First ALMA Observation of a Solar Plasmoid Ejection from an X-ray Bright Point

Eruptive phenomena such as plasmoid ejections or jets are an important feature of solar activity with the potential for improving our understanding of the dynamics of the solar atmosphere. Such ejections are often thought to be signatures of the outflows expected in regions of fast magnetic reconnection. The 304 A EUV line of Helium, formed at around 10^5 K, is found to be a reliable tracer of such phenomena, but the determination of physical parameters from such observations is not straightforward. We have observed a plasmoid ejection from an X-ray bright point simultaneously at millimeter wavelengths with ALMA, at EUV wavelengths with AIA, in soft X-rays with Hinode/XRT. This paper reports the physical parameters of the plasmoid obtained by combining the radio, EUV and X-ray data. As a result, we conclude that the plasmoid can consist either of (approximately) isothermal 10^5 K plasma that is optically thin at 100 GHz, or else a 10^4 K core with a hot envelope. The analysis demonstrates the value of the additional temperature and density constraints that ALMA provides, and future science observations with ALMA will be able to match the spatial resolution of space-borne and other high-resolution telescopes.Comment: 10 page, 5 figures, accepted for publication in Astrophysical Journal Letter. The movie can be seen at the following link: http://hinode.nao.ac.jp/user/shimojo/data_area/plasmoid/movie5.mp

Evidence for a Common Representation of Decision Values for Dissimilar Goods in Human Ventromedial Prefrontal Cortex

To make economic choices between goods, the brain needs to compute representations of their values. A great deal of research has been performed to determine the neural correlates of value representations in the human brain. However, it is still unknown whether there exists a region of the brain that commonly encodes decision values for different types of goods, or if, in contrast, the values of different types of goods are represented in distinct brain regions. We addressed this question by scanning subjects with functional magnetic resonance imaging while they made real purchasing decisions among different categories of goods (food, nonfood consumables, and monetary gambles). We found activity in a key brain region previously implicated in encoding goal-values: the ventromedial prefrontal cortex (vmPFC) was correlated with the subjects' value for each category of good. Moreover, we found a single area in vmPFC to be correlated with the subjects' valuations for all categories of goods. Our results provide evidence that the brain encodes a "common currency" that allows for a shared valuation for different categories of goods

Does the 8−N8-N bonding rule break down in As2_2Se3_3 glass?

The local coordination numbers of As$_2$Se$_3$ glass were determined by a combination of anomalous x-ray scattering experiments, reverse Monte Carlo calculations, and {\it ab initio} molecular dynamics simulations. The well-known `8-$N$ bonding rule' proposed by Mott breaks down around the As atoms, exceeding the rule by 7--26%. An experimental prediction based on mean-field theory agrees with the present experimental and theoretical results. The fourfold coordinated As atoms likely form As-As wrong bond chains rather than ethan-like configurations, which is identified as the origin for the breakdown of the `8-$N$ bonding rule'.Comment: 6 pages, 6figures, 1table, submitted to Europhysics Letter

Frequency and Phase Synchronization in Neuromagnetic Cortical Responses to Flickering-Color Stimuli

In our earlier study dealing with the analysis of neuromagnetic responses (magnetoencephalograms - MEG) to flickering-color stimuli for a group of control human subjects (9 volunteers) and a patient with photosensitive epilepsy (a 12-year old girl), it was shown that Flicker-Noise Spectroscopy (FNS) was able to identify specific differences in the responses of each organism. The high specificity of individual MEG responses manifested itself in the values of FNS parameters for both chaotic and resonant components of the original signal. The present study applies the FNS cross-correlation function to the analysis of correlations between the MEG responses simultaneously measured at spatially separated points of the human cortex processing the red-blue flickering color stimulus. It is shown that the cross-correlations for control (healthy) subjects are characterized by frequency and phase synchronization at different points of the cortex, with the dynamics of neuromagnetic responses being determined by the low-frequency processes that correspond to normal physiological rhythms. But for the patient, the frequency and phase synchronization breaks down, which is associated with the suppression of cortical regulatory functions when the flickering-color stimulus is applied, and higher frequencies start playing the dominating role. This suggests that the disruption of correlations in the MEG responses is the indicator of pathological changes leading to photosensitive epilepsy, which can be used for developing a method of diagnosing the disease based on the analysis with the FNS cross-correlation function.Comment: 21 pages, 14 figures; submitted to "Laser Physics", 2010, 2

