The large‐scale structure of flare‐associated interplanetary shocks

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Abstract
The large‐scale structure of flare‐associated interplanetary shocks is investigated by examining the properties of 116 shocks which originated in solar flare events during a 18.7‐year period commencing mid‐May 1967. The best average representation of these shocks is an expansion which is uniform over about 100°. The highest compression ratio across the shock (∼2.7) is about 15° west of the radial from the flare site. The loose coupling of shocks and their drivers is supported by the observation that drivers are generally only detected for shocks originating near central meridian. A comparison of the numbers of shocks per year with the numbers of sudden commencement geomagnetic storms indicates that the percentage of shocks at 1 AU which originate in flare events is less than 50%. Many shock‐flare associations made in the past are probably in error.