Fine structure of the polar ionosphere in the midnight auroral zone during substorm activity: relationship between auroral electrojets, riometer absorption, auroral luminosity, ionospheric conductivity, and field-aligned currents

1993 ◽  
Author(s):  
A. L. Kotikov ◽  
q. M. Shishkina ◽  
Oleg A. Troshichev
Keyword(s):  
Fine Structure ◽  
Auroral Zone ◽  
Activity Relationship ◽  
Polar Ionosphere ◽  
Ionospheric Conductivity ◽  
Substorm Activity ◽  
Auroral Luminosity

Use of fractal approach to investigate ionospheric conductivity in the auroral zone

2013 ◽  
Vol 118 (7) ◽  
pp. 4108-4118 ◽  
Author(s):  
A. A. Chernyshov ◽  
M. M. Mogilevsky ◽  
B. V. Kozelov
Keyword(s):  
Auroral Zone ◽  
Ionospheric Conductivity ◽  
Fractal Approach

scholarly journals Investigations of the auroral luminosity distribution and the dynamics of discrete auroral forms in a historical retrospective

2014 ◽  
Vol 5 (1) ◽  
pp. 81-134 ◽  
Author(s):  
Y. I. Feldstein ◽  
V. G. Vorobjev ◽  
V. L. Zverev ◽  
M. Förster
Keyword(s):  
Local Time ◽  
18Th Century ◽  
Spectral Composition ◽  
Auroral Oval ◽  
Auroral Zone ◽  
Planetary Scale ◽  
Magnetospheric Convection ◽  
International Geophysical Year ◽  
Auroral Substorm ◽  
Auroral Luminosity

Abstract. Research results about planetary-scale auroral distributions are presented in a historical retrospective, beginning with the first "maps of isochasms" – lines of equal visibility of auroras in the firmament (Fig. 2) – up to "isoaurora maps" – lines of equal occurrence frequency of auroras in the zenith (Fig. 4). The exploration of auroras in Russia from Lomonosov in the 18th century (Fig. 1) until the start of the International Geophysical Year (IGY) in 1957 is shortly summed up. A generalised pattern of discrete auroral forms along the auroral oval during geomagnetically very quiet intervals is presented in Fig. 5. The changes of discrete auroral forms versus local time exhibit a fixed pattern with respect to the sun. The auroral forms comprise rays near noon, homogeneous arcs during the evening, and rayed arcs and bands during the night and in the morning. This fixed auroral pattern is unsettled during disturbances, which occur sometimes even during very quiet intervals. The azimuths of extended auroral forms vary with local time. Such variations in the orientation of extended forms above stations in the auroral zone have been used by various investigators to determine the position of the auroral oval (Fig. 9). Auroral luminosity of the daytime and nighttime sectors differ owing to different luminosity forms, directions of motion of the discrete forms, the height of the luminescent layers, and the spectral composition (predominant red emissions during daytime and green emissions during the night). Schemes that summarise principal peculiarities of daytime luminosity, its structure in MLT (magnetic local time) and MLat (magnetic latitude) coordinates, and the spectral composition of the luminosity are presented in Figs. 15 and 19. We discuss in detail the daytime sector dynamics of individual discrete forms for both quiet conditions and auroral substorms. The most important auroral changes during substorms occur in the nighttime sector. We present the evolution of conceptions about the succession of discrete auroral forms and their dynamics during disturbance intervals. This ranges from Birkeland's polar elementary storms, over the prospect of a fixed auroral pattern up to the auroral substorm model. The classic schemes of the spatial distribution and motion of discrete auroral forms during single substorms are shown in Fig. 20 (expansive and recovery phases) and Fig. 21 (creation, expansive and recovery phases). In this review we discuss various models of bulge formation, in particular as a result of new formation of arcs about 50–100 km poleward of previously existing auroral structures (Fig. 24). Discrete steps in the development of an expanding bulge are separated by 1–3 min from each other. The model of successive activations confines only to a ~40° longitudinal portion of the magnetotail (Fig. 28). We consider differences in the development of single substorms and substorms during magnetic storms. The structure and dynamics of auroras during steady magnetospheric convection (SMC) periods are dealt with in Sect. 8. A generalised scheme of the auroral distribution during SMC periods is shown in Fig. 34. Separate sections describe discrete auroras in the polar cap (Sect. 5), and the diffuse luminosity equatorward of the auroral oval (Sect. 9). Visual observations of diffuse auroral forms at midlatitudes suggest that the whole latitudinal interval between the auroral oval and the stable auroral red (SAR) arc is filled up with diffuse luminosity. SAR arcs with intensities of several tens of Rayleigh enclose systematically the region of diffuse luminosity; they are positioned at the border of the plasmasphere.

