Automated identification of coronal holes from synoptic EUV maps

Coronal holes (CH) are regions of open magnetic field lines in the solar corona and the source of fast solar wind. Understanding the evolution of coronal holes is critical for solar magnetism as well as for accurate space weather forecasts. We study here the extreme ultraviolet (EUV) synoptic maps at three wavelengths (195A/193A, 171A and 304A) measured by Solar and Heliospheric Observatory/Extreme Ultraviolet Imaging Telescope (SOHO/EIT) and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) instruments. The two datasets are first homogenized by scaling the SDO/AIA data to the SOHO/EIT level by means of histogram equalization. We then develop a novel automated method to identify CHs from these homogenized maps by determining the intensity threshold of CH regions separately for each synoptic map. This is done by identifying the best location and size of an image segment, which optimally contains portions of coronal holes and the surrounding quiet Sun allowing us to detect the momentary intensity threshold. Our method is thus able to adjust itself to the changing scale size of coronal holes and to temporally varying intensities. To make full use of the information in the three wavelengths we construct, a composite CH distribution, which is more robust than distributions based on one wavelength. Using the composite CH dataset we discuss the temporal evolution of CHs during the solar cycles 23 and 24

Prediction of even and odd sunspot cycles

Here we study the prediction of even and odd numbered sunspot cycles separately, thereby taking into account the Hale cyclicity of solar magnetism. We first show that the temporal evolution and shape of all sunspot cycles are extremely well described by a simple parameterized mathematical expression. We find that the parameters describing even sunspot cycles can be predicted quite accurately using the sunspot number 41 months prior to sunspot minimum as a precursor. We find that the parameters of the odd cycles can be best predicted with maximum geomagnetic aa index close to fall equinox within a 3-year window preceding the sunspot minimum. We use the found precursors to predict all previous sunspot cycles and evaluate the performance with a cross-validation methodology, which indicates that each past cycle is very accurately predicted. For the coming sunspot cycle 25 we predict an amplitude of 171 +/- 23 and the end of the cycle in September 2029 +/- 1.9 years. We are also able to make a rough prediction for cycle 26 based on the predicted cycle 25. While the uncertainty for the cycle amplitude is large we estimate that the cycle 26 will most likely be stronger than cycle 25. These results suggest an increasing trend in solar activity for the next decades.Comment: This manuscript has been accepted for publication in the Journal of Space Weather and Space Climate (JSWSC). An earlier version of this manuscript has been posted as a pre-print in Research Square https://www.researchsquare.com/article/rs-2377445/v

Undulate : A framework for data-driven software engineering enabling soft computing

Context. Especially web-facing software systems enable the collection of usage data at a massive scale. At the same time, the scale and scope of software processes have grown substantively. Automated tools are needed to increase the speed and quality of controlling software processes. The usage data has great potential as a driver for software processes. However, research still lacks constructs for collecting, refining and utilising usage data in controlling software processes.Objective. The objective of this paper is to introduce a framework for data-driven software engineering. The UNDULATE framework covers generating, collecting and utilising usage data from software processes and business processes supported by the software produced. In addition, we define the concepts and process of extreme continuous experimentation as an exemplar of a software engineering process.Method. We derive requirements for the framework from the research literature, with a focus on papers inspired by practical problems. In addition, we apply a multilevel modelling language to describe the concepts related to extreme continuous experimentation.Results. We introduce the UNDULATE framework and give requirements and provide an overview of the processes of collecting usage data, augmenting it with additional dimensional data, aggregating the data along the dimensions and computing different metrics based on the data and other metrics.Conclusions. The paper represents significant steps inspired by previous research and practical insight towards standardised processes for data-driven software engineering, enabling the application of soft computing and other methods based on artificial intelligence.Peer reviewe

Magnetic Storms During the Space Age : Occurrence and Relation to Varying Solar Activity

