>MR1237: /* Research */ Cleaned up section

2020-12-27T21:25:37Z

Research: Cleaned up section

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{{Infobox scientist
| honorific_prefix =
| name = Hari Keshab Sen
| native_name = হরিকেশব সেন
| image =
| caption =
| honorific_suffix =
| birth_date = {{Birth date|df=yes|1905|2|9}}
| birth_place =
| death_date = {{Death date and age|df=yes|1976|9|1|1905|2|9}}
| death_place =
| alma_mater = {{Plainlist|
* [[Allahabad University]]
* [[Harvard University]]
}}
| fields = * [[Physics]]
* [[Astronomy]]
| nationality = [[India]]n
| workplaces = {{Plainlist|
* [[Harvard College Observatory]]
* [[Air Force Research Laboratory]]
* [[Hughes Aircraft Company]]
* [[National Institute of Standards and Technology]]
}}
| doctoral_advisor =
| academic_advisors =
| known_for = Sen-Wyller magneto-ionic theory (1960)
| awards =
| signature =
}}
'''Hari Keshab Sen''' ([[9 February]], 1905<ref>{{Cite web|title=Hari Keshab Sen|url=https://www.myheritage.com/names/hari_sen|website=www.myheritage.com|access-date=2020-02-18}}</ref> - [[1 September]], 1976), popularly known as '''H. K. Sen'''<ref name=PhysicsToday>{{Cite journal|date=1977|title=Hari Keshab Sen|journal=Physics Today|language=en|volume=30|issue=6|pages=68|doi=10.1063/1.3037610|bibcode=1977PhT....30f..68.|doi-access=free}}</ref> was an [[India]]n Bengali scientist, [[astrophysicist]]. He was known for the '''''Sen-Wyller magneto-ionic theory''''', which is a generalisation of the ''standard Appleton-Hartree formula'' for radio [[wave propagation]] through a weakly ionized gas in a [[magnetic field]]. The Sen-Wyller magneto-ionic theory was discoversd in 1960 by Hari Keshab Sen and A. A. Wyller.<ref name=PhysicsToday/>

== Biography ==
After completing his early education, H. K. Sen received his doctorate in astrophysics from [[Allahabad University]] in 1943. Then receiving an ''Aggasiz Research Fellowship'' to [[Harvard University]] in 1947 he went to US. From 1948–51, Sen was a lecturer in [[astronomy]] at the [[Harvard College Observatory]]. There he worked with [[Donald Howard Menzel|Donald H. Menzel]] on astrophysical problems. Sen stayed from 1951-54 as a physicist at the [[National Institute of Standards and Technology|National Bureau of Standards in Boulder]]. Before joining the [[Air Force Cambridge Research Laboratory]] in 1955, Sen served as a senior scientist of [[Hughes Aircraft Company|Hughes Aircraft Co]]. in 1954–55. In 1959 he became a research associate at the [[Harvard College Observatory]].<ref name=PhysicsToday/>

== Research ==
In the [[Air Force Cambridge Research Laboratory]], Sen associated with A. A. Wyller, and discovered the magneto-ionic theory in 1960.<ref>{{Cite journal|last=Bremer|first=J.|last2=Singer|first2=W.|date=1988|title=Relations between classical and Sen-Wyller magneto-ionic theories in view of their application at checking of IRI electron density models|journal=Advances in Space Research|language=en|volume=8|issue=4|pages=225–228|doi=10.1016/0273-1177(88)90246-3|bibcode=1988AdSpR...8..225B|issn=0273-1177}}</ref> His theory can explains the measured refraction, absorption and reflection properties of [[radio wave]]s in and from the [[Ionosphere|ionospheric]] D layers. Sen researched nonlinear oscillations of a Maxwellian plasma with Pradip M. Bakshi of [[Brandeis University]], [[Massachusetts]]. They obtained exact non-linear wave solutions for stationary waves in a uniformly moving frame for the case of a Maxwellian [[electron]] [[Plasma (physics)|plasma]] in a uniform ion background. It is found that there are no waves below a minimum [[phase velocity|wave velocity]]; [[anharmonicity|anharmonic waves]] develop above a certain velocity, but only up to a [[Amplitude|maximum amplitude]], depending on the wave velocity.<ref>{{Cite book|last=Sen|first=Hari K.|url=https://books.google.com/?id=FtsmuwEACAAJ&printsec=frontcover#v=onepage&q&f=false|title=Nonlinear Oscillations of a Maxwellian Plasma|date=1970|publisher=Air Force Cambridge Research Laboratories, Office of Aerospace Research, United States Air Force|language=en}}</ref>

== References ==
{{Reflist}}

{{Authority control}}

[[Category:1905 births]]
[[Category:1976 deaths]]
[[Category:Scientists from West Bengal]]
[[Category:Indian astrophysicists]]

Hari Keshab Sen - Revision history

>MR1237: /* Research */ Cleaned up section