Quiet and Disturbed Time Characteristics of Blanketing Es (Esb) During Solar Cycle 23

A sporadic E layer with dense ionization blocks the upper ionospheric layers in ionosonde observations and it is called, blanketing sporadic E (Esb). Although earlier studies have demonstrated that Esb occurrence is dependent on solar activity, seasons, local time, and equatorial electrojet/counter...

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Published in:Journal of geophysical research. Space physics 2017-11, Vol.122 (11), p.11,591-11,606
Main Authors: Yadav, V., Kakad, B., Bhattacharyya, A., Pant, T. K.
Format: Article
Language:English
Subjects:
Blanketing
blanketing Es (Esb)
E region
Electrojets
Equatorial electrojet
equatorial E region
Fluctuations
Ionization
Ionospheric layers
Physics
Solar activity
Solar cycle
solar cycle 23
Solar flux
Sporadic E layer
Studies
Summer
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Summary:A sporadic E layer with dense ionization blocks the upper ionospheric layers in ionosonde observations and it is called, blanketing sporadic E (Esb). Although earlier studies have demonstrated that Esb occurrence is dependent on solar activity, seasons, local time, and equatorial electrojet/counter equatorial electrojet (EEJ/CEEJ) strength, the physics behind this dependence is not well established particularly at the dip equatorial stations. Moreover, fewer comprehensive studies are available on Esb. Present work is a detailed statistical study of Esb occurrence and its characteristics during solar cycle 23 (1996–2006) at Indian dip equatorial station Trivandrum (dip latitude 0.5°N). In present study, solar flux dependence of Esb occurrence is clearly evident not only for magnetically quiet but also for the disturbed periods with maximum during low solar activity. Known seasonal peak Esb occurrence during summer (May–August) is found to be dominated by larger percentage of total blanketing events (fbEs ≥ 8 MHz) on magnetically disturbed days as compared to quiet days. We noticed prevalent Esb occurrence in the postmidnight (00–06 India Standard Time) periods during low solar activity. Besides Esb characteristics, the present study aims to investigate effect of solar flux on association of Esb and CEEJ. Coexistence of Esb and CEEJ is emphasized in earlier observational studies. However, any dependence of their association on solar flux is not yet examined. We find that their association is weaker during low solar activity as compared to high solar activity in summer, indicating that Esb occurrence is highly likely on CEEJ days during high solar activity periods. Key Points Association of Esb and CEEJ during summer is solar flux dependent and it gets stronger with increasing solar flux Prenoon CEEJ assists the formation of Esb at an earlier time than the usual postnoon period Percentage occurrence of total blanketing Esb events (fbEs ≥ 8 MHz) is larger on magnetically disturbed days
ISSN:2169-9380
2169-9402
DOI:10.1002/2017JA023911