Equatorial Zonal Electric Field Research Articles

Solar cycle variations in equatorial ionospheric zonal electric fields near sunrise

In this study, we investigate the solar cycle dependence of the sunrise ionospheric zonal electric fields at the equator under geomagnetically quiet conditions. Simulations using the Thermosphere–Ionosphere–Electrodynamics General Circulation Model (TIEGCM) reveal that the equatorial eastward electric field at sunrise decreases with the increase in solar activity, independent of longitude, season, and lower atmospheric tides. The solar cycle dependence of the sunrise zonal electric field is mainly related to the zonal wind dynamo. Moreover, this solar cycle dependence of sunrise electric fields at the equator is dominated by the corresponding variation in the F-region dynamo because the response of conductivity and neutral winds near sunrise to increasing solar flux is stronger in the F-region than in the E-region, although the sunrise eastward enhancement of electric fields is mainly driven by the E-region zonal wind dynamo. Specifically, the westward gradient of low-latitude F-region neutral winds near the dawn terminator tends to produce westward electric fields in the equatorial region that are more pronounced at solar maximum, whereas the midlatitude E-region dynamo induces an eastward enhancement of sunrise electric fields at the equator that decreases slightly with increasing solar activity. This study also reveals that the reason the eastward enhancement of equatorial zonal electric fields near dawn and dusk terminators show opposite solar cycle dependence is because of their different generation mechanisms.

Pronounced Suppression and X-Pattern Merging of Equatorial Ionization Anomalies After the 2022 Tonga Volcano Eruption.

Following the 2022 Tonga Volcano eruption, dramatic suppression and deformation of the equatorial ionization anomaly (EIA) crests occurred in the American sector ∼14,000 km away from the epicenter. The EIA crests variations and associated ionosphere‐thermosphere disturbances were investigated using Global Navigation Satellite System total electron content data, Global‐scale Observations of the Limb and Disk ultraviolet images, Ionospheric Connection Explorer wind data, and ionosonde observations. The main results are as follows: (a) Following the eastward passage of expected eruption‐induced atmospheric disturbances, daytime EIA crests, especially the southern one, showed severe suppression of more than 10 TEC Unit and collapsed equatorward over 10° latitudes, forming a single band of enhanced density near the geomagnetic equator around 14–17 UT, (b) Evening EIA crests experienced a drastic deformation around 22 UT, forming a unique X‐pattern in a limited longitudinal area between 20 and 40°W. (c) Thermospheric horizontal winds, especially the zonal winds, showed long‐lasting quasi‐periodic fluctuations between ±200 m/s for 7–8 hr after the passage of volcano‐induced Lamb waves. The EIA suppression and X‐pattern merging was consistent with a westward equatorial zonal dynamo electric field induced by the strong zonal wind oscillation with a westward reversal.

Dependence of Penetration Electric Field Efficiency on the Interplanetary Electric Field

AbstractSouthward interplanetary magnetic field (IMF) causes the generation of penetration electric fields in the ionosphere at middle and low latitudes. Penetration efficiency, which is defined to be the ratio of the change of the equatorial ionospheric zonal electric field to the change of the dawn‐dusk (Ey) component of the interplanetary electric field, is used to represent the quantitative relationship between interplanetary and ionospheric electric fields. We have searched equatorial vertical ion drift data measured by the Jicamarca Unattended Long‐term Investigations of the Ionosphere and Atmosphere (JULIA) radar over 19 years (2001–2019) for penetration electric fields when the correlation between interplanetary and ionospheric electric fields is greater than 0.8. In total, 450 penetration electric field events are identified. It is found that the penetration efficiency peaks near noon and decreases afterward. The penetration efficiency depends on the rate of change of Ey with time, the initial Ey when the IMF starts to turn southward, and the change in Ey between the beginning of the IMF southward turning and the subsequent northward turning. The initial Ey is well‐correlated with the change in Ey. A positive initial Ey or a smaller change in Ey results in a higher penetration efficiency. The quantitative dependence of penetration efficiency on the structures of Ey is derived for the first time. The results of this study are expected to improve the accuracy of prediction of penetration electric fields.

