Showing papers on "Space weather published in 1988"

Introduction to the space environment

Abstract: This reprint of the second edition includes a new chapter--Space Weather Services. The purpose of this chapter is to define space weather nowcast and forecast requirements for the commercial space weather community. A nowcast is a short-range forecast usually on the order of 1 or 2 hours lead tie. This is the only textbook on the space environment written for the novice which covers all the major topics in space physics. The reader is expected to have a solid background in introductory physics; therefore, this edition is most useful as a text for senior-year college or first-year graduate students. Topics include plasma physics, solar physics, solar wind processes, geomagnetism, magnetospheric physics, physics of the neutral atmosphere, ionospheric physics, ionospheric variability, radiowave propagation in the ionosphere, and space environmental effects on spacecraft.

“Space weather forecast”: Prediction of relativistic electron intensity at synchronous orbit

Abstract: Long-term variations in high-energy (greater than 2 MeV) electron flux at synchronous orbit are examined to reveal their close relationship to geomagnetic activity. The electron flux diminishes rapidly in association with an enhancement of geomagnetic activity (storm) and then increases. The flux becomes higher than the pre-storm level and its peak occurs approximately 4–5 days after the enhancement of geomagnetic activity. A linear prediction filter is designed for daily sums of Kp as input data and corresponding daily averages of the electron flux (Log value) as output data. The data are those taken in 1984–1985. This filter can successfully reproduce the electron flux behavior observed not only in 1984–1985 but also in 1978–1981.

Solar, Geomagnetic and Auroral Variations Observed in Historical Data

Abstract: The use of historical data sets to investigate solar and solar-terrestrial variability was demonstrated dramatically by J.A. Eddy when he described the Maunder Minimum. The historical record can also be examined for evidence of less dramatic changes such as those associated with the 88 year cycle in auroral activity. Power spectral analyses of historical auroral data from 450 AD to 1450 AD show a strong line at 88.4 ± 0.7 years verifying the existence of the Gleissberg cycle in auroras during that 1,000 years. The relation of these results to observations recorded since 1700 will be discussed. Emphasis will be placed on developing a description of the changes in solar and solar terrestrial phenomena during the 1900 and 1815 minima in sunspot cycle amplitude and auroral and geomagnetic disturbance levels.

Soho and Cluster - The scientific instruments

Abstract: The mission goals and instrumentation of the Soho and cluster spacecraft to be launched in 1995 as part of the international Solar-Terrestrial Science Program are discussed. Instruments such as normal-incidence, grazing-incidence, and EUV coronal spectrometers aboard the Soho spacecraft will study the origin of the solar wind and the physical properties of the solar atmosphere. The four Cluster spacecraft will measure electric and magnetic fields, plasmas, and energetic particles using instruments including a wide-band receiver system, a relaxation sounder, and a search coil magnetometer.

Max '91: flare research at the next solar maximum

Abstract: To address the central scientific questions surrounding solar flares, coordinated observations of electromagnetic radiation and energetic particles must be made from spacecraft, balloons, rockets, and ground-based observatories. A program to enhance capabilities in these areas in preparation for the next solar maximum in 1991 is recommended. The major scientific issues are described, and required observations and coordination of observations and analyses are detailed. A program plan and conceptual budgets are provided.

Correlations between solar activity and operationally determined satellite drag variation parameters

Abstract: Operational orbit determination of the Earth Radiation Budget Satellite (ERBS) and the Solar Maximum Mission (SMM) spacecraft using the Goddard Trajectory Determination System (GTDS) in the Flight Dynamics Facility (FDF) of the Goddard Space Flight Center (GSFC) has yielded an orbit solution data base of 3 years for ERBS and 8 years for SMM. One of the parameters in each data base is the drag variation parameter used in the GTDS atmospheric drag model; this parameter is solved routinely to accommodate the different atmospheric densities as they are encountered solution to solution. These two data bases of the drag variation parameter solutions are analyzed to evaluate correlations in the variations of the parameter with changes in the 10.7-cm wavelength solar flux, F10.7, and the geomagnetic index. The data for SMM span a wider range of solar flux values and show a stronger correlation. The data for ERBS, which is at a higher altitude and inclination than SMM, show a significant degree of scatter. For both satellites, the data indicate that changes in the drag variation parameter are more strongly correlated with the F10.7 solar flux than with the geomagnetic index. Correlations with the geomagnetic index are apparent only for severe geomagnetic storm conditions. Results from this analysis enhance the understanding of the drag model and the accommodation density variations in operational orbit determination support.

Solar proton event forecasts

Abstract: The United States operates a space weather service to provide information on space hazards including solar proton events to Federal government agencies and other users who operate systems that are affected by disturbances in the upper atmosphere and interplanetary environment. The observation and prediction of solar proton events has been continuous through solar cycle 21 (1976 to 1986), establishing a base of experience that can be used in providing similar support to space operations in the 1990's. The observations, indices, alerts, and forecasts used in the service are described. Also provided is a short summary of the experience obtained from making proton event predictions in solar cycle 21 including the years 1976 to 1986.