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We investigate the properties of acoustic events (AEs), defined as spatially concentrated and short duration energy flux, in the quiet sun using observations of a 2D field of view (FOV) with high spatial and temporal resolution provided by…

Solar and Stellar Astrophysics · Physics 2015-06-05 J. -M. Malherbe , T. Roudier , M. Rieutord , T. Berger , Z. Frank

Coronal Mass Ejections (CMEs) are subject to changes in their direction of propagation, tilt, and other properties as they interact with the variable solar wind. We investigated the heliospheric propagation of 15 Earth-impacting CMEs…

Solar and Stellar Astrophysics · Physics 2024-11-05 Sandeep Kumar , Nandita Srivastava , Nat Gopalswamy , Ashutosh Dash

Collisionless shock waves, ubiquitous in the universe, are crucial for particle acceleration in various astrophysical systems. Currently, the heliosphere is the only natural environment available for their in situ study. In this work, we…

Solar Energetic Particle (SEP) acceleration and injection into interplanetary space during gradual SEP events is thought to take place at Coronal Mass Ejection (CME)-driven shocks. Features of measured intensity profiles at 1 au have been…

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

We model the transport of solar energetic particles (SEPs) in the solar wind. We propagated relativistic test particles in the field of a steady three-dimensional magnetohydrodynamic simulation of the solar wind. We used the code MPI-AMRVAC…

Solar and Stellar Astrophysics · Physics 2025-02-19 Houeibib Ahmed , Pantellini Filippo , Griton Lea

Differential flows among different ion species are often observed in the solar wind, and such ion differential flows can provide the free energy to drive Alfv\'en/ion-cyclotron and fast-magnetosonic/whistler instabilities. Previous works…

Solar and Stellar Astrophysics · Physics 2021-11-01 Wen Liu , Jinsong Zhao , Huasheng Xie , Yuhang Yao , Dejin Wu , L. C. Lee

A statistical analysis of 15,210 electron velocity distribution function (VDF) fits, observed within $\pm$2 hours of 52 interplanetary (IP) shocks by the $Wind$ spacecraft near 1 AU, is presented. This is the second in a three-part series…

Over decades of solar wind observations, heavy ions have been observed to have a higher temperature and flow faster than protons in the solar corona and heliosphere. Remote observations have largely been limited to the low corona ($<…

We study the variation of the shape of the proton intensity-time profiles in simulated gradual Solar Energetic Particle (SEP) events with the relative observer's position in space with respect to the main direction of propagation of an…

Solar and Stellar Astrophysics · Physics 2015-06-17 R. Rodríguez-Gasén , A. Aran , B. Sanahuja , C. Jacobs , S. Poedts

We study selected properties of Solar Energetic Particle (SEP) events as inferred from their associated radio emissions. We used a catalogue of 115 SEP events that consists of entries of proton intensity enhancements at one AU, with…

Solar and Stellar Astrophysics · Physics 2015-08-12 A. Kouloumvakos , A. Nindos , E. Valtonen , C. E. Alissandrakis , O. Malandraki , P. Tsitsipis , A. Kontogeorgos , X. Moussas , A. Hillaris

Solar Energetic Particle (SEP) events are critical for understanding particle acceleration and transport in the heliosphere. While most SEP events involve outward streaming particles along open magnetic field lines, bidirectional events…

This paper investigates the onset time of Solar Energetic Particle (SEP) events with numerical simulations, and analyses the accuracy of the Velocity Dispersion Analysis (VDA) method. Using a 3-dimensional focused transport model, we…

Solar and Stellar Astrophysics · Physics 2015-06-18 Y. Wang , G. Qin

Recent progress in realistic simulations of solar convection have given us an unprecedented opportunity to evaluate the robustness of solar interior structures and dynamics obtained by methods of local helioseismology. We present results of…

Wave-particle instabilities driven by departures from local thermodynamic equilibrium have been conjectured to play a role in governing solar wind dynamics. We calculate the statistical variation of linear stability over a large subset of…

Solar and Stellar Astrophysics · Physics 2020-01-08 Kristopher G. Klein , Mihailo Martinovic , David Stansby , Timothy S. Horbury

Solar Orbiter's four in-situ instruments have recorded numerous energetic electron events at heliocentric distances between 0.5 and 1au. We analyse energetic electron fluxes, spectra, pitch angle distributions, associated Langmuir waves,…

We summarize observations of around a thousand solar energetic particle (SEP) events since 1967 that include ~25 MeV protons, made by various near-Earth spacecraft (IMPs 4, 5, 7, 8, ISEE 3, SOHO), that encompass Solar Cycle 20 to the…

Solar and Stellar Astrophysics · Physics 2016-08-11 Ian G. Richardson , Tycho T. von Rosenvinge , Hilary V. Cane

Using high-cadence extreme-ultraviolet (EUV) images obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we investigate the solar sources of 26 $^{3}$He-rich solar energetic particle (SEP) events at…

Solar and Stellar Astrophysics · Physics 2015-05-27 Nariaki V. Nitta , Glenn M. Mason , Linghua Wang , Christina M. S. Cohen , Mark E. Wiedenbeck

Drifts are known to play a role in galactic cosmic ray transport within the heliosphere and are a standard component of cosmic ray propagation models. However, the current paradigm of Solar Energetic Particle (SEP) propagation holds the…

Solar and Stellar Astrophysics · Physics 2013-08-30 M. S. Marsh , S. Dalla , J. Kelly , T. Laitinen

Solar energetic particle (SEP) events are one of the most crucial aspects of space weather that require continuous monitoring and forecasting using robust methods. We demonstrate a proof of concept of using a data-driven supervised…

Solar and Stellar Astrophysics · Physics 2024-08-13 Sumanth A. Rotti , Berkay Aydin , Petrus C. Martens

The solar wind (SW) and the extreme ultraviolet (EUV) radiation modulate fluxes of interstellar and heliospheric particles inside the heliosphere both in time and in space. Understanding this modulation is necessary to correctly interpret…

Space Physics · Physics 2020-08-19 Justyna M. Sokół , D. J. McComas , M. Bzowski , M. Tokumaru