AMDA-TOPCAT use case

Magnetospheric regions automatic identification

V. Génot – October 2012 – V2vincent.genot@irap.omp.eu

Special thanks to the CDPP team, M. Taylor (TOPCAT) & K. Meziane

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

Goal : • Reproduce two paper1’s 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

mag

neto

sphe

re

magnetosheath

solar wind

All THEMIS data 2007/03/01-2009/10/01

With ACE data shifted to THEMIS A position

THEMIS A magnetospheric sampling over ~3 years

3dview.cesr.fr

THEMIS A orbits from 2007/03/01 to 2009/10/01

Magnetospheric regions

-- only THEMIS A

Jelinek et al., JGR 2012

AMDA – TOPCAT analysis

In both cases, the bin/contour represents the number of events

solar wind

magnetosheath

mag

neto

sphe

re

Magnetospheric regions

• rB>4-rn

• rB<10rn

Magnetosheath region

rB=4-rn

rB=10rn

= rn

rB

Condition from the plot above :

Bow shock and magnetopause identification

Jelinek et al., JGR 2012

AMDA – TOPCAT analysis

In both case, each bin represents the probability (<1) for this location to be in the magnetosheath

In TOPCAT this is automatically computed from the flag_msh values

Step by step AMDA–TOPCAT analysisMagnetospheric 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 the « interoperability » and open a SAMP connection• download rB and rn on 2007/03/01 – 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 !

Step by step AMDA–TOPCAT analysisBow 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>4-rn and rB<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

• 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

Transfer via SAMP (same procedure as before)

r_n = n_i_tha/shiftT_(sw(0),4000)

r_b = bs_tha(3)/shiftT_(imf(3),4000)

Parameter definition in AMDA

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

3dview.cesr.fr

Time delay between ACE and THEMIS A

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

Here the delay T is almost constant (2400) so r_b is bs_tha(3)/shiftT_(imf(3),2400)

Time delay

T=2400

T=|XACE-XTHEMIS_A|/VSW

r_b

r_b

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)

T=2400 T=3200 T=4000

Time delay

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

T=|XACE-XTHEMIS_A|/VSW

r_b

r_b

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

Tool 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 :

Using the binning TOPCAT functionality for density map :

Using the binning TOPCAT functionality for density map :