Sudden Commencement Research Articles

Reaction of electric and meteorological states of the near-ground atmosphere during a geomagnetic storm on 5 April 2010

The effects of a geomagnetic storm on 5 April 2010 on electric parameters of the atmospheric near-ground layer in Kamchatka have been investigated. Three processes over the course of the storm were identified. Air electroconductivity began to decrease 4 h before the storm, and this lasted for 20 h. The storm's sudden commencement caused potential gradient oscillations with amplitudes up to 300 V/m. During the stages of the storm, a significant increase in the atmosphere ion content unipolarity coefficient occurred.

Modeling radiation belt electron acceleration by ULF fast mode waves, launched by solar wind dynamic pressure fluctuations

AbstractWe investigate the magnetospheric MHD and energetic electron response to a Storm Sudden Commencement (SSC) and subsequent magnetopause buffeting, focusing on an interval following an SSC event on 25 November 2001. We find that the electron flux signatures observed by LANL, Cluster, and GOES spacecraft during this event can largely be reproduced using an advective kinetic model for electron phase space density, using externally prescribed electromagnetic field inputs, (herein described as a “test‐kinetic model”) with electromagnetic field inputs provided by a 2‐D linear ideal MHD model for ULF waves. In particular, we find modulations in electron flux phase shifted by 90° from the local azimuthal ULF wave electric field (Eφ) and a net enhancement in electron flux after 1.5 h for energies between 500 keV and 1.5 MeV near geosynchronous orbit. We also demonstrate that electrons in this energy range satisfy the drift resonance condition for the ULF waves produced by the MHD model. This confirms the conclusions reached by Tan et al. (2011), that the energization process in this case is dominated by drift‐resonant interactions between electrons and MHD fast mode waves, produced by fluctuations in solar wind dynamic pressure.

Ground‐based ELF/VLF chorus observations at subauroral latitudes—VLF‐CHAIN Campaign

AbstractWe report observations of very low frequency (VLF) and extremely low frequency (ELF) chorus waves taken during the ELF/VLF Campaign observation with High‐resolution Aurora Imaging Network (VLF‐CHAIN) of 17–25 February 2012 at subauroral latitudes at Athabasca (L=4.3), Canada. ELF/VLF waves were measured continuously with a sampling rate of 100 kHz to monitor daily variations in ELF/VLF emissions and derive their detailed structures. We found quasiperiodic (QP) emissions whose repetition period changes rapidly within a period of 1 h without corresponding magnetic pulsations. QP emissions showed positive correlation between amplitude and frequency sweep rate, similarly to rising‐tone elements. We found an event of nearly simultaneous enhancements of QP emissions and Pc1/electromagnetic ion cyclotron wave intensities, suggesting that the temperature anisotropy of electrons and ions developed simultaneously at the equatorial plane of the magnetosphere. We also found QP emissions whose intensity suddenly increased in association with storm sudden commencement without changing their frequency. Falling‐tone ELF/VLF emissions were observed with their rate of frequency change varying from 0.7 to 0.05 kHz/s over 10 min. Bursty‐patch emissions in the lower and upper frequency bands are often observed during magnetically disturbed periods. Clear systematic correlation between these various ELF/VLF emissions and cosmic noise absorption was not obtained throughout the campaign period. These observations indicate several previously unknown features of ELF/VLF emissions in subauroral latitudes and demonstrate the importance of continuous measurements for monitoring temporal variations in these emissions.

Study on Ionospheric TEC Effect during the Magnetic Storm on August 5<sup>th</sup>,2011

Using GPS observations, this article studied the global TEC’s effect and its variation characters during the magnetic storm on August 5th, 2011. Results show that after sudden commencement and deep main phase of the magnetic storm, there are strong positive ionospheric TEC disturbances in the area along middle and low latitude with local time of 12:00 at noon. Besides, compared with TEC reference value, the maximum increase values are respectively 21.26 TECU and 25.29 TECU. TEC’s abnormal decline appeared in some area of high latitude at mid night on the northern semi-sphere. The analysis results reflect that the ionospheric disturbances are dependent on the local time. Moreover, observations on the BRMU GPS station show that the rate of TEC (ROT) rose and fell quickly, and its standard deviation ROTI index increased from less than 0.5 TECU/min to lager than 1.5 TECU/min, which meant that TEC temporal and spatial gradient had become larger and larger during the storm. The global ROTI map reflects the strong irregularity of the ionosphere density structure in the high-latitude area with higher time resolution in case of storm sudden commencement, and the maximum value rose up to 6 TECU/min. Then, the ionospheric irregularity appeared in wide area of the globe after noon.

