Merging of Storm Time Midlatitude Traveling Ionospheric Disturbances and Equatorial Plasma Bubbles

Abstract

Postsunset midlatitude traveling ionospheric disturbances (TIDs) and equatorial plasma bubbles (EPBs) were simultaneously observed over American sector during the geomagnetic storm on 8 September 2017. The characteristics of TIDs are analyzed by using a combination of the Millstone Hill incoherent scatter radar data and 2‐D detrended total electron content (TEC) from ground‐based Global Navigation Satellite System receivers. The main results associated with EPBs are as follows: (1) stream‐like structures of TEC depletion occurred simultaneously at geomagnetically conjugate points, (2) poleward extension of the TEC irregularities/depletions along the magnetic field lines, (3) severe equatorial and midlatitude electron density (Ne) bite outs observed by Defense Meteorological Satellite Program and Swarm satellites, and (4) enhancements of ionosphere F layer virtual height and vertical drifts observed by equatorial ionosondes near the EPBs initiation region. The stream‐like TEC depletions reached 46° magnetic latitudes that map to an apex altitude of 6,800 km over the magnetic equator using International Geomagnetic Reference Field. The formation of this extended density depletion structure is suggested to be due to the merging between the altitudinal/latitudinal extension of EPBs driven by strong prompt penetration electric field and midlatitude TIDs. Moreover, the poleward portion of the depletion/irregularity drifted westward and reached the equatorward boundary of the ionospheric main trough. This westward drift occurred at the same time as the sudden expansion of the convection pattern and could be attributed to the strong returning westward flow near the subauroral polarization stream region. Other possible mechanisms for the westward tilt are also discussed.

Temporal and Spatial Variations of Total Electron Content Enhancements During a Geomagnetic Storm on 27 and 28 September 2017

“…Many previous studies on the response of the magnetosphere, ionosphere, and thermosphere associated with solar wind disturbances and geomagnetic storms using ground‐based and satellite observations and simulation have been conducted (e.g., Aa et al, 2019; Astafyeva et al, 2016; Blanc & Richmond, 1980; Bruinsma & Forbes, 2007; David et al, 2011; Ferdousi et al, 2019; Huang, 2008; Kikuchi et al, 1996, 2008; Liu, Wang, Burns, Yue, et al, 2016; Liu, Wang, Burns, Solomon, et al, 2016; Nishida, 1968; Sori et al, 2019; Tanaka, 1995; Tanaka et al, 2016). According to previous knowledge, when the southward IMF arrives at the magnetopause and the merging process between the IMF and geomagnetic field occurs at the dayside magnetopause, the solar wind energy effectively enters the magnetosphere and the intensity of FACs and high‐latitude convection is enhanced significantly.…”

Coordinated Ground‐Based and Space‐Based Observations of Equatorial Plasma Bubbles

“…For these reasons, collective analysis of multisite and multi-instrument measurements provides an effective way to generate an integrated and comprehensive image for specifying both large-scale and mesoscale features of plasma bubbles (Aa et al, 2019;Cherniak et al, 2019). Recently, with the successful launch and deployment of National Aeronautics and Space Administration's Global-scale Observations of Limb and Disk (GOLD) mission, an excellent opportunity exists to use the unique data set from the GOLD far ultraviolet imaging spectrograph to monitor equatorial ionospheric structure.…”

Statistical Analysis of Equatorial Plasma Irregularities Retrieved From Swarm 2013–2019 Observations

“…The morphology and evolution processes of EPIs have been widely studied by using multi‐instrument measurements. For example, density irregularities are seen as airglow emission depletions in optical observations of ground‐based all‐sky imagers or space‐based ultraviolet imagers (Aa et al, ; Comberiate & Paxton, ; Kelley et al, ; Kil, Heelis, et al, ; Makela & Kelley, ; Martinis et al, ), plume‐like structures in radar backscatter measurements (Jin et al, ; Li et al, ; Woodman & La Hoz, ; Yokoyama & Fukao, ), range‐type equatorial spread‐F (ESF) echoes on ionograms (Abdu et al, ; Li et al, ), in situ plasma density depletions detected by Low‐Earth Orbiting (LEO) satellite observations (Aa et al, ; Basu et al, ; Cherniak et al, ; Huang et al, , ; Xiong et al, , ; Zakharenkova et al, ), and total electron content (TEC) depletions derived from Global Navigation Satellite System (GNSS) measurements (Aa et al, ; Blanch et al, ; Cherniak & Zakharenkova, ; Ma & Maruyama, ; Katamzi‐Joseph et al, ). Moreover, numerical models have also been used to study the triggering mechanisms of EPIs (e.g., Aveiro et al, ; Carter et al, ; Huba & Joyce, ; Huba et al, ; Krall et al, ; Retterer & Gentile, ; Yokoyama et al, ).…”