The solar burst of 21 May 1984 presented a number of unique features. The time profile consisted of seven major structures (seconds), with a turnover frequency  or approx. 90 GHz, well correlated in time to hard X-ray emission. Each structure consisted of multiple fast pulses (.1 seconds), which were analyzed in detail. A proportionality between the repetition rate of the pulses and the burst fluxes at 90 GHz and  or approx. 100 keV hard X-rays, and an inverse proportionality between repetition rates and hard X-rays power law indices have been found. A synchrotron/inverse Compton model has been applied to explain the emission of the fast burst structures, which appear to be possible for the first three or four structures

Correia, E.

Costa, J. E. R.

Dennis, B. R.

Kaufmann, P.

Vaz, A. M. Z.

English

NASA Technical Reports Server

8. Title INPE-380-9-PRE/895
THE POSSIBLE IMPORTANCE OF SYNCHROTRON/INVERSE
COMPTON LOSSES TO EXPLAIN FAST MM-WAVE AND HARD
EMISSION OF A SOLAR EVENT
9. Authorship
E.
P.Kauftnann
J.E.E.Costa
A.M.Zodi Vaz
E.R.Dennis*
Responsible author
(NASft-TM-88659) THE FCSSIELE IMPOH1ANCE OP N86-25316
SYNCHEOTRON/INVEfiSE CCMfTCN 1C£S£S TO
EXPLAIN FAST H«-WAVE AND HA£D X-BAY EMISSION
OF A SOLAR EVEN! (NASA) 11 p EC A02/MF A01 Unclas
CSCL 03B G3/92 43125
INSTITUTO DE PESQUISAS ESPACIAIS
https://ntrs.nasa.gov/search.jsp?R=19860015845 2020-03-20T15:29:28+00:00Z
1. Publication N9
INPE-3809-PRE/895
2. Version 3.. Date
February 1986
.4. Origin Pruyram
DAS-DRA RADIO
5. Distribution
D Internal @ External
D Restricted
6. Key words - selected by the author(s)
SOLAN BURST - SINCHRO/COMPTON RADIATION - ULTRA FAST STRUCTURES.
7. U.D.C.: 523.03
8. Title INPE-380-9-PRE/895
THE. POSSIBLE IMPORTANCE OF SYNCHROTRON/INVERSE
COMPTON LOSSES TO EXPLAIN FAST MM-WAVE AND HARD
3-RA.T EMISSION OF A SOLAR EVENT
9. Authorship
Responsible author
E. Correia
P.Kauflnann
J.E.R.Costa
A.M.Zodi Vaz
E.R.Dennis*
^fc_ <f»
10. NO of pages:10
11. Last page:
12. Revised by
Pierre Kaufmann
13. Authorized by
Dp. Marco Antonio Rai
Director General
14. Abstract/Notes - Th& solar hurst of 21 May 1984 presented a number of
unique features. The time profile consisted in seven major structures
Cseconds-l, with a turnover frequency > 90 GHz, well correlated in time to
hard X-ray- emission. . Each structure consisted in multiple fast pulses
(JO.-2 seconds).^  which were analysed in detail. It has been confirmed a
proportionality between the repetition rate of the pulses and the burst
fluxes, at 90 GHz and > 100 keV hard X-rays, and found an inverse proportio-
nality between repetition rates and hard X-rays power law indices. A
synchrotron/inverse Compton model has been applied to explain the emission
of the fast burst structures, which appear to be possible, for the first
three or four structures.
NASA-GSFC
15. Remarks- To appear in the Proc.of the SMM Topical Workshop on Rapid
Fluctuations-in Solar Flares, NASA, . Lanham, MD, Sep. 30-0ct.4., 1935.
THE POSSIBLE IMPORTANCE OF SYNCHROTRON/INVERSE COMPTON LOSSES TO EXPLAIN
FAST MM-WAVE AND HARD X-RAY EMISSION OF A SOLAR EVENT
E.Correia1 , P .Kaufmann 1 , J .E.R.Costa 1 , A.M.Zodi Vaz1 , and
B.R.Dennis2
!INPE: Institute de Pesquisas Espaciais, C.P.515, 12.200-
Sao Jose dos Campos, S.P.,Brazil
2NASA: Goddard Space Flight Center, Laboratory for Astronomy and
• Solar Physics, Greenbelt, MD 20771, USA
'ABSTRACT
The solar burst of 21 May 1984 presented a number of unique features. The
time profile consisted in seven major structures (seconds), with a turnover
frequency > 90 GHz, well correlated in time to hard X-ray emission. Each
structure consisted in multiple fast pulses (10~2 seconds), which were analysed
in detail. It has been confirmed a proportionality between the repetition rate
of the pulses and the burst fluxes at 90 GHz and > 100 keV hard X-rays, and
found an inverse proportionality between repetition rates and hard X-rays power
