Abstract We studied the response of ionosphere ( F region) in Brazilian sector during extreme space weather event 17 March 2015 using a large network 102 GPS‐ total electron content (TEC) stations. It is observed that vertical (VTEC) was severely disturbed storm main and recovery phases. A wavelike oscillation with three peaks TEC diurnal variation from equator to low latitudes phase on 17–18 2015. The latitudinal extent decreased beginning toward phase. first peak extended beyond 0°S 30°S,...

We investigate the response of equatorial ionosphere at dusk to intense magnetic storms 30 October 2003 and 20 November 2003, different aspects which have been widely studied by community. present here a very complete set space ground‐based diagnostics that provide vertical latitudinal structures within South Atlantic anomaly (SAMA) region contiguous parts America Africa. show for both storms, sector corresponding universal time (UT) interval between fast decrease SYM‐H index minimum value...

This study presents the Global Self‐Consistent Model of Thermosphere, Ionosphere and Protonosphere (GSM TIP) numerical simulations 9–14 September 2005 geomagnetic storm effects in middle‐ low‐latitude ionosphere. Recent modifications to GSM TIP model include adding an empirical high‐energy electron precipitation introducing a high‐resolution (1 min) calculation region 2 field‐aligned currents cross‐cap potential difference. These resulted better representation such as penetration...

Abstract The St. Patrick's Day storm of 17 March 2015 has a long‐lasting main phase with the Dst reaching minimum −223 nT. During phase, two strong prompt penetration electric field (PPEF) phases took place; first southward turning IMF Bz around ~1200 UT and second onset substorm ~1725 leading to equatorial zonal enhancements. consequent spatiotemporal disturbances in ionospheric total electron content resultant modifications ionization anomaly (EIA) over Brazilian longitudinal sector are...

Abstract The equatorial electrojet (EEJ) is a narrow band of current flowing eastward at the ionospheric E region altitudes along dayside dip equator. Mutually perpendicular electric and magnetic fields over equator results in formation ionization anomaly (EIA), which turn generates large electron density variabilities. Simultaneous study on characteristics EEJ EIA necessary to understand role This helpful for improved estimation total content (TEC) range delays required satellite‐based...

This paper presents a study of thermospheric and ionospheric response to the 2008 minor sudden stratospheric warming (SSW) event. period was characterized by low solar geomagnetic activity. The performed using Global Self‐consistent Model Thermosphere, Ionosphere, Protonosphere (GSM TIP). results were compared with ionosonde data from Irkutsk, Kaliningrad, Sao Jose dos Campos, Jicamarca. SSW event modeled specifying temperature density perturbations at lower boundary GSM TIP (80 km...

The intense modifications in the ionosphere‐thermosphere system equatorial and low‐latitude regions associated with dynamic electrodynamic coupling from high to low latitudes chemical changes during geomagnetic storms are important space weather issues. In second half of October 2003, solar activity resulted one two major on 29 30 October. this paper we present discuss ionospheric sounding observations carried out Palmas São José dos Campos, Brazil (the Brazilian sector), Ho Chi Minh City,...

Ionospheric vertical sounding observations, using a digital ionosonde, are being carried out on routine basis at Sao Jose dos Campos (23.2°S, 45.9°W; dip latitude 17.6°S, hereafter referred to as SJC), Brazil, located under the southern crest of equatorial ionization anomaly (EIA), since August 2000. In this paper, we present and discuss seasonal variation gravity wave (GW) traveling ionospheric disturbance (TID) oscillations in F 2 layer during high solar activity (HSA, September 2000 2001)...

[1] In this paper, we report a long-term study of medium-scale traveling ionospheric disturbance (MSTID) occurrence using all-sky images O I 630 nm airglow emission. Our is based on 10.5 year data series in which 5.5 years compound new set. The were obtained by an imager installed at Cachoeira Paulista (22.7°S, 45°W, 15°S magnetic latitude). results show the greatest MSTIDs during solar minimum and minor rate descending ascending activity periods. During maximum, have not detected MSTID...

Abstract It is known that the equatorial and low‐latitude ionosphere characterized with typical dynamical phenomena namely, ionization anomaly (EIA). Accurate modeling of characteristic variations EIA more important to arrive at correct estimation range delays required for communication navigation applications. The total electron content (TEC) data from a chain Global Positioning System (GPS) receivers seven identified locations equator crest beyond along 315°E geographic longitude in...

Abstract The present study investigates the ionospheric total electron content (TEC) and F‐layer response in Southern Hemisphere equatorial, low, middle latitudes due to major sudden stratospheric warming (SSW) event, which took place during January–February 2009 Northern Hemisphere. In this study, using 17 ground‐based dual frequency GPS stations two ionosonde spanning from 2.8°N 53.8°S, longitudes 36.7°W 67.8°W over South American sector, it is observed that ionosphere was significantly...

Abstract There are growing concerns about the effect of solar flares on ionosphere, mainly due to possible deterioration or damage our communication and navigation satellite systems. On 3 July 2021, 28 October there were (SFs) classified as X1.59 X1.0, respectively. These two SFs only ones X‐class that occurred during last low activity (LSA:2018–2021). Data from magnetometers Global Positioning System (GPS)—Total Electron Content (TEC) used investigate spatial‐temporal electrodynamics...

A digital ionosonde of the type known as Canadian Advanced Digital Ionosonde (CADI) is operational at São José dos Campos (23.2°S, 45.9°W), Brazil. This ionospheric sounding station located under southern crest equatorial anomaly. The F layer electron density profile presents considerable day‐to‐day variability, even during undisturbed conditions, and this variability still one less understood aspects physics ionosphere. propagation waves into ionosphere may play an important role in...

Abstract. In this work, the F-region critical frequency (foF2) and peak height (hmF2) measured by digital ionosondes at two Brazilian low-latitude stations, namely Palmas (10.17° S, 48.20° W, dip –10.80°) São José dos Campos (23.20° 45.86° –38.41°), are compared with IRI-2001 model predictions. The comparison latter station shows quite a reasonable agreement for both parameters. former exhibits better hmF2 than foF2. general, generates good results, although some improvements still necessary...

Ionospheric vertical sounding observations are being carried out at Sao Jose dos Campos (23.2°S, 45.9°W; dip latitude 17.6°S), Brazil, under the southern crest of equatorial ionization anomaly (EIA) since August 2000. In this paper, we present and discuss daytime F2‐layer stratification near EIA, for first time, magnetically quiet high solar activity conditions. Three examples a year statistics presented. The F3‐layer were observed between 10:40 11:45 UT on 31 December 2000, 13:30 14:30 1...

We present recent observations of Sudden Phase Anomalies due to subionospheric propagation anomalies produced by solar X‐ray flares. use the new South America VLF Network (SAVNET) study 471 ionospheric events flares during period May 2006 July 2009 which corresponds minimum activity. For this activity level, we find that 100% with a peak flux above 5 × 10 −7 W/m 2 in 0.1–0.8 nm wavelength range produce significant disturbance, while needed do so is about 2.7 . latter threshold dependent on...

The main purpose of this investigation is to study the ionospheric F region response induced by intense geomagnetic storm that occurred on 7–8 September 2002. index Dst reached a minimum −181 nT at 0100 UT 8 September. In study, we used observations from chain 12 GPS stations and another 6 digital ionosonde stations. It should be mentioned that, soon after sudden commencement (SC) 1637 7 September, TEC variations midlatitude in both hemispheres showed an positive phase. However, during...