Cosmic Magnetism

UNIVERSAL IMPORTANCE
“Magnetic fields are involved in every astrophysical process on every scale: from planetary and stellar interiors to neutron stars, stellar wind bubbles and supernova remnants; from the interstellar medium in galactic disks, nuclei, spiral arms and halos to the intracluster and intergalactic media. They are involved in essentially every particle acceleration process and are thus fundamental to non-thermal physics in the Universe.”
 
THE ALL-PERVASIVE ETHER.
“Magnetic fields span many orders of magnitude in both their physical scale and field strength reaching as high as 10(15) Gauss in magnetars to as low as 10(-9) Gauss in intergalactic regions. Since they do not radiate and cannot be observed directly, their study is challenging.”
 
ENORMOUS IMPACT.
“Magnetic fields are a natural consequence of the dynamic plasmas that comprise a star. They directly and indirectly impact stellar lives through modification of convective and circulatory interior flows, redistribution of angular momentum and nucleosynthetic chemicals, channeling and modification of mass loss and accretion, and shedding of rotational angular momentum through magnetic braking.”
 

 

 
ALL OF EVERYTHING AFFECTED.
“Ultimately, these effects lead to important modification of stellar evolutionary pathways and stellar feedback effects, such as mechanical energy deposition in the ISM and supernova explosions, and hence the properties of stellar remnants and the structure and chemistry of the local Galactic environment.” (ISM = the interstellar medium).
 
PROBES.
“Magnetic fields pervade in the interstellar medium and are believed to shape the process of star formation, yet probing magnetic fields is challenging.”
 
ENORMOUS ENERGY.
“Turbulent magnetic fields are thought to be a significant component of the Galaxy with a magnitude equal to or greater than the mean field component.”
 
THE SHADOW CAST.
“Observations of nearby spiral galaxies have revealed a regular large scale pattern that follows the spiral arms. However these observations are 2D projections of a 3D field, of which the exact topology remains a mystery.”
 
SNARK.
“They sought it with thimbles, they sought it with care;
They pursued it with forks and hope;
They threatened its life with a railway-share;
They charmed it with smiles and soap.”
(Lewis Carroll, The Hunting of the Snark),
 
TURBULENT HEAVENS.
“Galactic magnetic fields should not be treated as minor perturbations, but rather as key ingredients in a rich dynamically active environment.”
 
PARTICLE ACCELERATORS.
“Galactic magnetic fields are thought to be responsible for the acceleration of electrons, positrons and ions to cosmic rays.”
 
EXTREME ENERGY.
“Additionally, ultra-high energy cosmic rays (UHECRs) are extragalactic cosmic rays with energies exceeding 10(18) eV.”
 
ORIGINS.
“Acceleration to these extreme energies could be due to transients such as massive supernovae or compact object mergers, active-galactic nuclei, or galaxy clusters, though the exact mechanism is unclear.”
 
JETS OF IONS.
“Active Galactic Nuclei, powered by accretion on a supermassive black hole, eject relativistic jets that interact with the interstellar and intergalactic medium on sub-pc to Mpc scales.”
 
MAGNETIC FIELDS
“Magnetic fields in AGN are observed from pc scales to Mpc scales, e.g. from the non-thermal filaments in the Galactic centre, VLBI polarimetry of radio galaxy cores, to polarization of jets, and radio lobes. They affect the accretion disk, jet collimation and particle acceleration, and contribute significantly to the pressure inside radio lobes.” (AGN = Active Galactic Nuclei).
 
STRUCTURED UNIVERSE.
“We know that on the largest scales there is structure to the Universe: voids, filaments, and clusters (e.g. the cosmic web).”
 
BLACK BOX.
“Theory tells us the magnetic fields pervade all of this intergalactic space, but as yet there have been no measurements of intergalactic magnetic fields. The origin of cosmic fields and their evolution and role in structure formation is unknown.”
 
KEY TO THE UNIVERSE.
“Magnetism contributes to every astrophysical process on every scale and its study offers considerable opportunity for transformational understanding.”

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