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11.
D.J. Michels N.R. Sheeley R.A. Howard M.J. Koomen R. Schwenn K.H. Mulhauser H. Rosenbauer 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(7):311-321
A small coronagraph has been placed in orbit to monitor the sun's outer corona from 2.5 to 10.0 solar radii, and five years of nearly continuous synoptic observations have now been completed. Rapid and sensitive image processing techniques have been developed to screen the data for transient phenomena, particularly coronal mass ejections (CMEs). About 50,000 coronal images have been examined, out of a five-year total of 68,000, and a standardized listing of more than 1,200 coronal transients for the period 1979–1982 has been prepared. These data have been analysed in the light of other available information, particularly on conditions in the interplanetary plasma. The dynamical characteristics of the active corona, as they are beginning to emerge from the data, are presented. We find that coronal mass ejections exercise significant influence on the interplanetary solar wind. They are the source of disturbances that are frequent and energetic, that tend to be somewhat focussed, that often reach shock intensity, and that propagate to large heliocentric distances, sometimes causing major geomagnetic storms. 相似文献
12.
R.A. Howard N.R. Sheeley M.J. Koomen D.J. Michels 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(7):307-310
The Solwind coronagraph on the P78-1 earth-orbiting satellite has been monitoring the Sun routinely at 10-minute intervals during the 5-year interval from April, 1979 to the present. In a statistical analysis of about 1000 mass ejections observed through the end of 1981, we find an average occurrence rate of 1.8 mass ejections per day. Histograms of speed, central latitude, angular span, brightness, and other parameters have been constructed, and properties such as shape classification have been tabulated. These characteristics are summarized for these years near sunspot maximum. The average speed and mass estimate are found to be similar to those found at the declining phase of the previous sunspot cycle. The angular span and central latitude distributions are quite different than seen during the declining phase, and are very dependent upon structural class. The fluctuations in the occurrence rate of CMEs does not seem to match the fluctuations in the sunspot number. There is a tendency for high speed CMEs to occur more frequently in 1981 than in 1980, and more frequently in 1980 than in 1979. 相似文献
13.
Howard E. McCurdy 《Space Policy》1994,10(4):277-289
Estimates of the cost of human space flight continue to generate controversy in the effort to set US space policy. Estimates vary widely, depending upon the position of the observer. This article identifies the real cost of major space flight programs and traces the heterofore unsuccessful efforts to cut the expense of space operations. 相似文献
14.
Howard A. Baker 《Space Policy》1990,6(4):332-340
This article examines the development of policy on space debris in the European Space Agency and the USA, comments on its regulatory effectiveness, and proposes further recommendations for consideration when developing future space debris policy. The author argues that the international community must work towards a policy which incorporates an environmental perspective, and discusses the principles which should inform such a perspective. 相似文献
15.
Physiologic and metabolic responses of wheat seedlings to elevated and super-elevated carbon dioxide
Lanfang H. Levine Hirokazu Kasahara Joachim Kopka Alexander Erban Ines Fehrl Fatma Kaplan Wei Zhao Ramon C. Littell Charles Guy Raymond Wheeler John Sager Aaron Mills Howard G. Levine 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The metabolic consequence of suboptimal (400 μmol mol−1 or ppm), near-optimal (1500 ppm) and supra-optimal (10,000 ppm) atmospheric carbon dioxide concentrations [CO2] was investigated in an attempt to reveal plausible underlying mechanisms for the differential physiological and developmental responses to increasing [CO2]. Both non-targeted and targeted metabolite profiling by GC–MS and LC–MS were employed to examine primary and secondary metabolites in wheat (Triticum aestivum, cv Yocoro rojo) continuously exposed to these [CO2] levels for 14, 21 and 28 days. Metabolite profile was altered by both [CO2] and physiological age. In general, plants grown under high [CO2] exhibited a metabolite profile characteristic of older plants under ambient CO2. Elevated [CO2] resulted in higher levels of phosphorylated sugar intermediates, though no clear trend in the content of reducing sugars was observed. Transient starch content was enhanced by increasing [CO2] to a much greater extent at 10,000 ppm CO2 than at 1500 ppm CO2. The percentage increase of starch content resulting from CO2 enrichment declined as plants develope. In contrast, elevated [CO2] promoted the accumulation of secondary metabolites (flavonoids) progressively to a greater extent as plants became mature. Elevated [CO2] to 1500 ppm induced a higher initial growth rate, while super-elevated [CO2] appeared to negate such initial growth promotion. However, after 4 weeks, there was no difference in vegetative growth between 1500 and 10,000 ppm CO2-grown plants, both elevated CO2 levels resulted in an overall 25% increase in biomass over the control plants. More interestingly, elevated atmospheric [CO2] reduced evapotranspiration rate (ET), but further increase to the supra-optimal level resulted in increased ET (a reversed trend), i.e. ET at 1500 ppm < ET at 10,000 ppm < ET at 400 ppm. The differential effect of elevated and super-elevated CO2 on plants was further reflected in the nitrogen dynamics. These results provide the potential metabolic basis for the differential productivity and stomatal function of plants grown under elevated and super-elevated CO2 levels. 相似文献
16.
