Existing and potential customers for space weather predictions can be found in many disciplines. Satellite problems range from ``phantom'' commands to the complete failure of the Japanese geostationary telecommunications satellite CS-3b (in 1989). During one large solar flare sequence certain satellite operators were not aware of satellite anomalies because their communication links to the satellites were inoperable due to the geomagnetic storm itself. Low-altitude, high-inclination satellites experienced periods of uncontrolled tumbling as they transited regions of strong magnetic gradients from field-aligned currents feeding auroral substorm circuits. Communication effects from ionospheric disturbances included the disruption of LORAN navigation systems, HF (high frequency band) communication breakdown, interference from remote low-power transmitters, and disruption of radio navigation signals. Ionospheric heating from precipitating magnetospheric energetic particles and resistive closure of field aligned currents (Joule heating) changes the scale height of the neutral atmosphere and increases the drag on low orbiting satellites. This causes changes in normal satellite orbits which place satellite positions outside the expected ``windows'' of operation. During one storm, the US Air Force and Navy reported large numbers of ``uncorrelated targets'' in space, i.e. unidentified objects, each of which had to be re-acquired and re-identified. Astronauts experienced irritating ``flashes'' in their eyes during the Shuttle Atlantis mission to launch the NASA GALILEO satellite (to Jupiter), as energetic protons penetrated the optic nerves. These did not subside until the proton events ended. Radiation sensors on Concorde supersonic jets showed that passengers and crew received a radiation dose equivalent to a chest X-ray. On the ground, power grids were overloaded, transformers damaged and service disrupted. This compendium of events [ Allen and Wilkinson, 1993] serves to emphasize the diversity of effects and potential customers. For example, SESC currently serves over 25 customer groups, the number of which has been steadily increasing over several decades as the awareness of space weather effects increases. Figure 2 underscores the continuity of the customer base once an application for specification and forecasting is determined.=20
The failure of the Canadian Anik satellite in January, 1994, highlighted that many tens of billions of dollars are invested in satellite systems that are potentially at risk. For example, there are somewhere in excess of 200 commercial and military satellites in geosynchronous orbit from various worldwide sources. Considering that each one may cost of the order of $200 million, that adds up to over $40 billion in hardware in geosynchronous orbit alone. Day-to-day space environment related problems range from aggravation-level, minor impacts to functional loss and/or to actual sub-system and system loss, as in the Anik and CS-3b failures. The dollar loss of the minor impacts is difficult to quantify, but it falls under both direct loss and loss of confidence in the system. The loss of a satellite is in the several $100 million category for hardware plus down time.
It is often difficult to obtain information on satellite anomalies. Even
so, Table 1 provides a listing of 46 instances of operational disturbances
from the Spacecraft Anomaly Database of the National Geophysical Data
Center, covering 25 days in March 1989. The majority of these are diagnosed
to be from electrostatic discharge from spacecraft charging. The
manifestations of this problem are ``phantom commands'': i.e. undesired
changes in the satellite operational set up that were not instigated from
the ground. It is also easy to see that some days are much worse than
others. A quick survey shows that most occur when 
(an index of global
magnetic activity on a logarithmic scale from 0 to 9) is greater than 4,
i.e., increased magnetic activity. This list is made from a small subset of
satellites whose operators are willing to provide information. The total
problem is much larger. It involves both surface charging by keV particles
and deep dielectric charging by MeV electrons. Surface charging problems
occur in the regions where fluxes are enhanced. Deep dielectric charging
results from a cumulative build-up of charge in a dielectric, and the
discharge may occur during the build-up or may be triggered at the time of
greatest flux or at a later time when the threshold is finally exceeded.
The Anik failure has been attributed to deep dielectric charging. The
current up-to-date data base contains over 9000 anomalies covering the time
period from 1970 to the present (D. Wilkinson, private communication, 1994).
Revenues for the commercial satellite industry are in the neighborhood of $5 billion annually. A small percentage increase in operational efficiency translates into large profits. Satellite operators currently wait for problems to happen and then react to try and correct the problem. Some satellites are more susceptible than others, depending on what design mitigation techniques have been implemented. Short term prediction of when a satellite is expected to enter a region with high probability for spacecraft charging would provide a means to take mitigation actions to prevent capability loss rather than to react after the fact to re-boot or repair. Just knowing the magnetic field in geosynchronous orbit is important to those satellites that use magnetic torquing. During intense magnetic storms geosynchronous satellites cross the magnetopause and enter the magnetosheath where the magnetic field is often reversed; hence, applied torques for attitude control could be in the wrong direction. Predictions are needed for the large number of communications satellites at geosynchronous orbit and for those in other orbits such as the orbits in which the Global Positioning System (GPS) satellites fly.
Spacecraft charging has also been observed in low-Earth orbit [ Gussenhoven et al., 1985] although it is not as common because of the high background density of thermal plasma and it occurs only briefly during the transit of the most intense regions of auroral precipitation. Prediction is more difficult because the amount of acceleration of particles between the ionosphere and magnetosphere is not well defined. During intense activity, regions of high probability could be defined.
Substorms are episodic events that release energy stored in the magnetosphere and magnetotail into the high latitude ionosphere, creating intense aurora and magnetic disturbances. Substorms occur at most levels of magnetic activity, but are more frequent and intense during magnetic storms. Auroral activity and intense substorm disturbances cause dropouts and changes in paths of HF communications, increase scintillation degradation of radio signals at higher frequencies, and disrupt surveillance tracking with Over-The-Horizon (OTH) radar. Prediction of irregularity regions could be used pro-actively to optimize communication links and operation of the OTH system.=20
The US Air Force and Navy maintain surveillance of over 6000 objects in space. Increased heating of the high-latitude ionosphere from particle precipitation and Joule heating will change the drag on many of these objects. During the major storms of the last solar maximum, significant numbers of these objects were temporarily lost as orbit parameters were changed by the increased drag. Prediction of these effects would allow operators to maintain tracking of critical objects and plan for an orderly recovery of tracking of others.
