fn = {'312  2004' '313  2004' '314  2004' '315  2004' ...
      '20  2005'  '21  2005'  '22  2005'  '23  2005' ...
      '24  2005'  '148  2005' '149  2005' '150  2005' '151  2005' ...
      '235  2005' '236  2005' '237  2005' ...
      '252  2005' '253  2005' '254  2005' '255  2005' '256  2005'};
  
% northern hemisphere
kN = find(MLAT<45);
ByN = By; ByN(kN) = NaN;
SzN = Sz; SzN(kN) = NaN;

% southern hemisphere
kS = find(MLAT>-45);
ByS = By; ByS(kS) = NaN;
SzS = Sz; SzS(kS) = NaN;

% both hemisspheres
kNS = find(MLAT<45 & MLAT>-45);
ByNS = By; ByNS(kNS) = NaN;
SzNS = Sz; SzNS(kNS) = NaN;

% select day
Day = 1;

% plot data for N 
plot(SzN(Day,:),ByN(Day,:),'.b')
xlabel('Sz  (mW/m^2)','FontSize',12)
ylabel('By  (nT)','FontSize',12)
title(['Northern Hemisphere (Geom)  -  ',fn{Day}],'FontSize',12)

% plot data for S
plot(SzN(Day,:),ByN(Day,:),'.b')
xlabel('Sz  (mW/m^2)','FontSize',12)
ylabel('By  (nT)','FontSize',12)
title(['Southern Hemisphere (Geom)  -  ',fn{Day}],'FontSize',12)

% plot data for N & S
plot(SzN(Day,:),ByN(Day,:),'.b')
xlabel('Sz  (mW/m^2)','FontSize',12)
ylabel('By  (nT)','FontSize',12)
title(['North & South (Geom)  -  ',fn{Day}],'FontSize',12)