Publication Search Results

Search Results

Showing 1-20 of about 91 results.
The Drivers of Active Region Outflows into the Slow Solar WindBrooks, David H.Winebarger, Amy R.Savage, SabrinaWarren, Harry P.De Pontieu, BartPeter, HardiCirtain, Jonathan W.Golub, LeonKobayashi, KenMcIntosh, Scott W.McKenzie, DavidMorton, RichardRachmeler, LaurelTesta, PaolaTiwari, SanjivWalsh, RobertDOI: info:10.3847/1538-4357/ab8a4cv. 894144
Brooks, David H., Winebarger, Amy R., Savage, Sabrina, Warren, Harry P., De Pontieu, Bart, Peter, Hardi, Cirtain, Jonathan W., Golub, Leon, Kobayashi, Ken, McIntosh, Scott W., McKenzie, David, Morton, Richard, Rachmeler, Laurel, Testa, Paola, Tiwari, Sanjiv, and Walsh, Robert. 2020. "The Drivers of Active Region Outflows into the Slow Solar Wind." The Astrophysical Journal 894:144.
ID: 156960
Type: article
Authors: Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; Warren, Harry P.; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub, Leon; Kobayashi, Ken; McIntosh, Scott W.; McKenzie, David; Morton, Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert
Abstract: Plasma outflows from the edges of active regions have been suggested as a possible source of the slow solar wind. Spectroscopic measurements show that these outflows have an enhanced elemental composition, which is a distinct signature of the slow wind. Current spectroscopic observations, however, do not have sufficient spatial resolution to distinguish what structures are being measured or determine the driver of the outflows. The High-resolution Coronal Imager (Hi-C) flew on a sounding rocket in 2018 May and observed areas of active region outflow at the highest spatial resolution ever achieved (250 km). Here we use the Hi-C data to disentangle the outflow composition signatures observed with the Hinode satellite during the flight. We show that there are two components to the outflow emission: a substantial contribution from expanded plasma that appears to have been expelled from closed loops in the active region core and a second contribution from dynamic activity in active region plage, with a composition signature that reflects solar photospheric abundances. The two competing drivers of the outflows may explain the variable composition of the slow solar wind.
A New Facility for Airborne Solar Astronomy: NASA's WB-57 at the 2017 Total Solar EclipseCaspi, AmirSeaton, Daniel B.Tsang, Constantine C. C.DeForest, Craig E.Bryans, PaulDeLuca, Edward E.Tomczyk, StevenBurkepile, Joan T.Casey, Thomas "Tony"Collier, JohnDarrow, Donald "DD"Del Rosso, DominicDurda, Daniel D.Gallagher, Peter T.Golub, LeonJacyna, MatthewJohnson, David "DJ"Judge, Philip G.Klemm, Cary "Diddle"Laurent, Glenn T.Lewis, JohannaMallini, Charles J.Parent, Thomas "Duster"Propp, TimothySteffl, Andrew J.Warner, JeffWest, Matthew J.Wiseman, JohnYates, MalloryZhukov, Andrei N.NASA WB-57 2017 Eclipse Observing TeamDOI: info:10.3847/1538-4357/ab89a8v. 895131
Caspi, Amir, Seaton, Daniel B., Tsang, Constantine C. C., DeForest, Craig E., Bryans, Paul, DeLuca, Edward E., Tomczyk, Steven, Burkepile, Joan T., Casey, Thomas "Tony", Collier, John, Darrow, Donald "DD", Del Rosso, Dominic, Durda, Daniel D., Gallagher, Peter T., Golub, Leon, Jacyna, Matthew, Johnson, David "DJ", Judge, Philip G., Klemm, Cary "Diddle", Laurent, Glenn T., Lewis, Johanna, Mallini, Charles J., Parent, Thomas "Duster", Propp, Timothy, Steffl, Andrew J. et al. 2020. "A New Facility for Airborne Solar Astronomy: NASA's WB-57 at the 2017 Total Solar Eclipse." The Astrophysical Journal 895:131.
ID: 156873
Type: article
Authors: Caspi, Amir; Seaton, Daniel B.; Tsang, Constantine C. C.; DeForest, Craig E.; Bryans, Paul; DeLuca, Edward E.; Tomczyk, Steven; Burkepile, Joan T.; Casey, Thomas "Tony"; Collier, John; Darrow, Donald "DD"; Del Rosso, Dominic; Durda, Daniel D.; Gallagher, Peter T.; Golub, Leon; Jacyna, Matthew; Johnson, David "DJ"; Judge, Philip G.; Klemm, Cary "Diddle"; Laurent, Glenn T.; Lewis, Johanna; Mallini, Charles J.; Parent, Thomas "Duster"; Propp, Timothy; Steffl, Andrew J.; Warner, Jeff; West, Matthew J.; Wiseman, John; Yates, Mallory; Zhukov, Andrei N.; NASA WB-57 2017 Eclipse Observing Team
Abstract: NASA's WB-57 High Altitude Research Program provides a deployable, mobile, and stratospheric platform for scientific research. Airborne platforms are of particular value for making coronal observations during total solar eclipses because of their ability both to follow the Moon's shadow and to get above most of the atmospheric air mass that can interfere with astronomical observations. We used the 2017 August 21 eclipse as a pathfinding mission for high-altitude airborne solar astronomy, using the existing high-speed visible-light and near/midwave infrared imaging suite mounted in the WB-57 nose cone. In this paper, we describe the aircraft, the instrument, and the 2017 mission; operations and data acquisition; and preliminary analysis of data quality from the existing instrument suite. We describe benefits and technical limitations of this platform for solar and other astronomical observations. We present a preliminary analysis of the visible-light data quality and discuss the limiting factors that must be overcome with future instrumentation. We conclude with a discussion of lessons learned from this pathfinding mission and prospects for future research at upcoming eclipses, as well as an evaluation of the capabilities of the WB-57 platform for future solar astronomy and general astronomical observation.
