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An empirical model for forecasting solar wind speed related geomagnetic events is presented here. The model is based on the estimated location and size of solar coronal holes. This method differs from models that are based on photospheric…

Astrophysics · Physics 2008-11-26 S. Robbins , C. J. Henney , J. W. Harvey

Why the tenuous solar outer atmosphere, or corona, is much hotter than the underlying layers remains one of the greatest challenge for solar modeling. Detailed diagnostics of the coronal thermal structure come from extreme ultraviolet (EUV)…

Solar and Stellar Astrophysics · Physics 2018-05-02 Gregory Fleishman , Sophie Musset , Véronique Bommier , Lindsay Glesener

Probing the solar corona is crucial to study the coronal heating and solar wind acceleration. However, the transient and inhomogeneous solar wind flows carry large-amplitude inherent Alfven waves and turbulence, which make detection more…

The shape of the electron velocity distribution function plays an important role in the dynamics of the solar wind acceleration. Electrons are normally modelled with three components, the core, the halo, and the strahl. We investigate how…

The solar wind emanates from the hot and tenuous solar corona. Earlier studies using 1.5 dimensional simulations show that Alfv\'{e}n waves generated in the photosphere play an important role in coronal heating through the process of…

Solar and Stellar Astrophysics · Physics 2015-05-30 Takuma Matsumoto , Takeru Ken Suzuki

The solar corona is much hotter than the photosphere and chromosphere, but the physical mechanism responsible for heating the coronal plasma remains unidentified yet. The thermal microwave emission, which is produced in strong magnetic…

Solar and Stellar Astrophysics · Physics 2025-08-27 Alexey A. Kuznetsov , Gregory D. Fleishman , Gelu M. Nita , Sergey A. Anfinogentov

We investigate the origin of mesoscale structures in the solar wind called microstreams defined as enhancements in solar wind speed and temperature that last several hours. They were first clearly detected in Helios and Ulysses solar wind…

Solar and Stellar Astrophysics · Physics 2023-10-24 Bahaeddine Gannouni , Victor Réville , Alexis Rouillard

The dependence of the sources and properties of the near-Earth solar wind on solar cycle activity is an important issue in solar and space physics. We use the improved two-step mapping procedure that takes into account the initial…

Solar and Stellar Astrophysics · Physics 2024-07-02 Xinzheng Shi , Hui Fu , Zhenghua Huang , Limei Yan , Chi Ma , Chenxi Huangfu , Hongqiang Song , Lidong Xia

The solar inner corona is a region that plays a critical role in energizing the solar wind and propelling it to supersonic and supra-Alfvenic velocities. Despite its importance, this region remains poorly understood because of being least…

Solar and Stellar Astrophysics · Physics 2023-08-25 Richa N. Jain , R. K. Choudhary , Anil Bhardwaj , T. Imamura , Anshuman Sharma , Umang M. Parikh

We present an examination of the First Ionization Potential (FIP) fractionation scenario invoking the ponderomotive force in the chromosphere, and its implications for the source(s) of slow speed solar winds by using observations from The…

Solar and Stellar Astrophysics · Physics 2020-05-25 Natsuha Kuroda , J. Martin Laming

We developed a new technique for registration of the far solar corona from ground-based observations at distances comparable to those obtained from space coronagraphs. It makes possible visualization of fine details of studied objects…

Solar and Stellar Astrophysics · Physics 2015-05-14 Y. Y. Shopov , D. A. Stoykova , K. Stoitchkova , L. T. Tsankov , A. Tanev , Kl. Burin , St. Belchev , V. Rusanov , D. Ivanov , A. Stoev , P. Muglova , I. Iliev

The relative abundances of chemical elements and isotopes have been our most effective tool in identifying and understanding energetic particles. The early surprise in solar energetic particles (SEPs) was 1000-fold enhancements in 3He/4He…

Solar and Stellar Astrophysics · Physics 2018-04-03 Donald V. Reames

We present an analysis of small-scale, periodic, solar-wind density enhancements (length-scales as small as \approx 1000 Mm) observed in images from the Heliospheric Imager (HI) aboard STEREO A. We discuss their possible relationship to…

Solar and Stellar Astrophysics · Physics 2010-09-30 Nicholeen M. Viall , Harlan E. Spence , Angelos Vourlidas , Russell Howard

The solar wind, a stream of charged particles originating from the Sun and transcending interplanetary space, poses risks to technology and astronauts. In this work, we develop a prediction model to forecast the solar wind speed at the…

Solar and Stellar Astrophysics · Physics 2025-01-22 Daniel Collin , Yuri Shprits , Stefan J. Hofmeister , Stefano Bianco , Guillermo Gallego

Multiwavelength observations of the propagating disturbances (PDs), discovered by Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO), are analyzed to determine its driving mechanism and physical nature. Two magnetic…

The acceleration of thermal solar wind protons at spherical interplanetary shocks driven by coronal mass ejections is investigated. The solar wind velocity distribution is represented using $\kappa$-functions, which are transformed in…

Space Physics · Physics 2019-08-07 P. L. Prinsloo , R. D. Strauss , J. A. le Roux

Solar wind heating rates have often been calculated by fitting plasma and magnetic field data with a set of model functions. In this letter, we show that the rates obtained by such an approach strongly depend on the rather arbitrary choice…

Solar and Stellar Astrophysics · Physics 2023-02-21 Arnaud Zaslavsky

The corona of the Sun is dominated by emission from loop-like structures. When observed in X-ray or extreme ultraviolet emission, these million K hot coronal loops show a more or less constant cross section. In this study we show how the…

Solar and Stellar Astrophysics · Physics 2015-06-11 H. Peter , S. Bingert

Elemental abundances in the solar corona and solar wind are often observed to differ from those in the solar photosphere, most commonly showing an enhancement of low first ionization-potential (FIP) elements (the FIP effect). The…

Solar and Stellar Astrophysics · Physics 2026-05-05 Paola Testa , Juan Martinez-Sykora , Bart De Pontieu , Alberto Sainz Dalda , David Long , Deborah Baker , David H. Brooks

We analyze measured proton and electron temperatures in the high-speed solar wind in order to calculate the separate rates of heat deposition for protons and electrons. When comparing with other regions of the heliosphere, the fast solar…

Solar and Stellar Astrophysics · Physics 2015-05-13 Steven R. Cranmer , William H. Matthaeus , Benjamin A. Breech , Justin C. Kasper