J/ApJ/710/L58 Coronal type II radio bursts in 2002 (Lobzin+, 2010)
Automatic recognition of coronal type II radio bursts: the automated radio burst
identification system method and first observations.
Lobzin V.V., Cairns I.H., Robinson P.A., Steward G., Patterson G.
<Astrophys. J., 710, L58-L62 (2010)>
=2010ApJ...710L..58L 2010ApJ...710L..58L
ADC_Keywords: Sun; Radio sources
Keywords: Sun: activity - Sun: coronal mass ejections (CMEs) - Sun: flares -
Sun: radio radiation - techniques: image processing
Abstract:
Major space weather events such as solar flares and coronal mass
ejections are usually accompanied by solar radio bursts, which can
potentially be used for real-time space weather forecasts. Type II
radio bursts are produced near the local plasma frequency and its
harmonic by fast electrons accelerated by a shock wave moving through
the corona and solar wind with a typical speed of ∼1000km/s. The
coronal bursts have dynamic spectra with frequency gradually falling
with time and durations of several minutes. This Letter presents a new
method developed to detect type II coronal radio bursts automatically
and describes its implementation in an extended Automated Radio Burst
Identification System (ARBIS 2). Preliminary tests of the method with
spectra obtained in 2002 show that the performance of the current
implementation is quite high, ∼80%, while the probability of false
positives is reasonably low, with one false positive per 100-200hr
for high solar activity and less than one false event per 10000hr for
low solar activity periods. The first automatically detected coronal
type II radio burst is also presented.
Description:
In the present study, we use archived and real-time solar radio
spectra provided by the Learmonth Solar Radio Observatory (Western
Australia). The instrument covers a frequency range 25-180MHz and
completes a frequency sweep every 3s. To elaborate suitable techniques
for data processing, we have chosen the year 2002 (near the solar
maximum), when 60 coronal type II events were observed at the
Learmonth observatory. Table 1 displays data extracted from the
National Geophysical Data Center's event listing and the results of
the present study.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 46 60 Type II radio bursts observed at Learmonth
observatory in 2002
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See also:
J/ApJ/710/1111 : Interplanetary shocks radio bursts (Gopalswamy+, 2010)
J/A+AS/119/489 : Solar Type II Radio Bursts, 1990.09 - 1993.12 (Mann+ 1996)
ftp://ftp.ngdc.noaa.gov/STP/SOLAR_DATA/SOLAR_RADIO/SPECTRAL/2002/SPEC_NEW.02 :
National Geophysical Data Center 2002's event listing
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq ? Event number (1)
3 A1 --- m_Seq [ab] Combined events have the same "Seq"
number followed by letters a and b
5- 14 A10 "YYYY/MM/DD" Obs Date of the observation
16- 20 A5 "h:m" Stime UT start time
22- 26 A5 "h:m" Etime UT end time
28 I1 --- Int [1,3] Intensity
30- 32 I3 MHz Sfreq Start frequency
33 A1 --- u_Sfreq [:] Uncertainty flag on Sfreq
35- 37 I3 MHz Efreq End frequency
38 A1 --- u_Efreq [:] Uncertainty flag on Efreq
40 I1 --- True [0/1]? Number of true positives in daily
spectra
42 A1 --- f_True [dn] event not taken into account (2)
44 I1 --- False [0,3]? Number of false alarms in daily
spectra
46 A1 --- f_False [dn] event not taken into account (2)
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Note (1): Events not analyzed have no "Seq" number; specifically, all data for
the April 2002 were unavailable.
Note (2): Flag as follows:
n = data not available.
d = This event is not taken into account because it is questionable.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 30-Mar-2012