EUV imaging and spectroscopy for improved space weather forecastingGolub, LeonCheimets, PeterDeLuca, Edward E.Madsen, Chad A.Reeves, Katharine K.Samra, JennaSavage, SabrinaWinebarger, AmyBruccoleri, Alexander R.DOI: info:10.1051/swsc/2020040v. 10Article 37
Golub, Leon, Cheimets, Peter, DeLuca, Edward E., Madsen, Chad A., Reeves, Katharine K., Samra, Jenna, Savage, Sabrina, Winebarger, Amy, and Bruccoleri, Alexander R. 2020. "EUV imaging and spectroscopy for improved space weather forecasting." Journal of Space Weather and Space Climate 10:Article 37.
ID: 157469
Type: article
Authors: Golub, Leon; Cheimets, Peter; DeLuca, Edward E.; Madsen, Chad A.; Reeves, Katharine K.; Samra, Jenna; Savage, Sabrina; Winebarger, Amy; Bruccoleri, Alexander R.
Abstract: Accurate predictions of harmful space weather effects are mandatory for the protection of astronauts and other assets in space, whether in Earth or lunar orbit, in transit between solar system objects, or on the surface of other planetary bodies. Because the corona is multithermal (i.e., structured not only in space but also in temperature), wavelength-separated data provide crucial information that is not available to imaging methods that integrate over temperature. The extreme ultraviolet (EUV) wavelengths enable us to focus directly on high temperature coronal plasma associated with solar flares, coronal mass ejections (CMEs), and shocked material without being overwhelmed by intensity from the solar disk. Both wide-field imaging and spectroscopic observations of the solar corona taken from a variety of orbits (e.g., Earth, L1, or L5) using suitably-chosen EUV instrumentation offer the possibility of addressing two major goals to enhance our space weather prediction capability, namely: (1) Improve our understanding of the coronal conditions that control the opening and closing of the corona to the heliosphere and consequent solar wind streams, and (2) Improve our understanding of the physical processes that control the early evolution of CMEs and the formation of shocks, from the solar surface out into the extended corona.
Observation and Modeling of High-temperature Solar Active Region Emission during the High-resolution Coronal Imager Flight of 2018 May 29Warren, Harry P.Reep, Jeffrey W.Crump, Nicholas A.Ugarte-Urra, IgnacioBrooks, David H.Winebarger, Amy R.Savage, SabrinaDe Pontieu, BartPeter, HardiCirtain, Jonathan W.Golub, LeonKobayashi, KenMcKenzie, DavidMorton, RichardRachmeler, LaurelTesta, PaolaTiwari, SanjivWalsh, RobertDOI: info:10.3847/1538-4357/ab917cv. 89651
Warren, Harry P., Reep, Jeffrey W., Crump, Nicholas A., Ugarte-Urra, Ignacio, Brooks, David H., Winebarger, Amy R., Savage, Sabrina, De Pontieu, Bart, Peter, Hardi, Cirtain, Jonathan W., Golub, Leon, Kobayashi, Ken, McKenzie, David, Morton, Richard, Rachmeler, Laurel, Testa, Paola, Tiwari, Sanjiv, and Walsh, Robert. 2020. "Observation and Modeling of High-temperature Solar Active Region Emission during the High-resolution Coronal Imager Flight of 2018 May 29." The Astrophysical Journal 896:51.
ID: 157470
Type: article
Authors: Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.; Ugarte-Urra, Ignacio; Brooks, David H.; Winebarger, Amy R.; Savage, Sabrina; De Pontieu, Bart; Peter, Hardi; Cirtain, Jonathan W.; Golub, Leon; Kobayashi, Ken; McKenzie, David; Morton, Richard; Rachmeler, Laurel; Testa, Paola; Tiwari, Sanjiv; Walsh, Robert
Abstract: Excellent coordinated observations of NOAA active region 12712 were obtained during the flight of the High-resolution Coronal Imager (Hi-C) sounding rocket on 2018 May 29. This region displayed a typical active region core structure with relatively short, high-temperature loops crossing the polarity inversion line and bright "moss" located at the footpoints of these loops. The differential emission measure (DEM) in the active region core is very sharply peaked at about 4 MK. Further, there is little evidence for impulsive heating events in the moss, even at the high spatial resolution and cadence of Hi-C. This suggests that active region core heating is occurring at a high frequency and keeping the loops close to equilibrium. To create a time-dependent simulation of the active region core, we combine nonlinear force-free extrapolations of the measured magnetic field with a heating rate that is dependent on the field strength and loop length and has a Poisson waiting time distribution. We use the approximate solutions to the hydrodynamic loop equations to simulate the full ensemble of active region core loops for a range of heating parameters. In all cases, we find that high-frequency heating provides the best match to the observed DEM. For selected field lines, we solve the full hydrodynamic loop equations, including radiative transfer in the chromosphere, to simulate transition region and chromospheric emission. We find that for heating scenarios consistent with the DEM, classical signatures of energy release, such as transition region brightenings and chromospheric evaporation, are weak, suggesting that they would be difficult to detect.
LUCI onboard Lagrange, the next generation of EUV space weather monitoringWest, Matthew J.Kintziger, ChristianHaberreiter, MargitGyo, ManfredBerghmans, DavidGissot, SamuelBüchel, ValeriaGolub, LeonShestov, SergeiDavies, Jackie A.DOI: info:10.1051/swsc/202005v. 1049
West, Matthew J., Kintziger, Christian, Haberreiter, Margit, Gyo, Manfred, Berghmans, David, Gissot, Samuel, Büchel, Valeria, Golub, Leon, Shestov, Sergei, and Davies, Jackie A. 2020. "LUCI onboard Lagrange, the next generation of EUV space weather monitoring." Journal of Space Weather and Space Climate 10:49.
