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# Directory Listing of Routines

# projects/mms/common/curlometer

- LINGRADEST
  IDL subroutine to calculate magnetic field gradients, divergence, curl, and field line
- MMS_CURL
  This routine calculates div B and curl B for a specified time interval
- MMS_LINGRADEST
  Calculations of Grad, Curl, Curv,..., for MMS using

# Routine Descriptions

## LINGRADEST

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     PROCEDURE:
           lingradest

     PURPOSE:
           IDL subroutine to calculate magnetic field gradients, divergence, curl, and field line
           curvature from 4-point observations

     Input:
           B-field components from the four probes
           Coordinates from the four probes
           Length of vectors (all variables should be interpolated to the same length)

     Method used:
           Linear Gradient/Curl Estimator technique
           see Chanteur, ISSI, 1998, Ch. 11

     Originally designed for Cluster by A. Runov (2003)

     $LastChangedBy: egrimes $
     $LastChangedDate: 2022-03-29 13:55:04 -0700 (Tue, 29 Mar 2022) $
     $LastChangedRevision: 30732 $
     $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/projects/mms/common/curlometer/lingradest.pro $

(See projects/mms/common/curlometer/lingradest.pro)

## MMS_CURL

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     PROCEDURE:
           mms_curl

     PURPOSE:
           This routine calculates div B and curl B for a specified time interval

     KEYWORDS:
           trange: time range over which to compute the curl (will be prompted if not provided)
           fields: array of tplot variables containing the B-field for each spacecraft (in GSE coordinates)
           positions: array of tplot variables containing the S/C position vectors for each spacecraft (also GSE coordinates)

     NOTES:
           The input B-field data and position data are expected to be in
           GSE coordinates

           Original by Jonathan Eastwood, with changes from Tai Phan
           Minor modifications for SPEDAS by egrimes

        For more info on this method, see:
           Chanteur, G., Spatial Interpolation for Four Spacecraft: Theory,
             Chapter 14 of Analysis methods for multi-spacecraft data, G.
             Paschmann and P. W. Daly (Eds.) ISSI Scientific Report SR-001.

     $LastChangedBy: egrimes $
     $LastChangedDate: 2017-04-24 12:09:49 -0700 (Mon, 24 Apr 2017) $
     $LastChangedRevision: 23221 $
     $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/projects/mms/common/curlometer/mms_curl.pro $

(See projects/mms/common/curlometer/mms_curl.pro)

## MMS_LINGRADEST

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     PROCEDURE:
           mms_lingradest

     PURPOSE:
           Calculations of Grad, Curl, Curv,..., for MMS using
           the Linear Gradient/Curl Estimator technique
           see Chanteur, ISSI, 1998, Ch. 11

     Based on Cluster routine (A. Runov, 2003)

     Input: Bxyz from four points with the same time resolution
            and same sampling intervals (joined time series)
            Coordinates of the four points (R) with the same time
            resolution and sampling as Bxyz
            datArrLength := the length of B and R arrays (must be
            the same for all vectors)

     Output: bxbc, bybc, bzbc: B-field in the barycenter
             LGBx, LGBy LGBz: B-gradient at the barycenter
             LCxB, LCvB, LCzB: curl^B at the barycenter
             curv_x_B, curv_y_B, curv_z_B: B-curvature at the
             barycenter, RcurvB: the curvature radius

     $LastChangedBy: egrimes $
     $LastChangedDate: 2017-04-24 12:31:29 -0700 (Mon, 24 Apr 2017) $
     $LastChangedRevision: 23222 $
     $URL: svn+ssh://thmsvn@ambrosia.ssl.berkeley.edu/repos/spdsoft/trunk/projects/mms/common/curlometer/mms_lingradest.pro $

(See projects/mms/common/curlometer/mms_lingradest.pro)