PHOEBUS: Space Weather su LISA Helios Vocca

Transcription

1 PHOEBUS: Space Weather su LISA Helios Vocca 1

2 a GW primer. Gravitational force cannot propagate instantaneously It can only propagate at the speed of light Conclusions: Gravitational force propagates as waves travelling at the speed of light Only detectable effect for free falling observer is the tide (different force at different places) 2

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4 Gravitational Waves Predicted by Einstein 80 years ago Never detected with a man-made detector t P [s] Indirect evidence through energy loss of binary pulsar PSR (Hulse- Taylor) Einstein prediction 4

5 Gravitational Waves Very large energy, almost no interaction Ideal information carrier, almost no scattering or attenuation The whole Universe has been transparent for GWs, all the way back to the Big Bang 5

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9 LISA basics SourceGWFree falling testbodieslaser Ranging 9

10 Test Masses Telescopes Spacecrafts 3 pairs of free falling test masses ( ms -2 Hz 0.1 mhz) 3 test-mass follower shielding spacecraft 2 semi-independent km Michelson Interferometers with Laser Transponders km LISA Goal: GW at 0.1 mhz 0.1 Hz 10

11 LISA essentials 1: the smart orbits 11

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13 Angular Resolution with LISA Measurements on detected sources: - ~ 1 1 o - (mass,distance) 1% 13

14 LISA essentials 2: the laser transponding scheme Test mass km Phase-lock loop Laser Sensor Beating power loss due to beam divergence 14

15 LISA essential 3: Drag-free Achieving free fall against non-gravitational disturbances 15

16 LISA essential 3: Drag-free Achieving free fall against non-gravitational disturbances 16

17 Thrusters Drag-free: keeping the spacecraft with the proof-mass Spacecraft Displacement sensor Test mass x High gain force feedback 17

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27 The drag-free key elements: the displacement sensor injection electrode Ac amplifier Ac bias Test mass PSD 27

28 The drag-free key elements: the displacement sensor injection electrode Ac amplifier Ac bias Test mass PSD 28

29 The drag-free key elements: the displacement sensor injection electrode Ac amplifier Ac bias Test mass PSD & z & y z & x x y 29

30 Parasitic coupling The reality x Stray forces 30

31 Main disturbances to free-fall and design guidelines The residual test-mass acceleration noise {{{}{ o ce o spacec a tsc / p bse so o se a as t c st ess o c 31

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37 Spacecrafts 3 pairs of free falling test masses ( ms -2 Hz 0.1 mhz) Test Masses Can it be achieved? Telescopes km 37

38 LISA acceleration noise spectral density S 1/2 ( ) = s 2 m Hz 4mm gap V dc 10mV eff 300s 1 1/2 0.1mHz f Required acceleration noise limit for random charge: (m s -2 Hz -1/2 ) [total: ] ( Hz) 38

39 Proton fluxes 39

40 Simulation scheme Ti C Au Shape: cube Side: 4.6 cm Material: gold Thickness : 88.9 g/cm 2 Mo 40

41 Simulation materials Density Thickness Grammage (g/cm 3 ) (cm) (g/cm 2 ) Carbon Titanium Molybdenum Gold

42 Proton results: Source GCR at solar maximum Charge rate (e + /s) 15 Effective charge rate (e/s) 110 GCR at solar minimum Gradual Event Gradual Event Gradual Event Gradual Event Gradual Event Solar Flare peak flux

43 LISA acceleration noise spectral density Acceleration noise Effective charge rate spectral density Source 0.1mHz (m s -2 Hz -1/2 ) GCR at solar maximum GCR at solar minimum Gradual Event Gradual Event Gradual Event Gradual Event Gradual Event Solar Flare peak flux

