Characteristics of Kinematics of a Coronal Mass Ejection during the 2010 August 1 CME-CME Interaction Event

We study the interaction of two successive coronal mass ejections (CMEs) during the 2010 August 1 events using STEREO/SECCHI COR and HI data. We obtain the direction of motion for both CMEs by applying several independent reconstruction methods and find that the CMEs head in similar directions. This provides evidence that a full interaction takes place between the two CMEs that can be observed in the HI1 field-of-view. The full de-projected kinematics of the faster CME from Sun to Earth is derived by combining remote observations with in situ measurements of the CME at 1 AU. The speed profile of the faster CME (CME2; ~1200 km/s) shows a strong deceleration over the distance range at which it reaches the slower, preceding CME (CME1; ~700 km/s). By applying a drag-based model we are able to reproduce the kinematical profile of CME2 suggesting that CME1 represents a magnetohydrodynamic obstacle for CME2 and that, after the interaction, the merged entity propagates as a single structure in an ambient flow of speed and density typical for quiet solar wind conditions. Observational facts show that magnetic forces may contribute to the enhanced deceleration of CME2. We speculate that the increase in magnetic tension and pressure, when CME2 bends and compresses the magnetic field lines of CME1, increases the efficiency of drag.Comment: accepted for Ap

Thoughts from a past AGU SPA fellows committee

Community honours, such as those bestowed by professional scientific societies like the American Geophysical Union (AGU) are an important element of both individual career advancement and contributes to the historical record of scientific progress. The process by which honours are bestowed is not widely shared amongst the community. The purpose of this article is to share the recent experiences of several members of the AGU Space Physics and Aeronomy (SPA) Fellows committee. We outline the criteria for selection, the evaluation process, difficulties encountered by the committee, and steps taken to mitigate these difficulties. Of particular note is the impact of implicit bias in the award system. Steps could be taken by the awarding scientific societies to reduce the impact of these biases, but in the meantime individual award committees can employ some of the strategies we outline in this article. By sharing our experiences, we hope to improve the process of granting awards and honours for the scientists putting together award nominations, future committee members, and the scientific societies granting these awards. &nbsp;</p

Das Weltraumwetter

Unsere Sonne beeinflusst ihre direkte kosmische Umgebung in vielfältiger Weise – sei es durch heftige Strahlungsausbrüche, durch massereiche Gaswolken, die sie in den interplanetaren Raum hinaus schleudert, oder durch den unablässig von ihr weg strömenden Sonnenwind. Diese als ‚Weltraumwetter’ bezeichneten Erscheinungen und ihre Auswirkungen auf die Erde sind ein faszinierendes Forschungsgebiet

Meeting Report: European Commission’s Space-Weather Awareness Dialogue

This short report summarises the findings of the Space-Weather Awareness Dialogue organised by the JRC and DG ENTR in Brussels, on 25-26 October 2011, and it briefly describes the JRC's planned activities on space-weather related impact on critical infrastructures and their services.JRC.G.6-Security technology assessmen

Characteristics and evolution of sheath and leading edge structures of interplanetary coronal mass ejections in the inner heliosphere based on Helios and Parker Solar Probe observations

Aims: We statistically investigate the plasma and magnetic field characteristics of the upstream regions of interplanetary coronal mass ejections (ICMEs) and their evolution as function of distance to the Sun in the inner heliosphere. We use a sample of 40 well-observed ICMEs from Helios 1/2 (0.3-1au) and 5 from Parker Solar Probe (0.32-0.75au). For each event we identify four main density structures, namely shock, sheath, leading edge (LE), and magnetic ejecta (ME) itself. Methods: We derive separately for each structure averaged plasma and magnetic field parameter values as well as duration and place the results into comparison with the upstream solar wind (SW) to investigate the interrelation between the different density structures. Results: The sheath structure presumably consists of compressed plasma due to the turbulent SW material following the shock. The sheath lies ahead of a region of compressed ambient SW, the LE, which is typically found directly in front of the magnetic driver and seems to match the bright leading edge commonly observed in remote sensing observations of CMEs. The sheath becomes denser than the ambient SW at about 0.06au, which we interpret as the average starting distance for actual sheath formation. Between 0.09-0.28au the sheath structure density starts to dominate over the density within the ME. The ME density seems to fall below the ambient SW density over 0.45-1.07au. Besides the well-known expansion of the ME, the sheath size shows a weak positive correlation with distance, while the LE seems not to expand with distance from the Sun. We further find a moderate anti-correlation between sheath density and local SW plasma speed upstream of the ICME shock. An empirical relation is derived connecting the ambient SW speed with sheath and LE density that can be used for modeling of ICME evolution. Constraints to those results are given.Comment: Accepted for A&