380 research outputs found
Neutrinos in dense quark matter and cooling of compact stars
We discuss that observational constraints on neutrino cooling processes may
restrict the spectrum of quark matter phases admissible for compact star
interiors.Comment: 3 pages, contribution to International School of Nuclear Physics on
"Neutrinos in Cosmology, in Astro-, Particle- and Nuclear Physics,
Erice-Sicily, September 16-24, 200
Neutrino emissivities and bulk viscosity in neutral two-flavor quark matter
We study thermodynamic and transport properties for the isotropic
color-spin-locking (iso-CSL) phase of two-flavor superconducting quark matter
under compact star constraints within a NJL-type chiral quark model. Chiral
symmetry breaking and the phase transition to superconducting quark matter
leads to a density dependent change of quark masses, chemical potentials and
diquark gap. A self-consistent treatment of these physical quantities
influences on the microscopic calculations of transport properties. We present
results for the iso-CSL direct URCA emissivities and bulk viscosities, which
fulfill the constraints on quark matter derived from cooling and rotational
evolution of compact stars. We compare our results with the phenomenologically
successful, but yet heuristic 2SC+X phase. We show that the microscopically
founded iso-CSL phase can replace the purely phenomenological 2SC+X phase in
modern simulations of the cooling evolution for compact stars with color
superconducting quark matter interior.Comment: 15 pages, 6 figures, references added, text improve
Ionospheric response during low and high solar activity
We analyse solar extreme ultraviolet (EUV) irradiance observed by the Solar EUV Experiment (SEE) onboard the Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) satellite, and solar proxies (the F10.7 index, and Mg-II index), and compare their variability with the one of the global mean Total Electron Content (GTEC). Cross-wavelet analysis confirms the joint 27 days periodicity in GTEC and solar proxies. We focus on a comparison for solar minimum (2007-2009) and maximum (2013-2015) and find significant differences in the correlation during low and high solar activity years. GTEC is delayed by
approximately 1-2 days in comparison to solar proxies during both low and high solar activity at the 27 days solar rotation period. To investigate the dynamics of the delay process, Coupled Thermosphere Ionosphere Plasmasphere electrodynamics model simulations have been performed for low and high solar activity conditions. Preliminary results using cross correlation analysis show an ionospheric delay of 1 day in GTEC with respect to the F10.7 index during low and high solar activity.Wir analysieren vom Solar Extreme Ultraviolet Experiment (SEE) an Bord des Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) Satelliten gemessene solare EUV-Irradianzen, solare Proxies (den F10.7-Index und denMg-II-Index), und vergleichen deren VariabilitĂ€t mit derjenigen des global gemittelten Gesamtelektronengehalts (GTEC). Kreuzwaveletanalysen bestĂ€tigen eine gemeinsame VariabilitĂ€t im Periodenbereich der solaren Rotation (27 Tage). Wir vergleichen insbesondere den Zusammenhang wĂ€hrend des solaren Minimums (2007- 2009) und Maximums (2013-2015), wobei signifikante Unterschiede der Korrelation zwischen solaren und ionosphĂ€rischen Parametern auftreten. Es tritt eine Verzögerung der Maxima und Minima von GTEC gegenĂŒber denjenigen der solaren Proxies von
einem Tag sowohl im solaren Minimum als auch im solaren Maximum auf
Evaluating the performance of ionic liquid coatings for mitigation of spacecraft surface charges
To reduce the impact of charging effects on satellites, cheap and lightweight
conductive coatings are desirable. We mimic space-like charging environments in
ultra-high vacuum (UHV) chambers during deposition of charges via the electron
beam of a scanning electron microscope (SEM). We use the charge induced
signatures in SEM images of a thin ionic liquid (IL) film on insulating
surfaces such as glass, to assess the general performance of such coatings. In
order to get a reference structure in SEM, the samples were structured by
nanosphere lithography and coated with IL. The IL film (we choose BMP DCA, due
to its beneficial physical properties) was applied ex situ and a thickness of
10 to 30 nm was determined by reflectometry. Such an IL film is stable under
vacuum conditions. It would also only lead to additional mass of below 20
mg/m. At about 5 A/m e/(sm), a typical
sample charging rate in SEM, imaging is possible with no noticeable contrast
changes over many hours; this electron current density is already 6 orders of
magnitudes higher than "worst case geosynchronous environments" of
A/m. Measurements of the surface potential are used for
further insights in the reaction of IL films to the electron beam of a SEM.
