Drag-Based Ensemble Model (DBEM):
probabilistic model for heliospheric propagation of CMEs

Important note: This version of DBEM is mainly for testing purposes. Method with the synthetic measurements may produce the unreliable results in the case of hit/miss ratio, if the number of synthetic measurements is small (m < 15) resulting in bad representation of the normal distribution. For this purpose, we developed DBEM version 2 with slightly different method that uses the randomly generated samples determined by normal (Gauss) distribution as input.

CME date
Date when CME leading edge is located at radial distance R0.
Dates are limited by available ephemeris data:
from 01-01-1961 to 30-11-2049.
Note: If you are using STEREO A (STA) or B (STB) target then by CME date is limited from 27-10-2006 (launch of the satellites).
 CME date (at R0):
CME time
Time in UTC when CME leading edge is located at radial distance R0.
 CME time in UTC (at R0):
h min
Drag gamma parameter & types of CMEs
Slow CMEs (type 'stealth'): v < 500 km/s
Normal CMEs: 500 km/s < v < 1000 km/s
Fast CMEs: v > 1000 km/s
Valid values for user defined gamma are:
0.001 ×10-7 km-1γ ≤ 100 ×10-7 km-1.
 Drag parameter, γ (depending on CME speed):
 ×10-7 km-1
Solar wind speed
The background constant solar wind speed, w. The current value of solar wind speed is calculated with solar wind forecast model (University of Graz) and it is valid only for a current date and next 4 days.
Valid values are:
200 km/s ≤ w ≤ 800 km/s.
 Solar wind speed, w =
km/s  (current: 327 km/s)   Current solar wind speed forecast
(2020-03-31 03:42 - 2020-04-04 03:42)

mean w: 327 km/s
median w: 323 km/s
min w: 306 km/s
max w: 363 km/s
The solar wind speed forecasting is based on an empirical relation linking the area of coronal holes observed in remote sensing EUV data and high speed streams measured at Earth after about 4 days.
For more information visit Solar wind forecast website:
CME starting radial distance
The distance of CME leading edge in coronagraph image on selected date and time. Distance should be given in solar radius units (rSun = 6.955×105 km).
Valid values are: 1 rSunR0 ≤ 60 r Sun.
  CME starting radial distance, R0 =
Starting speed of CME
The CME starting speed, v0 is the speed of CME leading edge located at R0.
Valid values are: 50 km/s ≤ v0 ≤ 5000 km/s.
 Starting speed of CME, v0 (at R0) =
CME's angular half-width
CME's angular half-width λ is based on coronagraphic observations.
Valid values are: 0° < λ < 90°.

Coronograph observation - example with lambda
 CME's angular half-width, λ =
Longitude of CME source region
Longitude of CME source region is CME propagation direction determined on observation of eruptive phenomena on the solar disc.
Valid values are: -180° < φCME < 180°.

DBM cone geometry and phi_CME
 Longitude of CME source region, φCME =
Model will calculate the results regarding to the selected target on the ecliptic plane. Target distance and Earth-target heliocentric angular separation for selected object will be automatically taken from ephemeris data.
Note: STA refers to STEREO A and STB to STEREO B satellite.
 Select target:

The Drag-Based Ensemble Model (DBEM)

Version: 1.3 (25 February 2018)


From 15 November 2017 DBEM has performed 877 successful calculations.
Based on DBM version:
  • with constant solar wind (w) and gamma parameter
  • initially presumed cone geometry
  • segmental expansion
DBM & DBEM code is developed in Python 3.5


The description of DBM calculation in pdf format is available here

Python & PHP code:

Jaša Čalogović


Jaša Čalogović [1,2], Mateja Dumbović [1,2], Bojan Vršnak [1], Manuela Temmer [2], Tomislav Žic [3],
Astrid Veronig [2], Isabell Piantschitsch [2]
[1] Hvar Observatory, Faculty of Geodesy, University of Zagreb, Croatia
[2] Institute of Physics, University of Graz, Austria
[3] Faculty of Engineering, University of Rijeka, Croatia

List of publications:

  • Dumbović, M., Čalogović, J., Vršnak, B. et al. (2018): The Drag-based Ensemble Model (DBEM) for Coronal Mass Ejection Propagation, The Astrophysical Journal, 854, 2, pp180, DOI: 10.3847/1538-4357/aaaa66.
  • Žic, T., Vršnak, B., Temmer, M. (2015): Heliospheric Propagation of Coronal Mass Ejections: Drag-Based Model Fitting, Astrophysical Journal Supplement Series, 218, 2, DOI: 10.1088/0067-0049/218/2/32
  • Vršnak, B., Temmer, M., Žic, T. et al. (2014): Heliospheric Propagation of Coronal Mass Ejections: Comparison of Numerical WSA-ENLIL+Cone Model and Analytical Drag-based Model, Astrophysical Journal Supplement Series, 213, 2, DOI: 10.1088/0067-0049/213/2/21
  • Vršnak, B., Žic, T., Vrbanec, D. et al. (2013): Propagation of Interplanetary Coronal Mass Ejections: The Drag-Based Model, Solar Phys., 285, 2, pp295-315: DOI: 10.1007/s11207-012-0035-4
  • Vršnak, B., Žic, T., Falkenberg, T. V. et al. (2010): The role of aerodynamic drag in propagation of interplanetary coronal mass ejections, Astronomy and Astrophysics, 512, A47, DOI: 10.1051/0004-6361/200913482
  • Vršnak, B., Vrbanec, D., Čalogović, J. (2009): The role of aerodynamic drag in dynamics of coronal mass ejections, Proceedings of the International Astronomical Union, 257, p. 271-277, DOI: 10.1017/S1743921309029391
  • Vršnak, B., Žic, T. (2007): Transit times of interplanetary coronal mass ejections and the solar wind speed, Astronomy & Astrophysics, 472, p. 937–943, DOI: 10.1051/0004-6361:20077499
  • Vršnak, B. (2006): Forces governing coronal mass ejections, Advances in Space Research, 38, 3, DOI: 10.1016/j.asr.2005.03.090


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