Deep Dive: E3C01
The correct answer is D: Solar flares. What is the cause of short-term radio blackouts is solar flares. Solar flares cause sudden ionization that absorbs HF signals. For amateur radio operators, this is important for understanding propagation disruptions. Understanding this helps when experiencing blackouts.
Why Other Answers Are Wrong
Option A: Incorrect. Coronal mass ejections cause longer-term effects, not short-term blackouts - solar flares cause short-term blackouts. CME isn't the cause. Option B: Incorrect. Sunspots on solar equator don't cause short-term blackouts - solar flares do. Sunspots isn't the cause. Option C: Incorrect. North-oriented interplanetary magnetic field doesn't cause short-term blackouts - solar flares do. Magnetic field orientation isn't the cause.
Exam Tip
Short-term radio blackout cause = solar flares. Think 'S'hort-'T'erm 'B'lackout = 'S'olar 'F'lares. Solar flares cause sudden ionization that absorbs HF signals. Not CME, not sunspots, not magnetic field - just solar flares.
Memory Aid
Short-term radio blackout cause = solar flares. Think 'S'hort-'T'erm = 'S'olar 'F'lares. Solar flares cause sudden ionization that absorbs HF signals. Important for understanding propagation disruptions.
Real-World Example
Short-term radio blackouts: They're caused by solar flares. When a solar flare occurs, it creates sudden ionization in the D layer of the ionosphere, which absorbs HF signals and causes immediate blackouts. This is different from coronal mass ejections which cause longer-term effects. This is the cause - solar flares.
Source & Coverage
Question Pool: 2024-2028 Question Pool
Subelement: E3C
Reference: 2024-2028 Question Pool · E3 - Radio Wave Propagation
Key Concepts
Verified Content
Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E3C topic.