Magnetospheric protons and electrons encountered by the moon in the plasma sheet

During its passage through the geomagnetic tail, the Moon encounters the plasma sheet. Properties of plasma sheet electrons and protons, first detected at lunar distances by Explorer 35, are described. The electrons have a rapidly fluctuating non-Maxwellian energy distribution with a mean energy of several hundred electron volts and density ç 0.2 cm^?3. The protons, of energy ç 1 keV, were usually detected above the instrument background when flowing towards the Earth at ç 200 km s^?1. Implications for migration of grains on the lunar surface are also pointed out and it is suggested that strong terrestrial polar winds in the early history of the Earth-Moon system may have caused some erosion of the Earth-facing side of the Moon, and that gravitational shielding of interplanetary rock flux by the Earth may also be an explanation of the relative smoothness of the front side.     

On the storage of high-energy protons in the solar corona: The cyclotron instability

We consider the problem of long-time storage of high-energy protons, accelerated in the process of a flare, in coronal magnetic traps. From the viewpoint of the storage, one of the most important plasma instabilities is the kinetic cyclotron instability of the Alfvén waves. We carry out a detailed theoretical analysis of the instability for typical conditions of the solar corona. It is the refraction of the Alfvén waves in combination with a drastic decrease of the instability growth rate with an increase of the angle between the directions of the wave vector and the stationary magnetic field that leads to the possibility of the long-term storage of the flare protons. Sufficient conditions of the storage are determined.     

A possible mechanism for producing cosmic gamma ray bursts

In this paper, we propose a model to explain the energy supply of cosmic γ-ray bursts by means of magnetic energy annihilation in neutral sheets formed in local active regions on magnetic white dwarfs. According to this model the instability process in the plasma consists of two phases, a thermal explosive phase and a steady annihilation phase. The magnetic energy stored in the local source is efficiently converted into kinetic energy and the energy dissipation is at a rate consistent with the observations. With the rapid increase of anomalous resistivity a plasma turbulence field is set up which can immediately be coupled with fast electrons in the Maxwellian high energy tail. The relativistic electrons are then produced within a time as short as 10⁻⁸ sec., which is not in conflict with the fast ascent of brief “spikes” of gamma rays. The calculated results indicate that the γ-rays can also be emitted through synchrotron radiation by the accelerated electrons moving around the magnetic field.While many details of this theoretical model remain to be cleared up, the present point of view may be taken as a promising basis for future work.     

The role of high-energy protons and electrons in powering the solar white-light flare emission

The temporal histories of three intense and impulsive gamma-ray flares, for which also white-light emission had been observed, are analyzed in order to test the role of high-energy particles- electrons and protons - in powering the optical continuum. By comparing the light curves at optical wavelengths and at X-ray and gamma-ray energies, we find a good correlation of the main peaks of emission, which confirms previous findings that the continuum emission is most likely associated with the energy loss of energetic particles. The power carried by the greater-than-50 keV nonthermal electrons may be sufficient to balance the optical emission. The power residing in protons or ions with energies greater than 1 MeV depends largely on the spectral shape of the particle distribution. Only if this is similar to a power law, may the energy carried by these high-energy particles be sufficient to balance the white-light flare emission.Operated by the Association of Universities for Research in Astronomy, Inc., under cooperative agreement with the National Science Foundation. Partial support for the National Solar Observatory is provided by the USAF under a Memorandum of Understanding with the NSF.     

Circular radiation by monopole in plasma

The aim of this paper has been to study circular radiation emitted by cosmic magnetic monopole. A formula of the radiation is derived. By use of this formula, a basic feature of the radiation spectrum is described. It is shown that the radiation spectrum of magnetic monopole is very different from that of a charged particle, which gives a possibility to examine the magnetic monopole.     

Searching for curvature pion radiation from protons in strongly magnetized pulsars

By using rather conservative estimates based on the simplest polar cap model, we search the ATNF Pulsar Catalogue for strongly magnetized stars that could accelerate relativistic protons up to the curvature pion production threshold. The best candidate turns out to be the 16 ms pulsar J0537-6910, but the corresponding characteristic parameter χ=a/m _p is yet too small to give origin to observable signals. We show that, for pulsars with period P≈1 ms, a surface polar magnetic field B≈10¹² G is required in order to induce detectable curvature pion radiation from accelerated protons in the magnetosphere. Some other emission processes are also considered.     

