Equatorial Noise With Quasiperiodic Modulation: Multipoint Observations by the Van Allen Probes Spacecraft. Issue 6 (16th June 2018)

• Record Type: Journal Article
• Authors: Němec, F.; Santolík, O.; Boardsen, S. A.; Hospodarsky, G. B.; Kurth, W. S.
• Is Part Of: Journal of geophysical research. Volume 123:Issue 6(2018)
• Page Start: 4809
• Page End: 4819
• Publication Date: 2018-06-16
• Subjects: equatorial noise -- quasiperiodic modulation -- Van Allen Probes -- RBSP; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2018JA025482
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Electromagnetic wave measurements performed by the two Van Allen Probes spacecraft are used to analyze equatorial noise emissions with a quasiperiodic modulation of the wave intensity. These waves are confined to the vicinity of the geomagnetic equator, and they occur primarily on the dayside. In situ plasma number density measurements are used to evaluate density variations related to the wave occurrence. It is shown that the events are sometimes effectively confined to low‐density regions, being observed at successive satellite passes over a time duration as long as 1 hr. The events typically occur outside the plasmasphere, and they often cease to exist just at the plasmapause. The analysis of the spatial separations of the spacecraft at the times when the events were observed simultaneously by both of them allows us to estimate the event spatial dimensions. It is found that the event spatial extent is typically lower than about 0.25 R E in radial distance and within about 1 hr in magnetic local time. Modulation periods of the events decrease with increasing plasma number density up to about 100 cm −3 . Principally no dependence is observed at larger densities, possibly indicating a propagation from other locations. Key Points: EN events with the QP modulation are sometimes confined to low‐density regions The events typically occur just outside the plasmasphere Multispacecraft observations allow us to estimate the spatial dimensions of the events