scholarly journals Energetic-Particle Abundances in Impulsive Solar Flare Events

1994 ◽  
Vol 142 ◽  
pp. 649-667 ◽  
Author(s):  
D. V. Reames ◽  
J. P. Meyer ◽  
T. T. von Rosenvinge
Keyword(s):  
Solar Flare ◽  
Electron Temperature ◽  
Solar Flares ◽  
Solar Disk ◽  
Energetic Particle ◽  
Solar Maximum ◽  
Source Region ◽  
Plasma Waves ◽  
Heavy Elements ◽  
Common Occurrence

AbstractWe report on the abundances of energetic particles from impulsive solar flares, including those from a survey of 2283He-rich events, with3He/4He > 0.1, observed by theISEE 3spacecraft from 1978 August through 1991 April. The rate of occurrence of these events corresponds to ~1000 events yr−1on the solar disk at solar maximum. Thus the resonant plasma processes that enhance3He and heavy elements are a common occurrence in impulsive solar flares. To supply the observed fluence of3He in large events, the acceleration must be highly efficient and the source region must be relatively deep in the atmosphere at a density of more than 1010atoms cm−3.3He/4He may decrease in very large impulsive events because of depletion of3He in the source region.The event-to-event variations in3He/4He, H/4He,e/p, and Fe/C are uncorrelated in our event sample. Abundances of the elements show a pattern in which, relative to coronal composition,4He, C, N, and O have normal abundance ratios, while Ne, Mg, and Si are enhanced by a factor ~2.5 and Fe by a factor ~7. This pattern suggests that elements are accelerated from a region of the corona with an electron temperature of ~3-5 MK, where elements in the first group are fully ionized (Q/A =0.5), those in the second group have two orbital electrons (Q/A~ 0.43), and Fe hasQ/A~ 0.28. Ions with the same gyrofrequency absorb waves of that frequency and are similarly accelerated and enhanced. Further stripping may occur after acceleration as the ions begin to interact with the streaming electrons that generated the plasma waves.Subject headings: Sun: abundances — Sun: flares — Sun: particle emission

scholarly journals Preface

1991 ◽  
Vol 336 (1643) ◽  
pp. 323-323
Keyword(s):  
Solar Flare ◽  
Energy Release ◽  
Gamma Rays ◽  
Solar Flares ◽  
Solar Maximum ◽  
Interplanetary Space ◽  
Release Site ◽  
Solar Maximum Mission ◽  
New Information ◽  
Three Space

During the period of the 1980 solar maximum three space missions (P78-1, Solar Maximum Mission and Hinotori ) carried out extensive studies of solar flares. In their different ways all of these missions contributed significant new information to our understanding of the solar flare phenomenon. In this volume the contribution made by these three spacecraft to the study of the energy release and the related creation of high-tem perature plasma, the transport of energy from the primary release site, the production of gamma-rays at energies up to 10 MeV and the ejection of solar matter into interplanetary space are reviewed.

Atomic physics calculations relevant to solar flare spectra

1991 ◽  
Vol 336 (1643) ◽  
pp. 471-484 ◽  
Keyword(s):  
Solar Flare ◽  
Atomic Physics ◽  
Solar Flares ◽  
Solar Maximum ◽  
Emission Lines ◽  
Atomic Data ◽  
Solar Maximum Mission ◽  
X Ray ◽  
Physical Conditions ◽  
Recombination Processes

Solar flare spectra in the ultraviolet and X-ray wavelength regions are rich in emission lines from highly ionized ions, formed at temperatures around 10 7 K. These lines can be used as valuable diagnostics for probing the physical conditions in solar flares. Such analyses require accurate atomic data for excitation, ionization and recombination processes. In this paper, we present a review of work which has already been carried out, in particular for the Solar Maximum Mission observations, and we look to future requirements for Solar-A .

