Equatorial aurora: the aurora-like airglow in the negative magnetic anomaly

Abstract

The most fantastic optical phenomena in the Earth's upper atmosphere are the auroras. They are highly informative indicators of solar activity, geomagnetic activity, upper atmospheric structures and dynamics, and magnetospheric energetic particles. An area where the geomagnetic field differs significantly from the expected symmetric dipole, such as at the South Atlantic Anomaly, where the magnetic field intensity is low, gives rise to stronger precipitation of energetic particles into the upper atmosphere. Impact excitation and the subsequent airglow emissions exhibit aurora-like dynamic signatures. Nomenclatures of nonpolar aurora or equatorial auroras are similar to those used with the polar auroras owing to their similar excitation mechanisms. This paper provides an overview of the knowledge and the challenges concerning auroral activity at the South Atlantic Anomaly, or more generally, at the negative magnetic anomaly. We emphasize systematic investigation of the equatorial auroras to reveal the temporal and spatial evolution of the magnetic anomaly and the behaviour of energetic particles in near-Earth space.

Correlations Between Giant Undulations and Plasmapause Configurations

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The magnetosphere-plasmasphere-ionosphere energy coupling in geospace is one of the key focuses in the space physics and space weather researches. The coupling is primarily represented by the mass, energy and moment in solar wind entering into and convecting in the magnetosphere, transforming between waves and particles in the inner magnetosphere, being released into the ionosphere and upper atmosphere and eventually generating spectacular auroras in the Earth's polar region (e.g., Angelopoulos et al, 2008;Lyon, 2000) and even the equatorial region (He, Wei, & Wan, 2020;He et al, 2021). The inner magnetosphere, as one of the important regions where the mass and energy couple and diffuse, contains the plasmasphere, the ring current and the radiation belts.

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Climatological predictions of the auroral zone locations driven by moderate and severe space weather events

“…In contrast, aurorae sightings during the Carrington event have been reported in regions far more equatorward than the AACGM latitude marking the equatorward edge of the danger zones. This can be due to details of the Carrington event not captured by the climatological nature of our study, but it has to be noted that some of the mid-to-low latitude events could be equatorial aurorae 36 , associated with a phenomenology that is not included in our danger zone definition.…”

Equatorial auroral records reveal dynamics of the paleo-West Pacific geomagnetic anomaly

“…The structure of the internally generated magnetic field has profound consequences for Earth's atmosphere. Close to low-intensity regions of magnetic field, precipitation of energetic particles can reach ∼100 km altitude (9,10) and produces a unique type of dynamic red equatorial aurora in the night sky, which is totally different from the traditional chemicalrelated stable red airglow in regions of more typical magnetic intensity. As the result of particle deposition during the times of geomagnetic disturbance, the red equatorial aurora exhibits polar aurora-like dynamic signatures and is significantly stronger than the traditional red airglow (10).…”