Solar Flare Scale: 

• A and B Class: The weakest flares; almost always harmless.

• C Class: Minor, small-scale flares. They barely affect Earth, though long-duration C-flares can occasionally produce slow-moving coronal mass ejections (CMEs).

• M Class: Medium-sized flares. They frequently trigger brief radio blackouts at Earth's polar regions.

• X Class: The largest flares. These major events can trigger global radio blackouts and long-lasting radiation storms.

K-Index Scale:

• 0–2 (Quiet): Calm conditions with minimal geomagnetic activity. Excellent for high-frequency (HF) radio propagation and completely safe for drone flying or satellite operations. Auroras are generally confined near the poles.

• 3–4 (Unsettled to Active): Moderate geomagnetic activity. May cause slight radio signal degradation. A \(Kp\) of 4 is the baseline often needed to potentially spot auroras in northern regions of the contiguous U.S..

• 5–9 (Geomagnetic Storm): These levels indicate a solar storm is actively impacting Earth.