Asymmetric Development of Auroral Surges in the Northern and Southern Hemispheres

Uchida, Herbert Akihito; Kataoka, Ryuho; Kadokura, Akira; Murase, Kiyoka; Yukimatu, A. S.; Miyoshi, Yoshizumi; Ebihara, Yusuke; Hosokawa, K.; Matsuoka, A.; Kurita, Satoshi; Fujita, Shigeru; Shinohara, I.

doi:10.1029/2020gl088750

Cited by 2 publications

(2 citation statements)

References 44 publications

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“…While there are few studies about simultaneous AKR observations in the two hemispheres, it is different for the observations of auroras. There are numerous reports about auroral asymmetry detected either from ground‐based receivers or from satellites (see for example, Liou & Mitchell, 2019; Liou et al., 2018; Luan et al., 2010, 2016; Newell et al., 2010; Østgaard et al., 2015, 2018; Reistad et al., 2013; Uchida et al., 2020). But here also it is difficult to find similar characteristics for the occurrences of AKR‐like emissions and auroras.…”

Section: Discussionmentioning

confidence: 99%

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Properties of AKR‐Like Emissions Recorded by the Low Altitude Satellite DEMETER During 6.5 Years

2022

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Normally, auroral kilometric radiation (AKR) which is emitted in the auroral zones escapes from the Earth. But since a few decades very similar radiations are observed by ground‐based receivers and by satellites at altitudes below the AKR generation area. They are called leaked AKR or AKR‐like emissions because it is expected that there are linked to AKR. This paper deals with observations of such AKR‐like emissions observed in the auroral zones (in the North and in the South) by the low‐altitude satellite DEMETER. In total, 2,526 events have been recorded during 6.5 years. These events are not very rare as they occur at least 2% of the time. Although this data set has a severe flaw due to a latitudinal constraint, it was possible to draw interesting properties of these emissions. In fact they are very similar to usual AKR observed at much higher altitudes during auroral activities (the same frequency range, magnetic local time (MLT) sector, and invariant latitude). The main difference concerns a strong asymmetry between the Northern and the Southern hemispheres: (a) the number of AKR‐like emissions in the Northern hemisphere is 32% larger than in the Southern hemisphere but this percentage decreases when the auroral activity increases, and (b) there is an important seasonal effect because the number of events decreases during the winter season both in the North and in the South.

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Section: Discussionmentioning

confidence: 99%

“…Uchida et al (2020) performed simultaneous observations of auroras at Tjörnes, Iceland, and Syowa station, Antarctica and they observed a shift of 1.7-2.3 hr in MLT in the South in relation to the North.…”

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Properties of AKR‐Like Emissions Recorded by the Low Altitude Satellite DEMETER During 6.5 Years

2022

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Mesospheric ionization during substorm growth phase

Murase

Kataoka

Nishiyama

et al. 2022

J. Space Weather Space Clim.

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Many studies have been conducted about the impact of energetic charged particles on the atmosphere during geomagnetically active times, while quiet time effects are poorly understood. We identified two energetic electron precipitation (EEP) events during the growth phase of moderate substorms and estimated the mesospheric ionization rate for an EEP event for which the most comprehensive dataset from ground-based and space-born instruments was available. The mesospheric ionization signature reached below 70 km altitude and continued for ~15 min until the substorm onset, as observed by the PANSY radar and imaging riometer at Syowa Station in the Antarctic region. We also used energetic electron flux observed by the Arase and POES 15 satellites as the input for the air-shower simulation code PHITS to quantitatively estimate the mesospheric ionization rate. The calculated ionization level due to the precipitating electrons is consistent with the observed value of cosmic noise absorption. The possible spatial extent of EEP is estimated to be ~8 h MLT in longitude and ~1.5° in latitude from a global magnetohydrodynamic simulation REPPU and the precipitating electron observations by the POES satellite, respectively. Such a significant duration and spatial extent of EEP events suggest a non-negligible contribution of the growth phase EEP to the mesospheric ionization. Combining the cutting-edge observations and simulations, we shed new light on the space weather impact of the EEP events during geomagnetically quiet times, which is important to understand the possible link between the space environment and climate.

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Asymmetric Development of Auroral Surges in the Northern and Southern Hemispheres

Cited by 2 publications

References 44 publications

Properties of AKR‐Like Emissions Recorded by the Low Altitude Satellite DEMETER During 6.5 Years

Properties of AKR‐Like Emissions Recorded by the Low Altitude Satellite DEMETER During 6.5 Years

Mesospheric ionization during substorm growth phase

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