Long-term monthly statistics of mid-latitudinal NmF2 in the northern geographic hemisphere during geomagnetically quiet and steadily low solar activity conditions

Long-term mid-latitude hourly values of NmF2 measured in 1957–2015 by 10 ionosondes in the Northern geographic hemisphere were processed to select periods of geomagnetically quiet and low solar activity conditions to calculate several descriptive statistics of the noon NmF2 for each month, including the mathematical expectation, most probable value, arithmetic average, and arithmetic average median. The month-to-month variability of these descriptors allowed us to identify months of a year when they reach their extremes (maxima, minima). The calculated month-to-month variations of the NmF2 statistical parameters made it possible to study the winter anomaly and spring–autumn asymmetry in these statistical parameters. •The month-to-month variability of the NmF2 statistical parameters.•The winter anomaly in the NmF2 statistical parameters.•The spring-autumn asymmetry in the NmF2 statistical parameters.