3 rd RSIH&SWA Workshop – Morelia, Mexico – 21 October 2015 Updates of Observations of Heliospheric Faraday Rotation (FR) and Interplanetary Scintillation (IPS) with the LOw Frequency ARray (LOFAR): Steps Towards Improving Space-Weather Forecasting Capabilities M.M. Bisi (1), R.A. Fallows (2), C. Sobey (2), T. Eftekhari (3,2), E.A. Jensen (4), B.V. Jackson (5), H.-S. Yu (5), P.P. Hick (6,5), D. Odstrcil (7,8), and M. Tokumaru (9). (1) RAL Space, Science and Technology Facilities Council, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire, OX11 0QX, England, UK (2) ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands (3) University of New Mexico, Albuquerque, NM 87131, USA (4) Planetary Science Institute, 1700 East Fort Lowell, Suite 106, Tucson, AZ , USA (5) Center for Astrophysics and Space Science, University of California, San Diego, La Jolla, CA, , USA (6) San Diego Supercomputer Center, University of California, San Diego, La Jolla, CA, , USA (7) NASA Goddard Space Flight Center, Greenbelt, MD, USA (8) School of Physics, Astronomy, and Computational Sciences, George Mason University, 4400 University Drive, Fairfax, VA , USA. (9) STELab, Nagoya University, Furo-Cho, Chikusa-ku, Nagoya , Japan

Outline  Why?  Brief Reminder of the Multi-Site Interplanetary Scintillation (IPS) Experiment (Radio Heliospheric Imaging)  LOFAR (including brief updates)  IPS Developments with LOFAR  Heliospheric Faraday Rotation (FR) Determination and Verification Developments with LOFAR  Brief Summary

Why?

Space Weather can Effect Almost all of Society!

Brief Reminder of the Multi-Site Interplanetary Scintillation (IPS) Experiment (Radio Heliospheric Imaging) - e.g. see M.M. Bisi, “Planetary, heliospheric, and solar science with radio scintillation”, Chapter 13 of Heliophysics Volume IV “Active stars, their astrospheres, and impacts on planetary Environments”, Editors C.J. Schrijver, F. Bagenal, and J.J. Sojka, Cambridge University Press, in-press, 2015, and references therein.

Multi-Site IPS (1) Radio signals received at each site are very similar except for a small time-lag. The cross-correlation function can be used to infer the solar wind velocity(s) across the line of sight (LOS). (Not to scale) Hubble Deep Field – HST (WFPC2) 15/01/96 – Courtesy of R. Williams and the HDF Team and NASA IPS is most-sensitive at and around the P-Point of the LOS to the Sun and is only sensitive to the component of flow that is perpendicular to the LOS; it is variation in intensity of astronomical radio sources on timescales of ~0.1s to ~10s that is observed.

Multi-Site IPS (2)

IPS (g-level/density) Density Turbulence  Scintillation index, m, is a measure of level of turbulence  Normalized Scintillation index, g = m(R) / g > 1  enhancement in  Ne g  1  ambient level of  Ne g < 1  rarefaction in  Ne (Courtesy of Periasamy K. Manoharan) Scintillation enhancement with respect to the ambient wind identifies the presence of a region of increased turbulence/density and possible CME along the line-of-sight to the radio source

LOFAR (including brief updates)

The LOw Frequency ARray (LOFAR) (1) Low-Band Dipoles ~10 to ~90 MHz. High-Band Tiles 110 to ~250 MHz.

LOFAR (2)

LOFAR (3)  Pathfinder to the Square Kilometre Array (SKA).  Frequency agile system over two primary observing bands of 10 MHz to ~240 MHz split into 10 MHz to 90 MHz (LBA) and 110 MHz to ~240 MHz (HBA) with two antenna types.  Ample collecting area with plenty of combinations of multi-site observations with the International Stations over long baselines.  Experimentation with beam modes to enable band widths encompassing 80 MHz to ~the entire observing frequency range!  Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) based on LOFAR technology located just inside Finland.

LOFAR (4)  LOFAR has and is being used to investigate many aspects of Heliophysics including the following examples (there are several papers in the literature now using LOFAR and/or KAIRA data based on these and related areas of investigation): - Solar wind and CME structure (via IPS); - The changing magnetic field of the inner heliosphere (via FR); - Solar disc imaging; - Planetary auroral emissions; - Solar radio burst investigations (including via novel tied-array beam modes; and - Ionospheric studies based around scintillation characteristics and using secondary spectra to be to determine height to the scattering screen.

IPS Developments with LOFAR

- Investigations are ongoing. Our Second Coronal Mass Ejection (CME) with LOFAR…

LOFAR Observations of IPS 31 May 2013 (1) E-Limb 399 km s -1 E-Limb 540 km s -1 E-Limb 466 km s -1 E-Limb 490 km s R S at 11.5° Lat R S at 15.3° Lat R S at 42.4° Lat R S at 23.9° Lat.

LOFAR Observations of IPS 31 May 2013 (2) W-Limb 288 km s -1 W-Limb 363 km s -1 W-Limb 369 km s -1 W-Limb 372 km s R S at 19.4° Lat R S at 36.1° Lat R S at 27.5° Lat R S at 28.6° Lat.

LOFAR Observations of IPS on 03 June 2013 W-Limb CME! 522 km s -1 E-Limb 442 km s -1 W-Limb 585 km s -1 behind CME W-Limb 496 km s -1 behind CME R S at 45.9° Lat R S at 28.1° Lat R S at 33.0° Lat R S at 26.3° Lat.

