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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.

The theme of this paper is to show that the temperature rising rate by the greenhouse gases is only 1/5 of what is generally considered. This conclusion is based on identifying two natural global changes. One of them is a near-linear change after the Little Ice Age (LIA) and the second is the Pacific (PDO) and Atlantic AMO) decadal oscillations, together called MDO. After the end of the LIA in about 1850, the rising rate of temperature rise has been approximately linear with the rate + 0.3°C/100 years, while the MDO has been super9 posed on it with an amplitude of 0.2°C (the range = 0.4ºC) and the period of 40-60 years. The combined rise of temperature by the two natural components between 1975 and 2000 (which is considered to be due to CO2 by the IPCC) is 0.47°C; it is comparable with the observed rise of 0.5°C during the same period. Thus, the contribution of the greenhouse gases for the same period is estimated to be at most 0.1°C, not 0.5°C.It is estimated that the temperature rise from 2000 to 2100 will be 0.9°C± 0.2°C (=‘recovery’ from LIA + greenhouse gases + MDO), namely 0.3°C + 0.4°C ± 0.2°C, namely between 0.7°C and 1.1°C, assuming that the present production rate of the greenhouse gases is maintained.

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.

Four major subjects in solar physics, the heating of the corona, the cause of the solar wind, the formation of sunspots and the cause of solar flares, are discussed on the basis of the electric current approach, a sequence of processes consisting of power supply(dynamo), transmission (currents/circuits) and dissipation(high coronal temperature, solar wind, sunspots and solar flares).This is because the four subjects have hardly been considered in terms of the electric current approach in the past, in spite of the fact that these subjects are various manifestations of electromagnetic processes. It is shown that this approach provides a new systematic way of considering each subject; (1) the long-standing issue of the coronal temperature, (2)the long-standing problem on the cause of the solar wind, (3)the presence of single spots(forgotten or dismissed in the past) and its relation to unipolar magnetic regions and (4) the crucial power/energy source and subsequent explosive processes of solar flares. The four subjects are obviously extremely complicated and difficult subjects, but it is hoped that the electric current approach might provide a new insight in considering the four subjects.

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)

The high temperature of the corona, 2 x 106 K, recognized by the presence of highly ionized atoms, such as FeXIV, is caused by the ionization of accelerated electrons by a dou...

Both auroral substorms and solar flares have explosive nature. Since both are mostly various manifestations of electromagnetic energy dissipation processes, it is basic to consider both phenomena as a chain of electromagnetic processes, which consists of a dynamo process as the power supply, power transmission and manifestations of dissipative processes (auroral substorms and solar flares)-- the electric current approach. Based on this view, since both phenomena are powered by a dynamo and have an explosive component, they are likely to have the component directly driven (DD) by the dynamo and the component which results from the unloading (UL) process of accumulated energy (generated also by the dynamo). Thus, it is crucial to identify and distinguish the dynamo-produced power/energy/dissipation into two components in both morphology and theory. In this paper, since we have taken this approach for auroral substorms, we attempt to apply it for solar flares by adopting a photospheric dynamo theory by Lee et al. (1995) and Choe and Lee (1996a, 1996b); their dynamo process takes place on the photosphere under a magnetic arcade. It is shown that their dynamo can supply both the power and energy needed for flares, providing the arcade field-aligned currents for the two-ribbon Hα emission (DD) and the current loop along the dark filament above the arcade for the explosive process (UL).

A morphological examination of the Kitt Peak photospheric magnetic maps has been made over three sunspot cycles in order to study the morphology of unipolar magnetic regions and sunspots. Unipolar magnetic regions (positive and negative) are a series of weak, large-scale longitudinal bands, extending from 0° to 60° in latitude and alternatively aligned in longitude. The first finding is that unipolar regions grow and decay with the sunspot cycle and thus are likely to be a part of the basic solar (dipolar) magnetism, not old active regions located below 30° in latitude (as have long been considered). The second finding is that positive pores and single spots (coalesced pores, often called ‘isolated’ spots or ‘independent’ spots) occur in a positive unipolar region (vice vera). Thus, the unipolar regions could be the source of single spots. The third finding is that a pair (positive and negative) of dense clusters of pores, single spots and large spots (a coalesced single spots) occur at each side of the boundary of neighboring (positive and negative) unipolar regions, forming pairs of spots across the boundary; in fact, pairs of spots do not occur in the middle of a unipolar region. The boundaries of unipolar regions are tentatively identified as the Hale boundary, where solar activities (including solar flares) occur). Thus, it is suggested that the presently accepted magnetic tube theory may need a new consideration.

