Search results for "Geophysic"

Anomalies in radiation-collisional kinetics of Rydberg atoms induced by the effects of dynamical chaos and the double Stark resonance

2013

Radiative and collisional constants of excited atoms contain the matrix elements of the dipole transitions and when they are blocked one can expect occurring a number of interesting phenomena in radiation-collisional kinetics. In recent astrophysical studies of IR emission spectra it was revealed a gap in the radiation emitted by Rydberg atoms ($RA$) with values of the principal quantum number of $n\approx10$. Under the presence of external electric fields a rearrangement of $RA$ emission spectra is possible to associate with manifestations of the Stark effect. The threshold for electric field ionization of $RA$ is $E\approx3\cdot10^{4}$ V/cm for states with $n>10$. This means that the emis…

Multi-phase interstellar clouds in the Vela SNR resolved with XMM-Newton

2005

XMM-Newton spatial/spectral resolution and high effective area allow to deepen our knowledge about the shocks in Supernova Remnants and their interaction with the interstellar medium. We present the analysis of an EPIC observation of the northern rim of the Vela SNR and we compare the X-ray and optical morphology of the emission. We derive a description of the internal structure of the shocked interstellar clouds, arguing that the transmitted shock model is compatible with our data. We also suggest that thermal conduction between clouds and inter-cloud medium is very efficient and produces the evaporation of the clouds in the interstellar medium. � 2005 COSPAR. Published by Elsevier Ltd. Al…

A coupled map as a model of the dynamics of the magnetotail current sheet

2001

Abstract A magnetic field model of the magnetotail current sheet in the form of a coupled-map lattice (CML) is presented. It is continuously driven (“running”) and based on the MHD diffusion equation. Solar wind vBS data (solar wind speed multiplied by the southward component of IMF) are used for driving the model, and it is shown to exhibit perturbations (avalanches) with power-law scalings in their distributions of duration and size. Such distributions may indicate self-organized critical (SOC) behavior. Furthermore, it is shown that the power spectra of the model outputs are of bicolor power-law form with different slopes for high and low frequencies. Although the “running” model gives p…

Production altitude and time delays of the terrestrial gamma flashes: Revisiting the Burst and Transient Source Experiment spectra

2008

[1] On the basis of the RHESSI results it has been suggested that terrestrial gamma flashes (TGFs) are produced at very low altitudes. On the other hand some of the Burst and Transient Source Experiment (BATSE) spectra show unabsorbed fluxes of X rays in the 25–50 keV energy range, indicating a higher production altitude. To investigate this, we have developed a Monte Carlo code for X-ray propagation through the atmosphere. The most important features seen in the modeled spectra are (1) a low-energy cutoff which moves to lower energies as TGFs are produced at higher altitudes, (2) a high-energy cutoff which moves to lower energies as TGFs are observed at larger zenith angles, and (3) time d…

Collocated measurements of boundary layer cloud microphysical and radiative properties: A feasibility study

2010

[1] First data from collocated, helicopter-based measurements of boundary layer cloud microphysical properties (effective droplet radius Reff, droplet number concentration N) and spectral radiative quantities (cloud optical thickness τ, cloud top albedo ρ, reflectivity ) are presented. The in situ measurements of the microphysical cloud properties were collected by the Airborne Cloud Turbulence Observation System (ACTOS) attached to a helicopter by a 145 m long rope. Cloud spectral reflectivity was derived from radiances measured by grating spectrometers combined with downward looking optical inlets installed underneath the helicopter. Correlations between cloud microphysics and reflected r…

Reply to comment by R. Grard et al. on “An analysis of VLF electric field spectra measured in Titan's atmosphere by the Huygens probe”

2011

Properties of the isolated neutron star RX J185635-3754

2004

Abstract Despite improved observational capabilities, the surface properties of neutron stars remain uncertain. In principle, multiwavelength spectra can reveal their compositions and angular diameters and constrain the interior equation of state. The Chandra LETG spectrum of the brightest isolated neutron star is a featureless continuum. The X-ray blackbody fit underpredicts the observed optical fluxes, but the spectral energy distribution can be fit with a two blackbody model. No pulsations are seen. We discuss model atmosphere fits. We conclude there is no need to invoke exotic physics: RX J185635-3754 is likely a 0.5 × 10 6 years old pulsar.

Coronal mass ejections in the heliosphere

2010

With the advent of the NASA STEREO mission, we are in a position to perform unique investigations of the evolution of coronal mass ejections (CMEs) as they propagate through the heliosphere, and thus can investigate the relationship between CMEs and their interplanetary counterparts, so-called interplanetary CMEs (ICMEs). ICME studies have been principally limited to single-point, in-situ observations; interpretation of the in-situ characteristics of ICMEs has been used to derive a range of ICME properties which we can now confirm or refute using the STEREO imaging data. This paper is a review of early STEREO CME observations and how they relate to our currently understanding of ICMEs based…

Simultaneous Observations of EIP, TGF, Elve, and Optical Lightning

2021

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

Spectral Analysis of Individual Terrestrial Gamma-ray Flashes Detected by ASIM

2021

The Atmosphere-Space Interactions Monitor (ASIM) is the first instrument in space specifically designed to observe terrestrial gamma-ray flashes (TGFs). TGFs are high energy photons associated with lightning flashes and we perform the spectral analysis of 17 TGFs detected by ASIM. The TGF sample is carefully selected by rigorous selection criteria to keep a clean sample suitable for spectral analysis, that is, suitable count statistics, low instrumental effects, and reliable source location. Monte Carlo modeling of individual TGFs has been compared to the observed energy spectra to study the possible source altitudes and beaming geometries. A careful model of the instrumental effects has be…