Participating mechanisms such as polarization or reorientation will are
discussed.Comment: Submitted to Proceedings of the 14th IAA Symposium on Small
Satellites for Earth System Observatio
The response of the ionospheric peak electron density (NmF2) to solar activity)
The ionospheric peak electron density NmF2, simulated with the Coupled
Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) model was used to
study the ionospheric response to solar flux in years of low (2008) and high (2013)
solar activity. The CTIPe NmF2 was compared to the Whole Atmosphere Community
Climate Model with Thermosphere and Ionosphere Extension (WACCM-X) and the
Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)
NmF2 in March and July of 2008 and 2013. The comparison shows that the CTIPe NmF2 is lower than the COSMIC andWACCM-X NmF2. Both models successfully reproduce the semi-annual variations seen in the COSMIC observations. Analysis of the 27-day variations of the CTIPe NmF2 shows that the midnight NmF2 deviations are stronger than the midday deviations. In addition, at low solar activity, the 27-day variations of NmF2 are larger in the Southern Hemisphere, while at high solar activity, the 27-day variations of NmF2 are larger at the equator and in the Northern Hemisphere.
An ionospheric delay was estimated with CTIPe simulated NmF2 at the 27-day solar
rotation period during low and high solar activity. During low (high) solar activity, an
ionospheric delay of about 12 (34) hours is predicted indicating an increasing ionospheric delay with solar activity.Die maximale ionosphÀrische Elektronendichte NmF2, die mit dem Coupled Thermosphere Ionosphere Plasmasphere electrodynamics (CTIPe) Modell
simuliert wurde, wurde zur Untersuchung der ionosphÀrischen Reaktion in Jahren
mit geringer (2008) und hoher (2013) SonnenaktivitÀt verwendet. CTIPe vorhergesagte NmF2 wurde mit derjenigen des Whole Atmosphere Community Climate Model with Thermosphere and Ionosphere Extension (WACCM-X) und Messwerten des Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) im MÀrz und Juli der Jahre 2008 und 2013 verglichen. Der Vergleich zeigt, dass NmF2
aus CTIPe geringer ist als das COSMIC gemessene und von WACCM-X simulierte.
Beide Modelle reproduzieren erfolgreich die von COSMIC beobachteten halbjÀhrlichen
Schwankungen. Die Analyse der 27-tÀgigen Schwankungen des CTIPe NmF2 zeigt,
dass die mitternÀchtlichen NMF2-Abweichungen stÀrker sind als diejenigen am Mittag.
AuĂerdem sind bei geringer SonnenaktivitĂ€t die 27-Tage-Abweichungen von NmF2 in der SĂŒdhemisphĂ€re gröĂer, wĂ€hrend bei hoher SonnenaktivitĂ€t die 27-Tage-Abweichungen von NmF2 am Ăquator und in der NordhemisphĂ€re gröĂer sind.
Die ionosphÀrische Verzögerung wÀhrend geringer und hoher SonnenaktivitÀt wurde
fĂŒr die 27-tĂ€gige Sonnenrotation mit CTIPe simuliert. Bei geringer (hoher) SonnenaktivitĂ€t wird eine ionosphĂ€rische Verzögerung von etwa 12 (34) Stunden beobachtet, was auf eine zunehmende ionosphĂ€rische Verzögerung mit zunehmender SonnenaktivitĂ€t hinweist
- âŠ