How long does it take a coronal mass ejection to affect radio propagation on Earth?
The correct answer is D: 15 hours to several days. It takes 15 hours to several days for a coronal mass ejection (CME) to affect radio propagation on Earth. CMEs are clouds of charged particles that travel much slower than light, taking 1-4 days typically. For amateur radio operators, this is much slower than solar flare radiation (8 minutes). Understanding this helps predict when CME effects will occur.
Exam Tip
CME travel time = 15 hours to several days. Think 'C'ME = 'C'harged 'M'ass 'E'jection takes 'C'onsiderable time (hours to days). Charged particles travel slower than light, taking 15 hours to several days. Not 28 days (rotation), not 4-8 minutes (radiation) - hours to days.
Memory Aid
"CME travel time = 15 hours to several days. Think 'C'ME = 'C'harged 'M'ass 'E'jection takes 'C'onsiderable time. Charged particles travel slower than light, taking 15 hours to several days to reach Earth. Much slower than electromagnetic radiation."
Real-World Application
A coronal mass ejection occurs. The cloud of charged particles travels from the Sun to Earth, taking 1-3 days typically (15 hours to several days). When it arrives, it can cause geomagnetic storms that disrupt HF propagation. This is much slower than solar flare radiation, which takes only 8 minutes (speed of light).
Key Concepts
Why Other Options Are Wrong
Option A (28 days): Incorrect. 28 days is the solar rotation period, not CME travel time. CMEs take much less time (hours to days).
Option B (14 days): Incorrect. 14 days is too long - typical CME travel time is 1-4 days, not 14 days.
Option C (4-8 minutes): Incorrect. 4-8 minutes is for electromagnetic radiation (solar flares), not charged particles (CME). CMEs travel much slower.
题目解析
The correct answer is D: 15 hours to several days. It takes 15 hours to several days for a coronal mass ejection (CME) to affect radio propagation on Earth. CMEs are clouds of charged particles that travel much slower than light, taking 1-4 days typically. For amateur radio operators, this is much slower than solar flare radiation (8 minutes). Understanding this helps predict when CME effects will occur.
考试技巧
CME travel time = 15 hours to several days. Think 'C'ME = 'C'harged 'M'ass 'E'jection takes 'C'onsiderable time (hours to days). Charged particles travel slower than light, taking 15 hours to several days. Not 28 days (rotation), not 4-8 minutes (radiation) - hours to days.
记忆口诀
CME travel time = 15 hours to several days. Think 'C'ME = 'C'harged 'M'ass 'E'jection takes 'C'onsiderable time. Charged particles travel slower than light, taking 15 hours to several days to reach Earth. Much slower than electromagnetic radiation.
实际应用示例
A coronal mass ejection occurs. The cloud of charged particles travels from the Sun to Earth, taking 1-3 days typically (15 hours to several days). When it arrives, it can cause geomagnetic storms that disrupt HF propagation. This is much slower than solar flare radiation, which takes only 8 minutes (speed of light).
错误选项分析
Option A (28 days): Incorrect. 28 days is the solar rotation period, not CME travel time. CMEs take much less time (hours to days). Option B (14 days): Incorrect. 14 days is too long - typical CME travel time is 1-4 days, not 14 days. Option C (4-8 minutes): Incorrect. 4-8 minutes is for electromagnetic radiation (solar flares), not charged particles (CME). CMEs travel much slower.
知识点
Coronal mass ejection, CME, 15 hours to several days, Charged particles
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.