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.

At the present time, there is no quantitative way to predict not only the onset time of solar flares, but also their intensity. In the past, most solar flare prediction studies have searched for various precursors of the onset of flares. In this paper, we consider a new and quantitative approach to predict the onset of the explosive process of solar flares and their intensity, based on the principle that solar flares are basically various manifestations of electromagnetic energy dissipation, so that a dynamo process in the photosphere as its power supply is essential. The power is a basic physical quantity (erg/s), so that it can, at least in principle, be universally applicable for all flares. The power of the photospheric dynamo is given by the Poynting flux P= V(B2/8π)S erg/s, where V and B are the plasma speed and magnetic field intensity, and S is the dimension of the plasma flow; these quantities are in principle observable simultaneously all together, in addition to the dissipation rate δ (for example, the Hα emission rate). In fact, if one can follow the development of the power P(t) and [∫ P(t)dt − ∫ δ(t)dt], it may be possible, together with various precursors, to predict in principle the onset time and the intensity of flares at least semi-quantitatively, although this task will require much experience on the basis of a large number of flares. Unfortunately, however, all the needed simultaneous data set (V, B, S, δ) is not available in the present literature, so that one incomplete case is examined. This concept has been examined for auroral substorms, which are also manifestations of electromagnetic energy dissipation and have the explosive feature. This was possible, because the simultaneous data sets (V, B, S, δ) are available.

Arctic sea ice is a key component of the Arctic hydrologic cycle. This cycle is connected to land and ocean temperature variations and Arctic snow cover variations, spatially and temporally. Arctic...

There are three major paradigms in the field of solar activity research. They are: 1) Unipolar magnetic regions are remnants of old active regions. 2) A pair of sunspots is formed when a thin magnetic flux tube rises above the photospheric surface. 3) Solar flares occur when magnetic energy in an anti–parallel magnetic configuration is rapidly released by magnetic reconnection. Practically all researches of solar activities during several decades have been based on the above paradigms. Although these three paradigms have been almost universally accepted since the1960s (as many papers state so in their introduction), it may be worthwhile to review them. It is shown that: (i) Unipolar magnetic regions are different from old active regions and are actually one of the fundamental features of the solar internal dynamo process. (ii) A positive single spot is produced by a coalescence process in a positive unipolar magnetic region (vice versa), and a pair of positive and negative spots occurs at the boundary of two unipolar magnetic regions (of the opposite polarity) by a p–spot inducing a f–spot. (iii) Solar flares are powered by the photospheric dynamo process, and their explosive feature is caused by a sudden disruption of the current loop around the region where the dynamo process is in progress. These are examples of an alternative idea for each of the three paradigms and are presented to promote new thinking.

Difficulties of proposing a new idea against a standstill or stagnated paradigm are described. In order to achieve a breakthrough or paradigm change, one requires a creative data assembly, the sense of timing, confidence, courage, patience, endurance and even a wit. A few suggestions are made to overcome the difficulties.

A paradigm transition or change is essential in the development of science. During the transition, there are intense debates and controversies among scientists. In this paper, we attempt to analyze controversies in four levels and also three types of researchers.

The sequence of phenomena consisting of solar flares, coronal mass ejections (CMEs), auroral substorms, and geomagnetic storms is mostly a manifestation of electromagnetic energy dissipation. Thus, first of all, it is natural to consider each of them in terms of a sequence of power supply (dynamo), power transmission (electric currents/circuits), and dissipation (mostly observed phenomena), i.e., as an input–output process and the electric current line approach. Secondly, extending this concept, it is attempted in this paper to consider the whole solar–terrestrial relationship in terms of electric currents. This approach enables us to follow through not only the sequence in solar flares, auroral substorms, and geomagnetic storms but also to connect all phenomena naturally as a continuous flow of magnetic energy (V[B2∕8π]) from the sun across the magnetopause. This consideration gives some insight into all the processes involved equally well compared with the magnetic field line approach, which has been adopted almost exclusively in the past.