Dynamics and plasma properties of an X-ray jet from SUMER, EIS, XRT and EUVI A & B simultaneous observations

Small-scale transient phenomena in the quiet Sun are believed to play an important role in coronal heating and solar wind generation. One of them named as "X-ray jet" is the subject of our study. We indent to investigate the dynamics, evolution and physical properties of this phenomenon. We combine spatially and temporally multi-instrument observations obtained simultaneously with the SUMER spectrometer onboard SoHO, EIS and XRT onboard Hinode, and EUVI/SECCHI onboard the Ahead and Behind STEREO spacecrafts. We derive plasma parameters such as temperatures and densities as well as dynamics by using spectral lines formed in the temperature range from 10 000 K to 12 MK. We also use image difference technique to investigate the evolution of the complex structure of the studied phenomenon. With the available unique combination of data we were able to establish that the formation of a jet-like event is triggered by not one but several energy depositions which are most probably originating from magnetic reconnection. Each energy deposition is followed by the expulsion of pre-existing or new reconnected loops and/or collimated flow along open magnetic field lines. We derived in great detail the dynamic process of X-ray jet formation and evolution. We also found for the first time spectroscopically in the quiet Sun a temperature of 12~MK and density of 4 10^10~cm^-3 in a reconnection site. We raise an issue concerning an uncertainty in using the SUMER Mg X 624.9 A line for coronal diagnostics. We clearly identified two types of up-flow: one collimated up-flow along open magnetic field lines and a plasma cloud formed from the expelled BP loops. We also report a cooler down-flow along closed magnetic field lines. A comparison is made with a model developed by Moreno-Insertis \etal\ (2008).Comment: 15 pages, 15 figure

Observations of a rotating macrospicule associated with an X-ray jet

We attempt to understand the driving mechanism of a macrospicule and its relationship with a coronal jet. We study the dynamics of a macrospicule and an associated coronal jet captured by multi-spacecraft observations. Doppler velocities both in the macrospicule and the coronal jet are determined by EIS and SUMER spectra. Their temporal evolution is studied using X-ray and He II 304 images. A blueshift of -120+/-15 km/s is detected on one side of the macrospicule, while a redshift of 50+/-6 km/s is found at the base of the other side. The inclination angle of the macrospicule inferred from a stereoscopic analysis with STEREO suggests that the measured Doppler velocities can be attributed to a rotating motion of the macrospicule rather than a radial flow or an expansion. The macrospicule is driven by the unfolding motion of a twisted magnetic flux rope, while the associated X-ray jet is a radial outflow.Comment: 4 pages, 3 figures, accepted for publication in A&

Multi-wavelength spectroscopic observation of EUV jet in AR 10960

We have studied the relationship between the velocity and temperature of a solar EUV jet. The highly accelerated jet occurred in the active region NOAA 10960 on 2007 June 5. Multi-wavelength spectral observations with EIS/Hinode allow us to investigate Doppler velocities at the wide temperature range. We analyzed the three-dimensional angle of the jet from the stereoscopic analysis with STEREO. Using this angle and Doppler velocity, we derived the true velocity of the jet. As a result, we found that the cool jet observed with \ion{He}{2} 256 \AA $\log_{10}T_e[\rm{K}] = 4.9$ is accelerated to around $220 \rm{km/s}$ which is over the upper limit of the chromospheric evaporation. The velocities observed with the other lines are under the upper limit of the chromospheric evaporation while most of the velocities of hot lines are higher than that of cool lines. We interpret that the chromospheric evaporation and magnetic acceleration occur simultaneously. A morphological interpretation of this event based on the reconnection model is given by utilizing the multi-instrumental observations.Comment: Accepted for publication in Ap

Mind reading: discovering individual preferences from eye movements using switching hidden Markov models

