R. Fiori, Vickal V. Kumar, D. Boteler, M. Terkildsen
High frequency (HF) radio wave propagation is sensitive to space weather induced ionospheric disturbances that result from enhanced photoionization and energetic particle precipitation. Recognizing the potential risk to HF radio communication systems used by the aviation industry, as well as potential impacts to GNSS navigation and the risk of elevated radiation levels, the International Civil Aviation Organization (ICAO) initiated development of a space weather advisory service. For HF systems, this service specifically identifies shortwave fadeout, auroral absorption, polar cap absorption, and post storm maximum useable frequency depression (PSD) as phenomena impacting HF radio communication, and specifies moderate and severe event thresholds to describe event severity. This paper examines the occurrence rate and duration of events crossing the moderate and severe thresholds. Shortwave fadeout was evaluated based on thresholds in the solar X-ray flux. Analysis of 40-years of solar X-ray flux data showed that moderate and severe level solar X-ray flares were observed, on average, 123 and 5 times per 11-year solar cycle, respectively. The mean event duration was 68 minutes for moderate level events and 132 minutes for severe level events. Auroral absorption events crossed the moderate threshold for 40 events per solar cycle, with a mean event duration of 5.1 hours. The severe threshold was crossed for 3 events per solar cycle with a mean event duration of 12 hours. Polar cap absorption had the longest mean duration at ~8 hours for moderate events and 1.6 days for severe events; on average, 24 moderate and 13 severe events observed per solar cycle. Moderate and severe thresholds for shortwave fadeout, auroral absorption, and polar cap absorption were used to determine the expected impacts on HF radio communication. Results for polar cap absorption and shortwave fadeout were consistent with each other, but the expected impact for auroral absorption was shown to be 2-3 times higher. Analysis of 22 years of ionosonde data showed moderate and severe PSD events occurred, on average, 200 and 56 times per 11-year solar cycle, respectively. The mean event duration was 5.5 hours for moderate level events and 8.5 hours for severe level events. During solar cycles 22 and 23, HF radio communication was expected to experience moderate or severe impacts due to the ionospheric disturbances caused by space weather a maximum of 163 and 78 days per year, respectively, due to the combined effect of absorption and PSD. The distribution of events is highly non-uniform with respect to solar cycle: 70% of moderate or severe events were observed during solar maximum compared to solar minimum.
{"title":"Occurrence rate and duration of space weather impacts to high frequency radio communication used by aviation","authors":"R. Fiori, Vickal V. Kumar, D. Boteler, M. Terkildsen","doi":"10.1051/swsc/2022017","DOIUrl":"https://doi.org/10.1051/swsc/2022017","url":null,"abstract":"High frequency (HF) radio wave propagation is sensitive to space weather induced ionospheric disturbances that result from enhanced photoionization and energetic particle precipitation. Recognizing the potential risk to HF radio communication systems used by the aviation industry, as well as potential impacts to GNSS navigation and the risk of elevated radiation levels, the International Civil Aviation Organization (ICAO) initiated development of a space weather advisory service. For HF systems, this service specifically identifies shortwave fadeout, auroral absorption, polar cap absorption, and post storm maximum useable frequency depression (PSD) as phenomena impacting HF radio communication, and specifies moderate and severe event thresholds to describe event severity. This paper examines the occurrence rate and duration of events crossing the moderate and severe thresholds. Shortwave fadeout was evaluated based on thresholds in the solar X-ray flux. Analysis of 40-years of solar X-ray flux data showed that moderate and severe level solar X-ray flares were observed, on average, 123 and 5 times per 11-year solar cycle, respectively. The mean event duration was 68 minutes for moderate level events and 132 minutes for severe level events. Auroral absorption events crossed the moderate threshold for 40 events per solar cycle, with a mean event duration of 5.1 hours. The severe threshold was crossed for 3 events per solar cycle with a mean event duration of 12 hours. Polar cap absorption had the longest mean duration at ~8 hours for moderate events and 1.6 days for severe events; on average, 24 moderate and 13 severe events observed per solar cycle. Moderate and severe thresholds for shortwave fadeout, auroral absorption, and polar cap absorption were used to determine the expected impacts on HF radio communication. Results for polar cap absorption and shortwave fadeout were consistent with each other, but the expected impact for auroral absorption was shown to be 2-3 times higher. Analysis of 22 years of ionosonde data showed moderate and severe PSD events occurred, on average, 200 and 56 times per 11-year solar cycle, respectively. The mean event duration was 5.5 hours for moderate level events and 8.5 hours for severe level events. During solar cycles 22 and 23, HF radio communication was expected to experience moderate or severe impacts due to the ionospheric disturbances caused by space weather a maximum of 163 and 78 days per year, respectively, due to the combined effect of absorption and PSD. The distribution of events is highly non-uniform with respect to solar cycle: 70% of moderate or severe events were observed during solar maximum compared to solar minimum.