Global Longitudinal Behavior of IRI Bottomside Profile Parameters From FORMOSAT‐3/COSMIC Ionospheric Occultations

Abstract

The bottomside thickness and shape (B0 and B1) are the critical key elements for depicting a realistic electron density profile in the International Reference Ionosphere (IRI) model. We investigated their longitudinal variability using a large database of FORMOSAT‐3/COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) electron density profiles covering the period 2006–2015 from which these parameters are derived using a simple analytic Chapman least squares fitting. The parameters are then compared with the IRI‐2012 submodels, that is, Bil‐2000, Gul‐1987, and ABT‐2009 during different seasons and solar activity. Besides apparent adherence of B0 to the equatorial region, the opposite occurrence pattern of maximum B0 to that of NmF2 is realized, manifesting semiannual distribution and hemispheric asymmetry. Unlike NmF2, the presence of single anomaly crest in B0 in all seasons except March equinox and their leading local time stamps are among the key observations. In spite of regular representation of IRI submodels during equinox, the performance of Gul‐1987 seems to be inferior during solstice with respect to geomagnetic field and equatorial electrodynamics, thereby depicting an erroneous distribution of B0. The striking wave‐like feature in B0 longitudinal variability is also revealed indicating its possible connection with the nonmigrating diurnal/semidiurnal tides. Moreover, the solar activity effect on B0 appears to be relatively higher over the Asian and Pacific longitudes (60–150°E). Although speculations are made over B1 variability, its complete longitudinal characteristics are indistinguishable in our results, except the subordinate magnitude as compared to IRI estimations. The important findings from this study may reinforce the understanding of bottomside variability and future improvements in IRI.

Observations and simulations of large-scale traveling ionospheric disturbances during the January 14-15, 2022 geomagnetic storm

“…studies (e.g., Lin et al, 2005;Rajesh et al, 2021). During quiet time, EIA is the region between ±10°and ±15°magnetic latitude (MLat) across the magnetic equator (center) (e.g., Panda et al, 2018;Rajesh et al, 2021;Ogwala et al, 2022). As shown in Figure 2A, during the disturbed time, EIA in both hemispheres expands to higher latitudes, even to middle and high latitudes.…”

Comparison between RO and Digisonde topside plasma frequency over European Digisonde stations

“…This approach was very powerful in the sense that it leveraged the inherent weakness of ionosondes that can only probe the EDP up to the F-layer peak at a specific location with the superiority of the RO technique to monitor the EDP beyond the F-layer peak on a global scale. Based on this compromise offered by each technique, comparison studies of peak ionospheric characteristics (NmF2/hmF2) and validation of bottomside and topside ionospheric models was possible on the basis of single-station (for example in Cyprus), multi-station and global scale datasets [1][2][3][4] . In addition colocation studies using other instruments such as Incoherent Scatter Radar (ISR) facilitated full (bottomside-topside) EDPs validation 5 .…”

Validation and Improvement of NeQuick Topside Ionospheric Formulation Using COSMIC/FORMOSAT‐3 Data

“…The radio occultation (RO) technique is based on precise dual‐frequency phase measurements (Schreiner et al., 1999) from global navigation satellite system (GNSS) receivers on board Low‐Earth Orbit (LEO) satellites that exploit radio signals transmitted from GNSS satellites. Many authors have worked on the validation of COSMIC data using colocated digisonde and Incoherent Scatter Radar (ISR) stations (Bai et al., 2019; Cherniak & Zakharenkova, 2014; Hu et al., 2014; Krankowski et al., 2011; Lei et al., 2007; Panda et al., 2018; Shaikh et al., 2018; Singh et al., 2021; Stankov & Jakowski, 2006; Yue et al., 2011).…”