Wave particle interactions in reconnection regions

Many space phenomena cause very strong electron heating, but the mechanisms are often either unknown, or not well understood. An example is the magnetic reconnection which occurs in solar flares (shown in the top figure) or in the earth's magnetosphere: a large proportion of the energy is released in the form of semirelativistic electron beams and heated plasma. One type of process which can produce electron acceleration is resonant wave-particle interaction:

Waves in the plasma are driven by spatial variations (e.g. in the magnetic field) or unstable particle distributions.
These waves interact stochastically with electrons, increasing the average electron energy and changing the particle distribution function.

We are investigating this mechanism in various plasma configurations, comparing the results of observations and computationally intensive particle simulations against simple analytical results and quasilinear models (the lower figure shows the result of one such calculation).

Where these simplified models are valid, they allow considerable insight into the physical processes at work. These models also yield predictions in regimes where direct simulation is computationally infeasible.

Key References:

Cairns, I. H., 2001, "Lower Hybrid Drive in Solar Magnetic Reconnection Regions: Implications for Electron Acceleration and Solar Heating", Publications of the Astronomical Society of Australia, 18, 336-344

Cairns, I. H., 2005, "Electron Acceleration by Lower Hybrid Waves in Magnetic Reconnection Regions", Submitted to Physical Review E

Figure 1. Magnetic field loops on the sun are heated during a solar flare (see bright yellow region) near the sun's limb. Data is from NASA's TRACE spacecraft.

Figure 2. An ion beam interacts with low phase-speed waves, and begins to form a ring-like distribution.

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