Deep Dive: E3C02
The correct answer is A: Increasing disturbance of the geomagnetic field. What is indicated by a rising A-index or K-index is increasing disturbance of the geomagnetic field. Higher A/K indices mean more geomagnetic disturbance. For amateur radio operators, this is important for understanding propagation conditions. Understanding this helps when evaluating propagation.
Why Other Answers Are Wrong
Option B: Incorrect. Decreasing disturbance isn't indicated - rising indices mean increasing disturbance. Decreasing is wrong. Option C: Incorrect. Higher levels of solar UV radiation isn't what A/K indices measure - they measure geomagnetic disturbance. UV radiation isn't the indication. Option D: Incorrect. Increase in critical frequency isn't what A/K indices indicate - they indicate geomagnetic disturbance. Critical frequency isn't the indication.
Exam Tip
Rising A/K index = increasing disturbance of geomagnetic field. Think 'R'ising 'A'/'K' = 'R'ising 'A'ctivity/'K'haos. Higher A/K indices mean more geomagnetic disturbance. Not decreasing, not UV radiation, not critical frequency - just increasing geomagnetic disturbance.
Memory Aid
Rising A/K index = increasing disturbance of geomagnetic field. Think 'R'ising 'A'/'K' = 'I'ncreasing 'D'isturbance. Higher A/K indices mean more geomagnetic disturbance. Important for understanding propagation conditions.
Real-World Example
A rising A-index or K-index: It indicates increasing disturbance of the geomagnetic field. Higher indices mean the Earth's magnetic field is more disturbed, which can affect HF propagation (especially polar paths). This is what rising indices indicate - increasing geomagnetic disturbance.
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.