TERRESTRIAL EFFECTS OF SOLAR ACTIVITY 



satellites can be used that are not 

 subject to the "polar blackout" that 

 accompanies any biologically danger- 

 ous particle flux. 



Electromagnetic radiation from so- 

 lar flares can be observed by sensitive 

 radio receivers in the form of radio 

 "noises," or interference, if the sun 

 happens to be in the direction that 

 the antenna is "looking." Observa- 

 tions of the sun's radio emission are 

 required to advise system operators 

 of the nature of the signal they are 

 observing. 



General Observational Data — The 

 researcher needs forecasts and real- 

 time advisories of the occurrence of 

 selected solar and geophysical events 

 in order to schedule and conduct ex- 

 periments. He needs a consistent base 

 of comparable observational data that 

 can be vigorously examined for sig- 

 nificant relationships. 



The State of the Art 



To meet the needs of these various 

 operational and research communi- 

 ties, varied capabilities, skills, and 

 understanding are required. Individ- 

 ually or institutionally, the atmos- 

 pheric scientist and his colleagues 

 must provide the following: 



1. Observations of the sun and 

 the space environment; 



2. Rapid communications and data 

 processing; 



3. Forecasts of significant solar 

 activity and geophysical re- 

 sponses. 



In addition, they must have an un- 

 derstanding of the needs of specific 

 systems and operations, in order to 

 present advice to an operator in the 

 form that will benefit him most. 



Observations of the Sun and the 

 Space Environment — The observa- 

 tions must be continuous, consistent, 



comparable, and, where appropriate, 

 synoptic. They should include, but 

 not be limited to, solar flares, active- 

 region parameters, solar radio emis- 

 sion, space radiation, solar wind, the 

 ionosphere, and the geomagnetic field. 



U.S. civilian and military agencies 

 maintain a network of operational 

 solar observatories around the globe. 

 This network is supplemented by nu- 

 merous scientific observatories. 

 Nearly continuous patrol of solar 

 chromospheric activity has been 

 achieved thereby. But the data ob- 

 tained are not as useful in operational 

 situations as, ideally, they might be. 



First, they are subject to consider- 

 able inconsistency due to the subjec- 

 tive evaluations of the individual 

 observers. To obtain the final de- 

 scription of a solar event, many often 

 highly divergent observations are sta- 

 tistically combined. But in the quasi- 

 real-time frame of operational sup- 

 port, evaluation of a solar event must 

 be made on the basis of only one or 

 two observations. 



Second, patrol of the sun's radio 

 emission is not complete. Gaps in 

 synoptic coverage exist, frequencies 

 useful for diagnosing solar activity 

 are not always available, and some ob- 

 servatories report uncalibrated data. 

 Operational radio patrol is about 90 

 percent effective, nonetheless. 



Unmanned satellites are patrolling 

 energetic-particle emission and some 

 other space parameters for opera- 

 tional use. Real-time energetic-par- 

 ticle patrol presently exceeds 20 hours 

 a day; X-rays, 16 to 18 hours; and 

 solar wind, 8 to 9 hours. The obser- 

 vations are limited, however, in that: 

 (a) they are not continuous; (b) data 

 acquisition and processing are expen- 

 sive; (c) all needed parameters are 

 not sampled; (d) different sensors are 

 not intercomparable; (e) sensor re- 

 sponse changes; and (f) the vehicles 

 have limited lifetimes. Other scien- 

 tific satellites are sampling the space 

 environment, but limited readout and 

 data-processing capabilities and ex- 



perimenters' proprietary rights pre- 

 vent these data from being used 

 operationally. 



Observations of the ionosphere are 

 being made using vertical- and 

 oblique-incidence ionosondes, riome- 

 ters, and sudden-ionospheric-disturb- 

 ance sensors. For operational use, 

 however, timely receipt of data is 

 available from only about 20 loca- 

 tions around the world. 



Several other observations of solar 

 and geophysical parameters are being 

 made for operational use. These in- 

 clude radio maps of the sun, ground- 

 based neutron monitors, and geomag- 

 netic-field observations. In general, 

 they suffer from the same limitations 

 as the observational networks de- 

 scribed earlier. 



The recent establishment of World 

 Data Centers for storing and ex- 

 changing space data represents a sig- 

 nificant advance. These centers are 

 supported by the Inter-Union Com- 

 mission on Solar-Terrestrial Physics 

 of the International Council of Scien- 

 tific Unions. However, the primary 

 benefit comes to the research com- 

 munity rather than directly to the 

 operational community. Furthermore, 

 the program still suffers from incon- 

 sistencies, incomparabilities, and in- 

 completeness of much of the data. 



Rapid Communications and Data 

 Processing — Rapid communication 

 and processing of data are essential 

 for timely forecasts. Even in the ab- 

 sence of forecast capability, they are 

 required to make maximum opera- 

 tional use of observations. 



The Air Force has designated a 

 special teletype circuit for the rapid 

 movement and exchange of solar- 

 physical data within the United 

 States. Both civil and military agen- 

 cies have access to it. This circuit 

 makes possible near-real-time relay. 

 Data from the overseas observatories 

 must be relayed by more complex and 

 time-consuming means. 



15 



