Approximately how long does it take the increased ultraviolet and X-ray radiation from a solar flare to affect radio propagation on Earth?
The correct answer is C: 8 minutes. It takes approximately 8 minutes for the increased ultraviolet and X-ray radiation from a solar flare to affect radio propagation on Earth. This is the time it takes for electromagnetic radiation (light, X-rays) to travel from the Sun to Earth. For amateur radio operators, this means SIDs can occur about 8 minutes after a solar flare. Understanding this helps predict when SID effects will occur.
Exam Tip
Solar flare radiation travel time = 8 minutes. Think '8' minutes = '8' minutes for 'E'lectromagnetic radiation. UV and X-ray radiation from solar flares takes about 8 minutes to reach Earth (speed of light). Not 28 days (rotation), not hours (charged particles).
Memory Aid
"Solar flare radiation travel time = 8 minutes. Think '8' minutes = '8' minutes for 'E'lectromagnetic radiation. UV and X-ray radiation from solar flares takes about 8 minutes to reach Earth. Speed of light travel time."
Real-World Application
A major solar flare occurs. About 8 minutes later, the increased UV and X-ray radiation reaches Earth, causing increased D-layer absorption and disrupting propagation. This is much faster than charged particles (which take 20-40 hours), because electromagnetic radiation travels at the speed of light.
Key Concepts
Why Other Options Are Wrong
Option A (28 days): Incorrect. 28 days is the solar rotation period, not the radiation travel time. Radiation travels much faster.
Option B (1-2 hours): Incorrect. 1-2 hours is too long - electromagnetic radiation travels at the speed of light, taking about 8 minutes from Sun to Earth.
Option D (20-40 hours): Incorrect. 20-40 hours is way too long - that's for charged particles (CME), not electromagnetic radiation. Radiation travels at light speed.
题目解析
The correct answer is C: 8 minutes. It takes approximately 8 minutes for the increased ultraviolet and X-ray radiation from a solar flare to affect radio propagation on Earth. This is the time it takes for electromagnetic radiation (light, X-rays) to travel from the Sun to Earth. For amateur radio operators, this means SIDs can occur about 8 minutes after a solar flare. Understanding this helps predict when SID effects will occur.
考试技巧
Solar flare radiation travel time = 8 minutes. Think '8' minutes = '8' minutes for 'E'lectromagnetic radiation. UV and X-ray radiation from solar flares takes about 8 minutes to reach Earth (speed of light). Not 28 days (rotation), not hours (charged particles).
记忆口诀
Solar flare radiation travel time = 8 minutes. Think '8' minutes = '8' minutes for 'E'lectromagnetic radiation. UV and X-ray radiation from solar flares takes about 8 minutes to reach Earth. Speed of light travel time.
实际应用示例
A major solar flare occurs. About 8 minutes later, the increased UV and X-ray radiation reaches Earth, causing increased D-layer absorption and disrupting propagation. This is much faster than charged particles (which take 20-40 hours), because electromagnetic radiation travels at the speed of light.
错误选项分析
Option A (28 days): Incorrect. 28 days is the solar rotation period, not the radiation travel time. Radiation travels much faster. Option B (1-2 hours): Incorrect. 1-2 hours is too long - electromagnetic radiation travels at the speed of light, taking about 8 minutes from Sun to Earth. Option D (20-40 hours): Incorrect. 20-40 hours is way too long - that's for charged particles (CME), not electromagnetic radiation. Radiation travels at light speed.
知识点
Solar flares, Radiation travel time, 8 minutes, SID timing
Verified Content
Question from official FCC General Class question pool. Explanation reviewed by licensed amateur radio operators.