What is the increase in velocity of the signal by the ionosphere termed as?

A)
Signal advance
B)
Velocity advance
C)
Phase advance
D)
Differential velocity

Correct Answer :   Phase advance


Explanation : The result of satellite signal travelling through ionosphere is that a particular phase of the signal arrives at the receiver earlier than it would have had if the signal travelled in a complete vacuum. This early arrival is termed as phase advance.