It is suggested that the magnetosphere tries to stabilize itself by quickly unloading the magnetic energy accumulated within its main body, when the accumulated magnetic energy exceeds a limited amount, which can be identified as the energy for the expansion phase. It is this process which manifests as the impulsive expansion phase, during which auroral arcs advance well beyond the pre-substom latitude in the midnight sector. It was shown in the previous paper [Akasofu, 2013] that the magnetotail does not have enough magnetic energy for a medium substom (energy 5x1015J; AE = 1000 nT). In this paper, it is shown: (1) The reason of the short life-time (1-1.5 hours) of the expansion phase is due to the fact that a limited amount of magnetic energy accumulated during the growth phase is dissipated in a period similar to the duration of the growth phase (1-1.5 hours); the accumulation rate is similar to the dissipation rate during the expansion phase: (2) When the main body of the magnetosphere accumulates the magnetic energy, it is inflated; β (= [nkT/ B2/8π]) even at XGSM = -6 Re becomes close to 1.0 for magnetic energy (2.9x 1014J) which is less than the amount consumed by a medium intensity substorm. (3) As a result, the plasma sheet current and thus the magnetosphere are expected to become unstable, unloading the accumulated excess magnetic energy and resulting in current reduction and deflation. (4) The resulting deflation can cause an earthward electric field of 5-50 mV/m, which can generate Bostrom's current system, which is mainly responsible in producing various phenomena of the expansion phase. (5) The large range of substorm intensity (AE=100 - 2000 nT) is likely to be due to the location where the energy is accumulated, closer is the distance to the earth (XGSM between -10 Re and -4 Re), more intense the substorm intensity is.

Auroral substorms are mostly manifestations of dissipative processes of electromagnetic energy. Thus, we consider a sequence of processes consisting of the power supply (dynamo), transmission (currents/circuits) and dissipations (auroral substorms-the end product), namely the electric current line approach. This work confirms quantitatively that after accumulating magnetic energy during the growth phase, the magnetosphere unloads the stored magnetic energy impulsively in order to stabilize itself. This work is based on our result that substorms are caused by two current systems, the directly driven (DD) current system and the unloading system (UL). The most crucial finding in this work is the identification of the UL (unloading) current system which is responsible for the expansion phase. A very tentative sequence of the processes leading to the expansion phase (the generation of the UL current system) is suggested for future discussions. This proposed sequence is not necessarily new. Individual processes involved have been considered by many, but the electric current approach can bring them together systematically and provide some new quantitative insights.

In any scientific field, there is always a possibility, in which a particular theory dominates for many years. In this paper, the theory of magnetic reconnection in solar physics and auroral physics is reviewed as an example. It has prevailed for more than a half century in both fields as the “only one” without a concrete progress in understanding the source of energy for solar flares and auroral activities. This unusual situation is analyzed why and how it occurred. Since such a situation could occur in any scientific field, it may be useful to analyze how this situation happened. Actually, it is pointed out that a study of global warming may also be in a similar situation.

One of the important tasks of space weather prediction is to forecast the arrival of sub– cosmic ray particles and the onset/intensity of geomagnetic storms after solar flares. For these purposes, it is necessary to predict the onset/intensity of solar flares, to track the transit (or propagation) of coronal mass ejections (CMEs) in interplanetary space and finally to estimate the power (erg/s or w) produced by the interaction between CMEs and the magnetosphere. I find that a much more integrated and coordinated effort is needed than in the past in advancing the present space weather prediction. A few suggestions are provided for this purpose.

In this short paper, I emphasized that creativity in research is best demonstrated by a synthesis effort of observed facts, which could bring a paradigm change and produce a step-wise progress (“breakthrough”) in science.

[1] Characteristics of the ionospheric current system (the directly driven (DD) / unloading (UL) currents) and the power e during auroral substorms are examined semiquantitatively in terms of input-output relationship. The study confirms (a) The magnetic energy for the expansion phase is accumulated with the rate of a little more than 1018 erg/s during the growth phase which lasts for about 1 h (because the ionosphere cannot dissipate the input power). (b) The global energy dissipation rate in the ionosphere (including the Joule heat production and the particle precipitation) is more than 3.3 × 1018 erg/s. (c) Thus, the total energy consumption by the ionosphere during the impulsive expansion phase (lasting for about 1 h) is 1.2 × 1022 erg or up to 1023 erg for medium substorms. (d) However, it is shown that even the total magnetic energy in the magnetotail at a distance between 10 RE and 20 RE (6.5 × 1021 ergs = 6.5 × 1014 J) cannot supply the energy for the expansion phase. This estimate is consistent with the most recent satellite observations (4.3 × 1013 J (= 4.3 × 1020 ergs)). Thus, the following conclusions may be applicable for medium intensity substorms: (i) The major part of the magnetic energy for the expansion phase must be accumulated within a distance of 10 RE and be released almost totally during the expansion phase (because the duration of the growth phase and the expansion phase is about the same). (ii) This suggests that there is an upper limit of the energy which the magnetosphere can accumulate even at distances less than 10 RE. Further, it is confirmed that: (a) The expansion phase is characterized by a single cell current system UL (not a twin cell current system DD which is driven by the earthward plasma convection from the magnetotail). (b) The UL current is independent of the DD current, requiring a different origin. (c) During the recovery phase, the UL current is absent and the DD current approximately follows e (no accumulation of the energy), because the ionosphere is capable of dissipating the power even if the power is moderate). (d) Based on these results, as an example, one possible chain of processes within 10 RE is proposed as the release process of the accumulated magnetic energy by taking into account the fact that the frozen-in field condition is observed to be broken down.

