Cosmic Ray Production Research Articles

The cosmic-ray content of the Orion-Eridanus superbubble

Aims.The nearby Orion-Eridanus superbubble, which was blown by multiple supernovae several million years ago, has likely produced cosmic rays. Its turbulent medium is still energised by massive stellar winds and it can impact cosmic-ray transport locally. Theγradiation produced in interactions between cosmic rays and interstellar gas can be used to compare the cosmic-ray spectrum in the superbubble and in other regions near the Sun. It can reveal spectral changes induced in GeV to TeV cosmic rays by the past and present stellar activity in the superbubble.Methods.We used ten years of data from theFermiLarge Area Telescope (LAT) in the 0.25–63 GeV energy range to study the closer (Eridanus) end of the superbubble at low Galactic latitudes. We modelled the spatial and spectral distributions of theγrays produced in the different gas phases (atomic, molecular, dark, and ionised) of the clouds found in this direction. The model included other non-gaseous components to match the data.Results.We found that theγ-ray emissivity spectrum of the gas along the outer rim and in a shell inside the superbubble is consistent with the average spectrum measured in the solar neighbourhood. It is also consistent with the cosmic-ray spectrum directly measured in the Solar System. This homogeneity calls for a detailed assessment of the recent supernova rate and current census of massive stellar winds in the superbubble in order to estimate the epoch and rate of cosmic-ray production and to constrain the transport conditions that can lead to such homogeneity and little re-acceleration. We also found significant evidence that a diffuse atomic cloud lying outside the superbubble, at a height of 200–250 pc below the Galactic plane, is pervaded by a 34% lower cosmic-ray flux, but with the same particle energy distribution as the local one. Super-GeV cosmic rays should freely cross such a light and diffuse cirrus cloud without significant loss or spectral distorsion. We tentatively propose that the cosmic-ray loss relates to the orientation of the magnetic field lines threading the cirrus, which point towards the halo according to the dust polarisation data fromPlanck. Finally, we gathered the present emissivity measurements with previous estimates obtained around the Sun to show how the local cosmic-ray flux decreases with Galactic height and to compare this trend with model predictions.

High-energy cosmic ray production in X-ray binary jets

ABSTRACT As smaller analogues of active galactic nuclei, X-ray binaries (XRBs) are also capable of launching jets that accelerate particles to high energies. In this work, we re-examine XRB jets as potential sources of high-energy cosmic rays (CRs) and explore whether they could provide a significant second Galactic component to the CR spectrum. In the most intriguing scenario, XRB-CRs could dominate the observed spectrum above the so-called knee feature at ∼3 × 1015 eV, offering an explanation for several key issues in this transition zone from Galactic to extragalactic CRs. We discuss how such a scenario could be probed in the near future via multimessenger observations of XRB jets, as well as diffuse Galactic neutrino flux measurements.

Secondary-electron radiation accompanying hadronic GeV–TeV gamma-rays from supernova remnants

ABSTRACT The synchrotron radiation from secondary electrons and positrons (SEPs) generated by hadronic interactions in the shock of supernova remnant (SNR) could be a distinct evidence of cosmic ray (CR) production in SNR shocks. Here, we provide a method where the observed gamma-ray flux from SNRs, created by pion decays, is directly used to derive the SEP distribution and hence the synchrotron spectrum. We apply the method to three gamma-ray bright SNRs. In the young SNR RX J1713.7−3946, if the observed GeV−TeV gamma-rays are of hadronic origin and the magnetic field in the SNR shock is B ≳ 0.5 mG, the SEPs may produce a spectral bump at 10−5–10−2 eV, exceeding the predicted synchrotron component of the leptonic model, and a soft spectral tail at ≳100 keV, distinct from the hard spectral slope in the leptonic model. In the middle-aged SNRs IC443 and W44, if the observed gamma-rays are of hadronic origin, the SEP synchrotron radiation with B ∼ 400–500 μG can well account for the observed radio flux and spectral slopes, supporting the hadronic origin of gamma-rays. Future microwave to far-infrared and hard X-ray (>100keV) observations are encouraged to constraining the SEP radiation and the gamma-ray origin in SNRs.