Longitudinal Variations of Equatorial Ionospheric Electric Fields Near Sunrise

AbstractIn this work, we carry out a comprehensive modeling study, using the Thermosphere–Ionosphere–Electrodynamics General Circulation Model, to explore the physical processes by which the longitude‐dependent geomagnetic field drives the longitudinal variations of the sunrise enhancement of the zonal electric fields at the dip equator near the June solstice. Numerical experiments and diagnostic analyses of the electrodynamics equation show that the longitudinal differences of the equatorial zonal electric fields near sunrise are primarily associated with the longitudinal variations in the zonal wind dynamo, with those from the meridional wind dynamo contributing secondarily. Furthermore, the longitudinal differences of the wind dynamo near sunrise are mainly related to the longitudinal variations of and conductance, which are caused primarily by the direct influence of the longitudinal structures of magnetic field declination and strength. Meanwhile, the longitudinal variations of neutral winds, which also result in moderate longitudinal variations, play a secondary role in the longitudinal variations of the neutral wind dynamo, while plasma density, which has minor longitudinal differences near sunrise, contributes slightly by modifying the conductance. Overall, the sunrise enhancement in June is more significant at the longitudes where the magnetic field strength and distortion are larger or the magnetic field declination is smaller in the Northern Hemisphere.

Westward Electric Fields in the Afternoon Equatorial Ionosphere During Geomagnetically Quiet Times

AbstractThe daytime average zonal electric field is well known to be eastward in the equatorial ionosphere. Geomagnetic observations have revealed that the equatorial electrojet or zonal electric field occasionally becomes westward in the afternoon sector during quiet times. We present the first analysis of the dependence of the afternoon downward plasma drifts on the season, longitude, solar activity, and lunar phase using the ROCSAT‐1 satellite observations during 1999–2004. The results show that there are ~20% of downward plasma drifts at 13–17 LT. The occurrence rate of the downward plasma drift shows a peak around January and a secondary peak in July. The occurrence rate presents a slight decrease trend with the solar activity. Especially, the occurrence rate can attain ~40–50% around 60°E in June solstice and 145–245°E in December solstice, which is nearly comparable with the occurrence rate of the upward plasma drifts in these longitudes. The downward plasma drift occurs most frequently around the full moon in the afternoon sector. The geomagnetic declination induces the hemispheric differences in the dynamo current in the conjugate regions and controls the occurrence of the westward electric fields. A wavenumber‐4 longitudinal structure also appears to be present in the occurrence rate in June–September, and the wavenumber‐4 peak coincides with the diurnal eastward tidal wind, which drives the generation of the westward electric fields.

Whole Atmosphere Model Simulations of Ultrafast Kelvin Wave Effects in the Ionosphere and Thermosphere

AbstractThis paper examines the response of the upper atmosphere to equatorial Kelvin waves with a period of ∼3 days, also known as ultrafast Kelvin waves (UFKWs). The whole atmosphere model Ground‐to‐topside model of Atmosphere and Ionosphere for Aeronomy (GAIA) is used to simulate the UFKW events in the late summer of 2010 and 2011 as well as in the boreal winter of 2012/2013. When the lower layers of the model below 30‐km altitude are constrained with meteorological data, GAIA is able to reproduce salient features of the UFKW in the mesosphere and lower thermosphere as observed by the Aura Microwave Limb Sounder. The model also reproduces ionospheric response, as validated through comparisons with total electron content data from the Gravity field and steady‐state Ocean Circulation Explorer satellite as well as with earlier observations. Model results suggest that the UFKW produces eastward‐propagating ∼3‐day variations with zonal wavenumber 1 in the equatorial zonal electric field and F region plasma density. Model results also suggest that for a ground observer, identifying ionospheric signatures of the UFKW is a challenge because of ∼3‐day variations due to other sources. This issue can be overcome by combining ground‐based measurements from different longitudes. As a demonstration, we analyze ground‐based magnetometer data from equatorial stations during the 2011 event. It is shown that wavelet spectra of the magnetic data at different longitudes are only in partial agreement, with or without a ∼3‐day peak, but a spectrum analysis based on multipoint observations reveals the presence of the UFKW.

