Journal of Space Weather and Space Climate最新文献

{"title":"Quasi-stationary substructure within a sporadic E layer observed by the Low Frequency Array (LOFAR)","authors":"A. Wood, G. Dorrian, B. Boyde, R. Fallows, David Themens, M. Mevius, Tim Sprenger, Robert Main, S. Eleri Pryse, S. Elvidge","doi":"10.1051/swsc/2024024","DOIUrl":"https://doi.org/10.1051/swsc/2024024","url":null,"abstract":"Observations made with the Low Frequency Array (LOFAR) have been used to infer the presence of variations in a sporadic E layer on a spatial scale of several kilometres and a temporal scale of ~10 minutes. LOFAR stations across the Netherlands observed Cygnus A between 17 UT and 18 UT on 14th July 2018 at frequencies between 24.9 MHz and 64.0 MHz. Variations in the relative signal intensity, together with consideration of geometric optics, were used to infer the presence of a plasma structure. Spatial variations between the stations and the dispersive nature of the observations suggested that this plasma structure was located within the ionosphere. Independent confirmation of the presence of a sporadic E layer, and variation within it, was obtained from observations made by the Juliusruh ionosonde (54.6° N, 13.4° E), which observed reflection of radio waves at an altitude of ~120 km and from frequencies of up to ~6 MHz. The large number (38) of LOFAR stations across the Netherlands together with the sub-second temporal resolution and broadband frequency coverage of the observations enabled the fine details of the spatial variation and the evolution of the structure to be determined. The structure was quasi-stationary, moving at ~12 m s-1, and it exhibited significant variation on spatial scales of a few kilometres. The observations were consistent with the steepening of a plasma density gradient at the edge of the feature over time due to an instability process. A 1-D numerical model showed that the observations were consistent with an electron density enhancement in the sporadic E layer with a density change of 2x1011 m-3 and a spatial scale of several kilometres. Collectively, these results show the ability of LOFAR to observe substructure within sporadic E layers and how this substructure varies with time. They also show the potential value of such datasets to constrain models of instability processes, or to discriminate between competing models.","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" 43","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141825278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Characterizing the distribution of extreme geoelectric field events in Sweden","authors":"V. Lanabere, Andrew P. Dimmock, L. Rosenqvist, A. Viljanen, L. Juusola, A. Johlander","doi":"10.1051/swsc/2024025","DOIUrl":"https://doi.org/10.1051/swsc/2024025","url":null,"abstract":"Historically, Sweden has reported several impacts on transformers and transmission lines related to geomagnetically induced currents (GICs) that develop during strong space weather events. GICs are driven by the geoelectric field (E), and their intensity depends on various factors, including the lithology conductivity and the rate of change of the Earth's magnetic field. The purpose of this study is to perform an extreme value analysis (EVA) of the E magnitude at six different latitudes in Sweden and to express the maximum |E| that might be observed in 10, 50 and 100 years. We analyzed 10-second E data in Sweden, which was obtained from a 1-D model. This model incorporates 10-second geomagnetic measurements from the IMAGE network and the vertical Earth's ground electrical conductivity in Sweden, extracted from a 3-D conductance map for the Fennoscandian region. Extreme E events tend to occur in clusters around geomagnetic disturbances (substorms and geomagnetic storms). Therefore, we applied two different methods to decluster the data. After declustering, Generalized Pareto (GP) distributions were fitted to the remaining extreme events that exceed the 99.5th percentile. The EVA indicates that the shape parameter of the GP distribution depends on latitude. This implies that at higher geographic latitudes (64.52-68.02°N) the distribution decreases faster toward zero than at lower latitudes (58.26-62.25°N). As a result the expected maximum |E| in 100-years in central Sweden ranges between 4.0-8.5 V/km, while at higher latitudes, it ranges between 2.0-2.5 V/km similar to the modeled geoelectric field values during the Halloween event in October 2003. In particular, around 60.50°N the distribution of extreme events exhibits the heaviest tail. When we additionally consider the effect of conductivity, the region of west Sweden around 60.50°N exhibits the largest expected maximum in 100-years with a value around 8.5 V/km. This is three times larger the maximum modeled |E| at that latitude.","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"21 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141639777","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long term relationships of electron density with solar activity","authors":"N. Jakowski, M. Mainul Hoque, J. Mielich","doi":"10.1051/swsc/2024023","DOIUrl":"https://doi.org/10.1051/swsc/2024023","url":null,"abstract":"Greenhouse gases such as carbon dioxide and methane that are causing climate change may cause long term trends in the thermosphere and ionosphere. The paper aims to contribute to explore long term effects in the ionosphere focusing on the impact of solar activity changes.