Dusty space plasma diagnosis using temporal behavior of polar mesospheric summer echoes during active modification

The objective of this paper is to study the effect of different plasma and dust parameters on Polar Mesospheric Summer Echoes (PMSE) temporal behavior after turn-on and turn-off of radio wave heating and to use these responses to diagnose the properties of the dust layer. The threshold radar frequency and dust parameters for the enhancement or suppression of radar echoes after radio wave heating turn-on are investigated for measured mesospheric plasma parameters. The effect of parameters such as the electron temperature enhancement during heating, dust density, dust charge polarity, ion-neutral collision frequency, electron density and dust radius on the temporal evolution of electron irregularities associated with PMSE are investigated. The possible diagnostic information for various charged dust and background plasma quantities using the temporal behavior of backscattered radar power in active experiments is discussed. The computational results are used to make predictions for PMSE active modification experiments at 7.9, 56, 139, 224 and 930MHz corresponding to existing radar facilities. Data from a 2009 VHF (224 MHz) experiment at EISCAT is compared with the computational model to obtain dust parameters in the PMSE

The equatorial electrojet during geomagnetic storms and substorms

The climatology of the equatorial electrojet during periods of enhanced geomagnetic activity is examined using long-term records of ground-based magnetometers in the Indian and Peruvian regions. Equatorial electrojet perturbations due to geomagnetic storms and substorms are evaluated using the disturbance storm time (Dst) index and auroral electrojet (AE) index, respectively. The response of the equatorial electrojet to rapid changes in the AE index indicates effects of both prompt penetration electric field and disturbance dynamo electric field, consistent with previous studies based on F region equatorial vertical plasma drift measurements at Jicamarca. The average response of the equatorial electrojet to geomagnetic storms (Dst<−50 nT) reveals persistent disturbances during the recovery phase, which can last for approximately 24 h after the Dst index reaches its minimum value. This “after-storm” effect is found to depend on the magnitude of the storm, solar EUV activity, season, and longitude

Why Are Electronic Invoice Processes Risky? - Empirical Analysis and Discussion of Risk Factors

Electronic invoice processes are characterized by various software solutions, legal uncertainty, heter-ogeneous demands, lack of know how, and information system infrastructure incompatibilities. Due to this complexity and the uncertainty that companies face, a holistic map of risk factors of e-invoice processes is required. Companies must be conscious not only about potential opportunities but also about potential risks before they change their business processes and their information systems’ archi-tecture. Potential risk factors are identified theoretically and empirically evaluated with a quantitative expert survey that investigates risk probabilities and potential losses associated with these factors. The empirical analysis reveals that the investigated factors are valid and reliable. After conducting an ex-plorative factor analysis, 37 statistically significant risk factors are grouped into ten risk dimensions: process organization, standard, environment, project management, strategy, acceptance, system, pro-cess execution, security, and change management

Average field-aligned ion velocity over the EISCAT radars

Long-term measurements by the European Incoherent Scatter (EISCAT) radars at Tromsø (69.6° N, 19.2° E) and Svalbard (78.2° N, 16.0° E) are used to determine the climatology of the field-aligned ion velocity in the F-region ionosphere (175–475 km) at high latitudes. The average ion velocity is calculated at various altitudes and times of day. The magnitude of the average field-aligned ion velocity is on the order of 10 m/s, similar to previous results at middle and low latitudes. The results obtained for the two radars are in good agreement. During daytime the direction of the average field-aligned ion velocity changes from downward to upward around 350 km, while during nighttime it is upward at all heights. The reversal height of the daytime field-aligned ion velocity depends on solar activity. It is elevated by more than 100 km during high solar flux periods compared to low solar flux periods. The Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) reproduces the main features of the field-aligned ion velocity climatology. The simulation results suggest that the plasma pressure gradient force and gravity force play a dominant role for the daytime field-aligned ion motion. The height pattern of the field-aligned ion velocity tends to be preserved in different solar activity conditions at constant pressure surfaces, but not at constant altitudes, which explains the observed dependence on solar activity. During nighttime, the effect of the neutral wind dominates the field-aligned ion velocity

Average field-aligned ion velocity over the EISCAT radars

Long-term measurements by the European Incoherent Scatter (EISCAT) radars at Tromsø (69.6° N, 19.2° E) and Svalbard (78.2° N, 16.0° E) are used to determine the climatology of the field-aligned ion velocity in the F-region ionosphere (175–475 km) at high latitudes. The average ion velocity is calculated at various altitudes and times of day. The magnitude of the average field-aligned ion velocity is on the order of 10 m/s, similar to previous results at middle and low latitudes. The results obtained for the two radars are in good agreement. During daytime the direction of the average field-aligned ion velocity changes from downward to upward around 350 km, while during nighttime it is upward at all heights. The reversal height of the daytime field-aligned ion velocity depends on solar activity. It is elevated by more than 100 km during high solar flux periods compared to low solar flux periods. The Thermosphere Ionosphere Electrodynamics General Circulation Model (TIE-GCM) reproduces the main features of the field-aligned ion velocity climatology. The simulation results suggest that the plasma pressure gradient force and gravity force play a dominant role for the daytime field-aligned ion motion. The height pattern of the field-aligned ion velocity tends to be preserved in different solar activity conditions at constant pressure surfaces, but not at constant altitudes, which explains the observed dependence on solar activity. During nighttime, the effect of the neutral wind dominates the field-aligned ion velocity

