Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1765795 | Advances in Space Research | 2009 | 7 Pages |
Abstract
We revisit the transient interplanetary events of January 1 and September 23, 1978. Using in-situ and remote sensing observations at locations widely separated in longitudes and distances from the Sun, we infer that in both cases the overall shock surface had a very fast “nose” region with speeds >900 and >1500 kmâ1 in the January and September events, respectively, and much slower flank speeds (â¼600 kmâ1 or less), suggesting a shock surface with a strong speed gradient with heliospheric longitude. The shock-nose regions are thus likely efficient acceleration sites of MeV ions, even at 1 AU from the Sun. Our 3D magnetohydrodynamics modeling suggests that a 24° Ã 24° localized disturbance at 18 solar radii injecting momentum 100 times the background solar wind input over 1 h can produce a disturbance in semi-quantitative agreement with the observed shock arrival time, plasma density and velocity time series in the January 1978 event.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Space and Planetary Science
Authors
D.B. Berdichevsky, D.V. Reames, C.-C. Wu, R. Schwenn, R.P. Lepping, R.J. MacDowall, C.J. Farrugia, J.-L. Bougeret, C. Ng, A.J. Lazarus,