\u0000Peak electron density data derived from vertical sounding measurements covering 65 years at the ionosonde stations Juliusruh (JR055), Boulder (BC840) and Kokubunji (TO536), have been utilized to estimate the long-term behavior of daytime ionospheric F2 layer ionization in relation to the solar 10.7 cm radio flux index F10.7. In parallel, Global Navigation Satellite System (GNSS) based vertical total electron content (TEC) data over the ionosonde stations in combination with the peak electron density data have been used to derive the equivalent slab thickness τ for estimating long-term behavior in the time period 1996-2022. A new approach has been developed for deriving production and loss term proxies for studying long-term ionization effects from F2 layer peak electron density and TEC data. The derived coefficients allow estimating the long-term variation of atomic oxygen and molecular nitrogen concentrations including their ratio during winter months.\u0000The noon-time slab thickness values over Juliusruh correlate well with the decrease of F10.7 and the F2 layer peak height and enable estimating the neutral gas temperature. The equivalent slab thickness decreases by about 20 km per decade in the period 1996-2022, indicating a thermospheric cooling by about 100 K per decade for Juliusruh. Whereas the oxygen concentration decreases, the loss term, considered as a proxy for molecular components of the neutral gas, in particular N2, increases with the long-term solar activity variation. Considering 11 years averages of the production and loss terms under wintertime conditions, the long-term study reveals for the O/N2 ratio a percentage decrease of 5% per decade and for F10.7 about 3.1% per decade in a linear approach referred to the year 1970. Linear models of 11 years averaged NmF2 and foF2 from corresponding F10.7 show a very close correlation with the temporal variation of F10.7 until about 1990. The root mean square errors are in the order of 1.0 -1.3 ‧1010m-3 for NmF2 and 0.03-0.05 MHz for foF2. After 1990 the linear models clearly deviate from F10.7 at all selected ionosonde stations indicating a non-local effect.","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"2 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141683948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Modeling Study of ≥2 MeV Electron Fluxes in GEO at Different Prediction Time Scales Based on LSTM and Transformer Networks","authors":"Xiaojing Sun, Dedong Wang, A. Drozdov, Ruilin Lin, Artem Smirnov, Yuri Shprits, Siqing Liu, B. Luo, Xi Luo","doi":"10.1051/swsc/2024021","DOIUrl":"https://doi.org/10.1051/swsc/2024021","url":null,"abstract":"In this study, we develop models to predict log10 of ≥2 MeV electron fluxes with 5-minute resolution at the geostationary orbit using the Long Short-Term Memory (LSTM) and transformer neural networks for next 1-hour, 3-hour, 6-hour, 12-hour, and 1-day predictions. The data of GOES-10 satellite from 2002 to 2003 are the training set, the data in 2004 are the validation set, and the data in 2005 are the test set. For different prediction time scales, different input combinations with four days as best offset time are tested and it is found that the transformer models perform better than the LSTM models, especially for higher flux values. The best combinations for the transformer models for next 1-hour, 3-hour, 6-hour, 12-hour, 1-day predictions are (log10 Flux, MLT), (log10 Flux, Bt, AE, SYM-H), (log10 Flux, N), (log10 Flux, N, Dst, Lm), and (log10 Flux, Pd, AE) with PE values of 0.940, 0.886, 0.828, 0.747, and 0.660 in 2005, respectively. When the low flux outliers of the ≥2 MeV electron fluxes are excluded, the PE (prediction efficiency) values for the 1-hour and 3-hour predictions increase to 0.958 and 0.900. By evaluating the prediction of ≥2 MeV electron daily and hourly fluences, the PE values of our transformer models are 0.857 and 0.961, respectively, higher than those of previous models. In addition, our models can be used for filling the data gaps of ≥2 MeV electron fluxes.","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"140 15","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141350901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Energetic particle acceleration and transport with the novel Icarus+PARADISE model","authors":"E. Husidic, N. Wijsen, T. Baratashvili, S. Poedts, Rami Vainio","doi":"10.1051/swsc/2024009","DOIUrl":"https://doi.org/10.1051/swsc/2024009","url":null,"abstract":"With the rise of satellites and mankind's growing dependence on technology, there is an increasing awareness of space weather phenomena related to high-energy particles. Shock waves