Cosmic Rays Investigation by the PAMELA experiment

PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) is a satellite-borne experiment. It was launched on June 15th 2006 from the Baikonur space centre on board the Russian Resurs-DK1 satellite. For about 10 years PAMELA took data, giving a fundamental contribution to the cosmic ray physics. It made high-precision measurements of the charged component of the cosmic radiation challenging the standard model of the mechanisms of production, acceleration and propagation of cosmic rays in the galaxy and in the heliosphere. PAMELA gave results on different topics on a very wide range of energy. Moreover, the long PAMELA life gives the possibility to study the variation of the proton, electron and positron spectra during the last solar minimum. The time dependence of the cosmic-ray proton and helium nuclei from the solar minimum through the following period of solar maximum activity is currently being studied. Low energy particle spectra were accurately measured also for various solar events that occurred during the PAMELA mission. In this paper a review of main PAMELA results will be reported.

Recent Results from the High Altitude Water Cherenkov Observatory

The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory, anextensive air shower detector consisting of 300 water Cherenkov tanks located at 4100m in Puebla, Mexico, has been surveying the TeV gamma-ray sky for almost five years. HAWC can observe steady sources, variable sources, transients, which allows for probes of both astrophysical and particle physics phenomena. This includes the production and propagation of cosmic rays, studies of Lorentz invariance violation, and dark matter searches. I will discuss recent HAWC results as well as the future of the observatory.

Ten years of AGILE: the mission and scientific highlights

We review the main features and scientific results obtained during the first 10 years of the AGILE space Mission, a scientific program of the Italian Space Agency (ASI) focused on high-energy astrophysics. The Mission was proposed in 1997 for the ASI “Small Mission” Program and the instrument has been developed with the programmatic and technical support of INAF and INFN. The AGILE satellite was launched on April 23, 2007, from the Indian base in Sriharikota. We describe first the characteristics of the instrument and of the satellite. AGILE is a very innovative space Mission for its class, and is capable of reaching an optimal scientific performance for the study of astrophysical sources with detectors operating in the energy ranges 20–60 keV, 400 keV–100 MeV, 50 MeV–30 GeV. We review the main scientific achievements of the Mission with contributions to the study of the most energetic Galactic and extragalactic sources including accreting compact objects (neutron stars and black holes), pulsars, Supernova Remnants, Active Galactic Nuclei (AGN). AGILE made several important discoveries: a novel mechanism of particle acceleration operating in the Crab Nebula, the emission of transient gamma rays at the moment of launching of relativistic jets from Galactic compact sources, the first evidence of hadronic cosmic ray production from Galactic sources, the emission of very powerful gamma-ray flares from accreting super-massive black holes in AGN, sudden spectral transitions in gamma-ray bursts. Furthermore, AGILE is now providing unique contributions for the study of gravitational wave source counterparts and cosmic neutrino emitters. Also terrestrial applications are relevant for the science program: AGILE discovered gamma-ray emission above 20 MeV from Terrestrial gamma-ray flashes produced by powerful lighting and thunderstorms. This discovery has an important impact for environmental and atmospheric studies. In addition, particle resonance effects and time-dependent precipitations in the lower Earth magnetosphere can by addressed by AGILE studying the charged particles detected by the instrument. The AGILE satellite is operating nominally, and continues to observe the sky searching for the most energetic phenomena of our Universe.

An Introduction to Particle Acceleration in Shearing Flows

Shear flows are ubiquitously present in space and astrophysical plasmas. This paper highlights the central idea of the non-thermal acceleration of charged particles in shearing flows and reviews some of the recent developments. Topics include the acceleration of charged particles by microscopic instabilities in collisionless relativistic shear flows, Fermi-type particle acceleration in macroscopic, gradual and non-gradual shear flows, as well as shear particle acceleration by large-scale velocity turbulence. When put in the context of jetted astrophysical sources such as Active Galactic Nuclei, the results illustrate a variety of means beyond conventional diffusive shock acceleration by which power-law like particle distributions might be generated. This suggests that relativistic shear flows can account for efficient in-situ acceleration of energetic electrons and be of relevance for the production of extreme cosmic rays.

