Space Weather Glossary

Space Weather Glossary - Plain English Guide

Quick reference for daily Space Weather posts. Every term links to the official NOAA source + a one-sentence explanation you can understand.

Last updated: Sep 1, 2026 — Sources: NOAA SWPC

Jump to: Flare Classes | M2 Flare | X Flare | Radio Blackouts | CME | G-Storms & Kp | S-Storms | Aurora | NOAA Links

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1. Solar Flare Classes — A, B, C, M, X

Solar flares are bursts of X-rays from sunspots. NASA measures them with GOES satellites in watts/m². Scale is logarithmic — each letter is 10x stronger than previous.

• A = 10⁻⁸ W/m² — Background, too weak to matter
• B = 10⁻⁷ W/m² — Very small
• C = 10⁻⁶ W/m² — Small, common, little Earth effect
• M = 10⁻⁵ W/m² — MODERATE Can cause brief radio blackouts
• X = 10⁻⁴ W/m² — EXTREME Major events, 10x an M

Number after letter = strength: M1 = 1x M threshold, M5 = 5x, M9.9 = almost X. Same for X.

Official: NOAA — Solar Flares Explained

What is an M2 Solar Flare?

M2 + R1 Minor — A moderate flare, 2x the M1 threshold (2×10⁻⁵ W/m²).

Plain English: Sunspot burped. Daytime ham radio and aviation HF (3-30 MHz) may fade for 10-30 mins on sunlit side. GPS and cell phones NOT affected.

Compare: M5 = R2 Moderate, M5+ triggers NOAA alert.

More: NOAA Scales Explanation — M to R correlation

What is an X Flare?

X1 = R3 Strong, X10 = R4 Severe, X20 = R5 Extreme. X is 10x M. An X2 is twice an X1.

Impact: Wide-area HF blackout 1-2 hrs, low-frequency navigation degraded, satellite issues possible.

2. Radio Blackouts — R1 to R5 Scale

R-scale measures HF radio blackout from flare X-rays. It's what you feel on Earth minutes after flare.

• R1 Minor (M1) — Weak fade, occasional loss
• R2 Moderate (M5) — Limited blackout, loss of contact
• R3 Strong (X1) — Wide blackout, 1 hr
• R4 Severe (X10) — 1-2 hr blackout
• R5 Extreme (X20) — Multi-hour, complete

Source: NOAA Space Weather Scales

3. CME — Coronal Mass Ejection

Giant cloud of magnetized plasma blown off Sun. Unlike flare light (arrives in 8 mins), CME takes 1-4 days to reach Earth. If Earth-directed, it can cause geomagnetic storm.

Not all flares have CMEs. M and X flares often do.

Source: NOAA — Coronal Mass Ejections

4. Geomagnetic Storms — G1 to G5 & Kp Index

G1 Minor, G2 Moderate, G3 Strong, G4 Severe, G5 Extreme

When CME hits Earth's magnetosphere, it shakes magnetic field. Measured by Kp index (0-9). NOAA scale:

• G1 (Kp=5) — Aurora visible in northern US, minor power grid fluctuations
• G2 (Kp=6) — Aurora to New York/Idaho, voltage alarms
• G3 (Kp=7) — Aurora to Illinois/Oregon, satellite drag, GPS wobble
• G4 (Kp=8) — Aurora to Alabama/California, power grid possible issues
• G5 (Kp=9) — Extreme, aurora to Texas, widespread grid problems (rare)

Sources: NOAA — Geomagnetic Storms | Current Kp Index

5. Solar Radiation Storms — S1 to S5

Protons accelerated by flare/CME. Danger to astronauts, high-altitude flights, satellite memory glitches. Not a ground-level danger except S5.

Source: NOAA — Solar Radiation Storms

6. Aurora / Northern Lights

Aurora happens when G-storm dumps energy into atmosphere. Higher Kp = farther south.

Check: NOAA Aurora Forecast Map (30-min) and Alerts

7. Official NOAA Links — Use These in Daily Posts

• NOAA Scales Explanation (R,S,G table) — link M2 → R1 here
• Solar Flare / Radio Blackout explainer
• CME explainer
• Geomagnetic Storm explainer
• 3-Day Forecast
• Aurora Oval Map Image

Plain-English summaries by Meta AI, facts from NOAA SWPC. For official alerts always check SWPC.

--- Live at: https://spaceweather.portnoithegroundhog.com/p/space-weather-glossary.html Anchors: #M-flare #X-flare #G-storm #flare-classes #cme #radio-blackout