ForbMod (EU-H2020 Marie Curie Sklodowska Actions)

Forbush decrease model for expanding CMEs affecting Earth and Mars

  • Run-Time: 2017-2019
  • Project Description: Galactic cosmic rays have a major impact on interplanetary space and planetary surfaces and are of outmost importance for space travel. They are modulated by the activity of the Sun – during high solar activity their number is reduced. On short time scales of several days, the reduction in galactic cosmic rays, so-called Forbush decreases, are observed, which are caused by the most violent eruptions in the solar system – coronal mass ejections (CMEs, a.k.a. solar storms). Project “Forbush decrease model for expanding CMEs (ForbMod)” aims to unravel how galactic cosmic rays are influenced by solar storms in the inner solar system (Sun to Mars) by developing a new model and utilizing a number of spacecraft and planetary observation, including those by Mars Curiosity Rover. Our current understanding is that the CMEs are actually magnetic structures disconnected from its surrounding so that the galactic cosmic rays can only enter inside trough random walk, i.e. diffusion. Since diffusion is slow compared to the speed of initially empty CME while traveling trough the interplanetary space, during the passage of the CME over our instruments we observe Forbush decreases. We intend to supplement our current understanding of this process by including some known observational facts about CMEs, which were greatly improved by spacecraft measurements in the past two decades. For the first time we will use CME observations to constrain the Forbush decrease model and take into account that CME evolves while traveling trough interplanetary space. In addition, for the first time we will compare modeling results to measurements not only taken from Earth, but also from Mars, recently available with the Mars Curiosity Rover. This modeling and multi-spacecraft observational approach will allow testing unanswered hypotheses on the FD properties. Thus the project will generate new knowledge on the properties of galactic cosmic ray decreases by solar storms, which is relevant for space weather, human spaceflight and planetary and exoplanetary atmospheres. [Download full proposal]
  • Team: Mateja Dumbovic (PI), Manuela Temmer
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  • Scientific publications 
  • Presentations
  • Public Outreach  
Visualization of ICME driving a shock and a corresponding Forbush decrease Visualization of ICME driving a shock and a corresponding Forbush decrease when ICME is encountered head-on (A) and at the flank (B) (Richardson & Cane, 2011, SolPhys); b) in situ measurements of an ICME in September 1998 (panels 2-6 show in descending order: plasma density, temperature, and speed, magnetic field strength and fluctuations) and a corresponding two-step Forbush decrease (1st panel), where shock/sheath region is colored blue and magnetic ejecta region is colored red (adapted from Dumbović et al., 2012);
 
Visualization of ICME driving a shock and a corresponding Forbush decrease a) model assumptions based on Cane et al., 1995 (cylindrical, empty FR and perpendicular diffusion of particles marked by arrows); b) corresponding modeled cosmic ray count change during the passage of the FR (right) for different values of the parameter f, which depends on the diffusion coefficient, time, and FR radius;
PROOF-OF-CONCEPT FIGURE
a) alignment of Earth and Mars at April 5th 2014; b-d) GCS reconstruction of Earth-directed CME on April 2nd 2014 for STEREO B/COR1 (b), STEREO A/COR1 (c) and SOHO/LASCO C2(d); e) in situ measurements with Wind spacecraft at L1 showing sheath (start marked by a dashed line) and FR (start marked by a solid line); f&g) corresponding FD measurements (start marked by a solid line) with ground-based neutron monitor measurements from the South pole on Earth and ground-based measurements from MSL/RAD on Mars; h) diffusion model FD for diffusion time 85h, diffusion coefficient 1019cm2s-1, and FR radius 0.15 AU without expansion (black line) and with additional 30% contribution from expansion estimated based on the FR density decrease given in Bothmer & Schwenn, 1998 (blue line);