Observations of Electron Precipitation During Pulsating Aurora and Its Chemical Impact

Tesema, Fasil; Partamies, Noora; Tyssøy, Hilde Nesse; Kero, Antti; Smith‐Johnsen, Christine

doi:10.1029/2019ja027713

Cited by 29 publications

(53 citation statements)

References 59 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is also possible to find cases where energies of APA electrons are higher than those of PPA electrons, specifically in the energy range below the energy limit (30 keV) measured by FAST. The stopping altitude of these electrons is above 95 km (Turunen et al, 2009). However, in this study, most of the energy (ionization) differences between the types were observed below 100 km.…”

Section: Discussioncontrasting

confidence: 53%

“…They further indicated that the intense ionization could lead to a significant effect on the ionospheric conductivity and current system and, in turn, affect the motion and shapes of PsA patches. Hard precipitation of PsA electrons is known to reach below 70 km and can ionize and change the chemistry of the mesosphere (Turunen et al, 2009(Turunen et al, , 2016Tesema et al, 2020). It has also been shown by model results that not all PsA electrons cause strong ionization and chemical changes (Tesema et al, 2020).…”

Section: Introductionmentioning

confidence: 97%

See 1 more Smart Citation

Observations of precipitation energies during different types of pulsating aurora

et al. 2020

Self Cite

View full text Add to dashboard Cite

Abstract. Pulsating aurora (PsA) is a diffuse type of aurora with different structures switching on and off with a period of a few seconds. It is often associated with energetic electron precipitation (>10 keV) resulting in the interaction between magnetospheric electrons and electromagnetic waves in the magnetosphere. Recent studies categorize pulsating aurora into three different types – amorphous pulsating aurora (APA), patchy pulsating aurora (PPA), and patchy aurora (PA) – based on the spatial extent of pulsations and structural stability. Differences in precipitation energies of electrons associated with these types of pulsating aurora have been suggested. In this study, we further examine these three types of pulsating aurora using electron density measurements from the European Incoherent Scatter (EISCAT) VHF/UHF radar experiments and Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) cosmic noise absorption (CNA) measurements. Based on ground-based all-sky camera images over the Fennoscandian region, we identified a total of 92 PsA events in the years between 2010 and 2020 with simultaneous EISCAT experiments. Among these events, 39, 35, and 18 were APA, PPA, and PA types with a collective duration of 58, 43, and 21 h, respectively. We found that, below 100 km, electron density enhancements during PPAs and PAs are significantly higher than during APA. However, there are no appreciable electron density differences between PPA and APA above 100 km, while PA showed weaker ionization. The altitude of the maximum electron density also showed considerable differences among the three types, centered around 110, 105, and 105 km for APA, PPA, and PA, respectively. The KAIRA CNA values also showed higher values on average during PPA (0.33 dB) compared to PA (0.23 dB) and especially APA (0.17 dB). In general, this suggests that the precipitating electrons responsible for APA have a lower energy range compared to PPA and PA types. Among the three categories, the magnitude of the maximum electron density shows higher values at lower altitudes and in the late magnetic local time (MLT) sector (after 5 MLT) during PPA than during PA or APA. We also found significant ionization down to 70 km during PPA and PA, which corresponds to ∼200 keV of precipitating electrons.

show abstract

Section: Discussioncontrasting

confidence: 53%

Section: Introductionmentioning

confidence: 97%

Observations of precipitation energies during different types of pulsating aurora

et al. 2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…The energetic electron precipitation (EEP) that produces PsA is thought to arise from chorus wave activity, whereby electrons from the radiation belts are scattered into the atmospheric loss cone (Thorne et al, 2010;Kasahara et al, 2018). The precipitating electrons typically have energies up to the order of 10-100 keV, depositing their energy into the upper mesosphere/lower thermosphere region at approximately 70-120 km altitude (Fang et al, 2008;Turunen et al, 2009;Miyoshi et al, 2010;Tesema et al, 2020b). PsA-related electron density enhancements have been observed at altitudes as low as 68 km, corresponding to electron energies of at least 200 keV (Miyoshi et al, 2015;Turunen et al, 2016;Tesema et al, 2020a).…”

Section: Introductionmentioning

confidence: 99%

D-region impact area of energetic electron precipitation during pulsating aurora

Bland¹,

Tesema

Partamies

2021

Ann. Geophys.

Self Cite

View full text Add to dashboard Cite

Abstract. A total of 10 radars from the Super Dual Auroral Radar Network (SuperDARN) in Antarctica were used to estimate the spatial area over which energetic electron precipitation (EEP) impacts the D-region ionosphere during pulsating aurora (PsA) events. We use an all-sky camera (ASC) located at Syowa Station to confirm the presence of optical PsAs, and then we use the SuperDARN radars to detect high frequency (HF) radio attenuation caused by enhanced ionisation in the D-region ionosphere. The HF radio attenuation was identified visually by examining quick-look plots of the background HF radio noise and backscatter power from each radar. The EEP impact area was determined for 74 PsA events. Approximately one-third of these events have an EEP impact area that covers at least 12∘ of magnetic latitude, and three-quarters cover at least 4∘ of magnetic latitude. At the equatorward edge of the auroral oval, 44 % of events have a magnetic local time extent of at least 7 h, but this reduces to 17 % at the poleward edge. We use these results to estimate the average size of the EEP impact area during PsAs, which could be used as a model input for determining the impact of PsA-related EEP on the atmospheric chemistry.

show abstract

“…Increased ionization in the D region leads to enhanced absorption of the cosmic noise, and at D-region heights this is mainly due to precipitation of electrons with energies above 10 keV (e.g. Turunen et al, 2009). The SGO riometers are wide-beam instruments which listen to the cosmic noise at approximately 30 MHz.…”

Section: From Cosmic Noise Absorption To a Regional Absorption Indexmentioning

confidence: 99%

“…The one-dimensional Sondakylä Ion and Neutral Chemistry model (e.g. Turunen et al, 2009) was run to investigate the production of odd hydrogen (HO x = OH+HO 2 ) and odd nitrogen (NO x = N+NO+NO 2 ) due to the strong ionization at the bottom part of the ionosphere and the following catalytic depletion of mesospheric ozone. The peak loss of mesospheric ozone was found to be 10 %-50 % depending on the season.…”

Section: Introductionmentioning

confidence: 99%

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

Partamies

Tesema

Bland³

et al. 2021

Ann. Geophys.

Self Cite

View full text Add to dashboard Cite

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 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 categorized. 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 show 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.

show abstract

Observations of Electron Precipitation During Pulsating Aurora and Its Chemical Impact

Cited by 29 publications

References 59 publications

Observations of precipitation energies during different types of pulsating aurora

Observations of precipitation energies during different types of pulsating aurora

D-region impact area of energetic electron precipitation during pulsating aurora

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

Contact Info

Product

Resources

About