driven by coronal mass ejections (CMEs) and corotating interaction regions (CIRs) occasionally act as potent particle accelerators, generating hazardous solar energetic particles (SEPs) that pose risks to satellite electronics and astronauts. Numerical simulation tools capable of modelling and predicting large SEP events are thus highly demanded. We introduce the new Icarus+PARADISE model as an advancement of the previous EUHFORIA+PARADISE model. Icarus, based on the MPI-AMRVAC framework, is a three-dimensional magnetohydrodynamic code that models solar wind configurations from 0.1 au onwards, encompassing transient structures like CMEs or CIRs. Differing from EUHFORIA's uniform-only grid, Icarus incorporates solution adaptive mesh refinement (AMR) and grid stretching. The particle transport code PARADISE propagates energetic particles as test particles through these solar wind configurations by solving the focused transport equation in a stochastic manner. We validate our new model by reproducing EUHFORIA+PARADISE results. This is done by modelling the acceleration and transport of energetic particles in a synthetic solar wind configuration containing an embedded CIR.  Subsequently, we illustrate how the simulation results vary with grid resolution by employing different levels of AMR.. The resulting intensity profiles illustrate increased particle acceleration with higher levels of AMR in the shock region, better capturing the effects of the shock.","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"142 23","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140369203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Advancements in Solar Spectral Irradiance Measurements by the TSIS-1 Spectral Irradiance Monitor and Its Role for Long-term Data","authors":"Erik C. Richard, O. Coddington, Dave Harber, M. Chambliss, Steven Penton, Keira Brooks, Luke Charbonneau, Courtney Peck, Stéphane Béland, P. Pilewskie, Tom Woods","doi":"10.1051/swsc/2024008","DOIUrl":"https://doi.org/10.1051/swsc/2024008","url":null,"abstract":"The first implementation of NASA’s Total and Spectral Solar Irradiance Sensor (TSIS-1) launched on December 15th, 2017 and was integrated on the International Space Station (ISS) to measure both the total solar irradiance (TSI) and the solar spectral irradiance (SSI). The direct measurement of the SSI is made by the LASP Spectral Irradiance Monitor (SIM) and provides data essential to interpreting how the Earth system responds to solar spectral variability. Extensive advances in TSIS-1 SIM instrument design and new SI-traceable spectral irradiance calibration techniques have resulted in improved absolute accuracy with uncertainties of less than 0.5% over the continuous 200 to 2400 nm spectral range. Furthermore, improvements in the long-term spectral stability corrections provide lower trend uncertainties in SSI variability measurements. Here we present the early results of the TSIS-1 SIM measurements covering the first 5 years of operations. This time-period includes the descending phase of solar cycle 24, the last solar minimum, and the ascending phase of solar cycle 25. The TSIS-1 SIM SSI results are compared to previous measurements both in the absolute scale of the solar spectrum and the time dependence of the SSI variability. The TSIS-1 SIM SSI spectrum shows lower IR irradiance (up to 6% at 2400 nm) and small visible increases (~0.5%) from some previous reference solar spectra. Finally, initial comparisons are made to current NRLSSI2 and SATIRE-S SSI model results and offer opportunities to validate model details both for short-term (solar rotation) spectral variability and, for the first time, the longer-term (near half solar cycle) spectral variability across the solar spectrum from the UV to the IR.","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140220702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Upgrades of the ESPERTA forecast tool for Solar Proton Events","authors":"M. Laurenza, M. Stumpo, Pietro Zucca, Mattia Mancini, S. Benella, L. Clark, Tommaso Alberti, Maria Federica Marcucci","doi":"10.1051/swsc/2024007","DOIUrl":"https://doi.org/10.1051/swsc/2024007","url":null,"abstract":"The Empirical model for Solar Proton Events Real Time Alert (ESPERTA) exploits three solar parameters (flare longitude, soft X-ray fluence, and radio fluence) to provide a timely prediction for the\u0000occurrence of solar proton events (SPEs, i.e., when the $>$10MeV proton flux is $geq$10 pfu) after the emission of a $geq$ M2 flare. In addition, it makes a prediction for the more geoeffective SPEs for which the $>$10 MeV proton flux is $geq$ 100 pfu. In this paper, we study two different ways to upgrade the ESPERTA model and implement it in real time: 1) by using ground based observations from the LOFAR stations; 2) by applying a novel machine\u0000learning algorithm to flare-based parameters to provide early warnings of SPE occurrence together with a fine-tuned radiation storm level. As a last step, we perform a preliminary study using a neural network to forecast the proton flux profile to complement the ESPERTA tool.