Bibliography

Seasonal Variation of Post-sunset and Post-midnight Equatorial Plasma Bubble in Malaysia during Moderate Solar Activity Level

The equatorial plasma bubble (EPB) is a common event that occurred at the F-layer of the ionosphere due to plasma irregularities. Its occurrence can be observed around sunset and midnight hours, depending on the season. In this study, ROTI plot measurement was utilized in EPB detection, where the data was obtained from the Department of Survey and Mapping Malaysia (JUPEM). The seasonal variation of EPB in Langkawi, Malaysia was investigated for both post-sunset and post-midnight occurrence within the period of moderate solar activity year (2011). The result showed that EPB was varied with season, where both post-sunset and post-midnight EPB were highly observed during the equinoctial month (March and April) compared to June solstice. However, the post-sunset EPBs were found dominant during equinox while post-midnight EPBs were during June solstice.

Rosli, Nur; Hamid, Nurul; Abdullah, Mardina; Buhari, Suhaila; Sarudin, Idahwati;

Published by:       Published on: nov

YEAR: 2021     DOI: 10.1109/IconSpace53224.2021.9768743

solar activity; equatorial plasma bubble (EPB); GPS; Ionosphere; Plasma measurements; Plasmas; post-midnight; Southeast Asia; Time-frequency analysis

Delay in Response of Global Electron Content and Electron Concentration at Various Altitudes to 27-Day Variations in Solar Activity

We investigate the influence of 27-day variations in solar activity related to the rotation of the Sun around its axis on the thermosphere–ionosphere system at different latitudes and heights, using the results of the calculations of the model of the Earth’s upper atmosphere. Based on the results of the model calculations, related processes in the thermosphere–ionosphere system were analyzed in the period from June 20 to July 21, 2014. There is a clear reaction to the daytime electron concentration Ne in the ionosphere for 27-day variations of the solar radiation flux (index F10.7). Using comparative and correlational analyses, we revealed the delay in the variations of the daytime electron concentration values calculated in the Ne model at different heights, including at the maximum of the F2-layer of the ionosphere (NmF2) and the total electron content and global electron content regarding changes F10.7. It is shown that changes in the O/N2 ratio are the main possible reasons for the delay. The revealed two-day lag in the global electron content is consistent with the results obtained earlier from the observational data. The height structure of the delay Ne relative to F10.7 is discussed. The results of the calculations over the ionospheric stations of the Northern Hemisphere showed that the maximum delay of variations Ne relative to F10.7 is obtained in high and low latitudes, and less at the subauroral and middle latitudes. It is shown that the lag of variations in the total electron content relative to F10.7 is always less than in the case of NmF2.

Klimenko, M.; Klimenko, V.; Ratovsky, K.; Yasyukevich, A.;

Published by: Russian Journal of Physical Chemistry B      Published on: may

YEAR: 2021     DOI: 10.1134/S1990793121030052

Ionosphere; global electron content; neutral composition of the thermosphere; solar activity

Spatial distribution of TEC across India in 2005: Seasonal asymmetries and IRI prediction

Total electron content measured simultaneously at 10 locations over India during the low solar activity year 2005 is used to examine the temporal and spatial asymmetries and also to assess the predictability of the International Reference Ionosphere in respect of the observed asymmetrical distribution. The stations are distributed in latitude along 77\textdegreeE and in longitude along 23\textdegreeN forming a meridional and a zonal chain respectively. A longitudinal gradient positive towards east was observed in the daytime hours of equinox and summer. Equinoctial asymmetry was prevalent across India during this year. Within the crest and equator, winter anomaly has been observed. It is found that IRI 2012 (with Ne Quick option, URSI coefficients) is unable to fully capture the temporal variation and spatial gradients of the ionization density in the Indian sector during 2005. The amount of offset between the model and measurement varies with local time and location.

Hazarika, Rumajyoti; Bhuyan, Pradip;

Published by: Advances in Space Research      Published on: 11/2014

YEAR: 2014     DOI: 10.1016/j.asr.2014.07.011

Equatorial ionization anomaly; Ionosphere; IRI; solar activity; TEC

First observational evidence of the modulation of the threshold height h'Fc for the occurrence of equatorial spread F by neutral composition changes

[1]\ In the present study, the seasonal and solar activity variations of the threshold height for equatorial spread F occurrence irrespective of the polarity of the meridional winds during magnetically disturbed period are presented for the first time. The modulation of the seasonal pattern of the threshold height by the seasonal mean O/N₂ values is also examined. The Ionosonde data of magnetic equatorial location Trivandrum (8.5\textdegreeN, 76.5\textdegreeE) and low latitude station SHAR (13.7\textdegreeN, 80.2\textdegreeE) in the Indian longitude sector during equinoxes, winter, and summer seasons of 2002 to 2006 and the corresponding Thermosphere Ionosphere Mesosphere Energetics and Dynamics/GUVI (Global Ultra Violet Imager) O/N₂ data are used for the study. The important findings that have emerged from this study are (i) the substantial increase of threshold height with magnetic activity for all the seasons and (ii) the modulation of h\textquoterightF_c by neutral density changes, irrespective of season, solar, or magnetic activity.

Haridas, M.; Manju, G.; Pant, Tarun;

Published by: Journal of Geophysical Research: Space Physics      Published on: 06/2013

YEAR: 2013     DOI: 10.1002/jgra.50331

Equatorial Spread F; O/N2; solar activity; Threshold height