Solar Physics: Overview

2020 ◽  
Author(s):  
E.R. Priest
Keyword(s):  
Solar Physics ◽  
Theoretical Models ◽  
High Energy ◽  
The Sun ◽  
Dynamo Action ◽  
Current Time ◽  
Definitive Answer ◽  
Year 2000 ◽  
High Energy Particles ◽  
The Magnetic Field

Solar physics is one of the liveliest branches of astrophysics at the current time, with many major advances that have been stimulated by observations from a series of space satellites and ground-based telescopes as well as theoretical models and sophisticated computational experiments. Studying the Sun is of key importance in physics for two principal reasons. Firstly, the Sun has major effects on the Earth and on its climate and space weather, as well as other planets of the solar system. Secondly, it represents a Rosetta stone, where fundamental astrophysical processes can be investigated in great detail. Yet, there are still major unanswered questions in solar physics, such as how the magnetic field is generated in the interior by dynamo action, how magnetic flux emerges through the solar surface and interacts with the overlying atmosphere, how the chromosphere and corona are heated, how the solar wind is accelerated, how coronal mass ejections are initiated and how energy is released in solar flares and high-energy particles are accelerated. Huge progress has been made on each of these topics since the year 2000, but there is as yet no definitive answer to any of them. When the answers to such puzzles are found, they will have huge implications for similar processes elsewhere in the cosmos but under different parameter regimes.

Detection of a change in the North-South ratio of count rates of particles of high-energy cosmic rays during a change in the polarity of the magnetic field of the Sun

JETP Letters ◽  
2015 ◽  
Vol 101 (4) ◽  
pp. 228-231
Author(s):  
A. V. Karelin ◽  
O. Adriani ◽  
G. C. Barbarino ◽  
G. A. Bazilevskaya ◽  
R. Bellotti ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
High Energy ◽  
The Sun ◽  
High Energy Cosmic Rays ◽  
The North ◽  
The Magnetic Field

scholarly journals The Sun as a Stellar Laboratory: Unsolved Problems

2004 ◽  
Vol 219 ◽  
pp. 1-10
Author(s):  
John C. Brown
Keyword(s):  
Particle Acceleration ◽  
Solar Physics ◽  
High Energy ◽  
Atmospheric Plasma ◽  
Energy Budgets ◽  
The Sun ◽  
Stellar Flare ◽  
Neupert Effect ◽  
Kinetic Effects

A brief overview is given of some of the current outstanding problems in solar physics with greatest emphasis on high energy phenomena in the atmosphere. The importance of plasma kinetic effects, as well as MHD, in understanding the complex finely structured and dynamic solar atmospheric plasma is stressed. Key results from the RHESSI Mission on energetic flare particle acceleration, propagation, and flare energy budgets are presented as are recent findings concerning the solar and stellar flare Neupert effect and the possible role of energetic particles in micro-events in the ‘non-flaring’ sun. Finally, evidence showing that magnetic fields are also important in hot star phenomena is mentioned.

scholarly journals Cygnus X-3 and Other Ultra-High-Energy γ-Ray Sources

1987 ◽  
Vol 125 ◽  
pp. 521-533
Author(s):  
John J. Barnard
Keyword(s):  
Theoretical Models ◽  
High Energy ◽  
Current Status ◽  
Ultra High Energy ◽  
X Ray ◽  
Air Shower ◽  
Γ Rays ◽  
Γ Ray ◽  
High Energy Particles

Recently, several binary X-ray sources have been found to be sources of ultra high energy γ-ray emission. Air shower observations indicate photon energies >∼ 1015 eV. We review the current status of observations from the source Cygnus X-3, and compare this data with that from the sources Hercules X-1, Vela X-1, and LMC X-4. Current theoretical models for the production of γ-rays and the acceleration of high energy particles are discussed and the consequences for the evolution of such systems are examined.

scholarly journals Plasma Energetics in Solar Flares

1980 ◽  
Vol 5 ◽  
pp. 343-350 ◽  
Author(s):  
Gerard Van Hoven
Keyword(s):  
Gamma Rays ◽  
Solar Flares ◽  
High Energy ◽  
Physical Mechanisms ◽  
Very High Energy ◽  
Physical Effects ◽  
High Energy Particles ◽  
The Magnetic Field ◽  
Dissipation Processes ◽  
Very High

I want to begin with the observation, which I will try to make clear in the following, that a solar flare comprises an incredibly complex set of phenomena. This is not only true with respect to what is seen and measured in spectacular examples, but also when one considers the constituent parts of simple, even idealized, cases. A series of different physical effects lead, as one illustration, to radiations from the flare-instability site and its surroundings which span the range from meter waves to gamma rays (Svestka 1976, Sturrock 1979).To fit within the context of this discussion, I will concentrate on the high-temperature and quasi-thermal aspects of a flare, and on the basic physical mechanisms connected with the primary energization and dissipation processes. Thus, I will treat the reconnection of the magnetic field, the bulk acceleration of particles, the thermalization and the ultimate radiation of the energy. I will not treat the optical manifestations or, at the other extreme, the acceleration of very high energy particles.

