Search Publications
A new parametrization for dark energy density and future deceleration
Mamon, Abdulla Al
In this work, we have proposed a general dark energy density parametrization to study the evolution of the universe. We have also constrained the model parameters using the combination of Type Ia supernova (SNIa), baryonic acoustic oscillations (BAO), cosmic microwave background radiation (CMB) and observational H(z) datasets. For the H(z) dataset…
Soft proton flux on ATHENA focal plane and its impact on the magnetic diverter design
Jacquey, Christian; Piro, Luigi; Molendi, Silvano +11 more
The experience gained with the current generation of X-ray telescopes like Chandra and XMM-Newton has shown that low energy "soft" protons can pose a severe threat to the possibility to exploit scientific data, reducing the available exposure times by up to 50% and introducing a poorly reproducible background component. These soft protons are pres…
The Formation of an Oxygen Wave by Magnetic Reconnection
Tenfjord, P.; Hesse, M.; Norgren, C.
Oxygen of ionospheric origin is a ubiquitous particle species in magnetospheric dynamics. We investigate how an oxygen population influences magnetic reconnection and how it is energized, using particle-in-cell simulations. The oxygen population is inserted initially in the inflow region, at two equal distances above and below the current sheet, a…
The 2015 Summer Solstice Storm: One of the Major Geomagnetic Storms of Solar Cycle 24 Observed at Ground Level
Augusto, C. R. A.; Navia, C. E.; de Oliveira, M. N. +8 more
We report on the 22 - 23 June 2015 geomagnetic storm that occurred at the summer solstice. There have been fewer intense geomagnetic storms during the current solar cycle, Solar Cycle 24, than in the previous cycle. This situation changed after mid-June 2015, when one of the largest solar active regions (AR 12371) of Solar Cycle 24 that was locate…
Searching for g modes. I. A new calibration of the GOLF instrument
Corbard, T.; Appourchaux, T.; Boumier, P. +1 more
Context. The recent claims of g-mode detection have restarted the search for these potentially extremely important modes. These claims can be reassessed in view of the different data sets available from the SoHO instruments and ground-based instruments.
Aims: We produce a new calibration of the GOLF data with a more consistent p-mode amplitud…
Magnetosheath Reconnection Before Magnetopause Reconnection Driven by Interplanetary Tangential Discontinuity: A Three-Dimensional Global Hybrid Simulation With Oblique Interplanetary Magnetic Field
Wang, Xueyi; Lin, Yu; Du, Aimin +1 more
Terrestrial dayside dynamics associated with a southward turning, oblique interplanetary magnetic field (IMF) carried by an interplanetary tangential discontinuity (TD) is investigated by performing a three-dimensional global-scale hybrid simulation systematically for cases in which the incoming solar wind TD possesses various magnetic field rotat…
Independent Estimation of Black Hole Mass for the γ-ray-detected Archetypal Narrow-line Seyfert 1 Galaxy 1H 0323+342 from X-Ray Variability
Komossa, S.; Jin, Chichuan; Yuan, Weimin +2 more
γ-ray-detected narrow-line Seyfert 1 galaxies (NLS1s) are a newly discovered class of radio-loud active galactic nuclei (AGNs) that launch powerful jets that are generally found only in blazars and radio galaxies. However, their black hole (BH) masses as estimated from their broad emission lines are an order of magnitude or more lower than those i…
More about solar g modes
Fossat, E.; Schmider, F. X.
Context. The detection of asymptotic solar g-mode parameters was the main goal of the GOLF instrument onboard the SOHO space observatory. This detection has recently been reported and has identified a rapid mean rotation of the solar core, with a one-week period, nearly four times faster than all the rest of the solar body, from the surface to the…
Constraining the period of the ringed secondary companion to the young star J1407 with photographic plates
Reichart, D. E.; Grindlay, J. E.; Haislip, J. B. +16 more
Context. The 16 Myr old star 1SWASP J140747.93-394542.6 (V1400 Cen) underwent a series of complex eclipses in May 2007, interpreted as the transit of a giant Hill sphere filling debris ring system around a secondary companion, J1407b. No other eclipses have since been detected, although other measurements have constrained but not uniquely determin…
Spatial Organization of Seven Extreme Solar Energetic Particle Events
Wang, Haimin; Vainio, Rami; Pohjolainen, Silja +4 more
Emission of relativistic protons and helium responsible for extreme solar particle events (ground level enhancements (GLEs)) is often structured. We investigate its organization depending on the eruption stage characterized by the heliocentric height of associated coronal mass ejections (CMEs). Seven GLEs are considered: events on 1997 November 6,…