scholarly journals Hard X-ray Spectrum of the Above-the-Looptop Source in Impulsive Solar Flares

2000 ◽  
Vol 195 ◽  
pp. 413-414
Author(s):  
S. Masuda
Keyword(s):  
Magnetic Reconnection ◽  
Energy Release ◽  
Solar Flares ◽  
Count Rate ◽  
High Quality ◽  
X Ray ◽  
Flare Energy

Extended AbstractThe Hard X-ray Telescope (HXT: Kosugi et al. 1991) onboard Yohkoh has observed that, in impulsive solar flares, a hard X-ray source is located above the apex of a soft X-ray flaring loop, in addition to double footpoint sources (Masuda et al. 1994, 1995). This observation suggests that flare energy-release, probably magnetic reconnection, takes place not in the soft X-ray loop but above the loop. It is important to derive the hard X-ray spectrum of the above-the-looptop source accurately in order to understand how electrons are energized there. The above-the-looptop source was most clearly observed during the 13 January 1992 flare. However, the count rate, especially in the H-band (53–93 keV), is too small to synthesize high-quality images and to derive an accurate spectrum.

scholarly journals Solar Flares as an Ongoing Magnetic Reconnection Process

1993 ◽  
Vol 141 ◽  
pp. 239-248 ◽  
Author(s):  
Saku Tsuneta
Keyword(s):  
Magnetic Reconnection ◽  
Energy Release ◽  
Solar Flares ◽  
Spatial Dimension ◽  
Energy Scale ◽  
Convincing Evidence ◽  
Neutral Sheet ◽  
X Ray ◽  
Reconnection Process ◽  
Limb Flare

AbstractThe soft X-ray images taken by the Yohkoh Soft X-ray Telescope (SXT) provide a powerful new tool to solve the mechanism of solar flares. In particular, a limb flare that occurred on 1991, December 2 gives us convincing evidence that magnetic reconnection of a neutral sheet formed at the loop top participates in the flare energy release. The neutral sheet appears to be associated with a destabilized rising loop system (filament) sheared with respect to the flaring loop. Similar formations of X-ray arcades are seen in the quiet Sun associated with filament eruptions on much larger spatial dimension and with a much smaller energy scale.

scholarly journals Gamma-rays from Solar Flares

2000 ◽  
Vol 195 ◽  
pp. 123-132 ◽  
Author(s):  
R. Ramaty ◽  
N. Mandzhavidze
Keyword(s):  
Energy Release ◽  
Gamma Rays ◽  
Solar Flares ◽  
Gamma Ray ◽  
Particle Interaction ◽  
Mass Motion ◽  
Relativistic Electrons ◽  
Total Energy Release ◽  
Flare Energy ◽  
Accelerated Particles

Gamma-ray emission is the most direct diagnostic of energetic ions and relativistic electrons in solar flares. Analysis of solar flare gamma-ray data has shown: (i) ion acceleration is a major consequence of flare energy release, as the total flare energy in accelerated particles appears to be equipartitioned between ≳ 1 MeV/nucleon ions and ≳ 20 keV electrons, and amounts to an important fraction of the total energy release; (ii) there are flares for which over 50% of the energy is in a particles and heavier ions; (iii) in both impulsive and gradual flares, the particles that interact at the Sun and produce gamma rays are essentially always accelerated by the same mechanism that operates in impulsive flares, probably stochastic acceleration through gyroresonant wave particle interaction; and (iv) gamma-ray spectroscopy can provide new information on solar abundances, for example the site of the FIP-bias onset and the photospheric 3He abundance. We propose a new technique for the investigation of mass motion and mixing in the solar atmosphere: the observations of gamma-ray lines from long-term radioactivity produced by flare accelerated particles.

Observations of Energetic Electrons in Solar Flares

1990 ◽  
Vol 142 ◽  
pp. 438-438
Author(s):  
B. Lokanadham
Keyword(s):  
Particle Acceleration ◽  
Energy Release ◽  
Observational Data ◽  
Solar Flares ◽  
Energetic Electrons ◽  
X Ray

A study of the simultaneous observations of solar flares in optical, radio and X-ray bands is important in understanding the process of energy release and particle acceleration in the explosive phenomena of solar flares. In order to determine the characteristics of such energetic electrons in solar flares, a total number of 50 two-ribbon flares have been carefully selected during the period 1979-89 having simultaneous observational data in the optical, X-ray and radio bands.

Flaring Coronal Structures

1994 ◽  
Vol 144 ◽  
pp. 227-234
Author(s):  
T. Watanabe
Keyword(s):  
Solar Corona ◽  
Magnetic Reconnection ◽  
Time Scales ◽  
Solar Flares ◽  
Initial Phase ◽  
X Ray ◽  
Ionized Plasmas ◽  
First Time ◽  
Coronal Structures

AbstractThe highlights of the Japanese solar mission,Yohkoh, are presented, with emphasis on flaring structures in the solar corona. Definitive evidences of the magnetic reconnection in the solar corona are observationally confirmed for the first time. New insights in the location of hard X-ray sources are obtained. Completely blueshifted line emissions from highly ionized plasmas are seen at the very initial phase of solar flares. It is revealed that the solar corona is very dynamic in various time scales in X-ray intensities. Ample evidences of numerous flare-like activity like microflares and X-ray jets conclude that they are also the manifestation of the magnetic reconnection.

scholarly journals Fast Electrons in Small Solar Flares

1975 ◽  
Vol 68 ◽  
pp. 385-409 ◽  
Author(s):  
R. P. Lin
Keyword(s):  
Shock Wave ◽  
Solar Flares ◽  
Interplanetary Medium ◽  
The Other ◽  
The Sun ◽  
Fast Electrons ◽  
X Ray ◽  
Flare Energy ◽  
Electromagnetic Emissions ◽  
Detailed Characteristic

Because ∼5–100 keV electrons are frequently accelerated and emitted by the Sun in small flares, it is possible to define a detailed characteristic physical picture of these events. This review summarizes both the direct spacecraft observations of non-relativistic solar electrons, and observations of the X-ray and radio emission generated by these particles at the Sun and in the interplanetary medium. These observations bear on the basic astrophysical process of particle acceleration in tenuous plasmas. We find that in many small solar flares the ∼5–100 keV electrons accelerated during flash phase constitute the bulk of the total flare energy. Thus the basic flare mechanism in these flares essentially converts the available flare energy into fast electrons. These electrons may produce the other flare electromagnetic emissions through their interactions with the solar atmosphere. In large proton flares these electrons may provide the energy to eject material from the Sun and to create a shock wave which could then accelerate nuclei and electrons to much higher energies.

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