scholarly journals A Supernova at 50 PC: Effects on the Earth’s Atmosphere and Biota

2017 ◽  
Author(s):  
A.L Melott ◽  
B.C. Thomas ◽  
M. Kachelrieß ◽  
D.V. Semikoz ◽  
A.C. Overholt
Keyword(s):  
Magnetic Field ◽  
Transverse Field ◽  
Cosmic Ray ◽  
Magnetic Field Effects ◽  
Field Orientation ◽  
Local Bubble ◽  
Coherent Field ◽  
Computational Procedures ◽  
Cosmic Ray Flux ◽  
Disordered Magnetic

ABSTRACTRecent 60Fe results have suggested that the estimated distances of supernovae in the last few million years should be reduced from ∼100 pc to ∼50 pc. Two events or series of events are suggested, one about 2.7 million years to 1.7 million years ago, and another may at 6.5 to 8.7 million years ago. We ask what effects such supernovae are expected to have on the terrestrial atmosphere and biota. Assuming that the Local Bubble was formed before the event being considered, and that the supernova and the Earth were both inside a weak, disordered magnetic field at that time, TeV-PeV cosmic rays at Earth will increase by a factor of a few hundred. Tropospheric ionization will increase proportionately, and the overall muon radiation load on terrestrial organisms will increase by a factor of ∼150. All return to pre-burst levels within 10kyr. In the case of an ordered magnetic field, effects depend strongly on the field orientation. The upper bound in this case is with a largely coherent field aligned along the line of sight to the supernova, in which case TeV-PeV cosmic ray flux increases are ∼104; in the case of a transverse field they are below current levels. We suggest a substantial increase in the extended effects of supernovae on Earth and in the “lethal distance” estimate; more work is needed. This paper is an explicit followup to Thomas et al. (2016). We also here provide more detail on the computational procedures used in both works.

scholarly journals Can the Local Bubble explain the radio background?

2021 ◽  
Vol 502 (2) ◽  
pp. 2807-2814
Author(s):  
Martin G H Krause ◽  
Martin J Hardcastle
Keyword(s):  
Magnetic Field ◽  
Energy Density ◽  
Radio Emission ◽  
Magnetic Energy ◽  
Cosmic Ray ◽  
Observational Constraints ◽  
Local Bubble ◽  
Magnetic Energy Density ◽  
Magnetic Field Model ◽  
Radio Background

ABSTRACT The ARCADE 2 balloon bolometer along with a number of other instruments have detected what appears to be a radio synchrotron background at frequencies below about 3 GHz. Neither extragalactic radio sources nor diffuse Galactic emission can currently account for this finding. We use the locally measured cosmic ray electron population, demodulated for effects of the Solar wind, and other observational constraints combined with a turbulent magnetic field model to predict the radio synchrotron emission for the Local Bubble. We find that the spectral index of the modelled radio emission is roughly consistent with the radio background. Our model can approximately reproduce the observed antenna temperatures for a mean magnetic field strength B between 3 and 5 nT. We argue that this would not violate observational constraints from pulsar measurements. However, the curvature in the predicted spectrum would mean that other, so far unknown sources would have to contribute below 100 MHz. Also, the magnetic energy density would then dominate over thermal and cosmic ray electron energy density, likely causing an inverse magnetic cascade with large variations of the radio emission in different sky directions as well as high polarization. We argue that this disagrees with several observations and thus that the magnetic field is probably much lower, quite possibly limited by equipartition with the energy density in relativistic or thermal particles (B = 0.2−0.6 nT). In the latter case, we predict a contribution of the Local Bubble to the unexplained radio background at most at the per cent level.

scholarly journals TeV Cosmic Ray Anisotropy and the Heliospheric Magnetic Field

2014 ◽  
Vol 1 ◽  
pp. 65-71 ◽  
Author(s):  
P. Desiati ◽  
A. Lazarian
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Particle Distribution ◽  
Sudden Change ◽  
Cosmic Ray ◽  
Arrival Direction ◽  
Energy Dependency ◽  
The Galaxy ◽  
Different Characteristics ◽  
Cosmic Ray Flux

