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Journal articles on the topic 'Equatorial spread F'

Author: Grafiati

Published: 6 September 2023

Last updated: 15 June 2025

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1

Becker-Guedes, F., Y. Sahai, P. R. Fagundes, et al. "Geomagnetic storm and equatorial spread-F." Annales Geophysicae 22, no. 9 (2004): 3231–39. http://dx.doi.org/10.5194/angeo-22-3231-2004.

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Abstract. In August 2000, a new ionospheric sounding station was established at Sao Jose dos Campos (23.2° S, 45.9° W; dip latitude 17.6° S), Brazil, by the University of Vale do Paraiba (UNIVAP). Another ionospheric sounding station was established at Palmas (10.2° S, 48.2° W; dip latitude 5.5° S), Brazil, in April 2002, by UNIVAP in collaboration with the Lutheran University Center of Palmas (CEULP), Lutheran University of Brazil (ULBRA). Both the stations are equipped with digital ionosonde of the type known as Canadian Advanced Digital Ionosonde (CADI). In order to study the effects of geomagnetic storms on equatorial spread-F, we present and discuss three case studies, two from the ionospheric sounding observations at Sao Jose dos Campos (September and November 2000) and one from the simultaneous ionospheric sounding observations at Sao Jose dos Campos and Palmas (July 2003). Salient features from these ionospheric observations are presented and discussed in this paper. It has been observed that sometimes (e.g. 4-5 November 2000) the geomagnetic storm acts as an inhibitor (high strong spread-F season), whereas at other times (e.g. 11-12 July 2003) they act as an initiator (low strong spread-F season), possibly due to corresponding changes in the quiet and disturbed drift patterns during different seasons.

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2

Chandra, H., G. D. Vyas, H. S. S. Sinha, S. Prakash, and R. N. Misra. "Equatorial spread-F campaign over SHAR." Journal of Atmospheric and Solar-Terrestrial Physics 59, no. 2 (1997): 191–205. http://dx.doi.org/10.1016/1364-6826(95)00199-9.

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3

Raghavarao, R., R. Suhasini, H. G. Mayr, W. R. Hoegy, and L. E. Wharton. "Equatorial spread-F (ESF) and vertical winds." Journal of Atmospheric and Solar-Terrestrial Physics 61, no. 8 (1999): 607–17. http://dx.doi.org/10.1016/s1364-6826(99)00017-6.

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4

Laxmi, V. N., and V. K. Tripathi. "Radio wave heating and equatorial spread-F." Journal of Atmospheric and Terrestrial Physics 49, no. 11-12 (1987): 1071–74. http://dx.doi.org/10.1016/0021-9169(87)90089-4.

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5

Rodrigues, F. S., M. J. Nicolls, M. A. Milla, et al. "AMISR-14: Observations of equatorial spread F." Geophysical Research Letters 42, no. 13 (2015): 5100–5108. http://dx.doi.org/10.1002/2015gl064574.

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6

Anderson, David N., and Robert J. Redmon. "Forecasting scintillation activity and equatorial spread F." Space Weather 15, no. 3 (2017): 495–502. http://dx.doi.org/10.1002/2016sw001554.

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7

Roh, Kyoung-Min, Hermann Luehr, Sang-Young Park, and Jung-Ho Cho. "The Effect of Equatorial Spread F on Relative Orbit Determination of GRACE Using Differenced GPS Observations." Journal of Astronomy and Space Sciences 26, no. 4 (2009): 499–510. http://dx.doi.org/10.5140/jass.2009.26.4.499.

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8

HUANG CHAO-SONG and M.C.KELLEY. "NUMERICAL SIMULATIONS OF LARGE SCALE EQUATORIAL SPREAD F." Acta Physica Sinica 45, no. 11 (1996): 1930. http://dx.doi.org/10.7498/aps.45.1930.

