Solar flare hard X-ray spikes observed by RHESSI: a statistical study
RHESSI OBSERVATIONS OF THE 2005 JANUARY 20 SOLAR FLARE
description
Transcript of RHESSI OBSERVATIONS OF THE 2005 JANUARY 20 SOLAR FLARE
RHESSI OBSERVATIONS OF THE 2005 JANUARY 20
SOLAR FLARE
Gerald Share1,2, Ronald Murphy2, David Smith3, Gordon Hurford4,
Allan Tylka2, and Robert Lin4
1 UMD, 2NRL,3UCSC, 4UCB
Supported by NASA SEC-GI & SR&T
SUMMARY
RHESSI has observed two distinct components of particle acceleration in the 2005 January 20th solar
flare.
There is a ‘normal’ impulsive component beginning at ~06:42 UT, peaking at ~06:47 UT,
lasting about 10 minutes, evidenced by bremsstrahlung and nuclear-line radiation
interacting at a footpoint with an ion power-law index of ~-3.
A separate component began with a sharp 1-2 min peak at ~06:46 UT, with a spectrum dominated by
pion-decay radiation; emission lasted for ~2 hours. No information as yet on how compact this
source is.
The GLE event commenced at 06:48 UT and was observed at energies >4 GeV. An ~5 min-wide
peak was observed at ~06:53 UT.
Spectral Accumulations
RHESSI observation of the 2005 January 20
SEPs
Spectrum dominated by a strong continuum (bremsstrahlung & pi-decay) extending to high
energies. Line features are relatively weak, consistent with a hard accelerated-particle
spectrum.
…. Bremsstrahlung
___ Narrow Nuclear
- - - Broad Nuclear
-decay
Calculated gamma-ray spectra vs flare-accelerated particle power-law index.
RHESSI gamma-ray time line in January 20 flare
Neutron-capture line fluxes agree with calculations for an accelerated-particle spectrum following a power-law with
index ~3.
250-500 keV 250 – 500 keV 2215-2231keV
RMC 4-9 RMC 6+9 RMC6+9
12 arcsec 35 arcsec 35 arcsec
35 arcsecond resolution cannot distinguish the footpoints
20 January 2005 06:44 - 06:56
128 x 128 arcsec
20 January 2005 06:44-06:56
TRACE 1600A at 06:52:30 UT250 – 500 keV 30, 50, 70, 90% contours 2215-2231 keV centroid 1- error circle
Comparison of Imaged and Spatially-Integrated Neutron-
Capture Line Counts
Demonstrates that particles producing a bulk of the neutron-capture line emission are primarily confined
in magnetic loops.
There appears to be a second high-energy component revealed above 10 MeV that can be fit by a pion-decay spectrum. Its time profile is
different: sharp peak and long tail. This high-energy radiation produces instrumental annihilation line radiation that contributes to
the solar flux in panel 4.
CORONAS (Kuznetsov et al. 2005/6) also observed this high-energy component with a
time profile similar to that observed by RHESSI.
0,01 0,1 1 10 10010-5
10-3
10-1
101
103
SPRN
IAIB
SONG
20 January, 2005
F, sm
-2 s
-1 MeV
-1
Eγ, MeV
06:43:30 – 06:45:10 UT
06:45:10 – 06:47:25 UT
The CORONAS spectra at the peak in the decay phase are consistent with a pion-decay origin.
Good agreement between corrected 511 keV flux and calculation for PL index =3. Nuclear-line flux appears to be produced by one population of accelerated ions interacting in a footpoint while the ‘pion’ and >20 MeV flux is dominated by a second higher-energy
particle component.
The high-energy photon emission observed by RHESSI extends up to two hours after the sharp
peak.
>20 MeV
There is weak 2.223 MeV line emission after 08:00 UT
suggesting that the high-energy emission is from ion interactions.
South Pole neutron monitor flux increased within about 2 min after high-energy gamma-ray peak. The neutron monitor and Milagro rates have relatively narrow peaks
at ~06:53 UT
Hi-E gamma peak
SUMMARY
RHESSI has observed two distinct components of particle acceleration in the 2005 January 20th solar
flare.
There is a ‘normal’ impulsive component beginning at ~06:42 UT, peaking at ~06:47 UT,
lasting about 10 minutes, evidenced by bremsstrahlung and nuclear-line radiation
interacting at a footpoint with an ion power-law index of ~-3.
A separate component began with a sharp 1-2 min peak at ~06:46 UT, with a spectrum dominated by
pion-decay radiation; emission lasted for ~2 hours. No information as yet on how compact this
source is.
The GLE event commenced at 06:48 UT and was observed at energies >4 GeV. An ~5 min-wide
peak was observed at ~06:53 UT.
Comparison of accelerated particles interacting at the Sun and observed in space (Mewaldt, priv. comm. 2005)
Total number of protons >30 MeV:
Solar flare impulsive component: (2.8 ± 0.8) x 1032
Solar flare high-energy component: 0.7 x 1032
Event integrated SEPs: 210 x 1032
Power-law spectral index:
Solar flare impulsive component: 3.0 ± 0.05
Solar flare high-energy component: <2.3
Event integrated SEPs: 2.15
Narrow peaks in the Milagro and Climax NM data (Ryan et al. 2005) appear similar to the high-energy gamma-ray peak. Does the GLE event also have an extended high-
energy component?
Extended emission > 4 GV?
The Tibet Yangbaging neutron monitor also observed such an extended tail. Could some of the counts be due to solar
neutrons?