The ESPERTA (Empirical model for Solar Proton Event Real Time Alert) forecast tool has a Probability of Detection (POD) of 63% for all >10 MeV events with proton peak intensity ≥10 pfu (i.e., ≥S1 ...events, S1 referring to minor storms on the NOAA Solar Radiation Storms scale), from 1995 to 2014 with a false alarm rate (FAR) of 38% and a median (minimum) warning time (WT) of ∼4.8 (0.4) hr. The NOAA space weather scale includes four additional categories: moderate (S2), strong (S3), severe (S4), and extreme (S5). As S1 events have only minor impacts on HF radio propagation in the polar regions, the effective threshold for significant space radiation effects appears to be the S2 level (100 pfu), above which both biological and space operation impacts are observed along with increased effects on HF propagation in the polar regions. We modified the ESPERTA model to predict ≥S2 events and obtained a POD of 75% (41/55) and an FAR of 24% (13/54) for the 1995-2014 interval with a median (minimum) WT of ∼1.7 (0.2) hr based on predictions made at the time of the S1 threshold crossing. The improved performance of ESPERTA for ≥S2 events is a reflection of the big flare syndrome, which postulates that the measures of the various manifestations of eruptive solar flares increase as one considers increasingly larger events.
In this work, we present a case study of the relevant timescales responsible for coupling between the changes of the solar wind and interplanetary magnetic field (IMF) conditions and the ...magnetospheric dynamics during the St. Patrick's Day Geomagnetic Storms in 2013 and 2015. We investigate the behavior of the interplanetary magnetic field (IMF) component Bz, the Perreault‐Akasofu coupling function and the AE, AL, AU, SYM‐H, and ASY‐H geomagnetic indices at different timescales by using the empirical mode decomposition (EMD) method and the delayed mutual information (DMI). The EMD, indeed, allows to extract the intrinsic oscillations (modes) present into the different data sets, while the DMI, which provides a measure of the total amount of the linear and nonlinear shared information (correlation degree), allows to investigate the relevance of the different timescales in the solar wind‐magnetosphere coupling. The results clearly indicate the existence of a relevant timescale separation in the solar wind‐magnetosphere coupling. Indeed, while fluctuations at long timescales (τ > 200 min) show a large degree of correlation between solar wind parameters and magnetospheric dynamics proxies, at short timescales (τ < 200 min) this direct link is missing. This result suggests that fluctuations at timescales lower than 200 min, although triggered by changes of the interplanetary conditions, are mainly dominated by internal processes and are not directly driven by solar wind/IMF. Conversely, the magnetospheric dynamics in response to the solar wind/IMF driver at timescales longer than 200 min resembles the changes observed in the solar wind/IMF features. Finally, these results can be useful for Space Weather forecasting.
Key Points
Novel analysis approaches clearly indicate the existence of a relevant timescale separation in the solar wind‐magnetosphere coupling
Short‐timescales (200 min) fluctuations, triggered by changes of the interplanetary conditions, are mainly related to internal processes
The magnetospheric dynamics at timescales longer than 200 min resembles the changes observed in the solar wind/IMF features
Properties of Solar Wind Structures at Mercury's Orbit Diego, P.; Piersanti, M.; Laurenza, M. ...
Journal of geophysical research. Space physics,
September 2020, 2020-09-00, 20200901, Letnik:
125, Številka:
9
Journal Article
Recenzirano
Mercury's environment is characterized by a high variability and strength of the solar forcing. Its magnetosphere is completely reconfigured even for small changes in the interplanetary magnetic ...field and the solar wind (SW) dynamic pressure. Different configurations are due to occurrence of different structures in the SW. Among them, high speed streams from coronal holes, magnetic clouds, and noncompressive density enhancement have been analyzed to better characterize the Hermean conditions, which might be expected during the ongoing BepiColombo mission. Helios 1 and 2 mission data collected between 0.29 and 0.47 AU have been used to perform a statistical analysis of these SW structures. The numerical results reported in the paper, as well as the probability densities displayed in the maps, give more precise indications when associated to a rigorous SW structures selection. The occurrence rate along solar cycle together with the average features of each class of SW structures are useful information for Space Weather topics. Results from the same analysis performed at 1 AU have been used to further verification of the radial behavior of the SW parameters.
