TABLE 844.— SOLAR FLARES* 



743 



Class 



1 



Mean area in 

 10 -6 of sun's 

 hemisphere 



217 



570 



Mean 



duration 



17 min 

 29 " 



Mean 

 duration 



62 min 

 3 hr 



The following paragraphs are reprinted from F. Hoyle, "Some Recent Researches in 

 Solar Physics," p. 36, Cambridge University Press, 1949. + 



Flares are a particular class of bright reversal characterized by sudden commence- 

 ments. The properties of flares are : 



(a) They are roughly classified in order of increasing importance as 1,2, 3, and 3 +. 

 The area of the flare, seen in projection against the solar disk, is, at present, used as the 

 criterion of importance. Flares of class 3 + are rare, occurring on an average only once 

 or twice per year. At the other extreme, flares of class 1 occur every few hours during 

 periods of marked solar activity. 



(b) The effective line width in H a at peak intensity varies between 1.75 A and 16 A. 

 being approximately proportional to the importance of the flare. // /3, H y show lesser 

 widths, but the data for these are somewhat meager. 



(c) The contour of the bright emission is nearly symmetrical about the normal position 

 of H a and is independent of the position of the flare upon the disk (there is invariably a 

 greater extension in the red wing than in the blue wing, which increases with the impor- 

 tance of the flare, reaching 0.7 A for those of the greatest intensity). Doppler displace- 

 ments of the contour indicating large-scale turbulence of the emitting material in the line 

 of sight have not been observed in excess of ± 10 km/sec. 



(d) Flares are associated with sunspots, and in particular with complicated spot groups. 

 The size of a sunspot, however, is not always a criterion of flare activity, some large spots 

 being relatively inactive. The emitting material is mainly situated either in the reversing 

 layer or the lower chromosphere, and the emission occurs in a region with fixed position 

 relative to the position of the spot group. The areas of flares projected on the solar disk 

 vary from a few hundred millionths up to the values exceeding 10,000 millionths of the 

 area of the disk. The duration of a flare is usually of the order of an hour or less, but 

 lifetimes > 5 hours occasionally occur. 



(e) Flares are strongly correlated with a number of terrestrial effects. Radio fadeouts, 

 due to increased ionization in the D-layer, occur simultaneously with the visible appearance 

 of intense flares. Great magnetic storms are associated with flares of classes 3 and 3 +. 

 The magnetic disturbances commence about 26 hours after the appearance of the flare, 

 and are most marked when the flare is near the center of the disk. Finally, there is a 

 growing body of evidence that the sun emits exceptionally high intensities in the radio 

 meter wave-band during flares. 



* Prepared by Edith J. Tebo, Harvard College Observatory. t Used with permission of the author. 



TABLE 845.— CONSTELLATION ABBREVIATIONS (Astron. Union, 1922) 



Andromeda . . . And 



Antlia . . . •. Ant 



Apus Aps 



Aquarius Aqr 



Aquila Aql 



Ara Ara 



Aries Ari 



Auriga Aur 



Rootes Boo 



Caelum Cae 



Camelopardalis. Cam 



<~ancer Cnc 



Canes Venatici.CVn 

 Canis Major . . CMa 

 Minor . . CMi 

 Capricornus . . . Cap 



Carina Car 



Cassiopeia .... Cas 



Centaurus Cen 



Cepheus Cep 



Cetus Cet 



Chamaeleon . . . Cha 



Circinus Cir 



Columba Col 



Coma Beren . . Com 

 Corona Aust . . Cr A 

 Corona Bor . . . CrB 



Corvus Crv 



Crater Crt 



Crux . . . : Cru 



Cygnus Cyg 



Delphinus .... Del 



Dorado Dor 



Draco Dra 



Equuleus Equ 



Eridanus Eri 



Fornax For 



Gemini Gem 



Grus Gru 



Hercules Her 



Horologium . . Hor 



Hydra Hya 



Hydrus Hyi 



Indus Ind 



Lacerta Lac 



Leo Leo 



Leo Minor .... LMi 



Lepus Lep 



Libra Lib 



Lupus Lup 



Lynx Lyn 



Lyra Lvr 



Mensa Men 



Microscopium . Mic 

 Monoceros .... Mon 



Musca Mus 



Norma Nor 



Octans Oct 



Ophiuchus .... Oph 



Orion Ori 



Pavo Pav 



Pegasus Peg 



Perseus Per 



Phoenix Phe 



Pictor Pic 



Pisces Psc 



Pisces Austr . . PsA 



Puppis Pup 



Pyxis Pyx 



Reticulum .... Ret 



Sagitta Sge 



Sagittarius .... Sgr 



Scorpius Sco 



Sculptor Scl 



Scutum Set 



Serpens Ser 



Sextans Sex 



Taurus Tau 



Telescopium . . Tel 

 Triangulum . . . Tri 



" Austr . . . Tr A 



Tucana Tuc 



Ursa Major . . . UMa 



" Minor . . . UMi 



Vela Vel 



Virgo Vir 



Volans Vol 



Vulpecula Vul 



SMITHSONIAN PHYSICAL TABLES 



