Space Weather Applications Research Articles

Topside Ionosphere of NeQuick2 and IRI‐2016 Validated by Using Onboard GPS Observations From Multiple LEO Satellites

AbstractAn accurate description of the topside ionosphere is of great importance for space weather applications. Currently, there are two commonly used empirical ionosphere models, that is, NeQuick2 and IRI‐2016, that can be used to describe the topside ionosphere. In this study, topside total electron content (TEC) values derived from low Earth orbit (LEO) satellites are selected to validate the topside ionosphere predictions of the NeQuick2 and IRI‐2016 models from 2008 to 2018. The results show that these two models both underestimate the topside ionosphere. Compared with the global topside ionosphere model estimated by LEO‐based global positioning system (GPS) observations with orbital altitudes of 500 and 800 km, NeQuick2 and IRI‐2016 have similar performances over different latitudes and longitudes. The daily mean root mean square (RMS) values are approximately 4.10 and 2.10 TEC units (TECU) for the region above 500 and 800 km, respectively. The results assessed by the GPS‐TEC technique indicate that the performance of the NeQuick2 model is slightly better than that of the IRI‐2016 model. The daily mean bias mainly ranges from −1.5 to 1.5 and −3.0 to −1.0 TECU for the regions above 500 and 800 km, respectively. The RMS values for the corresponding parts are 3.50 and 2.74 TECU. Finally, the validation results of the dSTEC method show that the mean bias is −0.43 and −0.20 TECU above 500 and 800 km, respectively. The mean RMS values are 2.04 and 0.72 TECU for the corresponding regions.

Determination of NavIC differential code biases using GPS and NavIC observations

Delay bias between the pseudo range code is called Differential Code Bias (DCB), this is one of the main error sources to estimate the precise Total Electron Content (TEC) in ionosphere. Differential delay biases between the dual frequency band signals in both satellite and receiver are called satellite differential code biases (SDCBs) and receiver differential code biases (RDCBs). The combined satellite and receiver DCBs lead to measure error TEC. SDCBs and RDCBs should be removed from the Global Navigation Satellite System (GNSS) measurements accurately. The DCB estimations of GNSS signals are important for improving GNSS user positioning accuracy in ionospheric and space weather applications. The Navigation with Indian Constellation (NavIC) system has been developed by India to cater to positioning, navigation, timing, and ionosphere and troposphere remote sensing applications. The proposed DCB estimation algorithm is necessary to calibrate the NavIC TEC measurements for both NavIC satellites and receivers. In this work, a Global Positioning System (GPS)-aided NavIC DCB estimation algorithm has been implemented with the help of single station GPS TEC measurements. TEC data were recorded at the same location by the NavIC as well as the GPS receiver (Koneru Lakshamaiah Education Foundation, Guntur, India, 16.47°N, 80.61°E) for the month of September 2016. The SDCB and RDCB estimations for NavIC satellites and receivers located at Guntur, India. The maximum SDCB value of 9.2 TECU was observed for NavIC satellite pseudo range number (PRN) 3. Standard deviations of NavIC satellites were in the range of 0.53–1.11 TECU. The NavIC RDCB was estimated to be 16 TECU. The DCB results were validated with the Fitted Receiver Bias (FRB) method. The implemented DCB estimation algorithm would be useful for improving positional accuracy of NavIC users.

Current status and possible extension of the global neutron monitor network

The global neutron monitor network has been successfully used over several decades to study cosmic ray variations and fluxes of energetic solar particles. Nowadays, it is used also for space weather purposes, e.g. alerts and assessment of the exposure to radiation. Here, we present the current status of the global neutron monitor network. We discuss the ability of the global neutron monitor network to study solar energetic particles, specifically during large ground level enhancements. We demonstrate as an example, the derived solar proton characteristics during ground level enhancements GLE #5 and the resulting effective dose over the globe at a typical commercial jet flight altitude of 40 kft (≈12,200 m) above sea level. We present a plan for improvement of space weather services and applications of the global neutron monitor network, specifically for studies related to solar energetic particles, namely an extension of the existing network with several new monitors. We discuss the ability of the optimized global neutron monitor network to study various populations of solar energetic particles and to provide reliable space weather services.

