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12 pages, 14170 KB

Open AccessArticle

Variations in Pulsating Aurora Emission in 337 nm and 391 nm Nitrogen Spectral Lines during Geomagnetic Substorms

by Pavel Klimov, Vera Nikolaeva, Alexander Belov, Boris Kozelov, Alexei Murashov, Alexei Roldugin and Sergei Sharakin

Universe 2023, 9(10), 441; https://doi.org/10.3390/universe9100441 - 30 Sep 2023

Cited by 4 | Viewed by 2805

Abstract

Spectroscopic measurements of aurora emissions provide valuable insights into the altitude of electron atmospheric penetration and their maximum energy. To achieve this, the photometers used in the PAIPS (Pulsating Aurora Imaging Photometers System) project are equipped with spectrometers. These spectrometers enable the measurement of auroral emissions in narrow spectral lines with a temporal resolution of milliseconds. In this study, we present two cases of PsA (Pulsating Aurora) measurements in the 337 nm and 391 nm spectral lines. We demonstrate that during quiet geomagnetic conditions the ratio of night sky emissions in these bands is close to one and significantly increases during substorms. We propose and implement a special procedure for estimating this ratio. Our findings reveal that the intensity of emissions in both spectral lines correlates with the AL index of geomagnetic activity. However, the ratio between the emissions fluctuates around constant values over time and does not undergo significant changes throughout the entire PsA event, which can last for more than an hour. Full article

(This article belongs to the Special Issue Auroral Physics)

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16 pages, 4112 KB

Open AccessArticle

Comparative Study of Dayside Pulsating Auroras Induced by Ultralow-Frequency Waves

by Xing-Yu Li, Qiu-Gang Zong, Jian-Jun Liu, Ze-Fan Yin, Ze-Jun Hu, Xu-Zhi Zhou, Chao Yue, Zhi-Yang Liu, Xing-Xin Zhao, Zi-Kang Xie, J. Bernard Blake, Christopher T. Russell, Robert E. Ergun and Per-Arne Lindqvist

Universe 2023, 9(6), 258; https://doi.org/10.3390/universe9060258 - 29 May 2023

Cited by 6 | Viewed by 2501

Abstract

Pulsating auroras are usually observed with ultralow-frequency (ULF) waves in the Pc 3–5 band (period 10–600 s). These auroras are thought to result from interactions between energetic electrons and chorus waves, but their relationship with ULF waves remains an open question. In this study, we investigated this question by conducting a comparative study on two ULF wave events with pulsating auroras observed near the magnetic footprints. Conjugate observations from the Magnetospheric Multiscale mission and the Chinese Yellow River Station were used. In both events, lower-band chorus waves were observed, which were suggested to be connected with the auroral pulsations by wavelet analysis. The intensity of these waves oscillates at the period of the ULF waves, but the physics laid behind them differs by events. During the event of 22 January 2019, compressional ULF waves changed the threshold for the whistler anisotropy instability periodically, affecting the emission of chorus waves. In the event on 10 January 2016, poloidal ULF waves modulated the chorus wave generation by regulating electron temperature anisotropy through drift resonance. ULF waves in these events may originate from perturbations in the solar wind. We highlight the role of ULF waves in the solar wind–magnetosphere–ionosphere coupling, which requires further study. Full article

(This article belongs to the Section Space Science)

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11 pages, 1608 KB

Open AccessCommunication

Near-UV Pulsations in the Aurora Region Measured by Orbital Telescope TUS during High-Intensity and Long-Duration Continuous AE Activity

by Pavel Klimov, Vladimir Kalegaev, Ksenia Sigaeva, Alexandra Ivanova, Grigory Antonyuk, Viktor Benghin and Ivan Zolotarev

Remote Sens. 2023, 15(1), 147; https://doi.org/10.3390/rs15010147 - 27 Dec 2022

Cited by 5 | Viewed by 2528

Abstract

Tracking Ultraviolet Set-up (TUS) on board the Lomonosov satellite measured the UV intensity pulsations in the auroral region. Sixty-four events with pulsations were registered during two measurement periods from 26 December 2016–10 January 2017 and 8–15 November 2017. During both periods, a high-intensity, long-duration, continuous auroral activity (HILDCAA) was detected. Simultaneous measurements in LEO by Lomonosov (DEPRON detector) and Meteor-M2 satellites show the enhanced fluxes of the trapped and precipitated energetic electrons in the region of the Earth’s outer radiation belt during these periods. We found that most of the UV-events correspond to energetic electron (E > 100 keV) precipitation. One can suggest that particles of these and higher energies cause a pulsating emission relatively deep in the atmosphere. Full article

(This article belongs to the Special Issue Advances in Remote Sensing of Pulsating Aurora from Space and Earth)

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14 pages, 5127 KB

Open AccessArticle

Transient Flashes in Saturn’s UV Aurora: An Analysis of Hubble Space Telescope 2013–2017 Campaigns and Cassini Magnetic Field Measurements

by Tianshu Qin, Sarah V. Badman, Joe Kinrade and Alexander Bader

Universe 2022, 8(11), 602; https://doi.org/10.3390/universe8110602 - 17 Nov 2022

Cited by 1 | Viewed by 2550

Abstract

We examined Hubble Space Telescope images of Saturn’s northern UV aurora in 2013–2017, identified 29 short-lived flashes, and examined simultaneous magnetometer data collected by the Cassini orbiter. When observation cadence permitted, a flash lifetime of 4–17 min (subject to exposure time-related uncertainties), and [...] Read more.

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). These transient flashes are identified in both the presence and absence of Saturn’s main auroral oval, indicating the lack of dependence on the main emission power. The concurrent magnetic field pulsations generally form a sawtooth shape, and the local field strength experiences a change of 0.2 to 2.0 nT (depending on the distance of Cassini). The quasiperiodic pulsation events were all detected when the spacecraft was in the southern hemisphere with conjugate flashes in northern aurora, suggesting these events occur on closed field lines, and typically showing a sudden transition to a less lagging, more southward magnetic field configuration. We also found the ionospheric footprint of the spacecraft must be close to the region of flashes for magnetic field pulsations to be detected, implying a localised rather than global driving process. Full article

(This article belongs to the Special Issue Auroral Physics)

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13 pages, 14415 KB

Open AccessArticle

System of Imaging Photometers for Upper Atmospheric Phenomena Study in the Arctic Region

by Pavel Klimov, Sergei Sharakin, Alexander Belov, Boris Kozelov, Alexei Murashov, Roman Saraev, Daniil Trofimov, Alexei Roldugin and Vladimir Lubchich

Atmosphere 2022, 13(10), 1572; https://doi.org/10.3390/atmos13101572 - 26 Sep 2022

Cited by 17 | Viewed by 2809

Abstract

A Pulsating Aurora Imaging Photometers Stereoscopic System (PAIPS) is suggested and described in the paper. The system is based on two lens telescopes with a matrix of multianode photomultiplier tubes as photodetectors placed in two high latitude observatories of the Polar Geophysical Institute. Telescopes provide simultaneous observations of a large volume of the atmosphere at altitudes in the range 50–100 km with high temporal resolution (up to 2.5

μ

s) and a spatial resolution of about 2 km. This is a novel system for pulsating aurora study aimed to determine the energies of precipitating electrons responsible for the pulsating aurora occurrence. The system can be used for other atmospheric phenomena studies: meteors, transient luminous events, etc. One telescope has been operating since September 2021 and has measured a variety of optical phenomena. Full article

(This article belongs to the Special Issue Mesosphere and Lower Thermosphere)

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