The new Sunspot Number: assembling all corrections

The Sunspot Number, created by R.Wolf in 1849, provides a direct long-term record of solar activity from 1700 to the present. In spite of its central role in multiple studies of the solar dynamo and of the past Sun-Earth relations, it was never submitted to a global critical revision. However, various discrepancies with other solar indices recently motivated a full re-calibration of this series. Based on various diagnostics and corrections established in the framework of several Sunspot Number Workshops and described in Clette et al. 2014, we assembled all corrections in order to produce a new standard version of this reference time series. In this paper, we explain the three main corrections and the criteria used to choose a final optimal version of each correction factor or function, given the available information and published analyses. We then discuss the good agreement obtained with the Group sunspot Number derived from a recent reconstruction. Among the implications emerging from this re-calibrated series, we also discuss the absence of a rising secular trend in the newly-determined solar cycle amplitudes, also in relation with contradictory indications derived from cosmogenic radionuclides. As conclusion, we introduce the new version management scheme now implemented at the World Data Center - SILSO, which reflects a major conceptual transition: beyond the re-scaled numbers, this first revision of the Sunspot Number also transforms the former locked data archive into a living observational series open to future improvements

The revised Brussels-Locarno Sunspot Number (1981-2015)

In 1981, the production of the international Sunspot Number moved from the Z\"{u}rich Observatory to the Royal Observatory of Belgium, marking a very important transition in the history of the Sunspot Number. Those recent decades are particularly important for linking recent modern solar indices and fluxes and the past Sunspot Number series. However, large variations have been recently identified in the scale of the Sunspot Number between 1981 and the present. Here, we reconstruct a new average Sunspot Number series $S_N$ using long-duration stations between 1981 and 2015. We also extend this reconstruction using long-time series from 35 stations over 1945-2015, which includes the 1981 transition. In both reconstructions, we also derive a parallel Group Number series $G_N$. Our results confirm the variable trends of the Locarno pilot station. We also verify the scale of the resulting 1981-2015 correction factor relative to the preceding period 1945--1980. By comparing the new $S_N$ and $G_N$ series, we find that a constant quadratic relation exists between those two indices. This proxy relation leads to a fully constant and cycle-independent $S_N/G_N$ ratio over cycles 19 to 23, with the exception of cycle 24. We find a very good agreement between our reconstructed $G_N$ and the new "backbone" Group Number but inhomogeneities in the original Group Number as well as the $F_{10.7}$ radio flux and the American sunspot number $R_a$. This analysis opens the way to the implementation of a more advanced method for producing the Sunspot Number in the future. In particular, we identify the existence of distinct subsets of observing stations sharing very similar personal k factors, which may be a key element for building a future multi-station reference in place of the past single pilot station.Comment: 33 pages, 23 figures, 2 table

Can we trace very cold dust from its emission alone ?

Context. Dust is a good tracer of cold dark clouds but its column density is difficult to quantify. Aims. We want to check whether the far-infrared and submillimeter high-resolution data from Herschel SPIRE and PACS cameras combined with ground-based telescope bolometers allow us to retrieve the whole dust content of cold dark clouds. Methods. We compare far-infrared and submillimeter emission across L183 to the 8 $\mu$m absorption map from Spitzer data and fit modified blackbody functions towards three different positions. Results. We find that none of the Herschel SPIRE channels follow the cold dust profile seen in absorption. Even the ground-based submillimeter telescope observations, although more closely following the absorption profile, cannot help to characterize the cold dust without external information such as the dust column density itself. The difference in dust opacity can reach up to a factor of 3 in prestellar cores of high extinction. Conclusions. In dark clouds, the amount of very cold dust cannot be measured from its emission alone. In particular, studies of dark clouds based only on Herschel data can miss a large fraction of the dust content. This has an impact on core and filament density profiles, masse and stability estimates.Comment: Letter to A&A (accepted for publication). must be viewed with ACROBAT READER for full enhancement. Otherwise, check images in Appendix