A Case Study of the Enhancements in Ionospheric Electron Density and Its Longitudinal Gradient at Chinese Low Latitudes

AbstractThe day‐to‐day variability of the ionospheric electron density and its longitudinal gradient challenges our description and understanding of the ionosphere, which is also essential for reliable applications of the Global Navigation Satellite System (GNSS). In this paper we conduct a case study of the anomalous enhancements in ionospheric electron density and its longitudinal gradient to reveal the spatial extent and related drivers of the enhancements. The ionospheric data analyzed include the vertical total electron content (TEC) by the Global Navigation Satellite System receivers, peak electron density (NmF2) and height (hmF2) of the F layer by a chain of ionosondes, and electron density profiles recorded by the Qujing incoherent scatter radar (103.8°E, 25.6°N) during the period from 29 May to 2 June 2015. Electron density enhancements are found in the region around the northern crest of equatorial ionization anomaly on the first 2 days of June 2015. It is the first time to report that, during the anomalous enhancement, the increase in electron density over Qujing depends on altitude, being stronger at higher altitudes. Further, there are strong longitudinal gradients in vertical TEC in the regions during the course of the electron density enhancements. Low latitude hmF2 and especially the equatorial electrojet become much larger on the enhancement days, implying the important role of equatorial zonal electric fields in the formation of the electron density enhancements at low latitudes.

Morphological Differences of the Northern Equatorial Ionization Anomaly Between the Eastern Asian and American Sectors

AbstractThe morphological difference of the northern equatorial ionization anomaly between the eastern Asian and American sectors is statistically studied with ground‐based total electron content data from 2000 to 2011. The intensity (Ic), latitudinal location (Lc), and occurrence time (Tc) of the daytime equatorial ionization anomaly crest are derived from daytime peak total electron content in time‐latitude plots. The main results are as follows. Lc in the two sectors exhibits an apparent difference, especially in solar minimum, during which Lc in the American sector shows an annual variation that is more poleward in northern summer and more equatorward in northern winter, while Lc in the eastern Asian sector shows a semiannual variation that is more poleward around equinoxes and more equatorward around solstices. Ic tends to be stronger in the eastern Asian sector than that in the American sector in all seasons, and this difference increases with the increase of the solar flux index. Tc tends to be earlier in northern winter and later in northern summer in both sectors and shows dependence on solar activity. We demonstrate that the seasonal variation of Lc in the American sector is not dominated by the ionospheric equatorial zonal electric field, and suggest that the difference of Lc between the two sectors is probably related to different meridional wind effects due to the displacement of geographic and magnetic equators. The Ic difference is probably related to the longitudinal wave number‐3 and ‐4 structures driven by tidal forcing from the 5lower atmosphere.

Variation of the Equatorial Height Anomaly During the Main Phase of 2015 St. Patrick's Day Geomagnetic Storm Using ANNIM and TIEGCM

AbstractA double‐peak structure in the peak height of ionospheric F2 layer around ±10o geomagnetic latitudes similar to the equatorial ionization anomaly was recently reported. This unique feature was referred as the equatorial height anomaly (EHA). In the present paper, a simulation study is carried out using the data‐driven artificial neural network‐based two‐dimensional ionospheric model (ANNIM‐2D) and the physics‐based thermosphere‐ionosphere‐electrodynamics general circulation model (TIEGCM) to understand the local time and latitudinal variation of EHA during the main phase of St. Patrick's Day geomagnetic storm. Both the ANNIM‐2D and TIEGCM consistently show pronounced EHA during the main phase of the geomagnetic storm. Further, the local time of EHA development on the storm day is much earlier (nearly 2 hr) than the quiet time over Brazilian sector (90°W). The TIEGCM simulation revealed that the storm time enhancement of the equatorial fountain associated with the enhanced equatorial zonal electric field is the main controlling factor for the pronounced EHA during the main phase. The storm time meridional neutral winds positively contribute to the development of EHA. This study revealed the direct manifestation of the storm time‐enhanced plasma fountain on the EHA.

Signatures of Sudden Storm Commencement on the equatorial thermospheric dayglow

It has been observed that the OI 630.0 nm dayglow emission over a dip equatorial station, Trivandrum (8.5° N, 77° E, dip 0.5° N), India registered an abrupt increase of ~ 2000 R during the compression phase of the magnetosphere as dictated by a sudden increase in solar wind ram pressure. Furthermore, an unusual depletion of these emissions has been observed during the eastward interplanetary electric field (IEF), concomitant with southward excursion of IMF Bz. The ionosonde and magnetometer observations confirmed the effects of prompt penetration electric field (PPEF). Associated with the eastward PPEF, formation of F3 layers were also noticed. These unique results, which emphasize the effect of Sudden Storm Commencement/IEF on these equatorial daytime airglow emissions are discussed in context of changes in the equatorial zonal electric field and F region height variations associated with polar/auroral activities due to the magnetosphere-ionosphere coupling.

