Bow Shock
Definition
The shock wave that forms where the supersonic solar wind first slams into Earth's magnetic field.
In plain language
Like the bow wave in front of a ship, a permanent shock front stands upstream of Earth where the solar wind abruptly slows and heats before flowing around the magnetic bubble.
The science
The bow shock decelerates the super-magnetosonic solar wind, standing ~13โ15 Earth radii sunward. Downstream, the shocked, turbulent magnetosheath plasma drapes around the magnetopause.
Why it matters for aurora viewing
Mostly a supporting actor for viewers, but shock arrivals from CMEs register as sudden jumps on telemetry โ often the first sign a storm has begun.
See this in action on tonight's data.