Nuclei of Heavy Elements from Solar Flares

1975 ◽  
Vol 68 ◽  
pp. 411-421
Author(s):  
C. Y. Fan ◽  
G. Gloeckler ◽  
D. Hovestadt
Keyword(s):  
Solar Flare ◽  
Solar Flares ◽  
Heavy Elements ◽  
Theoretical Interpretation ◽  
List Type ◽  
Type Number ◽  
Comprehensive Review ◽  
Solar Composition ◽  
Nuclear Species ◽  
Isotopic Abundances

This paper presents a comprehensive review of the up to date knowledge on nuclear species of Z>2 from solar flares. It covers the following five topics: (I)Solar flare particles of energies >15 MeV n-1 and solar composition;(II)solar flare particles of energies >15 MeV n-1, the enrichment of heavier elements;(III)theoretical interpretation of the enrichment;(IV)the charge states of solar particles; and(V)isotopic abundances of solar flare particles.

The role of magnetic loops in solar flares

1991 ◽  
Vol 336 (1643) ◽  
pp. 389-400 ◽  
Keyword(s):  
Solar Flare ◽  
Spatial Structure ◽  
Spatial Resolution ◽  
Solar Flares ◽  
Solar Maximum ◽  
Magnetic Topology ◽  
Solar Maximum Mission ◽  
X Ray ◽  
Ultraviolet Observations

X -ray and ultraviolet observations of flares have provided much important information on their spatial structure and magnetic topology. The early observations from Skylab emphasized the role of simple loops and loop arcades, but later observations from the Solar Maximum Mission have greatly complicated this picture. Flares appear in a multitude of loops with complex spatial and temporal interrelations. In many cases, interactions between different loops appear to play a crucial role. The inferred magnetic topology of solar flares will be reviewed with emphasis on the implications for processes of energy release and transfer. It will be shown that the spatial resolution of the observations obtained so far is still inadequate for solving many basic questions of solar flare research.

scholarly journals NO<sub>y</sub> production, ozone loss and changes in net radiative heating due to energetic particle precipitation in 2002–2010

2017 ◽  
Author(s):  
Miriam Sinnhuber ◽  
Uwe Berger ◽  
Bernd Funke ◽  
Holger Nieder ◽  
Thomas Reddmann ◽  
...  
Keyword(s):  
Energetic Particle ◽  
Solar Maximum ◽  
Lower Thermosphere ◽  
Solar Proton ◽  
Radiative Heating ◽  
Proton Event ◽  
Late Winter ◽  
Ozone Loss ◽  
Energetic Particle Precipitation ◽  
Ionization Rates

Abstract. We analyze the impact of energetic particle precipitation on the stratospheric nitrogen budget, ozone abundances and net radiative heating using results from three global chemistry-climate models considering solar protons and geomagnetic forcing due to auroral or radiation belt electrons. Two of the models cover the atmosphere up to the lower thermosphere, the source region of auroral NO production. Geomagnetic forcing in these models is included by prescribed ionization rates. One model reaches up to about 80 km, and geomagnetic forcing is included by applying an upper boundary condition of auroral NO mixing ratios parameterized as a function of geomagnetic activity. Despite the differences in the implementation of the particle effect, the resulting modeled NOy in the upper mesosphere agrees well between all three models, demonstrating that geomagnetic forcing is represented in a consistent way either by prescribing ionization rates or by prescribing NOy at the model top. Compared with observations of stratospheric and mesospheric NOy from the MIPAS instrument for the years 2002–2010, the model simulations reproduce the spatial pattern and temporal evolution well. However, after strong sudden stratospheric warmings, particle induced NOy is underestimated by both high-top models, and after the solar proton event in October 2003, NOy is overestimated by all three models. Model results indicate that the large solar proton event in October 2003 contributed about 1–2 Gmol (109 mol) NOy per hemisphere to the stratospheric NOy budget, while downwelling of auroral NOx from the upper mesosphere and lower thermosphere contributes up to 4 Gmol NOy. Accumulation over time leads to a constant particle-induced background of about 0.5–1 Gmol per hemisphere during solar minimum, and up to 2 Gmol per hemisphere during solar maximum. Related negative anomalies of ozone are predicted by the models nearly in every polar winter, ranging from 10–50 % during solar maximum to 2–10 % during solar minimum. Ozone loss continues throughout polar summer after strong solar proton events in the Southern hemisphere and after large sudden stratospheric warmings in the Northern hemisphere. During mid-winter, the ozone loss causes a reduction of the infrared radiative cooling, i.e., a positive change of the net radiative heating (effective warming), in agreement with analyses of geomagnetic forcing in stratospheric temperatures which show a warming in the late winter upper stratosphere. In late winter and spring, the sign of the net radiative heating change turns to negative (effective cooling). This spring-time cooling lasts well into summer and continues until the following autumn after large solar proton events in the Southern hemisphere, after sudden stratospheric warmings in the Northern hemisphere.

