Search

Explosive solar activities cause heliospheric disturbances. A simple scheme of simulating the propagation of shock waves in the heliosphere is devised to study such disturbances caused by solar flares. This scheme, the HAF scheme, is capable of simulating the propagation of many shock waves generated during extended periods up to a distance of 100 au (200 days) during periods when many solar disturbances can occur. The capability of the scheme is demonstrated in reproducing: (1) Multi-events with multi-satellite data within 2 au: (2) The heliospheric conditions at Ulysses/ Cassini within 10 au. (3) A successful reproduction of a Pioneer 11 event at 30 au. (4) The heliospheric condition up to 100 au in 2004, in addition to (5) reproducing recurrent geomagnetic srorms. Thus, the method presented here is simple enough in predicting a rough overall pattern of heliospheric disturbances on a day-to-day basis without MHD simulations. In this paper, we assembled systematically (in terms of distance from the sun) the above multiple results during the development of the HAF scheme in different periods by many researchers. It is hoped that much better schemes will be developed by extending and improving the HAF scheme.

This article describes a new understanding of the explosive nature of auroras, called auroral substorms, on the basis of a series of processes, from power supply (dynamo), circuit/current, and dissipation (auroral substorms) – the electric current approach, in which the magnetosphere or more specifically the primary magnetosphere-ionosphere coupling system (the primary M-I system) plays a crucial role. The primary M-I system has an anomaly; it cannot dissipate the dynamo power much for about 1 h after the dynamo power becomes above 1011 w. This anomaly is due to a low conductivity of the quiet-time ionosphere to dissipate increasing power. Thus, the power is accumulated in the inner magnetosphere (at about 6 Re; Re = earth’s radius) as magnetic energy, inflating the inner magnetosphere. When the accumulated energy reaches to about 1016 J, the primary M-I system seems to become unstable and unload impulsively the accumulated magnetic energy, deflating the magnetosphere. This deflating process generates the secondly M-I system, which is associated with an electric field 5–50 mV/m and field-aligned currents, ionizing the ionosphere and increasing the conductivity. Therefore, the primary M-I system can perform like an ordinary electrical system. It is this particular nature that exhibits explosive auroral displays. This paper describes systematically and semiquantitatively key points of this series of processes based on a few decades of work. The electric current approach is rather ‘new’ in substorm research and thus is rudimental at its development stage, so that n crucial issues are mentioned for future studies at the end.

It has long been considered that the high temperature of the solar corona, inferred from the presence of highly ionized atoms such as FeXIV, is caused by various heat transfer processes from the photosphere. In this paper, it is suggested that the neutral hydrogen layer, containing Fe atoms, of the corona, are ionized by the impact of energetic current carrying electrons along loops of magnetic field lines. It is suggested that current-carrying electrons are accelerated by the double layer; the corona consists of a large number of magnetic loops. It is shown that the current of intensity of about 1μA/cm2, consisting of 10 Kev electrons accelerated by the double layer, could provide the ionization rate of 1.8 x 104/cm3 in the corona along the loops. Thus, the corona could not be in a thermal equilibrium, so that the temperature of the corona may not be inferred from what the ionization potential of highly ionized atoms suggests. It is shown also that a dynamo process of the photosphere can generate the needed field-aligned currents. Further, the above estimated ionization rate can supply the solar wind.

Owing to the ever-present solar wind, our vast solar system is full of plasmas. The turbulent solar wind, together with sporadic solar eruptions, introduces various space plasma processes and phenomena in the solar atmosphere all the way to the Earth's ionosphere and atmosphere and outward to interact with the interstellar media to form the heliopause and termination shock. Remarkable progress has been made in space plasma physics in the last 65 years, mainly due to sophisticated in-situ measurements of plasmas, plasma waves, neutral particles, energetic particles, and dust via space-borne satellite instrumentation. Additionally high technology ground-based instrumentation has led to new and greater knowledge of solar and auroral features. As a result, a new branch of space physics, i.e., space weather, has emerged since many of the space physics processes have a direct or indirect influence on humankind. After briefly reviewing the major space physics discoveries before rockets and satellites, we aim to review all our updated understanding on coronal holes, solar flares and coronal mass ejections, which are central to space weather events at Earth, solar wind, storms and substorms, magnetotail and substorms, emphasizing the role of the magnetotail in substorm dynamics, radiation belts/energetic magnetospheric particles, structures and space weather dynamics in the ionosphere, plasma waves, instabilities, and wave-particle interactions, long-period geomagnetic pulsations, auroras, geomagnetically induced currents (GICs), planetary magnetospheres and solar/stellar wind interactions with comets, moons and asteroids, interplanetary discontinuities, shocks and waves, interplanetary dust, space dusty plasmas and solar energetic particles and shocks, including the heliospheric termination shock. This paper is aimed to provide a panoramic view of space physics and space weather., Accepted for publication in IEEE Transactions on Plasma Science (2022)

Space physics is one of the rapidly developing scientific fields, covering space from the sun to a distance of about 100 times between the sun and the earth, the region called the heliosphere. It includes parts of solar physics, geomagnetism (a study of geomagnetic storms), ionospheric physics, auroral physics, cosmic ray physics and planetary physics. The rapid progress in space physics owes a long history of debates and controversies among these sub-fields, as well as the advent of satellites and space probs, which began during the 1960s. A study of geomagnetic storms has an interesting development preceding space physics, so that it may be worthwhile to study history of space physics by following the development of the history of geomagnetic storms. The author has joined in space physics in its earliest days.