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Abstract We notice that the important early decreasing part of the main phase (MP) from the positive main phase onset (MPO) to 0-level of Dst and SymH indices is missed in the treatment of the main phase (MP) of geomagnetic storms. We correct this inconsistency in 848 storms having positive MPO (out of 1164 storms) in SymH during 1981–2019 by raising the 0-level of SymH to the MPO-level. The correction considers the full range of the main phase, increases the corrected (revised) storm intensity (SymHMin*) and impulsive strength (IpsSymH*) by up to − 149 nT and − 134 nT, respectively, and seems important for all aspects of global space weather. For example, the corrected SymHMin* changes the conventional storm identification and classification and corrected IpsSymH* clearly identifies all 3 severe space weather (SvSW) events from over 1100 normal space weather (NSW) events with a separation of 52 nT; it also identifies all 8 minor-system-damage space weather (MSW) events from the NSW events.

We present a case study of unusual spread-F structures observed by ionosondes at two equatorial and low-latitude Brazilian stations – São Luís (SL: 44.2∘ W, 2.33∘ S; dip angle: −6.9∘) and Fortaleza (FZ: 38.45∘ W, 3.9∘ S; dip angle: −16∘). The irregularity structures observed from midnight to postmidnight hours of moderate solar activity (F10.7 < 97 sfu, where 1 sfu = 10−22 W m−2 s−1) have characteristics different from typical post-sunset equatorial spread F. The spread-F traces first appeared at or above the F-layer peak and gradually became well-formed mixed spread F. They also appeared as plasma depletions in the 630.0 nm airglow emissions made by a wide-angle imager located at the nearby low-latitude station Cajazeiras (CZ: 38.56∘ W, 6.87∘ S; dip angle: −21.4∘). The irregularities appeared first over FZ and later over SL, giving evidence of an unusual westward propagation or a horizontal plasma advection. The drift-mode operation available in one of the ionosondes (a digital portable sounder, DPS-4) has enabled us to analyze the horizontal drift velocities and directions of the irregularity movement. We also analyzed the neutral wind velocity measured by a Fabry–Pérot interferometer (FPI) installed at CZ and discuss its possible role in the development of the irregularities.

Abstract This short paper presents the statistics of spread-F occurrence at four low-mid latitude locations (17.0° N, 21.2° N, 26.5° N and 36.5° N mag. lat.) in Japan longitude sector (~ 135° E) in March to April 2002, 2003 and 2006 (high, medium and low solar activity). The location of a spread-F minimum predicted by theoretical models is identified for the first time. The spread-F minimum occurs at the poleward side of the equatorial ionisation anomaly crest and shifts equatorward from ~ 25° N mag. lat. at high solar activity to below 17° N at low solar activity. The corresponding spread-F maximum occurring on the poleward side of the minimum also shifts equatorward from ~ 35° N (or beyond) at medium solar activity to 20°–25° N at low solar activity. The spread-F occurrence increases with decreasing solar activity at all locations especially at higher latitudes (> ~ 25° N) where there is almost no occurrence at high solar activity.

Abstract A computer program is developed to automatically identify the geomagnetic storms in Dst index by applying four selection criteria that minimize non-storm-like fluctuations. The program is used to identify the storms in Kyoto Dst and USGS Dst in 50 years (1958–2007). The identified storms (DstMin ≤ −50 nT) are used to investigate their seasonal variations. It is found that the overall seasonal variations of the storm parameters such as occurrence, average intensity (average DstMin) and average strength (average ⟨DstMP⟩) in both versions of Dst exhibit clear semiannual variations with equinoctial maxima and solstice minima; and the maxima and minima in intensity and strength (~±17% each) are less than those in occurrence (~±28%). Wavelet spectra of the storms reveal the existence of distinct semiannual component in four solar cycles (SCs 20–23) and weak longer and shorter-period components in some SCs. The semiannual variation observed also in the mean energy input during the main phase (MP) of the storms estimated from Dst is interpreted in terms of the (1) equinoctial mechanism based on the varying angle between the Earth–Sun line and Earth’s dipole axis and (2) Russell–Mcpherron effect based on the varying angle between the GSM Z-axis and GSE Y-axis; and the yearly range of the dipole tilt angle µ (23.2°) involved in the equinoctial mechanism is found larger than the title angle θ (16.3°) involved in the RM effect. Graphical Abstract .

