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

Xiong, Chao; Lühr, H.; Fejer, Bela G.

doi:10.1002/2015ja022133

Cited by 43 publications

(47 citation statements)

References 53 publications

(72 reference statements)

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“…Sahai et al () reported that the strong positive storm occurred during the main and recovery phase of the storm, and the density enhancement above the equatorial anomaly on the night of recovery phase was much stronger than that on the night of main phase. The different response to the storm during the recovery phase in different longitude sectors means that the storm effects on the ionosphere depend on the longitudes (Xu et al, ), especially during the recovery phase when the disturbance wind dynamo dominant the equatorial and low latitudes (Xiong et al, ). Furthermore, it can be noticed that the EIA density asymmetry and location asymmetry shown in Figures and increased with respect to the earlier several days, which means that the existence of the neutral wind and the effect of the neutral wind was remarkable.…”

Section: Discussionmentioning

confidence: 99%

The Response of Equatorial Ionization Anomaly in 120°E to the Geomagnetic Storm of 18 August 2003 at Different Altitudes From Multiple Satellite Observations

et al. 2017

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In this paper, the variations of equatorial ionization anomaly (EIA) in 120°E region during the 17–20 August 2003 storm are investigated from measurements of satellites at different altitudes from Challenging Minisatellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), scientific satellite of the Republic of China (ROCSAT‐1), and Defense Meteorological Satellite Program missions. The results showed that (1) at CHAMP and GRACE altitudes, the EIA was inhibited before the storm sudden commencement (SSC) and also during the storm recovery phase, but it was enhanced significantly during the storm main phase of the storm. (2) The variations of EIA strength and interhemispheric density asymmetry of the two crests were similar at CHAMP and GRACE altitudes, while the location asymmetry of the two crests was different at CHAMP and GRACE altitudes. (3) The irregularities and long‐duration scintillation were recorded before the SSC of the storm, when the EIA was inhibited. The irregularities at different altitudes and short‐duration scintillation were observed during the main phase of the storm, when the EIA was enhanced significantly. (4) The EIA enhancement can be attributed to the enhanced electric field due to prompt penetration interplanetary electric fields and the storm time neutral wind, while the suppression of EIA on 17 August can be attributed to the absence of the equatorward neutral wind, which varied with the altitudes. The EIA inhibition during the recovery phase may be caused mainly by the neutral wind. Our results suggest that the neutral wind is the crucial factor causing the variations in EIA and the occurrence of scintillation.

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Section: Discussionmentioning

confidence: 99%

The Response of Equatorial Ionization Anomaly in 120°E to the Geomagnetic Storm of 18 August 2003 at Different Altitudes From Multiple Satellite Observations

et al. 2017

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“…This is the time they claim that it takes for the disturbance dynamo to affect the low latitudes. In the recent study Xiong et al [] have confirmed by means of a superposed epoch analysis that about 3 h after a sudden increase of solar wind input into the magnetosphere‐ionosphere system (after the PPEF effect has ceased) westward winds and downward plasma drifts dominate for many hours in the postsunset sector. Both these forces stabilize the ionosphere.…”

Section: Discussionmentioning

confidence: 99%

“…Based on these observations, we expect a delayed and smoothed response of ionospheric plasma density to changes of the IEF. This retarded reaction has been taken into account by using a similar approach as utilized in previous studies [e.g., Richmond et al , ; Xiong et al , ]:

E_{m} ((),, t, τ) = \frac{{\int_{t 1}^{t} E^{'}}_{m} ((), t^{'}) e^{((), t^{'} - t) true/ τ} d t^{'}}{{\int_{t_{1}}^{t} e}^{((), t^{'} - t) true/ τ} d t^{'}}

where

E_{m}^{'}

is treated as a continuous function of time t ′, t 1 is chosen 3 h before the actual epoch, and τ is the e ‐folding time of the weighting function in the integrands, with a value τ = 0.5 h. These parameters have been found to be suitable for ionospheric studies like Xiong et al [, and references therein]. In Figure d

E_{m}^{'}

is presented, as calculated by equation , by a blue line, and the red line shows the time‐integrated E m obtained by equation .…”

