(a) Typical LIF measured ivdf (filled circles) as a function of velocity in the expansion chamber for operating parameters that do not result in the formation of an ion beam. (b) LIF measured ivdf (circles) as a function of velocity in the expansion chamber 38 cm downstream of the plasma source. A three Maxwellian component fit (solid line) yields identical ion temperatures of ∼0.16 eV for all three components. (c) Same data as (b) minus the fit to the stationary background population. A very small third accelerated population appears around 2500 m/s.
Smoothed fits to LIF measured ivdfs for a single double layer case as a function of velocity in the expansion chamber at three different downstream locations for source parameters that result in the formation of only a single downstream ion beam population. Over more than 11 cm, there is no change in the velocity of the accelerated ion population.
The ion velocity distribution function along the outflow direction (reduced to one dimension by integrating over the over two velocity components) for a bursty bulk flow event on 26 February 2008 at (a) 11:12:52 and 3s later at (b) 11:12:55. A large background signal in the measurement at zero velocity due to photoemission and spacecraft charging has been deleted from the figure (the dashed line corresponds to the contaminated region ofthe distribution). Two accelerated ion populations appear in both measurements.
Ion velocity distribution (as a function of velocity normalized to the initial Alfvén velocity) along the outflow direction from a particle-in-cell numerical simulation of magnetic reconnection. The distribution is obtained 20 ion inertial lengths downstream of the reconnection site and is integrated over the other two coordinate directions. The ion velocity distribution includes two accelerated ion populations plus a stationary background population.
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