The occurrence and wave properties of H+-, He+-, and O+-band EMIC waves observed by the Van Allen Probes

• Published in: Journal of geophysical research. Space physics Vol. 120; no. 9; pp. 7477 - 7492
• Main Authors: Saikin, A. A., Zhang, J.-C., Allen, R. C., Smith, C. W., Kistler, L. M., Spence, H. E., Torbert, R. B., Kletzing, C. A., Jordanova, V. K.
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 01-09-2015; American Geophysical Union
• Subjects: band separation; EMIC waves; Fast Fourier Transform; GEOSCIENCES; Magnetic fields; Probes; Spatial distribution; Van Allen Probes; Wave power
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1002/2015JA021358

We perform a statistical study of electromagnetic ion cyclotron (EMIC) waves detected by the Van Allen Probes mission to investigate the spatial distribution of their occurrence, wave power, ellipticity, and normal angle. The Van Allen Probes have been used which allow us to explore the inner magnetosphere (1.1 to 5.8 RE). Magnetic field measurements from the Electric and Magnetic Field Instrument Suite and Integrated Science on board the Van Allen Probes are used to identify EMIC wave events for the first 22 months of the mission operation (8 September 2012 to 30 June 2014). EMIC waves are examined in H+, He+, and O+ bands. Over 700 EMIC wave events have been identified over the three different wave bands (265 H+‐band events, 438 He+‐band events, and 68 O+‐band events). EMIC wave events are observed between L = 2–8, with over 140 EMIC wave events observed below L = 4. Results show that H+‐band EMIC waves have two peak magnetic local time (MLT) occurrence regions: prenoon (09:00 < MLT ≤ 12:00) and afternoon (15:00 < MLT ≤ 17:00) sectors. He+‐band EMIC waves feature an overall stronger dayside occurrence. O+‐band EMIC waves have one peak region located in the morning sector at lower L shells (L < 4). He+‐band EMIC waves average the highest wave power overall (>0.1 nT2/Hz), especially in the afternoon sector. Ellipticity observations reveal that linearly polarized EMIC waves dominate in lower L shells.
Key Points
A statistical study of EMIC waves observed by the Van Allen Probes is performed
The occurrence and wave properties of the EMIC waves are examined
Linearly polarized EMIC waves dominate lower L shells (L < 4)