First observations of 4fceauroral roar emissions

摘要: [1] This is a report on the first observations of auroral roar emissions near 4 times ionospheric electron cyclotron frequency (fce) with passive receiver installed in Svalbard, Norway. 4fce were detected from 5.27 to 5.70 MHz during moderate geomagnetic disturbances 22 days between May and September 2011 only noon evening, while no event occurred winter season. An analysis typical shows that density profile measured EISCAT Svalbard dynasonde satisfies condition upper nearly equal both hybrid resonance (fUH) at 238-km altitude. These support idea expanded most commonly-accepted generation mechanism 2fce 3fce roar: origin waves favorably generated under fUH ∼ F-region ionosphere.