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Magnetospheric regions automatic identification with AMDA and TOPCAT

Authors
Change Log [Science Use Case](#Science Use Case)
Goals
Steps
References

Authors

V. Génot , October 2012 , V2 vincent.genot@irap.omp.eu

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

Goals

  • 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

Steps

Magnetospheric region identification in Paper1

1

THEMIS A magnetospheric sampling over ~3 years

2

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

3

Magnetospheric Regions

4

Bow shock and magnetopause identification

5

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 http://cdpp-amda.cesr.fr/DDHTML/HELP/delay.html
  • 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

6
It is computed along the XGSE direction : T=|XACE-XTHEMIS_A|/VSW

Time Dalay

7

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

bs_tha(3)/shiftT_(imf(3),2400)  

or

bs_tha(3)/shiftT_(imf(3),3200)  

or

bs_tha(3)/shiftT_(imf(3),4000)  
  • 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*
8

Perspectives

  • 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

  • TOPCAT
    • 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

References

Please refer this tutorial to the original version


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