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Last modified: Thu Aug 6 12:53:14 2020.
Procedure: fac_matrix_make
Purpose: generates a field aligned coordinate transformation matrix
from an input B vector array(and sometimes a position vector array)
then stores it in a tplot variable
Arguments:
mag_var_name=the name of the tplot variable storing the magnetic field
vectors to be used in transformation matrix generation. This
variable must be in gse or gsm coordinates when passed to this procedure.
pos_var_name(optional)=the name of the tplot variable storing the position
vectors to be used in transformation matrix generation. This
variable must be in gei coordinates when passed to this procedure.
newname(optional)=the name of the tplot variable in which to store
the output
error(optional) = named variable that holds the error state of the
computation 1 = success 0 = failure
other_dim(optional) = the second axis for the field aligned
coordinate system.
/DEGAP: Set to call TDEGAP to remove any gaps from the data. See TDEGAP for
for other options that can be invoked using the _extra keyword.
E.g. thm_fac_matrix_make, 'tha_fgs', other_dim='xgse', /degap, dt=3
************For all transformations Z = B************
Warning about coordinate systems:
B field tplot variable must be in gse or gsm coordinates,
depending on what transformation has been selected.
Position tplot variable must be in gei coordinates. Gei is the default coordinate
system of thm_load_state.
Warning: The resulting transformation matrices will only correctly
transform data from the coordinate system of the input variable to
the field aligned coordinate system. So if mag_var_name is in gse
coordinates then you should only use the output matrices to transform
other data in gse coordinates.
valid second coord(other_dim) options:
'Xgse', (DEFAULT) translates from gse or gsm into FAC
Definition(works on GSE, or GSM):
X Axis = on plane defined by Xgse - Z
Second coordinate definition: Y = Z x X_gse
Third coordinate, X completes orthogonal RHS
(right hand system) triad: XYZ
Note: X_gse is a unit vector pointing in direction from
earth to the sun
'Rgeo',translate from geo into FAC using radial position vector
Rgeo is radial position vector, positive radialy outwards.
Second coordinate definition: Y = Z x Rgeo (eastward)
Third coordinate, X completes orthogonal RHS XYZ.
'mRgeo',translate into FAC using radial position vector
mRgeo is radial position vector, positive radially inwards.
Second coordinate definition: Y = Z x mRgeo (westward)
Third coordinate, X completes orthogonal RHS XYZ.
'Phigeo', translate into FAC using azimuthal position vector
Phigeo is the azimuthal geo position vector, positive Eastward
First coordinate definition: X = Phigeo x Z (positive outwards)
Second coordinate, Y ~ Phigeo (eastward) completes orthogonal RHS XYZ
'mPhigeo', translate into FAC using azimuthal position vector
mPhigeo is minus the azimuthal geo position vector; positive Westward
First coordinate definition: X = mPhigeo x Z (positive inwards)
Second coordinate, Y ~ mPhigeo (Westward) completes orthogonal RHS XYZ
'Phism', translate into FAC using azimuthal Solar Magnetospheric vector.
Phism is "phi" vector of satellite position in SM coordinates.
Y Axis = on plane defined by Phism-Z, normal to Z
Second coordinate definition: X = Phism x Z
Third completes orthogonal RHS XYZ
'mPhism', translate into FAC using azimuthal Solar Magnetospheric vector.
mPhism is minus "phi" vector of satellite position in SM coordinates.
Y Axis = on plane defined by Phism-Z, normal to Z
Second coordinate definition: X = mPhism x Z
Third completes orthogonal RHS XYZ
'Ygsm', translate into FAC using cartesian Ygsm position as other dimension.
Y Axis on plane defined by Ygsm and Z
First coordinate definition: X = Ygsm x Z
Third completes orthogonal RHS XYZ
Example:
fac_matrix_make,'tha_fgs',other_dim='Xgse',pos_var_name='tha_pos',newname='tha_fgs_fac_mat'
Notes:
(See general/cotrans/special/fac/fac_matrix_make.pro)