Diurnal Variations of the Statistical Characteristics of NmF2 Variability According to Ground-Based Low Latitude Ionosondes in Geomagnetically Quiet Conditions at Low Solar Activity

The study of diurnal variations of the statistical characteristics of the day-to-day variability of theNmF2 electron number density of the F2 ionosphere layer for each month (M) of the year in geomagneticallyquiet conditions at low solar activity according to hourly measurements of the critical frequency of the F2 ionosphere layer was carried out in Huancayo and Jicamarca. We calculated the NmF2(E) mathematical expectation, the NmF2(A) arithmetic mean, the most probable NmF2MP, the NmF2(MED) arithmetic mean monthlymedian, standard deviations s(E), s(A), s(MP), and s(MED) and coefficients of variations CVE, CVA, CVMP, andCV(MED) of the NmF2 value from NmF2E, NmF2(A), NmF2(MP), and NmF2(MED), respectively. It has been foundthat the difference of NmF2(MED)(UT,M) from NmF2E(UT,M) does not exceed 46%, NmF2(MP)(UT,M) fromNmF2(E)(UT,M): 102% and NmF2MP(UT,M) from NmF2MED(UT,M): 85%, where UT is Universal Time.The calculated statistical parameters s(E), s(A), s(MP), s(MED), CVE, CVA, CVMP, and CVMED are the characteristicsof the NmF2 variability from one day to another day at fixed M and UT values over low-latitude Huancayoand Jicamarca ionosondes in geomagnetically quiet conditions at low solar activity. The calculations showedthat the CVE, CVMED, and CVMP coefficients vary between 18%-82%, 19%-107%, and 18%-288%, respec-tively, and in the majority of cases, CVE(UT,M) is less than CVMED (UT,M) and CVMP(UT,M). It was shownthat minimizing the standard deviation and the variation coefficient of NmF2 using the mathematical expec-tation of NmF2 provides the best description of the set of NmF2 measurements with one single NmF2 statis-tical parameter under the considered conditions. The lowest CVE varies from 18% (April) to 29% (September)and the highest CVE ranges from 63% (November) to 73% (January). The average CVE value (average relativeday-to-day variability of NmF2) is highest in September (40%) and lowest in April (33%).