ID: 158889
Type: article
Authors: West, Matthew J.; Kintziger, Christian; Haberreiter, Margit; Gyo, Manfred; Berghmans, David; Gissot, Samuel; Büchel, Valeria; Golub, Leon; Shestov, Sergei; Davies, Jackie A.
Abstract: Lagrange eUv Coronal Imager (LUCI) is a solar imager in the Extreme UltraViolet (EUV) that is being developed as part of the Lagrange mission, a mission designed to be positioned at the L5 Lagrangian point to monitor space weather from its source on the Sun, through the heliosphere, to the Earth. LUCI will use an off-axis two mirror design equipped with an EUV enhanced active pixel sensor. This type of detector has advantages that promise to be very beneficial for monitoring the source of space weather in the EUV. LUCI will also have a novel off-axis wide field-of-view, designed to observe the solar disk, the lower corona, and the extended solar atmosphere close to the Sun-Earth line. LUCI will provide solar coronal images at a 2-3 min cadence in a pass-band centred on 19.5. Observations made through this pass-band allow for the detection and monitoring of semi-static coronal structures such as coronal holes, prominences, and active regions; as well as transient phenomena such as solar flares, limb coronal mass ejections (CMEs), EUV waves, and coronal dimmings. The LUCI data will complement EUV solar observations provided by instruments located along the Sun-Earth line such as PROBA2-SWAP, SUVI-GOES and SDO-AIA, as well as provide unique observations to improve space weather forecasts. Together with a suite of other remote-sensing and in-situ instruments onboard Lagrange, LUCI will provide science quality operational observations for space weather monitoring.
Is the High-Resolution Coronal Imager Resolving Coronal Strands? Results from AR 12712Williams, ThomasWalsh, Robert W.Winebarger, Amy R.Brooks, David H.Cirtain, Jonathan W.De Pontieu, BartGolub, LeonKobayashi, KenMcKenzie, David E.Morton, Richard J.Peter, HardiRachmeler, Laurel A.Savage, Sabrina L.Testa, PaolaTiwari, Sanjiv K.Warren, Harry P.Watkinson, Benjamin J.DOI: info:10.3847/1538-4357/ab6dcfv. 892134
Williams, Thomas, Walsh, Robert W., Winebarger, Amy R., Brooks, David H., Cirtain, Jonathan W., De Pontieu, Bart, Golub, Leon, Kobayashi, Ken, McKenzie, David E., Morton, Richard J., Peter, Hardi, Rachmeler, Laurel A., Savage, Sabrina L., Testa, Paola, Tiwari, Sanjiv K., Warren, Harry P., and Watkinson, Benjamin J. 2020. "Is the High-Resolution Coronal Imager Resolving Coronal Strands? Results from AR 12712." The Astrophysical Journal 892:134.
ID: 157291
Type: article
Authors: Williams, Thomas; Walsh, Robert W.; Winebarger, Amy R.; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; Golub, Leon; Kobayashi, Ken; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Rachmeler, Laurel A.; Savage, Sabrina L.; Testa, Paola; Tiwari, Sanjiv K.; Warren, Harry P.; Watkinson, Benjamin J.
Abstract: Following the success of the first mission, the High-Resolution Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1) on 2018 May 29 from the White Sands Missile Range, NM, USA. On this occasion, 329 s of 17.2 nm data of target active region AR 12712 were captured with a cadence of ≈4 s, and a plate scale of 0.129 arcsec pixel-1. Using data captured by Hi-C 2.1 and co-aligned observations from SDO/AIA 17.1 nm, we investigate the widths of 49 coronal strands. We search for evidence of substructure within the strands that is not detected by AIA, and further consider whether these strands are fully resolved by Hi-C 2.1. With the aid of multi-scale Gaussian normalization, strands from a region of low emission that can only be visualized against the contrast of the darker, underlying moss are studied. A comparison is made between these low-emission strands and those from regions of higher emission within the target active region. It is found that Hi-C 2.1 can resolve individual strands as small as ≈202 km, though the more typical strand widths seen are ≈513 km. For coronal strands within the region of low emission, the most likely width is significantly narrower than the high- emission strands at ≈388 km. This places the low-emission coronal strands beneath the resolving capabilities of SDO/AIA, highlighting the need for a permanent solar observatory with the resolving power of Hi-C.
Solar Active Region Heating Diagnostics from High-temperature Emission Using the MaGIXSAthiray, P. S.Winebarger, Amy R.Barnes, Will T.Bradshaw, Stephen J.Savage, SabrinaWarren, Harry P.Kobayashi, KenChampey, PatrickGolub, LeonGlesener, LindsayDOI: info:10.3847/1538-4357/ab3eb4v. 88424
Athiray, P. S., Winebarger, Amy R., Barnes, Will T., Bradshaw, Stephen J., Savage, Sabrina, Warren, Harry P., Kobayashi, Ken, Champey, Patrick, Golub, Leon, and Glesener, Lindsay. 2019. "Solar Active Region Heating Diagnostics from High-temperature Emission Using the MaGIXS." The Astrophysical Journal 884:24.
ID: 154626
Type: article
Authors: Athiray, P. S.; Winebarger, Amy R.; Barnes, Will T.; Bradshaw, Stephen J.; Savage, Sabrina; Warren, Harry P.; Kobayashi, Ken; Champey, Patrick; Golub, Leon; Glesener, Lindsay
Abstract: The relative amount of high-temperature plasma has been found to be a useful diagnostic to determine the frequency of coronal heating on sub- resolution structures. When the loops are infrequently heated, a broad emission measure (EM) over a wider range of temperatures is expected. A narrower EM is expected for high-frequency heating where the loops are closer to equilibrium. The soft X-ray spectrum contains many spectral lines that provide high-temperature diagnostics, including lines from Fe XVII-XIX. This region of the solar spectrum will be observed by the Marshall Grazing Incidence Spectrometer (MaGIXS) in 2020. In this paper, we derive the expected spectral line intensity in MaGIXS to varying amounts of high-temperature plasma to demonstrate that a simple line ratio provides a powerful diagnostic to determine the heating frequency. Similarly, we examine ratios of AIA channel intensities, filter ratios from a XRT, and energy bands from the FOXSI sounding rocket to determine their sensitivity to this parameter. We find that both FOXSI and MaGIXS provide good diagnostic capabilities for high-temperature plasma. We then compare the predicted line ratios to the output of a numerical model and confirm that the MaGIXS ratios provide an excellent diagnostic for heating frequency.
