PC Index Research Articles

Comparison of modeling of the polar cap absorption effect with observations at the AARI ground-based network

An elliptical model of cutoff for solar cosmic rays (SCR) at high latitudes has been calculated for SCR events and geomagnetic storms that occurred in February, March, and September 2014, June 2015, and September 2017 in order to predict the polar cap absorption (PCA) effect. The prediction is compared with observations of the PCA effect at the AARI network of six ionosondes, located in the north of Russia in a wide range of longitudes from 30 to 170 and magnetic latitudes from 56 to 64. We examine the dependence of the cutoff latitude on the magnetic storm strength, as well as the effect of additional ionization of the dayside and nightside ionosphere by SCR protons and electrons. The model demonstrates a satisfactory statistical accuracy up to 0.83 for the PCA prediction. We discuss prospects for further improvement of the elliptical model, such as consideration of the impact of SCRs of higher energies and inclusion of the PC index of energy flux into the polar cap.

Сравнение моделирования эффекта поглощения в полярной шапке с наблюдениями на сети станций ААНИИ

An elliptical model of cutoff for solar cosmic rays (SCR) at high latitudes has been calculated for SCR events and geomagnetic storms that occurred in February, March, and September 2014, June 2015, and September 2017 in order to predict the polar cap absorption (PCA) effect. The prediction is compared with observations of the PCA effect at the AARI network of six ionosondes, located in the north of Russia in a wide range of longitudes from 30 to 170 and magnetic latitudes from 56 to 64. We examine the dependence of the cutoff latitude on the magnetic storm strength, as well as the effect of additional ionization of the dayside and nightside ionosphere by SCR protons and electrons. The model demonstrates a satisfactory statistical accuracy up to 0.83 for the PCA prediction. We discuss prospects for further improvement of the elliptical model, such as consideration of the impact of SCRs of higher energies and inclusion of the PC index of energy flux into the polar cap.

Different origins of magnetic disturbances during substorm growth and expansion phases and insufficiency of the AL index as their sole measure

The paper examines the relationship between the PC index, characterizing the solar wind energy input into the magnetosphere, and the AL index, characterizing the magnetic substorm intensity for the expansion phase of isolated substorms recorded in 1998–2017. Magnetic disturbances in the course of the expansion phase are produced by the DP11 current system with a powerful westward electrojet disposed in the midnight auroral zone. It is generally accepted that this electrojet is generated by the “substorm current wedge” system of fieldaligned currents (SCW FAC) providing closure of the magnetotail plasma sheet currents through the auroral ionosphere. As this takes place, magnetic disturbances in the course of the substorm growth phase are produced by the DP12 current system with westward and eastward electrojets located, correspondingly, in the morning and evening sectors of the auroral zone, with the electrojets generated by the R1/R2 FAC system operating in the inner (closed) magnetosphere. The intensity of R1 currents is determined by the “coupling function” EKL, which represents the optimal combination of all geoeffective solar wind parameters affecting the magnetosphere. The DP2 magnetic disturbances generated by the R1 FAC system in polar caps forms the basis for estimating the PC index, which strongly follows the EKL field changes and correlates well with the development of magnetic substorms. Analyses performed in AARI revealed the principally distinctive character of the relationships between the PC index and AL index in the course of the substorm growth (DP12 disturbances) and explosive (DP11 disturbances) phases. The DP12 disturbances, generated by FAC systems in the closed magnetosphere, are developed in strong relation to the PC index. The DP11 disturbances, generated by the SCW FAC system, related to the magnetotail plasma sheet, show quite irregular character of relationship between the PC and AL values: the sudden jumps of the substorm intensity (ALpeaks) might occur, time and again, at any value of the PC index and with quite different delay times relative to sudden substorm onset. It means that the processes in the tail plasma sheet, leading to the formation of a “substorm current wedge” are determined by the state of the magnetotail plasma sheet itself. The solar wind influence (evaluated by the PC index) affects but does not control the processes in the magnetotail, unlike those in the inner magnetosphere. It should be noted in this connection that the intensity of magnetic DP12 and DP11 disturbances, observed in the course of the substorm growth and explosive phases, is estimated by a single AL index, in spite of the different origin of these disturbances (R1/R2 and SCW FAC systems). It is necessary to employ two separate indices characterizing DP12 and DP11 disturbances in order to allow for the effects of the solar wind on the processes in the inner magnetosphere and in the magnetotail.

