Bibliography

Response of the Ionospheric TEC to SSW and Associated Geomagnetic Storm Over the American Low Latitudinal Sector

During the sudden stratospheric warming (SSW) event in 2013, we investigated the American low latitude around 75°W. We used 12 Global Positioning System (GPS) receivers, a pair of magnetometers, and the NASA Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite airglow instrument to unveil the total electron content (TEC), inferred vertical drift, and the changes in the neutral composition, respectively. A major SSW characterized the 2013 SSW event with the main phase (7–27 January 2013) overlapped by a minor geomagnetic storm (17 January 2013). The late morning inferred downward-directed E X B drift did not support the varying equatorial ionization anomaly (EIA) signature during the SSW onset (7 January 2013). The mid-January (15–16 January 2013) witnessed enhancement in the varying inferred upward-directed E X B drift at both hemispheres. On 17 January 2013, there were reductions in the varying inferred upward-directed E X B drift at both hemispheres. Generally, the SSW effect on TEC around 15–16 January 2013 is more pronounced than the SSW onset. During the mid-January (15–16 January 2013), the higher northern EIA crests are facilitated majorly by the SSW compared to the photo-ionization that primarily enabled the southern crests. On 17 January 2013, the combined effect of photo-ionization and SSW contribution was majorly responsible for the slight reduction in the northern crest. In the southern hemisphere, photo-ionization played the lead role as the SSW, and the minor geomagnetic storm roles are secondary in enhancing the southern crest.

Fashae, J.; Bolaji, O.; Rabiu, A.;

Published by: Space Weather      Published on:

YEAR: 2022     DOI: 10.1029/2021SW002999

equatorial ionization anomaly (EIA); geomagnetic storm; low-latitude ionosphere; sudden stratospheric wind (SSW)

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

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.

Spogli, L.; Sabbagh, D.; Regi, M.; Cesaroni, C.; Perrone, L.; Alfonsi, L.; Di Mauro, D.; Lepidi, S.; Campuzano, S.; Marchetti, D.; De Santis, A.; Malagnini, A.; Scotto, C.; Cianchini, G.; Shen, Xu; Piscini, A.; Ippolito, A.;

Published by: Journal of Geophysical Research: Space Physics      Published on:

YEAR: 2021     DOI: 10.1029/2020JA028368

Geomagnetic storms; Equatorial Electrojet; in situ plasma density; ionospheric elctroduamics; Ionospheric storms; low-latitude ionosphere

Effects of prolonged southward interplanetary magnetic field on low-latitude ionospheric electron density

The present work describes the low-latitude ionospheric variability during an unusually prolonged (~33 h) geomagnetically disturbed condition that prevailed during 15\textendash16 July 2012. The low-latitude electron density in summer hemisphere, investigated using ground- and satellite-based observations, responded to this by generating strong negative ionospheric storm on 16 July. The maximum electron density on 16 July over Indian low latitudes was reduced by more than 50\% compared to that on a geomagnetically quiet day (14 July 2012). In contrast to the extreme reduction in total electron content (TEC) in the Northern Hemisphere, TEC from a winter hemispheric station revealed substantial (~23 total electron content unit, 1 TECU = 10¹⁶ el m^-2) enhancements on the same day. This contrasting hemispherical response in TEC is suggested to be due to the combined effects of strong interhemispheric and solar-driven day-night winds. Further, very weak equatorial electrojet (EEJ) strength on 16 July indicated that the westward electric field perturbations in the low-latitude ionosphere were possibly due to the disturbance dynamo effect associated with meridional circulation from polar to equatorial latitudes. Interestingly, despite reduction in the integrated EEJ strength on 15 July, the low-latitude electron density showed substantial enhancement, highlighting the significant effect of the positive ionospheric storm on the low-latitude ionosphere. The roles of electrodynamical/neutral-dynamical and compositional disturbances are discussed in view of these observations to understand low-latitude ionospheric response when geomagnetic disturbance persists for longer duration.

Bagiya, Mala; Hazarika, Rumajyoti; Laskar, Fazlul; Sunda, Surendra; Gurubaran, S.; Chakrabarty, D.; Bhuyan, P.; Sridharan, R.; Veenadhari, B.; Pallamraju, D.;

Published by: Journal of Geophysical Research: Space Physics      Published on: 07/2014

YEAR: 2014     DOI: 10.1002/2014JA020156

low-latitude ionosphere; neutral winds; prolonged southward IMF Bz; thermospheric neutral composition

Modeling storm-time electrodynamics of the low-latitude ionosphere–thermosphere system: Can long lasting disturbance electric fields be accounted for?

