scostep 2010 (stp12) - Leibniz-Institut für Atmosphärenphysik an der ...

STP12 Abstracts
Berlin, 12 - 16 July 2010
SCOSTEP Symposium 2010
Results from the C/NOFS Satellite obtained during the Current Deep Solar Minimum
Basu Sunanda , Basu Santimay
Boston College, USA
The multi-instrumented C/NOFS (Communication Navigation Outage Forecasting System)
satellite was launched on April 16, 2008 with 13 degree orbital inclination to characterize and
forecast outages in transinospheric communication systems in the equatorial region. The
satellite launch corresponded to the deepest solar minimum period and its perigee of even 400
km was found to be inadequate at times for the forecast of the ionospheric turbulence and
their deleterious effects on trans-ionospheric communication systems. However, the several
on-board instrument packages comprised of a planar Langmuir probe, vector electric field
instrument, ion velocity monitor, GPS occultation sensor and a multi-frequency radio beacon
have provided many new results. Only the neutral wind meter has not been able to operate
during this extreme quiet solar condition, but is expected to provide results when the solar
flux exceeds 100 units.
Observations by various investigators will be presented Measurements using the ion velocity
meter reported that the altitude extent of the ionosphere is significantly smaller than the
present reference models would predict for these levels of solar activity. Moreover they found
the transition height between O + and H + to reside near 450 km at night and at that time, this
unusually contracted ionospheric shell around the equator had a temperature of only 600 K.
Ion density data observed with the Planar Langmuir Probe (PLP) also yielded new findings,
such as deep plasma depletions at sunrise and broad plasma decreases at nighttime. As far as
plasma bubbles are concerned, several groups have analyzed the high resolution data of PLP
plasma density and obtained spectral characteristics from 10km to 100 m. They suggested the
possibility of two-slope spectra with a break at 70m scale length, which may be related to the
long-lasting solar minimum condition. We have utilized the PLP data in conjunction with
several ground-based instruments in the Jicamarca sector and have found great changes in the
low-latitude electrodynamics from day-to-day. The interpretations of our C/NOFS
ionospheric irregularity observations were greatly facilitated by the TEC data from the Low
Latitude Ionospheric Sensor Network (LISN) and the incoherent scatter radar and Digisonde
at Jicamarca.