Interstellar Medium V1

Transcription

1 Interstellar Medium V1 Heliosheath Termina/on Shock V2

2 which can be used to distinguish spatial and temporal effects. The V2 flows derived from the energetic particles using the Compton-Getting effect will be compared Why with the the measured speeds plasma speeds at to Voyager see if these flows 1 and 2 are so different? become decoupled. - a - ] e e ]. - - Figure 7: Plasma velocity components in the heliosheath. Voyager 1 Voyager 2 6

3 What happened to the missing azimuthal magne/c flux at Voyager 1? Expect corresponding increase in magne/c field Voyager 2 Conserva/on of magne/c flux: B T V R R = constant Voyager 1 However, while VR was decreasing B was constant <B> = 0.1 Richardson et al. 2013

4 HP The outer heliosheath inside the sector region is filled bubble - like structures of magne/c field- the bubbles are convected to higher la/tudes by the heliosheath flows flows Opher et al. ApJ 2011

5 Old and a New View: The permeable heliosphere

6 Magnetized jets driven by the sun: The structure of the heliosphere revisited Merav Opher Boston University Jim Drake University of Maryland Bertalan Zieger Boston University Tamas Gombosi University of Michigan 6

7 Classical View of the Heliosphere: Comet-like shape with a long tail; extending to 1000 s of AUs e.g. from Parker 1961; Baranov & Malama 1993 This view comes from the assumption that even though the solar wind becomes subsonic at the termination shock as it flows down the tail is able to stretch the solar magnetic field. 7

8 Two-lobe structure heliosphere: similar to astrophysical jets Side view Nose view The heliopause is captured at the iso-surface of lnt=12.7; the gray lines are the solar magnetic field lines; the red lines are the interstellar magnetic field. 8

9 Turbulent Lobes (Jets) speed Everywhere downstream of the termination shock P ram /P B < 1 so the solar magnetic field is strong enough to confine the flow and resist being stretched by the downstream flow. Cut at y=150au 9

10 Turbulent Lobes (Jets) Density B The distance to the heliopause down the tail between the two lobes is 250AU (as opposed to 560AU in the case with no B ISM ). The lobes are eroded as a result of instabilities and reconnection in the flanks 10 Cut at y=150au

11 Porous Layered Heliopause Swisdak, Drake, Opher ApJL 2013

12 Fig. 1. Overview of energetic particle observations at V1, to , showing the contrary behavior of GCRs and lower-energy particles. (A) HourlyaveragesofGCRactivityandthepronounced boundary crossing on 25 August 2012 (day 238). GCR error bars are T1s.(B)Intensitiesoflow-tomediumenergy ions and low-energy electrons. The time evolution is very different,depending on energy and species. Krimigis et al. Science 2013

13 Is Voyager 1 s/ll inside the Heliosphere? Magne/c Field is Solar Like! A B C Fig. 2. High-resolution observations of the magnetic field strength and direction. 48-s averages of the magnetic field strength B (A), azimuthal angle l (B), and elevation angle d (C), as a function of time measured from DOY 150 to 270, The angles are in RTN coordinates (28). Before 210, 2012, V1 observed magnetic fields characteristic of the heliosheath (26). The elevation and azimuthal angles are close to the Parker spiral direction, d P 0 and l P 90 or 270, respectively. A magnetic sector in which B was directed sunward along the Parker spiral angle was observed between 171, 2012 and 208, The magnetic field strength varied from 0.07 to 3.36 nt before the boundary crossings. Burlaga et al. Science 2013

14 And then. Voyager 1 detected interstellar densi/es! Gurneg et al. Science 2013

15 Announcement that Voyager 1 is (since end of August 2012) in interstellar space Several people s/ll thinking that Voyager 1 is in the Heliosheath (e.g. Fisk & Gloeckler 2013; McComas & Schwadron 2012; Schwadron & McComas 2013).

16 HOW FAR THE HELIOSPHERE AFFECTS THE ISM? STRONG TWIST OF THE INTERSTELLAR MAGNETIC FIELD ahead of the Heliopause Opher & Drake ApJL, in press 2013