Abstract: The data of meridian scanning photometer and EISCAT Svalbard Radar on Jan 22 2004 are analyzed, and the results shows that naturally enhanced ion acoustic lines of incoherent scatter spectra in the vicinity of the red auroral forms. The meridian scanning photometer observations from Longyearbyen near ESR site shows red auroral emission from 4 to 32 kR. The value of the emission density is more than 15 kR when naturally enhanced ion acoustic lines happen. There exists the good correlation of particle precipitation and naturally enhanced ion acoustic lines. According to the field-aligned current model, the data of the naturally enhanced ion acoustic lines are analyzed. The field-aligned current density are obtained by reversion, the magnitude of the values is to mAm^-2. The values of the field-aligned current density become small based on the modified field-aligned current model due to introducing the term of the field-aligned heat flow.