Sources of plasma in the high altitude cusp

• Published in: Journal of atmospheric and solar-terrestrial physics 2012-10, Vol.87-88, p.1-10
• Main Authors: Peterson, W.K., Trattner, K.J.
• Format: Article
• Language: English
• Subjects: Boundary layer; Boundary layer plasmas; Cusps; Energetic ions; High altitude; High altitude cusp; Holes; Intervals; Ionospherics; Plasma (physics); Plasma energization
• ISSN: 1364-6826; 1879-1824
• DOI: 10.1016/j.jastp.2011.07.001

Ambiguities introduced by the inconsistent definitions of the low and high altitude cusp lead to the inconsistency that at low altitudes the region commonly known as the cusp does not include boundary layer plasmas, but at high altitudes it does. Here we examine plasma data from two high altitude cusp intervals where ∼100keV ionospheric ions were observed. We show that the data are an average over an interval that includes plasma from both boundary layer and newly injected solar wind plasmas. We find that the ∼100keV ionospheric ions reported in the high altitude cusp are energized by well-known magnetospheric processes bringing energetic ions to the dayside boundary layers. We conclude that there is no need to postulate new processes associated with waves in diamagnetic cavities commonly found in the high altitude cusp to explain the observation of ∼100keV ionospheric ions found there. ► Cusp identification methods are inconsistent. ► Ionospheric investigators do not include boundary layer plasmas in the cusp. ► Magnetospheric investigators include boundary layer plasmas in the cusp. ► Boundary layer plasmas often include O+ and He+ with 100keV energies. ► There is no need for a new acceleration mechanism to explain 100keV ionospheric ions in the high altitude cusp.