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Surfaces of satellites and spacecraft are exposed to high energy charged particles from the solar wind, especially during space weather events. This can lead to differential charging, which is a common reason for hardware degradation and sensor errors. Solutions like coatings are required to avoid excessive cost and weight. Mimicking the electron part of space-like environments in ultra-high vacuum (UHV) chambers can be achieved by using electrons emitted by a scanning electron microscope (SEM). As a performance test for the discharge capabilities we use the quality of electron microscopy images on otherwise insulating substrates such as glass, structured by nanosphere lithography and coated with an ionic liquid (IL). Additionally, the surface potential was measured by Kelvin Probe Force Spectroscopy. The IL film (BMP DCA) was applied ex-situ and a thickness of 12.8 (±0.8) nm was determined by reflectometry and confirmed by dynamic atomic force microscopy. Such a film of ionic liquid would lead to an additional mass of below 20 mg and negligible additional material costs. The light absorption and influence of ionic liquid coatings on the current output of an actual solar cell were investigated. The results indicate, that these coatings are promising candidates for surface charge mitigation with a high potential for application.

This paper addresses the long-term climatology (over two solar cycles) of total electron content (TEC) irregularities from a polar cap station (Thule) using the rate of change of the TEC index (ROTI). The climatology reveals variabilities over different time scales, i.e., solar cycle, seasonal, and diurnal variations. These variations in different time scales can be explained by different drivers/contributors. The solar activity (represented by the solar radiation index F10.7P) dominates the longest time scale variations. The seasonal variations are controlled by the interplay of the energy input into the polar cap ionosphere and the solar illumination that damps the amplitude of ionospheric irregularities. The diurnal variations (with respect to local time) are controlled by the relative location of the station with respect to the auroral oval. We further decompose the climatology of ionospheric irregularities using the empirical orthogonal function (EOF) method. The first four EOFs could reflect the majority (99.49%) of the total data variability. A climatological model of ionospheric irregularities is developed by fitting the EOF coefficients using three geophysical proxies (namely, F10.7P, Bt, and Dst). The data-model comparison shows satisfactory results with a high Pearson correlation coefficient and adequate errors. Additionally, we modeled the historical ROTI during the modern grand maximum dating back to 1965 and made the prediction during solar cycle 25. In such a way, we can directly compare the climatic variations of the ROTI activity across six solar cycles.

A signal, such as from a GNSS satellite or microwave sounding system, propagating in the randomly inhomogeneous ionosphere, experiences chaotic modulations of its amplitude and phase. This effect is known as scintillation. This article reviews basic theoretical concepts and simulation strategies for modeling the scintillation phenomenon. We focused our attention primarily on the methods connected with the random phase screen model. For a weak scattering regime on random ionospheric irregularities, a single-phase screen model enables us to obtain the analytic expression for phase and intensity scintillation indices, as well as the statistical quantities characterizing the strength of scintillation-related fades and distortions. In the case of multiple scattering, the simulation with multiple phase screens becomes a handy tool for obtaining these indices. For both scattering regimes, the statistical properties of the ionospheric random medium play an important role in scintillation modeling and are discussed with an emphasis on related geometric aspects. As an illustration, the phase screen simulation approaches used in the global climatological scintillation model GISM are briefly discussed.

Ionospheric irregularities impair Global Navigation Satellite System (GNSS) signals and, in turn, affect the performance of GNSS positioning. Such effects are especially evident at low and high latitudes, which are currently gaining the attention of research and industry sectors. This study evaluates the impact of ionospheric irregularities on GNSS positioning in Greenland. We assess the performance of positioning methods that meet the demands of a wide range of users. In particular, we address the needs of the users of mass-market single-frequency receivers and those who require a solution of high precision provided by geodetic dual-frequency receivers. We take advantage of the datasets collected during three ionospheric storms: the St. Patrick’s Day storm of March 17, 2015, the storm on June 22, 2015, and another on August 25–26, 2018. We discover a significant impact of the ionospheric disturbances on the ambiguity resolution performance and the accuracy of the float solution in Real Time Kinematics (RTK) positioning. Next, assessing the single-frequency ionosphere-free Precise Point Positioning (PPP), we demonstrate that the model is generally unaffected by ionospheric disturbances. Hence, the model is predestined for the application by the users of single-frequency receivers in the areas of frequent ionospheric disturbances. Finally, based on the observation analyses, we reveal that phase signals on the L2 frequency band are more prone to cycle slips induced by ionospheric irregularities than those transmitted on the L1. Such signal properties explain a noticeable decline in the dual-frequency RTK performance during the ionospherically disturbed period and merely no effect for the single-frequency ionosphere-free PPP model.