Cosmogenic production of Ar39 and Ar37 in argon

We have experimentally determined the production rate of $^{39}$Ar and $^{37}$Ar from cosmic ray neutron interactions in argon at sea level. Understanding these production rates is important for argon-based dark matter experiments that plan to utilize argon extracted from deep underground because it is imperative to know what the ingrowth of $^{39}$Ar will be during the production, transport, and storage of the underground argon. These measurements also allow for the prediction of $^{39}$Ar and $^{37}$Ar concentrations in the atmosphere which can be used to determine the presence of other sources of these isotopes. Through controlled irradiation with a neutron beam that mimics the cosmic ray neutron spectrum, followed by direct counting of $^{39}$Ar and $^{37}$Ar decays with sensitive ultra-low background proportional counters, we determined that the production rate from cosmic ray neutrons at sea-level is expected to be $(759 \pm 128)$ atoms/kg$_\text{Ar}$/day for $^{39}$Ar, and $(51.0 \pm 7.4)$ atoms/kg$_\text{Ar}$/day for $^{37}$Ar. We also performed a survey of the alternate production mechanisms based on the state-of-knowledge of the associated cross-sections to obtain a total sea-level cosmic ray production rate of $(1048 \pm 133)$ atoms/kg$_\text{Ar}$/day for $^{39}$Ar, $(56.7 \pm 7.5)$ atoms/kg$_\text{Ar}$/day for $^{37}$Ar in underground argon, and $(92 \pm 13)$ atoms/kg$_\text{Ar}$/day for $^{37}$Ar in atmospheric argon.

Multimessenger Implications of AT2018cow: High-energy Cosmic-Ray and Neutrino Emissions from Magnetar-powered Superluminous Transients

Abstract Newly born, rapidly spinning magnetars have been invoked as the power sources of superluminous transients, including the class of “fast blue optical transients” (FBOTs). The extensive multiwavelength analysis of AT2018cow, the first FBOT discovered in real time, is consistent with the magnetar scenario and offers an unprecedented opportunity to comprehend the nature of these sources and assess their broader implications. Using AT2018cow as a prototype, we investigate high-energy neutrino and cosmic-ray production from FBOTs and the more general class of superluminous supernovae (SLSNe). By calculating the interaction of cosmic rays and the time-evolving radiation field and baryon background, we find that particles accelerated in the magnetar wind may escape the ejecta at ultrahigh energies. The predicted high-energy neutrino fluence from AT2018cow is below the sensitivity of the IceCube Observatory, and estimates of the cosmically integrated neutrino flux from FBOTs are consistent with the extreme-high-energy upper limits posed by IceCube. High-energy γ rays exceeding GeV energies are obscured for the first months to years by thermal photons in the magnetar nebula, but are potentially observable at later times. Given their potentially higher volumetric rate compared to other engine-powered transients (e.g., SLSNe and gamma-ray bursts), we conclude that FBOTs are favorable targets for current and next-generation multimessenger observatories.

A VLT/FLAMES survey for massive binaries in Westerlund 1

Context. X-ray emission from massive stars was first reported four decades ago, but the precise physics governing its formation as a function of stellar properties and binarity remains not fully understood. With the recent suggestion that such objects may be important sites of cosmic ray production, a better understanding of their high-energy properties is particularly timely. Aims. The young massive cluster Westerlund 1 provides an ideal testbed for understanding this emission, with over 50 cluster members detected in historical X-ray observations. In the decade since these data were obtained, significant new multi-epoch observations of the cluster have been made, allowing a fundamental reappraisal of the nature of both X-ray bright and dark stars. Methods. Optical spectroscopy permits accurate classification of cluster members, while multi-epoch observations of a sub-set allow identification and characterisation of the binary population. Results. A total of 45 X-ray sources within Wd1 now have precise spectral classifications. Of these, 16 have been identified as candidate or confirmed massive binaries. X-ray emission is confined to O9-B0.5 supergiants, Wolf-Rayets and a small group of highly luminous interacting/post-interaction OB+OB binaries. Despite their presence in large numbers, no emission is seen from earlier, less evolved O stars or later, cooler B super-/hypergiants. A total of 22 stars have X-ray properties that are suggestive of a contribution from emission originating in a wind collision zone. Conclusions. We suppose that the lack of X-ray emission from O giants is due to their comparatively low intrinsic bolometric luminosity if, as expected, they follow the canonical LX/Lbol relation for hot stars. The transition away from X-ray emission for OB supergiants occurs at the location of the bistability jump; we speculate that below this limit, stellar wind velocities are insufficient for internal, X-ray emitting shocks to form. Our results are consistent with recent findings that massive binaries are not uniformly brighter than single stars of comparable luminosity or spectral type, although it is noteworthy that the brightest and hardest stellar X-ray sources within Wd1 are all either confirmed or candidate massive, interacting/post-interaction binaries.

