Observation of pulsating aurora signatures in cosmic noise absorption data

Grandin, Maxime; Kero, Antti; Partamies, Noora; McKay, D. J.; Whiter, Daniel; Kozlovsky, Alexander; Miyoshi, Yoshizumi

doi:10.1002/2017gl073901

Cited by 23 publications

(39 citation statements)

References 44 publications

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“…Although pulsations in CNA during the recovery phase have been reported before (Grandin et al, 2017), no evidence of CNA pulsations are seen in any of the growth-phase events reported in this study. One possible reason is that the pulsation region is relatively narrow in latitude in the growth phase.…”

Section: Discussioncontrasting

confidence: 49%

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

McKay¹,

Partamies²,

Vierinen³

2018

Ann. Geophys.

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Abstract. The initial stage of a magnetospheric substorm is the growth phase, which typically lasts 1-2 h. During the growth phase, an equatorward moving, east-west extended, optical auroral arc is observed. This is called a growth-phase arc. This work aims to characterize the optical emission and riometer absorption signatures associated with growth-phase arcs of isolated substorms. This is done using simultaneous all-sky camera and imaging riometer observations. The optical and riometric observations allow determination of the location of the precipitation within growth-phase arcs of low-( < 10 keV) and high-(> 10 keV) energy electrons, respectively. The observations indicate that growth-phase arcs have the following characteristics:1. The peak of the cosmic noise absorption (CNA) arc is equatorward of the optical emission arc. This CNA is contained within the region of diffuse aurora on the equatorward side.2. Optical pulsating aurora are seen in the border region between the diffuse emission region on the equatorward side and the bright growth-phase arc on the poleward side. CNA is detected in the same region.3. There is no evidence of pulsations in the CNA.4. Once the equatorward drift starts, it proceeds at constant speed, with uniform separation between the growthphase arc and CNA of 40 ± 10 km.Optical pulsating aurora are known to be prominent in the post-onset phase of a substorm. The fact that pulsations are also seen in a fairly localized region during the growth phase shows that the substorm expansion-phase dynamics are not required to closely precede the pulsating aurora.

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Section: Discussioncontrasting

confidence: 49%

“…Satellite-based observations suggest that they are caused by time-varying flux of high-energy (> 10 keV) electrons (Wing et al, 2013). Weak pulsations in the CNA with close correlation to the optical phenomena have been reported (Brekke, 1971;Grandin et al, 2017).…”

mentioning

confidence: 99%

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

McKay¹,

Partamies²,

Vierinen³

2018

Ann. Geophys.

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“…Precipitation can occur also during pulsating aurora and exhibit modulation at similar timescales as the auroral emission (e.g. Grandin et al, 2017b).…”

Section: Introductionmentioning

confidence: 99%

Cosmic noise absorption signature of particle precipitation during interplanetary coronal mass ejection sheaths and ejecta

et al. 2020

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Abstract. We study here energetic-electron (E>30 keV) precipitation using cosmic noise absorption (CNA) during the sheath and ejecta structures of 61 interplanetary coronal mass ejections (ICMEs) observed in the near-Earth solar wind between 1997 and 2012. The data come from the Finnish riometer (relative ionospheric opacity meter) chain from stations extending from auroral (IVA, 65.2∘ N geomagnetic latitude; MLAT) to subauroral (JYV, 59.0∘ N MLAT) latitudes. We find that sheaths and ejecta lead frequently to enhanced CNA (>0.5 dB) both at auroral and subauroral latitudes, although the CNA magnitudes stay relatively low (medians around 1 dB). Due to their longer duration, ejecta typically lead to more sustained enhanced CNA periods (on average 6–7 h), but the sheaths and ejecta were found to be equally effective in inducing enhanced CNA when relative-occurrence frequency and CNA magnitude were considered. Only at the lowest-MLAT station, JYV, ejecta were more effective in causing enhanced CNA. Some clear trends of magnetic local time (MLT) and differences between the ejecta and sheaths were found. The occurrence frequency and magnitude of CNA activity was lowest close to midnight, while it peaked for the sheaths in the morning and afternoon/evening sectors and for the ejecta in the morning and noon sectors. These differences may reflect differences in typical MLT distributions of wave modes that precipitate substorm-injected and trapped radiation belt electrons during the sheaths and ejecta. Our study also emphasizes the importance of substorms and magnetospheric ultra-low-frequency (ULF) waves for enhanced CNA.

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“…Later, several statistical analyses confirmed that pulsating aurora is often associated with CNA (e.g., Arnoldy et al, ; Brekke, ). Recently, Grandin et al () showed an event in which there was a one‐on‐one correlation between the auroral pulsations quantified by the auroral blue‐line emission (427.8 nm) from an all‐sky camera and the variations in CNA obtained from a multibeam experiment of the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA; McKay‐Bukowski et al, ).…”

Section: Introductionmentioning

confidence: 99%

Responses of Different Types of Pulsating Aurora in Cosmic Noise Absorption

Yang

Spanswick

Liang

et al. 2019

Geophysical Research Letters

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A recent study (Grono & Donovan, 2018, https://doi.org/10.5194/angeo-36-891-2018) reported two distinct categories of pulsating aurora: patchy pulsating aurora (PPA) and amorphous pulsating aurora (APA). In this study we compare the auroral intensity of five PPA events and seven APA events monitored by the Time History of Events and Macroscale Interactions during Substorms (THEMIS) All‐Sky Imagers with co‐located cosmic noise absorption (CNA) from the Geospace Observatory wide‐beam riometers. Our results show significant correlations between CNA and the auroral intensity of the APA events but no correlation between CNA and the auroral intensity of the PPA events. Analysis of conjunctions with the electron flux data obtained from the FAST satellite, we found that electrons responsible for APA may extend to higher energy range than those for PPA.

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Observation of pulsating aurora signatures in cosmic noise absorption data

Cited by 23 publications

References 44 publications

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

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

Cosmic noise absorption signature of particle precipitation during interplanetary coronal mass ejection sheaths and ejecta

Responses of Different Types of Pulsating Aurora in Cosmic Noise Absorption

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