how to insert a geomagnetic equator line in the map plot

Hi i had problem to insert geomagnetic equator line into the current map, can anyone help

here is my code and the figure that i want to insert the geomagnetic equator line

% Define station coordinates
stations = {
    'Langkawi (LKW)', 6.32, 99.85;
    'Terengganu (TRE)', 5.33, 103.15;
    'Johor (JOH)', 1.49, 103.76;
    'Ranau (RAN)', 5.96, 116.67
    };

% Create a world map focused on Malaysia
figure;
worldmap([0 12], [90 122]);
load coastlines
geoshow(coastlat, coastlon, 'DisplayType', 'polygon', 'FaceColor', [0.8 0.8 0.8]);

% Add country borders
borders = shaperead('landareas', 'UseGeoCoords', true);
geoshow(borders, 'FaceColor', 'none', 'EdgeColor', [0.5 0.5 0.5]);

% Add station points
for i = 1:size(stations,1)
    lat = stations{i,2};
    lon = stations{i,3};
    textm(lat+0.2, lon, stations{i,1}, 'Color', 'r', 'FontWeight', 'bold');
    plotm(lat, lon, 'ro', 'MarkerFaceColor', 'r');
end

% Add legend and title
title('Station Locations in Malaysia with Geomagnetic Equator');

[Les Beckham]

You haven't shown the code which you used to try to insert the geomagnetic equator line, nor have you shown what the problem is. Please update your question to show what the issue is.

[ScottB]

As far as data you can use this map:

geomagnetic equator

and this converter (Geomagnetic<-->Geographic):

coordinate converter

to develop a few data points for use in plotting the geomagnetic equator for your area of interest.