law indices. A synchrotron/inverse Compton model has been applied to explain
the emission of the fast burst structures, which appear to be possible for the
first three or four structures.
A number of unique characteristics were found in a solar event observed in
21 May 1984, 1326UT at 30 and 90 GHz by Itapetinga Radio Observatory using
high time resolution (1 ms) and high sensitivity (0.03 S.F.U.), and at hard
X-rays, by the HXRBS experiment on board of the SMM satellite, with 128ms time
resolution. This event was also observed by patrol radio telescopes at 7 GHz
(Itapetinga) and at 1.4, 2.7, 5, 8.8 and 15.4 GHz (AFGL; Cliver, 1984). The
time profiles at hard X-rays, in two energy ranges, and at 90, 30 and 7 GHz
radio frequencies§are shown in Figure 1.
The event presented seven major time structures (1-2 sec duration) at 90
GHz, very well correlated to hard X-rays. They:are labeled A-G in Figure 1.
The 30 GHz emission enhanced only after the fourth structure, and are also well
correlated to the 90 GHz £ind hard X-rays emission. The radio emission intensity :
increased towards the shortest mm-waves, indicating a turnover frequency at
about or above 90 GHz for all seven major time structures, as shown by the
spectra in Figure 2.
ORfGINAL i®
QOALinnf
o
0
cn
C
a)
•a
1326:10 :20 :30 :/»Q : 50 1327:00 : 10
Figure 1 - The solar burst of 21 May 1984,
1326UT, observed at 7, 30 and 90 GHz (Ita_
petinga Radio Observatory) and hard X-rays
(HXRBS-SMM). The seven major time structu
res are labeled A-G.
Each structure was expanded in A second sections, in order to analyse
their time profiles in more detail. Using runnin'g mean technique ,we filtered
the 4 seconds sections to evidence pulses at 30 and 90 GHz (Figure 3). The
plots show that each radio structure, consisted in packets of fast pulses
with durations of tens of milliseconds and relative amplitude of ~50% at 90GHz
and of less than 5% at 30 GHz. Af ter the fourth structure, when the 30 GHz
emission was enhanced, we verified that the pulses between 30 and 90 GHz were
generally in phase, to better than 10 ms (Figure 4)•
Time expanded 4s sections were also analysed in comparison to hard X-rays,
and in terms of spectral indices. Two examples are shown in Figure 5. At
X-rays, the pulses are not visible because their durations (-60 ms) are shorter,
than the time resolution available (-128 ms) . However, when compared with time
integrated 90 GHz data, in the same 128 ms, the overall time structures appear
to he well correlated. Therefore it is likely that the fast pulses are also
present at hard X-ray and would be detected if enough sensitivity, and time
resolution were available. In this case., it is plausible to assume that both,
the radio and hard X-ray pulses, are produced by the same population of energe-
tic electrons.
100
CO
H
>-•
§ ro
X
:=>
04
c
CO
X _ A
o B
a — it — c
o '-It [.;
a .
 F
A
 G
V:
ra
-X^ V^ ^N^
^-/^
&
^
,n
-1 1—H-f-4-f
-I— -I 1 • I- \ t ) I-
10- 10 10 10 11
FREQUENCY (Hz)
Figure 2 - Radio spectra for the maximum of each major
time structure of the 21 May 1984 event, as indicated
in Figure 1.
Table I summarizes the main characteristics of each major time structure
of the burst. The spectral indices of the burst structures are distinguished
from the indices of a slow underlying burst emission component (-20 seconds).
At radio, the spect'ral indices a are defined as F « va, where F is the flux
density and v the frequency. The spectral indices between 30-90 GHz enhanced
for each superimposed structure with a~0.3 - 2.5, while the underlying slow
component spectral index was varying slowly in the 0-1.0 range. The X-ray
power-law spectral indices <5 are defined as F <* E-cl, where F is the flux, E
the photon energy, and q = 5-1. The corresponding hard X-ray structures
exhibited spectral indices reductions to ~ 3, while the slow component remained
at the 6 -4-5'. The spectra become harder in peak of each structure (Figure 5,
Table I) .