A collective radiation mechanism for the core emission of pulsars

A study of imperfect fluid interacting with the gravitational field for spherically-symmetric Robertson-Walker metric has been carried out. Exact solutions of the field equations of viscous fluid have been obtained under different equations of state. The corresponding physical interpretations of the solutions have been investigated. It has been shown that the occurrence of Big-Bang does not take place when the viscous fluid as only source term interacts with the gravitational field at the initial stages.     

Cross-section for the dissociative photoionization of hydrogen by 584 Å radiation: The formation of protons in the Jovian ionosphere

The cross-section for dissociative photoionization of hydrogen by 584 Å radiation has been measured, yielding a value of 5 × 10^?20 cm². The process can be explained as a transition from the $\text{X}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ ground state to a continuum level of the $\text{X}{}^2\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ ionized state of H₂ The branching ratio for proton (H⁺) vs molecular ion (H₂⁺) production at this energy is 8 × 10^?3. This process is quite likely an important source of protons in the Jovian ionosphere near altitudes where peak ionization rates are found.     

A coherent radiation mechanism for type IV dm radio bursts

An interpretation is presented of the decimetric type IV continuum with fine structure on March 6, 1972 and of the corresponding source region, in terms of ?erenkov plasma radiation and alternatively of synchrotron radiation, both in case of coherent and incoherent generation. If the magnetic field strength in the source region is a few gauss, in a stationary situation a loss cone instability develops which generates electron plasma waves coherently. The amount of energetic electrons required for consecutive induced scattering of the plasma waves at the thermal ions into electromagnetic waves is less than in case of synchrotron radiation. It is concluded that the former mechanism provides the explanation of type IV continua with fine structure such as intermediate drift bursts and sudden reductions of the continuum level.     

A coherent radiation mechanism for type IV solar radio bursts

A new coherent radiation mechanism, involving nonlinear interaction of whistler solitons with upperhybrid waves, excited by energetic electrons of energies of 10 keV–100 keV, is proposed for type IV solar bursts of both moving (type IV M) and stationary (type IV S) types. We show that the type IV M bursts occur when the interaction of whistler solitons and upperhybrid waves takes place in the coronal transients whereas the type IV S bursts originate provided this interaction takes place in stationary loops where density has been increased. The emitted radiation is right-hand circularly polarized with 100% polarization. Increase of brightness temperature, T _b , at lower frequencies and also its decrease, at all frequencies, with the passage of time is predicted for type IV M bursts; this agrees fully with the observations. Furthermore, the decrease of T _b , with time for stationary type IV component, is easily explained if the source which supplies energetic electron to the loop, becomes weaker with time.     

A note on the emission mechanism of storm radiation

A new mechanism has been proposed for the continuum and burst components of solar storm radiation by Genkin, Erukhimov, and Levin (1989a, b). In this paper, we point out that while bursts can be explained by the proposed mechanism of scattering on plasma turbulence generated density fluctuations, the continuum cannot be explained by sattering on thermal ion density fluctuations. The reason is, under the same coronal conditions, second harmonic emissions will dominate over the fundamental emission due to scattering on thermal ion density fluctuations in contradiction to observations. We also note that the range of plasma wave densities needed for this mechanism may not be realistic for the case of plasma wave generation due to loss cone instability. It is further argued that coalescence of plasma waves with low-frequency waves still seems to be the plausible mechanism.     

A new scenario for impulsive bursts of hard electromagnetic radiation in space plasma

We discuss the peculiarities of fast magnetic reconnection in the essentially nonequilibrium magnetosphere of a compact relativistic object: a neutron star, a magnetar, a white dwarf. Such a magnetosphere is produced by the interaction of a large-amplitude shock wave with a strong stellar magnetic field. We present an analytical solution of the generalized two-dimensional problem on the magnetosphere’s structure, the shape of its boundary, and the direct and reverse currents in a reconnecting current sheet. The uncompensated magnetic force acting on the reverse current is determined. Characteristic parameters of the nonequilibrium magnetosphere of compact stellar objects are estimated. We show that the excess magnetic energy of the magnetosphere is comparable to the mechanical energy brought into it by the shock at the instant of impact. The possibility of particle acceleration to enormous energies is discussed.     

