High frequency limit(GPS case When the EM wave has a high frequency, the dielectric constant can be written as for nz electrons per unit volume 4 INZe e()=1 plasma frequency For the ionosphere, Nz=104-106 electrons/cms and o p is 6-60 of mhz The wave-number is k=.|2a.|C O 04/08/02 12.540Lec1604/08/02 12.540 Lec 16 10 High frequency limit (GPS case) • When the EM wave has a high frequency, the dielectric constant can be written as for NZ electrons per unit volume: • For the ionosphere, NZ=10 4-10 6 electrons/cm 3 and ω p is 6-60 of MHz • The wave-number is e ( ω) = 1 − ω p 2 ω2 ω p 2 = 4 πNZe 2 m ⇒ plasma frequency k = ω2 − ω p 2 / c