Bibliography

Investigation of the negative ionospheric response of the 8 September 2017 geomagnetic storm over the European sector

In this study, we investigate the negative ionospheric response over the European sector during two storms that took place on 8 September 2017, primarily, by exploiting observations over ten European locations. The spatial and temporal variations of TEC, foF2 and hmF2 ionospheric characteristics are examined with the aim to explain the physical mechanisms underlying the strong negative ionospheric response. We detected very sharp electron density (in terms of foF2 and TEC) decrease during the main phases of the two storms and we attributed this phenomenon to the large displacement of the Midlatitude Ionospheric Trough (MIT). Our study also revealed that the two storms show different features caused by different processes. In addition, Large Scale Traveling Ionospheric Disturbances (LSTIDs) were observed during both storms, followed by enhanced Spread F conditions over Digisonde stations. The regional dependence of ionospheric storm effects was demonstrated, as the behavior of ionospheric effects over the northern part of Europe differed from that over the southern part.

Oikonomou, Christina; Haralambous, Haris; Paul, Ashik; Ray, Sarbany; Alfonsi, Lucilla; Cesaroni, Claudio; Sur, Dibyendu;

Published by: Advances in Space Research      Published on: aug

YEAR: 2022     DOI: 10.1016/j.asr.2022.05.035

Large-scale traveling ionospheric disturbances; Mid-latitude ionospheric trough; September 2017 geomagnetic storm; Swarm satellite

Multi-wavelength coordinated observations of ionospheric irregularity structures from an anomaly crest location during unusual solar minimum of the 24th cycle

The present paper reports coordinated ionospheric irregularity measurements at optical as well as GPS wavelengths. Optical measurements were obtained from Tiny Ionospheric Photometer (TIP) sensors installed onboard the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites. GPS radio signals were obtained from a dual frequency GPS receiver operational at Calcutta (22.58\textdegreeN, 88.38\textdegreeE geographic; geomagnetic dip: 32.96\textdegree; 13.00\textdegreeN, 161.63\textdegreeE geomagnetic) under the SCIntillation Network Decision Aid (SCINDA) program. Calcutta is located near the northern crest of Equatorial Ionization Anomaly (EIA) in the Indian longitude sector. The observations were conducted during the unusually low and prolonged solar minima period of 2008\textendash2010. During this period, four cases of post-sunset GPS scintillation were observed from Calcutta. Among those cases, simultaneous fluctuations in GPS Carrier-to-Noise ratios (C/N_o) and measured radiances from TIP over a common ionospheric volume were observed only on February 2, 2008 and September 25, 2008. Fluctuations observed in measured radiances (maximum 0.95 Rayleigh) from TIP due to ionospheric irregularities were found to correspond well with C/N₀ fluctuations on the GPS links observed from Calcutta, such effects being noted even during late evening hours of 21:00\textendash22:00 LT from locations around 40\textdegree magnetic dip. These measurements indicate the existence of electron density irregularities of scale sizes varying over several decades from 135.6\ nm to 300\textendash400\ m well beyond the northern crest of the EIA in the Indian longitude sector during late evening hours even in the unusually low solar activity conditions.

Paul, Ashik; Sur, Dibyendu; Haralambous, Haris;

Published by: Advances in Space Research      Published on: 03/2020

YEAR: 2020     DOI: 10.1016/j.asr.2019.11.035

GPS radio measurements; ionospheric irregularities; Northern crest of EIA; Optical measurements; solar minimum; TIP

Characteristics of post-midnight L-band scintillation in the transition region from the equatorial to mid-latitudes over the Indian longitude sector using COSMIC, C/NOFS and GPS measurements

Occurrence of L band scintillations around midnight and postmidnight hours have not been well studied and reported from the higher equatorial latitudes in the transition region from the equatorial to midlatitudes over the Indian longitude sector. The present paper reports cases of postmidnight L band scintillation observations by COSMIC during March 2014 over the Indian longitude sector. GPS\ S₄measurements from the International Global Navigation Satellite Systems Service station at Lucknow (26.91\textdegreeN, 80.96\textdegreeE geographic; magnetic dip: 39.75\textdegreeN) corroborate occurrence of postmidnight scintillations. The\ F\ region vertical upward velocities around the magnetic equator during evening hours have been used to understand the possibility of impact of irregularities generated over the magnetic equator at latitudes north of 30\textdegreeN. Postmidnight L band scintillations at latitudes greater than 30\textdegreeN without corresponding premidnight scintillations present interesting scientific scenario and give rise to suggestions of (1) any coupling mechanism between the equatorial and midlatitudes through which irregularities seeded in the midlatitudes may affect transionospheric satellite links at low latitudes or (2) irregularity generation at midlatitudes not connected with equatorial instabilities. Long-term analysis of\ S₄\ at L band measured by COSMIC over the Indian longitudes during March 2007\textendash2014 exhibits a well-defined longitude swath around 75\textendash83\textdegreeE of reduced (0.2 \< S₄ \< 0.4) or no scintillations which may be attributed to the longitudinal variability of scintillation occurrence following the global four-cell pattern of ionospheric activity.

Paul, A.; Haralambous, H.; Oikonomou, C.;

Published by: Radio Science      Published on: 12/2015

YEAR: 2015     DOI: 10.1002/2015RS005807

postmidnight L band scintillation over Indian longitude sector

Characteristics of postmidnight L band scintillation in the transition region from the equatorial to midlatitudes over the Indian longitude sector using COSMIC, C/NOFS, and GPS measurements

Paul, A; Haralambous, H; Oikonomou, C;

Published by: Radio Science      Published on:

YEAR: 2015     DOI: