Day-to-day variability of equatorial anomaly in GPS-TEC during low solar activity period

Aggarwal, Malini; Joshi, H. P.; Iyer, K. N.; Kwak, Young‐Sil; Lee, J.J.; Chandra, H.; Cho, K.S.

doi:10.1016/j.asr.2012.03.005

Cited by 31 publications

(9 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The stronger eastward electric field shifts the crest of plasma fountain further away from the dip equator. Several works reported strong correlation between integrated EEJ strength and the development of plasma fountain (Aggarwal et al, ; Raghavarao et al, ; Rama Rao et al, ; Rush & Richmond, ). This correlation was also observed in total electron content (TEC) variations reported by earlier workers (e.g., Iyer et al, ), though seasonal dependence of TEC under different solar epochs is sparse (Rama Rao et al, ; Yadav et al, ).…”

Section: Discussionmentioning

confidence: 99%

On the Occurrence of Afternoon Counter Electrojet Over Indian Longitudes During June Solstice in Solar Minimum

et al. 2018

View full text Add to dashboard Cite

Studies made earlier using ground‐based observations of geomagnetic field over the Indian longitudes revealed that the occurrence of equatorial counter electrojet (CEJ) events in afternoon hours is more frequent during June solstice (May‐June‐July‐August) in solar minimum than in other periods. In general, the June solstice solar minimum CEJ events occur between 1500 local time (LT) and 1800 LT with peak strength of about −10 nT at around 1600 LT. In order to understand the frequent occurrence of these CEJ events, an investigation is carried out using an equatorial electrojet model (Anandarao, 1976, https://doi.org/10.1029/GL003i009p00545) and the empirical vertical drift model by Fejer et al. (2008, https://doi.org/10.1029/2007JA012801). The strength, duration, peak value, and the occurrence time of CEJ obtained using electrojet model match remarkably well with the corresponding observation of average geomagnetic field variations. The occurrence of CEJ is found to be due to solar quiet (Sq) electric field in the westward direction which is manifested as downward drift in Fejer et al. (2008, https://doi.org/10.1029/2007JA012801) model output during 1500–1800 LT. Further, the occurrence of afternoon reversal of Sq electric field in this season is shown to be consistent with earlier studies from Indian sector. Therefore, this investigation provides explicit evidence for the role of westward Sq electric field on the generation of afternoon CEJ during June solstice in solar minimum periods over the Indian sector indicating the global nature of these CEJ events.

show abstract

Section: Discussionmentioning

confidence: 99%

On the Occurrence of Afternoon Counter Electrojet Over Indian Longitudes During June Solstice in Solar Minimum

et al. 2018

View full text Add to dashboard Cite

show abstract

“…For this reason, variations of the EIA have been extensively studied over various sectors [9][10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Variability of the African equatorial ionization anomaly (EIA) crests during the year 2013

2019

View full text Add to dashboard Cite

This paper discusses the variability of the position and magnitude of the crests of African Equatorial Ionization Anomaly during noon and post sunset periods. Total electron content data covered the year 2013, and were obtained from a chain of global positioning system receivers in both hemispheres around 37°E longitude. Local magnetometer data were used to infer the direction and magnitude of the E × B drift, while the solar extreme ultraviolet proxy index was used as a measure of solar activity. It was found that the time of formation of both crests varied from 1400 to 1700 local time. Additionally, the position of the crests was found to be asymmetric with respect to the magnetic equator. During the noon period, the position of the northern and southern crests varied from 4.91° to 7.36° and −9.17° to −12.62°, respectively. During the post-sunset period, it varied from 8° to 11.7° and −9° to −16°, respectively. Seasonally, with reference to the magnetic equator, both crests moved poleward during equinoxes and collapsed towards the equator during winter and summer. Equinoxes recorded the greatest crest magnitude followed by winter then summer over both hemispheres during the noon period. However, this trend persisted over the northern crest only during the post-sunset period. Overall, during the noon period, we recorded correlation coefficients of 0.67 and 0.68 between crest magnitudes and ΔH, a proxy for equatorial electrojet current, and 0.88 and 0.81 between crest positions and ΔH, for the northern and southern crests, respectively. During the Halloween day storm of 30 October 2013, a westward electric field inhibited the development of the post-sunset crests.

show abstract

“…As the dip‐equatorial electric field plays an important role in the development of plasma fountain (Aggarwal et al, ; Raghavarao et al, ; Rama Rao et al, ; Rush & Richmond, ), the westward electric field perturbations obtained on events 1–3 are expected to suppress the F‐region plasma fountain over low latitudes. In order to verify this aspect, the global TEC maps are generated corresponding to the time that is ∼2 hr after the maximum reduction in Δ E E J for the events 1–3.…”

Section: Resultsmentioning

confidence: 99%

Critical Evaluation of the Impact of Disturbance Dynamo on Equatorial Ionosphere During Daytime

2018

View full text Add to dashboard Cite

Based on careful analysis of 16 years of hourly variations of the strength of equatorial electrojet (EEJ) derived using the ground-based magnetometers over the Indian sector, the role played by disturbance dynamo electric field disturbances on equatorial ionosphere is identified. It is found that most prominent cases of the effects of disturbance dynamo occurred during equinoctial months in high solar activity period. In three extreme cases, the reduction in EEJ strength from quiet time average values of the respective month is more than twice the standard deviations for at least 3 hr. Based on the methodology described in Pandey et al. (2017, https://doi.org/10.1016/j.jastp.2017.03.012), it is found that the westward electric field perturbations are as large as 0.7 ± 0.2 to 1.2 ± 0.3 mV/m around noon hours for these three cases. In contrast to the expectation of disturbance dynamo electric field perturbations over equatorial latitudes from the earlier models, these values during daytime are significantly larger and even caused reversals of EEJ on two occasions. A possible additional source to augment the reduction in the electric field is indicated.

show abstract

Day-to-day variability of equatorial anomaly in GPS-TEC during low solar activity period

Cited by 31 publications

References 47 publications

On the Occurrence of Afternoon Counter Electrojet Over Indian Longitudes During June Solstice in Solar Minimum

On the Occurrence of Afternoon Counter Electrojet Over Indian Longitudes During June Solstice in Solar Minimum

Variability of the African equatorial ionization anomaly (EIA) crests during the year 2013

Critical Evaluation of the Impact of Disturbance Dynamo on Equatorial Ionosphere During Daytime

Contact Info

Product

Resources

About