Abstract. Cosmic rays are observed to possess a small non uniform distribution in arrival direction. Such anisotropy appears to have a roughly consistent topology between tens of GeV and hundreds of TeV, with a smooth energy dependency on phase and amplitude. Above a few hundreds of TeV a sudden change in the topology of the anisotropy is observed. The distribution of cosmic ray sources in the Milky Way is expected to inject anisotropy on the cosmic ray flux. The nearest and most recent sources, in particular, are expected to contribute more significantly than others. Moreover the interstellar medium is expected to have different characteristics throughout the Galaxy, with different turbulent properties and injection scales. Propagation effects in the interstellar magnetic field can shape the cosmic ray particle distribution as well. In particular, in the 1–10 TeV energy range, they have a gyroradius comparable to the size of the Heliosphere, assuming a typical interstellar magnetic field strength of 3 μG. Therefore they are expected to be strongly affected by the Heliosphere in a manner ordered by the direction of the local interstellar magnetic field and of the heliotail. In this paper we discuss on the possibility that TeV cosmic rays arrival distribution might be significantly redistributed as they propagate through the Heliosphere.

scholarly journals On a limitation of Zeeman polarimetry and imperfect instrumentation in representing solar magnetic fields with weaker polarization signal

2021 ◽  
Vol 11 ◽  
pp. 14
Author(s):  
A.A. Pevtsov ◽  
Y. Liu ◽  
I. Virtanen ◽  
L. Bertello ◽  
K. Mursula ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Transverse Field ◽  
Vector Magnetic Field ◽  
Field Orientation ◽  
Fill Fraction ◽  
Structure Morphology ◽  
Full Disk

Full disk vector magnetic fields are used widely for developing better understanding of large-scale structure, morphology, and patterns of the solar magnetic field. The data are also important for modeling various solar phenomena. However, observations of vector magnetic fields have one important limitation that may affect the determination of the true magnetic field orientation. This limitation stems from our ability to interpret the differing character of the Zeeman polarization signals which arise from the photospheric line-of-sight vs. the transverse components of the solar vector magnetic field, and is likely exacerbated by unresolved structure (non-unity fill fraction) as well as the disambiguation of the 180° degeneracy in the transverse-field azimuth. Here we provide a description of this phenomenon, and discuss issues, which require additional investigation.

ENERGETIC PARTICLES IN THE HELIOSPHERE

2005 ◽  
Vol 20 (29) ◽  
pp. 6621-6632 ◽  
Author(s):  
BERND HEBER
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Cosmic Rays ◽  
Energetic Particle ◽  
Current Knowledge ◽  
Cosmic Ray ◽  
Interplanetary Shock ◽  
The Sun ◽  
Local Interstellar Medium ◽  
Cosmic Ray Flux

The heliosphere is the region around the Sun that is filled by the solar wind and its embedded magnetic field. The interaction of the supersonic solar wind with the local interstellar medium leads to a transition from supersonic to subsonic speeds at the heliospheric termination shock. The latter is regarded to be the source of the anomalous component of cosmic rays. Within the heliosphere "local" energetic particle sources, like the Sun and interplanetary shock waves contribute to the cosmic ray flux, too. At energies below a few GeV the observed galactic and anomalous cosmic ray intensities are modulated by the heliospheric magnetic field. In my contribution, both the current knowledge and hypotheses about modulation and the transport of cosmic rays in the heliosphere are reviewed.

The Propagation of Cosmic Radiation Through the Inter-Planetary Magnetic Field

1967 ◽  
Vol 1 (1) ◽  
pp. 29-30
Author(s):  
K. G. McCracken
Keyword(s):  
Magnetic Field ◽  
Energy Range ◽  
Cosmic Radiation ◽  
Counting Rate ◽  
Cosmic Ray ◽  
Alpha Particles ◽  
Statistical Precision ◽  
Degree Of Anisotropy ◽  
Planetary Magnetic Field ◽  
Cosmic Ray Flux

Instruments were flown on the Pioneer 6 and 7 spacecraft during 1965-66 to study the degree of anisotropy of cosmic radiation in the energy range 7.5-90 Mev/nucleón. The instruments record the cosmic ray fluxes from each of four contiguous ‘quadrants’ of azimuthal rotation of the spacecraft, for each of three energy windows 7.5-45 Mev, 45-90 Mev, and 150-350 Mev for alpha particles and heavier nuclei. In addition, the counting rate of all particles of energy >7.5 Mev is recorded, thereby providing cosmic ray data of high statistical precision useful in the study of fast changes in the cosmic ray flux.

