Evidence For Particle Acceleration Research Articles

The relativistic solar particle event on 28 October 2021: Evidence of particle acceleration within and escape from the solar corona

Aims.We analyse particle, radio, and X-ray observations during the first relativistic proton event of solar cycle 25 detected on Earth. The aim is to gain insight into the relationship between relativistic solar particles detected in space and the processes of acceleration and propagation in solar eruptive events.Methods.To this end, we used ground-based neutron monitor measurements of relativistic nucleons and space-borne measurements of electrons with similar speed to determine the arrival times of the first particles at 1 AU and to infer their solar release times. We compared the release times with the time histories of non-thermal electrons in the solar atmosphere and their escape to interplanetary space, as traced by radio spectra and X-ray light curves and images.Results.Non-thermal electrons in the corona are found to be accelerated in different regions. Some are confined in closed magnetic structures expanding during the course of the event. Three episodes of electron escape to the interplanetary space are revealed by groups of decametric-to-kilometric type III bursts. The first group appears on the low-frequency side of a type II burst produced by a coronal shock wave. The two latter groups are accompanied at higher frequencies by bursts with rapid drifts to both lower and higher frequencies (forward- or reverse-drifting bursts). They are produced by electron beams that propagate both sunward and anti-sunward. The first relativistic electrons and nucleons observed near Earth are released with the third group of type III bursts, more than ten minutes after the first signatures of non-thermal electrons and of the formation of the shock wave in the corona. Although the eruptive active region is near the central meridian, several tens of degrees east of the footpoint of the nominal Parker spiral to the Earth, the kilometric spectrum of the type III bursts and the in situ detection of Langmuir waves demonstrate a direct magnetic connection between the L1 Lagrange point and the field lines onto which the electron beams are released at the Sun.Conclusions.We interpret the forward- and reverse-drifting radio bursts as evidence of reconnection between the closed expanding magnetic structures of an erupting flux rope and ambient open magnetic field lines. We discuss the origin of relativistic particles near the Earth across two scenarios: (1) acceleration at the CME-driven shock as it intercepts interplanetary magnetic field lines rooted in the western solar hemisphere and (2) an alternative where the relativistic particles are initially confined in the erupting magnetic fields and get access to the open field lines to the Earth through these reconnection events.

Search for muon neutrinos from the gravitational wave event GW170817 at the Baksan Underground Scintillation Telescope

Using data of the Baksan Underground Scintillation Telescope we have searched for muon neutrinos and antineutrinos with energies above 1 GeV coinciding with the gravitational wave (GW) event GW170817 that was recorded on August 17, 2017, by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and Advanced Virgo observatories. This is the first detection of the new type of events occurring as a result of a merger of two neutron stars in a binary system. A short gamma-ray burst (GRB) GRB170817A accompanying this event is evidence of particle acceleration in the source whose precise position was determined by detection of the subsequent optical signal. No neutrino signals were found with the Baksan Underground Scintillation Telescope in the interval ±500 s around the moment of the gravitational wave event GW170817, as well as during the next 14 days. The upper limits on integral fluxes of muon neutrino and antineutrino from the source are derived.

Evidence of Particle Acceleration in the Superbubble 30 Doradus C with NuSTAR

Abstract We present evidence of diffuse, non-thermal X-ray emission from the superbubble 30 Doradus C (30 Dor C) using hard X-ray images and spectra from NuSTAR observations. For this analysis, we utilize data from a 200 ks targeted observation of 30 Dor C as well as 2.8 Ms of serendipitous off-axis observations from the monitoring of nearby SN 1987A. The complete shell of 30 Dor C is detected up to 20 keV, and the young supernova remnant MCSNR J0536−6913 in the southeast of 30 Dor C is not detected above 8 keV. Additionally, six point sources identified in previous Chandra and XMM-Newton investigations have hard X-ray emission coincident with their locations. Joint spectral fits to the NuSTAR and XMM-Newton spectra across the 30 Dor C shell confirm the non-thermal nature of the diffuse emission. Given the best-fit rolloff frequencies of the X-ray spectra, we find maximum electron energies of ≈70–110 TeV (assuming a B-field strength of 4 μG), suggesting 30 Dor C is accelerating particles. Particles are either accelerated via diffusive shock acceleration at locations where the shocks have not stalled behind the Hα shell, or cosmic-rays are accelerated through repeated acceleration of low-energy particles via turbulence and magnetohydrodynamic waves in the bubble’s interior.

