Flare Energy Release in the Low Atmosphere

Transcription

1 Flare Energy Release in the Low Atmosphere Alexander G. Kosovichev, Viacheslav M. Sadykov New Jersey Institute of Technology Ivan N. Sharykin, Ivan V. Zimovets Space Research Institute RAS Santiago Vargas Universidad Nacional de Colombia

2 Standard Flare Model: Magnetic reconnection in the corona Polarity Inversion Line (PIL) In the Standard Flare Model, the primary energy release is located in the corona where the magnetic reconnection is driven by a plasmoid/filament eruption. The Hard X-ray Emission is produced by energetic particles at the loop top and loop footpoints. Plasma heating at the footpoints causes the chromospheric evaporation. Figure from K. Shibata et al. 1995, ApJ, 451, 83 Schematic for the standard model in 3D where four prereconnected magnetic field lines are shown. The grey area represents parts of the 3D volume of the QSL and the current layer. The 3D volume of the QSL has been restricted to only show the location of strong currents and limited to a low height (below the flux rope). Figure from M. Janvieret al. 14, ApJ, 788, 60

3 Magnetic Field Polarity Inversion Line High-gradient polarity inversion lines (PIL) are associated with strong flares (Severny, 1958, SvA, 2, 310; Schrijver, 16, ApJ 8, 103).

4 See poster: Flare-induced changes of the photospheric magnetic field in a δ-spot deduced from ground-based observations Gömöry, P.; Balthasar, H.; Kuckein, C.; Koza, J.; Veronig, A. M.; González Manrique, S. J.; Kučera, A.; Schwartz, P.; Hanslmeier, A. (17, AA, 602, A260) 0 07:52:17 UT 07:59:53 UT 08:09:53 UT 08:15:29 UT 08:41:29 UT y [arcsec] x [arcsec] x [arcsec] x [arcsec] x [arcsec] x [arcsec] High-resolution near-infrared spectropolarimetric observations were acquired simultaneously in two photospheric spectral lines, Fe I Å and Si I Å, with the Tenerife Infrared Polarimeter at the VTT on 13 October 15. An enhancement of the transverse magnetic field of approximately 550 G was found after the flare. The field bridges the PIL and connects umbrae of opposite polarities in the δ-spot. y (Mm) y (Mm) y (Mm) :53:09 08:00:36 UT 08:17:45 08:25:11 UT 08:44:19 08:51:43 UT x (Mm) x (Mm) x (Mm) longitudinal magnetic field (G) transverse magnetic field (G) total magnetic field strength (G)

5 Objective Investigate the magnetic structure and dynamics of the Polarity Inversion Line (PIL) in flaring regions, and their relationship to triggers and manifestations of the flare energy release in the lower layers of the solar atmosphere (the photosphere and chromosphere). Two case studies: 1) M1.0 flare of June 12, 14: high-resolution data from BBSO 2) X1.8 flare of Oct. 23, 12: strongest sunquake of Cycle 24

6 Flare 1: June 12, 14 ; М1.0 GOES class The flare was produced in δ-type sunspot of NOAA 187 region which was located at point (-630;-300) approximately 60 degrees from the disk center The X-ray peak occurred at 21:12UT and was observed bytherhessiandgoes.theflarehasm1.0goesclass The IRIS was observed this region from 18:44:38UT to 23:59:44UT in the coarse raster mode (8 slit positions covering the region of interest) The BBSO VIS (H-alpha scans) and BFI (TiO) instruments were observed the region from :43 UT till 21:42UT

7 BBSO observations: TiO filter and Hα line scans TiO filter Hα-0.8A Hα+0.8A Detection of the smallscale twisted flux rope structure at the PIL (Sadykov et al. 14; Kumar et al. 15). The flare started with brightening and expansion of the flux rope, initially had a compact 3-ribbon structure, and then expanded into much larger region.

