Investigation of the response time of the equatorial ionosphere in context of the equatorial electrojet and equatorial ionization anomaly

L. Jose,S. Ravindran,S. Alex,T. K. Pant,C. Vineeth

doi:10.5194/angeo-29-1267-2011

L. Jose, S. Ravindran + Show 3 more

Open Access

https://doi.org/10.5194/angeo-29-1267-2011

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Abstract

Abstract. Equatorial Electrojet (EEJ) and Equatorial Ionization Anomaly (EIA) are two large-scale processes in the equatorial/low latitude ionosphere, driven primarily by the eastward electric field during daytime. In the present paper we investigate the correlation between the Integrated EEJ strength (IEEJ) and the EIA parameters like the total electron content at the northern crest, location of crest in Magnetic latitude and strength of the EIA for the Indian sector. A good correlation has been observed between the IEEJ and EIA when a time delay is introduced between IEEJ and EIA parameters. This time delay is regarded as the response time of equatorial ionosphere in context of the evolution of EIA vis-à-vis EEJ. Further, a seasonal variation in the time delay has been observed, which is believed to be due to changes in thermospheric wind. Using the response time and the linear relationship obtained, the possibility of near-real time prediction of EIA parameters has been attempted and found that the prediction holds well during the geomagnetically quiet periods. The paper discusses these aspects in detail.

Highlights

Equatorial and low latitude ionosphere has many unique features like Equatorial Electrojet (EEJ), Equatorial Ionization Anomaly (EIA) and is more likely to have Equatorial spread F (ESF)/scintillations and other irregularities
The time delay at which the maximum correlation obtained is taken as the response time of the equatorial ionosphere, which means the time taken by the EIA to respond to the changes in the primary zonal electric field
The middle and bottom panels depict the correlation between Magnetic latitude (Mlat) of the EIA crest & Integrated EEJ strength (IEEJ) and EIA strength & IEEJ, respectively

Summary

Introduction

Equatorial and low latitude ionosphere has many unique features like Equatorial Electrojet (EEJ), Equatorial Ionization Anomaly (EIA) and is more likely to have Equatorial spread F (ESF)/scintillations and other irregularities. Using the measurements from satellite based Planar Langmuir Probe (PLP), Stolle et al (2008) have shown that the Crest to trough ratio of EIA responds to the variations of vertical drift values with a time delay of ∼1–2 h and EEJ strength ∼2–4 h.

Results

Conclusion