ISSN:0148-0227    

DOI:10.1029/94JA01974

年代:1994

数据来源: WILEY

摘要:

A personal perspective is given of the development of our understanding of the loss of electrons in the ionosphere, of the formation of the ionized regions, and of the collision processes pertaining to the nightglow.

ISSN:0148-0227    

DOI:10.1029/94JA00101

年代:1994

数据来源: WILEY

摘要:

Both the American Geophysical Union (AGU) and the International Union of Geodesy and Geophysics (IUGG) were established in 1919, to promote the study of physical problems in and above the Earth, for national and international managements. The initial internal structure within IUGG (especially for geomagnetism and space science dealt with in IAGA, the International Association of Geomagnetism and Aeronomy) owes very much to AGU's appropriate proposals. After the IGY (International Geophysical Year 1957‐58), it was necessary for both AGU and IAGA to modify their internal structures to cope with a rapid progress in space physics with technological development for in‐situ observations by spacecraft. A serious discussion was held in 1920's ‐ 30's about the possible existence of a non‐potential part in the geomagnetic field and its time‐variations in connection with the air‐Earth current. The curl‐freeness of the geomagnetic field cannot be experimentally proved insofar as the differential operation is simply substituted by spatial differences of the observed magnetic field values. It was shown that the archeo‐secular variation of the geomagnetic dipole axis in historic time could be known also from a comparison of the records of ancient auroras preserved in the Oriental and Occidental places. In the history of magnetic storm studies, there was a severe debate between two groups of workers, the Scandinavian school (the importance of field‐aligned currents at high latitudes was emphasized, based on an early study of Birkeland, and later advocated by Alfvén and his colleagues) and the British school (headed by Chapman, attributing the ground magnetic effect rather to horizontal currents in the ionosphere). However, their severe debate was rather meaningless without in‐situ magnetic field measurements above the ionosphere. It is emphasized in this paper that we have to pay more attention to the change in the magnetic declination, in particular its seasonal dependence. The declination change at the storm sudden commencements shows specific local‐time and seasonal dependences, reflecting the solar‐wind interaction with the geomagnetic field. The seasonal dependence of the daily declination change on quiet days enables us to infer transequatorial field‐aligned currents in the magnetosphere at low and middle latitudes. A review is given also for the significant contribution of MAGSAT to the study of three‐dimensional electric currents in the near‐Earth environmental space. There are five Appendices to supplement the above subjects, i.e. on the origin of the words “geomagnetism” and “aeronomy”; the transition from IATME to IAGA; Birkeland's last days in Tokyo; and Harang discontinuity; and the VII General Assembly of IUGG

ISSN:0148-0227    

DOI:10.1029/94JA00102

年代:1994

数据来源: WILEY

摘要:

The 75th Anniversary of the AGU marks the discovery of the basic features of solar control of the ionosphere. A quarter of a century later our understanding of ionospheric physics was revolutionized by the early rocket era of upper air research that brought the discoveries of solar X ray and XUV radiation.

ISSN:0148-0227    

DOI:10.1029/94JA00106

年代:1994

数据来源: WILEY

摘要:

Space science began with the indirect phase where the activity in space was inferred from such terrestrial phenomena as geomagnetic storms, ionospheric variations, and fluctuations in the cosmic ray intensity. The direct phase was initiated with spaceflight placing instruments directly in space and permitting the direct observation of UV and X rays, as well as precision observations of solar luminosity variations. The evidence from these many direct studies, together with the historical record of terrestrial conditions, shows that the variations of the luminosity of the Sun affect the terrestrial atmosphere at all levels, with devastating changes in climate tracking the major changes in the activity level and luminosity of the Sun. The quantification and understanding of this vital connection should be the first priority of space science and geophysics, from oceans and atmosphere through the ionosphere, magnetosphere, and all the way to the convective zone of the Sun. It becomes the vital phase of space science, focused on the basic science of the changing habitability of Earth.

ISSN:0148-0227    

DOI:10.1029/94JA00103

年代:1994

数据来源: WILEY

摘要:

This contribution to the 75th Anniversary of the AGU is an informal and anecdotal account of the author's research interests and activities as they relate to cosmic ray investigations involving geophysics and experiments in space during the period 1947 to the 1960's. It begins with the discovery of the cosmic ray nucleonic component geomagnetic latitude effect and its application to establishing the interplanetary origin of the cosmic ray intensityvs. time variations and the concept of solar modulation. The development of the cosmic ray neutron monitor contributed not only to an understanding of interplanetary electrodynamical processes, but also to the experimental evidence for a heliosphere. The author discusses the introduction of cosmic ray physics into the International Geophysical Year (1957‐58) and the post‐IGY initiation at the University of Chicago of research based on experiments carried in spacecr

ISSN:0148-0227    

DOI:10.1029/94JA00107

年代:1994

数据来源: WILEY

摘要:

This “personal history” covers the period from about 1954 to the present, beginning with the time that I witnessed the start of the U.S. space program triggered by the launch of Sputnik, and includes my experience as Project Scientist for Pioneers 1, 2, 5, and Explorer 6, my service at NASA headquarters as Chief of Lunar and Planetary Sciences, followed by my role in organization of the NASA Ames Space Sciences Division, and in 1973, I formed the Dept. of Planetary Sciences at the University of Ariz

ISSN:0148-0227    

DOI:10.1029/94JA00108

年代:1994

数据来源: WILEY

摘要:

This account displays continuing development flowing from my Ph.D. project. MHD was sufficient for the discovery of reconnection and observations on spacecraft provided supporting evidence. If the rate of reconnection is to be predicted, more sophisticated plasma theory is needed. Extensive analysis of wave‐particle interactions is described. They were thought to be important in the neutral sheet, but another mechanism, electron viscosity, is described and no conclusion is reache

ISSN:0148-0227    

DOI:10.1029/94JA00105

年代:1994

数据来源: WILEY

摘要:

Some important events leading to the emergence of our present understanding of some space physics phenomena are recounted from the author's personal perspective.

ISSN:0148-0227    

DOI:10.1029/94JA00104

年代:1994

数据来源: WILEY

摘要:

Coronal mass ejections (CMEs) have been identified as a trigger for large geomagnetic storms. A clever idea to provide advance warning of a high‐speed CME approaching the Earth was recently proposed by Hsieh et al. (1992): ejected solar matter decelerates on its way from the Sun to Earth, energetic neutral atoms (ENAs) are formed in the CME plasma due to recombination, ENAs pass the decelerating CME plasma and arrive first at the Earth. We evaluate the idea to use ENAs for advance detection of the high‐speed Earth‐approaching CMEs and consider the processes involved. Charge exchange between solar wind ions and interplanetary neutral atoms contribute effectively to ENA production. Characteristics of neutral gas within Earth's orbit are updated for both neutral atoms of interstellar origin and from outgassing from interplanetary dust. Computer simulation of CME‐produced ENAs shows that the total flux of CME‐produced ENAs is slightly smaller than the intensity of the quiescent neutral solar wind (NSW) while significantly higher ENA energies make them easily distinguishable from NSW atoms. Arrival of the CME‐produced ENAs is expected 3‐4 hours before the start of a large geomagnetic storm, which provides a basis for advance storm warning and prediction of storm magnitude. The progress in development of ENA measurement technique suggests that both the quiescent NSW and CME‐produced ENAs can be re

ISSN:0148-0227    

DOI:10.1029/94JA01571

年代:1994

数据来源: WILEY