A Comparative Study of Ionospheric Day‐To‐Day Variability Over Wuhan Based on Ionosonde Measurements and Model Simulations

Abstract

Day-today variability is ubiquitous in the ionosphere. Investigating and understanding the behavior is an important subject for the space environment. Previous studies proposed that ionospheric variability is mainly driven by three sources, including variations in solar activity and geomagnetic activity from above and lower atmospheric perturbations from below. Some general features of ionospheric day-today variability have been observed. Forbes et al. (2000) concluded that the variability in F2 peak electron densities (NmF2) at "high frequencies" (periods of several hours-2 days) and "low frequencies" (periods of 2-30 days) were 25%-35% and 15%-20%, respectively, by analyzing ionosonde data over 100 globally distributed stations under geomagnetic quiet conditions (Kp < 1). Rishbeth & Mendillo (2001) analyzed ionosonde data from 13 stations, with geographic (geomagnetic) latitudes range from −52° to +56° (−58° to +51°) during 1957-1990 and found that the day-today variability of NmF2 exhibits an obvious day-night difference in which the relative standard deviation of the mean value is ∼20% by day and ∼33% by night. Observations of incoherent scatter radar (ISR) revealed that the variability strength is height-dependent because photochemistry and plasma dynamics are dominant in different layers of the ionosphere (Moore et al., 2006). In that paper, they chose high latitudes (EISCAT Svalbard, 78.2°N), mid latitudes (Millstone Hill, 42.6°N), and low latitudes (Jicamarca, 12.1°S) ISR facilities. These works also examined the latitudinal dependence of the

Day‐To‐Day Variability of the MLT DE3 Using Joint Analysis on Observations From TIDI‐TIMED and a Meteor Radar Meridian Chain

“…The difference is supposed to be affected by the solar activity. Although, to our knowledge, no clear evidence has been reported that the level of solar activity could influence the tidal day‐to‐day variabilities in the MLT region, the low solar activity is indeed in favor of the tidal propagation into the thermosphere (Oberheide et al., 2009, 2011b) and generating the ionospheric day‐to‐day variability (Liu, 2020; Zhou et al., 2020, 2021) due to the lower dissipation under solar minimum condition. Whether the solar activity control the MLT tidal day‐to‐day variabilities or not and the corresponding mechanism are worthy of more detailed simulated investigation to provide exact evidence in the future.…”

The Height‐Dependent Delayed Ionospheric Response to Solar EUV

“…The strong difference below 100 km may be attributed variations due to processes in the lower atmosphere which are not taken into account. For example, features of day‐to‐day variability during solar minimum conditions or during nighttime are not well represented by TIE‐GCM, which is likely due to missing variations of perturbations from the lower atmosphere (Zhou et al., 2021). The quality of the ionosonde data must also be considered for the discussion of the observed differences, because uncertainties in the N e profiles are to be expected despite the consideration of only data with AQI of 2 and 3.…”

Quantifying day-to-day variability of O/N2 and its correlation with geomagnetic activity using GOLD

“…Strong agreement between the observed climatology of the IT region and the modeled climatology [from models like the Thermosphere-Ionosphere-Electrodynamics General Circulation Model (TIEGCM), its predecessor the Thermosphere General Circulation Model (TGCM), and the Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension (WACCM-X)] has been demonstrated since as early as 1981 (Dickinson et al, 1981;Richmond et al, 1992;Fesen et al, 2002;Qian et al, 2014;Liu et al, 2018), but the day-to-day variations are comparatively difficult to model/study and therefore less understood (Zhou et al, 2020, Zhou et al, 2021Andoh et al, 2022). Many details of the state of the IT system can be captured by parameters such as the ratio of atomic Oxygen (O) to molecular Nitrogen (N 2 ) (O/N 2 ).…”