Question 1

What is the Kp Index and how does it affect aurora viewing?

Accepted Answer

The Kp index is a global "geomagnetic disturbance" score from 0-9, measured by 13 magnetometer stations worldwide. Each Kp level pushes the aurora oval about 2° closer to the equator. At Kp 0, aurora stays around 66° latitude; at Kp 5, it reaches 56°; at Kp 9, it can extend to 48°. A Kp of 5+ (G1 storm) means aurora visible at mid-latitudes like Seattle and Chicago.

Question 2

What is Solar Wind Speed and why does it matter for aurora?

Accepted Answer

Solar wind speed is the velocity of charged particles streaming from the Sun. Normal speed is around 375 km/s. Speed is the second most important factor for aurora after Bz. Faster wind means more energy transfer over time, resulting in brighter aurora. Speeds of 500+ km/s indicate strong wind with enhanced aurora, while 600-800 km/s provides optimal conditions.

Question 3

What does Bz mean for aurora forecasting?

Accepted Answer

Bz is the most critical aurora parameter. It measures the north-south orientation of the interplanetary magnetic field. When Bz points south (negative), it can "reconnect" with Earth's northward-pointing field, opening the magnetosphere and allowing solar wind energy to pour in. Bz of -5 nT or stronger means the magnetosphere is open and aurora is active. Positive Bz means Earth's magnetic shield deflects solar wind.

Question 4

What is Particle Density and how does it affect aurora colors?

Accepted Answer

Particle density is the number of protons per cubic centimeter in the solar wind. Higher density means more particles available to excite atmospheric gases and create visible aurora. Density of 10+ particles/cc produces rich, colorful aurora displays, while under 5 particles/cc results in pale, faint aurora. Density can spike dramatically during solar events, often preceding intense auroral activity.

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Qu'est-ce que l'indice Kp ?

Vent solaire

Prévision d'aurores

Carte interactive des aurores

Caméras d'aurores en direct