded in TOPCAT
  • choose density map (2D histogram) : rB function of rn
  • adjust binning and plotting range as necessary (0-8 for rn, 0-22 for rB)
  • do not worry about NaN values !

Bow shock and magnetopause identification; Use of AMDA conditional parameters

  • define the solar wind ram pressure pSW shifted to THEMIS A
    • time delay may be taken as 4000s as before
    • pSW=1.67e-6nACEVACE^2
  • produce a time table T1 when the pSW values are in a restricted band (ex: pSW<4)
  • define a new (conditional) parameter : flag_msh
    • flag_msh=1 if rB greater than 4-rn and rB lower than 10rn (see plot), else 0 (for solar wind and magnetosphere)
  • download XTHA, sqrt(YTHA^2+ZTHA^2), flag_msh at 3600 s resolution (all in one file) for the above T1 time table

Transfer via SAMP (same procedure as before)

  • the table is loaded into TOPCAT
  • choose density map (2D histogram) :
    • sqrt(Y^2+Z^2) function of X weighted by flag_msh
  • adjust binning as necessary

Parameter definition in AMDA

r_n = n_i_tha/shiftT_(sw(0),4000)  
r_b = bs_tha(3)/shiftT_(imf(3),4000)  
p_sw = shiftT_(sw(0)*sw(1)*sw(1),4000)*1.67e-6
flag_msh = (n_i_tha/shiftT_(sw(0),4000)+bs_tha(3)/shiftT_(imf(3),4000) > 4.) & (bs_tha(3)/shiftT_(imf(3),4000) - 10.*n_i_tha/shiftT_(sw(0),4000) <0.)

flag_msh value is either 1 (THEMIS A is in the magnetosheath) or 0

Time delay between ACE and THEMIS A

It is computed along the XGSE direction : T=|XACE-XTHEMIS_A|/VSW

Time Dalay


Here the delay T varies much more, a banded delay could be adopted (not implemented here) with conditional parameters :





  • In AMDA a conditional parameter P is such that P=1 if P is true Ex: C=A*(T<3600)+*(T>3600) is equal to either A or B depending on the value of T*


  • Refine analysis with smaller ram pressure domains
  • Extend to larger time intervals, and other S/C (all THEMIS, CLUSTER, ...)
  • Extend to magnetosphere and solar wind region determinations
  • Use this procedure to deduce bow shock and magnetopause models

Tools enhancements

    • Bin value on mouse over
    • Over plot of contours and user defined lines on density maps
  • AMDA
    • Delay procedure (continuous instead of constant or banded)

Using the binning TOPCAT functionality for density map

9 10 11


Please refer this tutorial to the original version

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