44 Acceleration noise spectral density 44

45 LISA sensitivity 45

46 SOLAR WIND AND EARTH MAGNETOSPHERE Solar wind characterisitcs: 10 6 tons/s p,e km/s 6 part/cm 3 near Earth kev 46

47 INTERPLANETARY MAGNETIC FIELD SECTORS About 6 nt Earth moves +/-7.25 o latitude 47

48 Solar Energetic Particles (SEPs( SEPs) SEPs are particles above 1 MeV emitted by the Sun. They are mainly divided in two types of events: Impulsive and Gradual Impulsive* Gradual Particles Electron-rich Proton-rich 3He/4He ~1 ~ Fe/O ~1 ~0.1 H/He ~10 ~100 QFe ~20 ~14 Duration Hours Days Longitude Cone <30 deg ~180 deg Radio Type III, V (II) II, IV X-rays Impulsive Gradual Coronagraph - CME (96%) Solar Wind - IP Shock Events/year ~1000 ~10 * below 50 MeV Reames,, D V 1996, Energetic Particles from Solar Flares and Coronal Mass Ejections, in High Energy Solar Physics, Eds.. R Ramaty,, N Mandzhavidze,, X-M Hua, AIP Conf. Proc. 374, p35. 48

49 Gradual Events Solar energetic particles (SEPs) in gradual events are accelerated at a shock driven by a coronal mass ejection (CME) moving through the corona into the interplanetary medium. CME-driven shocks produce most of the large particle events at 1 AU and can accelerate protons up to 20 GeV. In large events the shock has been directly observed by spacecraft near 1 AU that are separated in longitude by

50 The spiral interplanetary magnetic field generates an asymmetry in the intensity-time profiles of SEP. In particular, events originating in the western hemisphere of the Sun are more likely to produce SEPs able to reach the Earth with respect to those in the eastern hemisphere. Protons can arrive from magnetically wellconnected sites in tens of minutes. For particles in the GeV range, the most effective longitude is close to 60 W. CME propagation The high fluence active sun period is of 7 years, from 2 years before the solar maximum year to 4 years after. The propagation time (between event and appearance of protons at the spacecraft) is a strong function of the longitude of the solar event. The time of the onset corresponds to the time at which the shock intercepts the magnetic field lines to the spacecraft Reames, D. V., 2002, Space Radiation (Japan), 3, 69 50

51 SOHO movie 1 Strong flare seen by SOHO 51

52 SOHO movie 2 SOHO multiple flare observation 52

53 LISA spacecraft characteristics Distance from the Sun AU Latitude off the ecliptic 0.7 o 1.0 o Longitude difference with respect to Earth 19 o 21 o 53

54 SEPs on LISA The shock nose of a typical gradual event takes about two days to reach Earth or LISA, half a day to cover the distance Earth-Lisa and about one hour to go through the three LISA detectors Gradual event can cause a series of signals of frequency below a few units 10-4 Hz For these reasons ESA and NASA decided to put cosmic-ray detectors on board each LISA spacecraft 54

55 Is it possible to perform some kind of physics with these detectors? Some recent history: 55

56 ULYSSES EXPERIMENT 56

57 SOHO EXPERIMENT 57

58 SEP FLUXES AT DIFFERENT LATITUDES 58

59 CME observed at different longitudes 59

60 CME INVARIANT SPECTRAL REGION 60

61 TWO EXPANDING CMEs 61

62 Solar physics with LISA Lisa might offer special conditions to study strong CMEs Earth detectors measurements might be correlated to the LISA particle counters Small step (2 degrees) and large step (20 degrees) longitude measurements might give precious hints on solar physics Lack of data between above 100 MeV where our detectors will operate 62

63 PHOEBUS: PHysics Of Events BUrsted by the Sun (Proposed by Helios Vocca and Catia Grimani) Il progetto è stato presentato al LISA Symposium, al LIST (LISA International Science Team) ed al COSPAR a Luglio E stato proposto dal LIST come guest experiment su LISA (è in corso la stesura del proposal) 63

64 PHOEBUS: PHysics Of Events BUrsted by the Sun Ha riscosso un entusiastico successo tra i fisici solari. Attualmente sono state attivate collaborazioni con responsabili italiani ed europei di fisica solare e space weather (Maurizio Candidi, Marisa Storini, Ester Antonucci, Eamonn Daly) Siamo stati inseriti nell Action Cost 724 della comunità europea ed in un programma di lungo periodo dell ASI di Fisica Spaziale per l Esplorazione del Sistema Solare. 64

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