As a first try, you can tweak the <options> of pst-magneticfield as in
%&pdflatex
% !TeX TXS-program:compile = txs:///pdflatex/[--shell-escape]
\documentclass{standalone}
\usepackage{pst-magneticfield}
\usepackage{graphicx}
\usepackage{pstricks-add, auto-pst-pdf}
\begin{document}
\psset{unit=0.5}
\begin{pspicture*}(-10,-12)(10,12)
\psframe[linecolor=black, fillstyle=solid,fillcolor=gray](-2,-3)(2,3)
\psmagneticfield[linecolor=black,N=2,R=2,L=1,PasB=0.4,nS=0,nL=7,pointsB
=1000](-10,-12)(10,12)
\rput(0,-2.6){\textcolor{white}{S}}
\rput(0,2.6){\textcolor{white}{N}}
\end{pspicture*}
\end{document}
to achieve something closer to your requirement as in
However, this is not the exact output you would desire. Plese note that I still am figuring out how to remove the red-lines that is appearing over the magnet. Also, dont forgot to escape the shell, if you are compiling with pdflatex which is necessary due to the usage of auto-pst-pdf.
** Update 1** By making drawSelf = false, you can remove the unwanted coils atop your magnets.
\psmagneticfield[linecolor=black,N=2,R=2,L=1,PasB=0.4,nS=0,nL=7,pointsB=1000, drawSelf = false]
This gives:
Addendum 1:
Apparently scripting this from scratch yields much more better results and makes our life easier ;). However, I am not sure of the technical accuracy! So, what do we need: A few ellipses, a box, a straight line and finally a few texts.
Note: This script can be optimised much better than it is currently presented.
%&pdflatex
% !TeX TXS-program:compile = txs:///pdflatex/[--shell-escape]
\documentclass[a4paper, pdf, x11names]{standalone}
\usepackage{pstricks}
\usepackage{graphicx}
\usepackage{pstricks-add, auto-pst-pdf}
\begin{document}
\psset{unit = 6mm}
\begin{pspicture}(-5,-4)(2,4)
% magnet
\psframe[linecolor=black, fillstyle=solid,fillcolor=gray](-3,-2.5)(0,2.5)
%right side
\psellipticarc[rot=0, linecolor = red]{->}(0.4,0)(1,2){0}{360}
\psellipticarc[rot=0, linecolor = red]{->}(0.4,0)(1.2,2.7){0}{360}
\psellipticarc[rot=0, linecolor = red]{->}(0.4,0)(1.4,3.4){0}{360}
%closing the gaps
\psellipticarc[rot=0, linecolor = red](0.4,0)(1,2){350}{10}
\psellipticarc[rot=0, linecolor = red](0.4,0)(1.2,2.7){350}{10}
\psellipticarc[rot=0, linecolor = red](0.4,0)(1.4,3.4){350}{10}
%left side and mirror
\psellipticarc[rot=0, linecolor = red]{<-}(-3.4,0)(1,2){-180}{0}
\psellipticarc[rot=0, linecolor = red]{<-}(-3.4,0)(1.2,2.7){-180}{0}
\psellipticarc[rot=0, linecolor = red]{<-}(-3.4,0)(1.4,3.4){-180}{0}
\psellipticarc[rot=0, linecolor = red](-3.4,0)(1,2){0}{190}
\psellipticarc[rot=0, linecolor = red](-3.4,0)(1.2,2.7){0}{190}
\psellipticarc[rot=0, linecolor = red](-3.4,0)(1.4,3.4){0}{190}
%interesting stuff
\psellipticarc[rot=0, linecolor = red]{-<}(-3.4,0)(1.6,4.1){-90}{80}
\psellipticarc[rot=0, linecolor = red](-3.4,0)(1.6,4.1){70}{90}
\psellipticarc[rot=0, linecolor = red]{>-}(0.4,0)(1.6,4.1){100}{-90}
\psellipticarc[rot=0, linecolor = red](0.4,0)(1.6,4.1){90}{110}
% allied extras
\psellipticarc[rot=0, linecolor = red]{-<}(-3.4,0)(1.8,4.8){-90}{80}
\psellipticarc[rot=0, linecolor = red](-3.4,0)(1.8,4.8){70}{90}
\psellipticarc[rot=0, linecolor = red]{>-}(0.4,0)(1.8,4.8){100}{-90}
\psellipticarc[rot=0, linecolor = red](0.4,0)(1.8,4.8){90}{110}
%the straight strip
\psline[linecolor=red]{>-}(-1.5,4)(-1.5,-4)
\psline[linecolor=red](-1.5,4)(-1.5,3.9)
%which direction is my magnetic field going huh?
\rput(-1.5,-2.1){N}
\rput(-1.5,2.1){S}
% now you know
\end{pspicture}
\end{document}
This gives,
Addendum 2: Based on @GodMustBeCrazy's comment on What if there is more than one magnet, we can achieve close to desired results by abusing the pst-electricfield package as in
%&pdflatex
% !TeX TXS-program:compile = txs:///pdflatex/[--shell-escape]
\documentclass[a4paper, pdf, x11names]{standalone}
\usepackage{pstricks}
\usepackage{pst-electricfield}
\usepackage{pstricks-add, auto-pst-pdf}
%https://tex.stackexchange.com/questions/308036/how-to-draw-a-circle-with-black-border-with-pstricks
\begin{document}
\psset{unit = 6mm}
\begin{pspicture*}(-6,-6)(6,6)
\psframe*[linecolor=white!50](-6,-6)(6,6)
\psElectricfield[Q={[-1 -2 2][1 2 2][-1 2 -2][1 -2 -2]},linecolor=red, radius=0.1]
% fitting the magnets
\psframe[linecolor=black, fillstyle=solid,fillcolor=gray](-2.3,-2.5)(-1.7,-1.5)
\psframe[linecolor=black, fillstyle=solid,fillcolor=gray](-2.3,2.5)(-1.7,1.5)
\psframe[linecolor=black, fillstyle=solid,fillcolor=gray](2.3,-2.5)(1.7,-1.5)
\psframe[linecolor=black, fillstyle=solid,fillcolor=gray](2.3,2.5)(1.7,1.5)
% drawing N-S
\rput(-2,-2.3){\textcolor{white}{\tiny S}}
\rput(-2,-1.7){\textcolor{white}{\tiny N}}
\rput(-2,2.3){\textcolor{white}{\tiny N}}
\rput(-2,1.7){\textcolor{white}{\tiny S}}
\rput(2,-2.3){\textcolor{white}{\tiny N}}
\rput(2,-1.7){\textcolor{white}{\tiny S}}
\rput(2,2.3){\textcolor{white}{\tiny S}}
\rput(2,1.7){\textcolor{white}{\tiny N}}
\end{pspicture*}
\end{document}
to get:
This is just a try for fun, I am really not sure about the technical accuracy of the results (been a little rusty in electromagnetics, been a long since I looked into them). Thanks to @Herbert for a nice answer that he made in the past ;)
