1 / 32

STP seminar August 26, 2009 Masaki N. Nishino * 1

Two mechanisms of solar-wind proton entry deep into the near-Moon wake revealed by SELENE (KAGUYA). STP seminar August 26, 2009 Masaki N. Nishino * 1

ravi
Download Presentation

STP seminar August 26, 2009 Masaki N. Nishino * 1

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Two mechanisms of solar-wind proton entrydeep into the near-Moon wake revealed by SELENE (KAGUYA) STP seminar August 26, 2009 Masaki N. Nishino*1 Collaborators: Masaki Fujimoto1, Kiyoshi Maezawa1, Yoshifumi Saito1, Shoichiro Yokota1, Kazushi Asamura1, Takaaki Tanaka1, Hideo Tsunakawa2, Hidetoshi Shibuya3, Masaki Matsushima2, Hisayoshi Shimizu4, Futoshi Takahashi2, and Toshio Terasawa2 ISAS/JAXA, (2) TITECH, (3) Kumamoto Univ., (4) ERI, Univ of Tokyo

  2. Outline • Introduction • SELENE spacecraft & instruments • Proton reflection at the dayside surface (Saito et al. GRL, 2008) • Type-1 entry (Nishino et al. GRL, 2009) • Type-2 entry (Nishino et al. GRL, in press) • Summary

  3. More than 80 % of time ... • The moon stays in the solar wind • interaction btwn SW and the Moon • Why important ? • Wake formation behind the moon • Particle/dust acceleration • Hazardous in future missions • Space plasma and planetary surface • no thick atmosphere • no intrinsic magnetic field

  4. A traditional view of the lunar wake • Electron-rich • high thermal speed of e- • generation of E field • Gradual acceleration of SW ions • No solar wind ions E E How do ions behave in the near-Moon wake ?

  5. Wind and SELENE Comparison of wake observations by Wind and SELENE

  6. Outline • Introduction • SELENE spacecraft & instruments • Proton reflection at the dayside surface • Type-1 entry • Type-2 entry • Summary

  7. SELENE (Kaguya) spacecraft • Launch • on Sept. 14, 2007 • Orbit • polar orbit • 2-hour period • 3-axis stabilized • Plasma measurement • Ions (composition) • Electrons • Magnetic fields • Waves

  8. MAP (PACE+LMAG) onboard SELENE (Kaguya) Orbit • 2-h period • polar orbit • 100 km alt. MAP-PACE • electrons x2 • ions x2 • each 2 str. FOV MAP-LMAG • magnetic field • 32 Hz MAP measures the near-Moon plasma environment comprehensively.

  9. Outline • Introduction • SELENE spacecraft & instruments • Proton reflection at the dayside surface • Type-1 entry • Type-2 entry • Summary

  10. Solar-wind proton reflection at the dayside surface protons reflected/scattered at the dayside surface

  11. Outline • Introduction • SELENE spacecraft & instruments • Proton reflection at the dayside surface • Type-1 entry • Observation • Model calculations • Type-2 entry • Summary

  12. Ion energy gain& loss at wake boundary (1) down e- SP: acceleration NP: deceleration up e- down ion up ion gain loss gain loss day SP wake NP day SP wake NP

  13. Ion energy gain& loss at wake boundary (1) SP: acceleration NP: deceleration gain loss gain loss

  14. Ion energy gain& loss at wake boundary (1) SP: acceleration NP: deceleration gain loss gain loss

  15. Ion energy gain& loss at wake boundary (1) SP: acceleration NP: deceleration gain loss gain loss

  16. Ion energy gain& loss at wake boundary (1) SP: acceleration NP: deceleration gain loss gain loss

  17. Ion energy gain& loss at wake boundary (1) SP: acceleration NP: deceleration gain loss gain loss

  18. Dependence on SW magnetic field By Implication of particle dynamics SP: gain NP: loss By>0 SP: loss NP: gain By<0 no energy gain nor loss small By

  19. Outline • Introduction • SELENE spacecraft & instruments • Type-1 entry • Observation • Model calculations • Type-2 entry • Summary

  20. Larmor phase filtering effect ? Wake E field ? E Vx decreases Vx increases E

  21. Wake E-field model How does this simple E field change the SW proton energy ?

  22. Model calculations : SW proton intrusion no energy change (a) No E field • no acceleration • cutoff due to thermal motion (b) with E field • energy gain & loss energy gain energy loss wake potential 300 eV, (width Rm/4, E ~ 0.7 mV/m) • SW • By=4 nT • Vsw=350 km/s • Vth=35 km/s observed ions

  23. Model calculations : SW proton intrusion Trajectory of SW protons • intrusion to mid- and low-latitude region • Energy in the rest frame • gain and loss • Energy in the SW frame • gain (as much as wake potential) bulk: Vsw=350 km/s, Larmor: v=70 km/s

  24. Summary of Type-1 entry Solar wind protonscan easily access to the lunar night side. Before SELENE Now with SELENE Complicated plasma environment We are now constructing a new model.

  25. Outline • Introduction • SELENE spacecraft & instruments • Proton reflection at the dayside surface • Type-1 entry • Type-2 entry • Observation • Model calculation • Summary

  26. Ion found in the deepest wake 2 kinds of wake ? • almost vacuum • plasma entry

  27. Proton entry into the deepest wake Proton sneaking into the deepest wake (from dayside ?) Accompanied by bi-streaming e- By-dominant IMF SZA 168 deg 100 km height

  28. Obliquely-going protons are detected by IMA Protons turn upward just near the nightside surface E-t scatter plot along virtual spacecraft orbit g E-t scatter plot along the virtual spacecraft orbit scatter location : every 5 degrees in the dayside region of Lon. and Lat. -70~+70 deg) scatter angle : every 2 degrees

  29. Validity of our model of Type-II entry Similar patterns related to Type-II entry are reproduced.

  30. Formation of PGR (proton-governed region) • Scattered protons sneak into one hemisphere on the nightside • formation of PGR • Generation of outward E field around PGR • PGR absorbs ambient electrons along the IMF • counter-streaming electrons are found in the PGR

  31. Wind and SELENE Comparison of wake observations by Wind and SELENE

  32. References • Ogilvie et al. GRL 1996 • Halekas et al. JGR 2005 • Saito et al. GRL 2008 • Nishino et al. GRL 2009a • Nishino et al. GRL 2009b

More Related