Because the ionosphere is a dispersive medium, it introduces additional time delays into the propagation of GPS signals which are proportional to the total electron content (TEC) in the ionosphere along the signal path and inversely proportional to the square of the frequency of the signal. The pseudo-range error from variations in TEC can reach up to 16 m in the zenith and up to 3 times that close to the horizon, changing over times as short as 10 minutes in the high latitude regions and over diurnal time scales at midlatitudes. The error for each of three directional components is added to the basic accuracy of 50 m of the system for civilian users. In practice some of these errors cancel.
Rapid variations in the ionospheric delay can do more damage to the accuracy of GPS for positioning and navigation. Scintillation effects can cause the phase tracking loops in the receivers to temporarily lose lock, introducing discontinuities in the phase derived biased pseudo-ranges. These effects have been observed in the auroral region [e. g. Heroux and Kleusberg, 1989]. At a recent SESC User's Conference a need was expressed for a forecast of the ionosphere for navigation purposes.
Geomagnetic disturbances can induce near DC currents (Geomagnetically Induced Currents, GIC) in long power lines. For instance, during the March 13, 1989, storm, GIC caused a complete shutdown of the Hydro Quebec power grid resulting in a nine hour power outage. The power pools that serve the entire northeastern United States came uncomfortably close to a cascading system collapse [ Kappenman, 1993]. The near DC current causes a net bias in transformer cores, thus creating high levels of half-cycle saturation which cause increased harmonics, excessive localized heating and erratic swings in power levels. As a result of GIC damage to a transformer, the Salem Nuclear Generating plant suffered a complete outage with replacement energy costs of $400,000/day [ Kappenman, 1993].
With the continuance of current trends, it is likely that the bulk power transmission network will become even more susceptible in the future. Electrical energy suppliers maximize their use of existing systems to avoid investments in large generating complexes which cause rate increases to the public. Maximizing the use of existing systems increases the stress on the system through reduced operating margins, increased bulk transmission and increased voltage control requirements [ Thompson, 1993]. Mitigation techniques --- including transmission line series capacitors and neutral blocking devices --- are expensive (Hydro Quebec is investing $1.2 billion for transmission line series capacitors [ Blais and Metsa, 1993]). A more prudent and timely approach for mitigation of the geomagnetic disturbance problem is to significantly improve forecasts and warnings to a level of reliability which permits the initiation of protective actions [ Kappenman, 1993]. Forecasting reliability is important in that counter measures all have an associated cost. Improvements are needed both in the short term forecasting (which doesn't exist) and the long term trend predictions (which needs improvement in solar inputs). Short term predictions could be based in part on both global and regional information provided by models. For the power industry, more region-specific information is required if expensive countermeasures are to be implemented based on forecasts [ Thompson, 1993].
Geomagnetically induced currents and voltages also affect pipelines. An unprotected pipeline in moist soil will, because of slight differences of the metallurgy of the steel and/or the soil that it passes through, set up electrochemical cells which cause corrosion at the anode junction with the soil. To protect these pipelines from corrosion, present technology uses a DC bias current to make the whole pipeline a cathode. Low current is obviously advantageous. However, GIC can easily overpower the applied currents and counteract the protection [ Shapka, 1993]. Forecasts could aid in mitigation technique modeling and application.
On the Earth's surface, magnetic disturbances can produce large induced currents and voltages in long conductors used for telecommunications. Such events have been known to produce disturbances and even disruptions [ Lanzerotti et al., 1983]. During the March 1989 storm, east-west potential changes of as much as 700 V peak-to peak were observed in the transatlantic fiber optic communication cable [ Medford et al., 1989]. Because of conservative design, total system integrity was maintained. However, extreme geomagnetically-induced voltages can affect the engineering performance of systems with long conductors. The probability of occurrence of the most extreme voltage excursions are needed for a number of engineering applications involving these long conductors [ Lanzerotti et al., 1993]. Forecasts could allow pro-active mitigation.
Many manufacturing processes are moving toward ``six sigma'' quality control (3.4 parts/million defective) which is dependent on rigid control of process variables. Manufacturing engineers often experience times when process variables seem out of control. Peaks in some process control problems are coincident with geomagnetic storms. For instance, semiconductor manufacturing product peak-defect patterns show a close relationship to geomagnetic events. In one study, 78% of the peak-defect days were within one day of the peak geomagnetic activity days for a six week period in 1991. While direct effects from magnetic field fluctuations have in some cases been ruled out, secondary effects from GIC induced variations in power line quality are possible [ Pratt, 1993]. Recommended corrective measures include the utilization of geomagnetic activity prediction services.
Manned spaceflight programs require space weather services ranging from prediction of future conditions to real-time monitoring of existing solar and near-Earth space conditions. Energetic solar protons are a radiation health hazard for astronauts. The arrival time in the near-Earth environment can begin within tens of minutes of the eruption of a solar flare. Astronauts outside the shielding afforded by the Shuttle itself are especially vulnerable. While low inclination orbits take advantage of the shielding of the Earth's magnetic field, high inclination orbits place the Shuttle outside normal rigidity cut-offs, allowing increased dosages. The proposed coupling of the US Space Station program with the Russian MIR station will result in still higher inclinations in the future. Prediction and monitoring of solar flares and CMEs provide essential safety constraints. High inclination orbits will also provide more exposure to orbital changes from increased drag during magnetically active periods.