We present a short review on retrieval mechanism of the D-region ionospheric plasma using sub-ionospheric VLF/LF data. First, we discuss importance of VLF/LF observation techniques and significant earth-ionosphere propagation models to diagnose electron-ion distribution in the lower ionosphere. Then we discuss about VLF/LF perturbations due to different geophysical phenomena and corresponding numerical simulations applied to retrieve the state of the D-region ionosphere. © Springer International Publishing AG, part of Springer Nature 2018.

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University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

Journal	Data powered by TypesetAstrophysics and Space Science Proceedings
Publisher	Data powered by TypesetSpringer Netherlands
ISSN	1570-6591