The legacy of PAMELA

PAMELA, a medium-sized experiment for the detection of cosmic rays, took data in space from 2006 to 2016. Composed of a magnetic spectrometer and several auxiliary detectors, the instrument compensated the reduced dimensions with the high performance of the individual detectors to obtain high-precision measurements over a range of energy from tens of MeV/n to 1 TeV/n.In ten years of operation PAMELA revealed very interesting features in cosmic rays, namely in the fluxes of protons, helium, electrons, that might change our basic vision of the mechanisms of production, acceleration and propagation of cosmic rays in the Galaxy. Amazing and stimulating have been the measurements of cosmic antiproton and positron fluxes that have allowed the nature of dark matter to be probed in a new way, suggesting new ideas and setting strong constraints to the models. The constant monitoring of the solar activity and the detailed study of the solar modulation of cosmic rays for a long period have boosted important improvements to the comprehension of the heliosphere mechanisms. PAMELA also measured the radiation environment around the Earth and discovered an antiproton radiation belt.

Positron Annihilation Spectroscopy of Active Galactic Nuclei

This paper focuses on the interpretation of radiation fluxes from active galactic nuclei. The advantage of positron annihilation spectroscopy over other methods of spectral diagnostics of active galactic nuclei (therefore AGN) is demonstrated. A relationship between regular and random components in both bolometric and spectral composition of fluxes of quanta and particles generated in AGN is found. We consider their diffuse component separately and also detect radiative feedback after the passage of high-velocity cosmic rays and hard quanta through gas-and-dust aggregates surrounding massive black holes in AGN. The motion of relativistic positrons and electrons in such complex systems produces secondary radiation throughout the whole investigated region of active galactic nuclei in form of cylinder with radius R= 400-1000 pc and height H=200-400 pc, thus causing their visible luminescence across all spectral bands. We obtain radiation and electron energy distribution functions depending on the spatial distribution of the investigated bulk of matter in AGN. Radiation luminescence of the noncentral part of AGN is a response to the effects of particles and quanta falling from its center created by atoms, molecules and dust of its diffuse component. The cross-sections for the single-photon annihilation of positrons of different energies with atoms in these active galactic nuclei are determined. For the first time we use the data on the change in chemical composition due to spallation reactions induced by high-energy particles. We establish or define more accurately how the energies of the incident positron, emitted γ-quantum and recoiling nucleus correlate with the atomic number and weight of the target nucleus. For light elements, we provide detailed tables of all indicated parameters. A new criterion is proposed, based on the use of the ratio of the fluxes of γ-quanta formed in one- and two-photon annihilation of positrons in a diffuse medium. It is concluded that, as is the case in young supernova remnants, the two-photon annihilation tends to occur in solid-state grains as a result of active loss of kinetic energy of positrons due to ionisation down to thermal energy of free electrons. The singlephoton annihilation of positrons manifests itself in the gas component of active galactic nuclei. Such annihilation occurs as interaction between positrons and K-shell electrons; hence, it is suitable for identification of the chemical state of substances comprising the gas component of the investigated media. Specific physical media producing high fluxes of positrons are discussed; it allowed a significant reduction in the number of reaction channels generating positrons. We estimate the brightness distribution in the γ-ray spectra of the gas-and-dust media through which positron fluxes travel with the energy range similar to that recorded by the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) research module. Based on the results of our calculations, we analyse the reasons for such a high power of positrons to penetrate through gas-and-dust aggregates. The energy loss of positrons by ionisation is compared to the production of secondary positrons by high-energy cosmic rays in order to determine the depth of their penetration into gas-and-dust aggregations clustered in active galactic nuclei. The relationship between the energy of γ-quanta emitted upon the single-photon annihilation and the energy of incident electrons is established. The obtained cross sections for positron interactions with bound electrons of the diffuse component of the non-central, peripheral AGN regions allowed us to obtain new spectroscopic characteristics of the atoms involved in singlephoton annihilation.