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"1 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-05-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41368122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Papaioannou, R. Vainio, O. Raukunen, P. Jiggens, À. Aran, M. Dierckxsens, S. Mallios, M. Paassilta, A. Anastasiadis
The Probabilistic Solar Particle Event foRecasting (PROSPER) model predicts the probability of occurrence and the expected peak flux of solar energetic particle (SEP) events. Predictions are derived for a set of integral proton energies (i.e., E > 10, > 30, and > 100 MeV) from characteristics of solar flares (longitude, magnitude), coronal mass ejections (width, speed), and combinations of both. Herein the PROSPER model methodology for deriving the SEP event forecasts is described, and the validation of the model, based on archived data, is presented for a set of case studies. The PROSPER model has been incorporated into the new operational advanced solar particle event casting system (ASPECS) tool to provide nowcasting (short term forecasting) of SEP events as part of ESA’s future SEP advanced warning system (SAWS). ASPECS also provides the capability to interrogate PROSPER for historical cases via a run-on-demand functionality.
{"title":"The probabilistic solar particle event forecasting (PROSPER) model","authors":"A. Papaioannou, R. Vainio, O. Raukunen, P. Jiggens, À. Aran, M. Dierckxsens, S. Mallios, M. Paassilta, A. Anastasiadis","doi":"10.1051/swsc/2022019","DOIUrl":"https://doi.org/10.1051/swsc/2022019","url":null,"abstract":"The Probabilistic Solar Particle Event foRecasting (PROSPER) model predicts the probability of occurrence and the expected peak flux of solar energetic particle (SEP) events. Predictions are derived for a set of integral proton energies (i.e., E > 10, > 30, and > 100 MeV) from characteristics of solar flares (longitude, magnitude), coronal mass ejections (width, speed), and combinations of both. Herein the PROSPER model methodology for deriving the SEP event forecasts is described, and the validation of the model, based on archived data, is presented for a set of case studies. The PROSPER model has been incorporated into the new operational advanced solar particle event casting system (ASPECS) tool to provide nowcasting (short term forecasting) of SEP events as part of ESA’s future SEP advanced warning system (SAWS). ASPECS also provides the capability to interrogate PROSPER for historical cases via a run-on-demand functionality.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44883102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Muralikrishna, Rafael Duarte Coelho dos Santos, Luis Eduardo Antunes Vieira
Studies of the Sun and the Earth's atmosphere and climate consider solar variability and its constant monitoring an important driver in climate models. Solar irradiance is one of the main parameters that allow monitoring this variation, which can be studied in spectrum ranges or in its version that integrates all those ranges. Some physical and semi-empirical models were developed and made available and are very relevant for the reconstruction of irradiance in periods of data failure or absence in the collection. However, the solar irradiance prediction could benefit ionospheric and climate models through prior knowledge of irradiance values hours or days ahead, without the need to know or have available other parameters that would be necessary for their reconstruction. This paper presents a neural network based approach, which uses images of the solar photosphere to extract sunspot and active region information and thus generate inputs for recurrent neural networks to perform the irradiance prediction. Experiments were performed with two recurrent neural network architectures for short- and long-term predictions of total and spectral solar irradiance along three wavelengths. The results show good quality of prediction results for TSI and motivate individual effort in improving the prediction of each type of irradiance predicted in this work. The results obtained for SSI point out that photosphere images do not have the same influence on the prediction of all wavelengths tested, but encourage the bet on new spectral lines prediction. The quality closeness in neural networks and physical models results raise the possibility that prediction is an option to be considered in studies for which only reconstructed data are considered.
