Evaluation of Different Methods for Calculating the ROTI Index Over the Brazilian Sector

Abstract

Ionospheric irregularities are known to interfere in the Global Navigation Satellite System (GNSS) radio signals leading to increases in positioning errors as a function of the Total Electron Content (TEC) dayto-day variability (Hoque & Jakowski, 2008). In addition, ionospheric scintillation caused by Equatorial Plasma Bubbles (EPBs) degrades the transmission of the signal that goes from the satellite to the receiver, which can cause the loss-of-lock in the receiver (Moraes et al., 2017). Thus, the low latitude ionospheric irregularities have been widely studied in the Brazilian sector using several techniques, such as ionosonde

Signatures of Equatorial Plasma Bubbles and Ionospheric Scintillations from Magnetometer and GNSS Observations in the Indian Longitudes during the Space Weather Events of Early September 2017

“…There are several studies presenting scintillation occurrence characteristics with the help of ROTI in the equatorial, low-latitude, and sub-auroral regions, confirming that ROTI can be taken as a parametric index to identify the spatiotemporal variation of scintillations [33,[35][36][37][38]. The ROTI observations from 21 reference stations in China show its consistent relation with scintillation characteristics [39].…”

“…ROTI refers to the standard deviation of the rate of change of TEC (ROT), whose values per minute can be obtained from the slant TEC estimations following the dispersive nature of refractive ionospheres in the dual-frequency phase and pseudorange observables. Over the last two decades, the extensive analysis of scintillation indices and ROTI variations demonstrated a close relationship among the parameters [25,32,33]. Hence, it has been used by several ionospheric groups to analyze the TEC fluctuations from an adequate number of GNSS stations across the globe.…”

Equatorial Plasma Bubbles Observed at Dawn and After Sunrise Over South America During the 2015 St. Patrick's Day Storm

“…Then, if there is no Ionospheric Pierce Point (IPP) data in the area, the box is resized to 5 × 5 elements, corresponding to 2.5° × 2.5°, and so on. This method is applied up to 21 × 21 elements, corresponds to a maximum smooth of 10.5° × 10.5° (Carmo et al., 2021; Takahashi et al., 2016). The construction of ROTI maps follows the same procedure.…”

“…The EPBs are defined as plasma depletion formed by Rayleigh‐Taylor Instability (RTI) processes (Kelley, 2009). Different instruments and methodologies can be used to detect these EPBs, such as Ionosondes (Abdu et al., 2003, 2012), All‐Sky Imager (Pimenta et al., 2007; Vargas et al., 2020), total electron content (TEC) (Barros et al., 2018; Silva et al., 2019), Very High Frequency (VHF) radars (Abdu et al., 2009), scintillation index (S4) (De Paula et al., 2007; De Rezende et al., 2007), disturbance ionospheric index (DIX) (Denardini et al., 2020), and Rate Of TEC Index (ROTI) (Carmo et al., 2021; de Jesus et al., 2020). These irregularities are commonly generated after sunset (Abdu et al., 2003; Agyei‐Yeboah et al., 2021; Magdaleno et al., 2012; Vargas et al., 2020).…”

Irregularities in the African ionosphere associated with total electron content anomalies observed during high solar activity levels

“…Cherniak et al, 2015 used the ROTI to study ionospheric irregularities and observed that variations in TEC characterize ionospheric responses to disturbance. Additionally, Souza and Camango, 2019 used the ROTI to study Brazilian sector low latitude irregularities, and the ROTI suitability is presented in Carmo et al, 2021. In the American sector of low and mid latitudes, Cherniak and Zakharenkova, 2022 observed signatures of ionospheric irregularities of moderate to intense magnitude at 4 UT to 6 UT during the 25-26 August 2018 storm. Their results also documented the nighttime persistence of irregularities until sunrise at ~28 magnetic latitude.…”