Donald V. Helmberger the Mentor

Don is certainly missed,by me,and by so many others.I particularly miss the constancy I derived by thinking of him down in Pasadena on the third floor of South ...     

On the mode theory of V. L. F. ionospheric propagation

Summary The space between the earth and the ionosphere is considered as a wave-guide with sharply bounded walls. Employing a representation in terms of spherical wave functions of complex order, the field of a vertical dipole source is calculated for very low frequencies. It is shown that the dominant mode for 16 kc is of order one and not zero as has been commonly supposed. Good agreement is obtained with the experimental results ofJ. Heritage.Paper presented at «Colloque International sur la propagation des Ondes Radio électriques» Paris, September 1956.     

V. A. Troitskaya: the Founder of the Russian School of Geomagnetic Pulsations

A thorough investigation of short-period oscillations in the Earth’s magnetic field as a fundamental natural process of the magnetospheric plasma began in Russia after V.A. Troitskaya established two oscillatory regimes in the geomagnetic field, namely, the regimes of continuous (Pc) and irregular pulsations (Pi). For studying these pulsations, 19 stations recording the telluric currents were installed during the International Geophysical Year (IGY, 1957–1959) on Troitskaya’s initiative. One of these stations was the Borok station. Subsequently, Borok has become the basic site for investigating geomagnetic pulsations and the main center for studying the short-period pulsations (SPPs) in the Earth’s magnetic field. This is the Borok scientific station where the key fundamental regularities of different types of geomagnetic pulsations were established. Troitskaya led and actively participated these works. Troitskaya organized and conducted the first complex geomagnetic observations in the world at the conjugate points Sogra (Arkhangelsk region, Russia) and Kerguelen (Indian Ocean). These studies were initially tested at the Borok observatory, where it was established that the wave packets of Pc1 geomagnetic pulsations are alternately observed in the northern and southern hemispheres in contrast to the other pulsation types which simultaneously occur in both hemispheres. The studies carried out at Borok promoted the establishment of a new direction in geophysics—diagnostics of the state of the magnetosphere based on the ground observations of geomagnetic pulsations. The analysis of simultaneous observations of the geomagnetic pulsations at polar latitudes of the Arctic and Antarctic was also for the first time conducted at the Borok observatory. This analysis revealed the main characteristics of wave phenomena at the geomagnetic poles and in the vicinity of the projection of the dayside polar cusp. Thus, for the first time in the world, Troitskaya and her Borok colleagues established the key patterns of the oscillatory regimes in the geomagnetic field of the Earth. This laid the basis for the further experimental and theoretical investigations which have shown that SPPs play a leading role in the dynamics of the magnetospheric plasma. In this paper we also list of 60 of Troitskaya’s main publications.     

In memory of Donald V. Helmberger

When I received the shocking news on August 13,2020 that our beloved Don passed away,I was deeply saddened.The feeling was worsened by the COVID-19 pandemic tha...     

V. V. Beloussov and Geophysics: A Tribute on His 110th Birth Anniversary

The contribution made by V.V. Beloussov (1907–1990), an outstanding Earth scientist in the former Soviet Union and Russia, to the development of planetary geophysics is considered. Beloussov was a brilliant coordinator of international cooperation and direct inspirer of international scientific programs of paramount importance. He took up one of the key positions in organizing and holding the International Geophysical Year (IGY) in 1957–1958. In 1960, Beloussov was elected President of the International Union of Geodesy and Geophysics and proposed the project “The upper mantle and its influence on the Earth’s crust,” which subsequently became known worldwide as the Upper Mantle Project. The project underlined that the experience of the IGY should be extended to studies of the deep structure of the Earth and the processes taking place in the Earth’s interior. The fulfillment of this and the subsequent Geodynamic project resulted in a breakthrough in the knowledge about the deep structure of the Earth, particularly the structure of the oceans. Beloussov actively advocated integrating science of the Earth, geonomy, and in his scientific research sought a geonomic approach incorporating the entire complex of geological, geophysical, and geochemical data. Beloussov’s scientific heritage contains propositions that are of current importance and can be involved in modern developments of the Earth sciences.     

Multiple reflections between the earth and the ionosphere in V.L.F. propagation

Summary Treating the ionosphere as a sharply bounded ionized medium, sky wave field intensities are calculated by geometrical-optical methods for very low radio frequencies. The reflection coefficients are discussed in some detail and the numerical data are compared with experiment.     

Errata for B.V.E. no. 28

Errata for B.V.E. no. 28     

How Donald V. Helmberger inspired me

I first met Don Helmberger when I visited Caltech in the spring of 1984 as a prospective graduate student.During that visit,I was immediately impressed by Don's...     

Graduate studies with Donald V. Helmberger

Arriving at the Seismo Lab in 1981,I first worked with Hiroo Kanamori on the seismotectonics of the New Hebrides(Vidale and Kanamori,1983)(I don't remember why)...     

Deep diving with Donald V. Helmberger

It has been more than a year since Don left us.He left us so suddenly.We planned to have a phone call after he settled down at his new house.However,it never ha...     

The Lost and the Found: Memories of Donald V. Helmberger

My first exposure to Don Helmberger's work was during a seismology class in my 2nd year in college where several students,including myself,were to present on Gr...     

弗拉基米尔·伊萨科维奇·凯利斯-博罗克院士80周岁诞辰

凯利斯 -博罗克院士是俄罗斯地震学和数学地球物理学领域杰出的科学家。他的高尚人品、科学的洞察力、活动能力以及他能从大量事实中择其主的聪明才智 ,使得他总能发现新的、常常是别人尚未提出的全球性问题 ,并团结各科学领域的专家进行研究。凯利斯 -博罗克建立了俄罗斯科学院国际地震预报理论和数学地球物理学研究所 ,并担任了首任所长。从 1 966年起他亲自编辑出版了《计算地震学》年度著作文集。凯利斯 -博罗克在科学活动初期专门从事数学地球物理学一些经典问题的研究 ,初期的研究是建立地震震源模型以及根据观测资料重建震源区的地面…     

Recollections of my mentor,Donald V. Helmberger

I arrived at Caltech as a graduate student in the summer of 1979.With a BSc degree in physics,I knew little to nothing about seismology or geophysics.The Seismo...