Study of the Equatorial and Low-Latitude Electrodynamic and Ionospheric Disturbances During the 22-23 June 2015 Geomagnetic Storm Using Ground-Based and Spaceborne Techniques.

We use a set of ground‐based instruments (Global Positioning System receivers, ionosondes, magnetometers) along with data of multiple satellite missions (Swarm, C/NOFS, DMSP, GUVI) to analyze the equatorial and low‐latitude electrodynamic and ionospheric disturbances caused by the geomagnetic storm of 22–23 June 2015, which is the second largest storm in the current solar cycle. Our results show that at the beginning of the storm, the equatorial electrojet (EEJ) and the equatorial zonal electric fields were largely impacted by the prompt penetration electric fields (PPEF). The PPEF were first directed eastward and caused significant ionospheric uplift and positive ionospheric storm on the dayside, and downward drift on the nightside. Furthermore, about 45 min after the storm commencement, the interplanetary magnetic field (IMF) Bz component turned northward, leading to the EEJ changing sign to westward, and to overall decrease of the vertical total electron content (VTEC) and electron density on the dayside. At the end of the main phase of the storm, and with the second long‐term IMF Bz southward turn, we observed several oscillations of the EEJ, which led us to conclude that at this stage of the storm, the disturbance dynamo effect was already in effect, competing with the PPEF and reducing it. Our analysis showed no significant upward or downward plasma motion during this period of time; however, the electron density and the VTEC drastically increased on the dayside (over the Asian region). We show that this second positive storm was largely influenced by the disturbed thermospheric conditions.

Electrodynamic disturbances in the Brazilian equatorial and low‐latitude ionosphere on St. Patrick's Day storm of 17 March 2015

AbstractThe St. Patrick's Day storm of 17 March 2015 has a long‐lasting main phase with the Dst reaching a minimum of −223 nT. During the main phase, two strong prompt penetration electric field (PPEF) phases took place; first with the southward turning of IMF Bz around ~1200 UT and the second with the onset of a substorm around ~1725 UT leading to strong equatorial zonal electric field enhancements. The consequent spatiotemporal disturbances in the ionospheric total electron content and the resultant modifications in the equatorial ionization anomaly (EIA) over the Brazilian longitudinal sector are investigated in detail. The simultaneous measurements from a large network of GPS receivers, ionosonde, and magnetometers over the Brazilian longitudinal sector are used for this study. In the presence of enhanced zonal electric field, the equatorial F2 layer peak (hmF2) experienced a rapid uplift without any significant change in the base height (h′F); while the F2 layer is redistributed into F2 and F3 layers. The enhanced zonal electric filed due to PPEF led to the strong super fountain effect under which the anomaly crest departed poleward to ~40°S latitude. In the presence of westward and equatorward wind surge over Brazil with the coexisting disturbance dynamo fields, strong hemispheric asymmetry is seen in the storm time response of EIA during both the PPEF phases.

Conjugate hemisphere ionospheric response to the St. Patrick's Day storms of 2013 and 2015 in the 100°E longitude sector

AbstractThe effects of the St. Patrick's Day geomagnetic storms of 2013 and 2015 in the equatorial and low‐latitude regions of both hemispheres in the 100°E longitude sector is investigated and compared with the response in the Indian sector at 77°E. The data from a chain of ionosondes and GPS/Global Navigation Satellite Systems receivers at magnetic conjugate locations in the 100°E sector have been used. The perturbation in the equatorial zonal electric field due to the prompt penetration of the magnetospheric convective under shielded electric field and the over shielding electric field gives rise to rapid fluctuations in the F2 layer parameters. The direction of IMF Bz and disturbance electric field perturbations in the sunset/sunrise period is found to play a crucial role in deciding the extent of prereversal enhancement which in turn affect the irregularity formation (equatorial spread F) in the equatorial region. The northward (southward) IMF Bz in the sunset period inhibited (supported) the irregularity formation in 2015 (2013) in the 100°E sector. Large height increase (hmF2) during sunrise produced short‐duration irregularities during both the storms. The westward disturbance electric field on 18 March inhibited the equatorial ionization anomaly causing negative (positive) storm effect in low latitude (equatorial) region. The negative effect was amplified in low midlatitude by disturbed thermospheric composition which produced severe density/total electron content depletion. The longitudinal and hemispheric asymmetry of storm response is observed and attributed to electrodynamic and thermospheric differences.

