Physics of Plasmas in a Dipole Field

  • Hasegawa A.

Dipole field is the most elementary structure of a magnetic field, yet the behavior of a plasma in a dipole magnetic field is very interesting both from the point of view of a single particle motion and of a collective fluid motion. In particular when a stochastic motion and diffusion in psi-phi space is induced by RF fields at omega~mphi the plasma particles are expected to have an ambipolar diffusion toward the center of the dipole and simultaneously be heated by J and mu considerations. Here mu, J and psi are the first (the magnetic moment), the second (action of the bounce motion) and the third (magnetic flux) invariants, phi is the conjugate angle of psi and m is the azimuthal mode number of the RF. As a consequence, one can produce a confined plasma with the pressure p(r) ~r sup (-20) /3 and density n(r)~r sup (-4) using a low density and low temperature source at an outer edge of the dipole field. The plasma thus produced is marginally stable with respect to an interchange because partial f / partial psi|sub mu, J=0. Furthermore, the fact that most plasmas are "trapped" leads to almost a perfect cancellation of the driving term of the ballooning instability by the trapped particle contribution and to a stability (with respect to the ballooning) to beta>>1.

Recent Publications

August 09, 2017

A Cloud Native Approach to 5G Network Slicing

  • Francini A.
  • Miller R.
  • Sharma S.

5G networks will have to support a set of very diverse and often extreme requirements. Network slicing offers an effective way to unlock the full potential of 5G networks and meet those requirements on a shared network infrastructure. This paper presents a cloud native approach to network slicing. The cloud ...

August 01, 2017

Modeling and simulation of RSOA with a dual-electrode configuration

  • De Valicourt G.
  • Liu Z.
  • Violas M.
  • Wang H.
  • Wu Q.

Based on the physical model of a bulk reflective semiconductor optical amplifier (RSOA) used as a modulator in radio over fiber (RoF) links, the distributions of carrier density, signal photon density, and amplified spontaneous emission photon density are demonstrated. One of limits in the use of RSOA is the lower ...

July 12, 2017

PrivApprox: Privacy-Preserving Stream Analytics

  • Chen R.
  • Christof Fetzer
  • Le D.
  • Martin Beck
  • Pramod Bhatotia
  • Thorsten Strufe

How to preserve users' privacy while supporting high-utility analytics for low-latency stream processing? To answer this question: we describe the design, implementation and evaluation of PRIVAPPROX, a data analytics system for privacy-preserving stream processing. PRIVAPPROX provides three properties: (i) Privacy: zero-knowledge privacy (ezk) guarantees for users, a privacy bound tighter ...