Proceedings of IAU Symposium 233,
St. Petersburg 2004, submitted
Solar forced variations of terrestrial high energy
particle environment as seen by RESIK PIN detectors on CORONAS-F
1Space Research Centre, Polish
Academy of Sciences, Kopernika 11, 51-622 Wroclaw, Poland
e-mail: mk@cbk.pan.wroc.pl
2IZMIRAN,
Russian Academy of Sciences
Abstract
RESIK is the bent crystal spectrometer aboard the CORONAS-F
satellite. It is equipped with four PIN diode detectors. These
detectors were used in order to detect background counts due to
energetic particle contamination present within polar regions and
SAA belts. At altitudes above 300 km (Coronas-F altitude is about
500 km) the population of charged particles trapped by the Earth's
magnetic field consists of protons (energies between 100 keV and
several hundred MeV) and electrons (energies between few tens of
keV and 10 MeV). The construction of RESIK PIN diode detectors
allows to sense particles with the energy above 1 MeV. We
present diagrams illustrating the coupling of the Coronas-F
particle environment and selected proxies of solar activity. The
data shown have been collected during initial phase of mission.
1 Introduction
Variations in certain manifestations of solar activity such as
solar wind and/or transient phenomena like interplanetary magnetic
fields boundary crossings, erupting filaments, coronal mass
ejection, presence of equatorial coronal holes, may cause
disturbances in the state of Earth magnethosphere. The effects of
these disturbances are especially noticeable in polar regions and
possibly in the South Atlantic Anomaly (SAA). The SAA is the
region of a lower geomagnetic field extending above Brazil and
south Atlantic. In this zone, which extends down to low Earth
orbit (LEO) altitudes, the energetic particle flux is
significantly increased. In the SAA region the LEO satellites
including ISS and shuttles, are exposed to increased levels of
harmfull radiation. Polar cap regions with increased energetic
particle population are also dangerous to the unmanned satellite
systems. In this paper we analyse the varaiation in the particle
environment in the auroral cap regions and SAA from the records of
RESIK PIN diode sensors placed aboard in order to detect regions
and times where/when the high voltage in RESIK proportional
detectors should be switched off. Signals from these PIN sensors
has been analysed aboard RESIK in order to switch-off the high
voltage from the primary large area proportional detectors
(measuring solar soft X-ray spectra) during passages through
regions of increased energetic particle density.
Figure 1:
Left: The correlation diagram showing direct correspondence between the
rates seen by RESIK PIN sensors and the rate measured by the MKL
instrument. Centre: Plots of time variation of the PIN
sensor rates in the three regions of geomagnetic environment (North
and South polar caps and SAA) atop variations of GOES-10
X-radiation fluxes for the corresponding times in April-May 2002.
Right: Map showing the location of regions with increased
rates of the PIN sensors as determined from data collected over
May 2002.
2 Observation and results
The PIN sensors have been collecting data from September 2001 to
September 2003. From various available, we have found the best
correlation (R = 0.97, left part in the Figure) between PIN sensor
rates and MKL proton rates for high-energy protons (Ep > 26 MeV). Time variations of RESIK PIN fluency, as considered in
three separate regions of the magnetosphere (South polar oval, SAA
and North polar oval regions) are shown in the middle. The map in
the Figure shows areas of higher PIN rates as seen in May 2002.
In both polar regions, increased PIN rates are distinctly observed
to follow certain flares seen on the GOES soft X-ray plot.
Th SAA region shows up also some activity-associated variability
also, however with a much smaller amplitude. Flare related
increases in the SAA rates are observed to be much more delayed in
time with respect to polar regions’ increases. Overall observed
fluctuations in the particle rate recorded within SAA are
approximately by an order of magnitude, with the peak levels few
times the average rate. This observed significant SAA changes
affect all LEO satellites including ISS.
Acknowledgements
RESIK (PI - J. Sylwester), is a common project
between NRL (USA), MSSL and RAL (UK), IZMIRAN (Russia) and SRC
(Poland). M.K., Z.K., J.S. and W.T. acknowledge support from grant
2.P03D.002.22 of the Polish Committee for Scientific Research.
References
-
Martin V. Zombeck 1982
Handbook of Space Astronomy and Astrophysics , 154-159.
File translated from TEX by TTH, version 2.25.
On 16 Sep 2004, 08:49.
