Geomagnetic Coordinates & IGRF-14

Aurora doesn't care about your geographic latitude. It follows geomagnetic latitude — your position relative to the Earth's magnetic pole, not the geographic pole. The difference matters a lot, especially in the southern hemisphere.

Geographic vs magnetic latitude

The north magnetic pole is currently somewhere in the Arctic Ocean near northern Canada. The south magnetic pole is off the coast of Antarctica, south of Australia. Because of this offset, the southern hemisphere's magnetic latitudes are shifted northward relative to their geographic counterparts.

In practice, this is good news for Australian and NZ aurora watchers. It means you're effectively "closer to the pole" in magnetic terms than your geographic latitude suggests. Here are some examples:

Notice that Adelaide sits at a higher (ie. closer to the south) magnetic latitude than Melbourne (~50°S vs ~48°S), even though Melbourne is about 3° further south geographically. That's because Adelaide lies almost directly north of the south magnetic pole (which sits south of Western Australia at about 136°E), while Melbourne is further east and the field lines curve away. It's a small difference in practice, but it's a neat reminder that longitude matters too — you need to know where you are relative to the magnetic pole, not just how far south you are.

What is IGRF-14?

Lumina uses the International Geomagnetic Reference Field (IGRF-14) to convert geographic coordinates to geomagnetic ones. IGRF is the gold-standard global model of Earth's magnetic field, updated every five years by the international geomagnetic community. Version 14 covers the 2025 epoch with secular variation forecasts out to 2030.

The conversion isn't a simple lat/lon offset — IGRF models the full 3D magnetic field vector at every point on Earth, accounting for the fact that the field is tilted, offset from Earth's centre, and has complex regional variations.

How Lumina does the conversion

Running the full IGRF model for every API request would be slow. Instead, Lumina pre-computes high-resolution grids covering Australia and New Zealand:

• Australia grid: 0.25° spacing covering 8°S–47°S and 108°E–160°E
• NZ grids: 0.25° spacing covering 32°S–50°S, 160°E– 180° (West) and 180°–172°W (East, across the dateline)

When you make a request, Lumina looks up your location in the grid using bilinear interpolation between the four nearest grid points. This is extremely fast and accurate to within a fraction of a degree. Outside the pre-computed grid regions (if you're travelling overseas, for example), Lumina falls back to the full IGRF calculation.

Why magnetic coordinates matter for aurora

The auroral oval is centred on the geomagnetic pole , not the geographic pole. The solar wind particles that cause aurora are guided by Earth's magnetic field lines — they spiral along field lines and enter the atmosphere where those lines connect to the surface. The whole system is fundamentally magnetic in nature.

This offset is also why aurora is visible from Australia and New Zealand at all. The south magnetic pole sits well off the geographic pole, toward our side of Antarctica, which shifts the entire southern auroral oval northward in geographic terms. Without that offset, the oval would sit squarely over the Southern Ocean and Antarctica — and populated AU/NZ latitudes would almost never see a display.

A good way to see how much this matters: compare Hobart with Ushuaia in southern Argentina. Ushuaia is at ~55°S geographic — a full 12° closer to the South Pole than Hobart. But because the magnetic pole is on the Australian side of Antarctica, Ushuaia's magnetic latitude is only about 40–45°S — around the same as Auckland. Meanwhile Hobart, at a much more modest ~43°S geographic, sits at ~58°S magnetic. The result: Hobart sees regular aurora during moderate activity, while Patagonia generally needs a major storm.

The pole moves

The magnetic poles aren't fixed — they drift over time. The north magnetic pole has been moving toward Siberia at about 50–60 km per year. The south magnetic pole is drifting more slowly. IGRF-14 accounts for this secular variation, so Lumina's conversions stay accurate as the field changes. The model gets updated every five years to stay on top of the drift.