8 Magnetic field topology and chromospheric evaporation The chromospheric evaporation observed by IRIS was located along the large flare ribbons. Regions of Fe XXI blue shift are found to be connected to the region of magnetic polarity inversion line (PIL) and an expanding flux rope via a system of low-lying loop arcades with height < 4.5 Mm. Sadykov et al, 16, ApJ, 828, 4

9 Twisted magnetic structure and horizontal currents in the polarity inversion line Before flare, :24:08 UT After flare, 22:00:00 UT TiO arcade TiO arcade 10 Mm 10 Mm TiO arcade 10 Mm 10 Mm TiO arcade j h, 10-2 A/m 2

10 Electric current density in the PIL before and after flare Figure shows changes in the distribution of absolute value of j along the slices B and C shown in two top panels with Bz map. Contours mark electric current density levels with values: 15, 37, 75, 150, 224, 298, 336 and 373 ma/m 2. Red line is the PIL in the plane of slice. Sharykin et al. 17, ApJ, 8, 84 In the region of the TiO arcade the magnitude of the electric current density is decreased, and that the height of the maximal current density is also decreased, while the other slices do not show significant changes.

11 Flare 2: Oct 23, 12 ; X1.8 GOES class Movie of HMI magnetograms

12 Flare produced a strong sunquake (the strongest sunquake of Cycle 24, so far) time difference HMI Dopplergram time difference HMI intensity A B C time-distance plot 60 D :15:43 UT Y, Mm 0 60 E ::28 UT Y, Mm X, Mm

13 Standard Flare Model: Hydrodynamic response of the low atmosphere Model of sunquake: Kosovichev & Zharkova, 1995 Rubio da Costa, F. et al, 16, ApJ, 827, 38 Alternative mechanisms of sunquake initiation: Sunquakes initiated by impulsive Lorentz force: Fisher et al., 12 Sunquakes initiated by pressure gradient due to flux rope expansion: Zharkov et al., 13 Sunquakes initiated by rapid dissipation of electric currents: Sharykin et al., 15 It is important to determine the time delay between the X-ray impulse and the photospheric impact and the magnitude of the impact, both in observations and models.

14 Using HMI as a fast-speed photometer Intensity, DNs Intensity, DNs Y, arcsec Camera 1 Camera 2 Camera 1 Camera time, min ("0": :10:01.72 UT) :15:48.60 UT X, arcsec Quiet Sun (Point 1) Flare region (Point 2) DNs FFT power FFT power FFT power Quiet Sun (blue rectangle box) Camera 1 Camera f, Hz Camera 1 Quiet Sun (blue rectangle box) Flare region (point 2) f, Hz Camera 2 Quiet Sun (blue rectangle box) Flare region (point 2) f, Hz Use Level-1 data from the HMI cameras (line scans) and a Fourier transform filter in order to demodulate the signals and recover intensity light curves with 3.6 sec cadence. Sharykin et al, (17)

15 Comparison of the high-cadence HMI intensity with RHESSI kev HXR HMI filtergram :15:48.60 UT 3 DN x HMI camera 2 HMI camera 1 RHESSI kev RHESSI count rate, counts/s Y, arcsec RHESSI 03:15:48.00 UT kev 50-0 kev X, arcsec time, min ("0": 23-oct-12 03:10:01.7 UT) The time delay between the peaks of the HXR emission and the photospheric response does not exceed 10 sec. This suggests that the energy release was in the low atmosphere, perhaps, in the low-lying loops of the PIL.

16 Sunquake sources Y, Mm 30 A (P-P 0)/P (P-P 0 )/P B RHESSI HXR kev [AUs] Egression power: 5-7 mhz X, Mm time, min (from 03:13:05 UT) (a) Egression acoustic power map integrated over the flare impulsive phase around 6 mhz, relative to the egression power of the quiet Sun. Contour lines show magnetic field with levels of 0.5, 1, and 1.5 kg (red for Bz > 0 and blue for Bz < 0). Black curve shows the PIL. (b) Temporal profile of the egression acoustic power (red) and the RHESSI count rate in the energy range of kev. The total helioseismic energy erg, which is approximately 1% of the total energy of nonthermal electrons, erg, determined from the RHESSI X-ray spectra

