Nowcasting Solar Energetic Particle Events Using Principal Component Analysis

We perform a principal component analysis (PCA) on a set of six solar variables (i.e. width/size () and velocity () of a coronal mass ejection, logarithm of the solar flare (SF) magnitude (), SF longitude (), duration (), and rise time ()). We classify the solar energetic particle (SEP) event radiation impact (in terms of the National Oceanic and Atmospheric Administration scales) with respect to the characteristics of their parent solar events. We further attempt to infer the possible prediction of SEP events. In our analysis, we use 126 SEP events with complete solar information, from 1997 to 2013. Each SEP event is a vector in six dimensions (corresponding to the six solar variables used in this work). The PCA transforms the input vectors into a set of orthogonal components. By mapping the characteristics of the parent solar events, a new base defined by these components led to the classification of the SEP events. We furthermore applied logistic regression analysis with single, as well as multiple explanatory variables, in order to develop a new index () for the nowcasting (short-term forecasting) of SEP events. We tested several different schemes for and validated our findings with the implementation of categorical scores (probability of detection (POD) and false-alarm rate (FAR)). We present and interpret the obtained scores, and discuss the strengths and weaknesses of the different implementations. We show that holds prognosis potential for SEP events. The maximum POD achieved is 77.78% and the relative FAR is 40.96%

Magnetic Flux of EUV Arcade and Dimming Regions as a Relevant Parameter for Early Diagnostics of Solar Eruptions - Sources of Non-Recurrent Geomagnetic Storms and Forbush Decreases

This study aims at the early diagnostics of geoeffectiveness of coronal mass ejections (CMEs) from quantitative parameters of the accompanying EUV dimming and arcade events. We study events of the 23th solar cycle, in which major non-recurrent geomagnetic storms (GMS) with Dst <-100 nT are sufficiently reliably identified with their solar sources in the central part of the disk. Using the SOHO/EIT 195 A images and MDI magnetograms, we select significant dimming and arcade areas and calculate summarized unsigned magnetic fluxes in these regions at the photospheric level. The high relevance of this eruption parameter is displayed by its pronounced correlation with the Forbush decrease (FD) magnitude, which, unlike GMSs, does not depend on the sign of the Bz component but is determined by global characteristics of ICMEs. Correlations with the same magnetic flux in the solar source region are found for the GMS intensity (at the first step, without taking into account factors determining the Bz component near the Earth), as well as for the temporal intervals between the solar eruptions and the GMS onset and peak times. The larger the magnetic flux, the stronger the FD and GMS intensities are and the shorter the ICME transit time is. The revealed correlations indicate that the main quantitative characteristics of major non-recurrent space weather disturbances are largely determined by measurable parameters of solar eruptions, in particular, by the magnetic flux in dimming areas and arcades, and can be tentatively estimated in advance with a lead time from 1 to 4 days. For GMS intensity, the revealed dependencies allow one to estimate a possible value, which can be expected if the Bz component is negative.Comment: 27 pages, 5 figures. Accepted for publication in Solar Physic

Review of solar energetic particle models

Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they are the product of a broad set of physical processes from the corona out through the extent of the heliosphere, and provide insight into processes of particle acceleration and transport that are widely applicable in astrophysics. From the operations perspective, SEP events pose a radiation hazard for aviation, electronics in space, and human space exploration, in particular for missions outside of the Earth’s protective magnetosphere including to the Moon and Mars. Thus, it is critical to improve the scientific understanding of SEP events and use this understanding to develop and improve SEP forecasting capabilities to support operations. Many SEP models exist or are in development using a wide variety of approaches and with differing goals. These include computationally intensive physics-based models, fast and light empirical models, machine learning-based models, and mixed-model approaches. The aim of this paper is to summarize all of the SEP models currently developed in the scientific community, including a description of model approach, inputs and outputs, free parameters, and any published validations or comparisons with data.</p

Dependence of Forbush-decrease characteristics on parameters of solar eruptions

Abstract. We analyze relations between characteristics of an extended ensemble of Forbush decreases (FDs) caused by CMEs from the central zone of the solar disk during the 23 rd solar cycle, on the one hand, and such solar eruption parameter as a summarized unsigned magnetic flux of CME-associated EUV dimmings and arcades, on the other hand. This eruption parameter is shown to have a pronounced direct correlation with the FD magnitude and a conspicuous reverse correlation with the ICME transit time from the Sun to the Earth. The revealed correlations indicate that main quantitative characteristics of major non-recurrent FDs (and geomagnetic storms as well) are largely determined by parameters of solar eruptions, in particular such as the summarized magnetic flux of dimmings and arcades. Introduction Non-recurrent Forbush decreases (FDs) and geomagnetic storms (GMSs) are caused by coronal mass ejections (CMEs) and their interplanetary counterparts ICMEs We develop a new approach to the early diagnostics of solar eruptions in which quantitative characteristics of such large-scale CME manifestations as dimmings and post-eruption (PE) arcades observed in the extreme ultraviolet (EUV) range are used as key parameters instead of the projected CME speed and shape I