Resilience of regional container port network: based on projection correlation and dynamic spatial Markov Chain

ABSTRACT Ports are interconnected by shipping routes within the global logistics network. Shocks and risks stemming from financial crises, epidemics, ecology, and so on have prompted shifts in cross-border labor division towards regional cooperation, reflecting an ‘anti-globalization’ trend. Despite these dynamics, few studies have analyzed the spatial structure and dynamic evolution of resilience within regional container port network. Addressing this gap, this study considers spatial and dynamic attributes to identify influential factors of resilience and introduces the concept of spatial lag-multidimensional resistance (SL-MR) to strengthen the understanding and cognition of regional container port network resilience (RCPNR). By ports in Tianjin and Hebei, China, it constructs a dynamic spatial Markov chain (DSMC) based on the projection correlation (PC index) to dissect transition trajectories amid financial crises and other conflicts. The findings indicate: (1) The regional container port network often experiences a low-level path dependence like ‘poverty trap.’ (2) Hierarchical spatial lags significantly influence the transition probability of container port network resilience degradation, with regional port relationships being unidirectional rather than cooperative. (3) The impact of the 2008 financial crisis and the COVID-19 pandemic on regional port resilience varies, serving as key determinants in shaping diverse resilience types.

PC Index as a Ground-Based Indicator of the Solar Wind Energy Incoming into the Magnetosphere: (2) Relation of PC Index to Magnetic Disturbances

PC Index as a Ground-Based Indicator of the Solar Wind Energy Incoming into the Magnetosphere: (2) Relation of PC Index to Magnetic Disturbances

Physical reasons for regular discrepancies in values of the PCN and PCS indices characterizing magnetic activity in the northern and southern polar caps

PC index characterizes magnetic activity generated in polar caps by R1 FAC system related to the solar wind electric field EKL. The PC index is calculated separately by data on magnetic disturbance values δF at stations Thule (PCN) and Vostok (PCS) with use of the “unified PC derivation method” taking into account statistically justified relationships between values of EKL and δF at these stations. Nevertheless, discrepancy between PCN and PCS indices is regularly observed: the value of difference ΔPC = PCN-PCS demonstrates the obvious seasonal variation and strongly increases in periods of high magnetic activity, the ΔPC values being the highest (>1 mV/m) in epochs of solar activity maximum and being the lowest (<0.5 mV/m) in the quiet periods. Analysis of discrepancies ΔPC, carried out by data on the 1-min definitive PCN and PCS indices for 22 year (1997–2022), showed that difference between the daily PCN and PCS values is caused by influence of the azimuthal BY IMF component, which generates the specific BY FAC system with reverse polarity of field-aligned currents in the northern and southern hemispheres. Effect of these currents, which is opposite in northern and southern polar caps, critically distorts the regular ionospheric current systems related to EKL field influence, resulting in discrepancy of corresponding PCN and PCS indices.

Imaging ovarian cancer – from baseline characteristics to high-risk image factors