scholarly journals Algorithm for numerical simulation of electron density and stochastically convecting high latitude ionosphere

2021 ◽  
Vol 2131 (2) ◽  
pp. 022013
Author(s):  
G Vlaskov
Keyword(s):  
Numerical Simulation ◽  
Electric Field ◽  
Electron Density ◽  
Large Scale ◽  
Ionospheric Plasma ◽  
Auroral Zone ◽  
Polar Ionosphere ◽  
Magnetospheric Convection ◽  
The Monte Carlo Method ◽  
High Latitude Ionosphere

Abstract The problem of modeling the inhomogeneities of the electron density in the polar ionosphere at the level of the F - layer is considered. It is known that the distribution of ionospheric plasma changes under the action of the electric field of large-scale magnetospheric convection. Since the electric field undergoes significant fluctuations in the auroral zone, it is proposed to use the Monte Carlo method to solve this problem, simulating the process of plasma motion, like the Wiener one with deterministic drift.

The diurnal and latitudinal variation of auroral zone ionospheric conductivity

1981 ◽  
Vol 86 (A1) ◽  
pp. 65 ◽  
Author(s):  
James F. Vickrey ◽  
Richard R. Vondrak ◽  
Stephen J. Matthews
Keyword(s):  
Auroral Zone ◽  
Latitudinal Variation ◽  
Ionospheric Conductivity

scholarly journals Observations of substorm fine structure

1998 ◽  
Vol 16 (7) ◽  
pp. 775-786 ◽  
Author(s):  
L. L. Lazutin ◽  
R. Rasinkangas ◽  
T. V. Kozelova ◽  
A. Korth ◽  
H. Singer ◽  
...  
Keyword(s):  
Fine Structure ◽  
Feedback Loop ◽  
Large Scale ◽  
Field Measurements ◽  
Magnetospheric Substorm ◽  
Line Configuration ◽  
Magnetic Field Measurements ◽  
Substorm Activity ◽  
Storms And Substorms ◽  
Geosynchronous Satellites

Abstract. Particle and magnetic field measurements on the CRRES satellite were used, together with geosynchronous satellites and ground-based observations, to investigate the fine structure of a magnetospheric substorm on February 9, 1991. Using the variations in the electron fluxes, the substorm activity was divided into several intensifications lasting about 3–15 minutes each. The two main features of the data were: (1) the intensifications showed internal fine structure in the time scale of about 2 minutes or less. We call these shorter periods activations. Energetic electrons and protons at the closest geosynchronous spacecraft (1990 095) were found to have comparable activation structure. (2) The energetic (>69 keV) proton injections were delayed with respect to electron injections, and actually coincided in time with the end of the intensifications and partial returns to locally more stretched field line configuration. We propose that the energetic protons could be able to control the dynamics of the system locally be quenching the ongoing intensification and possibly preparing the final large-scale poleward movement of the activity. It was also shown that these protons originated from the same intensification as the preceeding electrons. Therefore, the substorm instability responsible for the intensifications could introduce a negative feedback loop into the system, creating the observed fine structure with the intensification time scales.Key words. Magnetospheric Physics (Storms and substorms).

scholarly journals The structure-activity relationship between precursor fine structure and cathodes performance in Ni-rich layered oxide

2021 ◽  
Author(s):  
Lang Qiu ◽  
Mengke Zhang ◽  
Kanghui Hu ◽  
Yang Song ◽  
Zhenguo Wu ◽  
...  
Keyword(s):  
Particle Size ◽  
Fine Structure ◽  
Primary Particle ◽  
Structure Activity Relationship ◽  
Primary Particle Size ◽  
Activity Relationship ◽  
Particle Structure ◽  
Structural Degradation ◽  
Structure Activity ◽  
Depth Analysis

