HR: 08:30h
AN: SH11B-03    [PDF]
TI: Wavelength and decay scale of the density overshoot at collisionless shocks
AU: * Saxena, R
EM: rsaxena@ssl.berkeley.edu
AF: University of California, Berkeley, Space Sciences Laboratory University of California, Berkeley, CA 94720-7450 United States
AU: Bale, S D
EM: bale@ssl.berkeley.edu
AF: University of California, Berkeley, Space Sciences Laboratory University of California, Berkeley, CA 94720-7450 United States
AU: Mozer, F S
EM: fmozer@ssl.berkeley.edu
AF: University of California, Berkeley, Space Sciences Laboratory University of California, Berkeley, CA 94720-7450 United States
AU: Horbury, T
EM: t.horbury@ic.ac.uk
AF: Imperial College, The Blackett Laboratory Imperial College, London, SW7 United Kingdom
AB: Using spacecraft potential data from the Cluster spacecraft, we study the overshoot/undershoot density structure at 71 crossings of the quasi-perpendicular bow shock. The envelope of the absolute value of the density, in most cases, decays exponentially. We have fitted these envelopes to a decaying exponential function, $|n| \exp{(-B x)}$, from which we are able to calculate the decay length as 1/B. For those shocks without sufficient data points (3 or more) necessary to do an exponential fit, we defined the decay length to be the length it takes for the density to fall to 1/e of the y-intercept on our plots, where the x = 0 value is arbitrary. At all 71 shocks we also estimate the overshoot/undershoot wavelength using the zero-crossings of the density profile. Comparing the average wavelength to the ion gyro radius $v_{sh}/\Omega_{ci}$, we find that there is a good correlation between the two: $\lambda \approx$ 2.64 $v_{sh}/\Omega_{ci}$. We also find the wavelength to be $\lambda \approx$ 2.81 $c/\omega_{pi}$ ion inertial lengths, although this correlation is not as strong. We attempt to parameterize the scales with solar wind Mach number and plasma $\beta$.
DE: 2139 Interplanetary shocks
DE: 2154 Planetary bow shocks
DE: 7851 Shock waves
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting