Spectrum of Relativistic and Subrelativistic Cosmic Rays in the 100 pc Central Region

From the rate of hydrogen ionization and the gamma ray flux, we derived the spectrum of relativistic and subrelativistic cosmic rays (CRs) nearby and inside the molecular cloud Sgr B2 near the Galactic Center (GC). We studied two cases of CR propagation in molecular clouds: free propagation and scattering of particles by magnetic fluctuations excited by the neutral gas turbulence. We showed that in the latter case CR propagation inside the cloud can be described as diffusion with the coefficient $\sim 3\times 10^{27}$ cm$^2$ s$^{-1}$. For the case of hydrogen ionization by subrelativistic protons, we showed that their spectrum outside the cloud is quite hard with the spectral index $\delta>-1$. The energy density of subrelativistic protons ($>50$ eV cm$^{-3}$) is one order of magnitude higher than that of relativistic CRs. These protons generate the 6.4 keV emission from Sgr B2, which was about 30\% of the flux observed by Suzaku in 2013. Future observations for the period after 2013 may discover the background flux generated by subrelativistic CRs in Sgr B2. Alternatively hydrogen ionization of the molecular gas in Sgr B2 may be caused by high energy electrons. We showed that the spectrum of electron bremsstrahlung is harder than the observed continuum from Sgr B2, and in principle this X-ray component provided by electrons could be seen from the INTEGRAL data as a stationary high energy excess above the observed spectrum $E_x^{-2}$.Comment: 42 pages, 6 figures, accepted by Ap

Bulk and surface electronic properties of SmB6: a hard x-ray photoelectron spectroscopy study

We have carried out bulk-sensitive hard x-ray photoelectron spectroscopy (HAXPES) measurements on in-situ cleaved and ex-situ polished SmB6 single crystals. Using the multiplet-structure in the Sm 3d core level spectra, we determined reliably that the valence of Sm in bulk SmB6 is close to 2.55 at ~5 K. Temperature dependent measurements revealed that the Sm valence gradually increases to 2.64 at 300 K. From a detailed line shape analysis we can clearly observe that not only the J=0 but also the J=1 state of the Sm 4f 6 configuration becomes occupied at elevated temperatures. Making use of the polarization dependence, we were able to identify and extract the Sm 4f spectral weight of the bulk material. Finally, we revealed that the oxidized or chemically damaged surface region of the ex-situ polished SmB6 single crystal is surprisingly thin, about 1 nm only.Comment: 11 pages, 8 figure

Contiguous 3d and 4f magnetism: towards strongly correlated 3d electrons in YbFe2Al10

We present magnetization, specific heat, and 27Al NMR investigations on YbFe2Al10 over a wide range in temperature and magnetic field. The magnetic susceptibility at low temperatures is strongly enhanced at weak magnetic fields, accompanied by a ln(T0/T) divergence of the low-T specific heat coefficient in zero field, which indicates a ground state of correlated electrons. From our hard X-ray photo emission spectroscopy (HAXPES) study, the Yb valence at 50 K is evaluated to be 2.38. The system displays valence fluctuating behavior in the low to intermediate temperature range, whereas above 400 K, Yb3+ carries a full and stable moment, and Fe carries a moment of about 3.1 mB. The enhanced value of the Sommerfeld Wilson ratio and the dynamic scaling of spin-lattice relaxation rate divided by T [27(1/T1T)] with static susceptibility suggests admixed ferromagnetic correlations. 27(1/T1T) simultaneously tracks the valence fluctuations from the 4f -Yb ions in the high temperature range and field dependent antiferromagnetic correlations among partially Kondo screened Fe 3d moments at low temperature, the latter evolve out of an Yb 4f admixed conduction band.Comment: To appear in Phys. Rev. Let

Balance Functions, Correlations, Charge Fluctuations and Interferometry

Connections between charge balance functions, charge fluctuations and correlations are presented. It is shown that charge fluctuations can be directly expressed in terms of a balance functions under certain assumptions. The distortion of charge balance functions due to experimental acceptance is discussed and the effects of identical boson interference is illustrated with a simple model.Comment: 1 eps figure included. 5 pages in revtex

Particle acceleration and the origin of gamma-ray emission from Fermi Bubbles

Fermi LAT has discovered two extended gamma-ray bubbles above and below the galactic plane. We propose that their origin is due to the energy release in the Galactic center (GC) as a result of quasi-periodic star accretion onto the central black hole. Shocks generated by these processes propagate into the Galactic halo and accelerate particles there. We show that electrons accelerated up to ~10 TeV may be responsible for the observed gamma-ray emission of the bubbles as a result of inverse Compton (IC) scattering on the relic photons. We also suggest that the Bubble could generate the flux of CR protons at energies > 10^15 eV because the shocks in the Bubble have much larger length scales and longer lifetimes in comparison with those in SNRs. This may explain the the CR spectrum above the knee.Comment: 5 pages, 4 figures. Expanded version of the contribution to the 32nd ICRC, Beijing, #0589. To appear in the proceeding

Measurements of reactive nitrogen produced by tropical thunderstorms during BIBLE-C

The Biomass Burning and Lightning Experiment phase C (BIBLE-C) aircraft mission was carried out near Darwin, Australia (12°S, 131°E) in December 2000. This was the first aircraft experiment designed to estimate lightning NO production rates in the tropics, where production is considered to be most intense. During the two flights (flights 10 and 13 made on December 9 and 11-12, respectively) enhancements of NOx (NO + NO2) up to 1000 and 1600 parts per trillion by volume (pptv, 10-s data) were observed at altitudes between 11.5 and 14 km. The Geostationary Meteorological Satellite (GMS) cloud (brightness temperature) data and ground-based lightning measurements by the Global Positioning and Tracking System (GPATS) indicate that there were intensive lightning events over the coast of the Gulf of Carpentaria, which took place upstream from our measurement area 10 to 14 h prior to the measurements. For these two flights, air in which NOx exceeded 100 pptv extended over 620 × 140 and 400 × 170 km2 (wind direction x perpendicular direction), respectively, suggesting a significant impact of lightning NO production on NOx levels in the tropics. We estimate the amount of NOx observed between 11.5 and 14 km produced by the thunderstorms to be 3.3 and 1.8 × 1025 NO molecules for flights 10 and 13, respectively. By using the GPATS lightning flash count data, column NO production rates are estimated to be 1.9-4.4 and 21-49 × 1025 NO molecules per single flash for these two flight data sets. In these estimations, it is assumed that the column NO production between 0 and 16 km is greater than the observed values between 11.5 and 14 km by a factor of 3.2, which is derived using results reported by Pickering et al. (1998). There are however large uncertainties in the GPATS lightning data in this study and care must be made when the production rates are referred. Uncertainties in these estimates are discussed. The impact on the ozone production rate is also described. Copyright 2007 by the American Geophysical Union