Journal cover Journal topic
Annales Geophysicae An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 1.621 IF 1.621
  • IF 5-year value: 1.614 IF 5-year 1.614
  • CiteScore value: 1.61 CiteScore 1.61
  • SNIP value: 0.900 SNIP 0.900
  • SJR value: 0.910 SJR 0.910
  • IPP value: 1.58 IPP 1.58
  • h5-index value: 24 h5-index 24
  • Scimago H index value: 80 Scimago H index 80
Volume 17, issue 12
Ann. Geophys., 17, 1528-1534, 1999
https://doi.org/10.1007/s00585-999-1528-9
© European Geosciences Union 1999

Special issue: Equator S

Ann. Geophys., 17, 1528-1534, 1999
https://doi.org/10.1007/s00585-999-1528-9
© European Geosciences Union 1999

  31 Dec 1999

31 Dec 1999

Waveform and packet structure of lion roars

W. Baumjohann1, R. A. Treumann1, E. Georgescu1,2, G. Haerendel1, K.-H. Fornacon3, and U. Auster3 W. Baumjohann et al.
  • 1Max-Planck-Institut für extraterrestrische Physik, Garching, Germany
  • 2Institut for Space Sciences, Bucharest, Romania
  • 3Institut für Geophysik und Meteorologie, TU Braunschweig, Germany

Abstract. The Equator-S magnetometer is very sensitive and has a sampling rate of normally 128 Hz. The high sampling rate allows for the first time fluxgate magnetometer measurements of ELF waves between the ion cyclotron and the lower hybrid frequencies in the equatorial dayside magnetosheath. The so-called lion roars, typically seen by the Equator-S magnetometer at the bottom of the magnetic troughs of magnetosheath mirror waves, are near-monochromatic packets of electron whistler waves lasting for a few wave cycles only, typically 0.25 s. They are right-hand circularly polarized waves with typical amplitudes of 0.5–1 nT at around one tenth of the electron gyrofrequency. The cone angle between wave vector and ambient field is usually smaller than 1.5°.

Key words. Interplanetary physics (MHD waves and turbulence; plasma waves and turbulence)

Publications Copernicus
Special issue
Download
Citation
Share