Global images of trapped ring current ions during main phase of 17 March 2015 geomagnetic storm as observed by TWINS. Issue 7 (19th July 2016)

• Record Type: Journal Article
• Authors: Perez, J. D.; Goldstein, J.; McComas, D. J.; Valek, P.; Fok, M.‐C.; Hwang, Kyoung‐Joo
• Is Part Of: Journal of geophysical research. Volume 121:Issue 7(2016:Jul.)
• Page Start: 6509
• Page End: 6525
• Publication Date: 2016-07-19
• Subjects: ring current -- TWINS -- RBSPICE; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA022375
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: A unique view of the trapped particles in the inner magnetosphere provided by energetic neutral atom (ENA) imaging is used to observe the dynamics of the spatial structure and the pitch angle anisotropy on a global scale during the last 6 h of the main phase of a large geomagnetic storm (minimum SYM‐H = −230 nT) that began on 17 March 2015. Ion flux and pressure anisotropy obtained from Two Wide‐angle Imaging Neutral‐atom Spectrometers (TWINS) ENA images are shown. The ion flux shows two peaks, an inner one at approximately radii = 3–4 RE in the dusk‐to‐midnight sector and an outer peak at radii = 8–9 RE prior to midnight. The inner peak is relatively stationary during the entire period with some intensification during the final steep decline in SYM‐H to its minimum. The outer peak shows the significant temporal variation brightening and dimming and finally disappearing at the end of the main phase. The pressure anisotropy shows the expected perpendicular pitch angles inside of L = 6 but shows parallel pitch angles at greater L values. This is interpreted as consistent with pitch angle‐dependent drift as modeled in the Tsy05 magnetic field and Comprehensive Inner Magnetosphere‐Ionosphere simulations. The TWINS results are compared directly with Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE)‐A measurements. Using 15 min snapshots of flux and pressure anisotropy from TWINS along the path of RBSPICE‐A during the 6 h focused upon in this study, the essential features displayed in the TWINS global images are supported. Key Points: Ion flux in trapped ring current during main phase of large storm shows multiple peaks Pressure anisotropy tends toward parallel at large radii The TWINS ion images are compared directly with RBSPICE‐A in situ measurements