Assume that Suomi 100 Cubesat is at approximately above Helsinki.
Use the IRI web service (http://omniweb.gsfc.nasa.gov/vitmo/iri2012_vitmo.thml) and plot the following
profiles up to 1000km altitude by using a linear altitude scale:
i)
ii)
Electron density [m-3]
Electron temeprature [K]
for these three UTC times:
A) 2002/09/21, 10:00 UTC
B) 2008/09/21, 10:00 UTC
C) 2008/09/21, 00:00 UTC
Use the maximum electron density values and derive the corresponding electron plasma frequency at all
three cases.
In which of these case(s) you anticipate Suomi 100 Cubesat AM readio to detect 5 MHz radio wave signals
from an AM radio station when the satellite is at the altitude of 500 km?
2002/21/09 10:00 UTC
2008/21/09 10:00 UTC
2008/21/09 00:00 UTC
What might be the possible reason(s) why the maximum electron density value is the largest in the case A)
and smallest in the case C)?
Assume that you are designing Aalto-2 Langmuir probe. What kind of relevant information the profiles
which you derived above give to you?
Assume that you are controlling an ionosonde at Helsinki at those three times. What frequency range you
would use and why in order to make useful ionosphere F layer measurements?
Electron plasma frequency at 500 km altitude:
a) ωpe = sqrt(nee2/mε0) = sqrt(2.5*10^11 ( 1.6*10^-19)^2 / 9.11*10^-31 8.854 *10^-12) = 8.90*10^6
MHz
b) ωpe = sqrt(nee2/mε0) = sqrt(5*10^10 ( 1.6*10^-19)^2 / 9.11*10^-31 8.854 *10^-12) = 3.98*10^6
MHz
c) ωpe = sqrt(nee2/mε0) = sqrt(1.5*10^10 ( 1.6*10^-19)^2 / 9.11*10^-31 8.854 *10^-12) = 2.18*10^6
Mhz
The signal has to exceed electron plasma frequency in order to propagate. This is not achieved in the case A,
but with case B and C communication could be possible. This is highly likely in case C.
There is a 10 hour difference in daily timescales between case A and case C. Furthermore they have been
taken during different times of the solar cycle, with case A being closer to solar maximum and B and C closer
to solar minimum.
The profiles allow us to study the relation between electron density, electron temperature and height during
different times of the day ant the solar cycle.
The ionosphere F layer is from about 150km to 500 km, there are two different layers during the day called
F1 and F2. For the cases A, B and C, a frequency range of 10 MHz to 0.9 MHz would be appropriate.
2) Neutral atmosphere (max 2 points)
2.1 Use the web tool (http://ccmc.gsfc.nasa.gov/modelweb/models/msis_vitmo.php) and derive the
following altitude profiles up to 1000 km above Helsinki:
i. Atomic Oxygen (O), cm-3
ii. Nitrogen (N2), cm-3
iii. Oxygen O2, cm-3
iv. Neutral Temperature, K
at these two times:
A) 2002/09/21, 10:00 UTC
B) 2008/09/21, 10:00 UTC
2002/09/21, 10:00 UTC
2008/09/21, 10:00 UTC
2002/09/21 10:00 UTC
2008/09/21 10:00 UTC
2.2 Derive the values of these four parameters at altitude 500 km, where Suomi 100 CubeSat will be
located. What is the most dominant neutral particle species? Based on Tuesday’s lecture and lecture slides,
what kind of hazard do fast moving oxygen atoms cause to your instrument and to the spacecraft?
The most dominant particle species at 500 km is atomic oxygen. Fast moving oxygen atoms can cause
spacecraft charging and erosion, atmospheric variablity can furthermore cause atmospheric drag or more
correctly increase atmospheric drag.
3) Topic: A modern web tool and solar activity (max 1 point)
The web tools used above in 1. and 2. are useful tools to obtain important data from the internet which you
can use in your instrument design and the data analysis.
However, it is difficult to remember numerous web addresses, look sometimes very low quality plots
provided by the web service and to combine manually different data from different sources.
Would it not be useful if there would be a single web site from where you could get many kinds of data,
combine data, analyze data and make illustrative and clear plots?
Yes, it would be, so let’s start to use SubstormZoo (https://www.substormzoo.org/).
First of all, make an account to SubstormZoo if you have not already.
3.1. Plot F10.7 values with SubstormZoo starting from the year 1998.
i. Use the plot and give an educated guess for the year when the solar activity was (i) high
and (ii) low
ii. Based on the lecture notes, how long time you would assume that Suomi 100 CubeSat,
which is at an altitude of ~500km, would remain in the space in your high and low activity
times. (A simplified assumption: assume that the activity of the Sun would remain unchanged
during the whole misson).
i.
ii.
The radio flux seems to have quite clear maximum during 2000-2002, and a slightly smaller one
during 2014-15. Minima are present at 1996 and 2008-2009
As per the table in lectures slides, almost 30 years at minimum, 3 years at maximum, assuming
constant values. This is of course quite a simplification, the truth would be somewhere in
between.