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Description

A magnetic polarity inversion line (MPIL) in the photosphere of an active region (AR) separates distinct patches of positive and negative magnetic polarities. There have been several studies showing the relation between flare occurrence and MPIL characteristics (e.g., Schrijver 2007; Mason and Hoeksema 2010; Falconer et al. 2012). In particular, strong-gradient, strong-field MPILs (^sMPILs) have been considered as the most likely place where flux cancellation and/or flux rope emergence can take place in relation to the triggering of flares (e.g., Fang et al. 2012). We developed an algorithm to determine and characterise ^sMPILs in ARs. 

Input data

B_los and B_r images from SDO/HMI Space-weather HMI Active Region Patch (SHARP) cylindrical equal area (CEA) near-realtime (NRT) data

Output parameters 

MPIL_BLOS.MAX_LENGTH: Length of the longest ^sMPIL segment calculated from B_los of a given AR

MPIL_BLOS.TOT_LENGTH: Total length of ^sMPIL segments calculated from B_los of a given AR

MPIL_BLOS.TOT_USFLUX: Total unsigned magnetic flux around ^sMPIL segments calculated from B_los of a given AR

MPIL_BR.MAX_LENGTH: Length of the longest ^sMPIL segment calculated from B_r of a given AR

MPIL_BR.TOT_LENGTH: Total length of ^sMPIL segments calculated from B_r of a given AR

MPIL_BR.TOT_USFLUX: Total unsigned magnetic flux around ^sMPIL segments calculated from B_r of a given AR

Name: 

mpil.pro

Purpose: 

Calculates some characteristics of strong-gradient, strong-field magnetic polarity inversion lines (MPILs) in active regions

Calling sequence:

output_mpil=mpil(c_img, mpil_info=mpil_info, mpil_xy=mpil_xy, binxy=binxy, detail1=detail1, minsize1=minsize1, pbt_thresh1=pbt_thresh1, thresh1=thresh1, isth_cut1=isth_cut1, $

                            detail2=detail2, minsize2=minsize2, pbt_thresh2=pbt_thresh2, thresh2=thresh2, isth_cut2=isth_cut2, sep=sep, xy_pixel=xy_pixel)

Input parameters:

c_img : B_r or B_los SHARP cutout magnetogram, corrected for limb presence. Blos cutout should be deprojected.

Input Keywords:

binxy - number for xy spatial binning of the sharp magnetic field input data [in pixels] ; default=1 (i.e., no binning)

detail1 & detail2 - width of the smoothing window, which is used for a two-step MPIL detection algorithm [in pixels] ; default=6 & 3

minsize1 & minsize2 - threshold for the length of a single MPIL (used for two-step MPIL detection algorithm) [in Mm] ; default=5.5 & 2

pbt_thresh1 & pbt_thresh2 - threshold for the strength of the horizontal component of potential magnetic field on the photosphere (used for two-step MPIL detection algorithm) [in Gauss]; defualt=120 & 100

thresh1 & thresh2 - threshold for the gradient of Bz on the photosphere (used for two-step MPIL detection algorithm) [Gauss] ; defualt=20 & 8

isth_cut1 & isth_cut2 - distance within which separated segments of a single MPIL will be connected (used for two-step MPIL detection algorithm) [in Mm]; default=2 & 1

grad_width - distance for the horizontal gradient of Bz [in Mm]; default=3.5

sep - distance within which MPILs will be considered as a same group [in Mm]; default=11

xy_pixel - xy distance from MPILs for calculating total unsigned magnetic flux around MPILs [in Mm]; default=2

Output Keywords:  

mpil_info - information on types of MPILs

mpil_xy - x and y coordinates of MPILs [pixels]

Output:

output_mpil - 3 element 1D array related to the properties of MPILs

                      output_mpil[0]: total length of MPILs [Mm]

                      output_mpil[1]: length of the longest MPIL [Mm] 

                      output_mpil[2]: total unsigned magnetic flux around MPILs [10^20 Mx]

Property name in DB:

mpil_blos.max_length, mpil_blos.tot_length, mpil_blos.tot_usflux, mpil_br.max_length, mpil_br.tot_length, mpil_br.tot_usflux

Repository

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

References