scholarly journals Turbulent Acceleration in Solar Flares

1994 ◽  
Vol 142 ◽  
pp. 623-630
Author(s):  
D. B. Melrose
Keyword(s):  
Solar Flares ◽  
Gamma Ray ◽  
Low Frequency ◽  
Impulsive Phase ◽  
Primary Energy ◽  
Nonthermal Electron ◽  
Relativistic Electrons ◽  
Mhd Turbulence ◽  
Narrow Channels ◽  
Current Instability

AbstractTurbulent acceleration in the impulsive phase of solar flares is reviewed, with the emphasis on bulk energization of nonrelativistic electrons and prompt acceleration of the gamma-ray emitting nonrelativistic ions and relativistic electrons. The primary energy release in a flare cannot be due to collisional dissipation. Anomalous resistivity requires that the current flows in many narrow channels with the current density above threshold for current instability. The bulk energization of the electrons is due to the damping of low-frequency electrostatic turbulence generated by the current instability. This turbulence also limits the rate a nonthermal electron tail forms due to runaway acceleration. Stochastic and gyroresonant acceleration by MHD turbulence are discussed briefly, emphasizing the need for preacceleration. Stochastic acceleration is favorable for the gamma-ray emitting particles only if an adequated source of the MHD turbulence can be identified.Subject headings: acceleration of particles — MHD — Sun: flares — turbulence

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.

scholarly journals Characterization of Selected Solar Radio Bursts Based on Solar Activity Detected by e-CALLISTO (Malaysia)

2014 ◽  
Vol 32 ◽  
pp. 144-154
Author(s):  
Zety Sharizat Hamidi ◽  
N.N.M. Shariff ◽  
C. Monstein
Keyword(s):  
Solar Flare ◽  
Coronal Mass Ejections ◽  
Solar Radio ◽  
Low Frequency ◽  
Weather Condition ◽  
Impulsive Phase ◽  
Primary Energy ◽  
Radio Bursts ◽  
Solar Radio Bursts ◽  
Solar Burst

One of the main reasons to study more about the dynamics of solar radio bursts is because solar these bursts can interfere with the Global Positioning System (GPS) and communications systems. More importantly, these bursts are a key to understand the space weather condition. Recent work on the interpretation of the low frequency region of a main solar burst is discussed. Continuum radio bursts are often related to the solar activities such as an indication of the formation of sunspot, impulsive phase of solar flares and Coronal Mass Ejections (CMEs) and their frequencies correspond to the densities supposed to exist in the primary energy release volume. Specifically, solar burst in low frequency play an important role in interpretation of Sun activities. In this work, we have selected few solar bursts that successfully detected by our station at the National Space Centre, Banting Selangor. Our objective is to correlate the solar burst with Sun activities by looking at the main sources that responsibility with the trigger of solar burst. It is found that type II burst is dominant with Coronal Mass Ejections (CMEs), type III burst associated with solar flare, IV burst with the formation of active region and type U burst high solar flare. We believed that this work is a good start to monitor Sun’s activities in Malaysia as equatorial country.

scholarly journals Fermi Large Area Telescope observation of high-energy solar flares: constraining emission scenarios

2015 ◽  
Vol 11 (S320) ◽  
pp. 51-56
Author(s):  
Nicola Omodei ◽  
Melissa Pesce-Rollins ◽  
Vahè Petrosian ◽  
Wei Liu ◽  
Fatima Rubio da Costa ◽  
...  
Keyword(s):  
Solar Flares ◽  
Gamma Ray ◽  
Solar Energetic Particle ◽  
Cosmic Ray ◽  
Impulsive Phase ◽  
High Energy ◽  
Solar Energetic Particle Event ◽  
Emission Scenarios ◽  
Large Area ◽  
Gamma Ray Emission