{"title":"Exploring possibilities for solar irradiance prediction from solar photosphere images using recurrent neural networks","authors":"A. Muralikrishna, Rafael Duarte Coelho dos Santos, Luis Eduardo Antunes Vieira","doi":"10.1051/swsc/2022015","DOIUrl":"https://doi.org/10.1051/swsc/2022015","url":null,"abstract":"Studies of the Sun and the Earth's atmosphere and climate consider solar variability and its constant monitoring an important driver in climate models. Solar irradiance is one of the main parameters that allow monitoring this variation, which can be studied in spectrum ranges or in its version that integrates all those ranges. Some physical and semi-empirical models were developed and made available and are very relevant for the reconstruction of irradiance in periods of data failure or absence in the collection. However, the solar irradiance prediction could benefit ionospheric and climate models through prior knowledge of irradiance values hours or days ahead, without the need to know or have available other parameters that would be necessary for their reconstruction. This paper presents a neural network based approach, which uses images of the solar photosphere to extract sunspot and active region information and thus generate inputs for recurrent neural networks to perform the irradiance prediction. Experiments were performed with two recurrent neural network architectures for short- and long-term predictions of total and spectral solar irradiance along three wavelengths. The results show good quality of prediction results for TSI and motivate individual effort in improving the prediction of each type of irradiance predicted in this work. The results obtained for SSI point out that photosphere images do not have the same influence on the prediction of all wavelengths tested, but encourage the bet on new spectral lines prediction. The quality closeness in neural networks and physical models results raise the possibility that prediction is an option to be considered in studies for which only reconstructed data are considered.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47238814","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Léo Bosse, J. Lilensten, M. G. Johnsen, N. Gillet, S. Rochat, A. Delboulbé, S. Curaba, Y. Ogawa, Philippe Derverchère, S. Vauclair
It is now established that auroral emissions as measured from ground are polarised. The question of the information given by this polarisation is still to be explored. In this article, we show the results of a coordinated campaign between an optical polarimeter and several ground based instruments, including magnetometers, the EISCAT VHF radar and complementary luminance meters in the visible domain (Ninox). We show that in the E region, the polarisation is a good indicator of the ionospheric currents, velocity and dynamics.
{"title":"The polarisation of auroral emissions: A tracer of the E region ionospheric currents","authors":"Léo Bosse, J. Lilensten, M. G. Johnsen, N. Gillet, S. Rochat, A. Delboulbé, S. Curaba, Y. Ogawa, Philippe Derverchère, S. Vauclair","doi":"10.1051/swsc/2022014","DOIUrl":"https://doi.org/10.1051/swsc/2022014","url":null,"abstract":"It is now established that auroral emissions as measured from ground are polarised. The question of the information given by this polarisation is still to be explored. In this article, we show the results of a coordinated campaign between an optical polarimeter and several ground based instruments, including magnetometers, the EISCAT VHF radar and complementary luminance meters in the visible domain (Ninox). We show that in the E region, the polarisation is a good indicator of the ionospheric currents, velocity and dynamics.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42201105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To improve Thermosphere-Ionosphere modeling during disturbed conditions, data assimilation schemes that can account for the large and fast moving gradients moving through the modeled domain are necessary. We argue that this requires a physics based background model with a non-stationary covariance. An added benefit of using physics based models would be improved forecasting capability over largely persistence based forecasts of empirical models. As a reference implementation, we have developed an ensemble Kalman Filter (enKF) software called Thermosphere Ionosphere Data Assimilation (TIDA) using the physics based Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model as the background. In this paper we present detailed results from experiments during the 2003 Halloween Storm, 27-31 October 2003, under very disturbed ($mathrm{K}_p$ = 9) conditions while assimilating GRACE-A and B, and CHAMP neutral density measurements. TIDA simulates this disturbed period without using the L1 solar wind measurements, which were contaminated by solar energetic protons, by estimating the model drivers from the density measurements. We also briefly present statistical results for two additional storms: September 27 - October 2, 2002 and July 26 - 30, 2004 to show that the improvement in assimilated neutral density specification is not an artifact of the corrupted forcing observations during the 2003 Halloween Storm. By showing statistical results from assimilating one satellite at a time, we show that TIDA produces a coherent global specification for neutral density throughout the storm -- a critical capability in calculating satellite drag and debris collision avoidance for space traffic management.