scholarly journals Models and data analysis tools for the Solar Orbiter mission

2020 ◽  
Vol 642 ◽  
pp. A2 ◽  
Author(s):  
A. P. Rouillard ◽  
R. F. Pinto ◽  
A. Vourlidas ◽  
A. De Groof ◽  
W. T. Thompson ◽  
...  
Keyword(s):  
Data Analysis ◽  
Solar Disk ◽  
Source Region ◽  
Solar Interior ◽  
The Sun ◽  
Science Operations ◽  
Wide Range ◽  
Tools And Techniques ◽  
Orbiter Mission ◽  
Current Modelling

Context. The Solar Orbiter spacecraft will be equipped with a wide range of remote-sensing (RS) and in situ (IS) instruments to record novel and unprecedented measurements of the solar atmosphere and the inner heliosphere. To take full advantage of these new datasets, tools and techniques must be developed to ease multi-instrument and multi-spacecraft studies. In particular the currently inaccessible low solar corona below two solar radii can only be observed remotely. Furthermore techniques must be used to retrieve coronal plasma properties in time and in three dimensional (3D) space. Solar Orbiter will run complex observation campaigns that provide interesting opportunities to maximise the likelihood of linking IS data to their source region near the Sun. Several RS instruments can be directed to specific targets situated on the solar disk just days before data acquisition. To compare IS and RS, data we must improve our understanding of how heliospheric probes magnetically connect to the solar disk. Aims. The aim of the present paper is to briefly review how the current modelling of the Sun and its atmosphere can support Solar Orbiter science. We describe the results of a community-led effort by European Space Agency’s Modelling and Data Analysis Working Group (MADAWG) to develop different models, tools, and techniques deemed necessary to test different theories for the physical processes that may occur in the solar plasma. The focus here is on the large scales and little is described with regards to kinetic processes. To exploit future IS and RS data fully, many techniques have been adapted to model the evolving 3D solar magneto-plasma from the solar interior to the solar wind. A particular focus in the paper is placed on techniques that can estimate how Solar Orbiter will connect magnetically through the complex coronal magnetic fields to various photospheric and coronal features in support of spacecraft operations and future scientific studies. Methods. Recent missions such as STEREO, provided great opportunities for RS, IS, and multi-spacecraft studies. We summarise the achievements and highlight the challenges faced during these investigations, many of which motivated the Solar Orbiter mission. We present the new tools and techniques developed by the MADAWG to support the science operations and the analysis of the data from the many instruments on Solar Orbiter. Results. This article reviews current modelling and tool developments that ease the comparison of model results with RS and IS data made available by current and upcoming missions. It also describes the modelling strategy to support the science operations and subsequent exploitation of Solar Orbiter data in order to maximise the scientific output of the mission. Conclusions. The on-going community effort presented in this paper has provided new models and tools necessary to support mission operations as well as the science exploitation of the Solar Orbiter data. The tools and techniques will no doubt evolve significantly as we refine our procedure and methodology during the first year of operations of this highly promising mission.

ANALYSIS OF ENERGETIC PARTICLE EVENTS FOLLOWING SOLAR FLARES OF SEPTEMBER 24 AND NOVEMBER 22, 1977

1979 ◽  
pp. 413-416 ◽  
Author(s):  
V.G. Kurt ◽  
Yu.I. Logachev ◽  
V.G. Stolpovsky ◽  
N.F. Pissarenko ◽  
M. Gros ◽  
...  
Keyword(s):  
Solar Flares ◽  
Energetic Particle

scholarly journals On the Possibility of Local Magnetic Field Intensification in Evaporating Chromospheric Solar Flare Plasma

1989 ◽  
Vol 104 (2) ◽  
pp. 341-344
Author(s):  
V. N. Dermendjiev ◽  
G. T. Buyukliev ◽  
I. Ph. Panayotova
Keyword(s):  
Magnetic Field ◽  
Solar Flare ◽  
Solar Flares ◽  
Local Magnetic Field ◽  
Plume Structure ◽  
The Subject ◽  
Convective Plume ◽  
Flare Plasma ◽  
Initial Magnetic Field ◽  
Moving Vortex

