Morphology of Inner Magnetospheric low- energy ions M. Yamauchi 1, I. Dandouras 2, H. Reme 2, R. Lundin 3, L.M. Kister 4, F. Mazouz 5, Y. Ebihara 6 (1) Swedish Institute of Space Physics (IRF), Kiruna, Sweden (2) CNRS and U. Toulouse, IRAP, Toulouse, France (3) IRF, Umeå, Sweden (4) U. New Hampshire, Durham, NH, USA (5) IPSL/LATMOS, Paris, France (6) Kyoto University, Japan Cluster workshop 2013 A completed version of 2011 presentation

Ion drift Westward drift for high energy/evening and Eastward drift for low-energy/morning

Where? Inner Magnetosphere at 4~6 R E (Cluster perigee) Species? H + of 10 eV ~ 10 keV (CIS/CODIF energy range) Distribution? Intense ion population (except plasma sheet) In this work: (a) Statistics distribution, (b) 1-2 hour scale evolution/decay (using inbound-outbound asymmetry), and (c) relation to substorms (using elapsed time from high AE). We examined all SC-4 perigee pass during (about 670 traversals, with relatively clean data of 460 traversals). Analyses

(b) Wedge-like energy-latitude dispersed ions at sub-keV range: predominantly found in the morning sector some hours after a substorm. The source population is much colder than the plasma sheet. (c) Vertical stripes: similar to the wedge-like structure but dispersion is weak (nearly vertical in the spectrogram). The energy extends from the about 10 keV to sub-keV. (d) Short bursts of low-energy ions isolated from the above structures: a peak energy flux less than 100 eV but not thermal. (e) Internal asymmetry of (b) We examine ion signatures of

Before taking detailed analyses, we have to examine possible “biases” such as Instrument Degradation or Solar Cycle phase

Valid traversals for , , are 177, 115, 202, respectively.  rapid decrease is due to instrumental Decreasing trend in time (For warmed trapped ions, we cannot take statistics for because they are found high radiation dose region)

 Rapid degradation of the sensor Occurrence of substorms is rather constant  Is the trend due to some bias?

Not very much changed from to  We can safely use data together. Is Local Time distribution affected by this bias?

Local Time distribution symmetric + asymmetric enhanced within traversal

Relation to substorm? AL AU AL AU

eastward drift Viking 14 MLT poleward 6 MLT 9 MLT 12 MLT 15 MLT 18 MLT For the wedge-like dispersion, the relation to substorm has already been studied: After AE>400 nT activity, (1) Moves eastward (2) Decay in time cf. Viking hr from substorm

data Local Time distribution Relation to AE activities

The inner magnetospheric low-energy ion populations (1)-(3) below show significant changes within 1-2 hours. (1) Wedge-like energy-latitude dispersed ions (< a few keV), (2) Vertical stripes (< 10 keV), (3) Short-lived low-energy ion burst (< few hundred eV). For all three patterns, asymmetric cases (large inbound- outbound difference) are found more often than symmetric cases at almost all LT. For (2), majority of local midnight pass show large inbound- outbound difference when AL<300 nT. For (3), the lifetime is estimated as short as ≤ 1 hour Summary Yamauchi et al. (2013): Cluster observation of few-hour-scale evolution of structured plasma in the inner magnetosphere, Ann. Geophys., 31, , doi: /angeo , 2013.