Data reduction pipeline for MOF-based synoptic telescopes

There are strong scientific cases and practical reasons for building ground-based solar synoptic telescopes. Some issues, like the study of solar dynamics and the forecasting of solar flares, benefit from the 3D reconstruction of the Sun’s atmosphere and magnetic field. Others, like the monitoring and prediction of space weather, require full disk observations, at the proper sampling rate, combining H-alpha images and Doppler velocity and magnetic field. The synoptic telescopes based on Magneto Optical Filters (MOF) using different lines are capable of measuring the line-of-sight Doppler velocity and magnetic field over the full solar disk at different ranges of height in the Sun’s photosphere and low chromosphere. Instruments like the MOTH (Magneto-Optical filters at Two Heights), using a dual-channel based on MOFs operating at 589.0 nm (Na D2line) and 769.9 nm (K D1line), the VAMOS instrument (Velocity And Magnetic Observations of the Sun), operating at 769.9 nm (K D1 line), and the future TSST (Tor Vergata Synoptic Solar Telescope), using a dual-channel telescope operating at 656.28 nm (H-alpha line) and at 769.9 nm (K D1 line), allow to face both aspects, the scientific and the operative related to Space Weather applications. The MOTH, VAMOS and TSST data enable a wide variety of studies of the Sun, from seismic probing of the solar interior (sound speed, rotation, details of the tachocline, sub-surface structure of active regions), to the dynamics and magnetic evolution of the lower part of the solar atmosphere (heating of the solar atmosphere, identification of the signatures of solar eruptive events, atmospheric gravity waves, etc.), to the 3D reconstruction of the solar atmosphere and flare locations. However, the use of MOF filters requires special care in calibrating the data for scientific or operational use. This work presents a systematic pipeline that derives from the decennial use of MOF’s technology. More in detail, the pipeline is based on data reduction procedures tested and validated on MOTH data acquired at Mees Solar Observatory of the University of Hawaii Haleakala Observatories and at South Pole Solar Observatory (SPSO), at the Amundsen-Scott South Pole Station in Antarctica, during Antarctica Summer Campaign 2016/17.

The mini-neutron monitor: a new approach in neutron monitor design

The near-Earth cosmic ray flux has been monitored for more than 70 years by a network of ground-based neutron monitors (NMs). With the ever-increasing importance of quantifying the radiation risk and effects of cosmic rays for, e.g., air and space-travel, it is essential to continue operating the existing NM stations, while expanding this crucial network. In this paper, we discuss a smaller and cost-effective version of the traditional NM, the mini-NM. These monitors can be deployed with ease, even to extremely remote locations, where they operate in a semi-autonomous fashion. We believe that the mini-NM, therefore, offers the opportunity to increase the sensitivity and expand the coverage of the existing NM network, making this network more suitable to near-real-time monitoring for space weather applications. In this paper, we present the technical details of the mini-NM’s design and operation, and present a summary of the initial tests and science results.

Development of a 3‐D Plasmapause Model With a Back‐Propagation Neural Network

AbstractSeveral empirical models have been previously developed to study the characteristics of the global plasmasphere. A three‐dimensional solar wind‐driven global dynamic plasmapause model was developed in this study using a back‐propagation neural network based on multisatellite measurements. Our database contains 37,859 plasmapause crossing events from 4 January 1995 to 31 December 2015 covering all 24 magnetic local times (MLTs) from 66° to 79° magnetic latitudes. This model is parameterized by solar wind speed , interplanetary magnetic field , SYM‐H, and indices with smooth MLTs and latitude dependence. As the first 3‐D empirical model, this model corresponds to the true plasmapause structure and is useful for observing space weather and other applications especially for predicting the shape of the plasmapause by forecasting the input parameters. Moreover, the proposed model is not only highly sensitive to these parameters, but also to their changes over days, seasons, and years; this means that the diurnal, seasonal, and annual variations of the parameters can be captured by the model. Therefore, this model can provide a more accurate plasmapause position compared with previous models and can also be used as a basic reference to develop other models such as a global plasmaspheric density model.

