Analysis of the impact of geomagnetic storm onset time on GNSS signal reliability
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2025
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Abstract
This study investigates the effects of geomagnetic storm onset time on the performance of
Global Navigation Satellite System (GNSS). Unlike previous studies focusing primarily
on storm intensity, this work establishes storm onset time as a key predictive parame-
ter for ionospheric scintillation occurrence. The analysis uses geomagnetic storm data
and Global Positioning System (GPS) scintillation data from two low-latitude stations,
Makerere and Mbarara, spanning 2011 to 2016. A total of 1,082 geomagnetic storms
were identified and classified by their intensity into weak (−50 nT ≤ Dst < −25 nT),
moderate (−100 < Dst ≤ −50 nT), and severe (Dst ≤ −100 nT) categories. Only
a minority of storms triggered ionospheric scintillation, indicating that storm intensity
alone is insufficient to predict scintillation events. Scintillation was identified using the
amplitude index (S4), with thresholds set between 0.2 and 1.2. Using the epoch of
minimum IMF Bz (bow shock time) as the precise storm onset marker, results show
that scintillation predominantly occurred during night hours. Strong scintillation was
observed consistently when the bow shock time fell between 15:00 UT and 00:00 UT
(evening to nighttime in East Africa’s low-latitude region), with weaker events between
12:00 UT and 15:00 UT. No scintillation was detected when storm onset occurred from
00:00 UT to 12:00 UT, even during severe storms. These findings highlight the critical role
of storm commencement timing in ionospheric irregularity development and subsequent
GNSS signal degradation, which is crucial for mitigating risks in aviation, communication,
and navigation systems in low-latitude regions
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Tumuhairwe Bruce. (2025). Analysis of the impact of geomagnetic storm onset time on GNSS signal reliability [Dissertation]. Busitema University.