Searches for ultrahigh-energy neutrinos from gravitational wave events with the Pierre Auger Observatory

With the advent of the multi-messenger astronomy era, neutrinos open a unique window to the Universe allowing one to relate the most violent phenomena with the production and origin of the highest energy cosmic rays at distances beyond the GZK horizon. Neutrinos with E > 0.1 EeV of all flavors can be detected with the Surface Detector array of the Pierre Auger Observatory by means of their interaction in the atmosphere (downward-going ) or in the Earth crust (Earth-skimming ). The Pierre Auger Collaboration has searched for neutrino candidates in coincidence with gravitational wave events detected by LIGO/Virgo. Up to the present moment no neutrino candidates were found in any of these searches, which allows us to put competitive limits on the energy radiated in ultra-high energy neutrinos. The most stringent limits to the neutrino spectral fluence arise from the binary neutron star merger event GW170817 at a Ds ∼ 40 Mpc. The non-detection of neutrinos from this event is compatible with the predictions of a short GRB observed at a large off-axis angle.

Cosmic ray direct measurements

Direct measurements on cosmic rays in the energy region between tens MeV/n and few TeV/n have been extensively performed since the sixties by experiments on board stratospheric balloons, satellites, and Space Stations. The main goals have been the search for primordial antimatter, dark matter annihilation signals and exotic particles and the study of the mechanisms of production, acceleration and propagation of cosmic rays. A review of the major results up to an energy of few TeV obtained by the previous and the current experiments is presented in this article.

Latest results on high-energy cosmic neutrino searches with the ANTARES neutrino telescope

The ANTARES detector is currently the largest undersea neutrino telescope. Located in the Mediterranean Sea at a depth of 2.5 km, 40 km off the Southern coast of France, it has been looking for cosmic neutrinos for more than 10 years. High-energy cosmic neutrino production is strongly linked with cosmic ray production. The latest results from IceCube Collaboration represent a step forward towards the confirmation of a highenergy cosmic ray source. The ANTARES location in the Northern Hemisphere is optimal for the observation of most of the Galactic Plane, including the Galactic Center. It has constrained the IceCube neutrino excess reports as well as, more recently, the flux from the source identified in the Blazar TXS 0506+056. The latest results of ANTARES on such analyses, including point-like and extended sources, diffuse fluxes, transient phenomena and multi-messenger studies, are presented.

High-energy emissions from neutron star mergers

In 2017, LIGO-Virgo collaborations reported detection of the first neutron star merger event, GW170817, which is accompanied by electromagnetic counterparts from radio to gamma rays. Although high-energy neutrinos were not detected from this event, mergers of neutron stars are expected to produce such high-energy particles. Relativistic jets are launched when neutron stars merge. If the jets contain protons, they can emit high-energy neutrinos through photomeson production. In addition, neutron star mergers produce massive and fast ejecta, which can be a source of Galactic high-energy cosmic rays above the knee. We briefly review what we learned from the multi-messenger event, GW170817, and discuss prospects for multi-messenger detections and hadronic cosmic-ray production related to the neutron star mergers.

Joint Constraints on Galactic Diffuse Neutrino Emission from the ANTARES and IceCube Neutrino Telescopes

Abstract The existence of diffuse Galactic neutrino production is expected from cosmic-ray interactions with Galactic gas and radiation fields. Thus, neutrinos are a unique messenger offering the opportunity to test the products of Galactic cosmic-ray interactions up to energies of hundreds of TeV. Here we present a search for this production using ten years of Astronomy with a Neutrino Telescope and Abyss environmental RESearch (ANTARES) track and shower data, as well as seven years of IceCube track data. The data are combined into a joint likelihood test for neutrino emission according to the KRA model assuming a 5 PeV per nucleon Galactic cosmic-ray cutoff. No significant excess is found. As a consequence, the limits presented in this Letter start constraining the model parameter space for Galactic cosmic-ray production and transport.