Signatures of the non-Maxwellian κ-distributions in optically thin line spectra. II. Synthetic Fe XVII-XVIII X-ray coronal spectra and predictions for the Marshall Grazing-Incidence X-ray Spectrometer (MaGIXS)Dudík, JaroslavDzifčáková, ElenaDel Zanna, GiulioMason, Helen E.Golub, Leon L.Winebarger, Amy R.Savage, Sabrina L.DOI: info:10.1051/0004-6361/201935285v. 626A88
Dudík, Jaroslav, Dzifčáková, Elena, Del Zanna, Giulio, Mason, Helen E., Golub, Leon L., Winebarger, Amy R., and Savage, Sabrina L. 2019. "Signatures of the non-Maxwellian κ-distributions in optically thin line spectra. II. Synthetic Fe XVII-XVIII X-ray coronal spectra and predictions for the Marshall Grazing-Incidence X-ray Spectrometer (MaGIXS)." Astronomy and Astrophysics 626:A88.
ID: 152900
Type: article
Authors: Dudík, Jaroslav; Dzifčáková, Elena; Del Zanna, Giulio; Mason, Helen E.; Golub, Leon L.; Winebarger, Amy R.; Savage, Sabrina L.
Abstract: Aims: We investigated the possibility of diagnosing the degree of departure from the Maxwellian distribution using the Fe XVII-Fe XVIII spectra originating in plasmas in collisional ionization equilibrium, such as in the cores of solar active regions or microflares. Methods: The original collision strengths for excitation are integrated over the non-Maxwellian electron κ-distributions characterized by a high-energy tail. Synthetic X-ray emission line spectra were calculated for a range of temperatures and κ. We focus on the 6-24 Å spectral range to be observed by the upcoming Marshall Grazing-Incidence X-ray Spectrometer MaGIXS. Results: We find that many line intensity ratios are sensitive to both T and κ. Best diagnostic options are provided if a ratio involving both Fe XVII and Fe XVIII is combined with another ratio involving lines formed within a single ion. The sensitivity of such diagnostics to κ is typically a few tens of per cent. Much larger sensitivity, of about a factor of two to three, can be obtained if the Fe XVIII 93.93 Å line observed by SDO/AIA is used in conjuction with the X-ray lines. Conclusions: We conclude that the MaGIXS instrument is well-suited for detection of departures from the Maxwellian distribution, especially in active region cores.
Solar Eclipse Observations from the Ground and Air from 0.31 to 5.5 MicronsJudge, PhilipBerkey, BenBoll, AlyssaBryans, PaulBurkepile, JoanCheimets, PeterDeLuca, Edwardde Toma, GiulianaGibson, KeonGolub, LeonHannigan, JamesMadsen, ChadMarquez, VanessaRichards, AustinSamra, JennaSewell, ScottTomczyk, StevenVera, AlyshaDOI: info:10.1007/s11207-019-1550-3v. 294166
Judge, Philip, Berkey, Ben, Boll, Alyssa, Bryans, Paul, Burkepile, Joan, Cheimets, Peter, DeLuca, Edward, de Toma, Giuliana, Gibson, Keon, Golub, Leon, Hannigan, James, Madsen, Chad, Marquez, Vanessa, Richards, Austin, Samra, Jenna, Sewell, Scott, Tomczyk, Steven, and Vera, Alysha. 2019. "Solar Eclipse Observations from the Ground and Air from 0.31 to 5.5 Microns." Solar Physics 294:166.
ID: 154582
Type: article
Authors: Judge, Philip; Berkey, Ben; Boll, Alyssa; Bryans, Paul; Burkepile, Joan; Cheimets, Peter; DeLuca, Edward; de Toma, Giuliana; Gibson, Keon; Golub, Leon; Hannigan, James; Madsen, Chad; Marquez, Vanessa; Richards, Austin; Samra, Jenna; Sewell, Scott; Tomczyk, Steven; Vera, Alysha
Abstract: We present spectra and broad-band polarized light data from a novel suite of instruments deployed during the 21st August 2017 total solar eclipse. Our goals were to survey solar spectra at thermal infrared wavelengths during eclipse, and to test new technology for measuring polarized coronal light. An infrared coronal imaging spectrometer, flown at 14.3 km altitude above Kentucky, was supported on the ground by observations from Madras, Oregon (elevation 683 m) and Camp Wyoba on Casper Mountain, Wyoming (2402 m). In Wyoming we deployed a new infrared Fourier Transform Spectrometer (FTS), three low-dispersion spectrometers loaned to us by Avantes, a novel visible-light camera PolarCam, sensitive to linear polarization, and one of two infrared cameras from FLIR Systems, the other operated at Madras. Circumstances of eclipse demanded that the observations spanned 17:19 to 18:26 UT. We analyze spectra of the limb photosphere, the chromosphere, prominences, and coronal lines from 310 nm to 5.5 μm. We calibrated data photometrically using the solar disk as a source. Between different spectrometers, the calibrations were consistent to better than 13%. But the sensitivities achieved were insufficient to detect coronal lines from the ground. The PolarCam data are in remarkable agreement with polarization data from the K-Cor synoptic instrument on Mauna Loa, and with FLIR intensity data acquired in Madras. We discuss new results, including a detection of the He uc(i) 1083 nm multiplet in emission during the whole of totality. The combination of the FTS and AIR-Spec spectra reveals for the first time the effects of the telluric extinction on the infrared coronal emission lines, to be observed with upcoming Daniel K. Inouye Solar Telescope.
