maria luisa moriconi - Academia.edu (original) (raw)

Papers by maria luisa moriconi

AGU Fall Meeting Abstracts, Dec 1, 2008

Despite the multiple evidence of the diffuse presence of methane in Jupiter’s auroral regions, th... more Despite the multiple evidence of the diffuse presence of methane in Jupiter’s auroral regions, the mechanisms leading to the CH4 brightening observed both from ground- and space-based platforms are not yet fully understood. During the first NASA/Juno’s orbit, the on-board imager/spectrometer JIRAM (Jovian Infrared Auroral Mapper) detected the 3.3-µm methane emission on both Jupiter’s poles. The signal was found to be mostly confined within the main auroral ovals, although the lack of spectral coverage over 80°S prevented a deep investigation of the southern methane spot. The CH4 polar emissions at 3.3 µm are likely originated by non-thermal excitation mechanisms occurring above the 1 µbar level, such as auroral particle precipitation and/or Joule heating. However, aurorally driven upwelling of methane inside the main oval might also explain the enhanced concentrations of CH4 observed at the jovian poles. To address this controversy, we derive the effective temperature of methane in Jupiter’s auroral regions, which is a key information to understand the origin of the detected fluorescence. The goal is achieved by exploring three Juno’s orbits and focusing on the spectra with the highest methane emissions and the smallest contribution from other auroral features due to H3+. JIRAM measurements from the first perijove are used to investigate the northern methane brightening, while observations from perijoves 7 and 8 are examined for its southern counterpart. The analysis reveals similar temperatures in the north- and south-polar spots, mainly ranging between 400 K and 670 K.

EGUGA, Apr 1, 2017

During the first perijove passage of the Juno mission, the Jovian InfraRed Auroral Mapper (JIRAM)... more During the first perijove passage of the Juno mission, the Jovian InfraRed Auroral Mapper (JIRAM) observed a line of closely spaced oval features in Jupiter's southern hemisphere, between 30°S and 45°S. In this work, we focused on the longitudinal region covering the three ovals having higher contrast at 5 μm, i.e., between 120°W and 60°W in System III coordinates. We used the JIRAM's full spectral capability in the range 2.4-3 μm together with a Bayesian data inversion approach to retrieve maps of column densities and altitudes for an NH 3 cloud and an N 2 H 4 haze. The deep (under the saturation level) volume mixing ratio and the relative humidity for gaseous ammonia were also retrieved. Our results suggest different vortex activity for the three ovals. Updraft and downdraft together with considerations about the ammonia condensation could explain our maps providing evidences of cyclonic and anticyclonic structures.

Titan Aeronomy and Climate, Jun 1, 2016

Liquid hydrocarbons on Titan's surface were long predicted before the radar instrument onboard Ca... more Liquid hydrocarbons on Titan's surface were long predicted before the radar instrument onboard Cassini detected lakes poleward of 70°N on July 2006. Before that the Cassini Imaging Science Subsystem (ISS) observed a lake-like feature in the south pole, named Ontario Lacus, on June 2005. Here we analyze observations of Ontario Lacus taken by the Visual and Infrared Mapping Spectrometer (VIMS) on 2007 December 4, during the T38 flyby. These are the best spatially resolved images of a Titan lake to date, and were previously reported in Brown et al. (2008). We analyze images taken in the 5 micron, 2.75 micron and 2 micron methane windows. The observing geometry and our data processing (the methodology and its limitations) will be explained, followed by a discussion of the main characteristics of these images. These reproduce a portion of Ontario Lacus, supposedly filled with liquid hydrocarbons. Only part of it is visible on Titan's sunlit side. These images also show what appears to be a "beach", brighter then the lake's core but also brighter then the surrounding area of the lake. The morphology and composition of this beach is investigated and possible scenarios for its formation are explored. This yield constrains to geomorphologic models of Titan's surface.

