Noise in a Calorimeter Readout System Using Periodic Sampling

Fourier transform analysis of the calorimeter noise problem gives quantitative results on a) the time-height correlation, b) the effect of background on optimal shaping and on the ENC, c) sampling frequency requirements, and d) the relation between sampling frequency and the required quantization error

Effects of magnetic fields on radiatively overstable shock waves

We discuss high-resolution simulations of one-dimensional, plane-parallel shock waves with mean speeds between 150 and 240 km/s propagating into gas with Alfven velocities up to 40 km/s and outline the conditions under which these radiative shocks experience an oscillatory instability in the cooling length, shock velocity, and position of the shock front. We investigate two forms of postshock cooling: a truncated single power law and a more realistic piecewise power law. The degree of nonlinearity of the instability depends strongly on the cooling power law and the Alfven Mach number: for power-law indices \alpha < 0 typical magnetic field strengths may be insufficient either to stabilize the fundamental oscillatory mode or to prevent the oscillations from reaching nonlinear amplitudes.Comment: 11 text pages, LaTeX/AASTeX (aaspp4); 5 figures; accepted by Ap

Energy spectra of 3He-rich solar energetic particles associated with coronal waves

In addition to their anomalous abundances, 3He-rich solar energetic particles (SEPs) show puzzling energy spectral shapes varying from rounded forms to power laws where the later are characteristics of shock acceleration. Solar sources of these particles have been often associated with jets and narrow CMEs, which are the signatures of magnetic reconnection involving open field. Recent reports on new associations with large-scale EUV waves bring new insights on acceleration and transport of 3He-rich SEPs in the corona. We examined energy spectra for 32 3He-rich SEP events observed by ACE at L1 near solar minimum in 2007-2010 and compared the spectral shapes with solar flare signatures obtained from STEREO EUV images. We found the events with jets or brightenings tend to be associated with rounded spectra and the events with coronal waves with power laws. This suggests that coronal waves may be related to the unknown second stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs.Comment: Presented at 15th Annual International Astrophysics Conference "The Science of Ed Stone". Accepted for publication in Journal of Physics: Conference Serie

The Dynamics of Radiative Shock Waves: Linear and Nonlinear Evolution

The stability properties of one-dimensional radiative shocks with a power-law cooling function of the form $\Lambda \propto \rho^2T^\alpha$ are the main subject of this work. The linear analysis originally presented by Chevalier & Imamura, is thoroughfully reviewed for several values of the cooling index $\alpha$ and higher overtone modes. Consistently with previous results, it is shown that the spectrum of the linear operator consists in a series of modes with increasing oscillation frequency. For each mode a critical value of the cooling index, $\alpha_\textrm{c}$, can be defined so that modes with $\alpha < \alpha_\textrm{c}$ are unstable, while modes with $\alpha > \alpha_\textrm{c}$ are stable. The perturbative analysis is complemented by several numerical simulations to follow the time-dependent evolution of the system for different values of $\alpha$. Particular attention is given to the comparison between numerical and analytical results (during the early phases of the evolution) and to the role played by different boundary conditions. It is shown that an appropriate treatment of the lower boundary yields results that closely follow the predicted linear behavior. During the nonlinear regime, the shock oscillations saturate at a finite amplitude and tend to a quasi-periodic cycle. The modes of oscillations during this phase do not necessarily coincide with those predicted by linear theory, but may be accounted for by mode-mode coupling.Comment: 33 pages, 12 figures, accepted for publication on the Astrophysical Journa

Multi-Spacecraft Observations of Recurrent 3He-Rich Solar Energetic Particles

We study the origin of 3He-rich solar energetic particles (<1 MeV/nucleon) that are observed consecutively on STEREO-B, ACE, and STEREO-A spacecraft when they are separated in heliolongitude by more than 90{\deg}. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region producing X-ray flares accompanied by prompt electron events, when it was near the west solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged active region near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of 1) solar regions with long-lasting conditions for 3He acceleration and 2) solar energetic 3He that is temporary confined/re-accelerated in interplanetary space.Comment: accepted for publication in The Astrophysical Journa