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9

Kelley, Michael C., Jonathan J. Makela, Brent M. Ledvina, and Paul M. Kintner. "Observations of equatorial spread-F from Haleakala, Hawaii." Geophysical Research Letters 29, no. 20 (2002): 64–1. http://dx.doi.org/10.1029/2002gl015509.

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10

Kelley, M. C. "Equatorial spread-F: recent results and outstanding problems." Journal of Atmospheric and Terrestrial Physics 47, no. 8-10 (1985): 745–52. http://dx.doi.org/10.1016/0021-9169(85)90051-0.

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11

Raghavarao, R., M. Nageswararao, J. Hanumath Sastri, G. D. Vyas, and M. Sriramarao. "Role of equatorial ionization anomaly in the initiation of equatorial spread F." Journal of Geophysical Research 93, A6 (1988): 5959. http://dx.doi.org/10.1029/ja093ia06p05959.

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12

Sahai, Y., P. R. Fagundes, J. R. Abalde, et al. "Generation of large-scale equatorial F-region plasma depletions during lowrange spread-F season." Annales Geophysicae 22, no. 1 (2004): 15–23. http://dx.doi.org/10.5194/angeo-22-15-2004.

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Abstract. All-sky imaging observations of the F-region OI 630nm nightglow emission allow us to visualize large-scale equatorial plasma depletions, generally known as trans-equatorial plasma bubbles. Strong range type spread-F is the radio signature of these (magnetically) north-south aligned plasma depletions. An extensive database of the OI 630nm emission all-sky imaging observations has been obtained at Cachoeira Paulista (22.7°S, 45.0°W; dip latitude ∼16°S), Brazil, between the years 1987 and 2000. An analysis of these observations revealed that relatively few large-scale ionospheric plasma depletions occur during the months of May to August (southern winter, June solstice) in the Brazilian sector. Of the few that are observed during these months, some occur in association with geomagnetic storms and some do not. In this paper, a detailed analysis of the events when large-scale ionospheric plasma depletions were initiated and evolved during the June solstice periods are presented and discussed.Key words. Atmospheric composition and chemistry (airglow and aurora). Ionosphere (equatorial ionosphere; ionospheric irregularities)

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13

Cécile, J. F., P. Vila, and E. Blanc. "HF radar observations of equatorial spread-F over West Africa." Annales Geophysicae 14, no. 4 (1996): 411–18. http://dx.doi.org/10.1007/s00585-996-0411-1.

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Abstract. New experimental data depicting equatorial spread-F were taken during an HF radar sounding campaign in Korhogo (Ivory Coast, 9°24N, 5°37W, dip 4°S). Range-time-intensity maps of the radar echoes have been analyzed to identify the signatures of density depletions and bottomside spread-F. Density depletions are well known features of equatorial spread-F, and are believed to emerge after the development of a Rayleigh-Taylor instability on the bottomside F-layer. A simple model is developed and used to simulate the flow of density depletions over the radar field of view. The simulation permits an interpretation of the data that yields the zonal flow velocity as a function of local time. Comparisons with previous measurements are undertaken to assess the consistency of the computational results, and qualitative arguments are presented to identify bottomside spread-F. Using the computational results as reference, a morphological study of ionograms showing spread-F is undertaken which reveals the specific signature of bottomside spread-F on ionograms recorded just after sunset.

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14

Woodman, R. F. "Spread F – an old equatorial aeronomy problem finally resolved?" Annales Geophysicae 27, no. 5 (2009): 1915–34. http://dx.doi.org/10.5194/angeo-27-1915-2009.