ABSTRACT The existence of oceans or lakes of liquid hydrocarbons on Titan's surface was p... more ABSTRACT The existence of oceans or lakes of liquid hydrocarbons on Titan's surface was predicted more than 20 years ago. These would serve as a source of atmospheric methane and would also contain the end products of the photochemical reactions occurring high in the atmosphere. Although no oceans were ever found, lake-like features poleward of 70°N were first detected by the radar instrument onboard Cassini on July 2006. Before that, Cassini Imaging Science Subsystem (ISS) images of the south pole from June 2005 revealed an intriguing lake-like dark feature named Ontario Lacus. Recently an interesting and important result has been published about the identification of liquid ethane contained within Ontario Lacus (Brown et al. 2008). The authors analysed a near-infrared Visual and Infrared Mapping Spectrometer (VIMS) observation of the Ontario Lacus performed the 2007 December 4, during the T38 flyby. Their result needs nevertheless to be confirmed and improved using a more detailed methodology. Here we report on the analysis of this observation using a radiative transfer model (the libRadtran package) to simulate the atmospheric contribution. LibRadtran is a library of tools developed for radiative transfer calculations in the Earth's atmosphere, but adapted here to Titan's atmospheric conditions. Extinction sources were calculated for atmospheric methane and aerosols as a function of altitude and wavelength. Using the DISORT solver we were able to invert the surface spectrum of the lake interior and of an adjacent, non-lake region, in the near-infrared methane windows. The surface spectra were then compared with spectra of different ices and liquid hydrocarbons, yielding constraints on the possible constituents of Titan's lakes and their adjacent areas. Reference: Brown, R. et al. 2008. The identification of liquid ethane in Titan's Ontario Lacus, Nature 454, 607-610.

The electromagnetic coupling between the Galilean satellites at Jupiter and the planetary ionosph... more The electromagnetic coupling between the Galilean satellites at Jupiter and the planetary ionosphere generates an auroral footprint, whose ultimate source is the relative velocity between the moons and the corotating magnetospheric plasma. The footprint can be detected in the infrared L band (3.3-3.6 microns) by the Jovian InfraRed Auroral Mapper (JIRAM) onboard the Juno spacecraft, which can observe the footprint position with high precision. Here, we report the JIRAM data acquired since August 27th 2016 until May 23rd 2022, corresponding to the first 42 orbits of Juno. The dataset is used to compute the average position of the footprint tracks of Io, Europa and Ganymede. The result of the present analysis can help to test the reliability of magnetic field models, to calibrate ground-based observations and to highlight episodes of variability in the footprint positions, which in turn can point out specific conditions of the Jovian magnetospheric environment.

&lt;p&gt;The Jovian Infrared Auroral Mapper (JIRAM, a payload element of the NASA... more &lt;p&gt;The Jovian Infrared Auroral Mapper (JIRAM, a payload element of the NASA Juno mission to Jupiter) includes an infrared spectrometer covering the 2.0&amp;#8211;5.0 &amp;#956;m range. After reviewing the main results on the conditions of upper troposhere derived from the solar-dominated 2.0&amp;#8211;3.2 &amp;#956;m spectral range and presented in Grassi et al. 2021, we focus our discussion on open modeling issues and recent attempts to study these altitudes from data in the thermal-dominated 4.0-5.0 &amp;#956;m spectral range. We present also the results of an automatic classification of data performed on the basis of the HDBSCAN algorithm (McInnes et al. 2017). We show that similar spatial patterns are obtained either considering the coefficents of a PCA performed directly on spectra or on the physical parameters (clouds altitude, haze thickness) retrieved by the algorithm adopted in Grassi et al. 2021.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;Grassi et al. 2021 &amp;#160; d&lt;span&gt;oi:&lt;/span&gt;10.1093/mnras/stab740&lt;/p&gt;&lt;p&gt;McInnes et al. 2017 &amp;#160; d&lt;span&gt;oi:10.21105/joss.00205&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

A simple Radiative Transfer model has been developed for the Saturn's atmosphere and applied to t... more A simple Radiative Transfer model has been developed for the Saturn's atmosphere and applied to the VIMS images data. VIMS (Visible Infrared Mapping Spectrometer) is one of the instruments on board the Cassini spacecraft, orbiting the ringed planet since July 2004, still sending data to the Earth. VIMS is an image spectrometer able to show simultaneously the scene and spectral information of the target under observation, covering the visible and near infrared part of the electromagnetic spectrum. In order to test the model, we simulated the infrared radiance spectra inside a hot spot that, for its particular dynamical structure, is characterized by low optical depths. This cloudless condition is in contrast with the surrounding atmosphere, where the contribution of aerosols affects the signal. The results show the existance of different cloud layers in the surrounding atmosphere in order to fit the data. The near-infrared part (1.0-3.5 microns) of the VIMS spectra is very sensitive to the aerosols vertical distribution in the upper troposphere and lower stratosphere. Inversion techniques have been optimized and applied to these data, showing a three-layers stratification of scatterers: a lower-stratospheric layer located just above the tropopause (pressure levels of 60-100 mbar), a stable upper-tropospheric layer at pressure levels between 400-600 mbar, and a thicker cloud layer whose top lays just below the 1 bar level. Regional and spectral variation of these distribution are investigated.

