The Earth's magnetic field (the magnetosphere) varies both temporally (there is a daily variation of around 30 nT at mid latitudes and hundreds of nT at the poles) and spatially (from around 20,000 nT near the equator to 80,000 nT near the poles) for various reasons, such as the inhomogeneity of rocks and the interaction between charged particles from the Sun and the magnetosphere. Geomagnetic storms can cause much larger variations, but, on average, the Earth's magnetic field is relatively weak. A simple magnet from a hardware store produces a field hundreds of times stronger.