Whistler Waves as a Signature of Converging Magnetic Holes in Space Plasmas

Magnetic holes are plasma structures that trap a large number of particles in magnetic field is weaker than the its surroundings. The unprecedented high time-resolution observations by NASA's Magnetospheric Multi-Scale (MMS) mission enable us to study particle dynamics Earth's magnetosheath great detail. We reveal local generation mechanism whistler waves combination Landau-resonant and cyclotron-resonant wave-particle interactions electrons response large-scale evolution hole. As hole converges, pair counter-streaming electron beams form near hole's center as consequence combined action betatron Fermi effects. trigger slightly-oblique waves. Our conceptual prediction supported remarkable agreement between our numerical predictions from Arbitrary Linear Plasma Solver (ALPS). shows fundamental space astrophysical plasmas.