Statistical analysis of geosynchronous magnetic field perturbations near midnight during sudden commencements

AbstractWhen an interplanetary (IP) shock passes over the Earth's magnetosphere, the geosynchronous magnetic field strength near noon is always enhanced except for the magnetopause crossing events. Near midnight, however, it increases or decreases. This indicates that the nightside magnetosphere is not always compressed by a sudden increase in the solar wind dynamic pressure. To understand midnight geosynchronous magnetic field responses to IP shocks, we statistically examined geosynchronous magnetic field perturbations, corresponding to 120 sudden commencements (SCs), observed when geosynchronous spacecraft were near midnight between 2200 and 0200 magnetic local times. Out of the 120 SCs, 107 SCs were identified by one geosynchronous spacecraft, and 13 SCs were identified by two geosynchronous spacecraft. Thus, 133 events were used in our statistical study. We observed 23 events in spring, 40 events in summer, 32 events in fall, and 38 events in winter, respectively. A statistical study of the midnight geosynchronous SC perturbations reveals the following characteristics. (1) In summer, all events show a positive enhancement (+ΔBT) in the magnetic field strength. (2) In winter, however, ΔBT exhibits a positive (+ΔBT) or negative (–ΔBT) enhancement. (3) In summer, the midnight geosynchronous SC perturbations in the BH component (positive northward) in VDH coordinates are mostly (∼88%, 35 out of 40 events) positive (+ΔBH), while the occurrence rate of the positive perturbation (∼43%) in the Bz component (positive northward) in GSM coordinates is lower than that of the negative perturbation (∼57%). (4) In winter, the negative perturbations in ΔBH (∼61%) and ΔBz (∼74%) are dominant. (5) Both the north‐south components (BH and Bz) in spring and fall are scattered around zero. To explain the observations, we suggest that SC‐associated cross‐tail current (JSC) has a peak intensity around geosynchronous orbit and thus is a main controlling factor of midnight geosynchronous magnetic field perturbations during SCs. Specifically, we suggest that the seasonal variation of the sign of ΔBH, ΔBz, and ΔBT is due to the seasonal variation of the spacecraft position relative to JSC.

Some ionospheric storm effects at equatorial and low latitudes

In this paper, the response of the equatorial and low latitude ionosphere to three intense geomagnetic storms occurred in 2002 and 2003 is reported. For that, critical frequency of F2-layer foF2 and the peak height hmF2 hmF2 for the stations Jicamarca (11.9°S), Ascension Is (7.92°S) and Tucuman (26.9°S) are used. The results show a “smoothing” of the Equatorial Anomaly structure during the development of the storms. Noticeable features are the increases in foF2 before the storm sudden commencement (SC) at equatorial latitudes and the southern crest of the Equatorial Anomaly. In some cases nearly simultaneous increases in foF2 are observed in response to the storm, which are attributed to the prompt electric field. Also, positive effects observed at equatorial and low latitudes during the development of the storm seem to be caused by the disturbance dynamo electric field due to the storm-time circulation. Increases in foF2 above the equator and simultaneous decreases in foF2 at the south crest near to the end of a long-duration main phase are attributed to equatorward-directed meridional winds. Decreases in foF2 observed during the recovery phase of storms are believed to be caused by composition changes. The results indicate that the prompt penetration electric field on the EA is important but their effect is of short lived. More significant ionospheric effects are the produced by the disturbance dynamo electric field. The role of storm-time winds is important because they modify the “fountain effect” and transport the composition changes toward low latitudes.

Transmission line model for the near‐instantaneous transmission of the ionospheric electric field and currents to the equator

AbstractThe simultaneous onset of the preliminary impulse (PI) of the geomagnetic sudden commencement at high latitude and dayside dip equator is explained by means of the TM0 mode waves propagating at the speed of light in the Earth‐ionosphere waveguide (EIW) [Kikuchi et al., 1978]. A couple of issues remain to be addressed in the EIW model: (1) How is the TM0 mode wave excited by the field‐aligned currents (FACs) in the polar region? (2) How are the quasi‐steady ionospheric currents achieved by the TM0 mode waves? (3) How simultaneous or delayed are the onset and peak of the equatorial PI with respect to the high‐latitude PI? To address these issues, we examine the TEM (TM0) mode wave propagation in the finite‐length transmission lines replacing the pair of FACs (magnetosphere‐ionosphere (MI) transmission line) and the Earth‐ionosphere waveguide (ionosphere‐ground (IG) transmission line). The issue (1) is addressed by showing that a fraction of the TEM mode wave is transmitted from the MI to IG transmission lines through the polar ionosphere. To address the issues (2) and (3), we examine the properties of the finite‐length IG transmission line with finite ionospheric conductivity. It is shown that the ionospheric currents start to grow instantaneously and continue to grow gradually with time constants of 1–10 s depending on the ionospheric conductivity. The MIG transmission line enables us to explain the instantaneous onset and delayed peak time of the equatorial PI and quick electric field response of the low‐latitude ionosphere and inner magnetosphere.

