Unique Combinations of Differently Shaped Equatorial Plasma Bubbles Occurring Within a Small Longitude Range.

On 12 October 2020 and 26 December 2021, NASA's Global‐scale Observations of the Limb and Disk (GOLD) mission observed differently shaped equatorial plasma bubbles (EPBs) simultaneously within ∼10° longitude, near the subsatellite point and over the Atlantic, respectively which is unusual. On 12 October 2020, three EPBs with differing curvatures were observed in a ∼12° longitude sector. The westside EPB was curved toward the east, in a C‐shape. The middle was straight. The eastside EPB was curved westward, in a reversed C‐shape. In the second case, 26 December 2021, in a smaller longitude range of ∼6° adjacent C‐shaped and reversed C‐shaped EPBs were observed. EPBs' zonal drift velocities at the magnetic equator and both equatorial ionization anomaly crests were compared. These occurrences of oppositely shaped EPBs simultaneously in a narrow longitude may indicate that small‐scale longitudinal variations in the E‐region density, electric field, neutral wind variations, or a combination of them were present. Plain Language Summary: The post‐sunset ionosphere becomes conducive to the formation of plasma irregularities associated with depleted plasma densities. In the images obtained from space or ground, these plasma depleted regions appear as latitudinally elongated dark bands, which are known as "equatorial plasma bubbles (EPBs)." Satellite communication and navigation systems are adversely affected when the trans‐ionospheric radio signals travel through the EPBs. Thus, investigations of EPBs' formation and development are important. In 2‐D airglow images, the EPBs appear to be straight (aligned along the magnetic field lines). However, sometimes the poleward extensions of the EPBs can be tilted eastward or westward from the magnetic field line resembling either a C‐shape or reversed C‐shape, respectively. These differently shaped EPBs have been observed before. But, NASA's Global‐scale Observations of the Limb and Disk (GOLD) mission observed them simultaneously within ∼12° and 6° longitudes on 12 October 2020 and 26 December 2021 which is unusual. Such occurrence of opposite‐shaped EPBs within a small longitude range indicates small‐scale longitudinal variations in the E‐region density, neutral winds, electric fields, or a combination of them. We present detailed observations of these two unique events with possible explanations. Key Points: Differently shaped equatorial plasma bubbles are observed simultaneously within a small longitude of ∼10°Observations indicate longitudinal variations in EPBs' zonal drift velocities at the magnetic equator and equatorial ionization anomaly (EIA) crestsIndication of the effect of small spatial scale E‐region density, electric field, neutral wind variations, or a combination of them [ABSTRACT FROM AUTHOR]