In this paper, we analyze daytime observations of the critical frequencies of the F2 (foF2) and F3 (foF3) layers based on ionosonde observations made from Indian low latitudes close to the magnetic equator and study their local time, seasonal, planetary-scale variations (including the solar rotation effect), and solar activity dependence. Given the occurrence of the F3 layer, which has remarkable local time, seasonal and solar activity dependences, variations in foF2 have been evaluated. Local time variations in foF2 and foF3 show noon "bite-out" in all seasons and in all solar activity conditions, which are attributed to vertically upward plasma transport by the zonal electric field and meridional neutral wind. Comparison of observed foF2 with those of the IRI-2012 model clearly shows that the model values are always higher than observed values and the largest difference is observed during noontime owing to the noon bite-out phenomenon. Peak frequency of the F layer (foF2 / foF3), however, is found to have better agreement with IRI-2012 model. Seasonal variations of foF2 and foF3 show stronger asymmetry at the solstices than at the equinoxes. The strong asymmetry at the solstice is attributed to the asymmetry in the meridional neutral wind with a secondary contribution from E × B drifts, and the relatively weak asymmetry observed at the equinox is attributed to the asymmetry in E × B drifts. Variations in foF2 and foF3 with solar flux clearly show the saturation effect when F10.7 exceeds ~ 120 sfu, which is different from that of the mid-latitudes. Irrespective of solar flux, both foF2 and foF3 in summer, however, are found to be remarkably lower than those observed in other seasons. Variations in foF2 show dominant periods of ~ 27, ~ 16 and ~ 6 days. Intriguingly, amplitudes of ~ 27-day variations in foF2 are found to be maximum in low solar activity (LSA), moderate in medium solar activity (MSA) and minimum in high solar activity (HSA), while the amplitudes of ~ 27-day variations in F10.7 are minimum in LSA, moderate in MSA and maximum in HSA. These results are presented and discussed in light of current observational and model-based knowledge on the variations of low-latitude foF2 and foF3.

Abstract This thematic series contains 4 papers mostly presented at the 2016 AOGS meeting in Beijing. The four papers investigate four key regions in the magnetosphere–ionosphere coupling process: mid-tail magnetosphere, near-Earth magnetosphere, inner magnetosphere, and the polar ground region. Guo et al. (Geosci Lett 4:18, 2017) study the current system in reconnection region using 2.5D particle-in-cell simulations. Yao et al. (Geosci Lett 4:8, 2017) use conjugate measurements from ground auroral imagers and in situ THEMIS spacecraft to reveal the mechanism for the wave-like auroral structures prior to substorm onset. Zhang et al. (Geosci Lett 4:20, 2017) investigate the profiles of resonance zone and resonant frequency in the Landau resonance between radiation belt electrons and magnetosonic waves and between protons and cyclotron waves. Rae et al. (Geosci Lett 4:23, 2017) determine the relative timing between sudden increases in amplitude, or onsets, of different ultra-low-frequency wave bands during substorms.

In this paper, we present model simulations of the Mid-latitude Summer Nighttime Anomaly (MSNA) in the Northern Hemisphere, which is characterized by noon-time dip and evening maximum in the diurnal variation of the ionospheric density. The simulations are carried out using SUPIM (Sheffield University Plasmasphere Ionosphere Model) for solar minimum at 135° E longitude where MSNA is most pronounced in the Northern Hemisphere. The simulations are used to understand the relative importance of electric fields, and zonal and meridional winds in the formation of MSNA. The wind velocities measured by the Middle and Upper atmosphere radar (MU radar) and those obtained from the horizontal wind model (HWM93) are used. The results show that the formation of MSNA is closely related to the diurnal variation of the neutral winds with little contribution from the changes in the electric fields. The observed features of MSNA are better reproduced when MU radar winds are used as model input rather than HWM winds.

