TY - GEN
T1 - Effect of shock normal orientation fluctuations on field-aligned beam distributions
AU - Meziane, K.
AU - Hamza, A. M.
AU - Wilber, M.
AU - Lee, M. A.
AU - Mazelle, C.
AU - Lucek, E. A.
AU - Hada, T.
AU - Markowitch, A.
N1 - Funding Information:
Acknowledgements Work at U.N.B. is supported NSERC. Work at U.C. Berkeley is supported by NASA Grant NNG05GF99G. The authors are grateful to the International Space Science Institute for supporting topics related to shock acceleration.
Publisher Copyright:
© Springer Science+Business Media B.V. 2010.
PY - 2010
Y1 - 2010
N2 - We address the unsolved question of how foreshock field-aligned beam (FAB) parallel temperatures are produced. Studies including numerical simulations and recent observations have indicated that shocks can be nonstationary and include embedded spatial structures with varied scales. As a first step towards assessing the impact of such variability on backstreaming ions, we examine how a randomly distributed shock normal direction will affect FAB parallel velocity (v||) distributions. Assuming that the FABs are produced in a quasi-adiabatic reflection process at the shock, we derive a probability distribution function for v||. These derived distributions exhibit second, third and fourth order moments that agree well with the observations for a large range of reflection efficiencies δ, and depend strongly upon the average angle between the magnetic field and the shock normal θBn0. Best agreement is obtained for fluctuations of the normal orientation of a few degrees about a nominal direction. The derived model predicts a strong correlation between the shock geometry (θBn0) and the moments of the parallel velocity distribution, but with stronger tails extending to higher values of θBn0, a trend opposite to the observations.
AB - We address the unsolved question of how foreshock field-aligned beam (FAB) parallel temperatures are produced. Studies including numerical simulations and recent observations have indicated that shocks can be nonstationary and include embedded spatial structures with varied scales. As a first step towards assessing the impact of such variability on backstreaming ions, we examine how a randomly distributed shock normal direction will affect FAB parallel velocity (v||) distributions. Assuming that the FABs are produced in a quasi-adiabatic reflection process at the shock, we derive a probability distribution function for v||. These derived distributions exhibit second, third and fourth order moments that agree well with the observations for a large range of reflection efficiencies δ, and depend strongly upon the average angle between the magnetic field and the shock normal θBn0. Best agreement is obtained for fluctuations of the normal orientation of a few degrees about a nominal direction. The derived model predicts a strong correlation between the shock geometry (θBn0) and the moments of the parallel velocity distribution, but with stronger tails extending to higher values of θBn0, a trend opposite to the observations.
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U2 - 10.1007/978-90-481-3499-1_23
DO - 10.1007/978-90-481-3499-1_23
M3 - Conference contribution
AN - SCOPUS:80455137759
SN - 9780387727677
SN - 9780387876207
SN - 9781402055720
SN - 9781402069321
SN - 9781402088674
SN - 9781402091896
SN - 9781441981608
SN - 9781441983688
SN - 9783540758259
SN - 9783642033230
SN - 9783642103216
SN - 9783642103513
SN - 9783642113406
SN - 9783642172502
SN - 9789048133994
SN - 9789048134984
SN - 9789048134984
T3 - Astrophysics and Space Science Proceedings
SP - 349
EP - 362
BT - Astrophysics and Space Science Proceedings
A2 - Laakso, Harri
A2 - Taylor, Matthew
A2 - Escoubet, C. Philippe
PB - Springer Science and Business Media B.V.
T2 - 15th Workshop on Cluster Active Archive, 2008
Y2 - 9 March 2008 through 15 March 2008
ER -