Long-Term Tracking of Corotating Density Structures using Heliospheric Imaging

Abstract

The systematic monitoring of the solar wind in high-cadence and high-resolution heliospheric images taken by the Solar-Terrestrial Relation Observatory (STEREO) spacecraft permits the study of the spatial and temporal evolution of variable solar wind flows from the Sun out to 1~AU, and beyond. As part of the EU Framework 7 (FP7) Heliospheric Cataloguing, Analysis and Techniques Service (HELCATS) project, we have generated a catalogue listing the properties of 190 corotating structures well-observed in images taken by the Heliospheric Imager instruments on-board STEREO-A. We present here one of very few long-term analyses of solar wind structures advected by the background solar wind. This analysis confirms that most of the corotating density structures detected by the heliospheric imagers comprises a series of density inhomogeneities advected by the slow solar wind that eventually become entrained by stream interaction regions. We have derived the spatial-temporal evolution of each of these corotating density structures by using a well-established fitting technique. The mean radial propagation speed of the corotating structures is found to be $311\pm 31$ km~s${}^{-1}$. We predicted the arrival time of each corotating density structure at different probes. We show that the speeds of the corotating density structures derived using our fitting technique track well the long-term variation of the radial speed of the slow solar wind during solar minimum years (2007--2008). Furthermore, we demonstrate that these features originate near the coronal neutral line that eventually becomes the heliospheric current sheet.

27 pages, 12 figures, published in Solar Physics

References in corpus (1)

• Tracking Streamer Blobs Into the Heliosphere

Cited by in corpus (12)

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• Observational evidence for the associated formation of blobs and raining inflows in the solar Corona
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• CMEs in the Heliosphere: I. A Statistical Analysis of the Observational Properties of CMEs Detected in the Heliosphere from 2007 to 2017 by STEREO/HI-1
• Connecting Coronal Mass Ejections to their Solar Active Region Sources: Combining Results from the HELCATS and FLARECAST Projects
• A propagation tool to connect remote-sensing observations with in-situ measurements of heliospheric structures
• Automated Detection of Coronal Mass Ejections in STEREO Heliospheric Imager data
• Reconstructing solar wind inhomogeneous structures from stereoscopic observations in white-light: Small transients along the Sun-Earth line
• Reconstructing solar wind inhomogeneous structures from stereoscopic observations in white-light: Solar wind transients in 3D
• Identification of a Single Plasma Parcel during a Parker Solar Probe-Solar Orbiter radial alignment
• Three-dimensional Reconstruction of Coronal Mass Ejections by CORAR Technique through Different Stereoscopic Angle of STEREO Twin Spacecraft