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Register a new userEarthshine observations at high spectral resolution: Exploring and detecting metal lines in the Earths upper atmosphere
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Added by
Beatriz Gonz\\'alez-Merino
Publication date
2013
fields
Physics
and research's language is
English
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Observations of the Earth as a planet using the earthshine technique (i.e. looking at the light reflected from the darkside of the Moon), have been used for climate and astrobiology studies. They provide information about the planetary albedo, a fundamental parameter of the Earths energy balance. Here we present for the first time, observations of the earthshine taken at high spectral resolution. The high spectral resolution was chosen in order to investigate the possibility of detecting metallic layers in the Earths atmosphere of geological or meteoritic origin. The SARG echelle spectrograph at the Telescopio Nazionale Galileo in La Palma was used to acquire the earthshine data. Observations were carried out on several nights in February 2011, with the spectral resolution set at 29,000, covering a spectral range from the near-ultraviolet (360 nm) to near-infrared (1011.9 nm). While we find evidence for the detection of a Na layer in the earthshine, other atomic species are not detected, perhaps due to the low signal-to-noise ratio of the observations and the difficult telluric corrections. The Na layer is found to vary between observation dates, which we speculate is due to physical variations in mesospheric Na concentrations.
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We present long baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 870$,mu$m dust continuum emission and CO (3-2) from the protoplanetary disk around the Herbig Ae/Be star HD 100546, which is one of the few systems claimed to have two young embedded planets. These observations achieve a resolution of 4 au (3.8 mas), an rms noise of 66$mu$Jy/beam, and reveal an asymmetric ring between $sim$20-40 au with largely optically thin dust continuum emission. This ring is well fit by two concentric and overlapping Gaussian rings of different widths and a Vortex. In addition, an unresolved component is detected at a position consistent with the central star, which may trace the central inner disk ($<$2au in radius). We report a lack of compact continuum emission at the positions of both claimed protoplanets. We use this result to constrain the circumplanetary disk (CPD) mass and size of 1.44M$_{rm Earth}$ and 0.44au in the optically thin and thick regime, respectively, for the case of the previously directly imaged protoplanet candidate at $sim$55 au (HD100546 b). We compare these empirical CPD constraints to previous numerical simulations. This suggests that HD100546 b is inconsistent with several planet accretion models, while gas-starved models are also still compatible. We estimate the planetary mass as 1.65 M$_J$ by using the relation between planet, circumstellar, and circumplanetary masses derived from numerical simulations. Finally, the CO integrated intensity map shows a possible spiral arm feature that would match the spiral features identified in Near-Infrared scattered light polarized emission, which suggests a real spiral feature in the disk surface that needs to be confirmed with further observations.
The Cluster mission, launched in 2000, has produced a large database of electron flux intensity measurements in the Earths magnetosphere by the Research with Adaptive Particle Imaging Detector (RAPID)/ Imaging Electron Spectrometer (IES) instrument. However, due to background contamination of the data with high-energy electrons (>400 keV) and inner- zone protons (230-630 keV) in the radiation belts and ring current, the data have been rarely used for inner-magnetospheric science. The current paper presents two algorithms for background correction. The first algorithm is based on the empirical contamination percentages by both protons and electrons. The second algorithm uses simultaneous proton observations. The efficiencies of these algorithms are demonstrated by comparison of the corrected Cluster/RAPID/IES data with Van Allen Probes/Magnetic Electron Ion Spectrometer (MagEIS) measurements for 2012-2015. Both techniques improved the IES electron data in the radiation belts and ring current.Yearly averaged flux intensities of the two missions show the ratio of measurements close to 1. IES corrected measurements were also compared with Arase Medium-Energy Particle Experiments-Electron Analyzer (MEP-e) electron data during two conjunction periods in 2017 and also exhibited ratio close to 1. We demonstrate a scientific application of the corrected IES electron data analyzing its evolution during solar cycle. Spin-averaged yearly mean IES electron intensities in the outer belt for energies 40-400 keV at L-shell between 4 and 6 showed high positive correlation with AE index and solar wind dynamic pressure during 2001- 2016. Relationship between solar wind dynamic pressure and IES electron measurements in the outer radiation belt was derived as a uniform linear-logarithmic equation.
The impact of high-speed jets -- dynamic pressure enhancements in the magnetosheath -- on the Earths magnetopause has been observed to trigger local magnetic reconnection. We perform a three-dimensional hybrid simulation to study the magnetosheath and magnetopause under turbulent conditions using a quasi-radial southward interplanetary magnetic field (IMF). In contrast to quasi-steady reconnection with a strong southward IMF, we show that after the impact of a jet on the magnetopause, the magnetopause moves inwards, the current sheet is compressed and intensified and signatures of local magnetic reconnection are observed, showing similarities to spacecraft measurements
We report the detection of water absorption features in the dayside spectrum of the first-known hot Jupiter, 51 Peg b, confirming the star-planet system to be a double-lined spectroscopic binary. We used high-resolution (R~100,000), 3.2 micron spectra taken with CRIRES/VLT to trace the radial-velocity shift of the water features in the planets dayside atmosphere during 4 hours of its 4.23-day orbit after superior conjunction. We detect the signature of molecular absorption by water at a significance of 5.6 sigma at a systemic velocity of Vsys=-33+/-2 km/s, coincident with the host star, with a corresponding orbital velocity Kp = 133^+4.3_-3.5 km/s. This translates directly to a planet mass of Mp=0.476^+0.032_-0.031MJ, placing it at the transition boundary between Jovian and Neptunian worlds. We determine upper and lower limits on the orbital inclination of the system of 70<i (deg)<82.2. We also provide an updated orbital solution for 51 Peg b, using an extensive set of 639 stellar radial velocities measured between 1994 and 2013, finding no significant evidence of an eccentric orbit. We find no evidence of significant absorption or emission from other major carbon-bearing molecules of the planet, including methane and carbon dioxide. The atmosphere is non-inverted in the temperature-pressure region probed by these observations. The deepest absorption lines reach an observed relative contrast of 0.9x10^-3 with respect to the host star continuum flux, at an angular separation of 3 milliarcseconds. This work is consistent with a previous tentative report of K-band molecular absorption for 51 Peg b by Brogi et al. (2013).
Muon detectors and neutron monitors were recently installed at Syowa Station, in the Antarctic, to observe different types of secondary particles resulting from cosmic ray interactions simultaneously from the same location. Continuing observations will give new insight into the response of muon detectors to atmospheric and geomagnetic effects. Operation began in February, 2018 and the system has been stable with a duty-cycle exceeding 94%. Muon data shows a clear seasonal variation, which is expected from the atmospheric temperature effect. We verified successful operation by showing that the muon and neutron data are consistent with those from other locations by comparing intensity variations during a space weather event. We have established a web page to make real time data available with interactive graphics (http://polaris.nipr.ac.jp/~cosmicrays/).
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