Transcript Indices and proxies for space weather

SESSION 6
M. Messerotti1,2, M. Molinaro1
1INAF-Astronomical Observatory of Trieste,
IT
2Department of Physics, University of Trieste, IT
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The Sun as a radio noise source
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Effects of SRBs on Wireless Systems and GPSs
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TSRS and solar radio indices
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Multi-timescale analysis of the 5 Dec. 2006 SRB
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Conclusions
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PROXIES OF SOLAR DRIVERS
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Type I Bursts (magnetic topology changes)
Type II Bursts (propagating shocks; particle beams)
Type III Bursts (particle acceleration; particle beams)
Type IV Bursts (magnetic reconnection; acceleration)
Spikes (energy release fragmentation; acceleration)
Precursors (radio signatures preceding flares)
DIRECT SOURCE OF GEOEFFECTS
 Radio Flares (Very Intense Broad Band Radio Noise)
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The Sun is a radio source
 non-directional
 broad band
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Solar radio noise can
 increase by several orders of magnitude during outbursts
 persist at high levels for minutes to hours
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Enhanced solar radio noise can perturb
 HF communications (MIL!)
 Mobile communications (GSM, UMTS)
 Global Navigation Satellite Systems (GPS, GNSS)
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MULTIFREQUENCY
RADIOMETRY
LOW
TIME
RESOLUTION
GLOBAL
DIAGNOSTICS
FULL-DISK
SPATIAL
RESOLUTION
INDICES
RADIO
SPECTROGRAPHY
SOLAR
RADIO
PHENOMENA
HIGH
TIME
RESOLUTION
MULTIFREQUENCY
INTERFEROMETRY
SOURCE
SPATIAL
RESOLUTION
RADIO
HELIOGRAPHY
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LOCAL
DIAGNOSTICS
TIMINGS
COMPLEMENTARY
FOR SPW APPLICATIONS
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Bala et al. (2002):
 For a cellular base station operating at 900 MHz , the
equivalent solar flux (thermal noise=solar noise level) Feq 
960 SFU  more than twice the thermal noise power.
 For a base station operating at 2.4 GHz, Feq  6,000 SFU.
 The bit error rate (ber) changes rapidly with the S/N power
ratio. (0.75 dB change  10x in ber).
 Assuming an SRB effectivity threshold of 1,000 SFU, the
statistics over 4 decades indicates a probability of
interference every 10-20 days on average per year,
modulated by the solar cycle.

Lanzerotti et al. (2002); Nita et al. (2004)
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Cerruti et al. (2006):
 Observed reduced carrier-to-noise ratio in sunlit GPS
receivers over the duration of SRB (8,700 SFU RHCP  2.3
dB loss; 2005.09.07)
 Estimated L1 C/N0 fade of 3 dB and L2 C/N0 fade of 5.2 dB
for commonly used GPS antennas with a gain of 4 dBic,
from a SRB of 10,000 SFU
 SRB are a potential threat to life-critical systems based on
a Global Navigation Satellite System (GNSS): a 80,000 SFU
SRB can determine a 12 dB fade at L1 and a 26.2 dB fade
on the L2 channel  loss of lock in semi-codeless
receivers.

Possibly 4,000-12,000 SFU Chen et al. (2005)
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P. Kintner (Cornell University):
 Large number of receivers stopped tracking GPS
signal over the entire sunlit side of the Earth
 First quantitative measurement of the effect
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P. Doherty (Boston College):
 The 6 Dec SRB was the first one ever detected on the
civil air navigation system (WAAS, Wide Area
Augmentation System)
[see Cerruti et al., 2006]
Source: GPS Daily (http://www.gpsdaily.com)
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Multichannel Synoptic Graph
 - 1 s downsampled data
 - updated every 10 minutes
Solar Radio Indices Graphs
 - 1-min-average values
 - 1-min-max values
 - 1-min-ahead forecast
 - updated every 10 minutes
Solar Radio Indices Files
 - ASCII
 - Binary
 - FITS
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1-min-average and 1-min-max radio indices
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237, 327, 408, 610, 1420, 2695 MHz
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FLUX DENSITY & CIRCULAR POLARIZATION
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[ W / m2 / Hz ] & [ dBm / Hz ]
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Observed and 1-min-ahead Predicted Values
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Single polarization channels & sum of channels
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X
M
C
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TSRS observed maximum radio flux density significantly exceed reported levels:
S2695max = 10,391 SFU S1420max = 4,870 SFU
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Intense SRBs are a direct source of interference for
wireless communications and GPS systems
Published radio indices are not appropriate
descriptors as they provide incomplete information
1-min radio indices are inadequate as well → wrong
estimate of time over the threshold and polarization
Circular Polarization information is needed due to
the characteristics of radio systems
Real-time high time resolution analysis is a must for
properly evaluating the interfering effect on radio
systems
TSRS has the required features for this purpose
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