After its more than 80 years long history, the dynamo problem has finally approached to the goal of one’s ambition to unveil its grand mystery of creation and reversal of the geodynamic field in a self-consistent fasion. The success in unveiling this long mystery of the dynamo problem has been brought by elaborate large-scale computer simulations. In this review, a brief history of the dynamo problem, both theoretical and observational, is first described. Then the recent exciting demonstrations of the generation and reversal of the self-excited dipole-like magnetic structure done by the UCLA-LANL group and the NIFS group are described.

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The increasing existence of magnetic and electromagnetic fields in the environment has generated a myriad of questions and research activities around the world. Although these fields are beneficial to medicine, scientific research the populace, and industry, anxiety and uncertainty about their hazards have prompted researchers to strive to conclusively ascertain the positive, negative and long-term effects of these fields on biological systems. This paper reviews the biological effects of magnetic and electromagnetic fields that are classified into three categories: (1) time-varying magnetic fields, (2) DC or static magnetic fields, and (3) the multiplication of both static fields and other energy, such as light and radiation.

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The possible health hazard of exposure to low-frequency magnetic fields has become an issue of considerable public concern. Although many epidemiological studies have done, the results are inconsistent to explain an association between exposure to the magnetic fields in the environment and apparent cancer. In in vitro studies, the existence of the effects of the magnetic fields at low flux density has also been contradictory in various reports. This paper reviews studies on cellular and molecular effects of low-frequency magnetic fields.

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With the expanding use of portable telephones, public concerns regarding potential health hazards due to the absorption of electromagnetic energy have been growing. In this article, electromagnetic waves and their resultant biological effects are reviewed. The thermal effects due to RF (radio-frequency) electromagnetic fields and basic proposals for safety standards are described in conjunction with whole-body / localized average SARs (specific absorption rates) being used as bioeffect evaluation measures. Our computed dosimetries of the human head for portable telephones are also shown.

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The review addresses the concerns related to extremely low frequency electromagnetic fields (ELF/EMF) in workplaces. The exposure levels and epidemiological studies on cancer, the health effects of working with VDTs (visual display terminals), and the malfunction of cardiac pacemakers are described. The association of EMF exposure and cancer or disorders from VDT work cannot be considered conclusive. The information on the exposure level and effect of EMF on cardiac pacemakers should be disseminated in workplaces. Risk communication program on EMF is urgent for countermeasures against worker anxiety.

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In order to protect human health from excessive exposure to electromagnetic fields safety guidelines have been established by national and international organizations. The International Commission on Nonionization Radiation Protection is one of these organizations, whose guidelines are briefly regarded as typical. The activities on this issue in various countries are reviewd. Recent situations and the problems still unsolved are also discussed.

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A strong magnetic field is utilized in magnetic confinement fusion machines. A variety of magnetic confinement concepts are emlployed and give rise to the differences electromagnetic field environments. Here we surveyed two examples of confinement machines which are now being intensively investigated: the tokamak ITER and the helical system LHD with a large-scale superconducting coil system. Some safety aspects of high frequency electromagnetic environments related to the high-power plasma heating system are also described.

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The dependence of magnetic fluctuation level on magnetic Reynolds number S is examined in various phases such as current rising up and decay phases. The magnetic fluctuation level is normalized by the total magnetic field at the wall. In low S number regime, m=1 mode is most dominant and its power is larger than m=0, 2 modes, where m is poloidal mode number. It is found that the magnetic fluctuation level is not minimum in the current decay phase but at the plasma current maximum. As the S number increases, the power of m=1 mode transfer to the power of m=0 mode by magnetic reconnection, and the magnetic fluctuation level decreases in proportion to S^-1/2.

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Upon the change of the stochastic parameter, the period-3 accelerator mode of the standard map becomes unstable through hypebolic transition with reflection when the residue R goes over the unity, while it undergoes hyperbolic transition with reflection for the residues R becomes negative. The former case is nothing but the period-doubling bifurcation, in which the formation of new periodic orbits are confirmed with the known symmetry analysis. The hyperbolic transition without reflection however, leads to the birth of a pair of period-3 orbits, which can not he identified as the intersection of known symmetry lines. This finding calls for special interests to explore some kind of hidden symmetry for the hyperbolic transition without reflection in the period-3 accelerator modes of the standard map.

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