Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array
© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Refraction and diffraction of incoming radio waves by the ionosphere induce time variability in the angular positions, peak amplitudes and shapes of radio sources, potentially complicating the autom...
| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Journal Article |
| Published: |
2015
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| Online Access: | http://hdl.handle.net/20.500.11937/28456 |
| _version_ | 1848752542200102912 |
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| author | Loi, S. Murphy, T. Bell, M. Kaplan, D. Lenc, E. Offringa, A. Hurley-Walker, Natasha Bernardi, G. Bowman, J. Briggs, F. Cappallo, R. Corey, B. Deshpande, A. Emrich, David Gaensler, B. Goeke, R. Greenhill, L. Hazelton, B. Johnston-Hollitt, M. Kasper, J. Kratzenberg, E. Lonsdale, C. Lynch, Mervyn McWhirter, S. Mitchell, D. Morales, M. Morgan, E. Oberoi, D. Ord, Stephen Prabu, T. Rogers, A. Roshi, A. Udaya Shankar, N. Srivani, K. Subrahmanyan, R. Tingay, Steven Waterson, M. Wayth, Randall Webster, R. Whitney, A. Williams, Andrew Williams, C. |
| author_facet | Loi, S. Murphy, T. Bell, M. Kaplan, D. Lenc, E. Offringa, A. Hurley-Walker, Natasha Bernardi, G. Bowman, J. Briggs, F. Cappallo, R. Corey, B. Deshpande, A. Emrich, David Gaensler, B. Goeke, R. Greenhill, L. Hazelton, B. Johnston-Hollitt, M. Kasper, J. Kratzenberg, E. Lonsdale, C. Lynch, Mervyn McWhirter, S. Mitchell, D. Morales, M. Morgan, E. Oberoi, D. Ord, Stephen Prabu, T. Rogers, A. Roshi, A. Udaya Shankar, N. Srivani, K. Subrahmanyan, R. Tingay, Steven Waterson, M. Wayth, Randall Webster, R. Whitney, A. Williams, Andrew Williams, C. |
| author_sort | Loi, S. |
| building | Curtin Institutional Repository |
| collection | Online Access |
| description | © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Refraction and diffraction of incoming radio waves by the ionosphere induce time variability in the angular positions, peak amplitudes and shapes of radio sources, potentially complicating the automated cross-matching and identification of transient and variable radio sources. In this work, we empirically assess the effects of the ionosphere on data taken by the Murchison Widefield Array (MWA) radio telescope. We directly examine 51 h of data observed over 10 nights under quiet geomagnetic conditions (global storm index Kp < 2), analysing the behaviour of short-time-scale angular position and peak flux density variations of around ten thousand unresolved sources. We find that while much of the variation in angular position can be attributed to ionospheric refraction, the characteristic displacements (10-20 arcsec) at 154 MHz are small enough that search radii of 1-2 arcmin should be sufficient for crossmatching under typical conditions. By examining bulk trends in amplitude variability, we place upper limits on the modulation index associated with ionospheric scintillation of 1-3 per cent for the various nights. For sources fainter than ~1 Jy, this variation is below the image noise at typical MWA sensitivities. Our results demonstrate that the ionosphere is not a significant impediment to the goals of time-domain science with the MWA at 154 MHz. |
| first_indexed | 2025-11-14T08:10:16Z |
| format | Journal Article |
| id | curtin-20.500.11937-28456 |
| institution | Curtin University Malaysia |
| institution_category | Local University |
| last_indexed | 2025-11-14T08:10:16Z |
| publishDate | 2015 |
| recordtype | eprints |
| repository_type | Digital Repository |
| spelling | curtin-20.500.11937-284562017-09-13T15:20:30Z Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array Loi, S. Murphy, T. Bell, M. Kaplan, D. Lenc, E. Offringa, A. Hurley-Walker, Natasha Bernardi, G. Bowman, J. Briggs, F. Cappallo, R. Corey, B. Deshpande, A. Emrich, David Gaensler, B. Goeke, R. Greenhill, L. Hazelton, B. Johnston-Hollitt, M. Kasper, J. Kratzenberg, E. Lonsdale, C. Lynch, Mervyn McWhirter, S. Mitchell, D. Morales, M. Morgan, E. Oberoi, D. Ord, Stephen Prabu, T. Rogers, A. Roshi, A. Udaya Shankar, N. Srivani, K. Subrahmanyan, R. Tingay, Steven Waterson, M. Wayth, Randall Webster, R. Whitney, A. Williams, Andrew Williams, C. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Refraction and diffraction of incoming radio waves by the ionosphere induce time variability in the angular positions, peak amplitudes and shapes of radio sources, potentially complicating the automated cross-matching and identification of transient and variable radio sources. In this work, we empirically assess the effects of the ionosphere on data taken by the Murchison Widefield Array (MWA) radio telescope. We directly examine 51 h of data observed over 10 nights under quiet geomagnetic conditions (global storm index Kp < 2), analysing the behaviour of short-time-scale angular position and peak flux density variations of around ten thousand unresolved sources. We find that while much of the variation in angular position can be attributed to ionospheric refraction, the characteristic displacements (10-20 arcsec) at 154 MHz are small enough that search radii of 1-2 arcmin should be sufficient for crossmatching under typical conditions. By examining bulk trends in amplitude variability, we place upper limits on the modulation index associated with ionospheric scintillation of 1-3 per cent for the various nights. For sources fainter than ~1 Jy, this variation is below the image noise at typical MWA sensitivities. Our results demonstrate that the ionosphere is not a significant impediment to the goals of time-domain science with the MWA at 154 MHz. 2015 Journal Article http://hdl.handle.net/20.500.11937/28456 10.1093/mnras/stv1808 fulltext |
| spellingShingle | Loi, S. Murphy, T. Bell, M. Kaplan, D. Lenc, E. Offringa, A. Hurley-Walker, Natasha Bernardi, G. Bowman, J. Briggs, F. Cappallo, R. Corey, B. Deshpande, A. Emrich, David Gaensler, B. Goeke, R. Greenhill, L. Hazelton, B. Johnston-Hollitt, M. Kasper, J. Kratzenberg, E. Lonsdale, C. Lynch, Mervyn McWhirter, S. Mitchell, D. Morales, M. Morgan, E. Oberoi, D. Ord, Stephen Prabu, T. Rogers, A. Roshi, A. Udaya Shankar, N. Srivani, K. Subrahmanyan, R. Tingay, Steven Waterson, M. Wayth, Randall Webster, R. Whitney, A. Williams, Andrew Williams, C. Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array |
| title | Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array |
| title_full | Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array |
| title_fullStr | Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array |
| title_full_unstemmed | Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array |
| title_short | Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array |
| title_sort | quantifying ionospheric effects on time-domain astrophysics with the murchison widefield array |
| url | http://hdl.handle.net/20.500.11937/28456 |