Early multiwavelength analysis of the recurrent nova V745 Sco

ABSTRACT In recent years, several nova explosions have been detected by Fermi/LAT at E > 100 MeV, mainly early after the explosion and for a short period of time. The first evidence of particle acceleration in novae was found in the 2006 eruption of RS Oph to explain the faster than expected deceleration of the blast wave. As a consequence, emission of high-energy gamma-rays mainly from neutral pion decay and inverse Compton scattering is expected. We aim to understand the early shock evolution, when acceleration of particles can take place, in nova explosions. To achieve this goal, we perform a multiwavelength study of the 2014 outburst of V745 Sco, a symbiotic recurrent nova similar to RS Oph. The analysis of early Swift/XRT observations, simultaneous to the tentative Fermi detection, is combined with Chandra and NuStar data, to get a global picture of the nova ejecta and the red giant wind evolution. Early radio and IR data are also compiled, providing information about the forward shock velocity and its magnetic field. The comparison with the plasma properties of RS Oph shows striking similarities, such as the skipping of the adiabatic phase occurring in supernova remnants, a hint of particle acceleration. The multiwavelength study of V745 Sco provides new insights into the evolution of the hot plasma in novae and its interaction with the circumstellar material, a powerful tool to understand the nature of the high-energy gamma-ray emission from symbiotic recurrent novae.

EVIDENCE FOR PARTICLE ACCELERATION TO THE KNEE OF THE COSMIC RAY SPECTRUM IN TYCHO ’S SUPERNOVA REMNANT

Supernova remnants (SNRs) have long been assumed to be the source of cosmic rays (CRs) up to the "knee" of the CR spectrum at 10^15 eV, accelerating particles to relativistic energies in their blast waves by the process of diffusive shock acceleration (DSA). Since cosmic ray nuclei do not radiate efficiently, their presence must be inferred indirectly. Previous theoretical calculations and X-ray observations show that CR acceleration modifies significantly the structure of the SNR and greatly amplifies the interstellar magnetic field. We present new, deep X-ray observations of the remnant of Tycho's supernova (SN 1572, henceforth Tycho), which reveal a previously unknown, strikingly ordered pattern of non-thermal high-emissivity stripes in the projected interior of the remnant, with spacing that corresponds to the gyroradii of 10^14 - 10^15 eV} protons. Spectroscopy of the stripes shows the plasma to be highly turbulent on the (smaller) scale of the Larmor radii of TeV energy electrons. Models of the shock amplification of magnetic fields produce structure on the scale of the gyroradius of the highest energy CRs present, but they do not predict the highly-ordered pattern we observe. We interpret the stripes as evidence for acceleration of particles to near the knee of the CR spectrum in regions of enhanced magnetic turbulence, while the observed highly ordered pattern of these features provides a new challenge to models of DSA.

Evidence for particle acceleration in the magnetospheric cusp

Abstract. New evidence reveals that the charged particles can be energized locally in the magnetospheric cusp. The power spectral density of the cusp magnetic fluctuations shows increases by up to four orders of magnitude in comparison to an adjacent region. Large fluctuations of the cusp electric fields have been observed with an amplitude of up to 350 mV/m. The measured left-hand polarization of the cusp electric field at ion gyro-frequencies indicates that the cyclotron resonant acceleration mechanism is working in this region. The cyclotron resonant acceleration can energize ions from keV to MeV in seconds.

Inverse Compton Emission from Galactic Supernova Remnants: Effect of the Interstellar Radiation Field

The evidence for particle acceleration in supernova shells comes from electrons whose synchrotron emission is observed in radio and X-rays. Recent observations by the HESS instrument reveal that supernova remnants also emit TeV gamma-rays; long awaited experimental evidence that supernova remnants can accelerate cosmic rays up to the ``knee'' energies. Still, uncertainty exists whether these gamma-rays are produced by electrons via inverse Compton scattering or by protons via neutral pion decay. The multi-wavelength spectra of supernova remnants can be fitted with both mechanisms, although a preference is often given to neutral pion decay due to the spectral shape at very high energies. A recent study of the interstellar radiation field indicates that its energy density, especially in the inner Galaxy, is higher than previously thought. In this paper we evaluate the effect of the interstellar radiation field on the inverse Compton emission of electrons accelerated in a supernova remnant located at different distances from the Galactic Centre. We show that contribution of optical and infra-red photons to the inverse Compton emission may exceed the contribution of cosmic microwave background and in some cases broaden the resulted gamma-ray spectrum. Additionally, we show that if a supernova remnant is located close to the Galactic Centre its gamma-ray spectrum will exhibit a ``universal'' cutoff at very high energies due to the Klein-Nishina effect and not due to the cut-off of the electron spectrum. As an example, we apply our calculations to the supernova remnants RX J1713.7-3946 and G0.9+0.1 recently observed by HESS.