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Abstract. One of the oldest scientific topics in Equatorial Aeronomy is related to Spread-F. It includes all our efforts to understand the physical mechanisms responsible for the existence of ionospheric F-region irregularities, the spread of the traces in a night-time equatorial ionogram – hence its name – and all other manifestations of the same. It was observed for the first time as an abnormal ionogram in Huancayo, about 70 years ago. But only recently are we coming to understand the physical mechanisms responsible for its occurrence and its capricious day to day variability. Several additional techniques have been used to reveal the spatial and temporal characteristics of the F-region irregularities responsible for the phenomenon. Among them we have, in chronological order, radio star scintillations, trans-equatorial radio propagation, satellite scintillations, radar backscatter, satellite and rocket in situ measurements, airglow, total electron content techniques using the propagation of satellite radio signals and, recently, radar imaging techniques. Theoretical efforts are as old as the observations. Nevertheless, 32 years after their discovery, Jicamarca radar observations showed that none of the theories that had been put forward could explain them completely. The observations showed that irregularities were detected at altitudes that were stable according to the mechanisms proposed. A breakthrough came a few years later, again from Jicamarca, by showing that some of the "stable" regions had become unstable by the non-linear propagation of the irregularities from the unstable to the stable region of the ionosphere in the form of bubbles of low density plasma. A problem remained, however; the primary instability mechanism proposed, an extended (generalized) Rayleigh-Taylor instability, was too slow to explain the rapid development seen by the observations. Gravity waves in the neutral background have been proposed as a seeding mechanism to form irregularities from which the instability would grow, but the former are difficult to observe as a controlling parameter. Their actual role still needs to be determined. More recently, radar observations again have shown the existence of horizontal plasma drift velocities counter streaming the neutral wind at the steep bottom of the F-region which produces a fast growing instability from which a generalized Rayleigh-Taylor instability can grow. The mechanisms proposed would explain the rapid development of the large and medium scale irregularities that have been observed, including some seen only by radars. Nevertheless, a proper quantitative theoretical mechanism that would explain how these irregularities break into the very important meter scale ones, responsible for the radar echoes, needs to be developed. This paper makes a selective historical review of the observations and proposed theories since the phenomenon was discovered to our current understanding.

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15

Patra, A. K., P. B. Rao, V. K. Anandan, and A. R. Jain. "Radar observations of 2.8 m equatorial spread-F irregularities." Journal of Atmospheric and Solar-Terrestrial Physics 59, no. 13 (1997): 1633–41. http://dx.doi.org/10.1016/s1364-6826(96)00162-9.

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16

Hysell, D. L. "Imaging coherent backscatter radar studies of equatorial spread F." Journal of Atmospheric and Solar-Terrestrial Physics 61, no. 9 (1999): 701–16. http://dx.doi.org/10.1016/s1364-6826(99)00020-6.

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17

Tsunoda, Roland T. "On seeding equatorial spread F: Parallel or transverse transport?" Journal of Atmospheric and Solar-Terrestrial Physics 103 (October 2013): 24–29. http://dx.doi.org/10.1016/j.jastp.2012.10.016.

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18

Pillat, Valdir Gil, Paulo Roberto Fagundes, and Lamartine Nogueira Frutuoso Guimarães. "Automatically identification of Equatorial Spread-F occurrence on ionograms." Journal of Atmospheric and Solar-Terrestrial Physics 135 (December 2015): 118–25. http://dx.doi.org/10.1016/j.jastp.2015.10.015.

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19

Martinis, Carlos, Jeffrey Baumgardner, Michael Mendillo, Shin-Yi Su, and Nestor Aponte. "Brightening of 630.0 nm equatorial spread-F airglow depletions." Journal of Geophysical Research: Space Physics 114, A6 (2009): n/a. http://dx.doi.org/10.1029/2008ja013931.

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20

Aswathy, R. P., and G. Manju. "Hindcasting of Equatorial Spread F Using Seasonal Empirical Models." Journal of Geophysical Research: Space Physics 123, no. 2 (2018): 1515–24. http://dx.doi.org/10.1002/2017ja025036.

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21

Sousasantos, Jonas, José Humberto Andrade Sobral, Esfhan Alam Kherani, Marcelo Magalhães Fares Saba, and Diovane Rodolfo de Campos. "Relationship between ionospheric plasma bubble occurrence and lightning strikes over the Amazon region." Annales Geophysicae 36, no. 2 (2018): 349–60. http://dx.doi.org/10.5194/angeo-36-349-2018.