AbstractThe Fermi Large Area Telescope (LAT) is the most sensitive instrument ever deployed in space for observing gamma-ray emission >100 MeV. This has also been demonstrated by its detection of quiescent gamma-ray emission from pions produced by cosmic-ray protons interacting in the solar atmosphere, and from cosmic-ray electron interactions with solar optical photons. The Fermi-LAT has also detected high-energy gamma-ray emission associated with GOES M-class and X-class solar flares, each accompanied by a coronal mass ejection and a solar energetic particle event, increasing the number of detected solar flares by almost a factor of 10 with respect to previous space observations. During the impulsive phase, gamma rays with energies up to several hundreds of MeV have been recorded by the LAT. Emission up to GeV energies lasting several hours after the flare has also been detected by the LAT. Of particular interest are the recent detections of three solar flares whose position behind the limb was confirmed by the STEREO satellites. While gamma-ray emission up to tens of MeV resulting from proton interactions has been detected before from occulted solar flares, the significance of these particular events lies in the fact that these are the first detections of >100 MeV gamma-ray emission from footpoint-occulted flares. We will present the Fermi-LAT, RHESSI and STEREO observations of these flares and discuss the various emission scenarios for these sources.

scholarly journals Submillimeter and Far Infrared Emission from Solar Flares

1994 ◽  
Vol 154 ◽  
pp. 103-112
Author(s):  
Vahé Petrosian
Keyword(s):  
Brightness Temperature ◽  
Solar Flares ◽  
Gamma Ray ◽  
Far Infrared ◽  
Impulsive Phase ◽  
Infrared Emission ◽  
Synchrotron Emission ◽  
X Ray ◽  
Quiet Sun ◽  
Hot Plasma

The mechanisms for emission in the submillimeter and far-infrared (1011 and 1013 Hz) regions by solar flares and expected fluxes at these frequencies are described and evaluated. These inferences are based on observations of flare emission at other frequencies and on models for these emissions. In the impulsive phase, non-thermal synchrotron emission by electrons responsible for > 10 MeV gamma-ray emission can give rise to significant radiation in the 1011 to 1013 Hz region from large flares. Free-free or thermal gyrosynchrotron from the hot plasma responsible for the gradual soft X-ray emission can produce significant radiation in the 1011 to 1013 Hz range. However, only radiation in the lower end of this range would have a brightness temperature exceeding the quiet sun brightness.

scholarly journals High Energy Gamma-Ray Radiation Above 300 KeV Associated with Solar Activity

1975 ◽  
Vol 68 ◽  
pp. 341-359 ◽  
Author(s):  
E. L. Chupp ◽  
D. J. Forrest ◽  
A. N. Suri
Keyword(s):  
Experimental Data ◽  
Solar Flares ◽  
Gamma Ray ◽  
Impulsive Phase ◽  
Theoretical Work ◽  
High Energy ◽  
Energy Gamma ◽  
Charged Secondary ◽  
Rule Out ◽  
Made In

The present status of our knowledge concerning the production of gamma-ray lines and continuum during the impulsive phase of solar flares is reviewed. Our data in this field is based solely on the OSO-7 observations made in 1972, August 4 and August 7. The experimental data will be reviewed. These observations along with theoretical work of Ramaty and Lingenfelter (1973a, b) and the charged secondary observations of the Chicago group (Anglin et al., 1973) lead to the investigation of different hypothetical models to explain the production of neutral and charged secondaries in the solar atmosphere. At the present time it is not possible to rule out the preflare and postflare accumulation models if all the data is considered. We will discuss the outstanding experimental questions to be answered in future investigations.

scholarly journals Acceleration, Transport of and Radiation by Electrons in Impulsive Phase of Flares

1990 ◽  
Vol 142 ◽  
pp. 391-402
Author(s):  
Vahé Petrosian
Keyword(s):  
Solar Flares ◽  
Gamma Ray ◽  
Impulsive Phase ◽  
Angle Distribution ◽  
Radio Emissions ◽  
Accelerated Electrons ◽  
Set Constraints ◽  
The Past ◽  
Flare Plasma

I review here results of works that we have carried out over the past few years in connection with various manifestations of the impulsive phase of solar flares. The primary goal of this work has been the determination of the characteristics of the accelerated electrons. We take into account various possible interactions that electrons suffer as they traverse the flare plasma and evaluate the expected radiation via several mechanisms. The comparison of these with the observed x-ray, gamma-ray and radio emissions allows us to set constraints on the characteristics of the accelerated electrons and on some properties of the flare plasma. I will describe some of the results we have derived from comparisons with SMM and other observations of flares during the past solar cycle. In particular, I will show that we can set limits on the range and distribution of the accelerated electron spectrum and pitch angle distribution, and on the column depth and field convergence rate of the flaring loop. More complete data and high spatial resolution and polarization observations could be very useful for furthering this kind of work.

