using quiver function to plot vectors on a hemisphere

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John Draper 2015-11-29

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https://ww2.mathworks.cn/matlabcentral/answers/258114-using-quiver-function-to-plot-vectors-on-a-hemisphere

评论： John Draper 2015-11-29

Hi, I'm trying to plot the magnetic field on the surface of a hemisphere (modelling a planetary dipole).

I have created a function magfield2 that produces the direction and magnitude of the magnetic field at some point (X,Y,Z) on the surface of a hemisphere, shown here:

if true
function [U,V,W] = magfield2(X,Y,Z) %U=mag force in X, V=mag force in Y, W=mag force in Z
r=(X.^2+Y.^2+Z.^2)^0.5 ;
U=3*X.*Z./(r.^5);
V=3*X.*Z./(r.^5);
W=((3*Z.^2 - r.^2)/r.^5);
  % code
end

I then try to use this function with the quiver function to plot this magnetic field at the surface as shown here

if true
[X,Y,Z] = sphere(50); %defines meshgrid coverage
[U,V,W] = magfield2(X,Y,Z); %magnetic field function
figure
quiver3(X,Y,Z,U,V,W,0.5)% no defines arrow length, other define direction
%defines arrow direction (u,v,w) at point (x,y,z)
hold on
surf(X,Y,Z) %produces surface
view(-35,45)%canges initial viewing angle
axis([0 3 -1.5 1.5 -1.5 1.5]) %defines axis parameters
hold off
  % code
end

Sadly, this just produces a hemisphere surface with no vectors on it. If I swap the magfield2 function with a surface normal function it seems to work fine.

Any comments/ suggestions would be appreciated. Thanks, John!