Transcript solar atmosphere

Spectrum of Accelerated Particles
Derived from the 2.223 MeV Line Data
in Some Solar Flares
Leonty I. Miroshnichenko (1, 2),
Evgenia V. Troitskaia (3), and Wei Q. Gan (4)
(1) Instituto de Geofísica, UNAM, MEXICO, [email protected]
(2) IZMIRAN, Troitsk, Moscow, RUSSIA, [email protected]
(3) SINP, Moscow State University, Moscow, RUSSIA
(4) Purple Mountain Observatory (PMO), Nanjing, CHINA
Abstract
•
•
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The 2.223 MeV line time profile for the flare of 16 December 1988 (for its third
most intensive peak) is studied. The enhancement of plasma density in the deep
photospheric layers below the flare region has been deduced. The energy
spectrum of energetic solar particles (protons) is assumed to be formed by
stochastic mechanism of acceleration.
To compare our model calculations with observations, we use two possible
functions for spectrum presentation, the power-law and Bessel functions with
spectral indices s and αT, respectively. The spectrum was shown to evolve with
time, namely, the spectral index αT was found to increase from 0.005 to 0.1
during the decay phase of the burst, i.e., the proton spectrum has become
harder.
The density enhancement found in the flare of 16 December 1988 is consistent
with our previous results for two other gamma-ray flares, 6 November 1997
and 22 March 1991.
This conclusion seems do not depend on the function of spectrum presentation
and on the model of secondary neutron production by accelerated solar
particles in the solar atmosphere. It is suggested that density enhancement in
the deep layers of the solar photosphere may be rather common feature of
powerful solar flares.
Density models for the solar atmosphere
Fig.1. Basic density model
of the solar atmosphere (1)
and four distorted models
(2-5). Only fragments
differing from the curve
(1) are shown (Kuzhevskij
et al., 2005). Parameter τ
is the optical depth for a
wavelength of 500 nm, the
level τ = 0.005 corresponds
to the top of the
photosphere.
Results of Model Calculations
(Power-Law Spectrum)
S=4
10

-2
flux, cm (16s)
-1
Fig. 2. Observed 2.223
MeV line fluences of the 16
December 1988 flare
(black diamonds) and the
best density model 5 for
the entire time profile of
the third gamma-ray burst
at S = 4.0.

16 December data
Models
1

2

3
4
5
1
0
50
100
150
200
250
Time, seconds
300
350
400
450
Results of Model Calculations
(Exponential Spectrum)

= 0.03
-1
10

-2
Flux,cm (16s)
Fig.3. Observed 2.223 MeV
line fluences of the 16
December 1988 flare
(black diamonds) and the
best density model 5 for
the entire time profile of
the third gamma-ray
burst. Model calculations
have been made with a
new neutron spectrum
(Hua et al., 2002) at αT =
0.03.
16 December data
Models
1





0
50
100
150
200
250
Time, seconds
300
350
400
450
Fig.4. Combined profile of the 2.223 MeV line burst on
16 December 1988 calculated at density models 2, 5
and S = 2, 4, 6 from Hua and Lingenfelter (1987)
16.12.88(N27E33)
data GRS,SMM
Models:
model2 S=4
model5 S=6
model5 S=2
-2
Flux, cm (16s)
-1
10
1
0
50
100
150
200
250
Time, seconds
300
350
400
450
Conclusions
• The density enhancement found in the flare of 16
December 1988 is consistent with our previous
results for two other gamma-ray flares, 6
November 1997 and 22 March 1991.
• This conclusion seems do not depend on the
function of spectrum presentation and on the
model of secondary neutron production by
accelerated solar particles in the solar atmosphere.
• It is suggested that density enhancement in the
deep layers of the solar photosphere may be rather
common feature of powerful solar flares.
Implications and Prospects
From above discussion it follows that
implications and further prospects of suggested
method are determined by involving new
observational data on the flares registered
during last years with high energy, time and
angle resolutions, in particular, by RHESSI,
CORONAS-F, and INTEGRAL spacecraft (23
July 2002, October-November 2003, and 20
January 2005).
Implications and Prospects
• At this way a serious problem exists due to nonradiative neutron absorption on He-3. In this context,
it would be very important to obtain independent
measurements of the He-3 content by new methods of
solar gamma-spectroscopy or by registration a weak
line at 20.58 MeV from radiative absorption of
neutrons by He-3 nuclei in solar flares.
• Some other possibilities arise from the considerations
of power-law spectra of solar protons accelerated by
shock waves and from account for possible
distribution of original neutrons on depth in the solar
atmosphere.
ACKNOWLEDGEMENTS
This work was supported partly by the CONACyT,
Mexico (project 45822, PERPJ10332), Russian
Foundation for Basic Research (RFBR, projects 0202-39032, 03-02-96026, 05-02-39011), Federal
Purpose Scientific and Technical Program, Section I,
Project 4), and President’s Grant of Russian
Federation (project 1445.2003.2). We also wish to
thank S.A. Chaikin and G.A. Kuleshov for the help in
calculations. The work by W. Gan was supported by
NNSFC (China) via grants 10173027, 10221001,
10333040) and by grant G2000078402 from the
Ministry of Science and Technology of China.
Acknowledgements
•
This work was greatly inspired by
Prof. Boris M. Kuzhevskij who
drastically passed away on 28
February 2005. His contribution to
the investigation of different aspects
of solar gamma rays remains very
significant.
Important references
• B.M. Kuzhevskij. Uspekhi Fizicheskikh Nauk,
137(2), 237-265 (1982).
• X.-M. Hua, R.E. Lingenfelter. Solar Phys., 107, 351
(1987).
• X.-M. Hua, B. Kozlovsky, R.E. Lingenfelter et al. (in
all 5 authors). Ap. J. Suppl., 140, 563-579 (2002).
• B.M. Kuzhevskij, L.I. Miroshnichenko, and E.V.
Troitskaia. Russian Astronomy Reports, 49(7), 566577 (2005).