{"title":"storm time neutral density assimilation in the thermosphere ionosphere with tida","authors":"M. Codrescu, S. Codrescu, M. Fedrizzi","doi":"10.1051/swsc/2022011","DOIUrl":"https://doi.org/10.1051/swsc/2022011","url":null,"abstract":"To improve Thermosphere-Ionosphere modeling during disturbed conditions, data assimilation schemes that can account for the large and fast moving gradients moving through the modeled domain are necessary. We argue that this requires a physics based background model with a non-stationary covariance. An added benefit of using physics based models would be improved forecasting capability over largely persistence based forecasts of empirical models. As a reference implementation, we have developed an ensemble Kalman Filter (enKF) software called Thermosphere Ionosphere Data Assimilation (TIDA) using the physics based Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model as the background. In this paper we present detailed results from experiments during the 2003 Halloween Storm, 27-31 October 2003, under very disturbed ($mathrm{K}_p$ = 9) conditions while assimilating GRACE-A and B, and CHAMP neutral density measurements. TIDA simulates this disturbed period without using the L1 solar wind measurements, which were contaminated by solar energetic protons, by estimating the model drivers from the density measurements. We also briefly present statistical results for two additional storms: September 27 - October 2, 2002 and July 26 - 30, 2004 to show that the improvement in assimilated neutral density specification is not an artifact of the corrupted forcing observations during the 2003 Halloween Storm. By showing statistical results from assimilating one satellite at a time, we show that TIDA produces a coherent global specification for neutral density throughout the storm -- a critical capability in calculating satellite drag and debris collision avoidance for space traffic management.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49291558","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chunhua Jiang, Lehui Wei, T. Yokoyama, Jiyao Xu, Kun Wu, W. Yuan, Jing Liu, Tongxin Liu, Guobin Yang, Zhengyu Zhao
Investigations of upwelling backscatter plumes are mostly from observations of VHF radars. In this study, we report the first observation of upwelling backscatter plumes (backscatter echoes beyond the critical frequency of the F2 layer, foF2) recorded by ionosondes at low latitudes on 13 March, 2015. With a pair of ionosondes (Puer, 22.7o N, 101.05o E, Dip Lat 12.9o N, and Chiang Mai, 18.76o N, 98.93o E, Dip Lat 9.04o N), Swarm satellites flying side-by-side (longitudinal separation of about 1.4°, about 150 km), and an all-sky imager (25o N, 104o E, Dip Lat 15.1o N), the evolution of plasma bubbles is presented in this study. Observations show that ionosonde backscatter plumes originating from a local-scale upwelling could be observed. In addition, this study also reported ionosonde backscatter plumes from other regions with approaching and receding characteristics. Results show that characteristics of backscatter plumes with ionosondes are consistent with observations from VHF radars. It suggests that ionosonde backscatter plumes might be used to study characteristics of upwelling backscatter plumes as well.
