The disturbance storm time (Dst, Kyoto Dst) index is a measure in the context of space weather. It gives information about the strength of the ring current around Earth caused by solar protons and electrons.^[1]

The ring current around Earth produces a magnetic field that is directly opposite Earth's magnetic field, i.e. if the difference between solar electrons and protons gets higher, then Earth's magnetic field becomes weaker.

A negative Dst value means that Earth's magnetic field is weakened. This is particularly the case during solar storms.