Ionization hole campaign—a coordinated rocket and ground-based study at the onset of equatorial spread-F: first results

Sridharan, R.; Chandra, H.; Das, Saurabh; Sekar, R.; Sinha, H. S. S.; Raju, D. Pallam; Narayanan, R.; Raizada, S.; Misra, R. N.; Raghavarao, R.; Vyas, G. D.; Rao, P. B.; Ramarao, P. V. S.; Somayajulu, V. V.; Babu, V. V.; Данилов, А. Д.

doi:10.1016/s1364-6826(97)00031-x

Cited by 20 publications

(14 citation statements)

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“…The layers formed are extremely sharp, typically with 1-2 km width, as they manifest in ionograms and the earlier one during the Dhajala event was seen as traces at fixed altitudes. The above observations suggest that these layers represent distinctly different regions of deposition, and it gets confirmed from one of the earlier vapour release experiments from an equatorial station Sriharikota, India (Sridharan et al, 1997). Multiple Barium clouds were released around sunset when the clouds were still exposed to the solar radiation, and thus got ionized.…”

Section: Discussionsupporting

confidence: 67%

Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

et al. 2001

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Abstract. Rapid radio soundings were made over Ahmedabad, a low latitude station during the period 16-20 November 1998 to study the sporadic-E layer associated with the Leonid shower activity using the KEL Aerospace digital ionosonde. Hourly ionograms for the period 11 November to 24 November were also examined during the years from 1994 to 1998. A distinct increase in sporadic-E layer occurrence is noticed on 17, 18 and 19 November from 1996 to 1998. The diurnal variations of f 0 E s and f b E s also show significantly enhanced values for the morning hours of 18 and 19 November 1998. The ionograms clearly show strong sporadic-E reflections at times of peak shower activity with multiple traces in the altitude range of 100-140 km in few ionograms. Sporadic-E layers with multiple structures in altitude are also seen in some of the ionograms (quarter hourly) at Thumba, situated near the magnetic equator. Few of ionograms recorded at Kodaikanal, another equatorial station, also show sporadic-E reflections in spite of the transmitter power being significantly lower. These new results highlighting the effect of intense meteor showers in the equatorial and low latitude E-region are presented.

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Section: Discussionsupporting

confidence: 67%

Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

et al. 2001

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“…This could be significant in the context of the occurrence/non-occurrence of ESF. It should be mentioned here that the in-situ measurements and the theoretical simulations had shown that vertical winds have a major role in the growth of ESF (Raghavarao et al, , 1999Sekar and Raghavarao, 1987;Sekar et al, 1994;Sridharan et al, 1997). Sekar and Raghavarao (1987) with the ETWA related convergence at the equator, which in turn determines the magnitude of the vertical winds at the equator.…”

Section: Resultsmentioning

confidence: 90%

Seasonal dependence of the "forecast parameter" based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)

et al. 2008

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Abstract. In an earlier study, Thampi et al. (2006) have shown that the strength and asymmetry of Equatorial Ionization Anomaly (EIA), obtained well ahead of the onset time of Equatorial Spread F (ESF) have a definite role on the subsequent ESF activity, and a new "forecast parameter" has been identified for the prediction of ESF. This paper presents the observations of EIA strength and asymmetry from the Indian longitudes during the period from August 2005-March 2007. These observations are made using the line of sight Total Electron Content (TEC) measured by a ground-based beacon receiver located at Trivandrum (8.5 • N, 77 • E, 0.5 • N dip lat) in India. It is seen that the seasonal variability of EIA strength and asymmetry are manifested in the latitudinal gradients obtained using the relative TEC measurements. As a consequence, the "forecast parameter" also displays a definite seasonal pattern. The seasonal variability of the EIA strength and asymmetry, and the "forecast parameter" are discussed in the present paper and a critical value for has been identified for each month/season. The likely "skill factor" of the new parameter is assessed using the data for a total of 122 days, and it is seen that when the estimated value of the "forecast parameter" exceeds the critical value, the ESF is seen to occur on more than 95% of cases.

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“…14, 17, 19 and 21 February 1993. There was a rocket flight on 19 February, 1993 from SHAR and hence the whole rocket range was lighted with the result that only a few images could be taken on the night of 19 February, 1993(Sridharan et al, 1997. Sinha et al (1996) have reported some of the observations obtained on the night of 21 February 1993.…”

Section: Observationsmentioning

confidence: 99%

Some new features of ionospheric plasma depletions over the Indian zone using all sky optical imaging

Sinha

Raizada

2014

Earth Planet Sp

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An all sky optical imaging system was operated from Sriharikota rocket range (SHAR) (14• N, 80• E, 5.5• N dip latitude) during January-March, 1993 to observe ionospheric plasma depletions through 630 nm and 777.4 nm night glow emissions. Strong plasma depletions were observed only on four nights viz., 14, 17, 19 and 21 February, 1993. Except the 17 February, which was a magnetically disturbed day, all the other nights pertained to magnetically quiet period. A number of plasma depletion parameters such as, degree of depletion, east-west extent, tilt with respect to the geomagnetic field, inter-depletion distance, drift velocity and plasma enhancements or brightness patterns were estimated. Some of the important results are: (a) It was found that the east-west extent of plasma depletions varied with the degree of depletion; for the 630 nm images the degree of depletion ranged between 6-9% per 100 km east-west extent and for 777.4 nm images it was 3% per 100 km east-west extent, (b) The average inter-depletion distance (IDD) was in the range of 1500 ± 100 km during the magnetically disturbed period and 740 ± 60 km during quiet periods. This is suggestive of gravity wave modulation of the bottom side of the F-region. While the large scale gravity waves (1500 ± 100 km) of auroral origin could be responsible during magnetically disturbed period, smaller scale gravity waves (740 ± 60 km) having their origin in the lower atmosphere could produce initial perturbation in the bottom side of the F-region, (c) Plasma depletions are observed to have an eastward tilt in the range of 10-15• with respect to the geomagnetic field. It has been suggested here that these tilts are associated with the variation of plasma drift with altitude, (d) plasma depletions are observed to be moving eastwards with drift velocities in the range of 40-190 ms −1 , and (e) Strong plasma enhancements or brightness patterns were observed on three nights. The degree of enhancement was by a factor of 1.4-3.8. These enhancements lasted for more than 15 minutes. Although, prima facie, these observations look similar to the transient brightness wave reported by Mendillo et al. (1997a), the high degree of enhancement and an extended duration of more than 15 minutes, observed in the present case, need to be understood.

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Ionization hole campaign—a coordinated rocket and ground-based study at the onset of equatorial spread-F: first results

Cited by 20 publications

References 38 publications

Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

Seasonal dependence of the "forecast parameter" based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)

Some new features of ionospheric plasma depletions over the Indian zone using all sky optical imaging

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Ionization hole campaign—a coordinated rocket and ground-based study at the onset of equatorial spread-F: first results

Cited by 20 publications

References 38 publications

Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

Sporadic-E associated with the Leonid meteor shower event of November 1998 over low and equatorial latitudes

Seasonal dependence of the &quot;forecast parameter&quot; based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)

Some new features of ionospheric plasma depletions over the Indian zone using all sky optical imaging

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Seasonal dependence of the "forecast parameter" based on the EIA characteristics for the prediction of Equatorial Spread F (ESF)