BackgroundImaging ovarian cancer (OC) includes evaluating peritoneal carcinomatosis (PC) and enlarged cardio phrenic lymph nodes (CPLN) by computed tomography (CT), and thorough evaluation is tedious work. A “CT short score” with high-risk CT parameters might be a more pragmatic approach, but it is not known if such a short score associates with aggressive OC subtypes and impaired OC survival. Further, it is not known if certain established OC risk factors are linked to high-risk CT-findings which would be important in image evaluation. Herein, we investigate a CT short score and its relation to baseline characteristics, OC subtypes, and survival.MethodsThe Malmö Diet and Cancer Study is a prospective cohort that included 17,035 women (1991–1996). Baseline characteristics and tumor information on 159 OC and information on OC specific survival (last follow-up, 2017-12-31) was registered. A CT short score (CPLN and PC-index (PCI) in seven regions) was registered and associations with clinical stage [stage I vs. advanced stage (II-IV), histological type/grade (high grade serous and endometrioid vs. other subtypes], and OC-specific survival were analyzed with logistic and Cox regression, respectively. Parity and menopausal status were analyzed in relation to short score and PCI.ResultsThere was an association between higher short score and advanced clinical stage (adjusted OR 2.76 (1.42—5.38)), adjusted for age at diagnosis and histological type/grade. Higher short score was associated with impaired OC specific survival (adjusted HR 1.17 (1.01—1.35)), adjusted for age at diagnosis, histological type/grade, and clinical stage. There were no significant associations between parity, menopausal status, and short score/PCI.ConclusionsCT short score was significantly associated with advanced clinical stages and impaired OC survival. A pragmatic approach (based on CT) to evaluate high risk image findings in OC could help reduce radiologists’ workload and at the same time provide structured reports to surgeons and oncologists involved in OC care.

Incomplete cytoreductive surgery for appendiceal and colorectal peritoneal carcinomatosis: Characteristics and outcomes of an overlooked group.

Complete cytoreductive surgery (CRS) may prolong survival for selected patients with peritoneal carcinomatosis from colorectal cancer (CRC). However, there is a paucity of data on outcomes following incomplete procedures. Patients with incomplete CRS for well-differentiated (WD) and moderate/poorly-differentiated (M/PD) appendiceal cancer, right and left CRC were identified at a single tertiary center (2008-2021). Of 109 patients, 10% were WD and 51% M/PD appendiceal cancers, and 16% right and 23% left CRC. There were no differences in gender, BMI (mean = 27), ASA score, previous abdominal surgery (72%), and extent of CRS. The PC Index differed between appendiceal and colorectal cancers (mean = 27 vs. 17, p < 0.01). Overall, the perioperative outcomes were similar among the groups, with 15% experiencing complications. Postoperatively, 61% received chemotherapy, and 51% required ≥1 subsequent procedure. The 1 and 3-year survival for the WD, M/PD, right and left CRC subgroups were 100%, 67%, 44%, 51%, and 88%, 17%, 12%, and 23%, respectively (p = 0.02). Incomplete CRS was associated with significant morbidity and number of subsequent palliative procedures. Prognosis correlated with histologic subtype; WD appendiceal cancer patients having superior outcomes, while those with right sided CRC the worst survival. These data may help guiding expectations in the setting of incomplete procedures.

PC index as a ground-based indicator of the solar wind energy incoming into the magnetosphere: (1) relation of PC index to the solar wind electric field EKL

The polar cap magnetic activity PC index was approved by IAGA as a proxy for energy that enters into the magnetosphere during solar wind-magnetosphere coupling (IAGA Resolutions, 2013; IAGA Resolution, 2021). The paper summarizes experimental results attesting the validity of this PC index essence. The following issues are examined: the PC index derivation method, making allowance for regular and irregular variations of ionospheric conductivity; relationships between the PC index and solar wind electric field (EKL) and factors controlling response of PC index to the EKL field alterations; relation of PC index to the magnetospheric field-aligned currents (FAC) and to solar wind dynamic pressure pulses (Pdyn). The PC index alterations in course of 23/24 solar activity cycles have been analyzed in relation to various solar wind parameters and the conclusion was made that linear link between the PC index and solar wind electric field EKL remained valid irrespective of solar activity cycle. New ideas concerning (1) the nature of occasional differences between the PC indices in summer and winter polar caps and (2) two simultaneously acting mechanisms of the solar wind influence on the magnetosphere (Dungey and Tverskoy concepts) are discussed, as a result of the PC index application. It is emphasized that the ground-based PC index ensures a permanent on-line information on geoefficiency of the solar wind impact on the magnetosphere and, correspondingly, on the varying geophysical situation.

