Role of IMF By in the prompt electric field disturbances over equatorial ionosphere during a space weather event

Chakrabarty, D. ; Hui, D. ; Rout, D. ; Sekar, R. ; Bhattacharyya, Archana ; Reeves, G. D. ; Ruohoniemi, J. M. (2017) Role of IMF By in the prompt electric field disturbances over equatorial ionosphere during a space weather event Journal of Geophysical Research: Space Physics, 122 (2). pp. 2574-2588. ISSN 0148-0227

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On 7 January 2005 (Ap=40) prompt penetration electric field perturbations of opposite polarities were observed over Thumba and Jicamarca on a few occasions during 13:45–16:30 UT. However, the electric field was found to be eastward during 14:45–15:30 UT over both Thumba and Jicamarca contrary to the general expectation wherein opposite polarities are expected at nearly antipodal points. On closer scrutiny, three important observational features are noticed during 14:10–15:15 UT. First, during 14:10–14:45 UT, despite increasing southward interplanetary magnetic field (IMF) Bz condition, the already westward electric field over Thumba weakened (less westward) while the eastward electric field over Jicamarca intensified (more eastward). Second, the electric field not only became anomalously eastward over Thumba but also got intensified further during 14:45–15:00 UT similar to Jicamarca. Third, during 15:00–15:15 UT, despite IMF Bz remaining steadily southward, the eastward electric field continued to intensify over Thumba but weakened over Jicamarca. It is suggested that the changes in IMF By component under southward IMF Bz condition are responsible for skewing the ionospheric equipotential patterns over the dip equator in such a way that Thumba came into the same DP2 cell as that of Jicamarca leading to anomalous electric field variations. Magnetic field measurements along the Indian and Jicamarca longitude sectors and changes in high-latitude ionospheric convection patterns provide credence to this proposition. Thus, the present investigation shows that the variations in IMF By are fundamentally important to understand the prompt penetration effects over low latitudes.

Item Type:Article
Source:Copyright of this article belongs to American Geophysical Union
ID Code:112413
Deposited On:10 Jan 2018 10:52
Last Modified:10 Jan 2018 10:52

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