Some Astrophysical Aspects in the Studies of Solar Cosmic Rays

Modern Physics Letters A, 2005

We discuss the most recent developments in our understanding of the acceleration and propagation of cosmic rays up to the highest energies. In particular we specialize our discussion to three issues: 1) developments in the theory of particle acceleration at shock waves; 2) the transition from galactic to extragalactic cosmic rays; 3) implications of up-to-date observations for the origin of ultra high energy cosmic rays (UHECRs).

AIP Conference Proceedings, 2002

In 1990's Very High Energy Gamma-ray Astrophysics has dramatically advanced due to the Imaging AirČerenkov Telescopes(IACTs). After the first detection of TeV gamma-ray emission from the Crab nebula in 1989, several type of TeV gamma-ray sources, Active Galactic Nuclei(AGN), young pulsar, and SuperNova Remnant(SNR), have been detected. In those discoveries, recent detections of both synchrotron Xrays and TeV gamma-ray emissions from several SNRs are very significant. SNR has been widely believed to be an unique candidate of galactic cosmic-ray origin since the beginning of cosmic-ray physics, whereas little observational evidences have been reported so far. Those are expected to be a clue of not only the galactic cosmic-ray origin but also the understanding of the particle acceleration due to a diffusive shock. Here I present the recent results obtained by our group, CANGAROO, about the evidences of electron and proton acceleration in SNRs.

We discuss solar and interplanetary aspects concerning the observations and interpretation of two relativistic components of solar cosmic rays (SCRs). The modeling analysis of 30 large GLEs for the period of 1956-2006 by the data of the worldwide network of neutron monitors clearly revealed existence of two distinct SCR populations (components): the early pulse-like intensity increase with exponential energy spectrum (prompt component, PC), and the late gradual increase with a softer energy spectrum of the power-law form (delayed component, DC). The results of our analysis of available data and a number of theoretical arguments rule out an idea of interplanetary propagation as the origin for these two components. Most likely, they are formed in the multiple processes of particle acceleration in the solar atmosphere. We argue in favour of two-source model for PC and DC generation. The exponential spectrum for prompt component may be an evidence of acceleration by electric fields arising in the reconnecting current sheets in the corona. The possible source of delayed component is most likely stochastic acceleration at the MHD turbulence in expanding flare plasma.

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021)

Physics International, 2012

The origin and acceleration theories of Ultrah High Energy Cosmic Rays (UHECRs) are still mesterious problem in modern physics and astrophysics. The acceleration of ultra high energy cosmic rays is conjectured to occur through interactions with electromagnetic fields in different astrophysical objects, like magnetic matter clumps, besides the well-known shock waves and elastic Fermi mechanisms. Based on this model, a considerable portion of the dynamics, that derives a charged particle parallel to a magnetic field B and under the influence of a force F, is assumed to be composed of acceleration by a non-magnetic force F || and a gyromotion along B direction plus drifts in the direction of F ⊥. The model and its formalism are introduced, section 2 and section 3. Various examples for drift motions and accelerating forces are suggested, section 4. The configuration of the cosmic electromagnetic in different astophysical plasma aspects could play intrinsic role in the acceleration process of UHECRs. In a forthcoming work, a quantitative estimation of the energy gained by charged cosmic rays in various astrophysical objects will be evaluated.

Astrophysical sources are extremely efficient accelerators. Some sources emit photons up to multi-TeV energies, a signature of the presence, within them, of particles with energies much higher than those achievable with the largest accelerators on Earth. Even more compelling evidence comes from the study of Cosmic Rays, charged relativistic particles that reach the Earth with incredibly high energies: at the highest energy end of their spectrum, these subatomic particles are carrying a macroscopic energy, up to a few Joules. Here I will address the best candidate sources and mechanisms as cosmic particle accelerators. I will mainly focus on Galactic sources such as Supernova Remnants and Pulsar Wind Nebulae, which being close and bright, are the best studied among astrophysical accelerators. These sources are held responsible for most of the energy that is put in relativistic particles in the Universe, but they are not thought to accelerate particles up to the highest individual ene...

Physica Scripta

Some general features of cosmic ray acceleration are summarized along with some inferences that can be drawn concerning the origin of the UHE component. The UHE luminosity density is found to be similar to that derived for GeV cosmic rays and its slope suggests a distinct origin. Reports of clustering on small angular scale, if confirmed, would rule out most proposed source models. More generally, it is argued that the highest energy particles can only be accelerated in sites that can induce an EMF E > ∼ 3 × 10 20 V and an associated power L min > ∼ E 2 /Z ∼ 10 39 W, where Z is the characteristic, electrical impedance, typically < ∼ 100Ω. Shock acceleration, unipolar induction and magnetic flares are the three most potent, observed, acceleration mechanisms and radio jet termination shocks, γ-ray blast waves, dormant black holes in galactic nuclei and magnetars are the least implausible, "conventional" manifestations of these mechanisms that have been invoked to explain the UHE cosmic rays. Each of these models presents problems and deciding between these and "exotic" origins for UHE cosmic rays, including those involving new particles or defects will require improved statistical information on the energies, arrival times and directions, as should be provided by the Auger project.