Alfvénic velocity spikes and rotational flows in the near-Sun solar windKasper, Justin C.Bale, S. D.Belcher, J. W.Berthomier, M.Case, Anthony W.Chandran, B. D. G.Curtis, D. W.Gallagher, D.Gary, S. P.Golub, LeonHalekas, J. S.Ho, G. C.Horbury, T. S.Hu, Q.Huang, J.Klein, K. G.Korreck, Kelly E.Larson, D. E.Livi, R.Maruca, B.Lavraud, B.Louarn, P.Maksimovic, M.Martinovic, M.McGinnis, D.Pogorelov, N. V.Richardson, J. D.Skoug, R. M.Steinberg, J. T.Stevens, Michael L.Szabo, A.Velli, M.Whittlesey, P. L.Wright, K. H.Zank, G. P.MacDowall, R. J.McComas, D. J.McNutt, R. L.Pulupa, M.Raouafi, N. E.Schwadron, N. A.DOI: info:10.1038/s41586-019-1813-zv. 576228–231
Kasper, Justin C., Bale, S. D., Belcher, J. W., Berthomier, M., Case, Anthony W., Chandran, B. D. G., Curtis, D. W., Gallagher, D., Gary, S. P., Golub, Leon, Halekas, J. S., Ho, G. C., Horbury, T. S., Hu, Q., Huang, J., Klein, K. G., Korreck, Kelly E., Larson, D. E., Livi, R., Maruca, B., Lavraud, B., Louarn, P., Maksimovic, M., Martinovic, M., McGinnis, D. et al. 2019. "Alfvénic velocity spikes and rotational flows in the near-Sun solar wind." Nature 576:228– 231.
ID: 155111
Type: article
Authors: Kasper, Justin C.; Bale, S. D.; Belcher, J. W.; Berthomier, M.; Case, Anthony W.; Chandran, B. D. G.; Curtis, D. W.; Gallagher, D.; Gary, S. P.; Golub, Leon; Halekas, J. S.; Ho, G. C.; Horbury, T. S.; Hu, Q.; Huang, J.; Klein, K. G.; Korreck, Kelly E.; Larson, D. E.; Livi, R.; Maruca, B.; Lavraud, B.; Louarn, P.; Maksimovic, M.; Martinovic, M.; McGinnis, D.; Pogorelov, N. V.; Richardson, J. D.; Skoug, R. M.; Steinberg, J. T.; Stevens, Michael L.; Szabo, A.; Velli, M.; Whittlesey, P. L.; Wright, K. H.; Zank, G. P.; MacDowall, R. J.; McComas, D. J.; McNutt, R. L.; Pulupa, M.; Raouafi, N. E.; Schwadron, N. A.
Abstract: The prediction of a supersonic solar wind1 was first confirmed by spacecraft near Earth2,3 and later by spacecraft at heliocentric distances as small as 62 solar radii4. These missions showed that plasma accelerates as it emerges from the corona, aided by unidentified processes that transport energy outwards from the Sun before depositing it in the wind. Alfvénic fluctuations are a promising candidate for such a process because they are seen in the corona and solar wind and contain considerable energy5-7. Magnetic tension forces the corona to co-rotate with the Sun, but any residual rotation far from the Sun reported until now has been much smaller than the amplitude of waves and deflections from interacting wind streams8. Here we report observations of solar-wind plasma at heliocentric distances of about 35 solar radii9-11, well within the distance at which stream interactions become important. We find that Alfvén waves organize into structured velocity spikes with duration of up to minutes, which are associated with propagating S-like bends in the magnetic-field lines. We detect an increasing rotational component to the flow velocity of the solar wind around the Sun, peaking at 35 to 50 kilometres per second-considerably above the amplitude of the waves. These flows exceed classical velocity predictions of a few kilometres per second, challenging models of circulation in the corona and calling into question our understanding of how stars lose angular momentum and spin down as they age12-14.
New deep coronal spectra from the 2017 total solar eclipseKoutchmy, S.Baudin, F.Abdi, ShGolub, LeonSèvre, F.DOI: info:10.1051/0004-6361/201935681v. 632A86
Koutchmy, S., Baudin, F., Abdi, Sh, Golub, Leon, and Sèvre, F. 2019. "New deep coronal spectra from the 2017 total solar eclipse." Astronomy and Astrophysics 632:A86.
ID: 154529
Type: article
Authors: Koutchmy, S.; Baudin, F.; Abdi, Sh; Golub, Leon; Sèvre, F.
Abstract: Context. The origin of the high temperature of the solar corona, in both the inner bright parts and the more outer parts showing flows toward the solar wind, is not understood well yet. Total eclipses permit a deep analysis of both the inner and the outer parts of the corona using the continuum white-light (W-L) radiations from electrons (K-corona), the superposed spectrum of forbidden emission lines from ions (E-corona), and the dust component with F-lines (F-corona). Aims: By sufficiently dispersing the W-L spectrum, the Fraunhofer (F) spectrum of the dust component of the corona appears and the continuum Thomson radiation can be evaluated. The superposed emission lines of ions with different degrees of ionization are studied to allow the measurement of temperatures, non-thermal velocities, Doppler shifts, and abundances to constrain the proposed heating mechanisms and understand the origin of flows that lead to solar wind. Methods: We describe a slit spectroscopic experiment of high spectral resolution to provide an analysis of the most typical parts of the quasi-minimum type corona observed during the total solar eclipse of Aug. 21, 2017 from Idaho, USA. Streamers, active region enhancements, and polar coronal holes (CHs) are measured well using deep spectra. Results: Sixty spectra are obtained during the totality with a long slit, covering ±3 solar radii in the range of 510 nm to 590 nm. The K+F continuum corona is exposed well up to two solar radii. The F-corona can be measured even at the solar limb. New weak emission lines were discovered or confirmed. The rarely observed Ar X line is detected almost everywhere; the Fe XIV and Ni XIII lines are clearly detected everywhere. For the first time hot lines are also measured inside the CH regions. The radial variations of the non-thermal turbulent velocities of the lines do not show a great departure from the average values. No significantly large Doppler shifts are seen anywhere in the inner or the middle corona. The wings of the Fe XIV line show some non-Gaussianity. Conclusions: Deep slit coronal spectra offered an opportunity for diagnosing several aspects of coronal physics during a well observed total eclipse without extended investments. The analysis of the ionic emission line profiles offers several powerful diagnostics of the coronal dynamics; the precise measurement of the F-continuum component provides insight into the ubiquitous dust corona at the solar limb.