对上升流后向散射羽流的研究大多来自甚高频雷达的观测。本文报道了2015年3月13日在低纬度地区首次观测到上升流后向散射羽流(后向散射回波超过F2层的临界频率，foF2)。利用一对离子探空仪(Puer, 22.70 N, 101.050 E，倾角12.90 N, Chiang Mai, 18.76 N, 98.93 E，倾角9.040 N)， Swarm卫星并排飞行(纵距约1.4°，约150 km)，以及一台全天成像仪(25o N, 1040 E，倾角15.10 N)，对等离子体气泡的演化进行了研究。观测表明，可以观测到来自局地尺度上升流的电离空仪后向散射羽流。此外，本研究还报道了来自其他地区的具有接近和后退特征的电离探空仪后向散射羽流。结果表明，利用电离层探空仪观测到的后向散射羽流特征与VHF雷达观测结果基本一致。这表明电离层探测后向散射羽流也可以用于研究上升流后向散射羽流的特征。
{"title":"Upwelling Coherent Backscatter Plumes Observed with Ionosondes in Low-Latitude Region","authors":"Chunhua Jiang, Lehui Wei, T. Yokoyama, Jiyao Xu, Kun Wu, W. Yuan, Jing Liu, Tongxin Liu, Guobin Yang, Zhengyu Zhao","doi":"10.1051/swsc/2022010","DOIUrl":"https://doi.org/10.1051/swsc/2022010","url":null,"abstract":"Investigations of upwelling backscatter plumes are mostly from observations of VHF radars. In this study, we report the first observation of upwelling backscatter plumes (backscatter echoes beyond the critical frequency of the F2 layer, foF2) recorded by ionosondes at low latitudes on 13 March, 2015. With a pair of ionosondes (Puer, 22.7o N, 101.05o E, Dip Lat 12.9o N, and Chiang Mai, 18.76o N, 98.93o E, Dip Lat 9.04o N), Swarm satellites flying side-by-side (longitudinal separation of about 1.4°, about 150 km), and an all-sky imager (25o N, 104o E, Dip Lat 15.1o N), the evolution of plasma bubbles is presented in this study. Observations show that ionosonde backscatter plumes originating from a local-scale upwelling could be observed. In addition, this study also reported ionosonde backscatter plumes from other regions with approaching and receding characteristics. Results show that characteristics of backscatter plumes with ionosondes are consistent with observations from VHF radars. It suggests that ionosonde backscatter plumes might be used to study characteristics of upwelling backscatter plumes as well.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41838130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, we present a new methodology to automatically classify perturbations in the lower ionosphere using GNSS radio occultation (RO) observations collected using Spire’s constellation of CubeSats. This methodology combines signal processing techniques with semi-supervised machine learning by applying spectral clustering in a metric space of wavelet spectra. A “bottom-up” algorithm was applied to extract E layer information directly from Spire’s high-rate (50 Hz) GNSS-RO profiles by subtracting the effect of the F layers. This processing algorithm has been implemented in our ground segment to operationally produce high rate sTEC profiles with a vertical resolution of better than 100 m. The key idea behind the semi-supervised classification is to produce a database of labeled clusters that can be used to classify new unlabeled data by determining which cluster it belongs to. A dataset of more than 12000 GNSS-RO profiles collected in 2019 containing sTEC perturbations is used to find the initial clusters. This dataset is used as a representation of the climatology of ionospheric perturbations, such as MSTIDs and sporadic Es. The wavelet power spectrum (WPS) is computed for these profiles, and a metric space is defined using the Earth mover's distance (EMD) between the WPS. A self-tuning spectral clustering algorithm is used to cluster the profiles in this metric space. These clusters are used as a reference database of perturbations to classify new sTEC profiles by finding the cluster of the closest profile of the clustered dataset in the EMD metric space. This new methodology is used to construct an automated system to monitor ionospheric perturbations on a global scale.
