796 research outputs found
Traveling wave packets of total electron content disturbances as deduced from global GPS network data
We identified a new class of mid-latitude medium-scale traveling ionospheric
disturbances (MS TIDs), viz. traveling wave packets (TWPs) of total electron
content (TEC) disturbances. For the first time, the morphology of TWPs is
presented for 105 days. Using the technique of GPS interferometry of TIDs we
carried out a detailed analysis of the spatial-temporal properties of TWPs by
considering an example of the most conspicuous manifestation of TWPs on October
18, 2001 over California, USA. The velocity and direction of TWPs correspond to
those of mid-latitude MS TIDs obtained previously from analyzing the phase
characteristics of HF radio signals as well as signals from geostationary
satellites and discrete cosmic radio sources.Comment: LaTeX2.09, 28 pages, 9 figure
Ionospheric effects of the solar flares of September 23, 1998 and July 29, 1999 as deduced from global GPS network data
This paper presents data from first GPS measurements of global response of
the ionosphere to solar flares of September 23, 1998 and July 29, 1999. The
analysis used novel technology of a global detection of ionospheric effects
from solar flares (GLOBDET) as developed by one of the authors (Afraimovich E.
L.). The essence of the method is that use is made of appropriate filtering and
a coherent processing of variations in total electron content (TEC) in the
ionosphere which is determined from GPS data, simultaneously for the entire set
of visible (over a given time interval) GPS satellites at all stations used in
the analysis. It was found that fluctuations of TEC, obtained by removing the
linear trend of TEC with a time window of about 5 min, are coherent for all
stations and beams to the GPS satellites on the dayside of the Earth. The time
profile of TEC responses is similar to the time behavior of hard X-ray emission
variations during flares in the energy range 25-35 keV if the relaxation time
of electron density disturbances in the ionosphere of order 50-100 s is
introduced. No such effect on the nightside of the Earth has been detected yet.Comment: EmTeX-386, 13 pages, 5 figure
The use of GPS-arrays in detecting shock-acoustic waves generated during rocket launchings
This paper is concerned with the form and dynamics of shock-acoustic waves
(SAW) generated during rocket launchings. We have developed a method for
determining SAW parameters (including angular characteristics of the wave
vector, and the SAW phase velocity, as well as the direction towards the
source) using GPS-arrays whose elements can be chosen out of a large set of
GPS-stations of the global GPS network. The application of the method is
illustrated by a case study of ionospheric effects from launchings of launch
vehicles (LV) Proton and Space Shuttle from space-launch complexes Baikonur and
Kennedy Space Center (KSC) in 1998 and 1999 (a total of five launchings). The
study revealed that, in spite of a difference of LV characteristics, the
ionospheric response for all launchings had the character of an N - wave
corresponding to the form of a shock wave, regardless of the disturbance source
(rocket launchings, industrial explosions). The SAW period T is 270--360 s, and
the amplitude exceeds the standard deviation of TEC background fluctuations in
this range of periods under quiet and moderate geomagnetic conditions by
factors of 2 to 5 as a minimum. The angle of elevation of the SAW wave vector
varies from 30 degree to 60 degree, and the SAW phase velocity (900-1200 m/s)
approaches the sound velocity at heights of the ionospheric F-region maximum.Comment: EmTeX-386, 23 pages, 6 figure
Directional complexity and entropy for lift mappings
We introduce and study the notion of a directional complexity and entropy for
maps of degree 1 on the circle. For piecewise affine Markov maps we use
symbolic dynamics to relate this complexity to the symbolic complexity. We
apply a combinatorial machinery to obtain exact formulas for the directional
entropy, to find the maximal directional entropy, and to show that it equals
the topological entropy of the map. Keywords: Rotation interval, Space-time
window, Directional complexity, Directional entropy;Comment: 19p. 3 fig, Discrete and Continuous Dynamical Systems-B (Vol. 20, No.
10) December 201
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