☀Space Weather

EUV wavelengths: Each filter reveals a layer of the solar corona at a different temperature. 94Å (~6M°C, active regions), 131Å (~10M°C, flares), 171Å (~1M°C, coronal loops), 195Å (~1.5M°C, general corona), 284Å (~2M°C, hot corona), 304Å (~80,000°C, chromosphere and prominences). The LASCO coronagraphs block the solar disk to reveal CMEs.

Flare classification: Measured by X-ray intensity. C-Class (common, minor impact on HF radio). M-Class (moderate, radio blackouts at high latitudes, GPS degradation). X-Class (the most powerful, global radio blackouts, radiation storms, associated with CMEs that produce severe geomagnetic storms 1-3 days later).

What is the solar wind? A stream of plasma (protons, electrons) emitted by the solar corona at 300-800+ km/s. The DSCOVR satellite at the L1 point (~1.5M km from Earth) measures it ~15-60 min before it arrives. The Bz component is key: when it points south (negative), it reconnects with Earth's field and triggers geomagnetic storms and auroras.

Components: Hp (parallel) is the most sensitive to magnetosphere compressions. He (east) detects tail currents. Hn (north) complements the measurement in the meridian plane.

Hemispheric power: <10 GW: aurora confined to the polar circle. 10-20 GW: moderate aurora at high latitudes. 20-50 GW: notable activity at mid-latitudes. >100 GW: severe storm with auroras at low latitudes.