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Abstract. The vertical coupling between the troposphere and the ionosphere presents some remarkable features. Under intense tropospheric convection, gravity waves may be generated, and once they reach the ionosphere, these waves may seed instabilities and spread F and equatorial plasma bubble events may take place. Additionally, there is a close association between severe tropospheric convection and lightning strikes. In this work an investigation covering an equinox period (September–October) during the deep solar minimum (2009) presents the relation between lightning strike activity and spread F (equatorial plasma bubble) detected over a low-latitude Brazilian region. The results show a considerable correlation between these two phenomena. The common element in the center of this conformity seems to be the gravity waves. Once gravity waves and lightning strikes share the same source (intense tropospheric convection) and the effects of such gravity waves in the ionosphere include the seeding of instabilities according to the gravity waves magnitude, the monitoring of the lightning strike activity seems to offer some information about the subsequent development of spread F over the equatorial region. Keywords. Ionosphere (equatorial ionosphere)

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22

Seba, Ephrem Beshir, Melessew Nigussie, and Mark B. Moldwin. "The relationship between equatorial ionization anomaly and nighttime equatorial spread F in East Africa." Advances in Space Research 62, no. 7 (2018): 1737–52. http://dx.doi.org/10.1016/j.asr.2018.06.029.

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23

Chakrabarti, N., and G. S. Lakhina. "Collisional Rayleigh-Taylor instability and shear-flow in equatorial Spread-F plasma." Annales Geophysicae 21, no. 5 (2003): 1153–57. http://dx.doi.org/10.5194/angeo-21-1153-2003.

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Abstract. Collisional Rayleigh-Taylor (RT) instability is considered in the bottom side of the equatorial F-region. By a novel nonmodal calculation it is shown that for an applied shear flow in equilibrium, the growth of the instability is considerably reduced. Finite but small amounts of diffusion enhances the stabilization process. The results may be relevant to the observations of long-lived irregularities at the bottom-side of the F-layer.Key words. Ionosphere (ionospheric irregularities, equatorial ionosphere, plasma waves and instabilities)

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24

Reinisch, B. W., M. Abdu, I. Batista, et al. "Multistation digisonde observations of equatorial spread F in South America." Annales Geophysicae 22, no. 9 (2004): 3145–53. http://dx.doi.org/10.5194/angeo-22-3145-2004.

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Abstract. Directional ionogram and F-region drift observations were conducted at seven digisonde stations in South America during the COPEX campaign from October to December 2002. Five stations in Brazil, one in Argentina, and one in Peru, monitored the ionosphere across the continent to study the onset and development of F-region density depletions that cause equatorial spread F (ESF). New ionosonde techniques quantitatively describe the prereversal uplifting of the F layer at the magnetic equator and the eastward motion of the depletions over the stations. Three of the Brazilian stations were located along a field line with a 350-km apex over the equator to investigate the relation of the occurrence of ESF and the presence of sporadic E-layers at the two E-region intersections of the field line. No simple correlation was found.

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25

Jayachandran, P. T., P. Sri Ram, V. V. Somayajulu, and P. V. S. Rama Rao. "Effect of equatorial ionization anomaly on the occurrence of spread-F." Annales Geophysicae 15, no. 2 (1997): 255–62. http://dx.doi.org/10.1007/s00585-997-0255-3.

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Abstract. The unique geometry of the geomagnetic field lines over the equatorial ionosphere coupled with the E-W electric field causes the equatorial ionization anomaly (EIA) and equatorial spread-F (ESF). Ionosonde data obtained at a chain of four stations covering equator to anomaly crest region (0.3 to 33 °N dip) in the Indian sector are used to study the role of EIA and the associated processes on the occurrence of ESF. The study period pertains to the equinoctial months (March, April, September and October) of 1991. The ratios of critical frequency of F-layer (ƒ0F2) and electron densities at an altitude of 270 km between Ahmedabad (33 °N dip) and Waltair (20 °N dip) are found to shoot up in the afternoon hours on spread-F days showing strengthening of the EIA in the afternoon hours. The study confirms the earlier conclusions made by Raghava Rao et al. and Alex et al. that a well-developed EIA is one of the conditions conducive for the generation of ESF. This study also shows that the location of the crest is also important in addition to the strength of the anomaly.