Nuclear Physics B - Proceedings Supplements, 1991

Journal of Geophysical Research, 1971

Murray et al. [1971] reported an observation in which a feature or 'kink' in the kinetic-energy spectra of solar cosmic rays from a solar burst was seen to decrease from 3.4 to 2.4 Mev over a period of 3 days. They assumed diffusion to be small and concluded that the decay time constant of this event (210 --10 hours) was not in accordance with energy losses due to adiabatic deceleration. In a companion paper, Jokipii [1971] proposed Fermi acceleration processes to account for the discrepancy.

2010

Based on the generic acceleration model, which suggests different types of electromagnetic interactions between the cosmic charged particles and the different configurations of the electromagnetic (plasma) fields, the ultra high energy cosmic rays are studied. The plasma fields are assumed to vary, spatially and temporally. The well-known Fermi accelerations are excluded. Seeking for simplicity, it is assumed that the energy loss due to different physical processes is negligibly small. The energy available to the plasma sector is calculated in four types of electromagnetic fields. It has been found that the drift in a time--varying magnetic field is extremely energetic. The energy scale widely exceeds the Greisen-Zatsepin-Kuzmin (GZK) cutoff. The polarization drift in a time--varying electric field is also able to raise the energy of cosmic rays to an extreme value. It can be compared with the Hillas mechanism. The drift in a spatially--varying magnetic field is almost as strong as ...

The Astronomy and Astrophysics Review, 2013

One century ago Viktor Hess carried out several balloon flights that led him to conclude that the penetrating radiation responsible for the discharge of electroscopes was of extraterrestrial origin. One century from the discovery of this phenomenon seems to be a good time to stop and think about what we have understood about Cosmic Rays. The aim of this review is to illustrate the ideas that have been and are being explored in order to account for the observable quantities related to cosmic rays and to summarize the numerous new pieces of observation that are becoming available. In fact, despite the possible impression that development in this field is somewhat slow, the rate of new discoveries in the last decade or so has been impressive, and mainly driven by beautiful pieces of observation. At the same time scientists in this field have been able to propose new, fascinating ways to investigate particle acceleration inside the sources, making use of multifrequency observations that range from the radio, to the optical, to X-rays and gamma rays. These ideas can now be confronted with data.

Journal of Experimental and Theoretical Physics, 2019

Based on the theory of diffusive shock acceleration of charged particles, we have investigated the spectra of protons recorded in the solar cosmic ray event near the Earth's orbit on November 22, 1977 (ground level enhancement no. 30, GLE30). The proton flux data from the CPME instrument installed on the IMP-8 spacecraft and the worldwide network of neutron monitors have been used to analyze the event. Using GLE30 as an example, we have shown for the first time that solar cosmic rays of relativistic energies can be produced by a shock wave with a relatively low speed of 560 km s-1 in the lower solar corona at a distance up to 1.6 (is the solar radius) within 615 s. The calculated proton spectra satisfactorily reproduce the measurements in the Earth's orbit.

Experimental Astronomy, 2012

Energetic particles are critical components of plasma populations found throughout the universe. In many cases particles are accelerated to relativistic energies and represent a substantial fraction of the total energy of the system, thus requiring extremely efficient acceleration processes. The production of accelerated particles also appears coupled to magnetic field evolution in astrophysical plasmas through the turbulent magnetic fields produced by diffusive shock acceleration. Particle acceleration is thus a key component in helping to understand the origin and evolution of magnetic structures in, e.g. galaxies. The proximity of the Sun and the range of high-resolution diagnostics available within the solar atmosphere offers unique opportunities to study the processes involved in particle acceleration through the use of a combination of remote sensing observations of the radiative signatures of accelerated particles, and of their plasma and magnetic environment. The SPARK concept targets the broad range of energy, spatial and temporal scales over which particle acceleration occurs in the solar atmosphere, in order to determine how and where energetic particles are accelerated. SPARK combines highly complementary imaging and spectroscopic observations of radiation from energetic electrons, protons and ions set in their plasma and magnetic context. The payload comprises focusing-optics X-ray imaging covering the range from 1 to 60 keV; indirect HXR imaging and spectroscopy from 5 to 200 keV, γ -ray spectroscopic imaging with high-resolution LaBr 3 scintillators, and photometry and source localisation at far-infrared wavelengths. The plasma environment of the regions of acceleration and interaction will be probed using soft X-ray imaging of the corona and vector magnetography of the photosphere and chromosphere. SPARK is designed for solar research. However, Exp Astron (2012) 33:237-269 239 in addition it will be able to provide exciting new insights into the origin of particle acceleration in other regimes, including terrestrial gamma-ray flashes (TGF), the origin of γ -ray bursts, and the possible existence of axions.

2001

Nuclear Physics B - Proceedings Supplements, 2013

One century ago Viktor Hess carried out several balloon flights that led him to conclude that the penetrating radiation responsible for the discharge of electroscopes was of extraterrestrial origin. One century from the discovery of this phenomenon seems to be a good time to stop and think about what we have understood about Cosmic Rays. The aim of this review is to illustrate the ideas that have been and are being explored in order to account for the observable quantities related to cosmic rays and to summarize the numerous new pieces of observation that are becoming available. In fact, despite the possible impression that development in this field is somewhat slow, the rate of new discoveries in the last decade or so has been impressive, and mainly driven by beautiful pieces of observation. At the same time scientists in this field have been able to propose new, fascinating ways to investigate particle acceleration inside the sources, making use of multifrequency observations that range from the radio, to the optical, to X-rays and gamma rays. These ideas can now be confronted with data.