Ionospheric response to solar and interplanetary disturbances: a Swarm perspective.

The ionospheric response to solar and interplanetary disturbances has been the subject of intense study for several decades. For 5 years now, the European Space Agency's Swarm fleet of satellites surveys the Earth's topside ionosphere, measuring magnetic and electric fields at low-Earth orbit with unprecedented detail. Herein, we study in situ the ionospheric response in terms of the occurrence of plasma instabilities based on 2 years of Swarm observations. Plasma instabilities are an important element of space weather because they include irregularities like the equatorial spread F events, which are responsible for the disruption of radio communications. Moreover, we focus on three out of the four most intense geospace magnetic storms of solar cycle 24 that occurred in 2015, including the St Patrick's Day event, which is the strongest magnetic storm of the present solar cycle. We examine the associated ionospheric response at Swarm altitudes through the estimation of a Swarm Dst-like index. The newly proposed Swarm derived Dst index may be suitable for space weather applications. This article is part of the theme issue 'Solar eruptions and their space weather impact'.

Analysis of sub-GLE and GLE events using NM data: space weather applications

Detailed study of solar energetic particle events is important to understand their acceleration and propagation in the interplanetary space and allows one to model various processes related to space weather and space climate e.g. radiation environment at flight altitudes and atmospheric ionization. A special class of events, called ground level enhancements, registered by ground based detectors, can dramatically change the radiation environment in the Earth’s atmosphere. New recently installed high-altitude polar neutron monitors NMs, namely DOMC/B and historically installed South Pole, have made the worldwide neutron monitor network more sensitive to strong solar energetic particle events, registered at ground level. The two high-altitude polar stations are able to detect lower energy events, which most likely would not be registered by the other (near sea level) neutron monitor stations. Here, using the worldwide neutron monitor database (NMDB) records and an optimization procedure combined with simulations, we assess the spectral and angular characteristics of a new class of events sub-GLEs. With the estimated spectral characteristics as an input, we evaluate the effective dose rate in polar and sub-polar regions at typical commercial flight altitude during such events as well as during GLEs.

Modeling Geoelectric Fields in Ireland and the UK for Space Weather Applications

AbstractGeoelectric fields at the Earth's surface caused by geomagnetic storms have the potential to disrupt and damage ground‐based infrastructure such as electrical power distribution networks, pipelines, and railways. Here we model geoelectric fields in Ireland and the UK during both quiet and active time intervals of geomagnetic conditions using measurements from magnetic observatories and electromagnetic tensor relationships. The analysis focused on (1) defining periods of the magnetic field variations that are largely affected by the geomagnetic storms, between 30 and 30,000 s; (2) constraining the electromagnetic tensor relationships that defines the Earth's response to magnetic field variations; (3) implementing and validating two approaches for modeling geoelectric fields based on measurements from magnetic observatories and local and interstation electromagnetic transfer functions; and (4) estimating uncertainties when modeling geoelectric fields. The use of interstation tensor relationships allowed us to differentiate between regional and local geomagnetic sources. We found coherence values of 0.5–0.95, signal‐to‐noise ratio of 1–15 dB, normalized root‐mean‐square values of 0.8–3.4, and root‐mean‐square values of 0.7–84 mV/km. Within these ranges of values, sites in close proximity (<100 km) to a magnetic observatory and not affected by local storms will provide the most accurate results, while sites located at further distances and affected by spatially localized features of the storm will be less accurate. These methods enable us to more accurately model geomagnetically induced currents, and their associated uncertainties, in the British and Irish power networks.