On 18 April 2002 the Cluster spacecraft crossed through the northern outer magnetospheric cusp region during 16:25-17:55 UT when the solar wind dynamic pressure was rather low (Bz was more negative than IMF By. The Cluster data from the FGM, CIS, PEACE, EFW, WHISPER and STAFF instruments reveal that the cusp is structured with three anti-sunward ion flow events of durations ≈1.5, 17.5 and 19.0 min, with bulk plasma flow roughly parallel to the magnetopause toward north. The ion and electron densities within the events are much greater than those outside. The zonal electric field in the ion flow events turns eastward as expected from V×B effect. The sharp inward boundaries of the ion flow events cross the four spacecraft in one time sequence, and the outward boundaries of the events cross the spacecraft in the reverse time sequence. The observations studied using magnetosphere and magnetopause models suggest that the structured cusp is a temporal feature that arises due to three inward and outward movements of the magnetopause by about 1.5RE so that Cluster, while crossing through the cusp, happened to be in the magnetosheath (ion flow event) and cusp alternately. The magnetopause moved due to the changes in the solar wind dynamic pressure by up to 100%.

Recent studies using model calculation and ionospheric observations have revealed the existence of an additional layer in the topside equatorial ionosphere, the F3 layer. In this work we analyze ionosonde data from two low/equatorial latitude stations in Brazil, during the year 1995, a low solar activity period, in order to study the F3 layer at those locations. At the magnetic station São Luís (2.3° S, 44° W, dip angle –0.5°) the occurrence of the F3 layer is much less evident than at the low latitude station Fortaleza (4° S, 38° W, dip angle –9°). The ionograms recorded at Fortaleza in 1995 show the existence of the layer on 50% of the days, with the occurrence being more frequent (75%) and distinct in summer. The layer appears on 66% of the days in winter and 28% in equinoxes. The layer starts to appear around 0930 LT and lasts from a few minutes to several hours. Its mean height varies from 570 km in summer to 440 km in winter, although on a day to day basis it can vary from as low as 375 km to 775 km. The ionospheric model SUPIM (Sheffield University Plasmasphere-Ionosphere Model) explains well the occurrence of the layer in summer, but not in winter, unless some key input parameters, such as electric field and winds are modified. This suggests that the existing models for electric fields and winds are not representative for the Brazilian low latitude region during winter.

Estudios recientes usando modelos y observaciones ionosféricas han revelado la existencia de una capa adicional en el tope de la ionosfera ecuatorial, la capa F . En el presente trabajo analizamos los datos de ionosondas de dos estaciones: una de baja latitud y otra ecuatorial en Brasil, durante el año 1995, un periodo de baja actividad solar, con el objeto de estudiar la capa F en estas latitudes. Se observa que en la estación magnética de São Luís (2.3° S, 44° W, dip angle –0.5°), la ocurrencia de la capa F3 es mucho menor que en la estación de baja latitud de Fortaleza (4° S, 38° W, dip angle –9°). Los ionogramas de Fortaleza en 1995 muestran la existencia de la capa en el 50% de los días. Dicha ocurrencia es frecuente y distintiva (75%) en verano (mes de diciembre). Los ionogramas también muestran la existencia de la capa en el 66% de los días en invierno (mes de junio) y en el 28% en los equinoccios. La capa empieza a aparecer alrededor de las 0930 hora local y dura desde unos minutos hasta varias horas. Esto significa que la altura de la capa varía desde 570 km en verano hasta 440 km en invierno, aunque día a día la altura puede variar desde 375 km hasta 775 km. El modelo ionosférico SUPIM (Sheffield University Plasmasphere-Ionosphere Model) se usó para simular las características de la capa sobre Fortaleza. El modelo explica bien la ocurrencia de la capa en verano, pero no en invierno, a menos que se modifiquen algunos parámetros clave tales como el campo eléctrico y los vientos. Esto indica que los modelos existentes para el campo eléctrico y los vientos no son representativos de las latitudes bajas brasileñas en el invierno. doi: https://doi.org/10.22201/igeof.00167169p.2000.39.1.297

Calculations using the Sheffield University plasmasphere ionosphere model have shown that under certain conditions an additional layer can form in the low latitude topside ionosphere. This layer (the F3 layer) has subsequently been observed in ionograms recorded at Fortaleza in Brazil. It has not been observed in ionograms recorded at the neighbouring station São Luis. Model calculations have shown that the F3 layer is most likely to form in summer at Fortaleza due to a combination of the neutral wind and the E×B drift acting to raise the plasma. At the location of São Luis, almost on the geomagnetic equator, the neutral wind has a smaller vertical component so the F3 layer does not form.

