Visualization and Analysis of
Particle Spectra
Octav Marghitu (1, 2) and Berndt Klecker (2)
(1) ISS Bucharest, (2) MPE Garching
The tasks listed below complement the lectures Principles of particle
spectrometry and Interpretation and modeling of particle spectra.
After selecting two Cluster orbits, one in summer and one in winter, CIS ion
data are used first to identify the big magnetospheric domains. Next, ion data
from the two orbits are explored in detail, by examining moments, spectrograms,
and distribution functions. The purpose of this closer investigation is twofold:
to illustrate the physical use of the particle data, and to point out instrumental
issues that require precautions.
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1. Orbit plots by Cluster
Science Data System
a. Go to the Cluster Science
Data System, CSDS,
and select the plot type Orbit /
Configuration Plot.
b. Plot a summer Orbit, by
selecting the date September 23, 2001 (for this type of plot the exact time is
not important).
c. Plot a winter Orbit, by
selecting the date February 3, 2003.
d. When do you expect Cluster
to encounter the solar wind and when the plasma sheet?
2. Ions overview by using the
Cluster/CIS web site
a. Go to the CIS site and select Data Plots / Public Access Spectrograms.
b. Go to the spectrograms for
Sep. 22, 2001, and identify the apogee time.
i.
Follow Cluster 1 along a complete orbit, starting at apogee, and identify
time intervals spent by Cluster in the plasma sheet, lobe, cusp, radiation
belt.
ii.
What can you say about the relative ratio of O+ / H+
density in the lobe versus plasma sheet? What feature in the spectrograms can
be associated with the (large scale) variation of this ratio?
iii.
List the features that you do not understand.
c. Go to the spectrograms for
Feb. 2, 2003, and identify the perigee time.
i.
Follow Cluster 1 along a complete orbit, starting at perigee, and identify
time intervals spent by Cluster in the radiation belt, auroral region, lobe,
cusp, magnetosheath, solar wind.
ii.
Give at least one example of signature in the data which does not have a
natural origin, but is related to a change in the instrument setup (e.g. a mode
change).
iii.
List the features that you do not understand.
3. Closer analysis of a time
interval on Sep. 23, 2001, by the cl
program.
a. Open three ’Terminal’ windows. Go
to the directory /mnt/share/particles/config_cl and start three
instances of the program by typing cl.
Click on ’Ok’ in the startup configuration window.
b. Plot a predefined set of CIS
spectrograms and moments, by loading in each cl (with File/Open) one of the configuration
files STIINTE_20010923_CODIF_H, STIINTE_20010923_CODIF_O, and STIINTE_20010923_HIA. For a study of the O+ outflow during the time
interval covered by these files you can take a look at Bouhram
et al, 2004.
c. Compare the CODIF O+ and H+ plots.
What prominent differences do you see? What is the time scale of the O+
outflow?
d. Compare the CODIF H+ and HIA
(all ions) density during the cusp crossing. What could be the reason for the
difference in density?
e. Compare the CODIF O+ and HIA
(all ions) Vz velocity between 12:00 and 12:30. The two velocities appear to be
different. What is their ratio and what do you think is the explanation for the
difference?
f.
Plot a predefined distribution function, by loading the configuration file STIINTE_20010923_CODIF_O_DF.
What is the approximate energy of the O+ beam seen in the plot? (Hint: a H+ ion
moving with 440 km/s has an energy of about 1 keV) Is the energy consistent
with the trace in the spectrogram?
g. What could be the
acceleration mechanism of the beam ions?
4. Closer analysis of a time
interval on Feb. 2, 2003, by the cl
program.
a. Restart the three cl
sessions.
b. Repeat the procedure 3.b for
the configuration files STIINTE_20030202_CODIF_H,
STIINTE_20030202_CODIF_O, and STIINTE_20030202_HIA.
c. Compare the HIA and CODIF H+
densities at the beginning of the interval. What could be the reason for the
large difference?
d. Note the peaks in the O+
density and velocity between 16:30 and 16:35. Are these peaks compatible with
an ion beam of ionospheric origin? (Hint: compare the velocity panel with the
magnetic field panel).
e. Plot the O+ distribution
function close to the first peak in density / velocity, by loading the
configuration file STIINTE_20030202_CODIF_O_DF. What is the energy of
the beam? (see the hint at 3.f) Explore the time variation of the distribution
function by clicking on ‚’Time <=’ and ‚’Time =>’ (note
that in this case the particles are counted every second spin, therefore every
second distribution is empty). What is the time scale of the beam? How does it
compare with the beam at 3.f ?
f.
Plot the H+ distribution function at the time of the O+ beam, by loading
the configuration file STIINTE_20030202_CODIF_H_DF. Do you see a beam
feature in the H+ data? At what energy? Can you imagine an acceleration
mechanism consistent with both the O+ and H+ ions?
g. How wide in latitude can be
the source region of the beam ions? Hint: the satellite velocity is about 5
km/s; for the mapping to the ionosphere compare the magnetic field in the plots
4.b with the value at 100 km, of about 50,000 nT.