1,901 research outputs found
Geomagnetic control of the spectrum of traveling ionospheric disturbances based on data from a global GPS network
In this paper an attempt is made to verify the hypothesis on the role of
geomagnetic disturbances as a factor determining the intensity of traveling
ionospheric disturbances (TIDs). To improve the statistical validity of the
data, we have used the based on the new GLOBDET technology method involving a
global spatial averaging of disturbance spectra of the total electron content
(TEC). To characterize the TID intensity quantitatively, we suggest that a new
global index of the degree of disturbance should be used, which is equal to the
mean value of the rms variations in TEC within the selected range of spectral
periods (of 20-60 min in the present case). It was found that power spectra of
daytime TEC variations in the range of 20-60 min periods under quiet conditions
have a power-law form, with the slope index k = -2.5. With an increase of the
level of magnetic disturbance, there is an increase in total intensity of TIDs,
with a concurrent kink of the spectrum caused by an increase in oscillation
intensity in the range of 20-60 min. It was found that an increase in the level
of geomagnetic activity is accompanied by an increase in total intensity of
TEC; however, it correlates not with the absolute level of Dst, but with the
value of the time derivative of Dst (a maximum correlation coefficient reaches
-0.94). The delay of the TID response of the order of 2 hours is consistent
with the view that TIDs are generated in auroral regions, and propagate
equatorward with the velocity of about 300-400 m/s.Comment: LaTeX2.09, 16 pages, 5 figures, 1 table, egs.cls, egs.bst (the style
files
Solar-Terrestrial Science Strategy Workshop
The conclusions and recommendations reached at the Solar Terrestrial Science Strategy Workshop are summarized. The charter given to this diverse group was: (1) to establish the level of scientific understanding to be accomplished with the completion of the current and near term worldwide programs; (2) identify the significant scientific questions to be answered by future solar terrestrial programs, and the programs required to answer these questions; and (3) map out a program strategy, taking into consideration currently perceived space capabilities and constraints, to accomplish the identified program
Handbook for MAP, volume 32. Part 1: MAP summary. Part 2: MAPSC minutes, reading, August 1989. MAP summaries from nations. Part 3: MAP data catalogue
Extended abstracts from the fourth workshop on the technical and scientific aspects of mesosphere stratosphere troposphere (MST) radar are presented. Individual sessions addressed the following topics: meteorological applications of MST and ST radars, networks, and campaigns; the dynamics of the equatorial middle atmosphere; interpretation of radar returns from clear air; techniques for studying gravity waves and turbulence, intercomparison and calibration of wind and wave measurements at various frequencies; progress in existing and planned MST and ST radars; hardware design for MST and ST radars and boundary layer/lower troposphere profilers; signal processing; and data management
Ionization effects due to solar flare on terrestrial ionosphere
Sudden frequency deviation ionospheric disturbances related to the flares of May 18 and 19, 1973 were observed from the NASA/MSFC high frequency Doppler sounder array system in Huntsville, Alabama. The results are compared with those observed at Table Mountain near Boulder, Colorado and at the University of Hawaii
Environmental analysis of the chemical release module
The environmental analysis of the Chemical Release Module (a free flying spacecraft deployed from the space shuttle to perform chemical release experiments) is reviewed. Considerations of possible effects of the injectants on human health, ionosphere, weather, ground based optical astronomical observations, and satellite operations are included. It is concluded that no deleterious environmental effects of widespread or long lasting nature are anticipated from chemical releases in the upper atmosphere of the type indicated for the program
The plasma dynamics of hypersonic spacecraft: Applications of laboratory simulations and active in situ experiments
Attempts to gain an understanding of spacecraft plasma dynamics via experimental investigation of the interaction between artificially synthesized, collisionless, flowing plasmas and laboratory test bodies date back to the early 1960's. In the past 25 years, a number of researchers have succeeded in simulating certain limited aspects of the complex spacecraft-space plasma interaction reasonably well. Theoretical treatments have also provided limited models of the phenomena. Several active experiments were recently conducted from the space shuttle that specifically attempted to observe the Orbiter-ionospheric interaction. These experiments have contributed greatly to an appreciation for the complexity of spacecraft-space plasma interaction but, so far, have answered few questions. Therefore, even though the plasma dynamics of hypersonic spacecraft is fundamental to space technology, it remains largely an open issue. A brief overview is provided of the primary results from previous ground-based experimental investigations and the preliminary results of investigations conducted on the STS-3 and Spacelab 2 missions. In addition, several, as yet unexplained, aspects of the spacecraft-space plasma interaction are suggested for future research
Short term Variability of the Sun Earth System: An Overview of Progress Made during the CAWSES II Period
This paper presents an overview of results obtained during the CAWSES II
period on the short term variability of the Sun and how it affects the near
Earth space environment. CAWSES II was planned to examine the behavior of the
solar terrestrial system as the solar activity climbed to its maximum phase in
solar cycle 24. After a deep minimum following cycle 23, the Sun climbed to a
very weak maximum in terms of the sunspot number in cycle 24 (MiniMax24), so
many of the results presented here refer to this weak activity in comparison
with cycle 23. The short term variability that has immediate consequence to
Earth and geospace manifests as solar eruptions from closed field regions and
high speed streams from coronal holes. Both electromagnetic (flares) and mass
emissions (coronal mass ejections, CMEs) are involved in solar eruptions, while
coronal holes result in high speed streams that collide with slow wind forming
the so called corotating interaction regions (CIRs). Fast CMEs affect Earth via
leading shocks accelerating energetic particles and creating large geomagnetic
storms. CIRs and their trailing high speed streams (HSSs), on the other hand,
are responsible for recurrent small geomagnetic storms and extended (days) of
auroral zone activity, respectively. The latter lead to the acceleration of
relativistic magnetospheric killer electrons. One of the major consequences of
the weak solar activity is the altered physical state of the heliosphere that
has serious implications for the shock-driving and storm causing properties of
CMEs. Finally, a discussion is presented on extreme space weather events
prompted by the 2012 July 23 super storm event that occurred on the backside of
the Sun. Many of these studies were enabled by the simultaneous availability of
remote-sensing and in situ observations from multiple vantage points with
respect to the Sun Earth line.Comment: 85 pages, 30 figures, 2 tables, Accepted for publication in Progress
in Earth and Planetary Science on April 13, 201
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