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26

Sastri, J. H. "<i>Letter to the Editor</i>: Post-midnight onset of spread-F at Kodaikanal during the June solstice of solar minimum." Annales Geophysicae 17, no. 8 (1999): 1111–15. http://dx.doi.org/10.1007/s00585-999-1111-4.

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Abstract. At dip equatorial stations in the Indian zone, spread-F conditions are known to develop preferentially around midnight during the June solstice (northern summer) months of low solar activity, in association with a distinct increase in F layer height. It is currently held that this onset of spread-F far away from the sunset terminator is due to the generalised Rayleigh-Taylor instability mechanism, with the gravitational and cross-field instability factors (and hence F layer height) playing important roles. We have studied the quarter-hourly ionograms of Kodaikanal (10.2°N; 77.5°E; dip 4°N) for the northern summer months (May-August) of 1994 and 1995 to ascertain the ambient ionospheric conditions against which the post-midnight onset of spread-F takes place. A data sample of 38 nights with midnight onset of spread-F and 34 nights without spread-F is used for the purpose. It is found that a conspicious increase in F layer height beginning around 2100 LT occurs on nights with spread-F as well as without spread-F. This feature is seen in the nocturnal pattern of F layer height on many individual nights as well as of average F layer height for the two categories of nights. The result strongly suggests that the F layer height does not play a pivotal role in the midnight onset of spread-F during the June solstice of solar minimum. The implications of this finding are discussed.Key words. Ionosphere (equatorial ionosphere; ionospheric irregularities)

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27

Lan, Hoàng Thái, та Nguyễn Thu Trang. "Một số đặc điểm của Spread F xích đạo quan trắc tại Việt Nam". VIETNAM JOURNAL OF EARTH SCIENCES 30, № 4 (2008): 368–73. http://dx.doi.org/10.15625/0866-7187/31/4/11779.

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28

Kumar, B. T. Vikram, P. Velayudhan Nair, and P. B. Rao. "HF doppler observations on the occurrence of equatorial spread-F." Journal of Earth System Science 94, no. 3 (1985): 261–67. http://dx.doi.org/10.1007/bf02839203.

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29

RASTOGI, R. G., S. ALEX, and P. V. KOPARKAR. "Equatorial spread F and ionospheric electron content at low latitudes." Journal of geomagnetism and geoelectricity 41, no. 9 (1989): 753–67. http://dx.doi.org/10.5636/jgg.41.753.

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30

Chen, Pei-Ren. "Equatorial plasma bubbles/range spread F irregularities and the QBO." Geophysical Research Letters 20, no. 21 (1993): 2351–54. http://dx.doi.org/10.1029/92gl01935.

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31

Jahn, J. M., J. LaBelle, and R. A. Treumann. "Evaluating the stationarity of equatorial spread-F time series data." Journal of Atmospheric and Solar-Terrestrial Physics 59, no. 4 (1997): 439–43. http://dx.doi.org/10.1016/s1364-6826(96)00054-5.

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32

Hysell, D. L. "Imaging coherent scatter radar studies of bottomside equatorial spread F." Journal of Atmospheric and Solar-Terrestrial Physics 60, no. 11 (1998): 1109–22. http://dx.doi.org/10.1016/s1364-6826(98)00047-9.

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33

Chen, K. Y., H. C. Yeh, S. Y. Su, C. H. Liu, and Norden E. Huang. "Anatomy of plasma structures in an equatorial spread F event." Geophysical Research Letters 28, no. 16 (2001): 3107–10. http://dx.doi.org/10.1029/2000gl012805.

