Transcript Document
Escaping ions over polar cap Inner magnetosphere, Bow shock/Foreshock, and Ancient magnetosphere Why? (1) Why do we research escape (2) Why do we research heating/energization (3) Why do we research Inner magnetosphere (low energy ions) (4) Why do we research bow shock / foreshock (5) Why do we research aurora (a) We are looking at phenomena that observations are not easily predicted by theories, and therefore are basic processes of plasma that needs to be understood (b) Inter-comparison between Earth-Venus-Mars = (1) and (4) (c) RBSP mission will intensify world-wide study = (2) and (3) (d) We are under aurora with ground-based facility = (2) and (5) Inner magnetosphere Inner magnetosphere (Cluster observation): * We found cold source in addition to hot source energy in the tail (finished) * We found ionosphere source in addition to tail source (need 0.5 manyear) * We found equatorially-confined ions (need 1 man-year, on-going) * We derived the velocity of the drift from (need 0.5 man-year) * We found mass-dependent drift of energetic ions that no theory has predicted (need 1 man-year) * We found that some aurora is related to solitary structure in the inner magnetosphere (need 1 man-year). * We plan to study north-south asymmetric cases (need 1 man-year, on-going) * We plan to study contamination effect of the radiation belt particles (need 1 man-year) Sub-to several-keV ion patterns in the inner magnetosphere (near perigee of Cluster) Viking eastward drift 14 MLT poleward westward drift Cluster Perigee, 11 MLT eastward drift 6 MLT 9 MLT Statistics: fossil of substorm (1) Moves eastward (2) Decrease in time for both probability and energy 12 MLT 15 MLT 18 MLT Time-lag (hours) (Yamauchi and Lundin, 2006) Further classification by two populations Peak AE during latest 6 hours vs Pattern in spectrogram Pattern in Spectrogram Peak AE (a) (b) (c) (d) < 300 nT 0 4 26 10 300~500 nT 0 8 17 1 > 500 nT 5 33 3 4 finding out source Warm (1 keV, 0.5/cc) Back-trace to 8 Re and Forward simulation Observation Cold (0.2~0.6/cc) +1° H+ S/C-1 Yes 0° -1° -2° No 23:40-24:00 UT O+ S/C-4Yes H+ H+ No S/C-3 O+ No O+ ? Relative S/C position: all at 9.0±0.1 MLT ions > 5000 km/s 1000~2000 km ions ≈ 3000 km/s P/A keV E P/A 06:42 06:44 IMAGE (FUV) 06:46 06:48 Equatorial trapped 100 eV H+ (1) Trapped (pitch angle ~ 90°) and confined to Equator (2) nearly 50% in the noon and dusk sectors, and 35% in night-dawn. (3) Variable content of He+. (majority is less than 5%) (4) Variable energy ratio between He+ and H+ (1 to 4), contrasting to the previous report. (5) Time scale of about an hour. Modeling Ancient magnetosphere/ionosphere Prognosis of O/H ratio of atmospheric escape from non-magnetized Ancient Earth Increase in Jeans & Photochemical (H, He) EUV/FUV SWDP IMF (IMF) SEP ++ same same same + same same same + + same + same + same (cf. Earth) + ++ Hydrodynamic (all) ++ (regime change) Ion pick-up (H, He) Wave and E// (all) Momentum transfer (all) O/H ratio of escape (#1) ++ (cf. Earth) ++ + same ++ same + (#2) + same + + #1) depending on relative extent of ionosphere and exosphere #2) because non-thermal > thermal for Earth-sized planet Mars-Venus-Earth difference 2: Bow shock and foreshock * Planetary size matters, Earth ≈ Venus ≠ Mars (no foreshock) because of (1) Gyroradius ≈ bow shock size for Mars (2) Extended exosphere due to low gravity produces cold ions at bow shock (3) This makes Mars an ideal laboratory to study micro-scale physics, i.e., ion motion. For example, we need new classification of shock. * Future plan (3-5 years) (1) bow shock reflection statistics (He++/H+ ratio etc) (2) comparison with cold ion Venus-Mars difference (1) size: finite gyroradius effect c/pi ( n-1/2) rg ( V/B) & c/piRS & rg/RS Venus RS (BS MA radius) (n1/2 V/B) 1 1 1& 1 1& 1 Earth ~5 ~ 1.2 ~ 1.7 & ~ 0.3 ~ 2 & ~ 0.4 Mars ~ 0.5 ~ 1.4 ~3& ~5 ~4&~8 SW parameter For Mars: RS ~ 5000 km for Martian Subsolar 2 keV H+ under 6 nT rg = 1000 km 5/cm3 H+ c/pi = 100 km (2) cold ions: only Mars has cold ion at bow shock Foreshock (Venus/Earth=yes, Mars=no) Martian specialty on Bow shock acceleration QT oblique acceleration QT ^ acceleration QL FS ^ & // acceleration escape // accelera escape on-going works old works Foreshock: He++ and H+ show different behavior inbound-outbound asymmetry: Quick ExB drift Heating event Freja O+ injections O+ = not well-studied H+ = wellstudied in 1° x 1h bin.