1,665 research outputs found
Examination of Separator Reconnection Rates in a Series of Adjacent Emerging/Existing Active Region Pairs
No abstract availabl
Complex Dynamic Flows in Solar Flare Sheet Structures
Observations of high-energy emission from solar flares often reveal the presence of large sheet-like structures, sometimes extending over a space comparable to the Sun's radius. Given that these structures are found between a departing coronal mass ejection and the post-eruption flare arcade, it is natural to associate the structure with a current sheet; though the relationship is unclear. Moreover, recent high-resolution observations have begun to reveal that the motions in this region are highly complex, including reconnection outflows, oscillations, and apparent wakes and eddies. We present a detailed first look at the complicated dynamics within this supra-arcade plasma, and consider implications for the interrelationship between the plasma and its embedded magnetic field
Heating Features of Interesting Supra-Arcade Downflows
Supra-arcade downflows (SADs) have been observed above flare loops during the decay phase of flare. They appear as tadpole-like dark plasma voids traveling towards the Sun. In areas surrounding where they appear, temperatures are often high. We aim to investigate temperature and heating mechanism of SADs. We apply our analysis to the M1.7 flare that occurred on 2012 July 12 and was observed by the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory. There are many obvious SADs above the arcade during this event in the AIA 131 channel. We calculate the differential emission measure and emission measure weighted temperature with AIA data in the region where SADs are concentrated. We find that the temperature in SADs region tends to be lower than the surrounding plasma. We also calculate velocities of SADs using the Fourier Local Correlation Tracking (FLCT, Fisher & Welsch, 2008) method to derive velocities in the supra-arcade region. Using corks to track the calculated velocities, we find our velocity results are consistent with the SAD motions in the AIA 131 intensity movie. We use the velocities to derive the adiabatic heating caused by the compression of plasma. Preliminary results indicate that there is adiabatic heating in front of the SADs
Quantitative Examination of a Large Sample of Supra-Arcade Downflows in Eruptive Solar Flares
Sunward-flowing voids above post-coronal mass ejection (CME) flare arcades
were first discovered using the soft X-ray telescope (SXT) aboard Yohkoh and
have since been observed with TRACE (extreme ultra-violet (EUV)), SOHO/LASCO
(white light), SOHO/SUMER (EUV spectra), and Hinode/XRT (soft X-rays (SXR)).
Supra-arcade downflow (SAD) observations suggest that they are the
cross-sections of thin flux tubes retracting from a reconnection site high in
the corona. Supra-arcade downflowing loops (SADLs) have also been observed
under similar circumstances and are theorized to be SADs viewed from a
perpendicular angle. Previous studies have presented detailed SAD observations
for a small number of flares. In this paper we present a substantial SADs and
SADLs flare catalog. We have applied semi-automatic detection software to
several of these events to detect and track individual downflows thereby
providing statistically significant samples of parameters such as velocity,
acceleration, area, magnetic flux, shrinkage energy, and reconnection rate. We
discuss these measurements, how they were obtained, and potential impact on
reconnection models.Comment: Submitted to ApJ -- 33 pages, 13 figure
Photothermal Fluctuations as a Fundamental Limit to Low-Frequency Squeezing in a Degenerate Optical Parametric Amplifier
We study the effect of photothermal fluctuations on squeezed states of light
through the photo-refractive effect and thermal expansion in a degenerate
optical parametric amplifier (OPA). We also discuss the effect of the
photothermal noise in various cases and how to minimize its undesirable
consequences. We find that the photothermal noise in the OPA introduces a
significant amount of noise on phase squeezed beams, making them less than
ideal for low frequency applications such as gravitational wave (GW)
interferometers, whereas amplitude squeezed beams are relatively immune to the
photothermal noise and may represent the best choice for application in GW
interferometers
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