The First Solar Flare Effect Observation at UiTM-SID Station during Solar Cycle 23-24

International Heliophysical Year (IHY; 2007-2009) has a remarkable impact on space and earth electromagnetism research and society. For Malaysian perspectives, it acts as a spiral point to the expanding of space weather-related research. The research activities involve installation of real-time Magnetic Data Acquisition System of Circum-pan Pacific Magnetometer Network, i.e. MAGDAS/CPMN for space weather study and application, which was deployed for the IHY; 2007-2009. In addition to MAGDAS system, to understand the characteristics of the lower ionospheric layer (60-150km) during space weather events, a Very Low Frequency (VLF) monitoring system has been developed. The MAGDAS and VLF monitoring system called UiTM-SID are located at Universiti Pendidikan Sultan Idris, UPSI (3.71’, 101.53’), Malaysia. The first observation effects of solar flare during November 2016 to March 2017, for the period of a minimum solar cycle 23-24 have been examined on sub-ionospheric VLF signals from VTX4 (19.2 kHz) and NWC (19.8 kHz) transmitter monitored at UPSI. In general, the level of amplitude reading for VTX4 signals is higher than NWC signals for quite diurnal variations. The effects of the solar flare class C7.5 on 29th November 2016 shows an enhancement of amplitude due to increase in the lower region electron density by the radiation of solar flare. The average daily amplitude reading was compared to the average value of solar flare event, the result shows the percentage difference is 12% increased in VTX4 and NWC signals.

Measurement of the polarisation in the auroral N2+ 427.8 nm band

In this paper, we provide for the first time polarisation measurements of the N+2 band at 427.8 nm performed with Premier Cru, a dedicated spectropolarimeter to investigate the polarisation of auroral emission lines between 400 and 700 nm. Details about the instrument, the observing conditions and the data analysis procedure are provided. Results obtained during three nights in March 2017 in Skibotn, Norway, indicate that the auroral blue line is polarised with a degree of linear polarisation of a few %. Due to weak Signal-to-Noise Ratios (SNR), these measurements still need to be taken with caution since none of the individual data set has a detection with a 3σ confidence level. However, results integrated over the entire observing period each night do show a 3σ detection but due to the long integration period, the origin of this polarisation cannot be linked to a specific type of aurora (diffuse vs structured arc) or specific ionospheric or geomagnetic conditions. These observations need to be confirmed with an improved design to increase the SNR and decrease the exposure time. When available, these improved measurements of the blue line polarisation will be important to better understand the physics of auroral processes at altitudes below 100 km where the N2+ emission occurs and possibly for space weather applications if the polarisation varies with ionospheric/geomagnetic conditions.

Assessment of Current Capabilities in Modeling the Ionospheric Climatology for Space Weather Applications: foF2 and hmF2

AbstractThis paper presents preliminary results of a metrics‐based assessment of current modeling capabilities in predicting the ionospheric climatology for two ionospheric characteristics, the foF2 and hmF2. This work is part of the activities of the Ionosphere Working Group of the International Forum for Space Weather Modeling Capabilities Assessment that is facilitated by the Community Coordinated Modeling Center. The results are based on the comparison between modeled and observed monthly medians of the foF2 and hmF2. Modeling formulations considered here include two empirical models (the International Reference Ionosphere [IRI] and Massachusetts Institute of Technology [MIT] Empirical model), as well as two physics‐based, coupled ionosphere‐thermosphere models (the Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics [CTIPe] and Thermosphere‐Ionosphere‐Electrodynamics General Circulation Model [TIE‐GCM]). The comparisons were carried out in year 2012 over seven ionospheric locations distributed worldwide in the Northern Hemisphere. Based on our findings, although significant errors are occasionally obtained from all modeling approaches, empirical models tend to provide systematically better correlation with the observed medians and follow the observed distributions more successfully, offering smaller prediction errors than the physics‐based ones. In case of foF2, the averaged prediction accuracy in terms of root‐mean‐square error (RMSE) ranges around 1.5 MHz for physics‐based models and 0.5 MHz for empirical models. In case of hmF2, it ranges around 30 and 20 km, respectively. The prediction accuracy presents strong seasonal and local time dependence, which differs for different models and ionospheric characteristics (i.e., foF2 or hmF2): it is strong for physics‐based models, weaker for IRI, and very weak for MIT empirical model. This latter outcome may provide suggestive input for future improvements.