scholarly journals Coronal Response to Energy Release During Solar Flares

1986 ◽  
Vol 7 ◽  
pp. 731-738
Author(s):  
Ester Antonucci
Keyword(s):  
High Resolution ◽  
Energy Release ◽  
Solar Flares ◽  
Solar Maximum ◽  
Impulsive Phase ◽  
Primary Energy ◽  
Release Process ◽  
X Ray ◽  
The Past ◽  
Flare Region

AbstractThe observations obtained with high resolution spectrometers flown in the past solar maximum, in the years 1979-1981, have shown that the soft x-ray plasma during the impulsive phase of solar flares is characterized by upflows. as well as by isotropic flows, at velocities of a few hundred km s-1. Isotropic flows can be directly related to the primary energy release process. While, upflows are an indication of chromospheric material heated to coronal temperatures and evaporating along the magnetic fluxtubes; they are therefore related to the development of the coronal soft x-ray source in the flare region.

scholarly journals Integrating of GIS and GPS for ionospheric perturbations in D- and F-layers using VLF receiver

2020 ◽  
Vol 26 (1) ◽  
pp. 547-560
Author(s):  
Bobomurat Ahmedov ◽  
Bahadir Mirzaev ◽  
Farmon Mamatov ◽  
Dadakhon Khodzhaev ◽  
Mukhiddin Julliev
Keyword(s):  
Central Asia ◽  
Solar Flares ◽  
Gamma Ray ◽  
Lightning Discharge ◽  
Low Frequency ◽  
Regular Monitoring ◽  
D Region ◽  
The Times ◽  
Electromagnetic Precursors ◽  
The Waves

Regular monitoring of the D- and F-layers of ionosphere over Central Asia territory is being performed on the permanent basis starting year 2008 when one Very Low Frequency (VLF) receiver and two SuperSID receivers were provided to Uzbekistan IHY cite by Stanford University. The results obtained at Tashkent IHY (International Heliophysical Year) station are applied to earthquake electromagnetic precursors, lightning, and Solar flares and to ionospheric disturbances originating from gamma ray flares of Soft Gamma-Ray Repeaters. Regular monitoring of the D-layer of ionosphere over Central Asia territory has been performed on the permanent basis. Several Solar events are observed and the analysis has shown that there is simultaneous correlation between the times of change of amplitude of the waves and the Solar flares. Features of the lightning discharge generated by radio atmospherics are studied and its effectiveness in D-region ionosphere diagnostics is examined. We have mainly analyzed GPS derived TEC disturbances from two GPS stations located in Tashkent and Kitab, for possible earthquake ionospheric precursors. The solar and geomagnetic conditions were quiet during occurrence of the selected more than 30 earthquakes. We produced TEC time series over both sites and apply them to detect anomalous TEC signals preceding or accompanying the earthquakes. The results show anomalous enhancements which are examined in the earthquakes.

scholarly journals On a Possible Origin of the Gamma-ray Excess around the Galactic Center

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1432
Author(s):  
Dmitry O. Chernyshov ◽  
Andrei E. Egorov ◽  
Vladimir A. Dogiel ◽  
Alexei V. Ivlev
Keyword(s):  
Dark Matter ◽  
Gamma Rays ◽  
Molecular Clouds ◽  
Alternative Explanation ◽  
Gamma Ray ◽  
Galactic Center ◽  
The Self ◽  
Large Area ◽  
Mhd Turbulence ◽  
The Standard Model

Recent observations of gamma rays with the Fermi Large Area Telescope (LAT) in the direction of the inner galaxy revealed a mysterious excess of GeV. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs) generation and propagation with a peak in the spectrum around a few GeV. Popular interpretations of this excess are that it is due to either spherically distributed annihilating dark matter (DM) or an abnormal population of millisecond pulsars. We suggest an alternative explanation of the excess through the CR interactions with molecular clouds in the Galactic Center (GC) region. We assumed that the excess could be imitated by the emission of molecular clouds with depleted density of CRs with energies below ∼10 GeV inside. A novelty of our work is in detailed elaboration of the depletion mechanism of CRs with the mentioned energies through the “barrier” near the cloud edge formed by the self-excited MHD turbulence. This depletion of CRs inside the clouds may be a reason for the deficit of gamma rays from the Central Molecular Zone (CMZ) at energies below a few GeV. This in turn changes the ratio between various emission components at those energies and may potentially absorb the GeV excess by a simple renormalization of key components.

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