The High-Resolution Coronal Imager, Flight 2.1Rachmeler, Laurel A.Winebarger, Amy R.Savage, Sabrina L.Golub, LeonKobayashi, KenVigil, Genevieve D.Brooks, David H.Cirtain, Jonathan W.De Pontieu, BartMcKenzie, David E.Morton, Richard J.Peter, HardiTesta, PaolaTiwari, Sanjiv K.Walsh, Robert W.Warren, Harry P.Alexander, CarolineAnsell, DarrenBeabout, Brent L.Beabout, Dyana L.Bethge, Christian W.Champey, Patrick R.Cheimets, Peter N.Cooper, Mark A.Creel, Helen K.Gates, RichardGomez, CarlosGuillory, AnthonyHaight, HarlanHogue, William D.Holloway, ToddHyde, David W.Kenyon, RichardMarshall, Joseph N.McCracken, Jeff E.McCracken, KennethMitchell, Karen O.Ordway, MarkOwen, TimRanganathan, JaganRobertson, Bryan A.Payne, M. JaniePodgorski, WilliamPryor, JonathanSamra, JennaSloan, Mark D.Soohoo, Howard A.Steele, D. BrandonThompson, Furman V.Thornton, Gary S.Watkinson, BenjaminWindt, DavidDOI: info:10.1007/s11207-019-1551-2v. 294174
Rachmeler, Laurel A., Winebarger, Amy R., Savage, Sabrina L., Golub, Leon, Kobayashi, Ken, Vigil, Genevieve D., Brooks, David H., Cirtain, Jonathan W., De Pontieu, Bart, McKenzie, David E., Morton, Richard J., Peter, Hardi, Testa, Paola, Tiwari, Sanjiv K., Walsh, Robert W., Warren, Harry P., Alexander, Caroline, Ansell, Darren, Beabout, Brent L., Beabout, Dyana L., Bethge, Christian W., Champey, Patrick R., Cheimets, Peter N., Cooper, Mark A., Creel, Helen K. et al. 2019. "The High-Resolution Coronal Imager, Flight 2.1." Solar Physics 294:174.
ID: 154524
Type: article
Authors: Rachmeler, Laurel A.; Winebarger, Amy R.; Savage, Sabrina L.; Golub, Leon; Kobayashi, Ken; Vigil, Genevieve D.; Brooks, David H.; Cirtain, Jonathan W.; De Pontieu, Bart; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Testa, Paola; Tiwari, Sanjiv K.; Walsh, Robert W.; Warren, Harry P.; Alexander, Caroline; Ansell, Darren; Beabout, Brent L.; Beabout, Dyana L.; Bethge, Christian W.; Champey, Patrick R.; Cheimets, Peter N.; Cooper, Mark A.; Creel, Helen K.; Gates, Richard; Gomez, Carlos; Guillory, Anthony; Haight, Harlan; Hogue, William D.; Holloway, Todd; Hyde, David W.; Kenyon, Richard; Marshall, Joseph N.; McCracken, Jeff E.; McCracken, Kenneth; Mitchell, Karen O.; Ordway, Mark; Owen, Tim; Ranganathan, Jagan; Robertson, Bryan A.; Payne, M. Janie; Podgorski, William; Pryor, Jonathan; Samra, Jenna; Sloan, Mark D.; Soohoo, Howard A.; Steele, D. Brandon; Thompson, Furman V.; Thornton, Gary S.; Watkinson, Benjamin; Windt, David
Abstract: The third flight of the High-Resolution Coronal Imager (Hi-C 2.1) occurred on May 29, 2018; the Sounding Rocket was launched from White Sands Missile Range in New Mexico. The instrument has been modified from its original configuration (Hi-C 1) to observe the solar corona in a passband that peaks near 172 Å, and uses a new, custom-built low-noise camera. The instrument targeted Active Region 12712, and captured 78 images at a cadence of 4.4 s (18:56:22 - 19:01:57 UT; 5 min and 35 s observing time). The image spatial resolution varies due to quasi- periodic motion blur from the rocket; sharp images contain resolved features of at least 0.47 arcsec. There are coordinated observations from multiple ground- and space-based telescopes providing an unprecedented opportunity to observe the mass and energy coupling between the chromosphere and the corona. Details of the instrument and the data set are presented in this paper.
Fine-scale Explosive Energy Release at Sites of Prospective Magnetic Flux Cancellation in the Core of the Solar Active Region Observed by Hi-C 2.1, IRIS, and SDOTiwari, Sanjiv K.Panesar, Navdeep K.Moore, Ronald L.De Pontieu, BartWinebarger, Amy R.Golub, LeonSavage, Sabrina L.Rachmeler, Laurel A.Kobayashi, KenTesta, PaolaWarren, Harry P.Brooks, David H.Cirtain, Jonathan W.McKenzie, David E.Morton, Richard J.Peter, HardiWalsh, Robert W.DOI: info:10.3847/1538-4357/ab54c1v. 88756
Tiwari, Sanjiv K., Panesar, Navdeep K., Moore, Ronald L., De Pontieu, Bart, Winebarger, Amy R., Golub, Leon, Savage, Sabrina L., Rachmeler, Laurel A., Kobayashi, Ken, Testa, Paola, Warren, Harry P., Brooks, David H., Cirtain, Jonathan W., McKenzie, David E., Morton, Richard J., Peter, Hardi, and Walsh, Robert W. 2019. "Fine-scale Explosive Energy Release at Sites of Prospective Magnetic Flux Cancellation in the Core of the Solar Active Region Observed by Hi-C 2.1, IRIS, and SDO." The Astrophysical Journal 887:56.