Communicating Uncertainty and Reliability in Space Weather Data, Models, and Applications

AbstractSpace Weather Journal editors advocate for discussion of uncertainty and reliability in future journal manuscripts and throughout the space weather enterprise.

Rigidity dependence of Forbush decreases in the energy region exceeding the sensitivity of neutron monitors

Applicability of our present setup for solar modulation studies in a shallow underground laboratory is tested on four prominent examples of Forbush decrease during solar cycle 24. Forbush decreases are of interest in space weather application and study of energy-dependent solar modulation, and they have been studied extensively. The characteristics of these events, as recorded by various neutron monitors and our detectors, were compared, and rigidity spectrum was found. Linear regression was performed to find power indices that correspond to each event. As expected, a steeper spectrum during more intense extreme solar events with strong X-flares shows a greater modulation of galactic cosmic rays. Presented comparative analysis illustrates the applicability of our setup for studies of solar modulation in the energy region exceeding the sensitivity of neutron monitors.

A method for automatic detection of equatorial spread-F in ionograms

A method is presented for automatic detection of spread-F. The method is based on an image recognition technique and is applied to ionograms recorded at the ionospheric station of Tucumán (26.9°S, 294.6°E). The performance achieved is statistically evaluated and demonstrated with significant examples. The proposed method improves Autoscala's ability to reject ionograms with insufficient information, including those featuring Spread-F. Automatic identification of cases of spread-F is of additional interest in Space Weather applications, when it helps detect degraded radio propagation conditions.The present data analysis is a retrospective study but forms the basis for real-time application as an extension of Autoscala’s capabilities.

Perturbed Input Ensemble Modeling With the Space Weather Modeling Framework

AbstractTo assess the effect of uncertainties in solar wind driving on the predictions from the operational configuration of the Space Weather Modeling Framework, we have developed a nonparametric method for generating multiple possible realizations of the solar wind just upstream of the bow shock, based on observations near the first Lagrangian point. We have applied this method to the solar wind inputs at the upstream boundary of Space Weather Modeling Framework and have simulated the geomagnetic storm of 5 April 2010. We ran a 40‐member ensemble for this event and have used this ensemble to quantify the uncertainty in the predicted Sym‐H index and ground magnetic disturbances due to the uncertainty in the upstream boundary conditions. Both the ensemble mean and the unperturbed simulation tend to underpredict the magnitude of Sym‐H in the quiet interval before the storm and overpredict in the storm itself, consistent with previous work. The ensemble mean is a more accurate predictor of Sym‐H, improving the mean absolute error by nearly 2 nT for this interval and displaying a smaller bias. We also examine the uncertainty in predicted maxima in ground magnetic disturbances. The confidence intervals are typically narrow during periods where the predicted dBH/dt is low. The confidence intervals are often much wider where the median prediction is for enhanced dBH/dt. The ensemble also allows us to identify intervals of activity that cannot be explained by uncertainty in the solar wind driver, driving further model improvements. This work demonstrates the feasibility and importance of ensemble modeling for space weather applications.

Prospective research on modeling of GNSS tropospheric delays for improving the accuracy of weather forecast in Indonesia

This paper overviews the prospect of utilizing Global Navigation Satellite Systems (GNSS) tropospheric delays to improve the accuracy of weather forecasts as well as environmental models toward effective management and decision-making. As well reports the application of GNNS technique for investigation of space weather and meteorological applications that have been conducted in the South Pole (Antarctica) and North Pole (Arctic). The revelation of the previous research provides further direction, what is the best approach that can be done to solve local problems but can give global impacts. In this case highlighted the application of GNSS technique for monitoring the volcanic activity in the Special Region of Yogyakarta, Indonesia.