Section: Observationsmentioning

confidence: 99%

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Ionospheric storm effects and equatorial plasma irregularities during the 17–18 March 2015 event

et al. 2016

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The intense magnetic storm on 17–18 March 2015 caused large disturbances of the ionosphere. Based on the plasma density (Ni) observations performed by the Swarm fleet of satellites, the Gravity Recovery and Climate Experiment mission, and the Communications/Navigation Outage Forecasting System satellite, we characterize the storm‐related perturbations at low latitudes. All these satellites sampled the ionosphere in morning and evening time sectors where large modifications occurred. Modifications of plasma density are closely related to changes of the solar wind merging electric field (Em). We consider two mechanisms, prompt penetration electric field (PPEF) and disturbance dynamo electric field (DDEF), as the main cause for the Ni redistribution, but effects of meridional wind are also taken into account. At the start of the storm main phase, the PPEF is enhancing plasma density on the dayside and reducing it on the nightside. Later, DDEF takes over and causes the opposite reaction. Unexpectedly, there appears during the recovery phase a strong density enhancement in the morning/prenoon sector and a severe Ni reduction in the afternoon/evening sector, and we suggest a combined effect of vertical plasma drift, and meridional wind is responsible for these ionospheric storm effects. Different from earlier studies about this storm, we also investigate the influence of storm dynamics on the initiation of equatorial plasma irregularities (EPIs). Shortly after the start of the storm main phase, EPIs appear in the postsunset sector. As a response to a short‐lived decline of Em, EPI activity appears in the early morning sector. Following the second start of the main phase, EPIs are generated for a few hours in the late evening sector. However, for the rest of the storm main phase, no more EPIs are initiated for more than 12 h. Only after the onset of recovery phase does EPI activity start again in the postmidnight sector, lasting more than 7 h. This comprehensive view of ionospheric storm effects and plasma irregularities adds to our understanding of conditions that lead to ionospheric instabilities.

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“…They also reported that the semidiurnal tide SW3 causes largest EEJ amplitudes from October to December. Recently Xiong et al [2016] examined the longitudinal wave patterns of the EEJ during quiet and disturbed periods. They found that even during magnetically disturbed periods (Kp > 3) the WN4 pattern of the EEJ can still be clearly recognized (especially during September equinox), but with lower amplitudes when compared to quiet periods.…”

Section: Introductionmentioning

confidence: 99%

New perspectives on equatorial electrojet tidal characteristics derived from the Swarm constellation

et al. 2016

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Using 2 years of magnetic field measurements from the Swarm constellation, we present a detailed study of the equatorial electrojet (EEJ) and its longitudinal gradient (ΔEEJ). This study represents for the first time the tidal characteristics derived from the longitudinal gradient of EEJ. Our analysis mainly focuses on the months around August (133 days centered on 15 August, day of year: 161–293) of 2014 and 2015 when the longitudinal wave number 4 (WN4) pattern is known to be most prominent. The EEJ intensity, derived from the average of the Swarm A and C current estimates, peaks around 11:30 LT and exhibits a clear WN4 pattern. These features are compatible with earlier CHAMP observations. The ΔEEJ, which can be considered as a high‐pass filtered result of EEJ, although having much smaller values than the EEJ, exhibits clearly the local time gradient of the EEJ diurnal variation. This kind of high‐pass filtering makes the tidal signatures in ΔEEJ more prominent. The crests of longitudinal WN4 patterns in ΔEEJ have locations different from those of EEJ. Prominent tidal components in ΔEEJ during August months are DE3, DW5, SW3, SW4, SW6, SPW1, SPW2, and SPW4. For a given wave number pattern the westward propagating components are more amplified in ΔEEJ than the eastward ones, which explains their numerous appearance. Using spectral analysis, we can confirm that the observed amplitude ratios of different tidal components between ΔEEJ and EEJ are as expected. Also, the phase differences between ΔEEJ and EEJ fit reasonably the theoretical values. The preferred amplification of westward propagating tides in ΔEEJ allows for a more detailed investigation of these components, which are assumed to be closer related to local electrodynamics processes.

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

Cited by 43 publications

References 53 publications

The Response of Equatorial Ionization Anomaly in 120°E to the Geomagnetic Storm of 18 August 2003 at Different Altitudes From Multiple Satellite Observations

The Response of Equatorial Ionization Anomaly in 120°E to the Geomagnetic Storm of 18 August 2003 at Different Altitudes From Multiple Satellite Observations

Ionospheric storm effects and equatorial plasma irregularities during the 17–18 March 2015 event

New perspectives on equatorial electrojet tidal characteristics derived from the Swarm constellation

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