AbstractWe study the occurrence of magnetic storms in space age (1957–2021) using Dst and Dxt indices. We find 2,526/2,743 magnetic storms in the Dxt/Dst index, out of which 45% are weak, 40% moderate, 12% intense and 3% major storms. Occurrence of storms in space age follows the slow decrease of sunspot activity and the related change in solar magnetic structure. We quantify the sunspot—coronal mass ejection (CME) storm relation in the five cycles of space age. We explain how the varying solar activity changes the structure of the heliospheric current sheet (HCS), and how this affects the high-speed solar wind stream (HSS)/corotating interaction region (CIR) storms. Space age started with a record number of storms in 1957–1960, with roughly one storm per week. Solar polar fields attained their maximum in cycle 22, which led to an exceptionally thin HCS, and a space age record of large HSS/CIR storms in 1990s. In the minimum of cycle 23, for the only time in space age, CME storm occurrence reduced below that predicted by sunspots. Weak sunspot activity since cycle 23 has weakened solar polar fields and widened the HCS, which has decreased the occurrence of large and moderate HSS/CIR storms. Because of a wide HCS, the Earth has spent 50% of its time in slow solar wind since cycle 23. The wide HCS has also made large and moderate HSS/CIR storms occur in the early declining phase in recent cycles, while in the more active cycles 20–22 they occurred in the late declining phase.Abstract We study the occurrence of magnetic storms in space age (1957–2021) using Dst and Dxt indices. We find 2,526/2,743 magnetic storms in the Dxt/Dst index, out of which 45% are weak, 40% moderate, 12% intense and 3% major storms. Occurrence of storms in space age follows the slow decrease of sunspot activity and the related change in solar magnetic structure. We quantify the sunspot—coronal mass ejection (CME) storm relation in the five cycles of space age. We explain how the varying solar activity changes the structure of the heliospheric current sheet (HCS), and how this affects the high-speed solar wind stream (HSS)/corotating interaction region (CIR) storms. Space age started with a record number of storms in 1957–1960, with roughly one storm per week. Solar polar fields attained their maximum in cycle 22, which led to an exceptionally thin HCS, and a space age record of large HSS/CIR storms in 1990s. In the minimum of cycle 23, for the only time in space age, CME storm occurrence reduced below that predicted by sunspots. Weak sunspot activity since cycle 23 has weakened solar polar fields and widened the HCS, which has decreased the occurrence of large and moderate HSS/CIR storms. Because of a wide HCS, the Earth has spent 50% of its time in slow solar wind since cycle 23. The wide HCS has also made large and moderate HSS/CIR storms occur in the early declining phase in recent cycles, while in the more active cycles 20–22 they occurred in the late declining phase

A Conceptual Modelling Approach to Software Variability

Variability is the ability of a system to be efficiently extended, changed, customised or configured for use in a particular context. Increasing amounts of variability are required of software systems. The number of possible variants of a software system may become very large, essentially infinite. Efficient methods for modelling and reasoning about software variability are needed and numerous such languages have been developed. Most of these languages either lack a solid conceptual foundation or a rigorous formal semantics, or both. In this dissertation, three novel software variability modelling languages, KOALISH, FORFAMEL and KUMBANG, which synthesises KOALISH and FORFAMEL, are developed. The languages are based on concepts found relevant to modelling software variability in scientific literature and practice, namely features and software architecture. They synthesise and clarify the concepts defined in a number of previous languages. Ideas first developed in product configuration research for modelling variability in non-software products are elaborated and integrated into the languages. A formal semantics is given for the languages by translation to weight constraint rule language (WCRL). One of the goals of this dissertation is to enable the representation of software variability knowledge at different levels of abstraction in a uniform manner, preferably using an existing conceptual modelling language with a formal semantics. Unfortunately, it turns out that no existing language meets these requirements. Consequently, a novel conceptual modelling language, NIVEL, with the necessary capabilities is developed in this dissertation. The modelling concepts of NIVEL are not based on software variability. Consequently, NIVEL can be applied in domains other than software variability and is hence generic and contributes to the theory of conceptual modelling. A formal semantics enabling automated, decidable reasoning is given for NIVEL by translation to WCRL. NIVEL is used to give an alternative definition of KUMBANG. The alternative definition is more compact and easily understandable than the original one. Major parts of the semantics of KUMBANG are captured by the semantics of NIVEL. The definition of KUMBANG in terms of a generic modelling language also brings software variability modelling closer to other forms of modelling, thus making software variability modelling less of an isolated discipline

