Generic magnetic field intensity profiles of interplanetary coronal mass ejections at Mercury, Venus and Earth from superposed epoch analyses

We study interplanetary coronal mass ejections (ICMEs) measured by probes at different heliocentric distances (0.3-1 AU) to investigate the propagation of ICMEs in the inner heliosphere and determine how the generic features of ICMEs change with heliospheric distance. Using data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER), Venus Express and ACE spacecraft, we analyze with the superposed epoch technique the profiles of ICME substructures, namely, the sheath and the magnetic ejecta. We determine that the median magnetic field magnitude in the sheath correlates well with ICME speeds at 1 AU, and we use this proxy to order the ICMEs at all spacecraft. We then investigate the typical ICME profiles for three categories equivalent to slow, intermediate, and fast ICMEs. Contrary to fast ICMEs, slow ICMEs have a weaker solar wind field at the front and a more symmetric magnetic field profile. We find the asymmetry to be less pronounced at Earth than at Mercury, indicating a relaxation taking place as ICMEs propagate. We also find that the magnetic field intensities in the wake region of the ICMEs do not go back to the pre-ICME solar wind intensities, suggesting that the effects of ICMEs on the ambient solar wind last longer than the duration of the transient event. Such results provide an indication of physical processes that need to be reproduced by numerical simulations of ICME propagation. The samples studied here will be greatly improved by future missions dedicated to the exploration of the inner heliosphere, such as Parker Solar Probe and Solar Orbiter.Peer reviewe

Increases in plasma sheet temperature with solar wind driving during substorm growth phases

During the substorm growth phase, magnetic reconnection extracts ~10^15 J from the solar wind through magnetic reconnection at the magnetopause, which is then stored in the magnetotail lobes. Plasma sheet pressure then increases to balance magnetic flux density increases in the lobes. We examine plasma sheet pressure, density and temperature during substorm growth phases using nine years of Cluster data (>316,000 data points). We show that plasma sheet pressure and temperature are higher during growth phases with higher solar wind driving whereas the density is approximately constant. We also show a weak correlation between plasma sheet temperature before onset and the minimum SuperMAG SML auroral index in the subsequent substorm. We discuss how energization of the plasma sheet before onset may result from thermodynamically adiabatic processes; how hotter plasma sheets may result in magnetotail instabilities and how this relates to the onset and size of the subsequent substorm expansion phase

A workshop on ‘Dietary Sweetness—Is It an Issue?’

This report summarises a workshop convened by ILSI Europe on 3 and 4 April 2017 to discuss the issue of dietary sweetness. The objectives were to understand the roles of sweetness in the diet, establish whether exposure to sweetness affects diet quality and energy intake, and consider whether sweetness per se affects health. Although there may be evidence for tracking of intake of some sweet components of the diet through childhood, evidence for tracking of whole diet sweetness, or through other stages of maturity are lacking. The evidence to date does not support adverse effects of sweetness on diet quality or energy intake, except where sweet food choices increase intake of free sugars. There is some evidence for improvements in diet quality and reduced energy intake where sweetness without calories replaces sweetness with calories. There is a need to understand the physiological and metabolic relevance of sweet taste receptors on the tongue, in the gut and elsewhere in the body, as well as possible differentiation in the effects of sustained consumption of individual sweeteners. Despite a plethora of studies, there is no consistent evidence for an association of sweetness sensitivity/preference with obesity or type 2 diabetes. A multifaceted integrated approach, characterising nutritive and sensory aspects of the whole diet or dietary patterns, may be more valuable in providing contextual insight. The outcomes of the workshop could be used as a scientific basis to inform the expert community and create more useful dialogue among health care professionals

Predicted arrivals of solar storms at planets and spacecraft 2007-2014 with STEREO

This is a visualization of the predicted impacts of solar storms observed with the STEREO heliospheric imagers covering 2007-2014, at a 3 hour time resolution. <div><br></div><div>It shows planets (filled circles) and spacecraft (filled squares) projected in the solar equatorial plane, in colors as indicated at the bottom. Large red (blue) circles are CMEs moving at constant propagation speed, with constant direction and constant angular width of 60°, modeled after observations by STEREO-Ahead (STEREO-Behind). </div><div><br></div><div>At an impact time, a circle with the color of the spacecraft and size related to the impact speed at the target according to the legend on the lower part of the figure is produced. This „impact circle" fades away with time so an impact is better visible. </div

HELCATS catalog of predicted coronal mass ejection arrivals ARRCAT

This catalog lists arrivals of solar coronal mass ejections at various spacecraft and planets predicted with the STEREO heliospheric imager instruments, between April 2007 - September 2014.<div><br></div><div><div>If this is used for a peer reviewed publication, please notify me via "christian.moestl [at] oeaw.ac.at" or "https://twitter.com/chrisoutofspace"</div><div><br></div><div>Number of events in ARRCAT: 1995</div><div><br></div><div>Targets: EARTH-L1, STEREO-A, STEREO-B, VENUS, MESSENGER, MARS, SATURN, ULYSSES, MSL, MAVEN, ROSETTA</div><div><br></div><div>The .sav file can be read directly in IDL ("restore" function) and python ("scipy.io.readsav").</div><div><br></div><div>See header file for more explanations.</div></div

Classification of comet 67P dust at the nanometre scale with MIDAS on-board Rosetta

International audienceThe properties of the smallest sub-units of cometary dust contain information on their origin and clues to the formation of planetesimals and planets. The MIDAS Atomic Force Microscope (AFM) on-board the ESA Rosetta orbiter collected dust in the coma of comet 67P/Churyumov-Gerasimenko. These particles, collected at low velocities, were analysed to measure the structural properties of minimally altered material with a known origin. This can be used to further the investigation of our early Solar System. A novel method is presented to achieve the highest spatial resolution of imaging possible with the MIDAS instrument. 3D topographic images with resolutions of down to 8 nm are analysed to determine the sub-unit sizes of particles on the nanometre scale

HELCATS interplanetary coronal mass ejection catalogue ICMECAT

<div>This is the HELCATS interplanetary CME catalog, based on magnetometer and plasma observations in the heliosphere.</div><div><br></div><div><div>If this is used for a peer reviewed publication, please notify me via "christian.moestl [at] oeaw.ac.at" or "https://twitter.com/chrisoutofspace"</div><div><br></div><div>Number of events in ICMECAT: 668</div><div><br></div><div>ICME observatories: Wind, STEREO-A, STEREO-B, VEX, MESSENGER, ULYSSES</div></div><div><br></div><div>Time range: January 2007 - December 2015.<br></div><div><br></div><div>The .sav file can be read directly in IDL ("restore" function) and python ("scipy.io.readsav").<br></div><div><br></div><div>See header file for more explanations.<br></div><div><br></div

Strong coronal channelling and interplanetary evolution of a solar storm up to Earth and Mars

The severe geomagnetic effects of solar storms or coronal mass ejections (CMEs) are to a large degree determined by their propagation direction with respect to Earth. There is a lack of understanding of the processes that determine their non-radial propagation. Here we present a synthesis of data from seven different space missions of a fast CME, which originated in an active region near the disk centre and, hence, a significant geomagnetic impact was forecasted. However, the CME is demonstrated to be channelled during eruption into a direction + 37+/-10 degree (longitude) away from its source region, leading only to minimal geomagnetic effects. In situ observations near Earth and Mars confirm the channelled CME motion, and are consistent with an ellipse shape of the CME-driven shock provided by the new Ellipse Evolution model, presented here. The results enhance our understanding of CME propagation and shape, which can help to improve space weather forecasts.Comment: 6 figures, published in Nature Communications as open acces