Assessment of GIC risk due to geomagnetic sudden commencements and identification of the current systems responsible

AbstractDuring periods of enhanced geomagnetic activity, geomagnetically induced currents (GIC) flow in power systems potentially causing damage to system components or failure of the system. The largest GIC are produced when there are large rates of change of the geomagnetic field (dB/dt). It is well established that the main phase of a geomagnetic storm, particularly the magnetic substorms occurring during that period, is a cause of large GIC and hence a risk factor for power systems. However, some power system disturbances have been associated with the occurrence of a storm sudden commencement (SSC) prior to the main phase. We investigate the magnetic signature observed on the ground and the associated solar wind and interplanetary magnetic field (IMF) conditions for both SSC and sudden impulse (SI) events, which are grouped together as sudden commencements (SC). SCs are primarily attributed to a sudden enhancement of the magnetopause current. For some events, we show that there is a high‐latitude enhancement (HLE) of the SC amplitude and corresponding dB/dt. The limited spatial extent suggests an ionospheric current source. Examination of the polarity of the change in the X‐component magnetic field shows that the HLE is due to a sudden increase of the ionospheric convection electrojets. The occurrence of the HLE is more prevalent for SSC‐type SCs, SCs caused by coronal mass ejections as opposed to corotating interaction regions, and SCs associated with a large solar wind speed (vsw) prior to the SC or a large Δvsw at the time of the SC.

Study of daytime vertical E × B drift velocities inferred from ground-based magnetometer observations of ΔH, at low latitudes under geomagnetically disturbed conditions

In this study, 30 storm sudden commencement (SSC) events during the period 2001–2007 for which daytime vertical E×B drift velocities from JULIA radar, Jicamarca (geographic latitude 11.91°S, geographic longitude 283.11°E, 0.81°N dip latitude), Peru and ΔH component of geomagnetic field measured as the difference between the magnitudes of the horizontal (H) components between two magnetometers deployed at two different locations Jicamarca (geographic latitude 11.91°S, geographic longitude 283.11°E, 0.81°N dip latitude) and Piura (geographic latitude 5.21°S, geographic longitude 279.41°E, 6.81°N dip latitude), in Peru, were considered. It is observed that a positive correlation exists between peak value of daytime vertical E×B drift velocity and peak value of ΔH for the three consecutive days of SSC. A qualitative analysis made after selecting the peak values of daytime vertical E×B drift velocity and ΔH showed that 57% of the events have daytime vertical E×B drift velocity peak in the magnitude range 20–30m/s and 63% of the events have ΔH peak in the range 80–100nT. The maximum probable (45%) range of time of occurrence of peak value for both vertical E×B drift velocity and ΔH during the daytime hours were found to be the same, i.e., 10:00–12:00 LT. A strong positive correlation was also found to exist between the daytime vertical E×B drift velocity and ΔH for all the three consecutive days of SSC, for all the events considered. To establish a quantitative relationship between day time vertical E×B drift velocity and ΔH, linear and polynomial (order 2 and 3) regression analysis (Least Square Method (LSM)) were carried out, considering the fully disturbed day after the commencement of the storm as ‘disturbed period’ for the SSC events selected for analysis. The formulae indicating the relationship between daytime vertical E×B drift velocity and ΔH, for the ‘disturbed periods’, obtained through the regression analysis were verified using the JULIA radar observed E×B drift velocity for 3 selected events. Root Mean Square (RMS) error analysis carried out for each case suggest that polynomial regression (order 3) analysis provides a better agreement with the observations from among the linear, polynomial (order 2 and 3) analysis.

Solar Cycle and Seasonal Distribution of Geomagnetic Storms with Sudden Commencement

In this brief paper the seasonal and solar cycle distribution of storms with sudden commencement is presented. A correlation between the number of geomagnetic storms by month and monthly sunspot numbers is observed. Also, a pronounced seasonal variation of the occurrence of intense geomagnetic storms and no dependence for moderate geomagnetic storms, which occur more frequently than the intense ones during the solar cycles.