Avoin korkeakoulu opiskelijoiden arvioimana

With the views held by students as the basis, the article looks into the functionality of the Open University as system of study, from the aspect of vocational, degree-oriented, and avocational studies. In addition, it looks at the Open University’s role as an institution offering general education, at the effect of the system of study on the realization of educational and social equality, and at the regional significance of the Open University. The results indicate that degree-studies are being used more and more as vocational further education. The problem is that studies are often seen as representing a mere formal vocational further qualification. Ali in all, it is assumed that the Open University is fairly well able to fulfil the expectations of students regarding the system of study.Artikkeli tarkastelee opiskelijoiden mielipiteiden pohjalta avoimen korkeakoulun toimivuutta opintojärjestelmänä, ammatillisen, tutkintotavoitteisen ja harrastuspainotteisen opiskelun näkökulmista. Lisäksi käsitellään avoimen korkeakoulun merkitystä yleissivistävän koulutuksen antajana, opintojärjestelmän vaikutusta koulutuksellisen tai yhteiskunnallisen tasa-arvon toteutumiseen ja avoimen korkeakoulun alueellista merkitystä. Tulosten mukaan arvosanaopetusta käytetään yhä enemmän ammatillisena täydennyskoulutuksena. Ongelmana on, että opinnot koetaan usein pelkäksi muodolliseksi ammatilliseksi lisäpätevöitymiseksi. Myös opintojen tutkintotavoitteisuus ja niiden merkitys osana muuta opiskelua on huomattava. Kokonaisuudessaan voi arvioida, että avoin korkeakoulu pystyy verraten hyvin täyttämään opiskelijoiden opintojärjestelmään kohdistuneet odotukset. Artikkeli perustuu Tampereen yliopistossa tehtyyn aikuiskasvatuksen syventävien opintojen tutkielmaan

Straight outta photosphere: Open solar flux without coronal modeling

Abstract Context: The open solar flux, that is, the total magnetic flux escaping the Sun, is one of the most important parameters connecting solar activity to the Earth. The open solar flux is commonly estimated from photospheric magnetic field measurements by making model assumptions about the solar corona. However, the question in which way the open solar flux is directly related to the distribution of the photospheric magnetic field is still partly unknown. Aims: We aim to reconstruct the open solar flux directly from the photospheric magnetic fields without making any assumptions about the corona and without using coronal hole observations, for instance. Methods: We modified an earlier vector sum method by taking magnetic field polarities into account and applied the method to the synoptic magnetograms of six instruments to determine the open solar flux from solar cycles 21–24. Results: The modified vector sum method produces a vector of the global solar magnetic field whose magnitude closely matches the open solar flux from the potential field source surface (PFSS) model both by the absolute scale and the overall time evolution for each of the six magnetograms. The latitude of this vector follows the Hale cycle by always pointing toward the dominantly positive-polarity hemisphere, and its longitude coincides with the location of the main coronal holes of the McIntosh Archive. We find multi-year periods during which the longitude of the vector slowly drifts or stays rather stationary in the Carrington frame. These periods are punctuated by times when the longitude moves rapidly in the Carrington frame. By comparing the magnitude of this vector to the open solar flux calculated from the PFSS model with different source surface heights, we find that the best match is produced with a source surface height Rss = 2.4 − 2.5 R⊙.Abstract Context: The open solar flux, that is, the total magnetic flux escaping the Sun, is one of the most important parameters connecting solar activity to the Earth. The open solar flux is commonly estimated from photospheric magnetic field measurements by making model assumptions about the solar corona. However, the question in which way the open solar flux is directly related to the distribution of the photospheric magnetic field is still partly unknown. Aims: We aim to reconstruct the open solar flux directly from the photospheric magnetic fields without making any assumptions about the corona and without using coronal hole observations, for instance. Methods: We modified an earlier vector sum method by taking magnetic field polarities into account and applied the method to the synoptic magnetograms of six instruments to determine the open solar flux from solar cycles 21–24. Results: The modified vector sum method produces a vector of the global solar magnetic field whose magnitude closely matches the open solar flux from the potential field source surface (PFSS) model both by the absolute scale and the overall time evolution for each of the six magnetograms. The latitude of this vector follows the Hale cycle by always pointing toward the dominantly positive-polarity hemisphere, and its longitude coincides with the location of the main coronal holes of the McIntosh Archive. We find multi-year periods during which the longitude of the vector slowly drifts or stays rather stationary in the Carrington frame. These periods are punctuated by times when the longitude moves rapidly in the Carrington frame. By comparing the magnitude of this vector to the open solar flux calculated from the PFSS model with different source surface heights, we find that the best match is produced with a source surface height Rss = 2.4 − 2.5 R⊙

Decadal variability in the Northern Hemisphere winter circulation : effects of different solar and terrestrial drivers