Storm-time ionospheric disturbance electric fields are studied for two large geomagnetic storms, March 31, 2001 and April 17–18, 2002, by comparing low-latitude observations of ionospheric plasma drifts with results from numerical simulations based on a combination of first-principles models. The simulation machinery combines the Rice convection model (RCM), used to calculate inner magnetospheric electric fields, and the coupled thermosphere ionosphere plasmasphere electrodynamics (CTIPe) model, driven, in part, by RCM-computed electric fields. Comparison of model results with measured or estimated low-latitude vertical drift velocities (zonal electric fields) shows that the coupled model is capable of reproducing measurements under a variety of conditions. In particular, our model results suggest, from theoretical grounds, a possibility of long-lasting penetration of magnetospheric electric fields to low latitudes during prolonged periods of enhanced convection associated with southward-directed interplanetary magnetic field, although the model probably overestimates the magnitude and duration of such penetration during extremely disturbed conditions. During periods of moderate disturbance, we found surprisingly good overall agreement between model predictions and data, with penetration electric fields accounting for early main phase changes and oscillations in low-latitude vertical drift, while the disturbance dynamo mechanism becomes increasingly important later in the modeled events. Discrepancies between the model results and the observations indicate some of the difficulties in validating these combined numerical models, and the limitations of the available experimental data.

Maruyama, Naomi; Sazykin, Stanislav; Spiro, Robert; Anderson, David; Anghel, Adela; Wolf, Richard; Toffoletto, Frank; Fuller-Rowell, Timothy; Codrescu, Mihail; Richmond, Arthur; Millward, George;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on:

YEAR: 2007     DOI: https://doi.org/10.1016/j.jastp.2006.08.020

Magnetosphere–ionosphere–thermosphere coupling; Ionospheric electrodynamics; low-latitude ionosphere; Penetration electric fields; disturbance dynamo electric fields; Numerical modeling

Nighttime F-region morphology in the low and middle latitudes seen from DMSP F15 and TIMED/GUVI

We investigate the seasonal, longitudinal, and altitudinal variations of the FF-region morphology at 2100\textendash2300\ LT in the low- and middle-latitudes using the data collected in August, September, and November of 2003. The topside morphology is investigated using in situ measurements of the O⁺O+ fraction and total ion density by the Defense Meteorological Satellite Program (DMSP) F15 satellite. The morphology of the equatorial ionization anomaly (EIA) near the FF peak altitude is investigated using the OI 135.6-nm radiance maps provided by the Global Ultraviolet Imager (GUVI) on board the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite. The hemispheric asymmetries of the topside ionosphere at 840\ km in the months near solstices can be characterized by the reduction of the O⁺O+ fraction and ion density in the winter hemisphere compared to those in the summer hemisphere. The minimum O⁺O+ fraction and ion density layers occur around 30^o30o magnetic latitude in the winter hemisphere. During the fall equinox, the hemispheric asymmetries are reversed in the regions of opposite magnetic declinations. From the comparison of the topside morphology with the global wind circulation pattern at 2200\ LT predicted by the Horizontal Wind Model 93 (HWM93) we infer that hemispheric asymmetry of the topside ionosphere is created primarily by the retardation of the downward plasma diffusion in one hemisphere through the field-aligned equatorward winds. The global EIA morphology does not conform to the topside morphology. The complex seasonal-longitudinal variations of the EIA strength and asymmetry are not explained simply by considering the modulation of the FF-layer height by the winds. The magnetic declination is not a useful tool in understanding the global EIA morphology.

Kil, Hyosub; DeMajistre, Robert; Paxton, L.; Zhang, Yongliang;

Published by: Journal of Atmospheric and Solar-Terrestrial Physics      Published on: 09/2006

YEAR: 2006     DOI: 10.1016/j.jastp.2006.05.024

Equatorial ionization anomaly; FF-region plasma distribution; low-latitude ionosphere; Neutral wind

Retrievals of nighttime electron density from Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission Global Ultraviolet Imager (GUVI) measurements

In this work we will present a method for retrieving nighttime electron density profiles from OI 135.6 nm limb emissions measured by the Global Ultraviolet Imager (GUVI) aboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission spacecraft. The primary mechanism for 135.6 nm radiance in the nighttime thermosphere is recombination of O⁺ ions, and the volume emission rate is approximately proportional to the square of the electron density. Herein we describe a two-step inversion method in which we first determine the volume emission rate as a function of altitude from the radiance measurements and then use the inferred volume emission rates to determine the electron density profile. There are two important factors that we have addressed in constructing the retrieval algorithms for this problem. First, the GUVI instrument was primarily designed for day side measurements. Consequently, the signal levels on the night side are very low, and our retrieval algorithms must therefore be able to function in regions where the signals are weak. Second, since we must take the square root of the volume emission rate, it must be everywhere positive in order for the electron density to be deduced. For this reason, we have imposed nonnegativity constraints (using the methods described by Menke [1989]) on what might otherwise be discrete linear retrievals of volume emission rate. After describing the retrieval method we present an error analysis and a preliminary comparison with coincident measurements by incoherent scatter radars (ISRs). In general, the retrieved electron densities from the GUVI data agree well with the ISR data, although more coincident measurements would increase our confidence in the resulting electron density profiles.

DeMajistre, R.; Paxton, L.; Morrison, D.; Yee, J.-H.; Goncharenko, L.; Christensen, A.;

Published by: Journal of Geophysical Research      Published on: 04/2004

YEAR: 2004     DOI: 10.1029/2003JA010296

Electron density; inversion; low-latitude ionosphere; TIMED/GUVI