ESA Science & Technology - NTC radiation measured by WHISPER

Frequency-time spectrograms showing continuum emissions measured by the Whisper instrument on three different days. The two upper panels display natural emissions only, while the lower panel also includes the resonance spectral harmonic lines induced during sounding operations.

Continuum radiations appear under different forms:

07 June 2003

• As a series of narrow frequency elements, penetrating the magnetosheath

25 July 2002

• As a continuum enhancement, starting simultaneously with auroral radiations signatures, both likely resulting from the same triggering due to particle injection and precipitation

23 October 2002

• Above 40 kHz, as structured emissions localized near the magnetic equator
• Between 30 and 50 kHz, as narrow frequency continuum elements
• At low frequency, as a smooth large band emission, trapped in between the plasmaspheric body and a density blob