AbstractNorthern Hemisphere winter circulation is affected by both solar and terrestrial forcings. El-Niño events and volcanic eruptions have been shown to produce a negative and a positive North Atlantic Oscillation (NAO) signature, respectively. Recent studies show a positive NAO signature related to both geomagnetic activity (proxy for solar wind driven particle precipitation) and sunspot activity (proxy for solar irradiance). Here the relative role of these four different drivers on the Northern Hemisphere wintertime circulation is studied using a statistical analysis of observational and reanalysis data during 1868–2014. The phase of the Quasi-Biennial Oscillation (QBO) is used to study driver signals in different stratospheric conditions. Moreover, the effects are separated for early/mid- and late winter. Our findings suggest a stratospheric mediation of the ENSO signal to the Atlantic side, which is delayed and modulated by the QBO unlike the signal in the Pacific side. The positive NAO by volcanic activity is preferentially obtained in the westerly QBO. We also find a substantial QBO modulation for geomagnetic activity and late winter sunspot activity, which favours a stratospheric pathway and the top-down mechanisms. However, signal in the North Pacific produced by early/mid-winter sunspot activity remain rather similar in different QBO phases and supports a direct forcing from the troposphere by the bottom-up sunspot mechanism.Abstract Northern Hemisphere winter circulation is affected by both solar and terrestrial forcings. El-Niño events and volcanic eruptions have been shown to produce a negative and a positive North Atlantic Oscillation (NAO) signature, respectively. Recent studies show a positive NAO signature related to both geomagnetic activity (proxy for solar wind driven particle precipitation) and sunspot activity (proxy for solar irradiance). Here the relative role of these four different drivers on the Northern Hemisphere wintertime circulation is studied using a statistical analysis of observational and reanalysis data during 1868–2014. The phase of the Quasi-Biennial Oscillation (QBO) is used to study driver signals in different stratospheric conditions. Moreover, the effects are separated for early/mid- and late winter. Our findings suggest a stratospheric mediation of the ENSO signal to the Atlantic side, which is delayed and modulated by the QBO unlike the signal in the Pacific side. The positive NAO by volcanic activity is preferentially obtained in the westerly QBO. We also find a substantial QBO modulation for geomagnetic activity and late winter sunspot activity, which favours a stratospheric pathway and the top-down mechanisms. However, signal in the North Pacific produced by early/mid-winter sunspot activity remain rather similar in different QBO phases and supports a direct forcing from the troposphere by the bottom-up sunspot mechanism

Planetary Waves Controlling the Effect of Energetic Electron Precipitation on the Northern Polar Vortex

AbstractEnergetic electron precipitation (EEP) forms ozone-depleting nitrogen and hydrogen oxides in the high-latitude middle and upper atmosphere, leading to ozone destruction and temperature enhancement that can strengthen the winter polar vortex. This EEP effect on polar vortex depends on quasi-biennial oscillation and sudden stratospheric warmings, which earlier studies relate to planetary waves. We study here the possible modulation of the EEP effect by planetary waves. We perform a principal component analysis of the vertical component of Eliassen-Palm flux (EP flux) to examine the latitudinal pattern of planetary waves. We use a multilinear regression analysis to estimate the responses of zonal wind and EP flux divergence to EEP in the northern winter stratosphere by keeping the two leading principal components of vertical EP flux as controlling factors. We find that the EEP strengthens the polar vortex most systematically when planetary wave propagation is enhanced at mid-latitudes but reduced at polar latitudes.Abstract Energetic electron precipitation (EEP) forms ozone-depleting nitrogen and hydrogen oxides in the high-latitude middle and upper atmosphere, leading to ozone destruction and temperature enhancement that can strengthen the winter polar vortex. This EEP effect on polar vortex depends on quasi-biennial oscillation and sudden stratospheric warmings, which earlier studies relate to planetary waves. We study here the possible modulation of the EEP effect by planetary waves. We perform a principal component analysis of the vertical component of Eliassen-Palm flux (EP flux) to examine the latitudinal pattern of planetary waves. We use a multilinear regression analysis to estimate the responses of zonal wind and EP flux divergence to EEP in the northern winter stratosphere by keeping the two leading principal components of vertical EP flux as controlling factors. We find that the EEP strengthens the polar vortex most systematically when planetary wave propagation is enhanced at mid-latitudes but reduced at polar latitudes