\u0000We evaluate the models over flare and SPE data the last two solar cycles and discuss the performance and the limits and advantages of the three methods.","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"17 7","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140239212","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Global Solar Photospheric and Coronal Magnetic Field over Activity Cycles 21-25","authors":"G. Petrie","doi":"10.1051/swsc/2024005","DOIUrl":"https://doi.org/10.1051/swsc/2024005","url":null,"abstract":"The evolution of the global solar magnetic field from the beginning of cycle 21 (mid-1970s) until the currently-ascending cycle 25 is described using photospheric full-disk and synoptic magnetograms from NSO Kitt Peak Vacuum Telescope (KPVT) 512-channel and Spectromagnetograph (SPMG) and the Synoptic Optical Long-term Investigation of the Sun (SOLIS) Vector Spectro-Magnetograph (VSM) and Global Oscillations Network Group (GONG), and Stanford University's Wilcox Solar Observatory (WSO). The evolving strength and symmetry of the global coronal field is described by potential-field source-surface models decomposed into axisymmetric and non-axisymmetric, and even- and odd-ordered magnetic multipoles. The overall weakness of the global solar magnetic field since cycle 23 splits the 50-year observing window into the stronger, simpler, more hemispherically symmetric cycles 21 and 22 and the weaker, more complex cycles 23 and 24. An anomalously large decrease in the global solar field strength occurred during cycle 23, and an anomalously weak axial/polar field resulted from that cycle, accompanied by an anomalously weak radial interplanetary magnetic field (IMF) during cycle 23 activity minimum and a weakened radial IMF overall since cycle 23. The general long-term decline in solar field strength and the development during cycle 24 of strong swings of hemispheric and polar asymmetry are analyzed in detail, including their transfer through global coronal structural changes to dominate mean in situ interplanetary field measurements for several years. Although more symmetric than cycle 24, the rise phase of cycle 25 began with the southern leading the northern hemisphere, but the north has recovered to lead this cycle's polar field reversal. The mean polar flux (poleward of $pm 60^{circ}$) has reversed at each pole, so far more symmetrically than the cycle 23 and 24 polar reversals.","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"11 6","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140438931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Erratum for article: “Forecasting Solar Energetic Proton Integral Fluxes with Bi-Directional Long Short-Term Memory Neural Networks”","authors":"Mohamed Nedal","doi":"10.1051/swsc/2023031","DOIUrl":"https://doi.org/10.1051/swsc/2023031","url":null,"abstract":"","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139213051","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"No signature of extreme solar energetic particle events in high-precision 14C data from the Alaskan tree for 1844–1876 CE","authors":"F. Miyake, M. Hakozaki, Hisashi Hayakawa, Naruki Nakano, Lukas Wacker","doi":"10.1051/swsc/2023030","DOIUrl":"https://doi.org/10.1051/swsc/2023030","url":null,"abstract":"Cosmogenic nuclides—14C from tree rings and 10Be & 36Cl from ice cores serve as an effective proxy for past extreme solar energetic particle (SEP) events. After identifying the first signature of an extreme SEP event in 774 CE, several candidates have been found in these proxy archives, such as 993 CE, 660 BCE, and 7176 BCE. Their magnitudes have been estimated to be tens of times larger than that of the largest SEP event ever observed since 1950s. Although a detailed survey of such extreme SEP events is ongoing, the detection of intermediate-sized SEP events that bridge the gap between modern observations and extreme events detected in cosmogenic nuclides has not progressed sufficiently, primarily because of the uncertainties in cosmogenic nuclide data. In this study, we measured 14C concentrations in tree rings in the 19th century (1844–1876 CE) to search for any increases in 14C concentrations corresponding to intermediate-size extreme SEP events. We utilized Alaskan tree-ring samples cut into early and latewoods to suppress the potential seasonal variations in intra-annual 14C data. Notably, no significant 14C variations were observed between early and latewoods (0.0 ± 0.3‰), and the annual resolution 14C data series displayed an error of ~0.8‰. Over the entire study period, no significant increase in 14C concentrations characterized by other candidates of extreme SEP events such as the 774 CE event was detected in the annual 14C data. The present result imposes a constraint on the SEP fluence when the largest-class of recorded solar storms occurred (especially those in 1859 CE and 1872 CE).","PeriodicalId":510580,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139211078","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}