Maximum sprite streamer luminosity near the stratopause

Sprites are composed of numerous streamers which exhibit transient luminosities in the upper middle atmosphere above thunderclouds after initiation by an intense positive lightning discharge, often followed by lightning continuing current. Here we report the discovery of a sprite which exhibits its main luminosity near the stratopause. This novel phenomenon is attributed to a sudden surge of intracloud lightning leader activity, based on a rigorous analysis of our observed electromagnetic waveforms

A PRACTICAL TEST OF A PROCESS MODEL FOR CUSTOMER RELATIONSHIP MANAGEMENT SYSTEM SELECTION WITH AN AUTOMOTIVE SUPPLIER

Selecting suitable customer relationship management systems (CRM) is a decision problem with economic, behavioural, technical and functional implications. It is important to methodically identify an appropriate solution with regard to the various aspects of the decision. In this paper, a practical test of the previously developed customer relationship management system selection (CRMSS) process model is conducted in a case study with an automotive safety goods supplier. The process model used was constructed based on a literature review and further refined by expert interviews and two international online surveys. To test the models applicability and align phases, tasks, roles and deliverables with practical experiences, qualitative interviews were conducted with the different stakeholders in the evaluation project. The CRMSS process model was then further refined according to the conclusions drawn from the presented case study. The first application of the process model suggests that it is considered as relevant for practice and can be understood and applied successfully for a CRM selection and evaluation. In the context of the case study the model was customised to meet the needs of the project

A model of high-latitude thermospheric density

We present an empirical model of the high-latitude air density at 450 km, derived from accelerometer measurements by the CHAllenging Minisatellite Payload and Gravity Recovery and Climate Experiment satellites during 2002–2006, which we call HANDY (High-Latitude Atmospheric Neutral DensitY). HANDY consists of a quiet model and disturbance model. The quiet model represents the background thermospheric density for “zero geomagnetic activity” conditions. The disturbance model represents the response of the thermospheric density to solar wind forcing at high latitudes. The solar wind inputs used are the following: (1) solar wind electric field ESW, (2) interplanetary magnetic field (IMF) clock angle CSW, and (3) solar wind dynamic pressure PSW. Both quiet and disturbance models are constructed on the basis of spherical harmonic function fitting to the data. Magnetic coordinates are used for the disturbance model, while geographical coordinates are used for the quiet model. HANDY reproduces main features of the solar wind influence on the high-latitude thermospheric density, such as the IMF By effect that produces a hemispheric asymmetry in the density distribution

Dynamic Properties of a Sporadic Sodium Layer Revealed by Observations Over Zhongshan, Antarctica: A Case Study

A sodium Doppler lidar system with three-directional measurements of sodium density, atmospheric wind field, and temperature was established at Zhongshan (69.4°S, 76.4°E), Antarctica. On November 14, 2019, a sporadic sodium layer (SSL) was observed at an altitude range of 93–103 km. The temporal/spatial sodium density variations of this SSL are associated with a strong sporadic E (Es) layer at nearly the same height, which is modulated by the convective electric field. By considering the structures and the time lags of the SSL's growth at three positions, the SSL appears to have a horizontal advection in an approximately westward direction with a velocity of the order of 80 m/s. This is consistent with the zonal wind velocity derived from the lidar system itself. The temporal/spatial sodium density variations strongly indicate that the formation and perturbation of SSLs are related to the evolution of ES layers due to varied electric fields and atmospheric gravity waves, while it is advected by the horizontal wind. © 2021. American Geophysical Union. All Rights Reserved

Ionospheric electron number densities from CUTLASS dual-frequency velocity measurements using artificial backscatter over EISCAT

Using quasi-simultaneous line-of-sight velocity measurements at multiple frequencies from the Hankasalmi Cooperative UK Twin Auroral Sounding System (CUTLASS) on the Super Dual Auroral Radar Network (SuperDARN), we calculate electron number densities using a derivation outlined in Gillies et al. (2010, 2012). Backscatter targets were generated using the European Incoherent Scatter (EISCAT) ionospheric modification facility at Tromsø, Norway. We use two methods on two case studies. The first approach is to use the dual-frequency capability on CUTLASS and compare line-of-sight velocities between frequencies with a MHz or greater difference. The other method used the kHz frequency shifts automatically made by the SuperDARN radar during routine operations. Using ray tracing to obtain the approximate altitude of the backscatter, we demonstrate that for both methods, SuperDARN significantly overestimates Ne compared to those obtained from the EISCAT incoherent scatter radar over the same time period. The discrepancy between the Ne measurements of both radars may be largely due to SuperDARN sensitivity to backscatter produced by localized density irregularities which obscure the background levels