Constraints on the Cosmic-Ray Ionization Rate in the z ∼ 2.3 Lensed Galaxies SMM J2135–0102 and SDP 17b from Observations of OH+ and H2O+

Abstract Cosmic rays are predominantly accelerated in shocks associated with star formation such as supernova remnants and stellar wind bubbles, so the cosmic-ray flux and thus cosmic-ray ionization rate, ζ H, should correlate with the star formation rate in a galaxy. Submillimeter bright galaxies (SMGs) are some of the most prolific star-forming galaxies in the universe, and gravitationally lensed SMGs provide bright continuum sources suitable for absorption line studies. Abundances of OH+ and H2O+ are useful for inferring ζ H when combined with chemical models, and have been used for this purpose within the Milky Way. At redshifts z ≳ 2 transitions out of the ground rotational states of OH+ and H2O+ are observable with ALMA, and we present observations of both molecules in absorption toward the lensed SMGs SMM J2135−0102 and SDP 17b. These detections enable an exploration of ζ H in galaxies with extreme star formation and high supernova rates, both of which should significantly enhance cosmic-ray production. The observed OH+ and H2O+ absorption is thought to arise in massive, extended halos of cool, diffuse gas that surround these galaxies. Using a chemical model designed to focus on the reaction network important to both species, we infer cosmic-ray ionization rates of ζ H ∼ 10−16–10−14 s−1 in these extended gaseous halos. Because our estimates come from gas that is far away from the sites of cosmic-ray acceleration, they imply that cosmic-ray ionization rates in the compact regions where star formation occurs in these galaxies are orders of magnitude higher.

Ultra-high-energy cosmic rays and neutrinos from tidal disruptions by massive black holes

Tidal disruptions are extremely powerful phenomena that have been designated as candidate sources of ultra-high-energy cosmic rays. The disruption of a star by a black hole can naturally provide protons and heavier nuclei, which can be injected and accelerated to ultra-high energies within a jet. Inside the jet, accelerated nuclei are likely to interact with a dense photon field, leading to a significant production of neutrinos and secondary particles. We model numerically the propagation and interactions of high-energy nuclei in jetted tidal disruption events in order to evaluate consistently their signatures in cosmic rays and neutrinos. We propose a simple model of the light curve of tidal disruption events, consisting of two stages: a high state with bright luminosity and short duration and a medium state, less bright and longer lasting. These two states have different impacts on the production of cosmic rays and neutrinos. In order to calculate the diffuse fluxes of cosmic rays and neutrinos, we model the luminosity function and redshift evolution of jetted tidal disruption events. We find that we can fit the latest ultra-high-energy cosmic-ray spectrum and composition results of the Auger experiment for a range of reasonable parameters. The diffuse neutrino flux associated with this scenario is found to be subdominant, but nearby events can be detected by IceCube or next-generation detectors such as IceCube-Gen2.

Particle acceleration in the superwinds of starburst galaxies

Context. Starbursts are galaxies undergoing massive episodes of star formation. The combined effect of stellar winds from hot stars and supernova explosions creates a high-temperature cavity in the nuclear region of these objects. The very hot gas expands adiabatically and escapes from the galaxy creating a superwind which sweeps matter from the galactic disk. The superwind region in the halo is filled with a multi-phase gas with hot, warm, cool, and relativistic components. Aims. The shocks associated with the superwind of starbursts and the turbulent gas region of the bubble inflated by them might accelerate cosmic rays up to high energies. In this work we calculate the cosmic ray production associated with the superwind using parameters that correspond to the nearby southern starburst galaxy NGC 253, which has been suggested as a potential accelerator of ultra-high-energy cosmic rays. Methods. We evaluate the efficiency of both diffusive shock acceleration (DSA) and stochastic diffusive acceleration (SDA) in the superwind of NGC 253. We estimate the distribution of both hadrons and leptons and calculate the corresponding spectral energy distributions of photons. The electromagnetic radiation can help to discriminate between the different scenarios analyzed. Results. We find that the strong mass load of the superwind, recently determined through ALMA observations, strongly attenuates the efficiency of DSA in NGC 253, whereas SDA is constrained by the age of the starburst. Conclusions. We conclude that NGC 253 and similar starbursts can only accelerate iron nuclei beyond ~1018 eV under very special conditions. If the central region of the galaxy harbors a starved supermassive black hole of ~106 M⊙, as suggested by some recent observations, a contribution in the range 1018−1019 eV can be present for accretion rates ṁ ~ 10−3 in Eddington units. Shock energies of the order of 100 EeV might only be possible if very strong magnetic field amplification occurs close to the superwind.