Investigation on<i>F</i>layer height rise and equatorial spread<i>F</i>onset time: Signature of standing large-scale wave

Joshi, L. M.; Balwada, S.; Pant, Tarun Kumar; Sumod, S. G.

doi:10.1002/2014sw001129

Cited by 16 publications

(14 citation statements)

References 34 publications

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“…It can be noted that the peak h′F was 558 km on 17 March, which is 200 km more than that on 16 March. Peak h′F in the range of 360–420 km over magnetic equator in the Indian sector during geomagnetically quiet days represents a very high degree of post sunset height rise [ Joshi et al , ]. Thus, the intense increase in the E × B drift after 17:30 IST on 17 March and the associated rise of the F layer were a direct outcome of the penetration of the high‐latitude electric field on the equatorial region.…”

Section: Resultsmentioning

confidence: 99%

Simulation of low‐latitude ionospheric response to 2015 St. Patrick's Day super geomagnetic storm using ionosonde‐derived PRE vertical drifts over Indian region

2016

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In this paper, we present low‐latitude ionospheric response over Indian longitude to the recent super geomagnetic storm of 17 March 2015, using the Sami2 is Another Model of the Ionosphere (SAMI2) model which incorporates ionosonde‐derived vertical drift impacted by prompt penetration eastward electric field occurring during the evening prereversal enhancement (PRE) in the vertical drift. The importance of this storm is that (1) Dst reaches as low as −228 nT and (2) prompt penetration of eastward electric field coincided with evening hours PRE. The daytime vertical E × B drifts in the SAMI2 model are, however, considered based on Scherliess‐Fejer model. The simulations indicate a significant enhancement in F layer height and equatorial ionization anomaly (EIA) in the post sunset hours on 17 March 2015 vis‐a‐vis quiet day. The model simulations during recovery phase, considering disturbance dynamo vertical E × B drift along with equatorward disturbance wind, indicate suppression of the daytime EIA. SAMI2 simulations considering the disturbance wind during the recovery phase suggest that equatorward wind enhances the ionospheric density in the low latitude; however, its role in the formation of the EIA depends on the polarity of the zonal electric field. Comparison of model derived total electron content (TEC) with the TEC from ground GPS receivers indicates that model does reproduce enhancement of the EIA during the main phase and suppression of the EIA during the recovery phase of the superstorm. However, peculiarities pertaining to the ionospheric response to prompt penetration electric field in the Indian sector vis‐a‐vis earlier reports from American sector have been discussed.

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Section: Resultsmentioning

confidence: 99%

Simulation of low‐latitude ionospheric response to 2015 St. Patrick's Day super geomagnetic storm using ionosonde‐derived PRE vertical drifts over Indian region

2016

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“…Especially, the development of low‐latitude density irregularity is mainly controlled by the perturbations of the zonal electric field at the equator. The zonal electric field is generally eastward (westward) during daytime (nighttime), forming vertical drifts that cause the equatorial ionosphere to rise (fall) (e.g., Joshi et al, ). The most important part of the zonal electric field is its enhancement near the solar terminator and early evening sectors which is characterized by prereversal enhancements (Fejer et al, ; Dubazane & Habarulema, , and references therein).…”

Section: Electric Field and Vertical Driftsmentioning

confidence: 99%

Longitudinal and Seasonal Variability of Equatorial Ionospheric Irregularities and Electrodynamics

Yizengaw

Groves

2018

Space Weather

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Over the past decades significant progresses have been done to understand the origin of seeding mechanisms of ionospheric irregularities. However, characterization of the global ionospheric irregularities as a function of local time, longitude, and season is still a challenge for the modeling community. In this review paper, using multiinstrument observations, we investigated the global irregularity distribution and its possible drivers that control the longitudinal and seasonal dependences. We demonstrated that forcing from lower thermosphere, like the localized tropospheric gravity waves seeding, may be responsible for the formation of strong longitudinal dependence of irregularity distribution. The location of Intertropical Convergence Zone that generate forceful thunderstorms and become favorable location for the launch of localized gravity waves may play an important role in the longitudinal dependence of irregularity distribution. Hence, incorporating the Intertropical Convergence Zone location into density irregularity modeling effort may provide important information to understand and characterize the longitudinal variability of irregularity distributions.Plain Language Summary The two major coupling processes, namely, (1) the vertical coupling that involves upward propagating atmospheric waves (forcing from below) and (2) magnetosphere-ionosphere coupling (forcing from above), cause for the initiation and development of ionospheric density irregularities that create favorable conditions for the creation of rapid amplitude and phase fluctuations of radio signals. On the other hand, application of radio wave is essential for our communication and navigation systems, either transmitted through the ionosphere for satellite communication and navigation or reflected off the ionosphere for HF and radar applications. This indicates that ionospheric density irregularities are as much an engineering concern as they are a scientific quest. The ionospheric irregularities, which are also not uniform globally, affect the integrity and performance of navigation and communication systems with different magnitudes at different longitudes. Hence, understanding the physics behind the longitudinal variability of equatorial ionospheric irregularities is essential to characterize and develop a model that can accurately capture the global distribution of ionospheric irregularities and its driving mechanisms.

