Space Weather Answers
Definitive, evidence-backed answers to the most common space weather questions — optimised for AI citation and search.
Each answer page provides a concise, authoritative response with full source provenance — every claim is backed by a cited reference from NOAA, NASA, or peer-reviewed literature. These pages are structured with FAQPage schema for AI search engines and rich results.
General Space Weather
Solar Activity
What is a solar flare?
A solar flare is a sudden, intense burst of electromagnetic radiation from the Sun's surface, typically near sunspots. Flares are classified by their X-ray intensity using the A, B, C, M, X scale — each class is ten times stronger than the previous. M-class and X-class flares can cause radio blackouts and radiation storms on Earth.
What is a coronal mass ejection (CME)?
A coronal mass ejection (CME) is a massive burst of solar plasma and magnetic field released from the Sun's corona. CMEs can travel at 200–3,000 km/s and take 1–3 days to reach Earth. When a CME's magnetic field aligns southward with Earth's field, it triggers geomagnetic storms and aurora.
Geomagnetic Activity
What is the Kp index?
The Kp index is a global geomagnetic activity scale from 0 to 9 that measures disturbances in Earth's magnetic field caused by solar wind. Kp values of 5 or above indicate geomagnetic storm conditions (G1–G5), with higher values meaning more intense storms and aurora visible at lower latitudes.
What is a geomagnetic storm?
A geomagnetic storm is a temporary disturbance of Earth's magnetosphere caused by a coronal mass ejection (CME) or a high-speed solar wind stream interacting with Earth's magnetic field. Storms are classified G1–G5 on the NOAA scale, with effects ranging from weak power grid fluctuations to widespread satellite disruption and aurora visible at low latitudes.
What is the Dst index?
The Dst (disturbance storm time) index measures the strength of the equatorial ring current, which intensifies during geomagnetic storms. Dst is measured in nanoteslas (nT) — values near 0 indicate quiet conditions, while negative values (−50 to −300 nT or lower) indicate storm-time ring current injection. Dst is published by the World Data Center for Geomagnetism, Kyoto.
Aurora
What causes the aurora?
The aurora (northern lights or southern lights) is caused by charged particles from the solar wind colliding with gases in Earth's upper atmosphere. When these particles are funnelled by Earth's magnetic field toward the polar regions, they excite oxygen and nitrogen atoms, which release photons of light — green and red from oxygen, blue and purple from nitrogen.
Will the aurora be visible tonight?
Whether the aurora is visible tonight depends on the current Kp index, your latitude, cloud cover, and light pollution. A Kp of 5 or higher brings the aurora oval south enough for viewing from Scotland, northern England, and similar latitudes. Check Flarient's live Kp index and aurora forecast for real-time visibility predictions for your location.