On the basis of auroral and polar magnetic substorm studies, the relationship between the solar wind-magnetosphere dynamo (the DD dynamo) current and the substorm dynamo (the UL dynamo) current is studied. The characteristics of both the DD and UL currents reveal why auroral substorms consist of the three distinct phases after the input power ε is increased above 1018 erg s−1. (a) The growth phase; the magnetosphere can accumulate magnetic energy for auroral substorms, when the ionosphere cannot dissipate the power before the expansion phase. (b) The expansion phase; the magnetosphere releases the accumulated magnetic energy during the growth phase in a pulse-like manner in a few hours, because it tries to stabilize itself when the accumulated energy reaches to about 1023 erg s−1. (c) The recovery phase; the magnetosphere becomes an ordinary dissipative system after the expansion phase, because the ionosphere becomes capable of dissipating the power with the rate of 1018 ~ 1019 erg s−1. On the basis of the above conclusion, it is suggested that the magnetosphere accomplishes the pulse-like release process (resulting in spectacular auroral activities) by producing plasma instabilities in the current sheet, thus reducing the current. The resulting contraction of the magnetic field lines (expending the accumulated magnetic energy), together with break down of the "frozen-in" field condition at distances of less than 10 RE, establishes the substorm dynamo that generates an earthward electric field (Lui and Kamide, 2003; Akasofu, 2011). It is this electric field which manifests as the expansion phase. A recent satellite observation at a distance of as close as 8.1 RE by Lui (2011) seems to support strongly the occurrence of the chain of processes suggested in the above. It is hoped that although the concept presented here is very crude, it will serve in providing one way of studying the three phases of auroral substorms. In turn, a better understanding of auroral substorms will also be useful in studying the magnetosphere, because various auroral activities can be the visible guide for this endeavor.

The concept of geomagnetic storm-producing solar plasma flows has evolved and advanced considerably over the last 100 years or so. This particular field of study began in an effort to understand geomagnetic disturbances and the aurora. The purpose of this paper is try to follow the ways in which early concepts evolved to later ones, not to review each concept in detail. It is fascinating to see a step-by-step buildup of these concepts, from the earliest idea of flow of solar electrons to coronal mass ejections (CMEs). The time line, though tentative, of the studies of geomagnetic storm-producing plasma flows is presented. The author hopes that this paper will serve young researchers in particular to consider how they plan to advance further this scientific field. There is still much uncertainty about geomagnetic storm-producing solar plasma flows. Some of the major questions are listed from the point of view of a geophysicist in the summary sections by grouping them in terms of the quiet-time solar wind, solar streams from corona holes and CMEs associated with solar flares.

In 1967, at the Birkeland Symposium in Sandefjord, Norway, Professor Hannes Alfvén stated that the second approach (in solving unsolved problems by the standard MHD theory) to cosmic electrodynamics is to "thaw" the "frozen-in" magnetic field lines. "We can illustrate essential properties of the electromagnetic state of space either by depicting the magnetic field lines or by depicting electric current lines," he said. There has been much progress in space physics since the Birkeland Symposium more than 40 years ago, but unfortunately our scientific community has not really succeeded in thawing the frozen-in field lines. Instead, it has pursued magnetic reconnection, a concept that Alfvén had been critical of. It is shown here that we have to study many unsolved problems and problems thought to be solved in terms of both the magnetic field line concept and the current system concept. In taking Alfvén's approach, we must consider the whole system, including the power supply (dynamo process) and its transmission and distribution (electric currents) and observed phenomena (power dissipation processes). Such a consideration can provide physical insight into many of our unsolved problems and problems thought to be solved. In this paper, we consider substorm onset processes, the substorm current system, sunspots, solar flares, coronal mass ejections, the interplanetary current sheet, and the magnetic field configuration of the heliosphere in terms of the current system concept. In particular, it is shown that a study of the current system is essential in substorm studies, more than changes of the magnetic field configuration in the magnetotail.

