Ooty Radio Telescope Space Weather

Transcription

1 Ooty Radio Telescope Space Weather P.K. Manoharan Radio Astronomy Centre National Centre for Radio Astrophysics Tata Institute of Fundamental Research Ooty , India Panel Meeting onspace Situational Awareness, Space Weather and Space Debris Research COSPAR 2012, Mysore 19 July 2012

2 Outline Space Weather Geo-magnetic activities Coronal mass ejections and interaction regions Ooty Radio Telescope Interplanetary Scintillation (IPS) Tracking of CME in the Sun Earth heliosphere 3-D reconstruction of solar wind structures Some results

3 Space Weather Sun Earth Connection Space weather is the manifestation of Sun-Earth relationship. It encompasses the following topics Mechanism of solar variability Physics of the solar wind and heliosphere Structure and dynamics of magnetosphere and their coupling to adjacent regions Middle and upper atmosphere and their coupling to regions above and below Plasma processes that accelerate energetic particles and control their propagation

4 Geo-magnetic activities Effective space weather solar wind transients are High-speed coronal mass ejections (CMEs) propagating along the Sun-Earth line Co-rotating interaction regions (CIRs) compress at the day side of the magnetosphere is severe The resultant complex processes (as observed from the surface of the Earth) cause geo-magnetic activities. Geo-magnetic activity Consists of geo-magnetic storm and substorm Their prediction is limited by variable (or turbulent) nature of the solar wind

5 Coronal Mass Ejections Largest phenomenon associated with the dissipation of magnetic flux at and above the surface of the Sun Travel outward at range of speeds, km/s Mass involved in each ejection is ~ g Main cause of large geo-magnetic storms CMEs appear to be an important factor of space weather, which has multiple geospheric, biospheric, and technological effects. A great interest in understanding the propagation and arrival of Earth-directed CMEs, which cause major storms at the Earth s magnetosphere. However, there are many open questions concerning CMEs origin, evolution, structure/extent in the interplanetary space To progress in understanding the effects of CMEs requires detail 3-D data on them from Sun to Earth

6 Coronal Mass Ejections (CMEs) It is essential to understand their size, density, and speed 3-D space from Sun to Earth plus evolution of shocks associated with them High-energy particle acceleration mechanisms Driving mechanisms of CMEs Interplanetary scintillation (remote sensing) technique is useful in the Sun-Earth distance

7 Single antenna of 530m x 30 m Ooty Radio Telescope. Ooty Radio Telescope

8 Latitude: North Longitude: East Ooty Radio Telescope (ORT) Equatorially mounted, off-axis parabolic cylinder 530m (N-S) x 30m (E-W) Reflecting surface made of 1100 stainless steel wires Large collecting area high sensitivity Feed 1056 λ/2 dipoles east-west tracking ~10.5 hours north-south electronic beam steering (± 65 deg.) Various astronomical studies Operated by Radio Astronomy Centre National Centre for Radio Astrophysics Tata Institute of Fundamental Research Ooty, India

9 ORT is being upgraded : Phase 1 Digitize RF from 11.5m section of ORT field of view 4.6 degree Phase 2 Digitize RF from every 4 phased dipoles (2m) Field view 27 degree Full 264-element system Software-based FX correlator Parameter Current Phase-1 Phase-2 Bandwidth 4 MHz 18 MHz 40 MHz FoV 2.3 x x x 27 Sensitivity (τ = 1 s) 40 mjy 12 mjy 1 mjy

10 Interplanetary Scintillation (IPS) * Compact radio sources, < 400 mas * small-scale ( 500 km) density irregularities in the solar wind * scattering scale size is governed by Fresnel scale, a F = z * a F 150 km at S-band * a F 400 km at = 1 m IPS measure of source intensity as a function of time, I(t) contains information on speed of solar wind density variations (i.e., δne) density turbulence spectrum (at scales ~ km at 327 MHz) angular diameter of the radio source

11 Interplanetary Scintillation Radio source L-O-S Sun Earth

12 Ooty IPS Observations IPS measurements on a large number of radio sources over a given period of time (i.e., different line-of-sight cuts in 3-D heliosphere) can provide snap shot images of inner heliosphere. At Ooty, everyday ~1200 radio sources are observed Computer-aided tomography developed in collaboration with the solar physics group at UCSD, USA, provides line of sight integral corrected solar wind 3-D structures

13 Evolution of Coronal Mass Ejections (Sun to 1 AU distance)

14 2003

15 Continuous acceleration? energy source? IPS LASCO Height-Time Plot Speed-Distance Plot

16 Speed Profiles: V CME (R) deceleration constant speed acceleration

17 Tomography reconstruction of Ooty IPS Data

18 Lines of sight typically observed in a day (2-AU cube)

19 Solar rotation and radial outward flow of the solar wind provide the 3-d structure of the solar wind at different view angles Computer Assisted Tomography analysis can remove the line-of-sight integration imposed on the solar wind parameters also provides high spatial resolution

20 Ooty 3-D Density and Speed Reconstruction Density Speed

21 Speed Comparisons with Wind in situ Data

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23 3-D Heliosphere Solar wind Density in 3-AU space

24 Ooty IPS images are useful to get the information on the arrival of CMEs at the near-earth environment Ooty study suggests that the flux rope that erupted from the Sun expands with distance, but retains its shape up to 1 AU or beyond, magnetic internal energy possessed by the CME (or magnetic cloud) determines the propagation and/or the expansion of the CME in the course of its propagation. results are consistent with the studies that the flux-rope types of the CMEs are magnetically driven

25 Thank You