Drones rely on GPS for position-holding and a magnetometer (electronic compass) for heading. Both can be affected when geomagnetic activity rises.
Why GPS degrades during geomagnetic storms
Geomagnetic storms disturb the ionosphere, the charged layer of the upper atmosphere that GPS signals pass through on their way from satellites to your drone. Increased ionospheric disturbance introduces extra signal delay and scintillation (rapid signal fluctuation), which reduces position-fix accuracy and, in more severe cases, can cause temporary loss of GPS lock.
Why the compass is affected separately
A drone's magnetometer measures the local magnetic field directly to determine heading. A disturbed geomagnetic field is, by definition, a less stable reference — this is the same physical phenomenon the Kp index quantifies. A compass reading during a storm can drift or "yaw" unexpectedly even when the drone hasn't physically rotated.
What this looks like to a pilot
Symptoms reported during elevated Kp include: the drone's position drifting slightly in GPS mode without stick input, "toilet bowl" circling behavior on return-to-home, or a compass calibration warning that wasn't present the day before in the same location.
Practical takeaway
At Kp 5 and above, treat GPS-assisted flight modes with extra caution — fly at lower altitude, keep the drone closer, and be ready to switch to manual/attitude mode if position-hold becomes unreliable. This is exactly why checking a live Kp reading before flying, not just wind and rain, is part of a complete preflight check.