Margarita Karovska Brian E. Wood John W. Cook Russell A. Howard Guenter E. Brueckner 《Space Science Reviews》1999,87(1-2):219-222
We present the results from a study of the dynamical properties of polar jets in the Sun's polar regions using LASCO C2 coronagraph
and EIT observations. In the simplest impulsive acceleration scenarios for jets, gravity is expected to be the dominant force
on the jet following the initial acceleration, especially in the Sun's polar regions where the open magnetic fields should
not significantly impede the jet's motion. Our analysis shows that although at low heights the kinematics of the jets could
be consistent with a gravitational deceleration of the ejected plasma, at higher heights their motions may simply follow the
ambient solar wind outflow. If so, the polar jets can be used as tracers of the solar wind in coronal holes.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
17.
N. Gopalswamy A. Lara P.K. Manoharan R.A. Howard 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2289-2294
We extend the empirical coronal mass ejection (CME) arrival model of Gopalswamy et al. [Gopalswamy, N. et al. Predicting the 1-AU arrival times of coronal mass ejections, J. Geophys. Res. 106, 29207, 2001] to predict the 1-AU arrival of interplanetary (IP) shocks. A set of 29 IP shocks and the associated magnetic clouds observed by the Wind spacecraft are used for this study. The primary input to this empirical shock arrival model is the initial speed of white-light CMEs obtained using coronagraphs. We use the gas dynamic piston–shock relationship to derive the ESA model which provides a simple means of obtaining the 1-AU speed and arrival times of interplanetary shocks using CME speeds. 相似文献
18.
N. Gopalswamy S. Yashiro M.L. Kaiser R.A. Howard 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,32(12):2613-2618
Two successive solar energetic particle (SEP) events associated with fast and wide coronal mass ejections (CMEs) on 2001 April 14 and 15 are compared. The weak SEP event of April 14 associated with an 830 km/s CME and an M1.0 flare was the largest impulsive event of cycle 23. The April 15 event, the largest ground level event of cycle 23, was three orders of magnitude more intense than the April 14th event and was associated with a faster CME (1200 km/s) and an X14.4 flare. We compiled and compared all the activities (flares, CMEs, interplanetary conditions and radio bursts) associated with the two SEP events to understand the intensity difference between them. Different coronal and interplanetary environments of the two events (presence of preceding CME and seed particles ahead of the April 15 event) may explain the intensity difference. 相似文献
19.
The causes and origins of Coronal Mass Ejections (CMEs) remain among the outstanding questions in Space Physics. The observations of CMEs by the LASCO coronagraphs on SOHO suggest that there are two distinct types of CMEs. The two types of events can be most easily distinguished by examining height-time plots. The Type A (Acceleration) events produce curved plots that often indicate a constant acceleration. These events are usually associated with pre-existing helmet-streamers, and are often associated with prominence eruptions or filament disappearance. The Type C (Constant speed) events show a constant speed. These events are usually brighter, larger, and faster than Type A events and may be associated with X-ray flares. While the two types of events can be distinguished in other ways, the height-time plots are a simple and unambiguous way to make this identification. 相似文献
20.
Edward J. Rhodes Alessandro Cacciani Steven Tomczyk Roger K. Ulrich Jacques Blamont Robert F. Howard Philip Dumont Edward J. Smith 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,4(8):103-112
A compact Dopplergraph/magnetograph placed in a continuous solar-viewing orbit will allow us to make major advancements in our understanding of solar internal structure and dynamics. An international program is currently being conducted at JPL and Mt. Wilson to develop such an instrument. By combining a unique magneto-optical resonance filter with CID and CCD cameras we have been able to obtain full- and partial-disk Dopplergrams and magnetograms. Time series of the velocity images are converted into k-ω power spectra which show clear- the solar nonradial p-mode oscillations. Magnetograms suitable for studying the long-term evolution of solar active regions have also been obtained with this instrument. A flight instrument based on this concept is being studied for possible inclusion in the SOHO mission. 相似文献