Initial CME Identification (Above) In-ecliptic positions and/or projections at the time of the LOFAR CME observation in IPS ( bin/make_where_gif). P-Point Projection LOS Projection (Below) An HI-2A smoothed difference movie of 03 June 2013 – part of CME just seen beyond the Earth on the right-hand side.

Heliospheric Faraday Rotation (FR) Determination and Verification Developments with LOFAR

LOFAR Heliospheric Faraday Rotation Observations LOFAR heliospheric Faraday rotation (FR) observations to date are as follows… Crab Nebula/3C144 (15 minutes of FR each time, plus 60 minutes of IPS on 02 July 2014 only):  02 July 2014 (10:40UT) – P-Point of 69 R S, 16.2°, Heliocentric Lat. -4.4°.  11 July 2014 (10:00UT) – P-Point of 104 R S, 24.8°, Heliocentric Lat. -2.8°.  22 July 2014 (12:00UT) – P-Point of 146 R S, 35.3°, Heliocentric Lat. -1.8°. PSR J :  13 August 2014 (13:00UT) – P-Point of 43.6 R S, 11.6°, and an extended observation of 140 minutes split into 20-minute intervals yet to be fully investigated in terms of the context of the observation. LOFAR Pulsar Catalogue of daytime FR observations is currently being put together to extend our availability of likely case studies.

Combined IPS (60 minutes) and FR (15 minutes) Observations of the Crab Nebula (3C144/PSR B / PSR J ) Using LOFAR International Stations Plus the Core, Respectively, on 02 July 2014, and FR using LOFAR Core on 11 and 22 July Work in progress – publications soon to be in preparation.

Variation in RM and Ionospheric Calibration  RM variations of the Crab pulsar observations on the three dates shown through July 2014 (green) along with the calculated ionospheric RM contributions plus inherent RM of the source (blue) using the LOFAR ionFR routine using TEC maps derived from CODE and IGSG.  A difference between the two is seen and this should be due to the heliospheric contributions to the RM.

Inner-Heliosphere Ecliptic Context 02 July 2014 (1)  Left-hand Image courtesy of the STEREO Science Center – Where is STEREO? ( Direction of the Crab Nebula (radio source) Density at Mercury from the UCSD tomography (using STELab IPS and Wind data) with the 1/R 2 put back in (since the below image is normalised to 1 AU) provides n = 31.9 cm -3 (low).

 ENLIL MHD modelling using the UCSD IPS tomography as input to drive the model (IPS- driven ENLIL) as opposed to using the traditional WSA as input.  Very-preliminary results suggest this provides an improved background solar-wind environment in the MHD modelling. Inner-Heliosphere Ecliptic Context 02 July 2014 (2)

02 July 2014 Back-of-Envelope Calculations  The observed RM was: ± 0.02 rad m -2.  The expected RM of the Crab (at this frequency range) is expected to be: rad m -2 (based on anti-solar observations taken during February 2014).  The modelled ionospheric RM was: ± rad m -2.  The remaining RM, assumed due to be from the slow solar wind, is: ± rad m -2, i.e ± 0.16 rad m -2 (high?).  Thus, using FR = λ 2 RM (and just using the central frequency), the resulting FR is roughly: rad.  UCSD model RM ~ -0.34° m -2 (0.006 rad m -2 ) (~1/57 LOFAR)?  Simplification: RM = x n e [cm -3 ] x B[nT] x L[AU]° m -2 where L is the contributing integration length along line of sight = x 80 x -150 x 0.4 = -9.6° m -2 ( rad m -2 ) (high?).

Other ecliptic context

Preliminary RM and FR (back-of-envelope calculations)  For similar solar-wind conditions, you expect the RM to decrease with distance from the Sun as the source moves further out from the Sun on the sky – this seems not to be the case from 02 to 11 to 22 July  The 11 July 2014 is potentially a CME as seen in the ecliptic context plots, but further investigations are needed.  The 22 July 2014 line of sight is possibly going through the northern edge of a high-speed stream and it’s not clear if this could contribute a greater RM than ambient slow solar wind, but it may due to the changes in the medium along the LOS.  All LOFAR values are ~57 times greater than for the modelling.

Observations of FR (140 minutes) of PSR J ) Using LOFAR International Station on 13 August Work in progress – publications soon to be in preparation.

Preliminary RM Calculations for 13 August 2014  Again with the simplification calculation (but only for the lowest value here): RM = x n e [cm -3 ] x B[nT] x L[AU]° m -2 where L is the contributing integration length along line of sight = x 80 x -150 x 0.4 = -3.84° m -2 ( rad m -2 ) (high? – but matches the 13:20UT-13:40UT value).  Context information is needed here – that’s the next step.

Contributions to the Faraday Rotation Signal (Courtesy of Colin J. Lonsdale)

Brief Summary

 IPS is an extremely powerful and unique technique for making heliospheric imaging observations of the inner heliosphere.  IPS/FR on LOFAR is progressing very well with good solar wind/ CME results, and preliminary heliospheric RM/FR determination – but much more work to be done, especially on ionospheric FR.  Both IPS and FR are becoming more useful for space-weather science and forecasting (a second golden age of IPS?).  The UCSD 3-D tomography will provide an excellent platform for obtaining 3-D magnetic-field values from combined radio observations of FR and IPS and integrating them into current IPS, closed-loop fields, and L 1 in-situ data tomography (and also as an improved input to drive ENLIL). Summary