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Radial evolution of sunward strahl electrons in the inner heliosphere
The heliospheric magnetic field (HMF) exhibits local inversions, in which the field apparently “bends back” upon itself. Candidate mechanisms to produce these inversions include various configurations of upstream interchange reconnection; either in the heliosphere, or in the corona where the solar wind is formed. Explaining the source of these inversions, and how they evolve in time and space, is thus an important step towards explaining the origins of the solar wind. Inverted heliospheric magnetic field lines can be identified by the anomalous sunward (i.e. inward) streaming of the typically anti-sunward propagating, field aligned (or anti-aligned), beam of electrons known as the “strahl”. We test if the pitch angle distribution (PAD) properties of sunward-propagating strahl are different from those of outward strahl.We perform a statistical study of strahl observed by the Helios spacecraft, over heliocentric distances spanning ≈ 0.3 – 1 AU. We find that sunward strahl PADs are broader and less intense than their outward directed counterparts; particularly at distances 0.3 – 0.75 AU. This is consistent with sunward strahl being subject to additional, path-length dependent, scattering in comparison to outward strahl.We conclude that the longer and more variable path from the Sun to the spacecraft, along inverted magnetic field, leads to this additional scattering. The results also suggest that the relative importance of scattering along this additional path length drops off with heliocentric distance. These results can be explained by a relatively simple, constant-rate, scattering process
Hydrogen Balmer line formation in solar flares affected by return currents
Aims. We investigate the effect of the electric return currents in solar
flares on the profiles of hydrogen Balmer lines. We consider the monoenergetic
approximation for the primary beam and runaway model of the neutralizing return
current. Methods. Propagation of the 10 keV electron beam from a coronal
reconnection site is considered for the semiempirical chromosphere model F1. We
estimate the local number density of return current using two approximations
for beam energy fluxes between and . Inelastic collisions of beam and return-current electrons
with hydrogen are included according to their energy distributions, and the
hydrogen Balmer line intensities are computed using an NLTE radiative transfer
approach. Results. In comparison to traditional NLTE models of solar flares
that neglect the return-current effects, we found a significant increase
emission in the Balmer line cores due to nonthermal excitation by return
current. Contrary to the model without return current, the line shapes are
sensitive to a beam flux. It is the result of variation in the return-current
energy that is close to the hydrogen excitation thresholds and the density of
return-current electrons.Comment: 4 pages, 3 figures, 1 table, accepted for publication in Astronomy
and Astrophysics Letter
Secondary Osteoporosis: Endocrine and Metabolic Causes of Bone Mass Deterioration
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Secondary osteoporosis results from medical conditions or treatments that interfere with the attainment of peak bone mass and/or may predispose to accelerated bone loss. Although secondary osteoporosis is less common, it is becoming more frequently diagnosed. Apart from the welldefined risk of secondary osteoporosis in patients requiring long-term corticosteroids therapy, an increasing list of dietary, lifestyle, endocrine, metabolic, and other causes of bone mass deterioration has been identified (Table 1). Recently it has been demonstrated that, in contrast to primary osteoporosis which is associated with age, gender, and family history, secondary osteoporosis shows a prevalence in men similar to that in women (men 21 % versus women 17.5%
A new proof for the decidability of D0L ultimate periodicity
We give a new proof for the decidability of the D0L ultimate periodicity
problem based on the decidability of p-periodicity of morphic words adapted to
the approach of Harju and Linna.Comment: In Proceedings WORDS 2011, arXiv:1108.341
The Critical Exponent is Computable for Automatic Sequences
The critical exponent of an infinite word is defined to be the supremum of
the exponent of each of its factors. For k-automatic sequences, we show that
this critical exponent is always either a rational number or infinite, and its
value is computable. Our results also apply to variants of the critical
exponent, such as the initial critical exponent of Berthe, Holton, and Zamboni
and the Diophantine exponent of Adamczewski and Bugeaud. Our work generalizes
or recovers previous results of Krieger and others, and is applicable to other
situations; e.g., the computation of the optimal recurrence constant for a
linearly recurrent k-automatic sequence.Comment: In Proceedings WORDS 2011, arXiv:1108.341
Scattering polarization in the CaII Infrared Triplet with Velocity Gradients
Magnetic field topology, thermal structure and plasma motions are the three
main factors affecting the polarization signals used to understand our star. In
this theoretical investigation, we focus on the effect that gradients in the
macroscopic vertical velocity field have on the non-magnetic scattering
polarization signals, establishing the basis for general cases. We demonstrate
that the solar plasma velocity gradients have a significant effect on the
linear polarization produced by scattering in chromospheric spectral lines. In
particular, we show the impact of velocity gradients on the anisotropy of the
radiation field and on the ensuing fractional alignment of the CaII levels, and
how they can lead to an enhancement of the zero-field linear polarization
signals. This investigation remarks the importance of knowing the dynamical
state of the solar atmosphere in order to correctly interpret
spectropolarimetric measurements, which is important, among other things, for
establishing a suitable zero field reference case to infer magnetic fields via
the Hanle effect.Comment: 14 pages, 10 figures, 3 appendixes, accepted for publication in Ap
Controllable Text Generation for All Ages : Evaluating a Plug-and-Play Approach to Age-Adapted Dialogue
Funding Information: We would like to thank the four anonymous GEM reviewers for their valuable feedback and the participants of our crowdsourcing experiments. The work received funding from the University of Amsterdam’s Research Priority Area Human(e) AI and from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 819455).Publisher PD
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