A number of published papers and openly available data on sea level changes, glacier retreat, freezing/break-up dates of rivers, sea ice retreat, tree-ring observations, ice cores and changes of the cosmic-ray intensity, from the year 1000 to the present, are studied to examine how the Earth has recovered from the Little Ice Age (LIA). We learn that the recovery from the LIA has proceeded continuously, roughly in a linear manner, from 1800-1850 to the present. The rate of the recovery in terms of temperature is about 0.5°C/100 years and thus it has important implications for understanding the present global warming. It is suggested on the basis of a much longer period covering that the Earth is still in the process of recovery from the LIA; there is no sign to indicate the end of the recovery before 1900. Cosmic-ray intensity data show that solar activity was related to both the LIA and its recovery. The multi-decadal oscillation of a period of 50 to 60 years was superposed on the linear change; it peaked in 1940 and 2000, causing the halting of warming temporarily after 2000. These changes are natural changes, and in order to determine the contribution of the manmade greenhouse effect, there is an urgent need to identify them correctly and accurately and remove them

The basic observations for magnetic storms and substorms at Earth and for flares at the Sun are reviewed for background. We present a common scenario of double magnetic reconnection for both substorms and flares based on previous interplanetary observations and substorm-triggering results. Central to the scenario is that the first magnetic reconnection phase is the source of energy loading for possible substorms and flares. The energy placed in the magnetotail or magnetosphere/at the sun lasts for only a short duration of time however. The energy gets dissipates away rapidly (in some less dramatic form). This scenario predicts that if the initial reconnection process is sufficiently intense and rapid, concomitant substorms and flares occur soon thereafter. If the energy input is less rapid, there may be lengthy delays for the onset of substorms and flares. If external influences (shocks, etc.) occur during the latter energy buildup, the “trigger” will cause a sudden release of this energy. The model also explains reconnection without subsequent substorms and flares. The model addresses the question why strong triggering events are sometimes ineffective.

The spectacular auroras that circle Earth's geomagnetic poles and burst with colorful displays during geomagnetic storms have mystified humanity for millennia. Now scientists are uncovering their secrets.

Forecasting the arrival of solar-generated shocks and accelerated protons anywhere in the heliosphere presents an awesome challenge in the new field of space weather. Currently, observations of solar wind plasmas and interplanetary magnetic fields are made at the sun-Earth libration point, L1, about 0.01 astronomical units (∼245 Earth radii) sunward of our planet. An obvious analogy is the pilot tube that protrudes ahead of a supersonic vehicle. The Advanced Composition Explorer and Solar and Heliospheric Observatory spacecraft, currently performing this function, provide about -1 h advance notice of impending arrival of interplanetary disturbances. The signatures of these disturbances may be manifested as interplanetary shock waves and/or coronal mass ejecta. We describe a first-generation procedure, based on first-principles numerical modeling, that provides the key links required to increase the advance notice (or lead time) to days, or even weeks. This procedure, instituted at the start of the present solar cycle 23, involves three separate models, used in real time, to predict the arrival of solar-event-initiated interplanetary shock waves at the L1 location. We present statistical results, using L1 observations as ground truth for 380 events. We also briefly discuss how one of these models (Hakamada-Akasofu-Fry version 2) may be used with a model that predicts the flux and fluence of energetic particles, for energies up to 100 MeV, that are generated by these propagating interplanetary shock waves.

We present the design, implementation, present status, and preliminary use of an operational forecaster-friendly solar wind prediction system. We have tested this architecture in our real-time "fearless forecast" prediction study of interplanetary shock arrival time (SAT) at Earth. This study has progressed on a continuous basis since 1997, near the rise of Solar Cycle 23. Comparisons of predicted SAT with observed SAT provide a measure of model forecast skill. We present our kinematic model's forecast skill statistics as compared with several other SAT models and propose important reference metrics for evaluating this and any other interplanetary modeling system. Our prediction system is presently being extended, via a hybrid approach, to include a three-dimensional magnetohydrodynamic (MHD) model. This procedure will accommodate proxy inputs for simulating interplanetary disturbances that are associated with various forms of solar activity (flares, disappearing filaments, coronal mass ejection imagery, shocks). The objective is to provide a capability in the near term to predict, shortly after the launch of large-scale structures at the Sun, the time-dependent interplanetary magnetic field vector (including the north-south component, Bz) at Earth. This is a key requirement for predicting geomagnetic storms.