Observations of Pc5 micropulsation-related electric field oscillations in the equatorial ionosphere

• Published in: Annales Geophysicae
• Main Authors: C. A. Reddy, S. Ravindran, K. S. Viswanathan, B. V. Krishna Murthy, D. R. K. Rao, T. Araki
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 1994
• Subjects: Science; Q; Physics; QC1-999; Geophysics. Cosmic physics; QC801-809; Greenland; Narsarsuaq
• Online Access: https://doi.org/10.1007/s00585-994-0565-7; https://doaj.org/article/073b0583090e4adf8808504085d9c02f

A 54.95-MHz coherent backscatter radar, an ionosonde and the magnetometer located at Trivandrum in India (8.5°N, 77°E, 0.5°N dip angle) recorded large-amplitude ionospheric fluctuations and magnetic field fluctuations associated with a Pc5 micropulsation event, which occurred during an intense magnetic storm on 24 March 1991 (A p =161). Simultaneous 100-nT-level fluctuations are also observed in the H-component at Brorfelde, Denmark (55.6°N gm) and at Narsarsuaq, Greenland (70.6°N gm). Our study of the above observations shows that the E-W electric field fluctuations in the E- and F-regions and the magnetic field fluctuations at Thumba are dominated by a near-sinusoidal oscillation of 10 min during 1730-1900 IST (1200-1330 UT), the amplitude of the electric field oscillation in the equatorial electrojet (EEJ) is 0.1-0.25 mV m -1 and it increases with height, while it is about 1.0 mV m -1 in the F-region, the ground-level H-component oscillation can be accounted for by the ionospheric current oscillation generated by the observed electric field oscillation in the EEJ and the H-component oscillations at Trivandrum and Brorfelde are in phase with each other. The observations are interpreted in terms of a compressional cavity mode resonance in the inner magnetosphere and the associated ionospheric electric field penetrating from high latitudes to the magnetic equator.