{"title":"Semi-supervised Classification of Lower-Ionospheric Perturbations using GNSS Radio Occultation Observations from Spire Global’s Cubesat Constellation","authors":"G. Savastano, Karl Nordström, M. Angling","doi":"10.1051/swsc/2022009","DOIUrl":"https://doi.org/10.1051/swsc/2022009","url":null,"abstract":"In this study, we present a new methodology to automatically classify perturbations in the lower ionosphere using GNSS radio occultation (RO) observations collected using Spire’s constellation of CubeSats. This methodology combines signal processing techniques with semi-supervised machine learning by applying spectral clustering in a metric space of wavelet spectra. A “bottom-up” algorithm was applied to extract E layer information directly from Spire’s high-rate (50 Hz) GNSS-RO profiles by subtracting the effect of the F layers. This processing algorithm has been implemented in our ground segment to operationally produce high rate sTEC profiles with a vertical resolution of better than 100 m. The key idea behind the semi-supervised classification is to produce a database of labeled clusters that can be used to classify new unlabeled data by determining which cluster it belongs to. A dataset of more than 12000 GNSS-RO profiles collected in 2019 containing sTEC perturbations is used to find the initial clusters. This dataset is used as a representation of the climatology of ionospheric perturbations, such as MSTIDs and sporadic Es. The wavelet power spectrum (WPS) is computed for these profiles, and a metric space is defined using the Earth mover's distance (EMD) between the WPS. A self-tuning spectral clustering algorithm is used to cluster the profiles in this metric space. These clusters are used as a reference database of perturbations to classify new sTEC profiles by finding the cluster of the closest profile of the clustered dataset in the EMD metric space. This new methodology is used to construct an automated system to monitor ionospheric perturbations on a global scale.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47048244","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Edvartsen, V. Maliniemi, H. Nesse Tyssøy, T. Asikainen, S. Hatch
The Mansurov effect is related to the interplanetary magnetic field (IMF) and its ability to modulate the global electric circuit, which is further hypothesized to impact the polar troposphere through cloud generation processes. We investigate the connection between IMF By-component and polar surface pressure by using daily ERA5 reanalysis for geopotential height since 1980. Previous studies produce a 27-day cyclic response during solar cycle 23 which appears to be significant according to conventional statistical tests. However, we show here that when statistical tests appropriate for strongly autocorrelated variables are applied, there is a fairly high probability of obtaining the cyclic response and associated correlation merely by chance. Our results also show that data from three other solar cycles, produce similar cyclic responses as during solar cycle 23, but with seemingly random offset in respect to timing of the signal. By generating random normally distributed noise with different levels of temporal autocorrelation, and using the real IMF By-time series as forcing, we show that the methods applied to support the Mansurov hypothesis up to now, are highly susceptible to random chance, as cyclic patterns always arise as artefacts of the methods. Potential non-stationary behavior of the Mansurov effect makes it difficult to achieve solid statistical significance on decadal time scales. We suggest more research on, e.g., seasonal dependence of the Mansurov effect to understand better potential IMF effects in the atmosphere.
