Ultraviolet spectroscopy of narrow coronal mass ejections

We present Ultraviolet Coronagraph Spectrometer (UVCS) observations of 5 narrow coronal mass ejections (CMEs) that were among 15 narrow CMEs originally selected by Gilbert et al. (2001). Two events (1999 March 27, April 15) were "structured", i.e. in white light data they exhibited well defined interior features, and three (1999 May 9, May 21, June 3) were "unstructured", i.e. appeared featureless. In UVCS data the events were seen as 4-13 deg wide enhancements of the strongest coronal lines HI Ly-alpha and OVI (1032,1037 A). We derived electron densities for several of the events from the Large Angle Spectrometric Coronagraph (LASCO) C2 white light observations. They are comparable to or smaller than densities inferred for other CMEs. We modeled the observable properties of examples of the structured (1999 April 15) and unstructured (1999 May 9) narrow CMEs at different heights in the corona between 1.5 and 2 R(Sun). The derived electron temperatures, densities and outflow speeds are similar for those two types of ejections. They were compared with properties of polar coronal jets and other CMEs. We discuss different scenarios of narrow CME formation either as a jet formed by reconnection onto open field lines or CME ejected by expansion of closed field structures. Overall, we conclude that the existing observations do not definitively place the narrow CMEs into the jet or the CME picture, but the acceleration of the 1999 April 15 event resembles acceleration seen in many CMEs, rather than constant speeds or deceleration observed in jets.Comment: AASTeX, 22 pages, incl. 3 figures (2 color) and 3 tables. Accepted for publication in Ap.

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

Thermo-mechanic-electrical coupling in phospholipid monolayers near the critical point

Lipid monolayers have been shown to represent a powerful tool in studying mechanical and thermodynamic properties of lipid membranes as well as their interaction with proteins. Using Einstein's theory of fluctuations we here demonstrate, that an experimentally derived linear relationship both between transition entropy S and area A as well as between transition entropy and charge q implies a linear relationships between compressibility \kappa_T, heat capacity c_\pi, thermal expansion coefficient \alpha_T and electric capacity CT. We demonstrate that these couplings have strong predictive power as they allow calculating electrical and thermal properties from mechanical measurements. The precision of the prediction increases as the critical point TC is approached

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

Polar Field Reversal Observations with Hinode

We have been monitoring yearly variation in the Sun's polar magnetic fields with the Solar Optical Telescope aboard {\it Hinode} to record their evolution and expected reversal near the solar maximum. All magnetic patches in the magnetic flux maps are automatically identified to obtain the number density and magnetic flux density as a function of th total magnetic flux per patch. The detected magnetic flux per patch ranges over four orders of magnitude ($10^{15}$ -- $10^{20}$ Mx). The higher end of the magnetic flux in the polar regions is about one order of magnitude larger than that of the quiet Sun, and nearly that of pores. Almost all large patches ($\geq 10^{18}$ Mx) have the same polarity, while smaller patches have a fair balance of both polarities. The polarity of the polar region as a whole is consequently determined only by the large magnetic concentrations. A clear decrease in the net flux of the polar region is detected in the slow rising phase of the current solar cycle. The decrease is more rapid in the north polar region than in the south. The decrease in the net flux is caused by a decrease in the number and size of the large flux concentrations as well as the appearance of patches with opposite polarity at lower latitudes. In contrast, we do not see temporal change in the magnetic flux associated with the smaller patches ($< 10^{18}$ Mx) and that of the horizontal magnetic fields during the years 2008--2012.Comment: 21 pages, 7 figures. Accepted for publication in Ap

Micro-Sigmoids as Progenitors of Coronal Jets - Is Eruptive Activity Self-Similarly Multi-Scaled?

