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

Abstract

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 ionospherelayer was carried out in Huancayo and Jicamarca. We calculated the NmF2E mathematical expectation,the NmF2A arithmetic mean, the most probable NmF2MP, the NmF2MED arithmetic mean monthlymedian, standard deviations σE, σA, σMP, and σMED and coefficients of variations CVE, CVA, CVMP, andCVMED of the NmF2 value from NmF2E, NmF2A, NmF2MP, and NmF2MED, respectively. It has been foundthat the difference of NmF2MED(UT,M) from NmF2E(UT,M) does not exceed 46%, NmF2MP(UT,M) fromNmF2E(UT,M): 102% and NmF2MP(UT,M) from NmF2MED(UT,M): 85%, where UT is Universal Time.The calculated statistical parameters σE, σA, σMP, σMED, 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%, respectively,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 expectationof NmF2 provides the best description of the set of NmF2 measurements with one single NmF2 statisticalparameter 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%).