Key Points
Properties of the different solar wind structures between 0.29 and 0.47 AU are compared
Alfvénic and sonic Mach number typical values between 0.3 and 1 AU for different solar wind structures are identified
Highest solar wind dynamic pressures at Mercury orbit, ~15 to 30 nPa, occur during noncompressive density enhancements
To evaluate the solar energetic proton (SEP) forecast model of Laurenza et al., here termed ESPERTA, we computed the input parameters (soft X-ray (SXR) fluence and ∼1 MHz radio fluence) for all ≥M2 ...SXR flares from 2006 to 2014. This database is outside the 1995-2005 interval on which ESPERTA was developed. To assess the difference in the general level of activity between these two intervals, we compared the occurrence frequencies of SXR flares and SEP events for the first six years of cycles 23 (1996 September-2002 September) and 24 (2008 December-2014 December). We found a reduction of SXR flares and SEP events of 40% and 46%, respectively, in the latter period. Moreover, the numbers of ≥M2 flares with high values of SXR and ∼1 MHz fluences (>0.1 J m−2 and >6 × 105 sfu × minute, respectively) are both reduced by ∼30%. A somewhat larger percentage decrease of these two parameters (∼40% versus ∼30%) is obtained for the 2006-2014 interval in comparison with 1995-2005. Despite these differences, ESPERTA performance was comparable for the two intervals. For the 2006-2014 interval, ESPERTA had a probability of detection (POD) of 59% (19/32) and a false alarm rate (FAR) of 30% (8/27), versus a POD = 63% (47/75) and an FAR = 42% (34/81) for the original 1995-2005 data set. In addition, for the 2006-2014 interval the median (average) warning time was estimated to be ∼2 hr (∼7 hr), versus ∼6 hr (∼9 hr), for the 1995-2005 data set.
Introduction La télémédecine s’étend à tous les domaines de la santé, dont la cicatrisation des plaies chroniques. Les plaies de pied diabétique et les ulcères veineux représentent une part ...importante de ces plaies. Matériels et méthodes Ce poster présente la description préliminaire du projet Européen FP7-ICT-2011-8 qui vise à élaborer un système de soins pour plaies chroniques intitulé SWAN-iCare. Résultats De septembre 2012 à septembre 2016, un consortium de cliniciens et de scientifiques va élaborer un nouveau système de prise en charge des plaies chroniques : le système SWAN-iCare, dédié principalement aux plaies de pied diabétique et aux ulcères veineux. Ce dispositif reposera sur un traitement par pression négative réalisable au domicile du patient, couplé à un monitoring à distance de la cicatrisation à partir : – de capteurs situés au voisinage de la plaie pour mesurer certaines caractéristiques physico-chimiques de l’exsudat impactant sur la cicatrisation (pH, taux de protéases…). – de mesure de la pression plantaire pour les plaies de pied diabétique ou de la dorsiflexion pour les ulcères veineux, ou encore d’un suivi de l’oxygénation de la plaie ou de la glycémie capillaire. Le but est d’offrir pour des plaies dites « difficile à cicatriser » un outil de monitoring pour le centre de cicatrisation en charge du patient, afin d’améliorer la prise en charge globale de ces plaies de pronostic incertain. Les résultats présentés ici tracent les grandes lignes de ce projet, dans les limites du respect de la propriété intellectuelle. Conclusion Dans un avenir proche, on peut s’attendre au développement du traitement par pression négative pour les plaies chroniques, associé à des systèmes de monitoring à distance reposant sur des capteurs pour différentes caractéristiques des plaies concernées.
Introduction La télémédecine touche tous les domaines de la santé, notamment la cicatrisation des plaies chroniques. Méthodes Description préliminaire du projet européen FP7-ICT-2011-8 visant à ...élaborer un système de soins pour plaies chroniques intitulé SWAN-iCare (Smart Wearable and Autonomous Negative Pressure Device for wound monitoring and therapy). Résultats De septembre 2012 à septembre 2016, un consortium de cliniciens et de scientifiques va élaborer un nouveau système de prise en charge des plaies chroniques dédié principalement aux plaies de pied diabétique et aux ulcères veineux. Ce système reposera sur un traitement par pression négative réalisable à domicile, couplé à un monitoring à distance de la cicatrisation à partir :. – de capteurs situés au voisinage de la plaie pour mesurer certaines caractéristiques physico-chimiques de l’exsudat impactant sur la cicatrisation (pH, taux de protéases…) ; – de mesure de la pression plantaire pour les plaies de pied diabétique ou de la dorsiflexion pour les ulcères veineux, ou encore d’un suivi de l’oxygénation de la plaie. Le but est d’offrir pour des plaies dites « difficile à cicatriser » un outil de monitoring pour le centre de cicatrisation en charge du patient, afin d’améliorer la prise en charge globale de ces plaies de pronostic incertain. Les résultats présentés ici tracent les grandes lignes de ce projet, dans les limites du respect de la propriété intellectuelle. Conclusion Dans un futur proche, on s’attend au développement du traitement par pression négative, associé à des systèmes de monitoring à distance des plaies chroniques.
