A fast rotating magnetized white dwarf, AEAquarii, was observed with Suzaku, in 2005 October–November and 2006 October with exposures of 53.1 and 42.4 ks, respectively. In addition to clear spin modulation in the 0.5–10 keV band of the XIS data at the barycentric period of 33.0769$\pm$0.0001 s, the 10–30 keV HXD data in the second half of the 2005 observation also showed statistically significant periodic signals at a consistent period. On that occasion, the spin-folded HXD light curve exhibited two sharp spikes separated by $\sim$0.2 cycles in phase, in contrast to approximately sinusoidal profiles observed at energies below $\sim$4 keV. The folded 4–10 keV XIS light curves are understood to be a superposition of those two types of pulse profiles. The phase-averaged 1.5–10 keV spectra can be reproduced by two thermal components with temperatures of $2.90_{-0.16}^{+0.20}$keV and 0.53${\;}_{-0.13}^{+0.14}$keV, but the 12–25 keV HXD data show a significant excess above the extrapolated model. This excess can be explained by either a power-law model with a photon index of $1.12_{-0.62}^{+0.63}$ or a third thermal component with a temperature of 54${\;}_{-47}^{+26}$keV. At a distance of 102 pc, the 4–30 keV luminosities of the thermal and the additional components become $1.7_{-0.6}^{+1.3}$ and 5.3${\;}_{-0.3}^{+15.3}$$\times10^{29}$ergs$^{-1}$, respectively. The latter corresponds to 0.09% of the spin-down energy of the object. Possible emission mechanisms of the hard pulsations are discussed, including non-thermal ones, in particular.

We present results from the Suzaku observations of the dwarf nova SS Cyg in quiescence and outburst in 2005 November. High sensitivity of the HXD PIN and high spectral resolution of the XIS enable us to determine plasma parameters with unprecedented precision. The maximum temperature of the plasma in quiescence 20.4 +4.0 −2.6 (stat.)±3.0(sys.) keV is significantly higher than that in outburst 6.0 +0.2 −1.3 keV. The elemental abundances are close to the solar ones for the medium-Z elements (Si, S, Ar) whereas they decline both in lighter and heavier elements, except for that of carbon which is 2 solar at least. The solid angle of the reflector subtending over an optically thin thermal plasma is Ω Q /2π = 1.7 ± 0.2 (stat.) ± 0.1 (sys.) in quiescence. A 6.4 keV iron Kα line is resolved into narrow and broad components. These facts indicate that both the white dwarf and the accretion disk contribute to the reflection. We consider the standard optically thin boundary layer as the most plausible picture for the plasma configuration in quiescence. The solid angle of the reflector in outburst Ω O /2π = 0.9 +0.5 −0.4 and a broad 6.4 keV iron line indicate that the reflection in outburst originates from the accretion disk and an equatorial accretion belt. The broad 6.4 keV line suggests that the optically thin thermal plasma is distributed on the accretion 1 arXiv:0809.3559v2 [astro-ph] 8 Oct 2008 disk like solar coronae.

Alpha particles with energies on the order of megaelectronvolts will be the main source of plasma heating in future magnetic confinement fusion reactors. Instead of heating fuel ions, most of the energy of alpha particles is transferred to electrons in the plasma. Furthermore, alpha particles can also excite Alfvénic instabilities, which were previously considered to be detrimental to the performance of the fusion device. Here we report improved thermal ion confinement in the presence of megaelectronvolts ions and strong fast ion-driven Alfvénic instabilities in recent experiments on the Joint European Torus. Detailed transport analysis of these experiments reveals turbulence suppression through a complex multi-scale mechanism that generates large-scale zonal flows. This holds promise for more economical operation of fusion reactors with dominant alpha particle heating and ultimately cheaper fusion electricity.

We model the post-shock accretion column (PSAC) of intermediate polars (IPs) with the specific accretion rate being floated in the range between 0.0001 and 100 g cm −2 s −1 and the metal abundance in the range between 0.1 and 2 times of the solar, and taking into account the gravitational potential with radial dependence, non-equipartition between ions and electrons, and ionization non-equilibrium. We fully take into account the dipole geometry for the PSAC. The specific accretion rate significantly affects the structure of the PSAC, and there is a critical rate below which the profiles of the density and temperature distributions deviate from those of the standard model. This happens when the specific accretion rate is 1 and 30 g cm −2 s −1 for the 0.7 and 1.2 M ⊙ white dwarf (WD), respectively, or the height of the PSAC becomes 1% of the white dwarf radius. Below the critical specific accretion rate, the present standard model is no longer valid. We calculate the spectra of the PSACs with the density and temperature distributions described above. Input parameters are the mass of the WD, the specific accretion rate, and the metal abundance. The spectral shape is constant and consistent with that of the standard model if the specific accretion rate is larger than the critical value, except for density-dependent emission lines. Below the critical specific accretion rate, on the other hand, the spectra soften as the specific accretion rate decreases. Associated with this, the maximum temperature of the PSAC becomes significantly lower than that of the standard model below the critical specific accretion rate. Although the ionization non-equilibrium are also considered in the spectral calculation, the effects are limited because the radiation from ionization nonequilibrium plasma is a few percent of the whole at most.

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