Abstract Cathode’s primary particle structure plays a key role in the performance of lithium ion batteries, which can be controlled by the precursor synthesis. Regretfully, the relevance between primary particle structure and cathode performance is not explicitly elucidated, that is, what is the discrepancy of cathode’s primary particle size on the structural degradation? In order to elaborate the structure-activity relationship between them, we have systematically investigated the regulation of primary particle size through an in-depth analysis of the precursor growth mechanism, ammonia-stirring coupling and hydrodynamics optimization. Structural and electrochemical characterizations of LiNi0.92Co0.04Mn0.04O2 with different primary sizes (336, 447, 565 and 675 nm) and a rounded analysis of structural degradation after cycling provide insight into the correlation between precursor fine structure and cathode performance, i.e. larger cathode’s primary particle size can effectively inhibit CEI film formation, structure decay, the intragranular/intergranular cracks formation owing to the alleviation of localized stress.

scholarly journals Solar cycle evolution of ULF wave power in solar wind and on ground

2020 ◽  
Vol 10 ◽  
pp. 43
Author(s):  
Reko Hynönen ◽  
Eija I. Tanskanen ◽  
Patrizia Francia
Keyword(s):  
Solar Wind ◽  
Solar Cycle ◽  
Solar Wind Speed ◽  
Low Frequency ◽  
Auroral Zone ◽  
Wave Power ◽  
Polar Cap ◽  
Ulf Wave ◽  
Substorm Activity ◽  
Ground Magnetic

The solar cycle evolution of the ultra-low frequency (ULF) power was studied in solar wind and on ground. We aim finding out how the ULF power in interplanetary and on ground magnetic field evolves over the solar cycle 23 (SC23) and how well do they follow each other in monthly time scales. The hourly power of the ULF waves was computed in the Pc5 frequency range 2–7 mHz for years 1998–2008. The highest wave power in SC23 is found to occur in late 2003 and the lowest at the solar minimum. Ground ULF power follows the IMF power and solar wind speed, particularly well during declining phase. The ULF power in winter exceeds the ULF power in other seasons during the declining phase of SC23, while equinoxes dominate in the ascending phase and the solar maximum. The ground ULF power was found to rise with magnetic latitude from 54° to 73°, after which Pc5 power decreases towards the polar cap. The Pc5 power in the auroral zone is larger in the nightside than the dayside due to substorm activity implying that magnetotail processes are an important contributor to the nightside ULF power.

High-latitude crochet (Solar flare effect) as a trigger of pseud-substorm onset

2021 ◽  
Author(s):  
Masatoshi Yamauchi ◽  
Magnar Johnsen ◽  
Shin-Ichi Othani ◽  
Dmitry Sormakov
Keyword(s):  
Solar Flare ◽  
High Latitude ◽  
Current System ◽  
Geomagnetic Latitude ◽  
Geomagnetic Disturbance ◽  
Substorm Onset ◽  
Ionospheric Conductivity ◽  
New Type ◽  
E Region ◽  
Substorm Activity

<p>Solar flares are known to enhance the ionospheric electron density and thus influence the electric currents in the D- and E-region.  The geomagnetic disturbance caused by this current system is called a "crochet" or "SFE (solar flare effect)".  Crochets are observed at dayside low-latitudes with a peak near the subsolar region ("subsolar crochet"), in the nightside high-latitude auroral region with a peak where the geomagnetic disturbance pre-exists during solar illumination ("auroral crochet"), and in the cusp ("cusp crochet").  In addition, we recently found a new type of crochet on the dayside ionospheric current at high latitudes (European sector 70-75 geographic latitude/67-72 geomagnetic latitude) independent from the other crochets.  The new crochet is much more intense and longer in duration than the subsolar crochet and is detected even in AU index for about half the >X2 flares despite the unfavorable latitudinal coverage of the AE stations (~65 geomagnetic latitude) to detect this new crochet (Yamauchi et al., 2020).  </p><p>The signature is sometime s seen in AL, causing the crochet signature convoluting with substorms.  From a theoretical viewpoint, X-flares that enhances the ionospheric conductivity may influence the substorm activity, like the auroral crochet.  To understand the substorm-crochet relation in the dayside, we examined SuperMAG data for cases when the onset of the substorm-like AL (SML) behavior coincides with the crochet.  We commonly found a large counter-clockwise ∆B vortex centered at 13-15 LT, causing an AU peak during late afternoon and an AL peak near noon at higher latitudes than the high-latitude crochet.  In addition, we could recognize a clockwise ∆B vortex in the prenoon sector, causing another poleward ∆B, but this signature is not as clear as the afternoon vortex.  With such strong vortex features, it becomes similar to substorms except for its local time.  In some cases, the vortex expends to the nightside sector, where and when nightside onset starts, suggesting triggering of onset.  Thus, the crochet may behave like pseudo-onset at different latitude than midnight substorms, and may even trigger substorm onset.</p>