An Extended Study of the Precursory Signs of Forbush Decreases: New Findings over the Years 2008 – 2016

In spite of the fact that the current Solar Cycle 24 is close to its end now, it is a less active Solar Cycle, during its time period (2008 – 2016) and a lot of Forbush decreases of cosmic ray intensity with rigidity 10 GV and amplitude greater than 2% were recorded by the ground-based neutron monitors. Among these events, the ones associated with sudden geomagnetic storm commencements (SSCs) and presenting a first harmonic of cosmic ray anisotropy greater than 0.8% were examined. Cosmic ray data recorded at the neutron monitor stations were obtained from the European high resolution neutron monitor database, while the Forbush decreases, accompanied by their characteristics were accessed from the updated Database of the Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN). Solar, interplanetary and geomagnetic characteristic parameters of each event separately have been studied in detail and analyzed. It was shown through the usage of the “ring of neutron monitor stations” method that, in some cases, precursory signals before the main phase of the event appeared. After an extended study of the Forbush decreases precursors during the examined period, the appearance of pre-decreases and/or pre-increases of the cosmic ray intensity before the beginning of the events, acting as precursory signals, were identified in almost half of the cases studied. In combination with other parameters, their common features are discussed, with the purpose of monitoring and possibly forecasting the space-weather conditions. © 2019, Springer Nature B.V

Precursory Signs of Large Forbush Decreases

The study of space-weather effects and more specifically Forbush decreases of the cosmic-ray intensity depends on space and ground measurements. Very often Forbush decreases and geomagnetic storms are accompanied by pre-increases and/or pre-decreases manifested in cosmic-ray behavior, known as precursory signs. These cosmic-ray intensity variations do not coincide with the shock arrival but begin well before (up to 24 hours) the onset of the main event. In this study a group of large Forbush decreases with amplitude ≥ 4% was examined for precursors. According to the helio-longitude of the solar source, the events were separated into three categories: western (21 ∘≤ helio-longitude ≤ 60∘), eastern (− 60 ∘≤ helio-longitude ≤ − 21 ∘), and central (− 20 ∘≤ helio-longitude ≤ 20 ∘). The selected events cover 1967 – 2017. The analysis of the Forbush decreases and the plotting of the asymptotic longitudinal cosmic-ray distribution diagrams were based on the “Global Survey Method” and the “Ring of Stations” method, respectively. Data on solar flares, solar-wind speed, interplanetary magnetic field, and geomagnetic indices (Kp and Dst) were also used. The results show the clear signs of precursors in a significant number of events. © 2021, The Author(s), under exclusive licence to Springer Nature B.V

Interplanetary Coronal Mass Ejections as the Driver of Non-recurrent Forbush Decreases

Interplanetary coronal mass ejections (ICMEs) are the counterparts of coronal mass ejections (CMEs) that extend in the interplanetary (IP) space and interact with the underlying solar wind (SW). ICMEs and their corresponding shocks can sweep out galactic cosmic rays (GCRs) and thus modulate their intensity, resulting in non-recurrent Forbush decreases (FDs). In this work, we selected all FDs that were associated with a sudden storm commencement (SSC) at Earth, and a solar driver (e.g., CME) was clearly identified as the ICME&apos;s source. We introduce and employ the tH parameter, which is the time delay (in hours) of the maximum strength of the interplanetary magnetic field from the FD onset (as is marked via the SSC), and consequently derive three groups of FD events (i.e., the early, medium, and late ones). For each of these we examine the mean characteristics of the FDs and the associated IP variations per group, as well as the resulting correlations. In addition, we demonstrate the outputs of a superposed epoch analysis, which led to an average time profile of the resulting FDs and the corresponding IP variations, per group. Finally, we interpret our results based on the theoretical expectations for the FD phenomenon. We find that both the shock sheath and the ejecta are necessary for deep GCR depressions and that the FD amplitude (A0) is larger for faster-propagating ICMEs. Additionally, we note the importance of the turbulent shock-sheath region across all groups. Finally, we present empirical relations connecting A0 to SW properties. © 2020. The American Astronomical Society. All rights reserved