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Diurnal and seasonal variations of <i>hm</i>F2 deduced from digitalionosonde over New Delhi and its comparison with IRI 2001


Title (Dublin Core)

Diurnal and seasonal variations of <i>hm</i>F2 deduced from digitalionosonde over New Delhi and its comparison with IRI 2001

Description (Dublin Core)

Using digital ionosonde observations at a low mid-latitude
station, New Delhi (28.6°N, 77.2°E, dip 42.4°N), we have derived hourly
monthly values of <i>hm</i>F2 (the real height corresponding to the peak
electron density in the F2-region), employing both the Dudeney&nbsp;(1983) and
Bilitza&nbsp;(1990) empirical formulations for the period from January 2001 to
August 2002. The diurnal and seasonal variations of <i>hm</i>F2 are analyzed.
Further, to assess the predictability of the latest available model,
International Reference Ionosphere, (IRI-2001), we have obtained the
median values of <i>hm</i>F2 derived from M(3000)F2 for each hour during
different seasons and compare these with the model. Our results show that
both the Dudeney&nbsp;(1983) and Bilitza (1990) formulations reveal more or
less a similar diurnal trend of <i>hm</i>F2, with higher values around midnight
and lower during sunrise, in all the seasons. It is also noted that the <i>hm</i>F2
shows a larger variability around midnight than by daytime, in all the
seasons. Further, the study shows that median values of observed <i>hm</i>F2,
using both formulations, are somewhat larger than those predicted by
the IRI, in all seasons and at all local times. During summer, the IRI values
agree comparatively well with the observations, especially during daytime.
Major discrepancies occur when the IRI underestimates observed <i>hm</i>F2
for local times from about 14:00&nbsp;LT to 18:00&nbsp;LT and 04:00&nbsp;LT to 05:00&nbsp;LT
during winter and equinox, where the percentage deviation of the observed

<i>hm</i>F2 values with respect to the IRI model varies from 15 to 25%. The
difference between the model and observations, outside this time period,
remains less than 20% during all the seasons.<br><br>
<b>Key words.</b> Ionosphere (modelling and forecasting; equatorial

Creator (Dublin Core)

N. K. Sethi
R. S. Dabas
V. K. Vohra

Subject (Dublin Core)

Geophysics. Cosmic physics

Publisher (Dublin Core)

Copernicus Publications

Date (Dublin Core)


Type (Dublin Core)


Identifier (Dublin Core)


Source (Dublin Core)

Annales Geophysicae, Vol 22, Pp 453-458 (2004)

Language (Dublin Core)


Relation (Dublin Core)

Provenance (Dublin Core)

Journal Licence: CC BY