KMITL

Permanent URI for this communityhttps://dspace.kmitl.ac.th/handle/123456789/1

Browse

Settings

Access type: UnknownAuthor: search.filters.author.Ameen, Muhammad Ayyaz

Search Results

Now showing 1 - 2 of 2
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Hemispheric responses of ionosphere-thermosphere to intense geomagnetic storms over the East Asian-Australian sector
    (2025-11-15)
    Tahir, Afnan
    ;
    Wu, Falin
    ;
    Shah, Munawar
    ;
    Jamjareegulgarn, Punyawi
    ;
    Ameen, Muhammad Ayyaz
    The irregularities of huge geomagnetic storms impact the satellite communication by enforcing large delays in ray path. This work investigates the hemispheric asymmetries in ionosphere-thermosphere responses to three large geomagnetic storms (Dst ∼−170 nT), occurring in different seasons and storm phases beginning in different local times, over the middle and low latitudes of East Asian-Australian longitude sector. The variations have been studied by critical frequency of F2 layer (foF2) and multi-satellites observables at ±60° conjugate latitudes along ∼115° E. The enhanced equatorial ionization anomaly (EIA) is associated to the strong eastward electric fields, trigger significant part in main phases of the December 2015 and August 2018 storms during dayside. The main phase covering the night side during March 2023 storm, exhibited no significant total electron content (TEC)/foF2 variations except small-scale ionospheric irregularities. The unexpected ionospheric-thermospheric asymmetry on 26 August 2018 is mainly influenced by the northward neutral winds as opposed to the seasonal winds. Moreover, the recovery phases of the December 2015 and March 2023 commenced around morning hours activate a classic seasonal response at middle latitudes along with disturbance dynamo effect at low latitudes. On contrary, the ionospheric responses at the recovery phase during August 2018 storm is not dominated by expected seasonal flow and disturbance dynamo. At different phases of the three storms, E region electric fields, thermospheric composition and neutral winds played a major role for ionospheric disturbances.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Multi-Instrument Observation of the Ionospheric Irregularities and Disturbances during the 23–24 March 2023 Geomagnetic Storm
    (2024-05-01)
    Tahir, Afnan
    ;
    Wu, Falin
    ;
    Shah, Munawar
    ;
    Amory-Mazaudier, Christine
    ;
    Jamjareegulgarn, Punyawi
    This work investigates the ionospheric response to the March 2023 geomagnetic storm over American and Asian sectors from total electron content (TEC), rate of TEC index, ionospheric heights, Swarm plasma density, radio occultation profiles of Formosat-7/Cosmic-2 (F7/C2), Fabry-Perot interferometer driven neutral winds, and E region electric field. During the storm’s main phase, post-sunset equatorial plasma bubbles (EPBs) extend to higher latitudes in the western American longitudes, showing significant longitudinal differences in the American sector. Over the Indian longitudes, suppression of post-sunset irregularities is observed, attributed to the westward prompt penetration electric field (PPEF). At the early recovery phase, the presence of post-midnight/near-sunrise EPBs till post-sunrise hours in the American sector is associated with the disturbance of dynamo-electric fields (DDEF). Additionally, a strong consistency between F7/C2 derived amplitude scintillation (S4) ≥ 0.5 and EPB occurrences is observed. Furthermore, a strong eastward electric field induced an increase in daytime TEC beyond the equatorial ionization anomaly crest in the American region, which occurred during the storm’s main phase. Both the Asian and American sectors exhibit negative ionospheric storms and inhibition of ionospheric irregularities at the recovery phase, which is dominated by the disturbance dynamo effect due to equatorward neutral winds. A slight increase in TEC in the Asian sector during the recovery phase could be explained by the combined effect of DDEF and thermospheric composition change. Overall, storm-time ionospheric variations are controlled by the combined effects of PPEF and DDEF. This study may further contribute to understanding the ionospheric responses under the influence of storm-phase and LT-dependent electric fields.