Cosmic rays and the electric field of thunderclouds: Evidence for acceleration of particles (runaway electrons)

We present the data on correlations of the intensity of the soft component of cosmic rays with the local electric field of the near-earth atmosphere during thunderstorm periods at the Baksan Valley (North Caucasus, 1700 m a.s.l.). The large-area array for studying the extensive air showers of cosmic rays is used as a particle detector. An electric field meter of the ‘electric mill’ type (rain-protected) is mounted on the roof of the building in the center of this array. The data were obtained in the summer seasons of 2000–2002. We observe strong enhancements of the soft component intensity before some lightning strokes. At the same time, the analysis of the regression curve ‘intensity versus field’ discovers a bump at the field sign that is opposite to the field sign corresponding to acceleration of electrons. It is interpreted as a signature of runaway electrons from the region of the strong field (with opposite sign) overhead.

Time-extended acceleration of energetic particles in the corona during the 19 October 1989 GLE

The broad injection cones and long durations of large solar energetic particle events (SEPs) have been recently considered as evidence for particle acceleration in the shock wave generated by a coronal mass ejection. Radio observations of an energetic flare on 19 Oct 1989 show that energetic electrons radiate both near the flare site and several tens of heliocentric degrees away. This is evidence for rapid particle propagation from the flare site or else for the simultaneous activation of widely separated sites of acceleration. At some places energetic electron signatures persist over at least several hours after the flare. We argue that even if the CME-associated shock wave may contribute to the acceleration, it competes with processes in the low and middle corona which may supply energetic particles to interplanetary space over several hours and with injection cones comparable with the width of CMEs.

Evidence for Particle Acceleration and Nuclear Reactions around Compact Relativistic Objects

AbstractIn this paper I summarize recent observational evidence for processes of particle acceleration around compact objects and their interaction with the ambient medium, which leads to nucleosynthesis of light elements (D, Li, Be, B).

Evidence for particle acceleration in a magnetized white dwarf from radio and gamma-ray observations

view Abstract Citations (42) References (36) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Evidence for Particle Acceleration in a Magnetized White Dwarf from Radio and Gamma-Ray Observations de Jager, O. C. Abstract The DQ Her-type magnetic cataclysmic variable AE Aqr contains the most rapidly spinning white dwarf (P = 33 s) in a close binary and can be considered as the 'millisecond pulsar' equivalent of white dwarfs. It shows flare-like UV emission on timescales of an hour during which strong Quasi-Periodic Oscillation (QPO) activity is seen, as well as flare-like radio synchrotron emission on similar timescales up to frequencies of at least 250 GHz. It is one of the most efficient coverters of accretion power to MeV electrons of all X-ray binaries, LMXB, and cataclysmic variables. TeV emission was also reported by two independent groups with a periodic and burst-like behavior similar to that seen in optical. The detection of a period derivative near 10-13 s/s in optical implies that the white dwarf is spinning down at a rate of approximately 6 x 1033 ergs/s which is at least an order of magnitude larger than the quiescent accretion luminosity and a few times larger than the typical UV flare luminosities. This spindown energy is not seen as disk luminosity, and the conditions appear to be favorable for the release of relativistic particles in a pulsar-type mechanism to explain the radio synchrotron emission in magnetic reconnection events, and the acceleration of particles to TeV energies in double layers if conditions are favorable. Publication: The Astrophysical Journal Supplement Series Pub Date: February 1994 DOI: 10.1086/191902 Bibcode: 1994ApJS...90..775D Keywords: Accretion Disks; Gamma Ray Astronomy; Particle Acceleration; Radio Astronomy; Relativistic Particles; White Dwarf Stars; Cataclysmic Variables; Current Density; Magnetic Field Reconnection; Stellar Luminosity; Ultraviolet Spectra; Astrophysics; ACCELERATION OF PARTICLES; STARS: BINARIES: CLOSE; STARS: FLARE; STARS: INDIVIDUAL CONSTELLATION NAME: AE AQUARII; STARS: WHITE DWARFS full text sources ADS | data products SIMBAD (3)

