Radial variation of whistler-mode chorus:first results from the STAFF/DWP instrument onboard the Double Star TC 1 Spacecraft

• Published in: Annales geophysicae (1988) Vol. 23; no. 8; pp. 2937 - 2942
• Main Authors: Santolik, O., Macúšová, E., Yearby, K. H., Cornilleau-Wehrlin, Nicole, Alleyne, H. Stc. K.
• Format: Journal Article
• Language: English
• Published: European Geosciences Union 2005
• Subjects: Astrophysics; Cosmology and Extra-Galactic Astrophysics; Physics; Sciences of the Universe
• ISSN: 0992-7689; 1432-0576
• DOI: 10.5194/angeo-23-2937-2005

We use the first measurements of the STAFF/DWP instrument on the Double Star TC-1 spacecraft to investigate whistler-mode chorus. We present initial results of a systematic study on radial variation of dawn chorus. The chorus events show an increased intensity at L parameter above 6. This is important for the possible explanation of intensifications of chorus, which were previously observed closer to the Earth at higher latitudes. Our results also indicate that the upper band of chorus at frequencies above one-half of the electron cyclotron frequency disappears for L above 8. The lower band of chorus is observed at frequencies below 0.4 of the electron cyclotron frequency up to L of 11-12. The maxima of the chorus power spectra are found at slightly lower frequencies compared to previous studies. We do not observe any distinct evolution of the position of the chorus frequency band as a function of L. More data of the TC-1 spacecraft are needed to verify these initial results and to increase the MLT coverage.