Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 &amp;quot;Halloween Storms&amp;quot;

Sahai, Y.; Becker‐Guedes, F.; Fagundes, P. R.; Abreu, A. J. de; Jesús, R. de; Pillat, V. G.; Abalde, J. R.; Martinis, C. R.; Brunini, C.; Gende, Mauricio; Huang, Chao-Tsung; Pi, Xiaoqing; Lima, W. L. C.; Bittencourt, J. A.; Otsuka, Yuichi

doi:10.5194/angeo-27-4463-2009

Cited by 26 publications

(18 citation statements)

References 53 publications

(46 reference statements)

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“…So the focus is to find the responses of VTEC during that particular period of time when the disturbed wind from the polar regions would not have reached the low latitudes as corroborated in many previous studies (Bauske & Prölss, 1997;Dashora et al, 2009;Ding et al, 2007;Hajkowicz, 1990;Hocke & Schlegel, 1996;Hunsucker, 1982;Nicolls et al, 2004). These results are in conformity with results presented by Sahai et al (2009) including detailed analysis of this storm from South American sector. The recent simulation results also indicate that simultaneous quantification of respective magnitudes of the background winds, electric field, and their perturbation components during the MP remains an open scope of research.…”

Section: Resultssupporting

confidence: 83%

“…Journal of Geophysical Research: Space Physics from BOGT and CORD (and elsewhere), albeit with different magnitudes and at different times (Sahai et al, 2009). While peaks over BOGT are observed at 20 and 21 UT, over UNSA they are seen about 18.5 UT and at about 21.5 UT and over CORD at about 21 and 22 UT.…”

Section: 1029/2019ja026671mentioning

confidence: 79%

“…Also, as shown in the previous case of 17 August 2001, simultaneous peaks in VTEC at 16 and 20 UT highlighted the role of PPEF and associated asymmetry. A typical LSTID traveling with mean speed of about 600 m/s may arrive at low latitudes with a delay of 4 hr and can produce sequential equatorward peaks in VTEC (Lu et al, 2012;Sahai et al, 2009). VTEC observations While GIM VTEC shows maximum VTEC with lesser values than the observations before 18 UT, the observations peak after 20 UT depicting average nature of GIM VTEC.…”

Section: August 2005mentioning

confidence: 86%

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Interhemispheric Asymmetry in Response of Low‐Latitude Ionosphere to Perturbation Electric Fields in the Main Phase of Geomagnetic Storms

2019

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Structures of sudden enhancements/depressions and associated interhemispheric asymmetry in low‐latitude total electron content (TEC) during the main phase (MP) of geomagnetic storms have remained unpredictable majorly due to oscillating equatorial vertical E×B drifts and resultant redistribution of plasma in low latitudes in a given seasonal background. Robust analysis of 7 major and 30 moderate ionospheric storms during the years 2000–2018 is performed with comprehensive literature review encompassing various sources of asymmetry in magnetosphere‐ionosphere coupling. Taking advantage of simultaneous long‐term observations of E×B drift from Jicamarca, H component from magnetometers, and global ionospheric map vertical TEC (VTEC) and TEC observations across the dip equator from the South American sector, simultaneous formation of peaks and valleys in VTEC and associated asymmetry are studied. Additionally, a three‐layer neural network‐based E×B drift model is developed using delta‐H observations that provide drift estimates in the absence of Jicamarca drifts. The main results establish simultaneous high‐magnitude short‐lived (1–2 hr) enhancements and depression in VTEC during the MP in daytime in both hemispheres with varying differences of −30 to 100 TECU with respect to quiet time mean and along with prominent existence of interhemispheric asymmetry in TEC during the MP regardless of seasons. Maximum VTEC in the northern and southern low latitudes is found to occur at different times during storms. Large difference of VTEC is found ranging between 10 and 30 TECU between the near conjugate locations of the hemispheres. Coincident global episodic peaks marked by steep VTEC falls show dominance of episodic eastward and westward penetration electric fields in the low‐latitude daytime ionosphere.

