Heliospheric Images of the Solar Wind at Earth

Abstract

During relatively quiet solar conditions throughout the spring and summer of 2007, the SECCHI HI2 white-light telescope on the STEREO B solar-orbiting spacecraft observed a succession of wave fronts sweeping past Earth. We have compared these heliospheric images with in situ plasma and magnetic field measurements obtained by nearEarth spacecraft, and we have found a near perfect association between the occurrence of these waves and the arrival of density enhancements at the leading edges of high-speed solar wind streams. Virtually all of the strong corotating interaction regions are accompanied by large-scale waves, and the low-density regions between them lack such waves. Because the Sun was dominated by long-lived coronal holes and recurrent solar wind streams during this interval, there is little doubt that we have been observing the compression regions that are formed at low latitude as solar rotation causes the high-speed wind from coronal holes to run into lower speed wind ahead of it. Subject headingg s: Sun: corona -Sun: coronal mass ejections (CMEs) -Sun: magnetic fields

An Empirical Reconstruction of the 2008 April 26 Coronal Mass Ejection

“…It should be mentioned that the slowly moving faint fronts seen out ahead of the red arrows in the two HI2-A images appear to us to be possible signatures of a corotating interaction region (CIR) that is also moving through the IPM at the time of the CME, a complicating factor in the interpretation of the HI2 images. Sheeley et al (2008aSheeley et al ( , 2008b and Rouillard et al (2008) have previously described the appearance of CIRs in HI2 data.…”

“…It can be difficult to discern faint CME fronts as far from the Sun as the HI2 field of view. The HI2 images in Figure 4 are running-difference images like those in Figure 3, but there are additional reduction steps to subtract the stellar and zodiacal background in order to better reveal the structures that are present in the solar wind (Sheeley et al 2008b). The arrows in Figure 4 indicate the parts of the observed structure that we believe correspond to the leading and trailing parts of the flux rope.…”

“…What is initially measured in the images are not distances from Sun-center but elongation angles, . The elongation angles are converted to distances, r, using the following equation (Kahler & Webb 2007;Sheeley et al 2008b;Wood et al 2009aWood et al , 2009b:…”

Interplanetary and Geomagnetic Consequences of Interacting CMEs of 13 – 14 June 2012

“…For the tracking of CME features, a minimum background image was created from a sequence of HI images. We constructed the time-elongation maps, conventionally called J-maps, (Sheeley et al, 2008;Davies et al, 2009) using the running difference images of HI-1 and HI-2. The details of the procedure to construct the J-maps and to derive the distance from the measured elongation angles have been described in Mishra, Srivastava, and Chakrabarty (2015); Mishra, Wang, and Srivastava (2016).…”

The Wide-Field Imager for Solar Probe Plus (WISPR)

“…To study the details of these small-scale transients, we need high-resolution observations, as these transients commonly take up only a few pixels in current LASCO and SEC-CHI coronagraph observations (Sheeley et al 2008;Rouillard et al 2008Rouillard et al , 2009. WISPR is designed with a 6.4 arcmin resolution so that it can image and trace the streamer blobs, within its FOV, to large heights and with a resolution equivalent to or better than that of the LASCO or SECCHI coronagraphs.…”