Empirical forecast of quiet time ionospheric Total Electron Content maps over Europe

An accurate forecast of the atmospheric Total Electron Content (TEC) is helpful to investigate space weather influences on the ionosphere and technical applications like satellite-receiver radio links. The purpose of this work is to compare four empirical methods for a 24-h forecast of vertical TEC maps over Europe under geomagnetically quiet conditions.TEC map data are obtained from the Space Weather Application Center Ionosphere (SWACI) and the Universitat Politècnica de Catalunya (UPC). The time-series methods Standard Persistence Model (SPM), a 27 day median model (MediMod) and a Fourier Series Expansion are compared to maps for the entire year of 2015. As a representative of the climatological coefficient models the forecast performance of the Global Neustrelitz TEC model (NTCM-GL) is also investigated. Time periods of magnetic storms, which are identified with the Dst index, are excluded from the validation.By calculating the TEC values with the most recent maps, the time-series methods perform slightly better than the coefficient model NTCM-GL. The benefit of NTCM-GL is its independence on observational TEC data. Amongst the time-series methods mentioned, MediMod delivers the best overall performance regarding accuracy and data gap handling. Quiet-time SWACI maps can be forecasted accurately and in real-time by the MediMod time-series approach.

An initial ULF wave index derived from 2 years of Swarm observations

Abstract. The ongoing Swarm satellite mission provides an opportunity for better knowledge of the near-Earth electromagnetic environment. Herein, we use a new methodological approach for the detection and classification of ultra low-frequency (ULF) wave events observed by Swarm based on an existing time-frequency analysis (TFA) tool and utilizing a state-of-the-art high-resolution magnetic field model and Swarm Level 2 products (i.e., field-aligned currents – FACs – and the Ionospheric Bubble Index – IBI). We present maps of the dependence of ULF wave power with magnetic latitude and magnetic local time (MLT) as well as geographic latitude and longitude from the three satellites at their different locations in low-Earth orbit (LEO) for a period spanning 2 years after the constellation's final configuration. We show that the inclusion of the Swarm single-spacecraft FAC product in our analysis eliminates all the wave activity at high altitudes, which is physically unrealistic. Moreover, we derive a Swarm orbit-by-orbit Pc3 wave (20–100 MHz) index for the topside ionosphere and compare its values with the corresponding variations of solar wind variables and geomagnetic activity indices. This is the first attempt, to our knowledge, to derive a ULF wave index from LEO satellite data. The technique can be potentially used to define a new Level 2 product from the mission, the Swarm ULF wave index, which would be suitable for space weather applications. Keywords. Space plasma physics (waves and instabilities)

The Impacts of the Ionospheric Observable and Mathematical Model on the Global Ionosphere Model

A high-accuracy Global Ionosphere Model (GIM) is significant for precise positioning and navigating with the Global Navigation Satellite System (GNSS), as well as space weather applications. To obtain a precise GIM, it is critical to take both the ionospheric observable and mathematical model into consideration. In this contribution, the undifferenced ambiguity-fixed carrier-phase ionospheric observable is first determined from a global distribution of permanent receivers. Accuracy assessment with a co-located station experiment shows that the observational errors affecting the ambiguity-fixed carrier-phase ionospheric observables range from 0.10 to 0.35 Total Electron Content Units (TECUs, where 1 TECU = 10 16 e − / m 2 and corresponds to 0.162 m on the Global Positioning System, GPS L1 frequency), indicating that the ambiguity-fixed carrier-phase ionospheric observable is over one order of magnitude more accurate than the carrier-phase leveled-code one (from 1.21 to 3.77 TECUs). Second, to better model the structure of the ionosphere, a two-layer GIM has been built based on the above carrier-phase observable. Preliminary global accuracy evaluation demonstrates that the accuracy of the two-layer GIM is below 1 TECU and about 2 TECUs during low and high solar activity periods. Third, the single-frequency point positioning experiment is adopted to test the ionosphere mitigation effects of the GIMs. Positioning results demonstrate that the single-frequency positioning accuracy can be improved by more than 30% using the undifferenced ambiguity-fixed ionospheric observable-derived two-layer GIM, compared with that using the carrier-phase leveled-code ionospheric observable-based single-layer GIM.