Investigation of Heliospheric Faraday Rotation Due to a Coronal Mass Ejection (CME) Using the LOw Frequency ARray (LOFAR) and Space-Based Imaging Techniques Mario M. Bisi (STFC RAL Space, UK) {Mario.Bisi@stfc.ac.uk}, Elizabeth A. Jensen[2], Richard A. Fallows[3], Charlotte Sobey[3][4][5], Brian Wood[6], Bernard V. Jackson[7], Alessandra Giunta[1], David Barnes[1], P. Paul L. Hick[8][7], Tarraneh Eftekhari[9], Hsiu-Shan Yu[7], Dusan Odstrcil[10][11], Munetoshi Tokumaru[12], Caterina Tiburzi[13], and Joris Verbiest[13]. [1]STFC-RAL Space, UK, [2]Planetary Science Institute, AZ, USA, [3]ASTRON, NL, [4]Curtain Institute of Radio Astronomy, WA, Australia, [5]CSIRO Astronomy and Space Science, WA, Australia, [6]NRL, DC, USA, [7]CASS-UCSD, CA, USA, [8]SDSC-UCSD, CA, USA, [9]University of New Mexico, NM, USA, [10]GMU, VA, USA, [11]NASA GSFC, MD, USA, [12]ISEE, Nagoya University, Japan, and [13]Universität Bielefeld, Germany. © 2017 RAL Space

Outline Part 1: Introduction to Radio Observations and LOFAR. Part 2: LOFAR 13 August 2014 CME Observations. Part 3: Summary and Outlook. © 2017 RAL Space

Introduction to Radio Observations and LOFAR. Part 1: Introduction to Radio Observations and LOFAR. © 2017 RAL Space

Radio Observations Interplanetary magnetic field Faraday rotation from 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. Interplanetary scintillation from compact radio source Faraday rotation from polarised radio source Interplanetary magnetic field Solar wind velocity, density/ turbulence, and signatures of field rotation and SIRs IPS variation in amount of scintillation → density proxy IPS cross-correlation of power spectra → velocity IPS fits to individual power spectra → velocity etc… Ionospheric scintillation

The LOw Frequency ARray (LOFAR) (1) Pathfinder to the Square Kilometre Array (SKA). Frequency agile system over two primary observing bands of ~10 MHz to ~250 MHz split into ~10 MHz to 90 MHz (LBA) and 110 MHz to ~250 MHz (HBA) using two antenna types. Ample collecting area with plenty of combinations of multi-site observations with the International Stations over multiple and varying long baselines. Experimentation with beam modes to enable band widths encompassing 80 MHz to ~the entire observing frequency range with a trade off on sensitivity! Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) based on LOFAR technology located just inside Finland. © 2017 RAL Space

LOFAR (2) High-Band Tiles 110 to ~250 MHz. Low-Band Dipoles © 2017 RAL Space

LOFAR (3)

LOFAR 13 August 2014 CME Observations. Part 2: LOFAR 13 August 2014 CME Observations. © 2017 RAL Space

Heliospheric Faraday Rotation (FR) Observations (1) © 2017 RAL Space Heliospheric Faraday Rotation (FR) Observations (1) Heliospheric FR can provide B‖ along the LOS; eventually, if a large enough number of observations are taken, B‖ can be input to the UCSD tomography to provide global magnetic-field parameters as well as the already-provided velocity and density parameters. Observations of PSR J1022+1001 (J2000) on 13 August 2014 commencing at 13:00UT running to 15:20UT (data go to 16:30UT – too noisy) split into 20-minute segments with the first 10 minutes in each taken as individual observations using the LOFAR Core. Observations set up to detect the passage of a CME launched late on 12 August 2014. P-Point of LOFAR LOS around 50 solar radii with an elongation angle of around 13.3°from the Sun.

Heliospheric FR Observations (2) © 2017 RAL Space Heliospheric FR Observations (2)

Heliospheric FR Observations (3) © 2017 RAL Space Heliospheric FR Observations (3)

Heliospheric FR Observations (4) © 2017 RAL Space Heliospheric FR Observations (4) Using simple dimensional-analysis calculations: RM = 0.002 x ne[cm-3] x B[nT] x L[AU]° m-2, where L is the contributing integration length along the LOS, we get a maximum expected RM value: RM = 0.002 x 669 x 150 x 0.25 = 50.2° m-2 (or 0.928 rad m-2); perhaps high – but is very much in line with the LOFAR preliminary heliospheric RM values.

Heliospheric FR Observations (5) (Oberoi and Lonsdale, 2012)

Part 3: Summary and Outlook. © 2017 RAL Space

© 2017 RAL Space Summary Part 1: Radio Observations are proving to be very- powerful tools for space-weather science and are showing real potential for space-weather forecasting and our understanding of the complexities of space-weather and its potential impacts. Part 2: The FR work presented here, although largely preliminary in nature, is pointing the way to a new experiment using LOFAR in obtaining heliospheric FR (and ultimately B‖) results on top of the already-successful IPS experiment. Part 2: Thus far, our preliminary CME investigation is indicating that we have obtained the correct ‘ballpark’ RM values as expected from theory and as calculated from the supporting data sets used in this case study as presented (see also Bisi et al., 2017/2018a,b, in preparation). Part 2: Observations of more polarised radio sources as they transit near the Sun and at increasing POS distances are needed. Part 2: See Fallows et al., Session 4 Presentation, Tuesday.