A1D4.2

Lead Beneficiary: HVAR

Beneficiaries involved: KU Leuven, MTA-KFKI-RMKI, UOulu

Due Date: month 24

Goal

Report on results of Task 4.1, which includes: observation and modeling of the interplanetary propagation of CMEs and prediction of their arrival times; ICME related cosmic ray variations; the relationship between coronal holes and the near-Earth high-speed streams and related geomagnetic disturbances.

Successes

In December 2008, a CME from the low corona to the Earth magnetosphere has been tracked for the first time ever. The analysis of this event is in progress (UGOE).

Progress so far

The interplanetary propagation of solar disturbances that affect the Earth was studied applying empirical/statistical procedures, analytical MHD modeling, and numerical MHD simulations. The primary objectives were the two most important space-weather features: coronal mass ejections (CMEs) and co-rotating interaction regions (CIRs).

All beneficiaries included in Task 4.1/WP4 (HVAR, KU Leuven, MTA-KFKI-RMKI, UOulu), strongly supported also by DTU, LPI, NOVELTIS, and UNIGRAZ, took part in the analysis of seven Sun-Earth CME-related events (see deliverable A1D4.1). These events were chosen from a larger sample, as potentially the best examples to study the interplanetary propagation of CMEs and their impact to the Earth. For this study especially important was the "Event Workshop" held at Hvar/Croatia 13-18 Sept 2009, where all of the mentioned beneficiaries met together. At the workshop previously obtained results were summarized, providing a smooth continuation of the study by defining further steps of the analysis and specifying the tasks (see the report under Soteria Meetings).

Special attention was paid to the Sun-Earth event related to the CME of 25 July 2004. The observed transit time and 1 AU velocity were compared with the outcome of the drag-based analytical model and the numerical code ENLIL, where coronagraphic measurements are used for the model input. Both models showed a very good performance in predicting the arrival of the interplanetary disturbance. After adjusting the procedures on this test-example, model runs were performed also for the other 6 events from the WP4 event-list, as well as for two homologous events preceding the eruption of 25 July 2004. Currently, we submitted a paper to the journal Astronomy & Astrophysics, where the analytical drag-based model of the interplanetary propagation of CMEs is presented, and the application demonstrated using the CME of 25 July 2004. The analysis of the ENLIL results for the 25 July 2004 event will be presented in a separate paper (almost ready for submission). The time profiles of the energetic particle fluxes at energies 0.125 to 32 MeV as observed aboard SOHO during this event were compared with the prediction of the Solar Particle Engineering Code (Solpenco). Whereas the profiles near the maximum are reproduced reasonably, the model predicts strong deceleration of the CME speed, which, to match the observed transit time, requires an initial speed of the coronal mass ejection significantly higher than observed by LASCO. This suggests that we need better understanding of the CME speed variation outside of the coronagraph field of view to predict the arrival time of the shock.

Beside the study of the mentioned seven events, about 80 CMEs were studied stereoscopically employing STEREO/SECCHI data (UGOE). For the first time CMEs from the Sun up to distances of ~ 1 AU have been directly observed with STEREO/SECCHI, and their in-situ properties for the cases they passed the orbits of STEREO A and B were measured. In December 2008, a CME from the low corona to the Earth magnetosphere has been tracked for the first time ever. The analysis of this event is in progress.

At KU Leuven plasma flow parameters around the stationary and expanding cylindrical plasma cloud were studied, as a preparation for the investigating the dynamics of the magnetic cloud by using the self-similar approach. Furthermore, the kinetic simulation of the decay of turbulence in the corona and in solar wind is set up, with new particle-in-cell-code Parsek3D. A number of cases were run to test the ability of having realistic parameters and the ability of the model to preserve invariant quantities such as energy and momentum.

Considering the study of CIRs, a series of solar wind high speed streams (HSSs) in 2005 and 2006 was chosen, since this was a period of low CME activity, and on the other hand, very good soft X-ray observations of equatorial coronal holes (ECHs) exist for this period. The relationship between coronal hole areas/positions and characteristics of the associated HSSs and related geomagnetic disturbances is analyzed. An empirical forecasting model is proposed, providing predictions of solar wind parameters and geomagnetic indices at the 6-hour resolution (a paper in preparation). The 2005 period is also used to investigate the HSS-related modulation of the cosmic ray flux (a paper in preparation). Comparison of the forecasting capabilities of the developed empirical model and MHD-numerical models is in progress (DTU, HVAR, KU Leuven) in cross-collaboration with WP3 (UNIGRAZ). The next step is to extend the study of the ECH-HSS relationship by employing the EUV observations, which would provide the whole-cycle time series. This would provide forecasting of the background solar wind characteristic at any phase of the solar cycle, which is essential for application of the drag-based model of the CME propagation.

List of the people working on this deliverable: HVAR: Bojan Vrsnak, Tomislav Zic, Jasa Calogovic, Dijana Vrbanec; KU Leuven: Giovanni Lapenta, Maria Elena Innocenti, Giorgi Dalakishvili, Stefaan Poeds i Giga Gogoberidze; MTA-KFKI-RMKI: Karoly Kecskemety, Peter Kiraly; UOulu: Kalevi Mursula, Ilpo Virtanen; DTU (cross-collaboration with D4.1): Susanne Vennerstrom, Thea Falkenberg; UGOE (cross-collaboration WP3): Volker Bothmer; UNIGRAZ (cross-collaboration WP3): Astrid Veronig, Manuela Temmer, Thomas Rotter.