Browsing by Author "Wülser, J.P."
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Item Homologous Helical Jets: Observations By IRIS, SDO, and Hinode and Magnetic Modeling With Data‐Driven(2015-03-05) Cheung, Mark C.M.; De Pontieu, B.; Tarbell, Ted D.; Fu, Y.; Tian, Hui; Testa, Paola; Reeves, Kathy K.; Martínez-Sykora, J.; Boerner, B.; Wülser, J.P.; Lemen, James; Title, Alan M.; Hurlburt, Neal E.; Kleint, Lucia; Kankelborg, Charles; Jaeggli, Sarah; Golub, Leon; McKillop, Sean; Saar, Steven; Carlsson, Mats; Hansteen, Viggo H.We report on observations of recurrent jets by instruments on board the Interface Region Imaging Spectrograph, Solar Dynamics Observatory (SDO), and Hinode spacecraft. Over a 4 hr period on 2013 July 21, recurrent coronal jets were observed to emanate from NOAA Active Region 11793. Far-ultraviolet spectra probing plasma at transition region temperatures show evidence of oppositely directed flows with components reaching Doppler velocities of ±100 km s−1. Raster Doppler maps using a Si iv transition region line show all four jets to have helical motion of the same sense. Simultaneous observations of the region by SDO and Hinode show that the jets emanate from a source region comprising a pore embedded in the interior of a supergranule. The parasitic pore has opposite polarity flux compared to the surrounding network field. This leads to a spine-fan magnetic topology in the coronal field that is amenable to jet formation. Time-dependent data-driven simulations are used to investigate the underlying drivers for the jets. These numerical experiments show that the emergence of current-carrying magnetic field in the vicinity of the pore supplies the magnetic twist needed for recurrent helical jet formation.Item The Interface Region Imaging Spectrograph (IRIS)(2014-02) De Pontieu, Bart; Title, Alan M.; Lemen, James; Kushner, G.D.; Akin, D.J.; Allard, A.; Berger, T.; Boerner, P.; Cheung, M.; Chou, C.; Drake, J.F.; Duncan, D.W.; Freeland, S.; Heyman, G.F.; Hoffman, C.; Hurlburt, Neal E.; Lindgren, R.W.; Mathur, D.; Rehse, R.; Sabolish, D.; Seguin, R.; Schrijver, C.J.; Tarbell, Ted D.; Wülser, J.P.; Wolfson, C.J.; Yanari, C.; Mudge, J.; Nguyen-Phuc, N.; Timmons, R.; van Bezooijen, R.; Weingrod, I.; Brookner, R.; Butcher, G.; Dougherty, B.; Eder, J.; Knagenhjelm, V.; Larsen, S.; Mansir, D.; Phan, L.; Boyle, P.; Cheimets, P.N.; DeLuca, E.E.; Golub, Leon; Gates, R.; Hertz, E.; McKillop, Sean; Park, Saehan; Perry, T.; Podgorski, W.A.; Reeves, Kathy K.; Saar, Steven; Testa, Paola; Tian, Hui; Weber, Mark A.; Dunn, C.; Eccles, S.; Jaeggli, Sarah; Kankelborg, Charles; Mashburn, K.; Pust, Nathan J.; Springer, LarryThe Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft provides simultaneous spectra and images of the photosphere, chromosphere, transition region, and corona with 0.33 0.4 arcsec spatial resolution, twosecond temporal resolution, and 1 km s1 velocity resolution over a fieldofview of up to 175 arcsec × 175 arcsec. IRIS was launched into a Sunsynchronous orbit on 27 June 2013 using a PegasusXL rocket and consists of a 19cm UV telescope that feeds a slitbased dualbandpass imaging spectrograph. IRIS obtains spectra in passbands from 1332 1358 Å, 1389 1407 Å, and 2783 2834 Å, including bright spectral lines formed in the chromosphere (Mg ii h 2803 Å and Mg ii k 2796 Å) and transition region (C ii 1334/1335 Å and Si iv 1394/1403 Å). Slitjaw images in four different passbands (C ii 1330, Si iv 1400, Mg ii k 2796, and Mg ii wing 2830 Å) can be taken simultaneously with spectral rasters that sample regions up to 130 arcsec × 175 arcsec at a variety of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to emission from plasma at temperatures between 5000 K and 10 MK and will advance our understanding of the flow of mass and energy through an interface region, formed by the chromosphere and transition region, between the photosphere and corona. This highly structured and dynamic region not only acts as the conduit of all mass and energy feeding into the corona and solar wind, it also requires an order of magnitude more energy to heat than the corona and solar wind combined. The IRIS investigation includes a strong numerical modeling component based on advanced radiativeMHD codes to facilitate interpretation of observations of this complex region. Approximately eight Gbytes of data (after compression) are acquired by IRIS each day and made available for unrestricted use within a few days of the observation.Item An Interface Region Imaging Spectrograph First View on Solar Spicules(2014-09) Pereira, Tiago M. D.; De Pontieu, Bart; Carlsson, Mats; Hansteen, Viggo H.; Tarbell, Ted D.; Lemen, James; Title, Alan M.; Boerner, P.; Hurlburt, Neal E.; Wülser, J.P.Solar spicules have eluded modelers and observers for decades. Since the discovery of the more energetic type II, spicules have become a heated topic but their contribution to the energy balance of the low solar atmosphere remains unknown. Here we give a first glimpse of what quietSun spicules look like when observed with NASA's recently launched Interface Region Imaging Spectrograph (IRIS). Using IRIS spectra and filtergrams that sample the chromosphere and transition region, we compare the properties and evolution of spicules as observed in a coordinated campaign with Hinode and the Atmospheric Imaging Assembly. Our IRIS observations allow us to follow the thermal evolution of type II spicules and finally confirm that the fading of Ca II H spicules appears to be caused by rapid heating to higher temperatures. The IRIS spicules do not fade but continue evolving, reaching higher and falling back down after 500800 s. Ca II H type II spicules are thus the initial stages of violent and hotter events that mostly remain invisible in Ca II H filtergrams. These events have very different properties from type I spicules, which show lower velocities and no fading from chromospheric passbands. The IRIS spectra of spicules show the same signature as their proposed disk counterparts, reinforcing earlier work. Spectroheliograms from spectral rasters also confirm that quietSun spicules originate in bushes from the magnetic network. Our results suggest that type II spicules are indeed the site of vigorous heating (to at least transition region temperatures) along extensive parts of the upward moving spicular plasma.