Large branches of trees sway, and thin ones bend; whistling heard in telegraph wires; umbrellas used with difficulty.
At Sea:
Large waves form on the sea; the white foam crests are more extensive everywhere.
Power systems: Possible widespread voltage control problems and
some protective systems will mistakenly trip out key assets from the grid.
Spacecraft operations: May experience surface charging and tracking problems,
corrections may be needed for orientation problems.
Other systems: Induced pipeline currents affect preventive measures, HF radio propagation sporadic,
satellite navigation degraded for hours, low-frequency radio navigation disrupted,
and aurora has been seen as low as Alabama and northern California (typically 45° geomagnetic latitude.).