{"title":"The Mansurov effect: Statistical significance and the role of autocorrelation","authors":"J. Edvartsen, V. Maliniemi, H. Nesse Tyssøy, T. Asikainen, S. Hatch","doi":"10.1051/swsc/2022008","DOIUrl":"https://doi.org/10.1051/swsc/2022008","url":null,"abstract":"The Mansurov effect is related to the interplanetary magnetic field (IMF) and its ability to modulate the global electric circuit, which is further hypothesized to impact the polar troposphere through cloud generation processes. We investigate the connection between IMF By-component and polar surface pressure by using daily ERA5 reanalysis for geopotential height since 1980. Previous studies produce a 27-day cyclic response during solar cycle 23 which appears to be significant according to conventional statistical tests. However, we show here that when statistical tests appropriate for strongly autocorrelated variables are applied, there is a fairly high probability of obtaining the cyclic response and associated correlation merely by chance. Our results also show that data from three other solar cycles, produce similar cyclic responses as during solar cycle 23, but with seemingly random offset in respect to timing of the signal. By generating random normally distributed noise with different levels of temporal autocorrelation, and using the real IMF By-time series as forcing, we show that the methods applied to support the Mansurov hypothesis up to now, are highly susceptible to random chance, as cyclic patterns always arise as artefacts of the methods. Potential non-stationary behavior of the Mansurov effect makes it difficult to achieve solid statistical significance on decadal time scales. We suggest more research on, e.g., seasonal dependence of the Mansurov effect to understand better potential IMF effects in the atmosphere.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44137656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
With the data from the Swarm satellite mission, we study the variability of ionospheric plasma parameters for low and high solar activities. We focus on the electron density measured by Swarm and derived parameters, and analyze the variability of these parameters in the contexts of the northern and southern hemispheres, specific latitudinal regions, and the solar activity level. We consider two time-intervals with high solar activity (HSA) from August 2014 to July 2015 and low solar activity (LSA) from January to December 2018. We show that electron density is described mainly by three probability density functions (PDF): exponentiated Weibull, lognormal, and chi distributions. These results with PDF can be applied to modeling or prediction of ionospheric parameters in different regions. The best fit of PDFs was obtained for low and mid latitudes, while at high latitudes and in the polar caps the double-peaked features of the distribution require the fit of multiple PDFs. The electron density distribution at low latitudes follows more a lognormal distribution, while in the high latitude region the chi distribution prevails. Different results were obtained for the Rate of change of Density Index (RODI) with two fitting PDF’s: lognormal or exponentiated Weibull, where the best fits are for high latitudes and polar caps. We demonstrate high variability in the electron density and derived parameters at low latitudes and in the polar caps. Comparing both hemispheres, we obtained higher values of these parameters during the solar minimum in the southern hemisphere at high latitudes and polar caps, while for the northern hemisphere higher values were obtained at low latitudes. The dependence on the satellite’s height was also considered. The main patterns in the diurnal variation of parameters in different regions do not depend on the level of solar activity (which affects only the maximum values). The largest asymmetry between both hemispheres in Ne diurnal distribution was obtained for the polar cap regions. Here a 50% decrease in Ne was observed in the northern hemisphere during HSA in the early morning sector (04-07 Magnetic Local Time) which has not yet been observed in the southern hemisphere. For the first time, such a global statistical characterization of the ionospheric plasma density based on the in situ data is presented.
{"title":"Interhemispheric variability of the electron density and derived parameters by the Swarm satellites during different solar activity","authors":"D. Kotova, Yaqi Jin, W. Miloch","doi":"10.1051/swsc/2022007","DOIUrl":"https://doi.org/10.1051/swsc/2022007","url":null,"abstract":"With the data from the Swarm satellite mission, we study the variability of ionospheric plasma parameters for low and high solar activities. We focus on the electron density measured by Swarm and derived parameters, and analyze the variability of these parameters in the contexts of the northern and southern hemispheres, specific latitudinal regions, and the solar activity level. We consider two time-intervals with high solar activity (HSA) from August 2014 to July 2015 and low solar activity (LSA) from January to December 2018. We show that electron density is described mainly by three probability density functions (PDF): exponentiated Weibull, lognormal, and chi distributions. These results with PDF can be applied to modeling or prediction of ionospheric parameters in different regions. The best fit of PDFs was obtained for low and mid latitudes, while at high latitudes and in the polar caps the double-peaked features of the distribution