Aims. The revised dataset of sunspot and group numbers (released by WDC-SILSO) and the sunspot number reconstruction based on dendrochronologically dated radiocarbon concentrations have been analyzed ...to provide a deeper characterization of the solar activity main periodicities and to investigate the role of the Gleissberg and Suess cycles in the grand minima occurrence. Methods. Empirical mode decomposition (EMD) has been used to isolate the time behavior of the different solar activity periodicities. A general consistency among the results from all the analyzed datasets verifies the reliability of the EMD approach. Results. The analysis on the revised sunspot data indicates that the highest energy content is associated with the Schwabe cycle. In correspondence with the grand minima (Maunder and Dalton), the frequency of this cycle changes to longer timescales of ~14 yr. The Gleissberg and Suess cycles, with timescales of 60−120 yr and ~ 200−300 yr, respectively, represent the most energetic contribution to sunspot number reconstruction records and are both found to be characterized by multiple scales of oscillation. The grand minima generation and the origin of the two expected distinct types of grand minima, Maunder and longer Spörer-like, are naturally explained through the EMD approach. We found that the grand minima sequence is produced by the coupling between Gleissberg and Suess cycles, the latter being responsible for the most intense and longest Spörer-like minima (with typical duration longer than 80 yr). Finally, we identified a non-solar component, characterized by a very long scale oscillation of ~ 7000 yr, and the Hallstatt cycle (~ 2000 yr), likely due to the solar activity. Conclusions. These results provide new observational constraints on the properties of the solar cycle periodicities, the grand minima generation, and thus the long-term behavior of the solar dynamo.
Incorporation of kinetic effects such as Landau damping into a fluid framework was pioneered by Hammett and Perkins, by obtaining closures of the fluid hierarchy, where the gyrotropic heat flux ...fluctuations or the deviation of the fourth-order gyrotropic fluid moment are expressed through lower-order fluid moments. To obtain a closure of a fluid model expanded around a bi-Maxwellian distribution function, the usual plasma dispersion function Z(ζ) that appears in kinetic theory or the associated plasma response function R(ζ)=1+ζZ(ζ) has to be approximated with a suitable Padé approximant in such a way that the closure is valid for all ζ values. Such closures are rare, and the original closures of Hammett and Perkins are often employed. Here we present a complete mapping of all plausible Landau fluid closures that can be constructed at the level of fourth-order moments in the gyrotropic limit and we identify the most precise closures. Furthermore, by considering 1D closures at higher-order moments, we show that it is possible to reproduce linear Landau damping in the fluid framework to any desired precision, thus showing convergence of the fluid and collisionless kinetic descriptions.
The spatio-temporal dynamics of the solar magnetic field has been investigated by using NSO/Kitt Peak magnetic synoptic maps covering the period 1976 August-2003 September. The field radial ...component, for each heliographic latitude, has been decomposed in intrinsic mode functions through the Empirical Mode Decomposition in order to investigate the time evolution of the various characteristic oscillating modes at different latitudes. The same technique has also been applied on synoptic maps of the meridional and east-west components, which were derived from the observed line-of-sight projection of the field by using the differential rotation. Results obtained for the ~22 yr cycle, related to the polarity inversions of the large-scale dipolar field, show an antisymmetric behavior with respect to the equator in all the field components and a marked poleward flux migration in the radial and meridional components (from about -35degrees and +35degrees in the southern and northern hemispheres, respectively). The quasi-biennial oscillations (QBOs) are also identified as a fundamental timescale of variability of the magnetic field and associated with poleward magnetic flux migration from low latitudes around the maximum and descending phase of the solar cycle. Moreover, signs of an equatorward drift, at a ~2 yr rate, seem to appear in the radial and toroidal components. Hence, the QBO patterns suggest a link to a dynamo action. Finally, the high-frequency component of the magnetic field, at timescales less than 1 yr, provides the most energetic contribution and it is associated with the outbreaks of the bipolar regions on the solar surface.
The time variability of the cosmic-ray (CR) intensity at three different rigidities has been analyzed through the empirical mode decomposition technique for the period 1964-2004. Apart from the ~11 ...yr cycle, quasi-biennial oscillations (QBOs) have been detected as a prominent scale of variability in CR data, as well as in the heliomagnetic field magnitude at 1 AU and in the sunspot area. The superposition of the ~11 yr and QBO contributions reproduces the general features of the CR modulation, such as most of the step-like decreases and the Gnevyshev Gap phenomenon. A significant correlation has also been found between QBOs of the heliospheric magnetic field and the CR intensity during even solar activity cycles, suggesting that the former are responsible for step-like decreases in CR modulation, probably dominated by the particle diffusion/convection in such periods. In contrast, during odd-numbered cycles, no significant correlation is found. This could be explained with an enhanced drift effect also during the solar maximum or a greater influence of merged interaction regions at great heliocentric distances during odd cycles. Moreover, the QBOs of CR data are delayed with respect to sunspot activity, the lag being shorter for A > 0 periods of even cycles (~1-4 months) than for A < 0 periods of odd cycles (~7-9 months); we suggest that solar QBOs also affect the recovery of the CR intensity after the solar activity maximum.
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