Reply to Comment by Stauning on “The PC Index Variations During 23/24 Solar Cycles: Relation to Solar Wind Parameters and Magnetic Disturbances”

AbstractThe polar cap magnetic activity index (PC) was approved by IAGA as an index characterizing the solar wind energy input into the magnetosphere. Relation of the PC index to solar wind parameters and solar activity during 23/24 solar cycles has been studied in paper (Troshichev et al., 2021, https://doi.org/10.1029/2020JA028491). The paper was commented by Dr. Stauning, who states that results obtained in the study are based on erroneous data presented on web site http://pcindex.org. According to Dr. Stauning, the following invalidities served as a reason for this assertion: incorrect determination of quiet daily curve (QDC), taken as reference level for counting the PC index value, and incorrect QDC amplitudes, incorrect yearly average values of PC index (and EKL field), incorrect methods of the analysis. In our answer we argue the correctness of our analysis and resulted conclusions.

Comment on “The PC Index Variations During 23/24 Solar Cycles: Relation to Solar Wind Parameters and Magnetic Disturbances” by Troschichev et al.

AbstractExamination of the contribution from O. A. Troshichev, S. Dolgacheva, N. A. Stepanov, and D. A. Sormakov: “The PC index variations during 23/24 solar cycles: relation to solar wind parameters and magnetic disturbances,” https://doi.org/10.1029/2020JA028491 has disclosed inconsistencies in the applied methods and errors in the calculated values. Some of the discrepancies reported in the present commentary affect directly the illustrations presented in their contribution while other possible errors may not be apparent since the use of relative values in their presentation makes thorough assessments difficult.

Invariability of relationships between the solar wind electric field EKL and the magnetic activity indices PC, AL and Dst

The daily values of the EKL field and indices of magnetic activity PC, AL and Dst were used to verify stability of relationships between these parameters in course of 23rd and 24th solar cycles. The results of analysis demonstrate that the mean level of correlation between the EKL field and PC index remains in range R = 0.85–0.90 over 24 years. During the solar maximum epochs (2008, 2015) the correlation between EKL and PC reduced down to R = 0.75, the decrease being related to solar protons events (SPE), which strongly affect the ionospheric conductivity in polar caps. In the course of both cycles the daily AL index well correlated with PC index (R = 0.93) and with EKL field (R = 0.83); correlation of daily Dst index with PC and EKL values was much worse (R = 0.72 and 0.64, correspondingly), the correlation being independent of solar activity epochs and cycles. The PC indices in northern (PCN) and southern (PCS) indices hemispheres demonstrate the evident seasonal variation; the PCsummer index is commonly larger than the PCwinter index, but PCwinter index better correlates with EKL field. The conclusion is made that relationships between the EKL field, PC index, and the magnetic disturbance indices AL and Dst remained valid in course of 23rd and 24th solar cycles and, therefore, the calibrating coefficients, determining these relationships, are not affected by solar activity.

The Use of Invalid Polar Cap South (PCS) Indices in Publications

AbstractPolar Cap (PC) indices, PCN North based on magnetic observations from Qaanaaq (THL) in Greenland and PCS South based on magnetic data from Vostok in Antarctica, are very useful indices for studies of solar wind‐magnetosphere interactions and for space weather monitoring and forecasts. PCN indices are issued from the Danish Space Research Institute (DTU Space) while PCS indices are issued from the Arctic and Antarctic Research Institute (AARI) in St Petersburg. Unfortunately, series of invalid PCS values have been provided from AARI and used in a number of publications issued since the PC index concept was endorsed by the International Association of Geomagnetism and Aeronomy (IAGA) in 2013. In spite of the disclosure of the failure in the PCS indices in 2018, publishing at the IAGA‐supported International Service of Geomagnetic Indices of the invalid indices has continued up to now (2022). The present contribution defines the invalidating features of the PCS indices in question, conveys examples, and discusses the applications in peer‐reviewed publications.