The investigations of plasma motions at the initial phases of solar flares (Antonucci and Dennis, 1983; Doschek, 1983; Watanabe, 1987) suggest evaporation from the chromospheric flaring area. According to de Jager (1983) when seen at the limb the evaporated plasma will look like a “convective plume” and it can be seen separated from heated footpoint areas.The subject of this work is the study of the possibility of forming hydrodynamic structures o-f thermal and starting plume's kind at the time of evaporation of the upper chromosphere in a flaring area. Also the possibility of increasing an initial magnetic field by a periodically moving vortex in a plume structure is investigated.

scholarly journals Mechanisms for Flash Phase Phenomena in Solar Flares

1974 ◽  
Vol 57 ◽  
pp. 253-282 ◽  
Author(s):  
Dean F. Smith
Keyword(s):  
Solar Flares ◽  
Acoustic Waves ◽  
Plasma Waves ◽  
Electron Plasma ◽  
X Rays ◽  
Fermi Acceleration ◽  
Acceleration Region ◽  
Low Frequencies ◽  
Coulomb Collisions ◽  
The Earth

Mechanisms for explaining the various forms of particles and radiation observed during the flash phase of solar flares are reviewed under the working hypothesis that the flash phase is the time in which electrons and to a lesser degree protons are accelerated in less than one second. A succession of such accelerations is allowed to explain longer lasting or quasi-periodic phenomena. Mechanisms capable of such acceleration are reviewed and it is concluded that first-order Fermi acceleration in a reconnecting current sheet is the most likely basic process. Such acceleration, however, gives rise to a rather narrow distribution of particle velocities along a given field line which is unstable to the production of electron plasma and ion-acoustic waves. This plasma turbulence can heat the plasma to produce soft X-rays and filter the initially narrow velocity distribution to produce a power law energy distribution. Electrons travelling inward from the acceleration region produce hard X-rays by bremsstrahlung and microwave bursts by gyro-synchrotron emission. Whereas the interpretation of X-ray spectra is relatively straightforward, the interpretation of microwave spectra is difficult because the source at low frequencies can be made optically thick by several different mechanisms.Electrons travelling further inward presumably thermalize and produce impulsive EUV and Hα emission. The theory for these emissions, although amenable to present techniques in radiative transfer, has not been worked out. Electrons travelling outward give rise to type III radio bursts by excitation of electron plasma waves and the electrons observed at the Earth. Study of the interaction of a stream of electrons with the ambient plasma shows that the electron spectra observed at the Earth do not necessarily reflect their spectrum at the acceleration region since they interact via plasma waves as well as through Coulomb collisions. The mechanisms for the conversion of plasma waves into radiation and the propagation of the radiation from its source to the observer are reviewed.

scholarly journals Collisionless Effects on Beam-Return Current Systems in Solar Flares

1985 ◽  
Vol 107 ◽  
pp. 521-525
Author(s):  
Loukas Vlahos ◽  
H. L. Rowland
Keyword(s):  
Solar Flares ◽  
Current System ◽  
Large Fraction ◽  
Coupled System ◽  
Impulsive Phase ◽  
Plasma Waves ◽  
Rate Equations ◽  
Return Current ◽  
Strong Turbulence ◽  
Current Systems

A large fraction of the electrons which are accelerated during the impulsive phase of solar flares stream towards the chromosphere and are unstable to the growth of plasma waves. The linear and nonlinear evolution of plasma waves as a function of time is analyzed with the use of a set of rate equations that follow in time the non-linearly coupled system of plasma waves-ion fluctuations. The nonthermal tail formed during the stabilization of the precipitated electrons can stabilize the Anomalous Doppler Resonance instability and prevent the isotropization of the energetic electrons. The precipitating electrons modify the way the return current is carried by the background plasma. In particular, the return current is not carried by the bulk of the electrons but by a small number of high velocity electrons. For beam/plasma densities ≳ 10−3, this can reduce the effects of collisions and heating by the return current. For higher density beams where the return current could be unstable to current driven instabilities, the effects of strong turbulence anomalous resistivity is shown to prevent the appearance of such instabilities. Our main conclusion is that the beam-return current system is interconnected and how the return current is carried is determined by the beam generated strong turbulence.

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