ID: 154545
Type: article
Authors: Tiwari, Sanjiv K.; Panesar, Navdeep K.; Moore, Ronald L.; De Pontieu, Bart; Winebarger, Amy R.; Golub, Leon; Savage, Sabrina L.; Rachmeler, Laurel A.; Kobayashi, Ken; Testa, Paola; Warren, Harry P.; Brooks, David H.; Cirtain, Jonathan W.; McKenzie, David E.; Morton, Richard J.; Peter, Hardi; Walsh, Robert W.
Abstract: The second Hi-C flight (Hi-C 2.1) provided unprecedentedly high spatial and temporal resolution (∼250 km, 4.4 s) coronal EUV images of Fe IX/X emission at 172 Å of AR 12712 on 2018 May 29, during 18:56:21─19:01:56 UT. Three morphologically different types (I: dot-like; II: loop-like III: surge/jet-like) of fine-scale sudden-brightening events (tiny microflares) are seen within and at the ends of an arch filament system in the core of the AR. Although type Is (not reported before) resemble IRIS bombs (in size, and brightness with respect to surroundings), our dot-like events are apparently much hotter and shorter in span (70 s). We complement the 5 minute duration Hi-C 2.1 data with SDO/HMI magnetograms, SDO/AIA EUV images, and IRIS UV spectra and slit-jaw images to examine, at the sites of these events, brightenings and flows in the transition region and corona and evolution of magnetic flux in the photosphere. Most, if not all, of the events are seated at sites of opposite-polarity magnetic flux convergence (sometimes driven by adjacent flux emergence), implying likely flux cancellation at the microflare's polarity inversion line. In the IRIS spectra and images, we find confirming evidence of field-aligned outflow from brightenings at the ends of loops of the arch filament system. In types I and II the explosion is confined, while in type III the explosion is ejective and drives jet-like outflow. The light curves from Hi-C, AIA, and IRIS peak nearly simultaneously for many of these events, and none of the events display a systematic cooling sequence as seen in typical coronal flares, suggesting that these tiny brightening events have chromospheric/transition region origin.
Unfolding Overlapped Slitless Imaging Spectrometer Data for Extended SourcesWinebarger, Amy R.Weber, MarkBethge, ChristianDowns, CooperGolub, LeonDeLuca, EdwardSavage, SabrinaZanna, Giulio delSamra, JennaMadsen, ChadAshraf, AfraCarter, CourtneyDOI: info:10.3847/1538-4357/ab21dbv. 882No. 112
Winebarger, Amy R., Weber, Mark, Bethge, Christian, Downs, Cooper, Golub, Leon, DeLuca, Edward, Savage, Sabrina, Zanna, Giulio del, Samra, Jenna, Madsen, Chad, Ashraf, Afra, and Carter, Courtney. 2019. "Unfolding Overlapped Slitless Imaging Spectrometer Data for Extended Sources." The Astrophysical Journal 882 (1):12.
ID: 152609
Type: article
Authors: Winebarger, Amy R.; Weber, Mark; Bethge, Christian; Downs, Cooper; Golub, Leon; DeLuca, Edward; Savage, Sabrina; Zanna, Giulio del; Samra, Jenna; Madsen, Chad; Ashraf, Afra; Carter, Courtney
Abstract: Slitless spectrometers can provide simultaneous imaging and spectral data over an extended field of view, thereby allowing rapid data acquisition for extended sources. In some instances, when the object is greatly extended or the spectral dispersion is too small, there may be locations in the focal plane where emission lines at different wavelengths contribute. It is then desirable to unfold the overlapped regions in order to isolate the contributions from the individual wavelengths. In this paper, we describe a method for such an unfolding, using an inversion technique developed for an extreme ultraviolet imaging spectrometer and coronagraph named the COronal Spectroscopic Imager in the EUV (COSIE). The COSIE spectrometer wavelength range (18.6-20.5 nm) contains a number of strong coronal emission lines and several density sensitive lines. We focus on optimizing the unfolding process to retrieve emission measure maps at constant temperature, maps of spectrally pure intensity in the Fe XII and Fe XIII lines, and density maps based on both Fe XII and Fe XIII diagnostics.
Predicting the COSIE-C Signal from the Outer Corona up to 3 Solar RadiiDel Zanna, GiulioRaymond, JohnAndretta, VincenzoTelloni, DanieleGolub, LeonDOI: info:10.3847/1538-4357/aadcf1v. 865132
Del Zanna, Giulio, Raymond, John, Andretta, Vincenzo, Telloni, Daniele, and Golub, Leon. 2018. "Predicting the COSIE-C Signal from the Outer Corona up to 3 Solar Radii." The Astrophysical Journal 865:132.
