Three different types of electric field disturbances affecting equatorial ionosphere during a long‐duration prompt penetration event

Abstract

Coordinated digisonde and OI 630.0 nm airglow observations from Thumba (TVM), an Indian dip equatorial station, in conjunction with magnetic and geosynchronous particle flux measurements, reveal three different types of electric field disturbances in the equatorial ionosphere-thermosphere system (ITS) occurring in succession over a period of 6 h on a single night (22-23 January,2012; A p = 24). These include (1) westward electric field perturbations owing to a pseudo-breakup and a substorm event, each lasting for about 30 min; (2) eastward electric field perturbations continuing for about an hour, owing to the southward excursion of Z component of interplanetary magnetic field (B z ); and (3) DP2-type fluctuating (period ∼40 min) electric field perturbation sustaining for about 4 h. The pseudo-breakup and the fully grown substorm events are found to be longitudinally localized and different in terms of response in the westward auroral electrojet index (AL) as well as geosynchronous electron/proton injections. The polarity of the prompt penetration of interplanetary electric field that affects the equatorial ionosphere is observed to be eastward during 2100-2200 IST (Indian Standard Time) which is observationally sparse but consistent with modeling studies. Interestingly, on the same night, DP2-type electric field fluctuations with ∼40 min periodicity and occasional eastward polarity (akin to daytime) are also found to affect the equatorial ITS for about 4 h (2200-0200 IST). The case study, thus, brings out different processes that constitute a long duration prompt penetration event which, otherwise, would have been categorized as a single event.

Significant Electric Field Perturbations in Low Latitude Ionosphere due to the Passage of Two Consecutive ICMEs During 6–8 September 2017

“…It is noticed that the DP2-type electric field fluctuations of ∼60-min periodicity affected equatorial ionosphere on both day (Philippine sector) and night (Peruvian sector) sides. This is consistent with earlier observations of wide range of periodicities 30-40 min (Kikuchi et al, 1996), 25-35 min (Hanumath Sastri et al, 2000, 40 min (Chakrabarty et al, , 2015Rout et al, 2018), ∼30 and ∼60 min (Chakrabarty et al, 2005;Rout et al, 2017) associated with DP2-type electric field perturbations. Another important observation that emerged from present investigation is additional presence of 45-min quasiperiodic DP2type perturbation on night side (Jicamarca sector).…”

Solar wind flow angle and geoeffectiveness of corotating interaction regions: First results

“…Therefore, although it is clear that the frequency response around the ring current region decides the prompt penetration frequency, the nature [e.g., Ohtani and Uozumi, 2014] of the processes that controls this response is not comprehensively understood. Nevertheless, the present study (Table 1) shows that on some occasions, DP2 (30 and 60 min periodicities) type [Nishida, 1968;Sastri et al, 2000;Chakrabarty et al, 2008Chakrabarty et al, , 2015 periodic fluctuations can reach up to dip equatorial ionosphere in daytime during the passage of CIRs. Table 1 suggests that the presence of PP electric field during CIR depends on the azimuthal solar wind flow angle (Φ) with the events which do not show causal relationship between EEJ and IMF B z , having | Φ | more than 6 ∘ .…”

“…Therefore, although it is clear that the frequency response around the ring current region decides the prompt penetration frequency, the nature [e.g., Ohtani and Uozumi , ] of the processes that controls this response is not comprehensively understood. Nevertheless, the present study (Table ) shows that on some occasions, DP2 (30 and 60 min periodicities) type [ Nishida , ; Sastri et al , ; Chakrabarty et al , , ] periodic fluctuations can reach up to dip equatorial ionosphere in daytime during the passage of CIRs.…”

“…The typical shielding time constant is ∼30 min [e.g., Senior and Blanc, 1984]. However, earlier observations reveal that shielding can remain broken for longer duration of time [Huang et al, 2005;Chakrabarty et al, 2015]. Therefore, although it is clear that the frequency response around the ring current region decides the prompt penetration frequency, the nature [e.g., Ohtani and Uozumi, 2014] of the processes that controls this response is not comprehensively understood.…”

Space Weather Research: Indian perspective

“…Based on VHF radar observations over equatorial ionosphere, penetration of convective electric fields to low latitudes was effectively investigated. In fact, the equatorial ionosphere is known to respond to variety of prompt electric field disturbances during space weather events, several of these affect almost instantaneously [ Sastri et al ., ; Chakrabarty et al ., , references therein]. The presence of these prompt electric field and their polarity has been successfully inferred through changes in the latitudinal extent of the processes like EIA [ Sharma et al ., , and references therein].…”