A1D4.6
Name: Scientific analysis report, Task 4.5, a-g
Lead Beneficiary: KU Leuven
Beneficiaries involved: Hvar, ROB, MTA-KFKI-RMKI, UOulu, DTU, IEEA, NOVELTIS
Due Date: 36 months
Goal
Development of the new methods and improvement of the existing capability for the space weather forecasting. In particular, predicting the arrival time of ICMEs and geomagnetic disturbances associated with high-speed streams from coronal holes, validation of the SOLPENCO code for extreme events, prediction of near-Earth solar wind disturbances, short-term prediction of geomagnetic storms and the time development of the improved Dst, long-term forecasting of coronal holes and solar active regions, and prediction of ionospheric scintillations.
Successes
Detailed analysis of solar X-ray flares gives strong evidence for two active longitudes and that the different classes of flares are connected to the same longitudes.
Progress so far
At KU Leuven the conditions for realistic modelling of reconnection regions with implicit PIC code Parsek, both in the dayside and in the tail were determined. Collaboration with the teams of NASA MMS mission is established in order to compare the simulations with existing observations from Cluster and Themis missions, and with future MMS data. The focus has been primarily in elucidating the role of electron holes and their induced turbulence on the reconnection.
Simulations of reconnection with Parsec were performed using realistic set of parameters (namely, realistic ion-to-electron mass ratio and Alfven velocity) in a guide-field configuration which reflects typical dayside Earth magnetopause conditions. The important result for the upcoming MMS mission is that large electron holes, distributed far along separatrices and thus marking the proximity of diffusion region, are generated continuously and stay at the separatrix for a long time. Electron pressure displays unusual anisotropy exactly on the separatrix, which could be useful for detection of the reconnection region using satellite data.
Furthermore, slowly reconnecting current sheet of finite thickness was studied in the MHD approximation, with FlipMHD code. Current profile, geometrical properties and the impact of the turbulence on the system were examined in order to clarify the nature of the instability taking place. It is shown that the slowly reconnecting current sheet in the presence of turbulence generally transits to fastly reconnecting system sooner and at generally smaller aspect ratio. Setting the realistic current sheet in the wider frame of the CME modelling is intended.
A collaboration between KU Leuven and the partner institution NOVELTIS is initiated (see D4.7) in order to apply the data assimilation (DA) techniques to the propagation of the unperturbed solar wind from the Sun to 1 AU. DA techniques, notably Ensemble Kalman Filter methods, are used to improve the quality of an initial 'guessed' input (solar magnetograms) through the iterative interaction of a model of the phenomenon to be examined (solar wind propagation model) and observations (ACE data). The aims of this activity are both to test the applicability of DA techniques to the Sun-Earth environment and to improve the quality of solar magnetograms. NOVELTIS is providing providing the expertise in DA techniques, while KU Leuven is developing the solar wind propagation model.
During the Hvar Workshop, September 2009, (cross-colaboration with WP3) a new collaborative task
was defined between DTU, Hvar and KU Leuven, where performances of numerical MHD heliospheric models in predicting the high speed streams would be compared with performances of an empirical model based on tracking equatorial coronal holes. Furthermore, Hvar Observatory and DTU analysed the Sun-Earth event of 25 July 2004 by comparing the observed transit time and the velocity at 1 AU both with the output of the numerical code ENLIL and the drag-based analytical model. For this work on heliospheric propagation a large number of model runs were performed in order to investigate to what extent variation of the near Sun input parameters affects the model output at L1, i.e. the modelled near Earth solar wind parameters. A publication on this work will be submitted shortly.
At DTU there is also established collaboration with partners in MTA-KFKI-RMKI and U Oulu. For two magnetic storm events specifically the three focus parameters were investigated: Dst/Dcx, magnetopause stand-off distance and auroral boundary location. Also, there is a close collaboration with the CCMC at NASA and with other SOTERIA partners in investigating/validating state-of-the-art physics based model performance during space weather events, where the special attention was paid to model the performance with respect to the selected WP4 focus parameters. In this regard, three different models have been used. ENLIL for modelling CME propagation through the heliosphere, and BATSRUS coupled with RCM as well as with Fok radiation belt model for modelling magnetospheric effects.
At MTA-KFKI-RMKI the solar energetic particle events of 25 July 2004, 28-29 October 2003 (Halloween events), and 19 May 2007 were analyzed using SOHO LION and EPHIN as well as STEREO IMPACT SEPT energetic proton data. The time profiles were modeled with the SOLPENCO code (0.125 to 32 MeV) which reproduced the flux enhancements near the shock reasonably well in the first two cases (3 events). The best model parameters were obtained from fits to the profiles. To obtain profiles with extremely high shock speeds one needs to make extrapolations outside of the speed range used in the model.
At U Oulu the occurrence of solar X-ray flares is analyzed using an improved treatment for finding the rotation parameters of solar active longitudes. Results show larger longitudinal asymmetries than earlier, and give strong evidence for two active longitudes in either hemisphere. It is found that active longitudes rotate faster in the northern hemisphere and that the different classes of flares (C,M and X) are connected to the same longitudes. Related publication in under review.
Also, the temporal and spatial distribution of coronal mass ejections is analyzed using both the CMEs observed manually and by automated detection methods (CACTUS by ROB). Despite large differences between the two data sets there are common, systematic features in the CME occurrence which also give evidence for active solar longitudes. Related publication (UOulu and ROB) is under work. UOulu has also calculated the local Dst/Dcx disturbances and the separate current contributions to the Dst/Dcx indices for the two WP4 storms (25 July 2004 and 28-29 October 2003). These results will be used to study the magnetospheric effects, both globally and locally, to the respective solar drivers, and to compare them with state-of-the-art models. This will be conducted in collaboration with DTU and Hvar. The role of the ROB will be to test the new methods developed within SOTERIA within an actual operational space weather forecast center context. This contribution is currently in stand-by, as this role comes necessarily after the development of the new methods.
IEEA is working on the software dedicated to predicting ionospheric scintillations. The geophysical parameters (solar spot number, magnetic activity, …) are taken as an input and produce as an output a probability of occurrence of scintillations in dependence on the operating frequency, local time, season and the geographic coordinates. Analysis of several data sets was performed concurrently to cross check the results of the model. The collaborative research of NOVELTIS and IEEA is directed to the improvement of ionospheric scintillation modelling with IEEA by using DA method. Discussions have been engaged to define the method. NOVELTIS is also working jointly with a partner DTU on computing and analysing TEC enhancements in the auroral region, whereas TEC maps were produced for each selected solar event.
List of the people involved in this deliverable: KU Leuven - Giovanni Lapenta, Marina Skender, Andrey Divin and Maria Elena Innocenti; Hvar - Bojan Vrsnak, Tomislav Zic and non-SOTERIA member Dijana Vrbanec; DTU - Susanne Vennerstrom and Thea Vilstrup Falkenberg; U Oulu - Kalevi Mursula, Timo Asikainen and Ilpo Virtanen; MTA-KFKI-RMKI: Karoly Kecskemety and Peter Kiraly; IEEA - Yannick Beniguel and Jean-Pierre Adam; NOVELTIS: François Crespon, Eric Jeansou and Chafih Skandrani; DTU - Susanne Vennerstrom and Thea Vilstrup Falkenberg; ROB – David Berghmans.
