Search results for "Physics::Space Physics"
showing 10 items of 357 documents
Models and data analysis tools for the Solar Orbiter mission
2020
All authors: Rouillard, A. P.; Pinto, R. F.; Vourlidas, A.; De Groof, A.; Thompson, W. T.; Bemporad, A.; Dolei, S.; Indurain, M.; Buchlin, E.; Sasso, C.; Spadaro, D.; Dalmasse, K.; Hirzberger, J.; Zouganelis, I.; Strugarek, A.; Brun, A. S.; Alexandre, M.; Berghmans, D.; Raouafi, N. E.; Wiegelmann, T.; Pagano, P.; Arge, C. N.; Nieves-Chinchilla, T.; Lavarra, M.; Poirier, N.; Amari, T.; Aran, A.; Andretta, V.; Antonucci, E.; Anastasiadis, A.; Auchère, F.; Bellot Rubio, L.; Nicula, B.; Bonnin, X.; Bouchemit, M.; Budnik, E.; Caminade, S.; Cecconi, B.; Carlyle, J.; Cernuda, I.; Davila, J. M.; Etesi, L.; Espinosa Lara, F.; Fedorov, A.; Fineschi, S.; Fludra, A.; Génot, V.; Georgoulis, M. K.; Gilbe…
The XMM-Newton Optical Monitor survey of the Taurus molecular cloud
2007
The Optical Monitor (OM) on-board XMM-Newton obtained optical/ultraviolet data for the XMM-Newton Extended Survey of the Taurus Molecular Cloud (XEST), simultaneously with the X-ray detectors. With the XEST OM data, we aim to study the optical and ultraviolet properties of TMC members, and to do correlative studies between the X-ray and OM light curves. In particular, we aim to determine whether accretion plays a significant role in the optical/ultraviolet and X-ray emissions. The Neupert effect in stellar flares is also investigated. Coordinates, average count rates and magnitudes were extracted from OM images, together with light curves with low time resolution (a few kiloseconds). For a …
Insolation cycles as a major control equatorial Indian Ocean primary production
1997
Analysis of a continuous sedimentary record taken in the Maldives indicates that strong primary production fluctuations (70 to 390 grams of carbon per square meter per year) have occurred in the equatorial Indian Ocean during the past 910,000 years. The record of primary production is coherent and in phase with the February equatorial insolation, whereas it shows diverse phase behavior with δ 18 O, depending on the orbital frequency (eccentricity, obliquity, or precession) examined. These observations imply a direct control of productivity in the equatorial oceanic system by insolation. In the equatorial Indian Ocean, productivity is driven by the wind intensity of westerlies, which is rel…
Compensation of Oxygen Transmittance Effects for Proximal Sensing Retrieval of Canopy–Leaving Sun–Induced Chlorophyll Fluorescence
2018
Estimates of Sun–Induced vegetation chlorophyll Fluorescence (SIF) using remote sensing techniques are commonly determined by exploiting solar and/or telluric absorption features. When SIF is retrieved in the strong oxygen (O 2 ) absorption features, atmospheric effects must always be compensated. Whereas correction of atmospheric effects is a standard airborne or satellite data processing step, there is no consensus regarding whether it is required for SIF proximal–sensing measurements nor what is the best strategy to be followed. Thus, by using simulated data, this work provides a comprehensive analysis about how atmospheric effects impact SIF estimations on proximal sensing, regarding: (…
The intensity contrast of solar photospheric faculae and network elements : II. Evolution over the rising phase of solar cycle 23
2006
We studied the radiative properties of small magnetic elements (active region faculae and the network) during the rising phase of solar cycle 23 from 1996 to 2001, determining their contrasts as a function of heliocentric angle, magnetogram signal, and the solar cycle phase. We combined near-simultaneous full disk images of the line-of-sight magnetic field and photospheric continuum intensity provided by the MDI instrument on board the SOHO spacecraft. Sorting the magnetogram signal into different ranges allowed us to distinguish between the contrast of different magnetic structures. We find that the contrast center-to-limb variation (CLV) of these small magnetic elements is independent of …
Direct Measurement of Focusing Fields in Active Plasma Lenses
2018
Physical review accelerators and beams 21(12), 122801 (2018). doi:10.1103/PhysRevAccelBeams.21.122801
Gravity Probe Spin: Prospects for measuring general-relativistic precession of intrinsic spin using a ferromagnetic gyroscope
2020
An experimental test at the intersection of quantum physics and general relativity is proposed: measurement of relativistic frame dragging and geodetic precession using intrinsic spin of electrons. The behavior of intrinsic spin in spacetime dragged and warped by a massive rotating body is an experimentally open question, hence the results of such a measurement could have important theoretical consequences. Such a measurement is possible by using mm-scale ferromagnetic gyroscopes in orbit around the Earth. Under conditions where the rotational angular momentum of a ferromagnet is sufficiently small, a ferromagnet's angular momentum is dominated by atomic electron spins and is predicted to e…
A Precessing Ferromagnetic Needle Magnetometer
2016
A ferromagnetic needle is predicted to precess about the magnetic field axis at a Larmor frequency $\Omega$ under conditions where its intrinsic spin dominates over its rotational angular momentum, $N\hbar \gg I\Omega$ ($I$ is the moment of inertia of the needle about the precession axis and $N$ is the number of polarized spins in the needle). In this regime the needle behaves as a gyroscope with spin $N\hbar$ maintained along the easy axis of the needle by the crystalline and shape anisotropy. A precessing ferromagnetic needle is a correlated system of $N$ spins which can be used to measure magnetic fields for long times. In principle, by taking advantage of rapid averaging of quantum unce…
A stellar flare-coronal mass ejection event revealed by X-ray plasma motions
2019
Coronal mass ejections (CMEs), often associated with flares, are the most powerful magnetic phenomena occurring on the Sun. Stars show magnetic activity levels up to 10^4 times higher, and CME effects on stellar physics and circumstellar environments are predicted to be significant. However, stellar CMEs remain observationally unexplored. Using time-resolved high-resolution X-ray spectroscopy of a stellar flare on the active star HR 9024 observed with Chandra/HETGS, we distinctly detected Doppler shifts in S XVI, Si XIV, and Mg XII lines that indicate upward and downward motions of hot plasmas (~10-25 MK) within the flaring loop, with velocity v~100-400 km/s, in agreement with a model of fl…
Comparison between probe stagnation point heat flux measurements and correlation formulas in SCIROCCO plasma wind tunnel tests
2012
A large part of the SCIROCCO Arc Heater Performance Map has been investigated. The heat flux measurements at the stagnation point of t he facility Calibratio Probe have been used to find an experimental fit. Such a formula ha s been compared with the predictions of the De Filippis-Serpico equation and the well known Fay-Riddell formula. Finally the experimental fit has been also compared with the Sa gner-Verant formula obtained at the ONERA F4 hypersonic plasma wind tunnel.