Nucleate boiling in a flat grooved heat pipe

International audienceThe present paper is devoted to an experimental study aiming at determining the thermal behavior of a flat plate heat pipe (FPHP) with micro grooves and at focusing especially on the effect of boiling in the grooves. The FPHP is hermetically sealed on its upper face with a transparent plate for observations. Experimental results obtained with methanol are presented. Nucleate boiling in the grooves is observed for relatively small heat fluxes (3 Wcm−2). The presence of nucleate boiling in the grooves improves the thermal performance of the flat heat pipe, and it must be emphasized that it does not constitute an operation limit as it is generally stated. The dry out of the evaporator is observed for heat fluxes much higher than the heat flux of onset of nucleate boiling. The results obtained for different filling ratios show the influence of this parameter that has to be optimized to improve the performance of the device

Network housekeeping with stretched low voltage limits

This paper looks into solutions a grid operator has to cope with, taking into account high penetration of high penetration of renewable sources and new loads in the LV grid. Next to that it answers the following main research questions: - what will happen when the low voltage limits will be stretched from ±10% (current value) to e.g. ±15% (with or without time limitation)? - what must a DSO do to realise such a change (technical, legal, ….)? To answer these questions a literature study, simulation, tests and extensive surveys amongst key stakeholders were performed. Finally, recommendations and alternatives are proposed towards the community of DSOs following EN50160

Integration of control loops in coupled field circuit model to study magnetic devices supplied by power electronic converter and their control

In this paper, we present a method to take into account the feedback control in software developed from coupled field circuit models. The implementation of control loops is done in a software which is able to simulate electromagnetic devices associated with power electronic circuits having a time dependent topology. The control strategy is implemented in a discrete‐time version and can manage all controllable electronic switches by means of different electric or magnetic quantities calculated during the simulation (flux, currents, voltages, …). Electrical systems involving magnetic devices, power electronic converters and their control devices can be simulated in presence of phenomena such as eddy currents or saturation of the magnetic materials

Synthesis and modelling of an electrostatic induction motor

This paper deals with a new way of synthesis and modelling of electrostatic induction micromotors by means of duality rules from the magnetic induction machine. An electromechanical model based on this method is given. Then, a computational procedure based on a general lumped parameter model and an electric field calculation code, has been developed so as to simulate the dynamic working of these actuators. A comparison is made between the computation results and the model results. Satisfactory agreement between theory and simulation is obtained in most respect

Nonparametric monitoring of sunspot number observations: a case study

Solar activity is an important driver of long-term climate trends and must be accounted for in climate models. Unfortunately, direct measurements of this quantity over long periods do not exist. The only observation related to solar activity whose records reach back to the seventeenth century are sunspots. Surprisingly, determining the number of sunspots consistently over time has remained until today a challenging statistical problem. It arises from the need of consolidating data from multiple observing stations around the world in a context of low signal-to-noise ratios, non-stationarity, missing data, non-standard distributions and many kinds of errors. The data from some stations experience therefore severe and various deviations over time. In this paper, we propose the first systematic and thorough statistical approach for monitoring these complex and important series. It consists of three steps essential for successful treatment of the data: smoothing on multiple timescales, monitoring using block bootstrap calibrated CUSUM charts and classifying of out-of-control situations by support vector techniques. This approach allows us to detect a wide range of anomalies (such as sudden jumps or more progressive drifts), unseen in previous analyses. It helps us to identify the causes of major deviations, which are often observer or equipment related. Their detection and identification will contribute to improve future observations. Their elimination or correction in past data will lead to a more precise reconstruction of the world reference index for solar activity: the International Sunspot Number.Comment: 27 pages (without appendices), 6 figure

Une méthode générale pour modé1iser les convertisseurs statiques associés à des dispositifs magnétiques

In this paper a general method for modelling power electronics circuits associated with electromagnetic devices is presented. This model is based on the simultaneous resolution of the circuit equations and the field equations in electromagnetic devices and on a general solution for taking into account the switching of semiconductors. This method allows to consider phenomena such as eddy currents and saturation of magnetic materials in the electromagnetic devices associated with static converters. Dans cet article, nous présentons une méthode générale pour simuler les ensembles constitués de convertisseurs statiques associés à des structures magnétiques. Cette solution est basée sur la résolution simultanée des équations de type circuit du convertisseur couplées aux équations du champ dans la structure magnétique et sur une méthode générale pour gérer l'état des interrupteurs du circuit. Il est alors possible de considérer des phénomènes tels que les courants de Foucault ou la saturation des matériaux dans des structures associées à des convertisseurs