Characteristics of ionospheric minimum frequency obtained by DPS-4 digisonde and comparison with IRI-D-region electron density over Jicamarca station

Abstract

The ionospheric minimum frequency (fmin) is one of the parameters measured by an ionosonde representing the least frequency for which a high frequency (HF) radio signal reflected and received by the ionosphere. Using the digisonde measurement at the Jicamarca station (12º S, 76.87 º W), a statistical study of the temporal variation of fmin was studied. The result also demonstrated the relationship existing between fmin and the electron density of the D-region (NmD) obtained from the IRI-2012 model prediction. We observed generally that the magnitude of fmin is lower during the night time and higher during the daytime. The monthly noontime averages of fmin are highest in February with value reaching 5.23 MHz while outside this period, fmin is within the range of ~1.80 (at night time) to 2.60 MHz (maximum in the morning). This indicates the possibility of radio absorption below the fmin value. We observed a similar trend between the values of fmin and NmD. Both parameters exhibit midday peak and maxima in the southern summer season. The correlation coefficient (r) of 5.4 was obtained between fmin and NmD when the measured frequency is ≥ 3.00 MHz. Considering D-region as an absorbing layer, the correlation tends to indicate a possible significant relationship between fmin and NmD. This infers the usefulness fmin as a proxy parameter for studying radio absorption in the ionosphere