Long-term variations of geomagnetic activity and their solar sources

Geomagnetic activity in each phase of the solar cycle consists of 3 parts: (1) a floor below which the geomagnetic activity cannot fall even in the absence of sunspots, related to moderate graduate commencement storms; (2) sunspot-related activity due to sudden commencement storms caused by coronal mass ejections; (3) graduate commencement storms due to high speed solar wind from solar coronal holes. We find that the changes in the floor depend on the global magnetic moment of the Sun, and on the other side, from the height of the floor we can judge about the amplitude of the sunspot cycle.

May 2005 Halo CMEs and Galactic Cosmic Ray Flux Changes at Earth’s Orbit

The pressure corrected hourly data from the global network of cosmic ray detectors, measurements of the interplanetary magnetic field (IMF) intensity (B) at Earth’s orbit and its components B x , B y , B z (in the geocentric solar ecliptic coordinates) are used to conduct a comprehensive study of the galactic cosmic ray (GCR) intensity fluctuations caused by the halo coronal mass ejection of 13 May 2005. Distinct differences exist in GCR timelines recorded by neutron monitors (NMs) and multidirectional muon telescopes (MTs), the latter respond to the high rigidity portion of the GCR differential rigidity spectrum. The Forbush decrease (FD) onset in MTs is delayed (∼5 h) with respect to the onset of a geomagnetic storm sudden commencement (SSC) and a large pre-increase is present in MT data before, during, and after the SSC onset, of unknown origin. The rigidity spectrum, for a range of GCR rigidities (≤200 GV), is a power law in rigidity (R) with a negative exponent (γ=−1.05) at GCR minimum intensity, leading us to infer that the quasi-linear theory of modulation is inconsistent with observations at high rigidities (>1 GV); the results support the force field theory of modulation. At present, we do not have a comprehensive model for the FD explaining quantitatively all the observational features but we present a preliminary model listing physical processes that may contribute to a FD timeline. We explored the connections between different phases of the FD and the power spectra of IMF components but did not find a sustained relationship.

Effect of SC on frequency content of geomagnetic data using DWT application: SC automatic detection

In this paper, a study is made to determine the effect of sudden commencement (SC) on the power spectrum of geomagnetic data using multiresolution analysis (MRA) of the discrete wavelet transform (DWT). The results of this study provides a guide to develop a new technique to automatically detect the SC because it could be an indicator of the onset of a geomagnetic storm. This new technique divides the original time series into different frequency sub-bands using the MRA of the DWT. Then it detects the change in a certain sub-band which shows a large change due to the SC. The geomagnetic records used in this study were 3-s resolution data collected from the Circum-Pan Pacific Magnetometer Network (CPMN). Using such high-resolution data enables us to minimize the detection error and the processing time to make a decision. The proposed algorithm is tested on one sample every three seconds of data sets collected from the CPMN. The maximum standard deviation of the algorithm detection times is observed to be fifty four seconds of the corresponding arrival times as determined by the National Geophysical Data Center (NGDC).

Correction to “Interplanetary shock‐induced current sheet disturbances leading to auroral activations: THEMIS observations”

[1] During the production of our original paper “Interplanetary shock-induced current sheet disturbances leading to auroral activations: THEMIS observations” by Xiaoyan Zhou, Xu-Zhi Zhou, Vassilis Angelopoulos, Quanqi Shi, Chih-Ping Wang, and Harald Frey (Journal of Geophysical Research, 118, 1–15, doi:10.1002/jgra.50175, 2013), Supporting Information that shows an animation was omitted during publication. The Supporting Information is included in this update. [2] In the original paper, the complete data set and our elaboration have provided a comprehensive description for the interplanetary shock effect on the magnetotail current sheet (CS)/plasma sheet and nightside ionosphere. The animation in this update illustrates the difference between the internal (due to the compressional waves) and external (due to the shock in the solar wind) compressions from the spatiotemporal point of view and presents a straightforward and dynamic depiction of the CS thinning as a result of those compressions. This Supporting Information is composed of seven frames in which magnetopause and THEMIS locations are drawn to scale. The magnetopause locations before and after the shock arrival (the time at the sudden commencement) are calculated using Shue’s model [Shue et al., 1998]. Each frame is in the X-Z GSM meridional plane and corresponds to a moment given in Table 2 except for the first frame. Locations of the internal and external compression fronts are marked to scale, which are calculated based on the observed compressional waves speed inside the magnetosphere and the shock speed in the solar wind. The tail current sheet thickness (i.e., 2 h) at the inner probes is calculated using formula (4). The parameter h is given in Table 2 and is drawn to scale as well. [3] In addition to Figures 3–5 in Zhou et al. [2013], this animation shows how much the external compression is behind the internal in distance and time and quantitatively depicts the current sheet thickness variation. Accordingly, the cross-tail current density at the CS center was abruptly enhanced as given in Table 2. Note that while not intense, the shock on 3 March 2009 caused a current sheet thickness reduction of 80% and current density increase of ~6 times in only ~7min.