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34

Thammavongsy, P., P. Supnithi, W. Phakphisut, K. Hozumi, and T. Tsugawa. "Spread-F prediction model for the equatorial Chumphon station, Thailand." Advances in Space Research 65, no. 1 (2020): 152–62. http://dx.doi.org/10.1016/j.asr.2019.09.040.

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35

Krall, J., J. D. Huba, and D. C. Fritts. "On the seeding of equatorial spread F by gravity waves." Geophysical Research Letters 40, no. 4 (2013): 661–64. http://dx.doi.org/10.1002/grl.50144.

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36

Abdu, M. A., E. Alam Kherani, I. S. Batista, E. R. de Paula, D. C. Fritts, and J. H. A. Sobral. "Gravity wave initiation of equatorial spread F/plasma bubble irregularities based on observational data from the SpreadFEx campaign." Annales Geophysicae 27, no. 7 (2009): 2607–22. http://dx.doi.org/10.5194/angeo-27-2607-2009.

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Abstract. The data from ground based experiments conducted during the 2005 SpreadFEx campaign in Brazil are used, with the help of theoretical model calculations, to investigate the precursor conditions, and especially, the role of gravity waves, in the instability initiation leading to equatorial spread F development. Data from a digisonde and a 30 MHz coherent back-scatter radar operated at an equatorial site, Sao Luis (dip angle: 2.7°) and from a digisonde operated at another equatorial site (dip angle: −11.5°) are analyzed during selected days representative of differing precursor conditions of the evening prereversal vertical drift, F layer bottom-side density gradients and density perturbations due to gravity waves. It is found that radar irregularity plumes indicative of topside bubbles, can be generated for precursor vertical drift velocities exceeding 30 m/s even when the precursor GW induced density oscillations are marginally detectable by the digisonde. For drift velocities ≤20 m/s the presence of precursor gravity waves of detectable intensity is found to be a necessary condition for spread F instability initiation. Theoretical model calculations show that the zonal polarization electric field in an instability development, even as judged from its linear growth phase, can be significantly enhanced under the action of perturbation winds from gravity waves. Comparison of the observational results with the theoretical model calculations provides evidence for gravity wave seeding of equatorial spread F.

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37

Krall, J., J. D. Huba, G. Joyce, and S. T. Zalesak. "Three-dimensional simulation of equatorial spread-F with meridional wind effects." Annales Geophysicae 27, no. 5 (2009): 1821–30. http://dx.doi.org/10.5194/angeo-27-1821-2009.

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Abstract. The NRL SAMI3 three-dimensional simulation code is used to examine the effect of meridional winds on the growth and suppression of equatorial spread F (ESF). The simulation geometry conforms to a dipole field geometry with field-line apex heights from 200 to 1600 km at the equator, but extends over only 4 degrees in longitude. The full SAMI3 ionosphere equations are included, providing ion dynamics both along and across the field. The potential is solved in two dimensions in the equatorial plane under a field-line equipotential approximation. By selectively including terms in the potential equation, the reduced growth predicted by Maruyama (1988) and the stabilization predicted by Zalesak and Huba (1991) are separately realized. We find that ESF is stabilized by a sufficiently large constant meridional wind (60 m/s in our example).

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38

Fritts, D. C., S. L. Vadas, D. M. Riggin, et al. "Gravity wave and tidal influences on equatorial spread F based on observations during the Spread F Experiment (SpreadFEx)." Annales Geophysicae 26, no. 11 (2008): 3235–52. http://dx.doi.org/10.5194/angeo-26-3235-2008.