Table I - Parameters of the burst major time structures, labeled A-G(Figure 1).
The spectral indices a and q are mean values at the maximum of each structure.
Radio fluxes are in s . f .u . , 1 s . f .u. - 10~22 w/ra2 Hz, and X-ray fluxes are in
units of 3 x 10~25 erg/cm2 s Hz. R is the repetition rate of fast pulses for
each structure, R = N / A t , with N the number of pulses, and At the duration of
the-major structures (or .packet of pulses).
Struc
cure
A
B
C
D
E
F
C
Flux
90 GHz
8
34
S3
40
58
27
23
Flux
30 CKz
3
5
7
9
24
12
16
F l u x X-rav
>30
koV
0.2
0.6
0.7
0.4
1.1
0.6
0.5
>100
IccV
0.01
0.03
0.05
o.o:
0.04
0.02
0.03
socccral indices
burse
a
1.2.
1,8
2.5
1.6
0'.9
0.7
0.3
q
2.2
2.5
1.9
2.7
2.4
2.8
2.7
s ! ou ccra.
a
0.8
0.8
1.0
4.0
0.3
0.3
0.0
<1
4.0
4.0
3.0
3.4
3.4
3.4
3.5
packet
dur.
(see)
2.0
3.8
2.8
1.6
1.7
1.6
1.0
K9
pulses
. N.
3
11
14
5
6
4
3
R
c.-1)
1.5
2.9
5.0
3.0
3.5
2.5
3.0
e-fold.
rise
tico(cs)
60
70.
40
60
50
60
60
AF/F
90 Oil
50
20
50
20
' 30
50
40
Interesting properties are found by correlating pulse repetition rates and
the fluxes at 90 GHz and X-rays, for the various packets of pulses. The
scatter diagrams (Figure 6) are for the seven structures which, together,
included 46 fast pulses. The correlation coefficient was excellent at > 100
KeV X-ray and 90 GHz (better than 90%) but not so good at > 30 KeV X-ray's
(60%).' These results favour the well accepted assumption that the mm-wave
emission are better associated to the higher energy X-rays and confirm the idea
that the pulses emission are quasi-quantized in energy (Kaufmann et al., 1980;
Correia, 1983; and Loran et al. , 1985). The characteristic enerey radiated
by each pulse at the emitting source can be estimated as 5 x 10 ergs at
90 GHz and 1020 ergs at > 100 KeV X-rays. _ .
Another and new result was found by correlating the pulse repetition^rates
and hard X-ray power-law spectral index, shown'in Figure 7. The correlation
coefficient is very good (91%). This result suggest that the harder is the
spectrum, 'the larger is the repetition rate.
The fast pulse emission and the high radio turnover frequency are ^
di f f icu l t to be interpreted using models currently available which consider the
acceleration of non-relativistic or mildly relativistic electrons (Kaufmann
et al., 1985; and McClements and Brown, 1986).
One possible explanation assumes the acceleration of ultrarelativistic
electrons which produce a synchrotron emission component spectrum peaking
somewhere at v > 1011 Hz. The current hard X-ray emission is attributed to
inverse Compton quenching on the synchrotron photons produced in a compact,
bright and short-lived source (Kaufmann et al., 1986). We analysed here this
possible interpretation for all the seven major structures of the 21 May 1984
event.
ORIGINAL PAGE IS
OF POOR
90 QU
30 CIlz N o i ^ e previous Co cha burse
1326:21 :22
1326:27
10
:23
:30
90 CHz
1326:34
1326-.41
90 GHz
. 30 CHz Noise a f t e r burst
1328:00
Figure 3 - All the structures at 90 and 30 GHz plotted on a 4s expanded time
scale with a running mean subtracted from the measured fluxes at the two
frequencies. The flux scales are indicated for structure C, and are kept the
same for all the other 4s sections.
Using the formulation of the synchrotron/inverse Compton model given by
Kaufmann et al., (1986), we obtained the pulse source characteristics in each
one of major time structures. The results, considering a magnetic field of
500 gauss are given in Table II.
The application of the synchrotron/inverse Compton model seems to work
self-consistently in the first four major time structures(A, B, C, D) , which
have turnover frequencies well above 1011 Hz. The estimated source parameters
required to explain the high turnover frequency and the short pulse durations •
(~ 60 ms) are:source of ~107cm and -lO^cnf3 density of energetic electrons
with Lorentz factor y > 40. The model predicts a turnover frequency around
1013 Hz. .