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“…Such seed or triggering perturbations are sometimes provided by gravity waves (Hysell et al, ; Krall et al, ), by spatially varying electric fields (C.‐S. Huang & Kelley, ), or by large‐scale wave structures on the bottomside of F‐region (Joshi et al, ; Tsunoda, ). A radio wave signal undergoes phase and amplitude scintillations while traversing through such irregular medium of varying refractive index (Yeh & Liu, ).…”

Section: Introductionmentioning

confidence: 99%

“…Although these ambient favorable conditions are present everyday in the postsunset hours, the generation of ESF irregularities is not seen on every day due to variation in amplitudes and scale size of the seed perturbation (Sekar et al, 1995). Such seed or triggering perturbations are sometimes provided by gravity waves (Hysell et al, 1990;Krall et al, 2013), by spatially varying electric fields (C.-S. Huang & Kelley, 1996), or by large-scale wave structures on the bottomside of F-region (Joshi et al, 2015;Tsunoda, 2012). A radio wave signal undergoes phase and amplitude scintillations while traversing through such irregular medium of varying refractive index (Yeh & Liu, 1982).…”

Section: Introductionmentioning

confidence: 99%

Evolution of Freshly Generated Equatorial Spread F (F‐ESF) Irregularities on Quiet and Disturbed Days

et al. 2018

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We examined the seasonal and solar flux dependence of the occurrence of freshly generated intermediate scale (100 m to few km) equatorial spread F (ESF) irregularities during magnetically quiet (Q) and disturbed (D) periods. We utilized long‐term (1992–2006 and 2013–2015) amplitude scintillation data on a 251 MHz signal recorded at Tirunelveli (dip lat. 1.5°N ). Also, ionosonde data (1990–2003) recorded at Trivandrum (dip lat. 0.5°N) are used. The presence of fresh ESF (F‐ESF) is identified using the maximum cross‐correlation between intensity variations recorded by two spaced receivers on a magnetic east‐west baseline. We find distinct differences in the seasonal and solar flux dependence of the usual postsunset (<22 LT) generation of F‐ESF on both Q‐ and D‐days. Interesting feature is that F‐ESF linked moderate–strong scintillations are more prevalent on D‐days as compared to Q‐days in both early (18–22 LT) and later (>22 LT) phase of evolution of the irregularities. It directly hints toward the difference in the spatial structuring (spatial scales) of F‐ESF on D‐days as compared to Q‐days. On D‐days, the occurrence of F‐ESF is more likely around midnight and early‐morning hours in all seasons. Whereas on Q‐days, the postmidnight F‐ESF is found to occur mainly during solstices of low solar activity. The possible sources for the generation of F‐ESF around midnight on Q‐days of solstices during low solar activity are examined. We also find that perturbation electric field linked with F‐ESF on D‐days sustains for longer time, which results in longer durations of the active phase of equatorial plasma bubbles.

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Investigation onFlayer height rise and equatorial spreadFonset time: Signature of standing large-scale wave

Cited by 16 publications

References 34 publications

Simulation of low‐latitude ionospheric response to 2015 St. Patrick's Day super geomagnetic storm using ionosonde‐derived PRE vertical drifts over Indian region

Simulation of low‐latitude ionospheric response to 2015 St. Patrick's Day super geomagnetic storm using ionosonde‐derived PRE vertical drifts over Indian region

Longitudinal and Seasonal Variability of Equatorial Ionospheric Irregularities and Electrodynamics

Evolution of Freshly Generated Equatorial Spread F (F‐ESF) Irregularities on Quiet and Disturbed Days

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