Post on 17-Jan-2016
description
IImportance Of mportance Of Very Low Frequency Very Low Frequency
Radio Signal DataRadio Signal Data Registered By Registered By
VVLFLF-receiver-receiver SystemSystem
A. Nina, V. Čadež and V. SrećkovićInstitute of Physics, Belgrade, SerbiaInstitute of Physics, Belgrade, Serbia
Astronomical ObservatoryAstronomical Observatory, Belgrade, Serbia, Belgrade, Serbia
ContentsContents• Ionosphere
• VLF signals – “ionospheric probes”VLF signals – “ionospheric probes”
• Importance of creating a database for Importance of creating a database for studying the ionosphere and its applications studying the ionosphere and its applications in technical and scientific researchin technical and scientific research such as:
--detection of different events by VLF signalsdetection of different events by VLF signals
-ionospheric diagnostics-ionospheric diagnostics
-study of physical and chemical processes -study of physical and chemical processes
IntroductionIntroduction
• Terrestrial ionosphere
• Methods of investigation
• Our study: low ionosphere
VLF signals – VLF signals – “ionospheric probes”“ionospheric probes”
• VLF wave propagation
• Advantages: - continual emission, - large area involved
for analyses, - international
collaboration: AWESOMEAWESOME,
AbsPALAbsPAL, SAVNETSAVNET, AARDDVARKAARDDVARK
• Belgrade VLF station
Significance of low Significance of low ionospheric study ionospheric study
• ScienceScience - detection of different pure natural and man-induced events - ionospheric diagnostics - study of physical and chemical processes
• TelecommunicationsTelecommunications - radio communications, - planned networks of mobile communication satellites, - high precision applications of global navigation satellite
systems, etc.• Explanation of application our database in scientific
research and, consequently, in prediction of possible problems in the telecommunications
Importance of databaseImportance of database• Processes in the ionosphere are: -very complex - time- and space variable
• Experiment: practically impossible to exactly simulate conditions in
particular cases
• Theory: no real time data available for all necessary parameters
needed for theoretical analyses
• Statistics: requires the existence of a database that can be used to
analyze the ionosphere
Detection of eventsDetection of events• Sun:
- regular variation
- transient variations
• Outer space
• Earth:
- in the atmosphere
- in the lithosphere
pure natural
man-induced
21:30:00 21:30:20 21:30:40 21:31:00
58.0
58.5
59.0
59.5
-130
-125
-120
-11521:30:00 21:30:20 21:30:40 21:31:00
NAA
Am
plit
ud
e (d
B)
NAA
GRB December 27th, 2004
Ph
ase
(o)
Time (UT)
00:00 04:00 08:00 12:00 16:00 20:00 24:0010
20
30
40
10
20
30
40
10
20
30
40
10
20
30
4000:00 04:00 08:00 12:00 16:00 20:00 24:00
Time (UT)
Mart 21, 2011 Mart 22, 2011 Mart 23, 2011
Am
plitu
de
(d
B)
December 21, 2010 December 22, 2010 December 23, 2010
September 22, 2010 September 23, 2010 September 24, 2010
Jun 13, 2010 Jun 19, 2010 Jun 20, 2010
DHO
HESSI
06:00 08:00 10:00 12:00 14:00 16:000
5
10
15
20
10
20
30
0
5
10
15
2006:00 08:00 10:00 12:00 14:00 16:00
Am
plit
ude (
dB
)
G1
NAA
DHO
16_February_2011
1-8A GOES-15
Inte
nsi
ty (
10-6
W/m
2 )SGR 1806-20
00:42 00:44 00:46 00:48
-170
-165
-160
-155
18
19
20
21
Ph
as
e (
o)
Time (UT)
GQD
Am
plitu
de
(d
B)
GQD
Ionospheric diagnosticsIonospheric diagnostics
• The case considered: Solar flare February 18th, 2011
• Recorded data: - GOES-15 satellite - Belgrade AWESOME receiver - DHO (Germany) transmitter (23.4 kHz)
• Theoretical model: Wait’s model of ionosphereWait’s model of ionosphere • Numerical program for simulation
VLF signal propagation: LWPCLWPC (Long-Wave Propagation Capability)
14:05 14:10 14:15 14:20 14:25
52
54
56
58
60
24
26
28
30
10-6
10-5
14:05 14:10 14:15 14:20 14:25
Time (UT)
rec (
o)
Are
c (d
B)
I(W
/m2 )
GOES-15 fit
14:05 14:10 14:15 14:20 14:25
109
1010
1011
N (
m-3)
Time (UT)
Physical and chemical processes Physical and chemical processes
(preliminary results)(preliminary results)
G(t) – electron gain rate
L(t) – electron loss rate
Upper half of D region:
tLtGdt
dN
)()()( 00 tItIKPtPtG sss
tNttRtL eff2
P(t) – photo-ionization rateR(t) – recombination rateI(t) – radiation flux by satelliteαeff – effective recombination coefficientKs – coefficient (dependent on energy interval of data registered by satellite)
14:05 14:10 14:15 14:20 14:25
0
1x1010
2x1010
3x1010
4x1010
5x1010
6x1010
dN
/dt
(m-3s-1
)
Time (UT)
total P R
I II III
I - Quasi equilibrium regime
II - Photo-ionization regime
III - Recombination regime
ConclusionsConclusions• Applications of low ionospheric
investigations in science and information technologies
• Research of low ionosphere by VLF waves
• Importance of VLF radio signal data registered by receiver systems