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Velocity of the shock generated by a large east limb flare on August 18, 1979
Author(s) -
Cane H. V.,
Stone R. G.,
Woo R.
Publication year - 1982
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl009i008p00897
Subject(s) - physics , shock (circulatory) , flare , shock wave , astrophysics , spacecraft , solar flare , astronomy , mechanics , medicine
The large flare of August 18, 1979 resulted in a shock which produced intense type II radio emission detected at kilometer wavelengths using the radio astronomy experiment on the ISEE‐3 spacecraft. The drift rate of the type II burst provides estimates of the velocity of the shock as a function of coronal height. A choice of density scale has been facilitated by detection of the shock with radio scattering measurements using the radio signals from Voyager 1 and Pioneer 11. Assuming radial motion of the shock, the spacecraft detections provide estimates of the arrival times of the shock at 13 R ⊙ and 73 R ⊙ . The arrival time of the shock at ISEE‐3 and subsequently at the magnetoshere can also provide estimates of the shock velocity. The resulting profile of velocity as a function of distance is consistent with the shock being driven out to about 0.2 AU and then decelerating with a decreasing outward speed proportional to R −0.8 . The profile presents the first determination of the velocity characteristics of a flare‐produced shock in the height range 0.05‐0.4 AU.