Solar energetic particles
Modelling of gradual SEP events: an example
The movie below shows the modelling of the evolution of the
interplanetary shock and the cobpoint, and the fitting to the proton
intensity-time profiles measured at 1.0 AU during the gradual proton
13 December 2006.
The right panel shows:
The left panel shows:
- The first snapshot shows the radial velocity contours of the
background solar wind, simulated from 1.03 solar radii to 1.02 AU (from
dark blue to light blue, as shown in the colour bar at the right). Note
that the solar wind reaches its stationary speed at ~40 solar radii.
- Succeeding snapshots: The evolution of the MHD simulated
interplanetary shock, propagating on top of this solar wind, from 4
solar radii to ~1.0 AU (L1 point, black dot). The maximum shock velocity
occurs at the nose of the shock, in the negative X-axis direction
(colour coded from dark red to light green).
- The location of the cobpoint at the front of the shock (red
point). The first cobpoint occurs about half an hour after the launch of
the driven shock, at ~5 solar radii, then it slides clockwise along the
shock front as the shock expands out warding the Sun.
- The interplanetary magnetic field line (white trace) that at each
time step connects the observer at L1 with the front of the shock. This
field line is extracted from the MHD simulation: it results in a Parker
spiral form upstream of the shock and it bends in the post shock sheath.
- Three measured proton intensity-time profiles (coloured dots) at
L1, the lower energy channel is from the SOHO/ERNE instrument and the
other two from the STEREO-A/HET telescope.
- The vertical green line marks the shock passage at L1.
- The white lines represent the synthetic flux profiles obtained
from the fitting using the shock-and-particle model. This model assumes
that the shock-accelerated particles are injected onto the
interplanetary magnetic field line connecting with the observer at the
In this event, high-energy particles are observed shortly after the
first cobpoint is established, thus the first injection of shock
accelerated particles occurs when the shock is still close to the Sun.
The lower energy profiles start increasing later than that because of
the presence of a background population of particles, but mainly due to
their smaller velocity and due to particle propagation effects along the
interplanetary magnetic field.
Note that the high energy proton flux peaks a few hours after the onset
of the event, while the low-energy intensity peaks at the shock arrival.
Thus, indicating that the shock is efficient at accelerating high energy
protons when it is close to the Sun, but as it propagates away, it
becomes only efficient at accelerating low-energy particles.
If you use this movie, please refer to:
Aran A., N. Agueda, C. Jacobs et al. 2011, American Geophysical Union,
Fall Meeting 2011, abstract
The research leading to the modelling performing this movie received
funds from the European Space Agency under the Solar Energetic Particle
Environment Modelling (A href="http://sepem.aeronomie.be/">SEPEM)
Project (ESA-ESTEC/Contract No 20162/06/NL/JD). The work at the
University of Barcelona was partly funded by the project AYA2010-17286
of the Spanish Ministerio de Ciencia e Innovación and at KU
Leuven, this research was partly funded by the KU Leuven project
GOA/2009-009, FWO project G.0729.11 and 06260 and PRODEX project C90205.
Angels Aran and Blai Sanahuja, 2012.
- Cobpoint: Heras, A.M.,
B. Sanahuja, D. Lario, Z.K. Smith, T. Detman and M. Dryer,
Three low-energy particle events: Modeling the influence of the parent
interplanetary shock, Astrophys. J., 445, 497–508, 1995.
- Shock-and-particle model:
Lario, D., B. Sanahuja and A.M. Heras,
Energetic Particle Events: Efficiency of Interplanetary Shocks as 92 keV < E < 100 MeV Proton Accelerators, Astrophys. J., 509, 415–434, 1998.
- Its applications:
- Aran, A., B. Sanahuja and D. Lario,
SOLPENCO: A solar particle engineering code, Adv. in Space Res., 37, 1240-1246, 2006.
- Aran, A.,
Synthesis of proton flux profiles of SEP events associated with
interplanetary shocks. The tool SOLPENCO, PhD Thesis, University of
- Aran, A., D. Lario, B. Sanahuja,
R.G. Marsden, M. Dryer, C.D. Fry and S.M. McKenna-Lawlor,
Modeling and forecasting solar energetic particle events at Mars:
the event on 6 March 1989, A&A, 469, 1123–1134, 2007.
- New shock-and-particle model:
Aran, A., C. Jacobs, B. Sanahuja, D. Lario,
S. Poedts, R. Rodríguez-Gasén and R.G. Marsden,
A Shock-and-Particle model for the prediction of gradual proton events
up to <200 MeV, A&A, Submitted, 2012.
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Last update: 24 April 2013