The radiation of energy by a current in a plasma

The derivation of the differential power emitted in any given direction by a current J in a linear, homogeneous and non-absorbing plasma is reviewed in detail. The conventional derivation is shown to give the poweremitted; a formalism for the powerreceived is established by evaluating the Poynting vector in terms of the far field. It is pointed out that the two power expressions differ because the same energy dE is emitted in a time dt _e but received over a different time dt _r . Moreover, a careful scrutiny of both the formalism for the power emission and for the power reception exposes implicit assumptions which do not hold if the plasma is anisotropic. The necessary steps for establishing a valid formalism for anisotropic media are briefly sketched.     

A revised version of synchrotron radiation in a magnetized plasma

We analyze the propagation features of synchrotron radiation of a charge moving with a gyrating helix trajectory (3-dimensional) in a magnetoplasma. We found that a new factor (1+ cot ) should be included into the relevant spectrum radiation formulae and the usual relativistic factor has to be modified as , ifv <v _g , the radiative energy are more concentrated along the velocity of the moving charge; but ifv>v _g, the direction of maximum energy cone deviates from the direction of the moving charge.     

A role of cosmic rays in generation of radio and optical radiation by plasma mechanisms

The radiation of ultrarelativistic particles is examined in a quasi-uniform magnetic field superimposed by a wide spectrum of magnetic, electric, and electron density inhomogeneities created in a turbulent plasma. The radiation spectrum from a particle of a given energy is shown to acquire a high-frequency power-law tail with the same spectral index as the index of small-scale turbulence. For a power-law spectrum of ultrarelativistic electrons, dN()/d ~ ^–, with a cut-off at some energy _max, the radiation spectrum consists of a few power-law ranges; the radiation intensity may suffer jumps at frequencies which separate these ranges.In the high-frequency range the spectral index is determined by small-scale magnetic and electric fields. At intermediate frequencies the main contribution comes from the synchrotron radiation in a large-scale field; the radiation spectrum has an index =(–1)/2. The same index may be produced by large-scale Langmuir waves. At lower frequencies the radiation spectrum increases owing to the transition radiation caused by electron density fluctuations; in this case the spectral index is equal to +1–.The possibility of diagnostics of high-frequency cosmic plasma turbulence from radiation of high-energy particles is discussed. It is shown that the proposed theory may explain some features in the spectra of several cosmic objects.     

The role of protons of the radiation belts in the generation of Pc 3–5

A new theory of the Alfvén wave generation in inhomogeneous finite β two component plasma is developed ($\text{β =}\text{8πρ}\text{β}{}_0{}^2$, ρ and B₀ are plasma pressure and unperturbed magnetic field, respectively). The analysis was carried out for these waves both for long wave approximation kρ_i ? 1 as well as for $\text{kρ}{}_{\mathrm{i}}\text{? 1}$ (k and ρ_i are wave vector and larmor radius of protons). The influence of the loss-cone on the development of the instability is considered. The theory is applied to explain the generation mechanism of Pc 3–5.     

A dominant role for protons at the onset of solar flares

The energetics of the onset of the impulsive phase of solar flares are examined on the premise that a single acceleration mechanism is operating in the corona. From considerations of recent observations of plasma turbulence and upflows, and nuclear gamma-rays it is concluded that a model where the bulk of the energy resides in a non-thermal electron beam with a low energy cut-off at 20–25 keV is incompatible with many of the observations. Conversely, a model where the bulk of the energy resides in non-thermal protons is consistent with the majority, if not all, of the observations. It is suggested that the bulk of the energy in the impulsive phase is initially transferred to 10²–10³ keV protons. Acceleration by a series of small shocks is an energy transfer mechanism which gives particles increments in velocity rather than energy and would naturally favour protons over electrons. An important consequence of this result is that the hard X-ray burst must be thermal. At this time the precise mechanism for thermal X-ray production is unclear; however recent theoretical plasma physics results have indicated promising avenues of research in this context.     

Analysis of the effect of focusing of electromagnetic radiation by galactic microlenses in a wide long-wave range

In accordance with contemporary notions, approximately at 96% of all mass of the Universe is invisible in the form of missing mass (23%) and dark energy (73%). Missing mass can manifest itself by means of interaction with electromagnetic radiation, which is created by gravitational fields of compact galactic bodies. As possible candidates for the role of microlenses, we examine substars, white dwarves, and main-sequence stars. We also take into account the fact that some of these microlenses may have the dense gas atmospheres. On the basis of model approximations, we have conducted an analysis of the focusing features of microlenses and have obtained numerical estimates for the coefficient of intensification in a wide long-wave range (from optical to radio). A multilateral investigation of the characteristics of an individual microlens is necessary to correctly interpret observation data.