A statistical look at plasmaspheric drainage plumes

Abstract

[1] The properties of plasmaspheric drainage plumes are examined using cold-plasma measurements in geosynchronous orbit. During high-speed stream-driven storms, 210 plume crossings are collected and statistically analyzed. Plumes that persist for 4 days are common, which was the duration of our search. Plumes weaken with age, becoming narrower in local time with plasma that becomes less dense. Cold-plasma flow velocities are sunward in the plumes, with flow speeds decreasing as the storms progress. Plumes transfer typically 2 Â 10 26 ions/sec (1.2 ton/hr of protons) when they are young, and the rate of transport decreases with plume age. A total of approximately 2 Â 10 31 ions (34 tons of protons) are transported via plumes in the life of a storm. About half of the outer plasmasphere is drained in the first 20 hours of a storm. Large density fluctuations in the plumes indicate that the drainage plumes are lumpy, and large velocity fluctuations of the plasma flow indicate that the drainage plumes may be turbulent. Because of their persistence, drainage plumes are anticipated to be a regular feature of any ongoing geomagnetic storm.

Detection of a plasmaspheric wind in the Earth's magnetosphere by the Cluster spacecraft

“…The solar wind source is of the order of ∼ 10 27 ions s −1 and the high-latitude ionospheric source is of the order of ∼ 10 26 ions s −1 , varying by a factor of ∼ 3 as a function of the activity level and particularly dependent on the IMF orientation (Moore et al, 2005;Haaland et al, 2009;Li et al, 2012). The plasmaspheric plumes, which are a persistent feature during active periods, contribute during these periods by typically ∼ 2 × 10 26 ions s −1 to the magnetospheric populations (Borovsky and Denton, 2008). It appears thus that the plasmaspheric wind constitutes a substantial plasma source for the magnetosphere, outside the plasmasphere, which is comparable to the other sources and which operates continuously, even during prolonged periods of quiet geomagnetic conditions.…”

Multi-spacecraft observations of small-scale fluctuations in density and fields in plasmaspheric plumes

“…If the fluctuations reported here are measured where plumes are actually generated, this may be relevant to their suggestions. Another aspect is the turbulent nature of plumes, examined by Borovsky and Denton (2008). Although our study does not focus on this feature, further study on this topic would advance our understanding of the time evolution of plumes.…”

“…McFadden et al (2008) reported density fluctuations inside plumes measured by THEMIS (Time History of Events and their Macroscopic Interactions during Substorms) satellites. Borovsky and Denton (2008) examined density fluctuations and their relation to turbulence using LANL geosynchronous data.…”

Evidence for Nonlinear Development of Magnetohydrodynamic Scale Intermittency in the Inner Heliosphere

“…We discuss this further at the end of the paper. We will also argue that both our results and those of Bruno et al (2003) strongly favor the interpretation that the solar wind MHD scale cascade is active and not passive as sometimes suggested (Borovsky 2008). The present results also raise some interesting questions regarding the initial-boundary data for solar wind fluctuations.…”