2,522 research outputs found
High-energy gamma-rays from stellar associations
It is proposed that TeV gamma-rays and neutrinos can be produced by cosmic
rays (CRs) through hadronic interactions in the innermost parts of the winds of
massive O and B stars. Convection prevents low-energy particles from
penetrating into the wind, leading to an absence of MeV-GeV counterparts. It is
argued that groups of stars located close to the CR acceleration sites in OB
stellar associations may be detectable by ground-based Cherenkov telescopes.Comment: 10 pages, 1 figure. Accepted for publication in Astrophysical Journal
Letter
High frequency waves in the corona due to null points
This work aims to understand the behavior of non-linear waves in the vicinity
of a coronal null point. In previous works we have showed that high frequency
waves are generated in such magnetic configuration. This paper studies those
waves in detail in order to provide a plausible explanation of their
generation. We demonstrate that slow magneto-acoustic shock waves generated in
the chromosphere propagate through the null point and produce a train of
secondary shocks that escape along the field lines. A particular combination of
the shock wave speeds generates waves at a frequency of 80 mHz. We speculate
that this frequency may be sensitive to the atmospheric parameters in the
corona and therefore can be used to probe the structure of this solar layer
UAS pilot support for departure, approach and airfield operations
Unmanned Aerial Systems (UAS) have great potential to be used in a wide variety of civil applications such as environmental applications, emergency situations, surveillance tasks and more. The development of Flight Control Systems (FCS) coupled with the availability of other Commercial Off-The Shelf (COTS) components is enabling the introduction of UAS into the civil market. The sophistication of existing FCS is also making these systems accessible to end users with little aeronautics expertise. However, much work remains to be done to deliver systems that can be properly integrated in standard aeronautical procedures used by manned aviation
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