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Ring Current in Solar Minimum: TWINS Observations

Ring Current in Solar Minimum: TWINS Observations. M. Fok 1 , N. Buzulukova 1 , D. McComas 2 , J. Goldstein 2 1 NASA Goddard Space Flight Center 2 Southwest Research Institute. 2009 GEM Workshop June 21 - 26 Snowmass, Colorado. The TWINS Mission.

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Ring Current in Solar Minimum: TWINS Observations

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  1. Ring Current in Solar Minimum: TWINS Observations M. Fok1, N. Buzulukova1, D. McComas2, J. Goldstein2 1NASA Goddard Space Flight Center 2Southwest Research Institute 2009 GEM Workshop June 21 - 26 Snowmass, Colorado

  2. The TWINS Mission Two Wide-angle Imaging Neutral-atom Spectrometers First Stereoscopic Magnetospheric Imaging Mission TWINS proposed in 1997, MoO (AO 97-OSS-03) 2 nadir-viewing Molniya-orbit spacecraft 7.2 RE apogee, 63.4˚ inclination, 12 hour orbit Actuator replaced S/C spinning Stero Imaging began in summer of 2008 Available at http://twins.swri.edu TWINS Team: PI: Dave McComas (SwRI) Project Scientist: Mei-Ching Fok (NASA) Program Scientist: Barbara Giles (NASA) Science Analysis Lead: Jerry Goldstein (SwRI)

  3. 11 October 2008 moderate storm (Dst/SYMH ~ -60nT) TWINS data

  4. 1 2 3 4 5 11 October 2008 Early Main Phase: Ring Current Buildup TWINS 2: ENA intensity; E = 12 keV Linear scale 0.0-0.5 (cm2 sr s eV)-1 (1) 07:20-07:30 UT (2) 07:50-08:10 UT (3) 08:20-08:40 UT RCE LAE LAE sunlight (4) 08:50-09:10 UT (5) 09:20-09:40 UT AU RCE AL RCE SYMH LAE LAE

  5. 11 October 2008 Middle of the Main Phase TWINS 1 and TWINS 2 stereoscopic observations 12 keV 09:50-10:10 UT 10:20-10:40 UT TWINS 1 RCE RCE sunlight RCE RCE LAE LAE TWINS 2 1 2 3 Linear scale 0.0-0.5 (cm2 sr s eV)-1

  6. CRCM main drivers: convection and plasma sheet parameters Weimer-2000 cross polar cap potential PS temperature Temperature and density at polar boundary from Tsyganenko&Mukai-2003 PS model, Rb=10 RE (different colors correspond 00 MLT, 03/21 MLT, 06/18 MLT)‏ PS density

  7. SYMH* index and Ring Current Pressure red – CRCM (Dessler-Parker-Scopke)‏ green – WDCG, Kyoto + correction 06:30 10:00 16:30 19:30 Correction to SYMH: SYMH* = SYMH/1.3 – 0.2p1/2 + 20 (nT) ; p – SW pressure (eV cm-3)‏ (Burton et al., 1975; Gonzalez et al., 1994; Kozyra et al., 2002)‏

  8. 07:30 UT 09:30 UT 10:00 UT TWINS1 Max = 0.5 Max=0.5 Max=0.5 CRCM ENA Max = 0.8 Max=0.8 Max=0.8 CRCM H+ flux TWINS 1 – CRCM Data-model comparison: ring current buildup (12 keV H+)‏

  9. 12 keV H+ flux Total RC pressure TWINS 1 / TWINS 2 - CRCM Data-model comparison: stereoscopic view (12 keV) at ~10:30 UT (main phase)‏ TWINS 1 TWINS 2 Max = 0.5 Max = 0.5 CRCM ENA Max = 0.8 Max = 0.8

  10. 12 August 2000 storm: Dst/SYMH(min) ~ -250 nT AL(min) ~ - 2000 nT 11 October 2000 storm: Dst/SYMH(min) ~ -60 nT AL(min) ~ - 800 nT

  11. Solar wind / IMF conditions: n, V,Bz, By 12 August 2000 11 October 2008

  12. Weimer-2000 cross polar cap potential: CRCM input 12 August 2000 11 October 2008

  13. CRCM H+ flux 12 August 2000 11 October 2008 10-15 keV 25-38 keV 60-120 keV

  14. CRCM TOTAL H+ PRESSURE (1-180 keV) 12 August 2000 storm main phase 11 October 2008 storm main phase

  15. Summary • Moderate ring current seen by TWINS • CRCM shows good spatial agreement with TWINS • ENA peak at post-midnight, Ion pressure peak at pre-midnight • Convection is a key factor determining storm size • Large storm  deeper ion penetration  strong pressure • Large storm  stronger J||  stronger eastward skewing

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