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Abstract. The Spread F Experiment, or SpreadFEx, was performed from September to November 2005 to define the potential role of neutral atmosphere dynamics, primarily gravity waves propagating upward from the lower atmosphere, in seeding equatorial spread F (ESF) and plasma bubbles extending to higher altitudes. A description of the SpreadFEx campaign motivations, goals, instrumentation, and structure, and an overview of the results presented in this special issue, are provided by Fritts et al. (2008a). The various analyses of neutral atmosphere and ionosphere dynamics and structure described in this special issue provide enticing evidence of gravity waves arising from deep convection in plasma bubble seeding at the bottomside F layer. Our purpose here is to employ these results to estimate gravity wave characteristics at the bottomside F layer, and to assess their possible contributions to optimal seeding conditions for ESF and plasma instability growth rates. We also assess expected tidal influences on the environment in which plasma bubble seeding occurs, given their apparent large wind and temperature amplitudes at these altitudes. We conclude 1) that gravity waves can achieve large amplitudes at the bottomside F layer, 2) that tidal winds likely control the orientations of the gravity waves that attain the highest altitudes and have the greatest effects, 3) that the favored gravity wave orientations enhance most or all of the parameters influencing plasma instability growth rates, and 4) that gravity wave and tidal structures acting together have an even greater potential impact on plasma instability growth rates and plasma bubble seeding.

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39

Uemoto, J., T. Maruyama, S. Saito, M. Ishii, and R. Yoshimura. "Relationships between pre-sunset electrojet strength, pre-reversal enhancement and equatorial spread-F onset." Annales Geophysicae 28, no. 2 (2010): 449–54. http://dx.doi.org/10.5194/angeo-28-449-2010.

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Abstract. The virtual height of the bottom side F-region (h'F) and equatorial spread-F (ESF) onsets at Chumphon (10.7° N, 99.4° E; 3.3° N magnetic latitude) were compared with the behaviour of equatorial electrojet (EEJ) ground strength at Phuket (8.1° N, 98.3° E; 0.1° N magnetic latitude) during the period from November 2007 to October 2008. Increase in the F-layer height and ESF onsets during the evening hours were well connected with the EEJ ground strength before sunset, namely, both the height increase and ESF onsets were suppressed when the integrated EEJ ground strength for the period from 1 to 2 h prior to sunset was negative. The finding suggests observationally that the pre-sunset E-region dynamo current and/or electric field are related to the F-region dynamics and ESF onsets around sunset.

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40

Hysell, D. L., E. Kudeki, and J. L. Chau. "Possible ionospheric preconditioning by shear flow leading to equatorial spread <i>F</i>." Annales Geophysicae 23, no. 7 (2005): 2647–55. http://dx.doi.org/10.5194/angeo-23-2647-2005.

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Abstract. Vertical shear in the zonal plasma drift speed is apparent in incoherent and coherent scatter radar observations of the bottomside F region ionosphere made at Jicamarca from about 1600–2200 LT. The relative importance of the factors controlling the shear, which include competition between the E and F region dynamos as well as vertical currents driven in the E and F regions at the dip equator, is presently unknown. Bottom-type scattering layers arise in strata where the neutral and plasma drifts differ widely, and periodic structuring of irregularities within the layers is telltale of intermediate-scale waves in the bottomside. These precursor waves appear to be able to seed ionospheric interchange instabilities and initiate full-blown equatorial spread F. The seed or precursor waves may be generated by a collisional shear instability. However, assessing the viability of shear instability requires measurements of the same parameters needed to understand shear flow quantitatively - thermospheric neutral wind and off-equatorial conductivity profiles. Keywords. Ionosphere (Equatorial ionosphere; ionospheric irregularities) – Space plasma physics (Waves and instabilities)

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41

Krall, J., J. D. Huba, S. L. Ossakow, and G. Joyce. "Equatorial spread <I>F</I> fossil plumes." Annales Geophysicae 28, no. 11 (2010): 2059–69. http://dx.doi.org/10.5194/angeo-28-2059-2010.

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Abstract. Behaviour of equatorial spread F (ESF) fossil plumes, i.e., ESF plumes that have stopped rising, is examined using the NRL SAMI3/ESF three-dimensional simulation code. We find that fossil bubbles, plasma density depletions associated with fossil plumes, can persist as high-altitude equatorial depletions even while being "blown" by zonal winds. Corresponding airglow-proxy images of fossil plumes, plots of electron density versus longitude and latitude at a constant altitude of 288 km, are shown to partially "fill in" in most cases, beginning with the highest altitude field lines within the plume. Specifically, field lines upon which the E field has fallen entirely to zero are affected and only the low altitude (≤600 km) portion if each field line fills in. This suggests that it should be possible to observe a bubble at high altitude on a field line for which the corresponding airglow image no longer shows a depletion. In all cases ESF plumes stop rising when the flux-tube-integrated ion mass density inside the upper edge of the bubble is equal to that of the nearby background, further supporting the result of Krall et al. (2010b).