The response of equatorial electrojet, vertical plasma drift, and thermospheric zonal wind to enhanced solar wind input

AbstractIn this study we used observations from the CHAMP and ROCSAT‐1 satellites to investigate the solar wind effects on the equatorial electrojet (EEJ), vertical plasma drift, and thermospheric zonal wind. We show that an abrupt increase in solar wind input has a significant effect on the low‐latitude ionosphere‐thermosphere system, which can last for more than 24 h. The disturbance EEJ and zonal wind are mainly westward for all local times and show most prominent responses during 07–12 and 00–06 magnetic local time (MLT), respectively. The equatorial disturbance electric field is mainly eastward at night (most prominent for 00–05 MLT) and westward at daytime with small amplitudes. In this study we show for the first time that the penetration electric field is little dependent on longitude at both the day and night sides, while the disturbance zonal wind is quite different at different longitude sectors, implying a significant longitudinal dependence of the ionospheric disturbance dynamo. Our result also indicates that the F region equatorial zonal electric field reacts faster than E region dynamo, to the enhanced solar wind input.

Duskside enhancement of equatorial zonal electric field response to convection electric fields during the St. Patrick's Day storm on 17 March 2015

AbstractThe equatorial zonal electric field responses to prompt penetration of eastward convection electric fields (PPEF) were compared at closely spaced longitudinal intervals at dusk to premidnight sectors during the intense geomagnetic storm of 17 March 2015. At dusk sector (Indian longitudes), a rapid uplift of equatorial F layer to >550 km and development of intense equatorial plasma bubbles (EPBs) were observed. These EPBs were found to extend up to 27.13°N and 25.98°S magnetic dip latitudes indicating their altitude development to ~1670 km at apex. In contrast, at few degrees east in the premidnight sector (Thailand‐Indonesian longitudes), no significant height rise and/or EPB activity has been observed. The eastward electric field perturbations due to PPEF are greatly dominated at dusk sector despite the existence of background westward ionospheric disturbance dynamo (IDD) fields, whereas they were mostly counter balanced by the IDD fields in the premidnight sector. In situ observations from SWARM‐A and SWARM‐C and Communication/Navigation Outage Forecasting System satellites detected a large plasma density depletion near Indian equatorial region due to large electrodynamic uplift of F layer to higher than satellite altitudes. Further, this large uplift is found to confine to a narrow longitudinal sector centered on sunset terminator. This study brings out the significantly enhanced equatorial zonal electric field in response to PPEF that is uniquely confined to dusk sector. The responsible mechanisms are discussed in terms of unique electrodynamic conditions prevailing at dusk sector in the presence of convection electric fields associated with the onset of a substorm under southward interplanetary magnetic field Bz.

Storm-time meridional flows: a comparison of CINDI observations and model results

Abstract. During a large geomagnetic storm, the electric field from the polar ionosphere can expand far enough to affect the mid-latitude and equatorial electric fields. These changes in the equatorial zonal electric field, called the penetration field, will cause changes in the meridional ion flows that can be observed by radars and spacecraft. In general this E × B ion flow near the equator caused by the penetration field during undershielding conditions will be upward on the dayside and downward on the nightside of the Earth. Previous analysis of the equatorial meridional flows observed by CINDI instrument on the C/NOFS spacecraft during the 26 September 2011 storm showed that all of the response flows on the dayside were excess downward flows instead of the expected upward flows. These observed storm-time responses are compared to a prediction from a physics-based coupled model of thermosphere–ionosphere–inner-magnetosphere in an effort to explain these observations. The model results suggest that the equatorial downward flow could be attributed to a combined effect of the overshielding and disturbance dynamo processes. However, some discrepancy between the model and observation indicates a need for improving our understanding of how sensitive the equatorial electric field is to various model input parameters that describe the magnetosphere–ionosphere coupling processes.