Rainfall and Temperature Variations over Burkina Faso: Possible Influence of Geomagnetic Activity, Solar Activity and Associated Energies from 1975 to 2020

This study investigates climatic parameters (rainfall, and temperature) over Burkina Faso and the possible role of solar activity and its induced energies. Through morphological investigations, we analyzed solar activity indices (sunspot number, IMF, PC index, Cosmic rays) over the last three solar cycles (1975-2020). Results about interplanetary heating show that joule heating is well correlated with the dynamic pressure of the solar plasma. Climate parameters (rainfall, Temperature) variabilities are modulated by disturbances in solar activity: 1) quiet solar characterized by a drop in solar plasma’s parameters is associated with important cloud cover and consequently bring important rainfall which chills terrestrial atmosphere, 2) active solar characterized by important input energy is associated with weak incident cosmic ray consequently with low cloudiness which brings warming. Thus, the possible natural link can be suggested between solar activity and climatic parameters even if it is not the only factor of global warming.

Reconstructing Substorms via Historical Data Mining: Is It Really Feasible?

AbstractThe evolution of the low‐latitude magnetosphere over the substorm cycle is reconstructed based on a new high‐resolution 3D representation of the magnetic field and nearest‐neighbor data mining. The study covers radial distances 2.5–25 and employs a record‐large pool of spacecraft data taken during 1995–2019. The magnetospheric state is quantified by four indices, representing the ground geomagnetic activity and its temporal trends in the entire range of geomagnetic latitude: the SuperMAG SMR, the midlatitude positive bay MPB, the auroral SML, and the polar cap PC index. The developed technique has been tested on specific substorm events, with the results presented in the form of 5‐min cadence diagrams and animations of the magnetic field line configurations and electric current distributions. In all the analyzed events, the initial intensification and radial expansion of the inner tail current is accompanied by a gradual stretching of the magnetic field, followed by its sudden collapse, dramatic depletion of the current beyond , and a large‐scale dipolarization of the field around the time of MPB peak, after which the system recovers and tends to its pre‐substorm state.

Areas for the connectivity of Chaco peccary (Catagonus wagneri) populations at the southern limit of their distribution in the Argentine Chaco / Áreas para a conectividade de populações de pecari do Chaco (Catagonus wagneri) no limite sul de sua distribuição no Chaco Argentino

The area of geographical distribution of mammal populations in the Argentine Chaco ecoregion is being increasingly reduced and this is mainly due to the progressive destruction of habitats. In this context, several species have been affected, among which is the endemic Catagonus wagneri (Tayassuidae), currently classified as "endangered" and with a trend of population decline. In this work, the predictions estimated by three algorithms were compared to establish the potential geographic distribution of this species at the southern limit of its natural distribution. Priority locations for landscape connectivity were identified by comparing intrinsic variations in the PC index based on data classification methods. With the use of foot transects, trap cameras and surveys with the local population, the presence of chacoan peccary was recorded on 25 occasions. From the GLM, Random Forest and Maxent algorithms (mean AUC 0.74), a reference model was obtained. Using it as an input and the PC index, the variation in the importance of the connectivity surfaces of the landscape was evaluated using three classification methods: quantile, equal interval and natural breaks. The consensus model (SDM) occupies 55,674 km2 of Argentina, representing 10% of the Chaco Seco ecoregion. The distribution occupies not only forest ecosystems, but also environments with less tree coverage. Coefficients of variation of 170% were recorded between the classification methods for the number of patches of classes 9 and 10 of the priority habitat for landscape connectivity. The SDM shows a fragmented distribution in line with the Chaco's land use change process.The results suggest a great variability of the PC index depending on the method of classifying data in class intervals, an aspect that was not discussed in previous studies.

