Abstract
Data from three all-sky cameras in Kiruna and Tjautjas (Sweden) were used to estimate the altitude of pulsating arc-like forms using optical tomography. The event under consideration occurred during the substorm recovery phase and comprised both periodic luminosity variation of the on/off type with repetition periods of 3–6 s (main pulsations) and faster scintillation (approximately 2 Hz) during the “on” phase of the main pulsations. It is found that (1) the altitudes of the pulsating auroral arcs decrease during “on” intervals from ~ 95 km to ~ 92 km and (2) for two closely spaced arcs, internal modulation took place only in the lowest arc. The results may be interpreted in the frame of the traditional mechanism assuming electron scattering via VLF-wave/particle interaction in the equatorial magnetosphere, while the internal modulation may also be alternatively interpreted in the frame of the less-often inferred mechanism of field-aligned acceleration somewhere between the equatorial plane and ionosphere.Graphical
Highlights
IntroductionSafargaleev et al Earth, Planets and Space (2022) 74:31 or more regular arc/segment structures with quasi-periodic on–off switching of its intensity
Pulsating aurora (PsA) is the name given to a kind of diffuse aurora that appears, in general, as irregular patchesSafargaleev et al Earth, Planets and Space (2022) 74:31 or more regular arc/segment structures with quasi-periodic on–off switching of its intensity
The Elec‐ tron multiplying charge-coupled device (EMCCD) all-sky camera in Tjautjas (TJA; 67.31°N, 20.73°E), Sweden, that was installed under the PsA research project and PWING project (e.g., Shiokawa et al 2017) gives 100 images per second that allow us to detect both the main pulsations and the internal modulation in PsA
Summary
Safargaleev et al Earth, Planets and Space (2022) 74:31 or more regular arc/segment structures with quasi-periodic on–off switching of its intensity. Most of the known characteristics of PsA have been reviewed by Royrvik and Davis (1977), Johnstone (1978), Lessard (2012), Nishimura et al (2020). Royrvik and Davis (1977) established three general morphologies: east–west aligned arcs, quasi-linear elements, and patches. The latter are regarded as the most common form of PsA and may be divided into three subcategories (Grono and Donovan 2020).
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