A real‐time forecast service for the ionospheric equatorial zonal electric field

The zonal electric field is the primary driver of two important features of the equatorial ionosphere: (1)The Equatorial Ionization Anomaly (EIA), and (2) plasma density irregularities, also known as spread‐F. During propagation through the ionosphere, communication and navigation radio signals are attenuated, delayed and scattered by these ionospheric features. Prediction of the zonal electric field is therefore a key to the real‐time specification of the ionosphere. We divide the zonal electric field into a climatological contribution plus the prompt‐penetration contribution predicted by a transfer‐function model applied to the interplanetary electric field measured by the Advanced Composition Explorer (ACE) satellite. The zonal electric field is predicted about one hour in advance, covering all local times and longitudes. The real‐time prediction is available as a Google application at http://www.geomag.us/models/PPEFM/RealtimeEF.html. The benefit of this application to space weather forecasting is twofold: As the driver of the equatorial plasma fountain, the predicted zonal electric field is a leading indicator by 2–3 h of the EIA and the Total Electron Content (TEC) of the equatorial ionosphere. Second, rapid uplift of the ionosphere by strong eastward electric field is known to induce spread‐F. Prediction of enhanced prompt penetration electric field in the eastward direction therefore enables the forecast of radio communication and navigation outages in the equatorial region.

On TIE‐GCM simulation of the evening equatorial plasma vortex

It has already been shown that the Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model (TIE‐GCM) is capable of reproducing the pre‐reversal enhancement (PRE) of the equatorial zonal electric field. However, the ability of TIE‐GCM to reproduce the post‐sunset plasma vortex, an important feature of the evening equatorial ionosphere closely related to the PRE, has been overlooked and had yet to be addressed. In order to address the ability of TIE‐GCM to reproduce the vortex, we examined model simulations of the plasma flow pattern in the geomagnetic equatorial plane and compared the simulations with ground‐based radar observations. We found that TIE‐GCM is indeed capable of reproducing the overall features of the post‐sunset equatorial plasma vortex pattern. We also found that both E and F region dynamos in TIE‐GCM dictate the main features of the vertical shear in the zonal plasma drifts that is part of the evening vortex. The contribution of vertical currents to the shear, however, is not negligible. Comparison of simulation results with radar measurements of the vortex indicates that the model can still be improved to better match the observations.

Features of theF3layer in the low-latitude ionosphere at sunset

The F-3 layer is a common feature within +/- 10 degrees of the magnetic equatorial ionosphere in the daytime. According to Balan et al. (1998) the F-3 layer occurs mainly during the morning-noon period due to the combined effect of the upward E x B drift and the neutral wind that provides upward plasma drifts at and above the F-2 layer. The F-3 layer occurrence rate is higher in summer and decreases with increasing solar activity. In this study, the characteristic of the sunset F-3 layer is first investigated using a solar cycle of ionosonde data (1995-2010) from the magnetic equatorial station at Jicamarca, and compared with the features derived from the four subtropical stations at Sao Luis, Fortaleza, Kwajalein, and Vanimo. Evidence shows that the local time distribution of the occurrence of the F-3 layer can extend to the postsunset time (1800-2100 local time). The sunset F-3 layer has a strong seasonal dependence occurring mainly during the summertime. Unlike the daytime F-3 layer, the occurrence of the sunset F-3 layer clearly increases and the virtual height of the bottom side of the F-3 layer statistically increases from 620 to 1000 km with increasing solar activity. In addition, the occurrence of the sunset F-3 layer at the other stations is much less than that at Jicamarca. These features of the dependence on the season, solar activity, and latitude are clearly related to the geomagnetic control of the evening prereversal enhancement of the equatorial zonal electric field and geomagnetic configuration.

Equatorial zonal electric fields inferred from a 3‐D electrostatic potential model and ground‐based magnetic field measurements

We present a new technique to infer quiet time zonal electric fields in the daytime equatorial ionosphere. The electric field inference technique utilizes a three‐dimensional (3‐D) electrostatic potential model of the low‐latitude ionosphere constrained by ground‐based magnetic field measurements. To test this technique, inferred zonal electric fields for the Peruvian sector in Jicamarca (11.95°S, 283.13°E, 0.6°N dip latitude) were compared with zonal electric field (vertical drift) measurements made by the Jicamarca Incoherent Scatter Radar. The comparison shows a good agreement between the inferred and measured electric fields. An example of electric field estimation for Davao (7.4°N, 125.4°E, 0.58°S dip latitude) in the Philippines sector is also presented in this report. Inferred electric fields for Davao are in good agreement with F region vertical plasma drifts measured by drift sensors onboard the AE‐E and ROCSAT‐1 satellites on that longitude sector. Our results suggest that realistic estimates of quiet time zonal electric fields for the equatorial ionosphere can be obtained from the 3‐D potential model whenever observatory magnetic field measurements are available.