  This work presents the study of the variability of foF2 and hmF2 at a low
latitude station in South America (Tucum\'an, 26.9{\deg}S, 294.6{\deg}E;
magnetic latitude 15.5{\deg}S, Argentina). Ground based ionosonde measurements
obtained during different seasonal and solar activity conditions (a year of low
solar activity, 2009 and one of high solar activity, 2016) are considered in
order to compare the ionospheric behavior. The parameters used to analyze the
variability are the median, upper and lower quartiles. In addition, the foF2
values are compared with those estimated by the International Reference
Ionosphere (IRI) - 2016 model. It is found that: a) A clear dependence on solar
activity is observed in foF2 and hmF2, both increase with increase in solar
activity. b) the variability of foF2 is higher at low solar activity, this
behavior is not observed in hmF2 that present similar variability during both
periods. c) the variability of foF2 is larger at night than during the day,
this behavior is more pronounced during the high solar activity period. d) The
variability of foF2 is higher than that of hmF2. e) Significant planetary wave
spectral peaks at about 2 and 5 days are observed at high and low solar
activity. f) In general, IRI overestimates foF2 during daytime, and
underestimates it at post-sunset period, a better agreement is shown during
nighttime.