scholarly journals Inverse cascade in the structure of substorm aurora and non-linear dynamics of field-aligned current filaments

2011 ◽  
Vol 29 (8) ◽  
pp. 1349-1354 ◽  
Author(s):  
B. V. Kozelov ◽  
I. V. Golovchanskaya ◽  
O. V. Mingalev
Keyword(s):  
Coarse Grained ◽  
Small Scale ◽  
Inverse Cascade ◽  
Non Linear ◽  
Substorm Activity ◽  
Field Aligned Current ◽  
Current Filaments ◽  
Scaling Features ◽  
Linear Interactions ◽  
Auroral Luminosity

Abstract. We investigate time evolution of scaling index αA that characterizes auroral luminosity fluctuations at the beginning of substorm expansion. With the use of UVI images from the Polar satellite, it is shown that αA typically varies from values less than unity to ~1.5, increasing with breakup progress. Similar scaling features were previously reported for fluctuations at smaller scales from all-sky TV observations. If this signature is interpreted in terms of non-linear interactions between scales, it means that the power of small-scale fluctuations is transferred with time to larger scales, a kind of the inverse cascade. Scaling behavior in the aurora during substorm activity is compared with that in the field-aligned currents simulated numerically in the model of non-linear interactions of Alfvénic coherent structures, according to the Chang et al. (2004) scenario. This scenario also suggests an inverse cascade, manifesting in clustering of small-scale field-aligned current filaments of the same polarity and formation of "coarse-grained" structures of field-aligned currents.

scholarly journals Statistical study on the occurrence of ASAID electric fields

2010 ◽  
Vol 28 (2) ◽  
pp. 439-448 ◽  
Author(s):  
S. Liléo ◽  
T. Karlsson ◽  
G. T. Marklund
Keyword(s):  
Electric Fields ◽  
Current System ◽  
Geomagnetic Latitude ◽  
Field Measurements ◽  
Auroral Oval ◽  
Outer Edge ◽  
Ionospheric Conductivity ◽  
Ion Drifts ◽  
Local Current ◽  
Substorm Activity

Abstract. The first statistical results on the occurrence of abnormal subauroral ion drifts (ASAID) are presented based on electric and magnetic field measurements from the low-altitude Astrid-2 satellite. ASAID are narrow regions of rapid eastward ion drifts observed in the subauroral ionosphere. They correspond to equatorward-directed electric fields with peak amplitudes seen to vary between 45 mV/m and 185 mV/m, and with latitudinal extensions between 0.2° and 1.2° Corrected Geomagnetic Latitude (CGLat), reaching in some cases up to 3.0° CGLat. Opposite to subauroral ion drifts (SAID) that are known to be substorm-related, ASAID are seen to occur predominantly during extended periods of low substorm activity. Our results show that ASAID are located in the vicinity of the equatorward edge of the auroral oval, mainly in the postmidnight sector between 23:00 and 03:00 magnetic local time. They are associated with a local current system with the same scale-size as the corresponding ASAID, composed by a region of downward field-aligned currents (FACs) flowing in the ASAID poleward side, and a region of upward flowing FACs in the equatorward side. The FACs have densities between 0.5 and 2.0 μA/m2. The data suggest that ASAID do not contribute significantly to the reduction of the ionospheric conductivity. ASAID are seen to have life times of at least 3.5 h. A discussion on possible mechanisms for the generation of ASAID is presented. We speculate that the proximity of the electron to the ion plasma sheet inner boundaries and of the plasmapause to the ring current outer edge, during extended quiet times, is an important key for the understanding of the generation of ASAID electric fields.

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