Cosmic-Ray Anisotropies as a Function of Time and Direction

1968 ◽  
Vol 1 (3) ◽  
pp. 114-115
Author(s):  
J.G. Ables
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Energy Range ◽  
Interplanetary Medium ◽  
Large Angle ◽  
Cosmic Ray ◽  
Angle Scattering ◽  
Large Angle Scattering ◽  
High Degree ◽  
Cosmic Ray Flux

The cosmic ray flux in the energy range 100 MeV/nucleon ≤ E ≤ 1 GeV/nucleon is remarkable for its high degree of isotropy. Observed deviations from isotropy seldom exceed a few per cent and are commonly much smaller. The mechanism responsible for this isotropy is presumed to be multiple, large-angle scattering of the charged cosmic ray particles by irregularities of the interplanetary magnetic field. While generally precluding any hope of discovering a source-related anisotropy of the flux in this energy range, it is just this strong interaction of the cosmic rays with the interplanetary medium that allows the study of the small observed anisotropies, both persistent and transient, to yield considerable information about the structure of the interplanetary medium (the solar wind and its entrapped magnetic field).

Signposts of shock-induced magnetic field compression in star-forming environments

2018 ◽  
Vol 14 (A30) ◽  
pp. 110-110
Author(s):  
Helmut Wiesemeyer
Keyword(s):  
Magnetic Field ◽  
Supernova Remnants ◽  
Dust Emission ◽  
Cosmic Ray ◽  
Induced Magnetic Field ◽  
Trapped Particles ◽  
Star Forming ◽  
Plane Projection ◽  
Deep Integration ◽  
Cosmic Ray Flux

AbstractIn star-forming environments, shock-compressed magnetic fields occur in cloud-cloud collisions, in molecular clouds exposed to supernova remnants (SNRs), and in photo-dissociation regions (PDRs). Besides their dynamical role, they increase the cosmic ray flux above the Galactic average, and the trapped particles contribute to the heating of the shocked gas. The associated dust emission is polarized perpendicularly to the sky plane projection of the field, Bsky. In edge-on viewed shock planes, highly ordered polarization patterns are expected. In search of such a signature, the dust emission from the Orion bar (a prototypical PDR) and from a molecular cloud/SNR interface (IC443-G) was studied with a λ870μm polarimeter at the APEX (Wiesemeyer etal 2014 and references therein). While our polarization map of OMC1 confirms the hourglass shape of Bsky (e.g., Schleuning 1998, Houde etal 2004), a deep integration towards the Orion bar reveals an alignment of Bsky with the shock forming in response to the wind and to the ionizing radiation from the Trapezium cluster (Fig. 1). This structure suggests a compressed magnetic field accelerating cosmic-ray particles, a scenario proposed by [Pellegrini et al. (2009)] to explain the high excitation temperature of rotationally warm H2 and CO (Shaw et al. 2009, Peng et al. 2012, respectively).

PERIODICITY IN DAILY VARIATION OF COSMIC RAY INTENSITY AS AN EFFECT OF SOLAR POLOIDAL MAGNETIC FIELD ORIENTATION

2004 ◽  
Vol 13 (02) ◽  
pp. 253-262 ◽  
Author(s):  
REKHA AGARWAL MISHRA ◽  
RAJESH K. MISHRA
Keyword(s):  
Magnetic Field ◽  
Daily Variation ◽  
Cosmic Ray ◽  
Activity Cycle ◽  
Solar Activity Cycle ◽  
Significant Shift ◽  
Poloidal Magnetic Field ◽  
Field Orientation ◽  
Cosmic Ray Intensity ◽  
Diurnal Anisotropy

A detailed analysis of the Deep River neutron monitor (NM) data for four different phases of solar activity cycle and for four groups of days chosen according to their different geomagnetic conditions is being carried out. It is found that the 60 quiet day (QD) in a year serve a better purpose for investigating the short/long term variation in cosmic ray (CR) intensity. Furthermore, data has been harmonically analysed for the period 1964–95 to investigate the effect of solar poloidal magnetic field (SPMF) orientation in daily variation (diurnal/semi-diurnal) of CR on geomagnetically QD. The phase of the diurnal and semi-diurnal anisotropy vectors on QD has shown a significant shift to early hours when the SPMF in the northern hemisphere (NH) is positive during the periods 1971–79 and 1992–95 as compared to that during the periods 1964–70 and 1981–90 when the SPMF in NH is negative, showing a periodic nature of daily variation in CR intensity with SPMF.

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