require the fit of multiple PDFs. The electron density distribution at low latitudes follows more a lognormal distribution, while in the high latitude region the chi distribution prevails. Different results were obtained for the Rate of change of Density Index (RODI) with two fitting PDF’s: lognormal or exponentiated Weibull, where the best fits are for high latitudes and polar caps. We demonstrate high variability in the electron density and derived parameters at low latitudes and in the polar caps. Comparing both hemispheres, we obtained higher values of these parameters during the solar minimum in the southern hemisphere at high latitudes and polar caps, while for the northern hemisphere higher values were obtained at low latitudes. The dependence on the satellite’s height was also considered. The main patterns in the diurnal variation of parameters in different regions do not depend on the level of solar activity (which affects only the maximum values). The largest asymmetry between both hemispheres in Ne diurnal distribution was obtained for the polar cap regions. Here a 50% decrease in Ne was observed in the northern hemisphere during HSA in the early morning sector (04-07 Magnetic Local Time) which has not yet been observed in the southern hemisphere. For the first time, such a global statistical characterization of the ionospheric plasma density based on the in situ data is presented.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47889327","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Patrick Mungufeni, Y. Migoya-Orué, M. Tshimangadzo, G. Omondi
This study attempts to improve estimation of ionospheric electron density profiles over Korea and adjacent areas by employing classical Kalman filtering technique to assimilate Total Electron Content (TEC) data from various sources into the NeQuick model. Successive corrections method was applied to spread the effect of TEC data assimilation at a given location to others that lacked TEC observations. In order to reveal that the assimilation results emulate the complex ionospheric changes during geomagnetic storms, the selected study days included both quiet (Kp ≤ 3) and disturbed geomagnetic conditions in the year 2015. The results showed that assimilation of TEC data derived from ground-based GPS receivers can improve the root mean squared error (RMSE) associated with the NeQuick model estimation of ionospheric parameters by ≥ 56 %. The improvement of RMSE achieved by assimilating TEC data that were measured using ionosondes was ~50 %. The assimilation of TEC observations made by the COSMIC radio occultation technique yielded results that depicted RMSE improvement of > 10 %. The assimilation of TEC data measured by GPS receiver onboard Low Earth Orbiting satellites yielded results that revealed deterioration of RMSE. This outcome might be due to either the fact that the receivers are on moving platforms and these dynamics might have not been accounted for during TEC computation or limitation of the assimilation process. Validation of our assimilation results with global ionosphere TEC data maps as processed at the center for orbit determination in Europe (CODE) revealed that both depicted similar TEC changes, showing response to a geomagnetic storm.
{"title":"Application of Classical Kalman filtering technique in assimilation of multiple data types to NeQuick model","authors":"Patrick Mungufeni, Y. Migoya-Orué, M. Tshimangadzo, G. Omondi","doi":"10.1051/swsc/2022006","DOIUrl":"https://doi.org/10.1051/swsc/2022006","url":null,"abstract":"This study attempts to improve estimation of ionospheric electron density profiles over Korea and adjacent areas by employing classical Kalman filtering technique to assimilate Total Electron Content (TEC) data from various sources into the NeQuick model. Successive corrections method was applied to spread the effect of TEC data assimilation at a given location to others that lacked TEC observations. In order to reveal that the assimilation results emulate the complex ionospheric changes during geomagnetic storms, the selected study days included both quiet (Kp ≤ 3) and disturbed geomagnetic conditions in the year 2015. The results showed that assimilation of TEC data derived from ground-based GPS receivers can improve the root mean squared error (RMSE) associated with the NeQuick model estimation of ionospheric parameters by ≥ 56 %. The improvement of RMSE achieved by assimilating TEC data that were measured using ionosondes was ~50 %. The assimilation of TEC observations made by the COSMIC radio occultation technique yielded results that depicted RMSE improvement of > 10 %. The assimilation of TEC data measured by GPS receiver onboard Low Earth Orbiting satellites yielded results that revealed deterioration of RMSE. This outcome might be due to either the fact that the receivers are on moving platforms and these dynamics might have not been accounted for during TEC computation or limitation of the assimilation process. Validation of our assimilation results with global ionosphere TEC data maps as processed at the center for orbit determination in Europe (CODE) revealed that both depicted similar TEC changes, showing response to a geomagnetic storm.","PeriodicalId":17034,"journal":{"name":"Journal of Space Weather and Space Climate","volume":"1 1","pages":""},"PeriodicalIF":3.3,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"58023880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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