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Section: Resultssupporting

confidence: 83%

Section: 1029/2019ja026671mentioning

confidence: 79%

Section: August 2005mentioning

confidence: 86%

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Interhemispheric Asymmetry in Response of Low‐Latitude Ionosphere to Perturbation Electric Fields in the Main Phase of Geomagnetic Storms

2019

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“…In some cases, the irregularities occur and intensify while in some other cases they are inhibited (Aarons, ). During the Halloween super storms on 29–30 October, 2003, Sahai et al () reported that plasma bubbles are generated at the equator and extended to ~33°S magnetic latitudes in South American sector, which maps to ~2500 km over the equator. Tulasi Ram et al () who studied the irregularities in Indian sector during five storms reported intensification in some cases and inhibition in other cases.…”

Section: Ionospheric Irregularitiesmentioning

confidence: 99%

A brief review of equatorial ionization anomaly and ionospheric irregularities

Balan

Liu

2018

Earth and Planetary Physics

168

124

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Following a brief history and progress of ionospheric research, this paper presents a brief review of the recent developments in the understanding of two major phenomena in low and mid latitude ionosphere—the equatorial ionization anomaly (EIA) and involved equatorial plasma fountain (EPF) and ionospheric irregularities. Unlike the easy‐to‐understand misinterpretations, the EPF involves field perpendicularE×B plasma drift and field‐aligned plasma diffusion acting together and plasma flowing in the direction of the resultant at all points along the field lines at all altitudes. The EIA is formed mainly from the removal of plasma from around the equator by the upward E×B drift creating the trough and consequently the crests with small accumulation of plasma at the crests when the crests are within ~±20° magnetic latitudes and no accumulation when they are beyond ~±25° magnetic latitudes. The strong EIA under magnetically active conditions arises from the simultaneous impulsive action of eastward prompt penetration electric field and equatorward neutral wind. Intense ionospheric irregularities develop in the post‐sunset bottom‐side equatorial ionosphere when it rises to high altitudes, and evolve nonlinearly into the topside. Pre‐reversal enhancement (PRE) of the vertical upward E×B drift and its fluctuations amplified during PRE provide the driving force and seed, with neutral wind and gravity waves being the primary sources. At low solar activity especially in summer when fast varying PRE is absent, the slow varying gravity waves including large scale waves (LSW) seem to act as both driver and seed for weak irregularities. At mid latitudes, the irregularities are weak and associated with medium scale traveling ionospheric disturbances (MSTIDs). A low latitude minimum in the occurrence of the irregularities at March equinox predicted by theoretical models is identified. The minimum occurs on the poleward side of the EIA crest and shifts equatorward from ~25° magnetic latitudes at high solar activity to below 17° at low solar activity.

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“…The generation or suppression of ESF has been studied by several investigators (e.g., Sahai et al, 1998Sahai et al, , 2009aWhalen, 2002;Abdu et al, 2003;Tsurutani et al, 2004;Martinis et al, 2005;de Abreu et al, 2010) during geomagnetic storm. As described by Kelley et al (2006), ESF can also be termed as "Convective Ionospheric storms" taking the analogy of the ionospheric process to thunderstorm.…”

Section: Introductionmentioning

confidence: 99%

Effects observed in the ionospheric F-region in the South American sector during the intense geomagnetic storm of 14 December 2006

Jesús

Sahai

Guarnieri

et al. 2010

Advances in Space Research

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Observations of the F-region ionospheric irregularities in the South American sector during the October 2003 "Halloween Storms"

Cited by 26 publications

References 53 publications

Interhemispheric Asymmetry in Response of Low‐Latitude Ionosphere to Perturbation Electric Fields in the Main Phase of Geomagnetic Storms

Interhemispheric Asymmetry in Response of Low‐Latitude Ionosphere to Perturbation Electric Fields in the Main Phase of Geomagnetic Storms

A brief review of equatorial ionization anomaly and ionospheric irregularities

Effects observed in the ionospheric F-region in the South American sector during the intense geomagnetic storm of 14 December 2006

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