To understand the global response of thermospheric‐ionospheric (TI) parameters to variations in solar irradiance measurements from the Global‐Scale Observations of the Limb and Disk (GOLD) ultraviolet imaging spectrograph, solar radio flux F10.7, predictions from the Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model, and International Global Navigation Satellite System Service total electron content maps (TEC) have been used. Various parameters such as GOLD O/N2, O2, and the nighttime peak electron density (Nmax) have been compared with the CTIPe model simulations. The GOLD observed Nmax shows a number of significant features including a winter anomaly and an equatorial ionization anomaly. The comparison with solar proxies showed that the GOLD QEUV correlates very well with the EUV observations compared to the F10.7 index. The study also examined the relationship between the solar proxies and Nmax on different time scales and found that Nmax responded significantly to QEUV at both medium‐ and long‐term timescales. Furthermore, a low correlation between Nmax in the equatorial region and solar proxies was found. A delayed ionospheric TEC response against solar flux variations within the 27‐day solar rotation was investigated. This ionospheric delay of TEC with respect to solar flux was observed to be less than 1 day, which was reproduced in model simulations. The current study has shown that the GOLD observations can be used to investigate the delayed ionospheric response and to gain a better understanding of the influence of solar activity on the TI system. Key Points: Ionospheric‐thermospheric parameters observed by Global‐Scale Observations of the Limb and Disk (GOLD) ultraviolet imaging spectrograph are compared with Coupled Thermosphere Ionosphere Plasmasphere electrodynamics model simulationsThe delayed ionospheric response against the solar flux is less than 1 day at the time scale of the 27 days solar rotation periodThe integrated 1–45 nm solar energy flux values observed by GOLD correlate well with the F10.7 and EUV [ABSTRACT FROM AUTHOR]

Space weather can strongly affect trans-ionospheric radio signals depending on the used frequency. In order to assess the strength of a space weather event from its origin at the sun towards its impact on the ionosphere a number of physical quantities need to be derived from scientific measurements. These are for example the Wolf number sunspot index, the solar flux density F10.7, measurements of the interplanetary magnetic field, the proton density, the solar wind speed, the dynamical pressure, the geomagnetic indices Auroral Electrojet, Kp, Ap and Dst as well as the Total Electron Content (TEC), the Rate of TEC, the scintillation indices S4 and σ(ϕ) and the Along-Arc TEC Rate index index. All these quantities provide in combination with an additional classification an orientation in a physical complex environment. Hence, they are used for brief communication of a simplified but appropriate space situation awareness. However, space weather driven ionospheric phenomena can affect many customers in the communication and navigation domain, which are still served inadequately by the existing indices. We present a new robust index, that is able to properly characterize temporal and spatial ionospheric variations of small to medium scales. The proposed ionospheric disturbance index can overcome several drawbacks of other ionospheric measures and might be suitable as potential driver for an ionospheric space weather scale.

Users of the Global Positioning System (GPS) utilize the Ionospheric Correction Algorithm (ICA) also known as Klobuchar model for correcting ionospheric signal delay or range error. Recently, we developed an ionosphere correction algorithm called NTCM-Klobpar model for single frequency GNSS applications. The model is driven by a parameter computed from GPS Klobuchar model and consecutively can be used instead of the GPS Klobuchar model for ionospheric corrections. In the presented work we compare the positioning solutions obtained using NTCM-Klobpar with those using the Klobuchar model. Our investigation using worldwide ground GPS data from a quiet and a perturbed ionospheric and geomagnetic activity period of 17 days each shows that the 24-hour prediction performance of the NTCM-Klobpar is better than the GPS Klobuchar model in global average. The root mean squared deviation of the 3D position errors are found to be about 0.24 and 0.45 m less for the NTCM-Klobpar compared to the GPS Klobuchar model during quiet and perturbed condition, respectively. The presented algorithm has the potential to continuously improve the accuracy of GPS single frequency mass market devices with only little software modification.

The solar eclipse on March 20, 2015 was a fascinating event for people in Northern Europe. From a scientific point of view, the solar eclipse can be considered as an in situ experiment on the Earth’s upper atmosphere with a well-defined switching off and on of solar irradiation. Due to the strong changes in solar radiation during the eclipse, dynamic processes were initiated in the atmosphere and ionosphere causing a measurable impact, for example, on temperature and ionization. We analyzed the behavior of total ionospheric ionization over Europe by reconstructing total electron content (TEC) maps and differential TEC maps. Investigating the large depletion zone around the shadow spot, we found a TEC reduction of up to 6 TEC units, i.e., the total plasma depletion reached up to about 50%. However, the March 20, 2015 eclipse occurred during the recovery phase of a strong geomagnetic storm and the ionosphere was still perturbed and depleted. Therefore, the unusual high depletion is due to the negative bias of up to 20% already observed over Northern Europe before the eclipse occurred. After removing the negative storm effect, the eclipse-induced depletion amounts to about 30%, which is in agreement with previous observations. During the solar eclipse, ionospheric plasma redistribution processes significantly affected the shape of the electron density profile, which is seen in the equivalent slab thickness derived by combining vertical incidence sounding (VS) and TEC measurements. We found enhanced slab thickness values revealing, on the one hand, an increased width of the ionosphere around the maximum phase and, on the other, evidence for delayed depletion of the topside ionosphere. Additionally, we investigated very low frequency (VLF) signal strength measurements and found immediate amplitude changes due to ionization loss at the lower ionosphere during the eclipse time. We found that the magnitude of TEC depletion is linearly dependent on the Sun’s obscuration function. By modelling TEC depletion and knowing the Sun’s obscuration function in advance, Global Navigation Satellite System (GNSS) operators may improve the broadcast ionospheric correction during a solar eclipse day.