Evidence for particle acceleration during magnetospheric substorms

Magnetospheric substorms represent the episodic dissipation of energy stored in the geomagnetic tail that was previously extracted from the solar wind. This energy release produces activity throughout the entire magnetosphere-ionosphere system, and it results in a wide variety of phenomena such as auroral intensifications and the generation of new current systems. All of these phenomena involve the acceleration of particles, sometimes up to several MeV. We present a brief overview of substorm phenomenology. We then review some of the evidence for particle acceleration in Earth's magnetosphere during substorms. Such in-situ observations in this most accessible of all cosmic plasma domains may hold important clues to understanding acceleration processes in more distant astrophysical systems.

Evidence for Particle Acceleration in a Magnetized White Dwarf from Radio and Gamma-Ray Observations

AbstractThe DQ Her-type magnetic cataclysmic variable AE Aqr contains the most rapidly spinning white dwarf ( P = 33 s) in a close binary and can be considered as the “millisecond pulsar” equivalent of white dwarfs. It shows flare-like UV emission on timescales of an hour during which strong QPO activity is seen, as well as flare-like radio synchrotron emission on similar timescales up to frequencies of at least 250 GHz. It is one of the most efficient converters of accretion power to MeV electrons of all X-ray binaries, LMXB, and cataclysmic variables. TeV emission was also reported by two independent groups with a periodic and burst-like behavior similar to that seen in optical. The detection of a period derivative near 10−13 s/s in optical implies that the white dwarf is spinning down at a rate of ~6 × 1033 ergs s−1 which is at least an order of magnitude larger than the quiescent accretion luminosity and a few times larger than the typical UV flare luminosities. This spindown energy is not seen as disk luminosity, and the conditions appear to be favorable for the release of relativistic particles in a pulsar-type mechanism to explain the radio synchrotron emission in magnetic reconnection events, and the acceleration of particles to TeV energies in double layers if conditions are favorable.Subject headings: acceleration of particles — binaries: close — stars: flare — stars: individual (AE Aquarii) — white dwarfs

A study of auroral electron acceleration using the EISCAT radar and the viking satellite

Electron density profiles measured by the EISCAT radar during auroral activity can be inverted to determine the energy-flux spectrum of precipitating electrons responsible for the ionisation. Using short time resolutions we are able to resolve even the monoenergetically peaked spectra characteristic of discrete auroral arcs. We apply this technique to measurements made during a number of auroral substorms and make a classification of the spectra according to the stage of the substorm and the optical signature. The Viking satellite provides direct measurements of electron and ion energy-flux spectra at altitudes of 2000–7000 km over the auroral oval during the same events. Combining these two data sets we discuss the reliability of the spectra derived from EISCAT and the evidence for particle acceleration below the satellite.

The flares of April 1980

We discuss the spatial and temporal characteristics of X-ray flares occurring in the active region NOAA2372 from April 6 to 13, 1980. The flares are seen to extend in most cases across the whole active complex, involving several magnetic features. They originate in an intermediate bipole, between the two main sunspots of the active region, where high magnetic shear was detected. A rapid expansion is seen in some cases, in conjunction with the start of the impulsive hard X-ray bursts. We also detect, in the late phases of some of the events, a large soft X-ray structure overlying the whole active region, which also shows up as a noise storm region at metric wavelengths. These large loops cool by heat conduction but, in some cases, Hα condensations seem to appear, probably as a result of magnetic compression and a condensation mode of the thermal instability. The topological aspects of the field configuration are discussed, in the context of flare models invoking magnetic reconnection at the site of the primary energy release. In such a model, the intermediate bipole is the natural site of initial magnetic reconnection, particle acceleration and heating. In one particular case of a flare observed at the limb, we find possible evidence of particle acceleration in a neutral sheet at the boundary between two clearly defined magnetic structures.

Evidence for solar particle production above approximately 75 GeV.

Observations of solar particles in the energy region above approximately 75 GeV provide good evidence for particle acceleration during the initial phase of a solar flare.