Abstract
Using recent Pierre Auger Observatory results on the UHECR spectrum and composition, the requirements placed on the sources of these particles are discussed. In this sense, the author interprets the term “multi-messenger” throughout as to refer to the additional information provided by the composition. The spatial distribution of these sources is investigated along with the energy distribution of UHECR they output. These investigations reveal the need for local UHECR sources which output a hard spectrum of intermediate/heavy UHECR. These results demand that local (<80 Mpc) UHECR sources exist, placing exciting and difficult requirements on the local extragalactic candidate sources. Angular correlation studies in collaboration with composition information also demonstrated to offer great potential for isolating the UHECR source distance for which an angular clustering of events is found. Specifically, for the case a correlation of the 13 events correlated with the direction of Cen A, it is shown that the composition information, and specifically, the lack of a lower energy proton correlation, can potentially constrain the source distance to be less than 15 Mpc. The fragility of nuclei with accelerators are also used to place constraints are on the source environment. These constraints motivate 0.1–1000 mG strength magnetic fields exist within the source and that quasi-relativistic scatterers are also present. A specific example of a diffuse large scale “nuclei friendly” accelerator, which meets the outline constraints is put forward.
Highlights
The revelation following recent Pierre Auger Observatory (PAO) results that ultra high energy cosmic rays (UHECR) possess a significant nuclei component, as shown in Fig. 1, has important astrophysical implications
Both the PAO and Telescope Array (TA) instruments have reported large scale (∼ 20◦) anisotropy/clustering signatures [11, 12] whose statistical significance have increased through consecutive years worth of data
Future anisotropy signals using composition information can be used to provide a probe on the source distance information
Summary
The revelation following recent Pierre Auger Observatory (PAO) results that ultra high energy cosmic rays (UHECR) possess a significant nuclei component, as shown in Fig. 1, has important astrophysical implications. The revelation following recent Pierre Auger Observatory (PAO) results that ultra high energy cosmic rays (UHECR) possess a significant nuclei component, as shown, has important astrophysical implications. Leaving the question of the available relative abundance of these species in the source region aside, the question of their acceleration and transport are here addressed. Using the extra degree of information provided by the particle composition, on top of that already provided by the energy and direction of the UHECR, the consequences of this result are discussed. The source injection spectra and composition consistent with these results is summarised. The subsequent constraints placed on the locality of these sources is addressed. Methods employing this new composition information in order to locate the sources highlighted. An example of a “nuclei friendly” acceleration site is provided, with generalities from this example being noted where possible
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