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42

Martinis, C., and M. Mendillo. "Equatorial spread F-related airglow depletions at Arecibo and conjugate observations." Journal of Geophysical Research: Space Physics 112, A10 (2007): n/a. http://dx.doi.org/10.1029/2007ja012403.

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Hysell, D. L. "An overview and synthesis of plasma irregularities in equatorial spread F." Journal of Atmospheric and Solar-Terrestrial Physics 62, no. 12 (2000): 1037–56. http://dx.doi.org/10.1016/s1364-6826(00)00095-x.

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Kudeki, Erhan, Ahmed Akgiray, Marco Milla, Jorge L. Chau, and David L. Hysell. "Equatorial spread-F initiation: Post-sunset vortex, thermospheric winds, gravity waves." Journal of Atmospheric and Solar-Terrestrial Physics 69, no. 17-18 (2007): 2416–27. http://dx.doi.org/10.1016/j.jastp.2007.04.012.

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45

Rastogi, R. G., H. Chandra, P. Janardhan, B. W. Reinisch, and Susanta Kumar Bisoi. "Post sunset equatorial spread-F at Kwajalein and interplanetary magnetic field." Advances in Space Research 60, no. 8 (2017): 1708–15. http://dx.doi.org/10.1016/j.asr.2017.06.020.

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46

Rastogi, R. G. "On the occurrence of equatorial spread-F in the evening hours." Journal of Atmospheric and Terrestrial Physics 48, no. 8 (1986): 687–93. http://dx.doi.org/10.1016/0021-9169(86)90018-8.

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47

Materassi, Massimo. "Stochastic field theory for the ionospheric fluctuations in Equatorial Spread F." Chaos, Solitons & Fractals 121 (April 2019): 186–210. http://dx.doi.org/10.1016/j.chaos.2019.01.027.

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48

Scotto, Carlo, Alessandro Ippolito, and Dario Sabbagh. "A method for automatic detection of equatorial spread-F in ionograms." Advances in Space Research 63, no. 1 (2019): 337–42. http://dx.doi.org/10.1016/j.asr.2018.09.019.

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49

Batista, Inez S., M. A. Abdu, A. J. Carrasco, et al. "Equatorial spread F and sporadic E-layer connections during the Brazilian Conjugate Point Equatorial Experiment (COPEX)." Journal of Atmospheric and Solar-Terrestrial Physics 70, no. 8-9 (2008): 1133–43. http://dx.doi.org/10.1016/j.jastp.2008.01.007.

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50

Subbarao, K. S. V., and B. V. Krishna Murthy. "Seasonal variations of equatorial spread-<i>F</i>." Annales Geophysicae 12, no. 1 (1994): 33–39. http://dx.doi.org/10.1007/s00585-994-0033-4.

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Abstract. The occurrence of spread-F at Trivandrum (8.5°N, 77°E, dip 0.5°N) has been investigated on a seasonal basis in sunspot maximum and minimum years in terms of the growth rate of irregularities by the generalized collisional Rayleigh-Taylor (GRT) instability mechanism which includes the gravitational and cross-field instability terms. The occurrence statistics of spread-F at Trivandrum have been obtained using quarter hourly ionograms. The nocturnal variations of the growth rate of irregularities by the GRT mechanism have been estimated for different seasons in sunspot maximum and minimum years at Trivandrum using h'F values and vertical drift velocities obtained from ionograms. It is found that the seasonal variation of spread-F occurrence at Trivandrum can, in general, be accounted for on the basis of the GRT mechanism.

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