*Question E3B11:
At what time of day is sporadic-E propagation most likely to occur?*  

*Correct Answer is  D: Between sunrise and sunset*  

### AI Response: (may contain errors)  

Sporadic-E propagation is a phenomenon where radio waves are reflected off dense patches of ionization in the E layer of the ionosphere. This type of propagation is most common during the daytime, particularly in the late spring and early summer months.

1. **Correct Answer: Between sunrise and sunset**
   - Sporadic-E propagation is most likely to occur during the daytime, specifically between sunrise and sunset. This is because the ionization levels in the E layer are higher during the day due to solar radiation, which increases the likelihood of sporadic-E events.

2. **Why the other choices are incorrect:**
   - **A: Between midnight and sunrise**  
     - During this time, the ionosphere is generally less ionized because the sun is not providing energy to ionize the atmospheric layers. Sporadic-E events are less common at night.
   - **B: Between sunset and midnight**  
     - After sunset, the ionization in the E layer begins to decrease as the sun's influence wanes, making sporadic-E propagation less likely.
   - **C: Between sunset and sunrise**  
     - This choice encompasses the entire night period, during which the ionization levels are lower, reducing the chances of sporadic-E propagation.

3. **Useful Rule of Thumb:**
   - Sporadic-E is more likely to occur when the sun is up, as solar radiation is a key factor in ionizing the E layer. Therefore, the best time for sporadic-E propagation is typically during daylight hours, especially in the late morning to early evening.