17 Continuum emission during the impulsive phase Y, arcsec HMI filtergram ( A) HMI filtergram ( A) HMI filtergram ( A) HMI filtergram ( A) 03:15:09.15 UT 03:15:31.66 UT 03:15:54.16 UT 03:16:16.66 UT A B C D (I-I 0 )/I 0, % X, arcsec X, arcsec X, arcsec X, arcsec 10

18 Continuum emission and sunquake sources Y, arcsec HMI filtergram ( A) HMI filtergram ( A) HMI filtergram ( A) HMI filtergram ( A) 03:15:09.15 UT 03:15:31.66 UT 03:15:54.16 UT 03:16:16.66 UT A 5-7 mh z B 5-7 mh z C 5-7 mhz D 5-7 mh z kev 50-0 kev X, arcsec X, arcsec X, arcsec X, arcsec (I-I 0 )/I 0, %

19 Continuum emission, sunquake sources and HXR sources Y, arcsec HMI filtergram ( A) HMI filtergram ( A) HMI filtergram ( A) HMI filtergram ( A) 03:15:09.15 UT 03:15:31.66 UT 03:15:54.16 UT 03:16:16.66 UT A 5-7 mh z B 5-7 mh z C 5-7 mhz D 5-7 mh z kev kev kev kev kev kev kev 50-0 kev X, arcsec X, arcsec X, arcsec X, arcsec (I-I 0 )/I 0, % During the first half of the impulsive phase the strongest HXR and photospheric emissions coincide with the strongest sunquake source.

20 Hinode/SOT images are used to B Y, arcsec estimate the impact area Hinode/SOT red continuum nm :15: 41-03:16:00 UT time difference image F3 F2 F1 RHESSI 03:15:48.00 UT kev 50-0 kev X, arcsec DNs DNs C SOT image slices around F1 Y = arcsec arcsec arcsec X, arcsec SOT image slices around F D Y = arcsec arcsec arcsec X, arcsec The ribbon width (FWHM of intensity profile peaks) is in the range of Mm. In this case the energy density flux of accelerated electrons is in the range of ( ) erg cm 2 s 1

21 Comparison with RADYN model The RADYN model with the highest available flux: F=10 11 ergs sm -2 s -1, power law δ=4. RH code is used to calculate the HMI observables. In the model the Doppler velocity perturbation shows a weak ( 0.5 kms 1 ) downflow that almost coincides with the heating function, followed by a gradual upflow. The amplitude of the plasma velocity in the photosphere in the model does not exceed 0.1 km s 1. photons s -1 cm -2 kev F :15:08-03:15:24 UT 03:15:48-03:16:04 UT nonthermal part thermal part Energy (kev) logt z (km) Normilized intensity Fe I continuum ( nm) Fe I line core ( nm) Fe I Doppler shift Time, s Allred, J. C., Kowalski, A. F., & Carlsson, M. 15, ApJ, 809, 104 Sharykin el al, 17, ApJ, 843, 67 V (km/s) Doppler speed, km/s

22 Magnetic field topology of the PIL before and after the flare NLFFF reconstruction reveals interacting low-lying loops in the PIL where the HRX sources and the photospheric impacts were observed. The low-lying field bridges the magnetic polarities across the PIL, similarly to the results of Gömöry et al. (17). This suggests that there was a significant energy release in the PIL.

23 Conclusions In M1.0 flare, the BBSO images reveal formation of a small-scale ( 3 Mm) arcade-like magnetic shearing structure in the PIL. Magnetic field of this structure is ~1 kg. The results suggest that the primary energy release was in the low atmosphere layers and, probably, caused by interaction of low-lying magnetic loops in the PIL. In X1.8 flare, the photospheric impacts that caused a strong sunquake were located in the PIL, and spatially and temporary coincided with HXR sources. The photospheric disturbances are delayed with respect to the hard X-ray emission by less than 10 s. This delay is consistent with predictions of the RADYN models. However, the current models fail to explain the magnitude of variations observed by the HMI. The data indicate that the electron energy flux was substantially higher than that in the RADYN simulations. The structure and dynamics of the PIL plays a key role in the flare initiation and energy release.