Propagation of information within coronal mass ejections

By Luke Barnard Comment Closed
[This originally appeared as a UKSP science nugget] Coronal mass ejections (CMEs) are huge, episodic eruptions of solar plasma and magnetic field which travel through the solar corona and out into the heliosphere. At Earth, they drive the most severe geomagnetic storms and thus are the primary focus of space-weather forecasting. Using white-light imagers, individual CMEs can be tracked continuously from the low corona, through the solar wind, all the way to Earth [1] and beyond. Such observations show CMEs apparently bouncing off each other [2] and deflecting off other coronal and solar wind structures [3]. Thus it is tempting to think of a CME as a coherent structure; a single – perhaps even quasi-solid — body, playing out a game of solar billiards. Such structural coherence has two physical requirements. Firstly, coherence requires a restoring force which can (at least partially) resist deformation by external factors. E.g., A bubble is a coherent body as surface tension communicates external forces across the entirety...
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Testing the current paradigm for space weather prediction with heliospheric imagers

By Alex Daykin Comment Closed
Predicting the arrival of coronal mass ejections (CMEs) in near-Earth space is a challenging and important problem, as CMEs are the main driver of severe space weather. The Heliospheric Imager (HI) cameras provide observations of the plasma between the Sun and Earth and can be used to track the evolution of CMEs as they flow away from the Sun, toward Earth. Techniques have been developed to use the HI observations to predict the arrival of CMEs in near-Earth space, potentially allowing the HI observations to be used in a space weather forecasting context. We assess how well these methods work for four CMEs observed by the HI cameras. We found that for these four events the techniques that use HI observations do not perform as well as the standard CME forecasting techniques used by the Space Weather Prediction Center. We try to improve the HI-based predictions by using a citizen science approach to develop a better method of tracking the...
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Solar wind variations over the last four centuries

By Alex Daykin Comment Closed
The heliospheric magnetic field (HMF) varies over all observed timescales, from millennia (top), though decades/centuries (middle) to days/hours (bottom). In this study we used sunspot records to reconstruct the global solar wind and heliospheric magnetic field for the first time. We find that during the Maunder minimum, a period of anonymously low sunspot numbers from AD 1650 to 1715, the solar wind speed was approximately half its modern value, with a similar drop in HMF intensity. This is likely to have led to a much larger terrestrial magnetosphere and a much reduced heliosphere.Owens, M. J., M. Lockwood, P. Riley, Global solar wind variations over the last four centuries Scientific Reports, 7, Article number: 41548 (2017) doi:10.1038/srep41548...
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