Automatic detection of sudden commencements using neural networks

The aim of this work is to develop an automatic system to detect sudden commencements (SCs). SCs are produced by a sudden increase of solar wind dynamic pressure and are detected simultaneously everywhere on the ground (Araki, 1994). Since 1975, Ebro Observatory is responsible to elaborate the list of SC, following the morphological rules given by Mayaud (1973). Nowadays, this task is still done manually and presents some difficulties; the most worrying one is the decreasing number of observatories who collaborate with this task because most of them opted for the installation of unattended observatories. Hence, the necessity of an alternative method to continue the service becomes a urgency. The automatic method presented in this work is based on neural network analysis. To succeed with neural networks, we did a previous work of characterization and parameterization of SCs by statistical analysis. In this way, we focused on the determination of the appropriate parameters to be used as the inputs of the network which resulted to be: slope, change of magnetic activity and difference of the levels before and after the jump. We worked with X component and also with Y component. An important criteria introduced in this work is the necessary coherence of the results obtained with this new automatic method with those obtained with the manual method and reported in the old list of SC. Finally, the neural network is able to recognize the SC pattern successfully, but now this is achieved in a non-manned way. A robust quasi-real-time detection can be undertaken in the future.

Collision of a solar wind shock wave with the Earth’s bow shock. Wave flow pattern

The wave pattern of the flow developed when a solar wind shock wave propagates along the surface of the Earth's bow shock is studied. The investigation is carried out in the three-dimensional non-plane-polarized formulation within the framework of the ideal magneto- hydrodynamic model in which the medium is assumed to be inviscid and non-heat-conducting and to have the infinite conductivity. The global three-dimensional pattern of the interaction which is a function of the latitude and longitude of elements on the surface of the bow shock is constructed as a mosaic of solutions to the problem of breakdown of a discontinuity developed between the states behind the impinging and bow shocks on the moving curve of intersection of their fronts. The investigation is carried out for typical solar wind parameters and interplanetary magnetic field strength in the Earth's orbit and for several Mach numbers of the interplanetary shock wave, which makes it possible to trace the evolution of the flow developed as a function of the intensity of the shock perturbation of the solar wind. The solution obtained is necessary for interpreting measurements carried out by spacecraft located in the neighborhood of the Lagrange point and the Earth's magnetosphere. At present, spacecraft located in the solar wind in the neighborhood of the Lagrange point L1 at distances of approximately 250 Earth's radii RE from the Earth (Wind, SOHO, and ACE) and groups of spacecraft in the neighborhood of the Earth's bow shock, in the magnetosheath, and in the outer magnetosphere (THEMIS, Cluster, and Double Star) are measuring the state of the interplanetary medium and magnetic field and transferring the data to the Earth. The measurements are used to identify sharp jumpwise changes occurring in the solar wind and related to shock waves, rotational and tangential discontinuities, and their manifestations recorded on spacecraft in the neighborhood of the Earth with the aim to forecast the cosmic weather in the form of sudden storm commencements, magnetic substorms, and sudden impulses in the Earth's magnetosphere (1-4). The results of numerical MHD simulations carried out by means of various methods (2-6) are used in analyzing the events. However, the simulations have insufficient spatial resolution, and due to this fact several MHD waves merge with one another and can hardly be identified; for example, slow or Alfven waves are unified with the contact discontinuity (5). For the correct interpretation of measurements it is necessary to use the exact solutions to the problem of interaction between a solar wind discontinuity and the Earth's bow shock Sb (7-11). The quasi-steady-state method of finding them within the framework of magnetohydrodynamics of an ideally conducting medium was first proposed in (7, 8) as the solution to the problem of breakdown of a discontinuity between the states behind the interacting waves on the moving curve of intersection of their fronts. The wave flow pattern and the dependences of the physical parameters of the medium and the magnetic field were first obtained as functions of the angle of inclination of Sb to the solar wind velocity Vsw in the

