*Question G3A02:
What effect does a sudden ionospheric disturbance have on the daytime ionospheric propagation?*  

*Correct Answer is  B: It disrupts signals on lower frequencies more than those on higher frequencies*  

### AI Response: (may contain errors)  

A sudden ionospheric disturbance, such as a solar flare, can significantly affect HF (high frequency) radio propagation. 

### Correct Answer Explanation:
- **Correct Answer: B: It disrupts signals on lower frequencies more than those on higher frequencies.**
  - During a sudden ionospheric disturbance, the ionosphere becomes more ionized, which can lead to increased absorption of lower frequency signals (like those below 10 MHz). Higher frequencies (above 10 MHz) tend to be less affected because they can penetrate the ionosphere more effectively and are less prone to absorption.

### Incorrect Answer Explanations:
- **A: It enhances propagation on all HF frequencies.**
  - This is incorrect because disturbances typically cause increased absorption and disruption, particularly at lower frequencies, rather than enhancing propagation.

- **C: It disrupts communications via satellite more than direct communications.**
  - This is misleading. While ionospheric disturbances can affect HF communications, satellite communications are primarily affected by the atmosphere and not the ionosphere in the same way. Direct communications (line-of-sight) are generally less impacted.

- **D: None, because only areas on the night side of the Earth are affected.**
  - This is incorrect because disturbances can affect daytime propagation as well. The ionosphere is influenced by solar activity regardless of whether it is day or night in a given location.

### Useful Rules of Thumb:
- Lower frequencies (below 10 MHz) are more susceptible to absorption during disturbances.
- Higher frequencies (above 10 MHz) are generally more reliable during such events.
- The ionosphere's behavior can change rapidly with solar activity, impacting HF propagation significantly.

Understanding these concepts will help you grasp the effects of ionospheric disturbances on radio communications, especially for the Extra Class exam.