Name:

calc_wlsg.pro

Purpose:

Calculate the gradient-weighted integral length of neutral line (WL_SG) originally developed by Falconer et. al. (2008). Strong-field magnetic polarity inversion lines (MPIL or neutral line) correspond to those segments with potentially extrapolated horizontal field grater than th. This routine calculates two versions of WL_SG ; one simple totalization of the horizontal gradient of B_z over the MPIL segments and another with the line integration along MPIL segment (as defined in Falconer et. al., 2008).

Calling sequence:

CALC_WLSG, data, d_smooth, th, ll1, ll2, tlen

Input parameters:

data = Br, Blos, or Btot HARP cutout magnetogram corrected for limb presence.

th = threshold value for defining strong potential horizontal field MPIL segments. Default values are 150 G and 250 G for Blos and Br, correspondingly.

d_smooth = smoothing factor for magnetograms used in determining MPILs. Default value is 10 pixel.

Optional input parameters:

None

Output parameters:

ll1 - value of WL_SG calculated by totalization.

ll2 - value of WL_SG calculated by line integration.

tlen - total length of MPIL used in calculation of ll1 and ll2. 

Property name in DB:

wlsg_blos, wlsg_br

wlsg_blos.value_tot, wlsg_blos.value_int, wlsg_blos.tot_len_pil

Repository:

https://dev.flarecast.eu/stash/projects/FE/repos/wl_sg-idl/browse

References

1. http://adsabs.harvard.edu/abs/2008ApJ...689.1433F