EIS/Hinode observations of Doppler flow seen through the 40 arcsec wide slit

The Extreme ultraviolet Imaging Spectrometer (EIS) on board Hinode is the first solar telescope to obtain wide slit spectral images that can be used for detecting Doppler flows in transition region and coronal lines on the Sun and to relate them to their surrounding small scale dynamics. We select EIS lines covering the temperature range 6x10^4 K to 2x10^6 K that give spectrally pure images of the Sun with the 40 arcsec slit. In these images Doppler shifts are seen as horizontal brightenings. Inside the image it is difficult to distinguish shifts from horizontal structures but emission beyond the image edge can be unambiguously identified as a line shift in several lines separated from others on their blue or red side by more than the width of the spectrometer slit (40 pixels). In the blue wing of He II, we find a large number of events with properties (size and lifetime) similar to the well-studied explosive events seen in the ultraviolet spectral range. Comparison with X-Ray Telescope (XRT) images shows many Doppler shift events at the footpoints of small X-ray loops. The most spectacular event observed showed a strong blue shift in transition region and lower corona lines from a small X-ray spot that lasted less than 7 min. The emission appears to be near a cool coronal loop connecting an X-ray bright point to an adjacent region of quiet Sun. The width of the emission implies a line-of-sight velocity of 220 km/s. In addition, we show an example of an Fe XV shift with a velocity about 120 km/s, coming from what looks like a narrow loop leg connecting a small X-ray brightening to a larger region of X-ray emission.Comment: 12 pages, 8 figures, to be published in Solar Physic

Analytical, circle-to-circle low-thrust transfer trajectories with plane change

Orbit averaging techniques are used to develop analytical approximations of circle-to-circle low-thrust trajectory transfers with plane-change about the Sun. Separate expressions are developed for constant acceleration, or thrust, electric propulsion, solar sail propulsion and combined, or hybrid electric (constant acceleration or thrust) / solar sail propulsion. The analytical expressions uniquely allow the structure of circle-to-circle low-thrust trajectory transfers with plane-change about the Sun to be understood, and the optimal trajectory structure is analytically derived for each propulsion system considered. It is found that the optimal fixed thrust electric propulsion transfer reduces the orbit radius with no plane change and then performs the plane-change, while the optimal solar sail and hybrid transfers combine the reduction of orbit radius with some plane change, before then completing the plane change. The optimal level of plane change during the reduction of orbit radius is derived and it is found the analytically-derived minimum time solar sail transfer is within 1% of the numerically-derived optimal transfer. It is also found that, under the conditions considered, a sail characteristic acceleration of less than 0.5 mm/s2 can, in 5-years, attain a solar orbit that maintains the observer-to-solar pole zenith angle below 40 degrees for 25 days; the approximate sidereal rotation period of the Sun. However, a sail characteristic acceleration of more than 0.5 mm/s2 is required to attain an observer-to-solar pole zenith angle below 30 degrees for 25 days within 5-years of launch. Finally, it was found that the hybridization of electric propulsion and solar sail propulsion was, typically, of more benefit when the system was thrust constrained than when it was mass constrained

Radiative instabilities in simulations of spherically symmetric supernova blast waves

High-resolution simulations of the cooling regions of spherically symmetric supernova remnants demonstrate a strong radiative instability. This instability, whose presence is dependent on the shock velocity, causes large-amplitude fluctuations in the shock velocity. The fluctuations begin almost immediately after the radiative phase begins (upon shell formation) if the shock velocity lies in the unstable range; they last until the shock slows to speeds less than approximately 130 km/s. We find that shock-velocity fluctuations from the reverberations of waves within the remnant are small compared to those due to the instability. Further, we find (in plane-parallel simulations) that advected inhomogeneities from the external medium do not interfere with the qualitative nature of the instability-driven fluctuations. Large-amplitude inhomogeneities may alter the phases of shock-velocity fluctuations, but do not substantially reduce their amplitudes.Comment: 18 pages text, LaTeX/AASTeX (aaspp4); 10 figures; accepted by Ap

Getting chirality right: single scalar leptoquark solutions to the (g−2)e,μ(g-2)_{e,\mu} puzzle

We identify the two scalar leptoquarks capable of generating sign-dependent contributions to leptonic magnetic moments, $R_2\sim (\mathbf{3}, \mathbf{2}, 7/6)$ and $S_1\sim (\mathbf{3}, \mathbf{1}, -1/3)$, as favoured by current measurements. We consider the case in which the electron and muon sectors are decoupled, and real-valued Yukawa couplings are specified using an up-type quark mass-diagonal basis. Contributions to $\Delta a_e$ arise from charm-containing loops and $\Delta a_\mu$ from top-containing loops -- hence avoiding dangerous LFV constraints, particularly from $\mu \to e \gamma$. The strongest constraints on these models arise from contributions to the Z leptonic decay widths, high-$p_T$ leptonic tails at the LHC, and from (semi)leptonic kaon decays. To be a comprehensive solution to the $(g-2)_{e/\mu}$ puzzle we find that the mass of either leptoquark must be $\lesssim 65$ TeV. This analysis can be embedded within broader flavour anomaly studies, including those of hierarchical leptoquark coupling structures. It can also be straightforwardly adapted to accommodate future measurements of leptonic magnetic moments, such as those expected from the Muon $g-2$ collaboration in the near future.Comment: 13 pages, 4 figures, matches published version. Error identified in initial calculation of $\mu \to e \gamma$ which, when corrected, invalidated the top-philic coupling ansatz. Models revised to represent texture with dominant charm-loop NP contribution to $\Delta a_e$, and top-loop to $\Delta a_\mu