Conference Theme: Integrating Psychological, Philosophical, Linguistic, Computational and Neural PerspectivesPoster Session 3: no. 33Here we used a hidden Markov model (HMM) based approach to infer individual choices from eye movements in preference decision-making. We assumed that during a decision making process, participants may switch between exploration and decision-making periods, and this behavior can be better captured with a Switching HMM (SHMM). Through clustering individual eye movement patterns described in SHMMs, we automatically discovered two groups of participants with different decision making behavior. One group showed a strong and early bias to look more often at the to-be chosen stimulus (i.e., the gaze cascade effect; Shimojo et al., 2003) with a short final decision-making period. The other group showed a weaker cascade effect with a longer final decision- making period. The SHMMs also showed capable of inferring participants’ preference choice on each trial with high accuracy. Thus, our SHMM approach made it possible to reveal individual differences in decision making and discover individual preferences from eye movement data.postprin

EUV jets, type III radio bursts and sunspot waves investigated using SDO/AIA observations

Images from the Solar Dynamics Observatory (SDO) at 211A are used to identify the solar source of the type III radio bursts seen in WIND/WAVES dynamic spectra. We analyse a 2.5 hour period during which six strong bursts are seen. The radio bursts correlate very well with the EUV jets coming from the western side of a sunspot in AR11092. The EUV jet emission also correlates well with brightening at what looks like their footpoint at the edge of the umbra. For 10-15 min after strong EUV jets are ejected, the footpoint brightens at roughly 3 min intervals. In both the EUV images and the extracted light curves, it looks as though the brightening is related to the 3-min sunspot oscillations, although the correlation coefficient is rather low. The only open field near the jets is rooted in the sunspot. We conclude that active region EUV/X-ray jets and interplanetary electron streams originate on the edge of the sunspot umbra. They form along a current sheet between the sunspot open field and closed field connecting to underlying satellite flux. Sunspot running penumbral waves cause roughly 3-min jet footpoint brightening. The relationship between the waves and jets is less clear.Comment: 4 pages, 7 figures, Accepted by A&A Letters. For associated gif movie, see http://www.mps.mpg.de/data/outgoing/innes/jets/losb_304_211_rd.gi

A First Comparison of Millimeter Continuum and Mg II Ultraviolet Line Emission from the Solar Chromosphere

We present joint observations of the Sun by the Atacama Large Millimeter/submillimeter Array (ALMA) and the Interface Region Imaging Spectrograph (IRIS). The observations were made of a solar active region on 2015 December 18 as part of the ALMA science verification effort. A map of the Sun's continuum emission of size $2.4' \times 2.3'$ was obtained by ALMA at a wavelength of 1.25 mm (239 GHz) using mosaicing techniques. A contemporaneous map of size $1.9'\times 2.9'$ was obtained in the Mg II h doublet line at 2803.5\AA\ by IRIS. Both mm/submm$-\lambda$ continuum emission and ultraviolet (UV) line emission are believed to originate from the solar chromosphere and both have the potential to serve as powerful and complementary diagnostics of physical conditions in this poorly understood layer of the solar atmosphere. While a clear correlation between mm-$\lambda$ brightness temperature $T_B$ and the Mg II h line radiation temperature $T_{rad}$ is observed the slope is $<1$, perhaps as a result of the fact that these diagnostics are sensitive to different parts of the chromosphere and/or the Mg II h line source function includes a scattering component. There is a significant offset between the mean $T_B$(1.25 mm) and mean $T_{rad}$(Mg II), the former being $\approx 35\%$ greater than the latter. Partitioning the maps into "sunspot", "quiet regions", and "plage regions" we find that the slope of the scatter plots between the IRIS Mg II h line $T_{rad}$ and the ALMA brightness temperature $T_B$ is 0.4 (sunspot), 0.56 (quiet regions), and 0.66 (plage regions). We suggest that this change may be caused by the regional dependence of the formation heights of the IRIS and ALMA diagnostics, and/or the increased degree of coupling between the UV source function and the local gas temperature in the hotter, denser gas in plage regions.Comment: 8 pages, 2 figure