scholarly journals Cosmic ray interactions in the solar atmosphere

2019 ◽  
Vol 491 (4) ◽  
pp. 4852-4856 ◽  
Author(s):  
Hugh S Hudson ◽  
Alec MacKinnon ◽  
Mikolaj Szydlarski ◽  
Mats Carlsson
Keyword(s):  
Magnetic Field ◽  
Open Field ◽  
Solar Atmosphere ◽  
Cosmic Ray ◽  
High Energy ◽  
Emission Anisotropy ◽  
Flux Tubes ◽  
Wide Range ◽  
High Energy Particles ◽  
The Magnetic Field

ABSTRACT High-energy particles enter the solar atmosphere from Galactic or solar coronal sources, and produce ‘albedo’ emission from the quiet Sun that is now observable across a wide range of photon energies. The interaction of high-energy particles in a stellar atmosphere depends essentially upon the joint variation of the magnetic field and plasma density, which heretofore has been characterized parametrically as P ∝ Bα with P the gas pressure and B the magnitude of the magnetic field. We re-examine that parametrization by using a self-consistent 3D MHD model (Bifrost) and show that this relationship tends to P ∝ B3.5 ± 0.1 based on the visible portions of the sample of open-field flux tubes in such a model, but with large variations from point to point. This scatter corresponds to the strong meandering of the open-field flux tubes in the lower atmosphere, which will have a strong effect on the prediction of the emission anisotropy (limb brightening). The simulations show that much of the open flux in coronal holes originates in weak-field regions within the granular pattern of the convective motions seen in the simulations.

scholarly journals Monitoring and forecasting of great radiation hazards for spacecraft and aircrafts by online cosmic ray data

2005 ◽  
Vol 23 (9) ◽  
pp. 3019-3026 ◽  
Author(s):  
L. I. Dorman
Keyword(s):  
Cosmic Ray ◽  
High Energy ◽  
Radiation Hazard ◽  
Personal Health ◽  
The Sun ◽  
Positive Signal ◽  
Radiation Hazards ◽  
Monitoring And Forecasting ◽  
High Level ◽  
High Energy Particles

Abstract. We show that an exact forecast of great radiation hazard in space, in the magnetosphere, in the atmosphere and on the ground can be made by using high-energy particles (few GeV/nucleon and higher) whose transportation from the Sun is characterized by a much bigger diffusion coefficient than for small and middle energy particles. Therefore, high energy particles come from the Sun much earlier (8-20 min after acceleration and escaping into solar wind) than the main part of smaller energy particles (more than 30-60 min later), causing radiation hazard for electronics and personal health, as well as spacecraft and aircrafts. We describe here principles of an automatic set of programs that begin with "FEP-Search", used to determine the beginning of a large FEP event. After a positive signal from "FEP-Search", the following programs start working: "FEP-Research/Spectrum", and then "FEP-Research/Time of Ejection", "FEP-Research /Source" and "FEP-Research/Diffusion", which online determine properties of FEP generation and propagation. On the basis of the obtained information, the next set of programs immediately start to work: "FEP-Forecasting/Spacecrafts", "FEP-Forecasting/Aircrafts", "FEP-Forecasting/Ground", which determine the expected differential and integral fluxes and total fluency for spacecraft on different orbits, aircrafts on different airlines, and on the ground, depending on altitude and cutoff rigidity. If the level of radiation hazard is expected to be dangerous for high level technology or/and personal health, the following programs will be used "FEP-Alert/Spacecrafts", "FEP-Alert/ Aircrafts", "FEP-Alert/Ground".

Multi-directional measurements of high energy particles from the Sun-Earth L1 point with STEPS

2016 ◽  
Author(s):  
S. K. Goyal ◽  
M. Shanmugam ◽  
A. R. Patel ◽  
T. Ladiya ◽  
Neeraj K. Tiwari ◽  
...  
Keyword(s):  
High Energy ◽  
The Sun ◽  
High Energy Particles

A profile of the Io dust cloud and plasma torus as observed from Juno

2020 ◽  
Author(s):  
John L. Jørgensen ◽  
Troelz Denver ◽  
Mathias Benn ◽  
Peter S. Jørgensen ◽  
Matija Herceg ◽  
...  
Keyword(s):  
Particle Flux ◽  
Relativistic Particle ◽  
Dust Cloud ◽  
High Energy ◽  
Trapped Particles ◽  
Field Lines ◽  
Plasma Torus ◽  
High Energy Particles ◽  
The Magnetic Field ◽  
Orbit Insertion

<p>The Juno MAG investigation’s dedicated star tracker, the Advanced Stellar Compass (ASC), has continuously monitored high energy particles fluxes in Jupiter’s magnetosphere subsequent to Juno’s orbit insertion on July 4, 2016. The ASC primary function is to provide an accurate inertial attitude reference, however, the most energetic particles in Jupiter’s trapped population is capable of penetrating the radiation shield of the ASC where they are registered. Such particles have energy >15MeV for electrons, >80MeV for protons, and >~GeV for heavier elements. With a sample cadence of 250ms, the ASC renders a detailed mapping of the trapped particles throughout space traversed by Juno. The particles travelling along the magnetic field lines crossing near the orbit of Io will be strongly influenced by interaction with any matter, moon, dust or plasma, which happens to be in their trajectory. The relativistic particle flux monitored, is highly relativistic, and has as such a modest retention time in any drift shell. The short lifetime of the trapped particles, and the constant scanning of field lines connecting to the Io environment enables a detailed profiling of the dust and plasma density, as well as the effect to/from Io itself. We present the measurement and their implications for the azimuthal and radial dust cloud and plasma torus.</p>

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