ner_tags: B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O O O O B-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula I-Formula O O O O O O O O O O B-Wavelength O O O B-Observatory B-Telescope O B-Telescope O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-Wavelength B-CelestialObject O O O B-CelestialObject O B-CelestialObject B-Wavelength O O O O O O O O O O O O B-Wavelength O O B-CelestialObject O O O O O O O O O O O B-Wavelength O O O O O O O O O O O O O O O B-Wavelength O O O O O O O O O O O B-Wavelength O O O O O O O O B-Observatory B-Telescope O B-Telescope O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B-CelestialObject I-CelestialObject O O O O O O B-CelestialObject I-CelestialObject O O O O O O O O O O O O
tokens: X-ray emitting e + e − pairs are fast cooling, which allows us to write their detailed energy balance. This results in a lower limit on , which is the ratio of the magnetar's long-term mean energy output in outflows (quiescent MHD wind + sporadic outbursts), , to its spin-down luminosity. This clearly implies that the MWN is not powered predominantly by the magnetar's spin-down-powered wind, and an alternative dominant energy source is required, most likely the decay of the magnetar's magnetic field. We show that the decay of its dipole field alone is not enough, and a significantly larger (by a factor of ∼10 2 –10 3 ) energy reservoir is needed. The most plausible candidate is the magnetar's internal magnetic field, which has to be ≳ 10 − 30 times larger than its dipole field. Finally, by assuming a maximum allowed initial internal field strength (on theoretical grounds) of B int, max ∼ 10 16 –10 16.5 G we obtain an upper limit on g ≲ 5 × (10 2 –10 3 ). In Section 7 we consider the possible origin of the GeV/TeV emission observed by Fermi /LAT and H.E.S.S. In Section 7.1 we consider the possibility of a hadronic origin for the GeV/TeV emission. While inverse-Compton emission by electrons in the MWN is energetically very challenging, we find a much more plausible and energetically reasonable alternative to be the decay of neutral pions that are produced by the interaction of cosmic rays (CR) accelerated in the shock driven by the SNR into the external medium, with nuclei in the nearby giant molecular cloud (GMC). In Section 7.2 , we consider the possibility of inverse-Compton emission by relativistic electrons in the MWN that upscatter seed photons from the NIR Galactic background and the CMB. For Galactic NIR seed photons we find it extremely difficult to account for the observed GeV/TeV luminosity. For CMB seed photons it is also very difficult to account for the GeV/TeV luminosity, and moreover, together with the power-law MWN electron energy distribution (as reflected by their X-ray synchrotron emission) one would expect a much broader spectral peak at TeV energies, which is hard to reconcile with the Fermi /LAT and H.E.S.S. observations. Therefore, we find this option implausible. Finally, we also consider emission from relativistic non-thermal bremsstrahlung from electrons accelerated at the SNR forward shock. Our conclusions are discussed in Section 8 . Our main findings are that the MWN is powered predominantly by outflows from the magnetar, whose main energy source is most likely the decay of its strong internal magnetic field. These conclusions became possible because of the discovery of this first MWN. The outflows from the magnetar accumulate inside the MWN, which therefore serves as a calorimeter that helps us study the system's history. 2 IMPLICATIONS OF THE ASSOCIATION WITH THE SNR The location of Swift J1834 at the very centre of the SNR W41 strongly supports their association. Moreover, it can also constrain the SGR's proper