Is Space Weather Different Over Africa, and If So, Why? An AGU Chapman Conference Report

Key Points Chapman Conference Meeting Report

Pc3 geomagnetic pulsations at near-equatorial latitudes at the initial phase of the magnetic storm of April 5, 2010

An analysis of sampled 1-s observational data on geomagnetic pulsations within the Pc3 range on the INTERMAGNET network of near-equatorial and low-latitude observatories spaced over longitude during the initial phase of a moderate magnetic storm (April 5–7, 2010) was carried out for the first time. The obtained results were compared with magnetic observations at the low-latitude Chambon-la-Foret (CLF) and subauroral Kerguelen (PAF) observatories, as well as with observations at six Australian observatories located at low and middle latitudes. Two time intervals were studied in detail: the sudden commencement (SC) of the storm and the onset of the great global substorm. In the first interval, maximal amplitudes of near-equatorial pulsations were observed in the near-noon sector; in the second interval, in the near-midnight sector. The dynamics of the spectral structure of Pc3 pulsations in the considered events was shown to be different in spite of the fact that in both cases an amplification of waves was observed in two close spectral bands of the Pc3 spectrum: ∼20–30 and ∼30–40 mHz. The considered Pc3 pulsations were characterized by very small azimuthal wavenumbers (0.5 and less). Possible generation mechanisms for the observed Pc3 pulsations are discussed.

Effects of SSC in geomagnetic field components H, D and Z at low-latitude stations during 1995–2001

The present study is an analysis of the effects of storm sudden commencements (SSC) on geomagnetic field components H, D and Z during 1995–2001 with the data of five low-latitude stations in India, namely Pondicherry (PND, 2.85°N, 79.92°E), Visakhapatnam (VSK, 8.34°N, 83.32°E), Alibag (ABG, 10.19°N, 72.87°E), Nagpur (NGP, 12.12°N, 79.08°E) and Ujjain (UJJ, 14.43°N, 75.78°E). The characteristics of geomagnetic H, D and Z field components are studied under various geophysical conditions. For both quiet and storm times, the maximum amplitude of H is obtained at PND and it decreases with increase in latitude for the period 1995–2001.The amplitude of D component is larger at VSK and smaller at UJJ for both quiet and storm periods during 1995–2001. It is clear that the storm time Hmin values show no variation with solar activity at 2.85°N (PND). However, all the other latitudes in the present study such as at 8.34°N, 10.19°N, 12.12°N and 14.43°N, storm time Hmin values decrease with increase of S10.7. The values of ΔHmin shows positive correlations with solar activity, for the stations PND, VSK, ABG, NGP and UJJ, considered in the present study. The value of correlation coefficient obtained between H and interplanetary magnetic field and H and interplanetary electric field increases with increase of solar activity. The values of ΔHmin (ΔHmin=Hstorm−Hquiet) increase with increase of solar activity and correlate well with Dstmax for the five low-latitudes studied here.

Simultaneous observations of ionospheric irregularities in the African low-latitude region

Ionospheric storms represent large global disturbances of the ionospheric F-region electron density in response to geomagnetic storms. This study investigates the ionospheric response during a minor geomagnetic storm that occurred on 13–15 September 2004. In particular, we use total electron content (TEC) measurements (rate of TEC change, ROT) to examine the presence of ionospheric irregularities over four low-latitude stations in the African sector, a region that has been less studied. Ionospheric irregularities are known to cause fading and phase fluctuation of L-band radio navigation signals such as those used by the Global Navigation Satellite Systems (GNSS), and are a common feature in the equatorial and low-latitude ionosphere. In the present study, the storm began with a sudden commencement at approximately 20:00UT on 13 September, while the peak of the main phase occurred on 14 September with an SYM-H index value around −59nT. On 13 September, the storm did not appear to hinder the development of irregularities as they were observed over all the stations. In contrast, irregularities were rarely observed at two of the 4 stations under study and were absent over the other two stations on 14 September. The DSMP F15 satellite post-sunset flight over the African region observed deep density depletions on 13 September that can be associated with the presence of ionospheric plasma bubble irregularities. Furthermore, an analysis of ΔH (horizontal geomagnetic component corrected for ring current effects) shows that there was a strong positive ΔH perturbation observed in the post-sunset hours on 13 September, which suggests the presence of an eastward penetration electric field, while a negative perturbation of ΔH, which is associated with the equatorial counter-electrojet, was observed on 14 September.