For the last three structures (E, F, and G) exhibiting a turnover
frequency at about 1011 Hz, the application of the model would require
unrealistically high numbers of energetic electrons. The last three structu-
res might be explained by existing models that do not require the acceleration
of ultrarelativistic electrons (.for example: Dulk and Marsh, 1982).
30 GHz Structure D
7.500-4—
128 ms time resolution
4ms time resolution
-1 0. 1
Seconds 30-90GHz spectral index
X-ray spectral index
Figure 4 - Phase relationships
lire analysed for Structure D,
with tfie pulses time profile in
(.a)_, and their cross-correlati-
on in (b). Pulses are in phase
to an accuracy better than 10 ms.
Figure. 5(_a) ~ A comparison of
f lux and spectral indices at
90 and 30 GHz, and hard X-rays
(> 30 KeV) for Structure C.
The trrae resolution at hard :31 :32 :33 :34
X-rays was 128 ras> and at radio was 4 ms. In the upper plot the 90 GHz data
was time integrated in 128 ms, in order to compare to the X-rays time profile.
90GHz_p
Figure 5 (b) - Comparative plots, similar.to
Figure 5(.a) , for Structure E.
M-
en
8 io
0.04-
^ 0.02;
Ul
1 ° c
X f>0
,-J <U
*» 1.5 '
o
'r-i
C i.o -
0.5 '
/ ? '\
V 100 KeV V 2.5 •- *\j_
/ ^ \4/ X-rays & \
A. x 9 n \
' / (b) -S " \
. / ' s \
/ • ' i r ' *l I t -- ti/ 1 . 5 1 3 D ' ' '
/ i \ • - 'I • -1 • o 2 4 G \ o 10
/ 2 4 6 8 10 U _x
s - Figure 7 - Scatter diagram -
.s betweem pulse repetition rates
.s and X-ray spectral index, for
*" ^s the last six burst structures.
./ 30 KeV
+*/* x~rays/*• '
t ' . § i § '
0 2 4 6 8 . 10
RCs"1)
• * " '
Figure 6 - Scatter diagrams: (a) Pulse
repetition rates and fluxes at 90 GHz,
(b) repetition rates at 90 GHz and
fluxes at hard X-rays (> 1.00 KeV) , and
(c) repetition rates at 90 GHz and
fluxes at hard X-rays (> 30 KeV) , for
all the seven structures.
Table II - Pulse source characteristics defined by Kaufraann et al., (1986)
^yTTchroTron/inverse-Conipton model application of each major time structure
as labeled in Figure 1. Parameters are defined at times t = t (at the
begining of the pulse) and t = tp (at the maximum of the pulse radio emission),
Y is the Lorentz factor , 5 is the fraction of energy lost by the electrons,
£ - Y'C't = t p ) /y ( t = t0) ; v is the maximum frequency of the spectrum produced
by the accelerated ultrarelativistic electrons; K is the proportionality factor
of the power law distribution N(y) = Ky~n; N and Nt are the density and total
number of electrons accelerated per pulse'; r ,„ is the ratio of the inverse-
Compton to bremss trail lung losses "intrinsic" £o the emitting pulse source.
STRUG
TURE
•A
B
C
D
vsm ..
(t=t0
Hz-
7xl013
SxlO13
7xl013
9xl013
vsm
(t=tp)
Hz
3xl012
4xl012
2xl012
4xl012
5
0.21
0.26
0.17
0.21
KV
electrons
2xl039
10*1
4xl038
9:<10A1
Nt
electrons
2xl031
2xl032
SxlO31
2x1 O32
c:-
3
2xl010
2X1011
SxlO10
2xlOU
Y
(t=cp)
47
40
39
45
rc/B
co tp
107 10
'107 56
107 2
3xl07 24
scale
size
era '
107
107
107
io7
Acknowledgements
This research was partially supported by the brazilian research agency
FINEP. INPE operates CMAM and Itapetinga Radio Observatory. One of the
authors (PK) is Guest Investigator on NASA-SMM Project.
REFERENCES
Oliver ,E.W.: 1984, private commun-ication.
Correia,E.: 1983, MS thesis, INPE, Brazil.
Bulk,G.A.; and Harsh ,K. A.: 1982, Astrophys. J.
 3 259., 350.
Kaufraann,P.; Strauss,F.M.; Opher,R.; Laporte.C.: 1980, Astron. Astrophys.> 87,
58.*
Kaufmann,P. ; Correia.E.; Costa,J .E.R.; Zodi Vaz.A.M.; and Dennis,B.R.; 1985, _
Nature, 313, 380.
Kaufmann,P. ; Correia.E.; Cos ta, J.E .R.; and Zodi. Vaz,A.M.: 19-86, Astron.
Astrophys., in. press.
Loran,J .M.; Brown,J .C. ; Correia,E.; and Kaufmann.P.: 1985, Solar Phys., 97,363.
McClements ,K.G. ; and Brown,J .C.: 1986, Astron. Astrophys., submitted.


The possible importance of synchrotron/inverse Compton losses to explain fast MM-wave and hard X-ray emission of a solar event

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