Ionospheric Response Over Brazil to the August 2018 Geomagnetic Storm as Probed by CSES‐01 and Swarm Satellites and by Local Ground‐Based Observations

Abstract

The geomagnetic storm that occurred on 25 August 25 2018, that is, during the minimum of solar cycle 24, is currently the strongest ever probed by the first China Seismo‐Electromagnetic Satellite (CSES‐01). By integrating the in situ measurements provided by CSES‐01 (orbiting at altitude of 507 km) and by Swarm A satellite (orbiting at ca., 460 km) with ground‐based observations (ionosondes, magnetometers, and Global Navigation Satellite System receivers), we investigate the ionospheric response at lower‐ and mid‐latitudes over Brazil. Specifically, we investigate the electrodynamic disturbances driven by solar wind changes, by focusing on the disturbances driving modifications of the equatorial electrojet (EEJ). Our proposed multisensor technique analysis mainly highlights the variations in the topside and bottomside ionosphere, and the interplay between prompt penetrating electric fields and disturbance dynamo electric fields resulting in EEJ variations. Thanks to this approach and leveraging on the newly available CSES‐01 data, we complement and extend what recently investigated in the Western South American sector, by highlighting the significant longitudinal differences, which mainly come from the occurrence of a daytime counter‐EEJ during both 25 and 26 August at Braziliian longitudes and during part of 26 August only in the Peruvian sector. In addition, the increased thermospheric circulation driven by the storm has an impact on the EEJ during the recovery phase of the storm. The observations at the CSES‐01/Swarm altitudes integrated with the ground‐based observation recorded signatures of equatorial ionospheric anomaly crests formation and modification during daytime coupled with the positive ionospheric storm effects at midlatitude.

A measure of ionospheric irregularities: zonal velocity and its implications for L-band scintillation at low-latitudes

“…Moreover, the MTA was located inside the South Atlantic Magnetic Anomaly (SAMA), where the total magnetic field decreases. This region is characterized by a strong longitudinal dependence on low latitude electrodynamics (Abdu et al, 2005;Spogli et al, 2021) and by ionospheric irregularities' formation due to precipitating particles from the near proton belt, which may act as a further source of GNSS signal degradation (see, e.g., Spogli et al, 2013a), including Loss of Lock (Damaceno et al, 2020). Red lines in Figure 2 indicate the approximate position of the magnetic parallel and meridian passing over PRU1 as retrieved by calculating the declination angle from IGRF-12 (Thébault et al, 2015).…”

Geomagnetic Activity at Lampedusa Island: Characterization and Comparison with the Other Italian Observatories, Also in Response to Space Weather Events

“…Diurnal variation can be conveniently isolated from longer period variations by using the appropriate filter procedure. In our case, we used the moving average, which represents a simple and efficient method for identifying long trends (e.g., [22,23,34,35]). In this regard, since diurnal variations have a periodicity of 24 h (and its sub-harmonics, 12, 8, 6, 4 h, and so on), we computed the moving average over 3 days: this value is sufficient to efficiently suppress the daily variations and not too large to include sub-harmonics of 27-day Sun's synodic rotation period (see in particular [36,37]).…”

“…In this work, we applied the semi-automated procedure developed by Del Corpo et al [70] to the pair DUR-LMP to determine FLRs during two geomagnetic storms: 5-11 September 2017 [22] and 23-29 August 2018 [23]. The procedure basically searches for a maximum in the ∆φ spectra and then checks if at the same frequency the typical amplitude ratio pattern is matched.…”

“…In the following sections, secular and diurnal variations, as well as geomagnetic field variations at shorter time scales from transient phenomena such as ULF waves and geomagnetic storms, observed at Lampedusa are presented and compared with the two other Italian observatories at Castello Tesino and Duronia. In particular, two geomagnetic storms that occurred during September 2017 and August 2018 recently studied in different geographic sectors [22,23] are studied here for the first time in the Mediterranean region for providing evidence of Field Line Resonance (FLR) events on Duronia-Lampedusa intermediate field line. FLRs are a useful tool to remotely sense the plasma mass density in the inner magnetosphere, a key parameters in the space weather context.…”

Climatology of Ionospheric Amplitude Scintillation on GNSS Signals at South American Sector During Solar Cycle 24

“…ΔEEF is derived by the application of a digital filter that allows mapping the interplanetary electric field (IEF) retrieved from Advanced Composition Explorer (ACE) satellite data through a transfer function model (Manoj et al, 2008;Manoj & Maus, 2012). Such kind of approach to model EEF disturbance, supported by IMF-Bz, has been proven to be effective in enabling investigation of the role of PPEFs in the storm-time behavior of the Equatorial Electrojet (EEJ) (e.g., Spogli et al, 2020, Alfonsi et al, 2021. Moreover, AE is here used to speculate about the behavior of Joule and particle heating possibly leading to storm-time neutral winds triggering DDEFs (Yamazaki and Maute, 2017) According to Figure 5, the IMF-Bz component was flipping between positive and negative values until 05:32 UT on 01 November, remaining negative from this time until 01:08 UT on 02 November.…”