Procedure: thm_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. This code has been modified from fac_matrix_make to handle input data that are in DSL coordinates. Arguments: mag_var_name=the name of the tplot variable storing the magnetic field vectors to be used in transformation matrix generation pos_var_name(optional)=the name of the tplot variable storing the position vectors to be used in transformation matrix generation 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. probe=probe(optional) = string indicating the THEMIS probe for systems that use the DSL system. If this keyword is not specified and probe name is required, thm_fac_matrix_make will infer the probe from the 3rd letter of the magnetic field variable. (eg. 'tha_fgs_gsm') If the tplot variable doesn't have a probe label in the name, this can lead to very irregular behavior, so it is recommended that you always specify probe. /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,gsm, or dsl 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 dsl coordinates then you should only use the output matrices to transform other data in dsl 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 'Zdsl', translates from dsl into FAC Definition: X Axis = on plane defined by Zdsl - Z Second coordinate definition: X = Z x Zdsl Third coordinate, Y completes orthogonal RHS (right hand system) triad: XYZ Example: fac_matrix_make,'tha_fgs',other_dim='Xgse',pos_var_name='tha_pos',out_var_name='tha_fgs_fac_mat',probe='a'