Main currently used resist mask formation models and problems solved have been overviewed. Stages of "full physical simulation" have been briefly analyzed based on physicochemical principles for conventional diazonapthoquinone (DNQ) photoresists and chemically enhanced ones. We have considered the concepts of the main currently used compact models predicting resist mask contours for full-scale product topologies, i.e., VT5 (Variable Threshold 5) and CM1 (Compact Model 1). Computation examples have been provided for full and compact resist mask formation models. Full resist mask formation simulation has allowed us to optimize the lithographic stack for a new process. Optimal thickness ratios have been found for the binary anti-reflecting layers used in water immersion lithography. VT5 compact model calibration has allowed us to solve the problem of optimal calibration structure sampling for maximal coverage of optical image parameters space while employing the minimal number of structures. This problem has been solved using cluster analysis. Clustering has been implemented using the k-means method. The optimum sampling is 300 to 350 structures, the rms error being 1.4 nm which is slightly greater than the process noise for 100 nm structures. The use of SEM contours for VT5 model calibration allows us to reduce the rms error to 1.18 nm for 40 structures.

Background: Forensic science, also known as Criminalistics is a field of science that uses science for investigation and its application in civil and criminal proceedings. One of the main challenges is to identify the dead during criminal and mass disaster investigations. Aim: The study aims to evaluate the morphometry of the orbital aperture and to verify its relationship with biological sex discrimination using three-dimensional Computed Tomography (3D CT). Study Design: This retrospective study involves 100 3D CT images of 50 males and 50 females (age 18-60 years). Materials and Methods: The exclusion criteria were congenital anomalies affecting the head and neck region, orbital fracture, systemic diseases affecting bone and head and neck tumor. Eight orbital parameters such as Orbital width, orbital height, orbital roof length, orbital floor-length, lateral orbital wall length, medial orbital wall length, intraorbital distance, and extra orbital distance were measured for all the 3D CT images using RadiAnt DICOM Viewer (64 bit). Statistical Analysis: Descriptive statistics including mean, standard deviation, and percentage distribution were calculated. Mann Whitney U-test assessed the comparison between groups. The linear regression equation and Wilk's lambda were also calculated for every parameter. Results: All the orbital measurements except for intraorbital distance were statistically significant between male and female subjects. Totally, 92.0% of the individuals were correctly classified. Conclusions: Orbital measurements were significantly larger in males than in females. Orbits exhibit the least dimensional change throughout one's life. Hence, it could be used as an adjunct in biological sex determination.

As a result of the research, 109 individuals of two amphibian species: the common frog (Rana temporaria) and the common toad (Bufo bufo) were selected. These two species are the most numerous among other species of amphibians within the studied territory, therefore, they can be considered typical species in the anthropogenically transformed habitats of the Ukrainian Roztochchia. During the analysis of the collected material, Ivlev’s selectivity index was used to determine the selective attitude of the studied amphibian species to the number of consumed objects. Comparing data obtained from Barber’s traps and material extracted from the stomachs of amphibians, it was concluded that depending on the habitat type, both the common frog (Rana temporaria) and the common toad (Bufo bufo) show a certain feeding selectivity. The common toad consumes mostly the representatives of Annelida (15%), Arachnida (15%) and Coleoptera (18%), what makes up 48% of all consumed objects in total. The common frog, under the conditions of anthropogenically transformed environment, prefers Mollusca (15%), Myriapoda (20%) and Hemiptera (20%) mostly, what is 55% in total. In half of the stomachs we examined for, both amphibian species, plant residues were found, specifically parts of leaves and branches. Additionally, in individuals of the Bufo bufo species, stones were discovered in the stomach. Most likely, these items ended up there accidentally during the capture of primary food objects. Species of tailless amphibians are highly vulnerable to the negative impact of various anthropogenic factors. Deforestation, water bodies drainage, and global or local environmental pollution can significantly affect diverse ecosystems. This, in turn, may lead to the disappearance of segments of the dietary spectrum for amphibians. Monitoring the trophic interactions of this animal class is crucial, given the importance of amphibians as vital links in food chains. This factor underscores the need for periodic trophic monitoring, as amphibians play a pivotal role in sustaining ecological balance within their vulnerable populations.