Observations from the X-ray telescope (XRT) on Hinode are used to study the nature of X-ray bright points, sources of coronal jets. Several jet events in the coronal holes are found to erupt from small-scale, S-shaped bright regions. This finding suggests that coronal micro-sigmoids may well be progenitors of coronal jets. Moreover, the presence of these structures may explain numerous observed characteristics of jets such as helical structures, apparent transverse motions, and shapes. In analogy to large-scale sigmoids giving rise to coronal mass ejections (CMEs), a promising future task would perhaps be to investigate whether solar eruptive activity, from coronal jets to CMEs, is self-similar in terms of properties and instability mechanisms.Comment: 8 pages, 5 figures, 1 tabl

First analysis of solar structures in 1.21 mm full-disc ALMA image of the Sun

Various solar features can be seen on maps of the Sun in the mm and sub-mm wavelength range. The recently installed Atacama Large Millimeter/submillimeter Array (ALMA) is capable of observing the Sun in that wavelength range with an unprecedented spatial, temporal and spectral resolution. To interpret solar observations with ALMA the first important step is to compare ALMA maps with simultaneous images of the Sun recorded in other spectral ranges. First we identify different structures in the solar atmosphere seen in the optical, IR and EUV parts of the spectrum (quiet Sun (QS), active regions (AR), prominences on the disc, magnetic inversion lines (IL), coronal holes (CH) and coronal bright points (CBPs)) in a full disc solar ALMA image. The second aim is to measure the intensities (brightness temperatures) of those structures and compare them with the corresponding QS level. A full disc solar image at 1.21 mm obtained on December 18, 2015 during a CSV-EOC campaign with ALMA is calibrated and compared with full disc solar images from the same day in H\alpha, in He I 1083 nm core, and with SDO images (AIA at 170 nm, 30.4 nm, 21.1 nm, 19.3 nm, and 17.1 nm and HMI magnetogram). The brightness temperatures of various structures are determined by averaging over corresponding regions of interest in the ALMA image. Positions of the QS, ARs, prominences on the disc, ILs, CHs and CBPs are identified in the ALMA image. At 1.21 mm ARs appear as bright areas (but sunspots are dark), while prominences on the disc and CHs are not discernible from the QS background, although having slightly less intensity than surrounding QS regions. ILs appear as large, elongated dark structures and CBPs correspond to ALMA bright points. These results are in general agreement with sparse earlier measurements at similar wavelengths. The identification of CBPs represents the most important new result.Comment: 9 pages, 3 figure

Coronal jet observed by Hinode as the source of a ^3He-rich solar energetic particle event

We study the solar source of the ^3He-rich solar energetic particle (SEP) event observed on 2006 November 18. The SEP event showed a clear velocity dispersion at energies below 1 MeV nucleon^(−1), indicating its solar origin. We associate the SEP event with a coronal jet in an active region at heliographic longitude of W50°, as observed in soft X-rays. This jet was the only noticeable activity in full-disk X-ray images around the estimated release time of the ions. It was temporally correlated with a series of type III radio bursts detected in metric and longer wavelength ranges and was followed by a nonrelativistic electron event. The jet may be explained in terms of the model of an expanding loop reconnecting with a large-scale magnetic field, which is open to interplanetary space for the particles to be observed at 1 AU. The open field lines appear to be anchored at the boundary between the umbra and penumbra of the leading sunspot, where a brightening is observed in both soft and hard X-rays during the jet activity. Other flares in the same region possibly associated with 3He-rich SEP events were not accompanied by a jet, indicative of different origins of this type of SEP event

Simultaneous Observations of the Chromosphere with TRACE and SUMER

Using mainly the 1600 angstrom continuum channel, and also the 1216 angstrom Lyman-alpha channel (which includes some UV continuum and C IV emission), aboard the TRACE satellite, we observed the complete lifetime of a transient, bright chromospheric loop. Simultaneous observations with the SUMER instrument aboard the SOHO spacecraft revealed interesting material velocities through the Doppler effect existing above the chromospheric loop imaged with TRACE, possibly corresponding to extended non-visible loops, or the base of an X-ray jet.Comment: 14 pages, 10 figures, accepted by Solar Physic