Efficacy of botulinum-A for nocturnal bruxism pain and the occurrence of bruxism events: a meta-analysis and systematic review

The purpose of this study was to explore the treatment efficacy of botulinum-A (BTX-A) in nocturnal bruxism. Five electronic databases (PubMed, Web of Science, Cochrane, Embase and Clinical Trials) were searched to identify related randomised controlled trials up to September 1, 2020. Five evaluation indices were extracted, namely, the pain at rest and at chewing (PR and PC), the number of bruxism events (NBE) and the self-assessment by patients (SA), to assess the treatment efficacy of BTX-A in bruxism. All data analyses were conducted using Review Manager (Version 5.3; The Cochrane Collaboration, London, United Kingdom). Six studies were included in this review. The sample was composed of 148 participants. Compared with the placebo group, the BTX-A group showed the significantly improved the PR index scores (MD, 1.16 cm; 95%CI, 0.65 to 1.67 cm; p < 0.00001), slightly improved the PC index scores (SMD, 0.25; 95%CI -0.14 to 0.64; p = 0.21), and the NBEs were significantly decreased in the before-injection group compared with that in the after-injection group (MD, 1.72; 95%CI, 0.60 to 2.85; p = 0.003). The results of this study suggest that BTX-A possesses significant therapeutic efficiency for the relief of pain and events of bruxism. However, whether the events of bruxism would recur or rebound after botulinum toxin injection needs more follow-up clinical evidence.

How well do the S2S models predict intraseasonal wintertime surface air temperature over mid-high-latitude Eurasia?

The leading modes of intraseasonal surface air temperature (SAT) over mid-high-latitude Eurasia (MHLE) in boreal winter are captured with the observational 10–60-day SAT anomaly during 1979–2016 by an empirical orthogonal function (EOF) analysis. Each cycle of the southeastward-propagating intraseasonal oscillation (ISO) of SAT is divided into eight phases formed by the first two principal components (PC1 and PC2). Reforecast data from five operational models in the Sub-seasonal to Seasonal (S2S) Project are utilized to assess the prediction skill of the intraseasonal SAT over the MHLE based on the PC index. It is revealed that the upper limit of the useful forecast skill ranges from ~ 10 to ~ 20 days and the models display a better score for target strong cases, although they underestimate the amplitude of the intraseasonal signal. Generally, a higher prediction skill appears in target phase 3, while a lower score exists in target phase 6. The phase-dependent feature of prediction skill is found to be associated with the phase-dependence of amplitude bias and phase angle error, indicating the importance of skillfully predicting ISO amplitude and propagation speed. On the basis of PC index, the ECMWF model can skillfully predict the evolution of an ISO event up to ~ 20 days in advance. Further assessment of potential predictability reveals a 5-day skill gap for ECMWF model, which needs to be overcome by reducing forecast errors for the current prediction scheme. In a nutshell, the real-time PC index can be an efficient method to capture and predict the ISO signal over MHLE, providing possibilities for improving sub-seasonal forecast skill of wintertime intraseasonal SAT anomaly. Meanwhile, more efforts are still needed for the improvements of dynamical prediction systems, to facilitate more accurate and longer-lead predictions of intraseasonal SAT signal over MHLE during boreal winter.

Space Weather Monitoring on Ground-based Magnetic Observations (PC Index)

Space Weather Monitoring on Ground-based Magnetic Observations (PC Index)

О необходимости адаптации модели авроральных высыпаний частиц OVATION Prime (2010)

The need to reparametrize the OVATION Prime (2010) empirical auroral precipitation model using the Russian polar cap index (PC index) is considered. For this purpose, the integrated auroral power of particle precipitation obtained from the Polar satellite data for the period from December 1996 to June 1998 is compared with the PC index and the Newell’s coupling function. The analysis revealed that the PC index at the time delays up to 5–20 minutes correlates with the magnitude of auroral power much better (the correlation coefficient R ~ 0.76–0.87) than the Newell’s coupling function (R ~ 0.46–0.82). Thus, for the purpose of nowcasting the zone of active particle precipitation, the PC index showed much higher scores, although the predicting abilities of the Newell’s coupling function for the time delays of more than 20 minutes remain the best.