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Hydrogen has been almost completely ignored in studies of the abundance patterns of the chemical elements in solar energetic particles (SEPs). We seek to find impulsive events where H fits these abundance patterns and document the events…

Solar and Stellar Astrophysics · Physics 2019-04-10 Donald V. Reames

We revisited assessments of the occurrence probability distribution of large events in solar energetic particles (SEP), based on measurements of cosmogenic radionuclides in lunar rocks. We present a combined cumulative occurrence…

Solar and Stellar Astrophysics · Physics 2014-01-17 Gennady A. Kovaltsov , Ilya G. Usoskin

We have spent 50 years in heated discussion over which populations of solar energetic particles (SEPs) are accelerated at flares and which by shock waves driven out from the Sun by coronal mass ejections (CMEs). The association of the large…

Solar and Stellar Astrophysics · Physics 2017-09-19 Donald V. Reames

When observed at 1 AU, slow solar wind is typically considered to have originated in source regions with magnetic topologies that are intermittently open to the heliosphere. Fast wind is typically considered to have originated in source…

Solar and Stellar Astrophysics · Physics 2025-08-27 B. L. Alterman , Y. J. Rivera , S. T. Lepri , J. M. Raines , R. D'Amicis

Metric type II solar radio bursts and solar energetic particles (SEPs) are both associated with shock fronts driven by coronal mass ejections (CMEs) in the solar corona. Recent studies of ground level enhancements (GLEs), regular large…

We study the solar energetic particle (SEP) event associated with the 2012 July 23 extreme solar storm, for which STEREO and the spacecraft at L1 provide multi-point remote sensing and in situ observations. The extreme solar storm, with a…

Solar and Stellar Astrophysics · Physics 2016-08-31 Bei Zhu , Ying D. Liu , Janet G. Luhmann , Huidong Hu , Rui Wang , Zhongwei Yang

Enhancements in 3He abundance, a characteristic feature of impulsive solar energetic particle (ISEP) events, are also frequently observed in gradual SEP (GSEP) events. Understanding the origin of this enrichment is crucial for identifying…

Solar and Stellar Astrophysics · Physics 2025-10-21 R. Bucik , S. T. Hart , M. A. Dayeh , M. I. Desai , G. M. Mason , M. E. Wiedenbeck

We fit the $\sim$0.1-500 MeV/nucleon H-Fe spectra in 46 large SEP events surveyed by Desai et al. (2016) with the double power-law Band function to obtain a normalization constant, low- and high-energy parameters $\gamma_a$ and $\gamma_b$;…

The need for quantitative characterization of the solar energetic particle (SEP) dynamics goes beyond being an academic discipline only. It has numerous practical implications related to human activity in space. The terrestrial magnetic…

Space Physics · Physics 2022-09-21 Valeriy Tenishev , Lulu Zhao , Igor Sokolov

On 2022 September 5, a large solar energetic particle (SEP) event was detected by Parker Solar Probe (PSP) and Solar Orbiter (SolO), at heliocentric distances of 0.07 and 0.71 au, respectively. PSP observed an unusual velocity-dispersion…

Solar energetic particle (SEP) events are related to flares and coronal mass ejections (CMEs). This work is a new investigation of statistical relationships between SEP peak intensities - deka-MeV protons and near-relativistic electrons -…

Solar and Stellar Astrophysics · Physics 2014-11-18 G. Trottet , S. Samwel , K. -L. Klein , T. Dudok de Wit , R. Miteva

In this paper we examine a low-energy SEP event observed by IS$\odot$IS's Energetic Particle Instrument-Low (EPI-Lo) inside 0.18 AU on September 30, 2020. This small SEP event has a very interesting time profile and ion composition. Our…

Context/Aims: We present a list of 61 solar energetic electron (SEE) events measured by the MESSENGER mission and the radial dependences of the electron peak intensity and the peak-intensity energy spectrum. The analysis comprises the…

We revisit a multi-spacecraft study of the element abundances of solar energetic particles (SEPs) in the 23 January 2012 event, where the power-law pattern of enhancements versus the mass-to-charge ratio A/Q for the elements C through Fe…

Solar and Stellar Astrophysics · Physics 2020-04-28 Donald V. Reames

Large solar eruptive events, including solar flares and coronal mass ejections (CMEs), can lead to solar energetic particle (SEP) events. During these events, protons are accelerated up to several GeV and pose numerous space weather risks.…

Solar and Stellar Astrophysics · Physics 2023-03-08 Charlotte Waterfall , Silvia Dalla , Osku Raukunen , Daniel Heynderickx , Piers Jiggens , Rami Vainio

Solar energetic particle (SEP) events are associated with coronal mass ejections (CMEs) and/or solar flares. SEPs travel through the corona and interplanetary space to reach Earth, posing a radiation hazard to spacecraft and astronauts…

Solar and Stellar Astrophysics · Physics 2024-11-07 Lei Cheng , Ming Zhang , Ryun Young Kwon , David Lario

Helioseismology has shown that the chemical composition of the Sun has changed over its lifetime. The surface abundance of helium and heavy elements is believed to have decreased by up to 10% relative to their initial values. However, this…

Astrophysics · Physics 2015-06-24 S. Turcotte , R. F. Wimmer-Schweingruber

The Sun is an effective particle accelerator producing solar energetic particle (SEP) events during which particles up to several GeVs can be observed. Those events observed at Earth with the neutron monitor network are called ground level…

Space Physics · Physics 2016-12-21 Patrick Kühl , Nina Dresing , Bernd Heber , Andreas Klassen

Corotation of particle-filled magnetic flux tubes is generally thought to have a minor influence on the time-intensity profiles of gradual Solar Energetic Particle (SEP) events. For this reason many models solve the focussed transport…

Solar and Stellar Astrophysics · Physics 2023-03-01 Adam Hutchinson , Silvia Dalla , Timo Laitinen , Charlotte O. G. Waterfall

Shock waves driven by fast and wide coronal mass ejections (CMEs) are highly efficient particle accelerators involved in the production of solar energetic particle (SEP) events. The gradual SEP event measured by STEREO-A and B on October…