Pulsating aurora and cosmic noise absorption associated with growth-phase arcs

McKay, D. J.; Partamies, Noora; Vierinen, Juha

doi:10.5194/angeo-36-59-2018

Cited by 16 publications

(20 citation statements)

References 27 publications

(41 reference statements)

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“…In total, 70 events included CNA enhancements during the growth phases prior to the onset. These signatures are similar to the growth phase CNA observations reported by, e.g., McKay et al (2018) and Sergeev et al (2012). The large majority of events with growth phase CNA signatures (66 events) were compound or multi-night events.…”

Section: Discussionsupporting

confidence: 86%

Electron precipitation characteristics during isolated, compound and multi-night substorm events

Partamies¹,

Tesema²,

Bland³

et al. 2020

Preprint

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Abstract. A set of 24 isolated, 46 compound and 36 multi-night substorm events from the years 2008–2013 have been analysed in this study. Isolated substorm events are defined as single expansion-recovery phase pairs, compound substorms consist of multiple phase pairs, and multi-night substorm events refer to recurring substorm activity on consecutive nights. Approximately 200 nights of substorm activity observed over the Fennoscandian Lapland have been analysed for their magnetic disturbance magnitude and the level of cosmic radio noise absorption. Substorm events were automatically detected from the local electrojet index data and visually categorised. We show that isolated substorms have limited lifetimes and spatial extents, as compared to the other substorm types. The average intensity (both in absorption and ground-magnetic deflection) of compound and multi-night substorm events is similar. For multi-night substorm events, the first night is rarely associated with the strongest absorption. Instead, the high-energy electron population needed to cause the strongest absorption builds up over 1–2 additional nights of substorm activity. The non-linear relationship between the absorption and the magnetic deflection at high and low activity conditions is also discussed. We further collect in-situ particle spectra for expansion and recovery phases to construct median precipitation fluxes at energies from 30 eV up to about 800 keV. In the expansion phases the bulk of the spectra shows a local maximum flux in the range of a few keV to 10 keV, while in the recovery phases higher fluxes are seen in the range of tens of keV to hundreds of keV. These findings are discussed in the light of earlier observations of substorm precipitation and their atmospheric effects.

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Section: Discussionsupporting

confidence: 86%

Electron precipitation characteristics during isolated, compound and multi-night substorm events

Partamies¹,

Tesema²,

Bland³

et al. 2020

Preprint

Self Cite

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“…Pulsating auroral patches observed during substorm expansion phases have a tendency to grow in size, while the more common patches seen during the substorm recovery phases mainly decrease in size (Partamies et al, 2019). Pulsating auroral patches have recently been found within the growth phase auroral arc of a substorm (McKay et al, 2018).…”

Section: Pulsating Aurora Relation To Substormsmentioning

confidence: 99%

“…The absorption is primarily a result of the Dregion ionosphere, ionized by high energy precipitation, UV and X-rays. In the last two decades, imaging riometers have been built that can be used to image the spatial structure of energetic precipitation (Honary et al, 2011;Kosch et al, 2001;McKay et al, 2018).…”

Section: Recent Advances 21 Observation Techniquementioning

confidence: 99%

Diffuse and Pulsating Aurora

et al. 2020

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This chapter reviews fundamental properties and recent advances of diffuse and pulsating aurora. Diffuse and pulsating aurora often occurs on closed field lines and involves energetic electron precipitation by wave-particle interaction. After summarizing the definition, large-scale morphology, types of pulsation, and driving processes, we review observation techniques, occurrence, duration, altitude, evolution, small-scale structures, fast modulation, relation to high-energy precipitation, the role of ECH waves, reflected and secondary electrons, ionosphere dynamics, and simulation of wave-particle interaction. Finally we discuss open questions of diffuse and pulsating aurora.

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“…The offset between the growth phase and the CNA arc is nearly uniform during the equatorward progression of the growth‐phase arc. McKay et al () also observed optical pulsating aurora between the diffuse emission and the main growth‐phase arc, colocated with CNA. In the same study, fast‐moving auroral patches were seen to traverse the sky, in the same region where the optical pulsations later appeared.…”

Section: Introductionmentioning

confidence: 93%

Lumikot: Fast Auroral Transients During the Growth Phase of Substorms

McKay

Paavilainen

Gustavsson

et al. 2019

Geophysical Research Letters

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The development of a magnetospheric substorm may be classified into three phases: growth, expansion, and recovery. The growth phase is important as it includes processes that lead to the expansion. In a recent growth‐phase study, a type of fast discrete auroral transient phenomena—referred to as Lumikot—were observed. The Lumikot are several kilometers across and move in the high‐energy precipitation region, parallel to the main growth‐phase arc, with both east‐west and west‐east directions of travel during the same event. Their apparent transverse movement and quasi‐stable intensity make them distinct from cooccurring optical pulsating aurorae. Comparison to other studies show that they occur in the cosmic noise absorption region and it is likely that the Lumikot are colocated with high‐energy particle populations on the boundary between the outer radiation belt and the plasmasheet.

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Pulsating aurora and cosmic noise absorption associated with growth-phase arcs

Cited by 16 publications

References 27 publications

Electron precipitation characteristics during isolated, compound and multi-night substorm events

Electron precipitation characteristics during isolated, compound and multi-night substorm events

Diffuse and Pulsating Aurora

Lumikot: Fast Auroral Transients During the Growth Phase of Substorms

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