ABSTRACT Vertical profiles of hydrogen cyanide (HCN) have been retrieved from Cassini/VIMS limb o... more ABSTRACT Vertical profiles of hydrogen cyanide (HCN) have been retrieved from Cassini/VIMS limb observations in the region from 600 to 1100 km of the Titan's atmosphere by analyzing the 3 μm emission. HCN concentrations show a very good correlation with solar zenith angles, for different latitudes and local times. This would indicate that HCN is in (or close to) photochemical equilibrium in the sounded region.

ABSTRACT Observations of Titan atmosphere made with the VIMS instrument on board the Cassini sate... more ABSTRACT Observations of Titan atmosphere made with the VIMS instrument on board the Cassini satellite show a strong limb emission around 3.3 μm at high atmospheric altitudes (above 700 km). This emission exhibits the spectral signatures of the strong CH4 bands. A detailed analysis of the spectra reveals an additional strong emission centered at 3.28 μm and peaking at about 950 km. Here we present an analysis of this residual spectra and show that it attributed to emission from heavy aromatic hydrocarbon compounds.

ABSTRACT In this work, selected regions of the giant vortex observed at Saturn since January 2011... more ABSTRACT In this work, selected regions of the giant vortex observed at Saturn since January 2011, have been investigated by analyzing the observations from the visual channel of the Visual and Infrared Mapping Spectrometer (VIMS-V) on board the Cassini spacecraft. Previously, a forward radiative transfer model has been developed, based on the LibRadtran code [13], adapted to the atmosphere of Saturn. Then an inverse code, based on the optimal estimation technique [14], has been implemented to retrieve the microphysical and geometrical properties of the clouds. Best fits of the radiance spectra relative to the vortex are produced and then the cloud top pressures are estimated. Data retrieved on a time lapse of months allow to investigate the temporal variation of the vortex's cloud properties.

Atmospheric Environment (1967), 1986

Abstract The latent heat flux has been determined during a fog situation by using a method based ... more Abstract The latent heat flux has been determined during a fog situation by using a method based on the surface heat balance equation and a parameterization of the sensible heat flux. The computed values of the latent heat flux show that it is connected with changes in fog density.

A simple study of the Saturn's clouds vertical profile is here presented using VIMS images. V... more A simple study of the Saturn's clouds vertical profile is here presented using VIMS images. VIMS (Visible Infrared Mapping Spectrometer), one of the instruments on board the Cassini spacecraft orbiting around the ringed planet since July 2004, is an image spectrometer able to show simultaneously a scene with the relative spectral information of the target under observation, covering the visible

During the first two years of the Cassini&amp;amp;amp;amp;amp;amp;amp;amp;#39;s nominal m... more During the first two years of the Cassini&amp;amp;amp;amp;amp;amp;amp;amp;#39;s nominal mission, VIMS (Visual and Infrared Mapping Spectrometer) has explored the whole system of Saturnian icy satellites. Here we report a comparative analysis of more than 600 full-disk observations obtained from July 2004 to nowadays for 15 regular and minor satellites: Atlas, Prometheus, Pandora, Janus, Epimetheus, Mimas, Enceladus, Tethys, Telesto, Calypso, Dione,

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2019

The instrument JIRAM (Jovian Infrared Auroral Mapper), on board the NASA spacecraft Juno, is both... more The instrument JIRAM (Jovian Infrared Auroral Mapper), on board the NASA spacecraft Juno, is both an imager and a spectrometer. Two distinct detectors are used for imaging and spectroscopy. The imager acquires Jupiter images in two bands, one of which (L band, 3.3–3.6 μm) is devoted to monitor the H 3 + emission. The spectrometer covers the spectral region from 2 to 5 μm (average spectral resolution 9 nm) with a 256 pixels slit that can observe the same scene of the L band imager with some delay. JIRAM scientific goals are the exploration of the Jovian aurorae and the planet's atmospheric structure, dynamics and composition. Starting early July 2016 Juno is orbiting around Jupiter. Since then, JIRAM has provided an unprecedented amount of measurements, monitoring both Jupiter's atmosphere and aurorae. In particular, the camera has monitored Jupiter's poles with very high spatial resolution, providing new insights in both its aurorae and the polar dynamic. The main findin...

EGU General Assembly Conference Abstracts, Apr 1, 2017

AGU Fall Meeting Abstracts, Dec 1, 2008

EGUGA, Apr 1, 2017

Titan Aeronomy and Climate, Jun 1, 2016

Atmospheric Environment (1967), 1986

Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, 2019

EGU General Assembly Conference Abstracts, Apr 1, 2017