ID: 149395
Type: article
Authors: Del Zanna, Giulio; Raymond, John; Andretta, Vincenzo; Telloni, Daniele; Golub, Leon
Abstract: We present estimates of the signal to be expected in quiescent solar conditions, as would be obtained with the COronal Spectrographic Imager in the EUV in its coronagraphic mode (COSIE-C). COSIE-C has been proposed to routinely observe the relatively unexplored outer corona, where we know that many fundamental processes affecting both the lower corona and the solar wind are taking place. The COSIE-C spectral band, 186–205 Å, is well-known as it has been observed with Hinode EIS. We present Hinode EIS observations that we obtained in 2007 out to 1.5 R , to show that this spectral band in quiescent streamers is dominated by Fe XII and Fe XI and that the ionization temperature is nearly constant. To estimate the COSIE-C signal in the 1.5–3.1 R region we use a model based on CHIANTI atomic data and SoHO UVCS observations in the Si XII and Mg X coronal lines of two quiescent 1996 streamers. We reproduce the observed EUV radiances with a simple density model, photospheric abundances, and a constant temperature of 1.4 MK. We show that other theoretical or semi-empirical models fail to reproduce the observations. We find that the coronal COSIE-C signal at 3 R should be about 5 counts/s per 3.″1 pixel in quiescent streamers. This is unprecedented and opens up a significant discovery space. We also briefly discuss stray light and the visibility of other solar features. In particular, we present UVCS observations of an active region streamer, indicating increased signal compared to the quiet Sun cases.
Polar Coronal Plumes as Tornado-like JetsTavabi, E.Koutchmy, S.Golub, L.DOI: info:10.3847/1538-4357/aadc64v. 86635
Tavabi, E., Koutchmy, S., and Golub, L. 2018. "Polar Coronal Plumes as Tornado-like Jets." The Astrophysical Journal 866:35.
ID: 149386
Type: article
Authors: Tavabi, E.; Koutchmy, S.; Golub, L.
Abstract: We examine the dynamical behavior of white-light polar-plume structures in the inner corona that are observed from the ground during total solar eclipses, based on their extreme ultraviolet (EUV) hot and cool emission line counterparts observed from space. EUV observations from Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) of a sequence of rapidly varying coronal hole structures are analyzed. Evidence of events showing acceleration in the 1.25 Mk line of Fe XII at 193 Å is given. The structures along the plume show an outward velocity of about 140 km s‑1 that can be interpreted as an upward propagating wave in the 304 Å and 171 Å lines; higher speeds are seen in 193 Å (up to 1000 km s‑1). The ejection of the cold He II plasma is delayed by about 4 minutes in the lowest layer and is delayed more than 12 minutes in the highest level compared to the hot 193 Å behavior. A study of the dynamics using time-slice diagrams reveals that a large amount of fast ejected material originates from below the plume, at the footpoints. The release of plasma material appears to come from a cylinder with quasi-parallel edge-enhanced walls. After the initial phase of a longitudinal acceleration, the speed substantially reduces, and the ejecta disperse into the environment. Finally, the detailed temporal and spatial relationships between the cool and hot components were studied with simultaneous multiwavelength observations, using more AIA data. The outward-propagating perturbation of the presumably magnetic walls of polar plumes supports the suggestion that Alfvén waves propagate outwardly along these radially extended walls.
Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe PlusKasper, Justin C.Abiad, RobertAustin, GerryBalat-Pichelin, MarianneBale, Stuart D.Belcher, John W.Berg, PeterBergner, HenryBerthomier, MatthieuBookbinder, JayBrodu, EtienneCaldwell, DavidCase, Anthony W.Chandran, Benjamin D. G.Cheimets, PeterCirtain, Jonathan W.Cranmer, Steven R.Curtis, David W.Daigneau, PeterDalton, GregDasgupta, BrahmanandaDeTomaso, DavidDiaz-Aguado, MillanDjordjevic, BlagojeDonaskowski, BillEffinger, MichaelFlorinski, VladimirFox, NicholaFreeman, MarkGallagher, DennisGary, S. PeterGauron, TomGates, RichardGoldstein, MelvinGolub, LeonGordon, Dorothy A.Gurnee, ReidGuth, GioraHalekas, JasperHatch, KenHeerikuisen, JacobHo, GeorgeHu, QiangJohnson, GregJordan, Steven P.Korreck, Kelly E.Larson, DavinLazarus, Alan J.Li, GangLivi, RobertoLudlam, MichaelMaksimovic, MilanMcFadden, James P.Marchant, WilliamMaruca, Bennet A.McComas, David J.Messina, LucianaMercer, TonyPark, SangPeddie, Andrew M.Pogorelov, NikolaiReinhart, Matthew J.Richardson, John D.Robinson, MilesRosen, IreneSkoug, Ruth M.Slagle, AmandaSteinberg, John T.Stevens, Michael L.Szabo, AdamTaylor, Ellen R.Tiu, ChrisTurin, PaulVelli, MarcoWebb, GaryWhittlesey, PhyllisWright, KenWu, S. T.Zank, GaryDOI: info:10.1007/s11214-015-0206-3v. 204131–186
Kasper, Justin C., Abiad, Robert, Austin, Gerry, Balat-Pichelin, Marianne, Bale, Stuart D., Belcher, John W., Berg, Peter, Bergner, Henry, Berthomier, Matthieu, Bookbinder, Jay, Brodu, Etienne, Caldwell, David, Case, Anthony W., Chandran, Benjamin D. G., Cheimets, Peter, Cirtain, Jonathan W., Cranmer, Steven R., Curtis, David W., Daigneau, Peter, Dalton, Greg, Dasgupta, Brahmananda, DeTomaso, David, Diaz-Aguado, Millan, Djordjevic, Blagoje, Donaskowski, Bill et al. 2016. "Solar Wind Electrons Alphas and Protons (SWEAP) Investigation: Design of the Solar Wind and Coronal Plasma Instrument Suite for Solar Probe Plus." Space Science Reviews 204:131– 186.
ID: 141934
Type: article
Authors: Kasper, Justin C.; Abiad, Robert; Austin, Gerry; Balat-Pichelin, Marianne; Bale, Stuart D.; Belcher, John W.; Berg, Peter; Bergner, Henry; Berthomier, Matthieu; Bookbinder, Jay; Brodu, Etienne; Caldwell, David; Case, Anthony W.; Chandran, Benjamin D. G.; Cheimets, Peter; Cirtain, Jonathan W.; Cranmer, Steven R.; Curtis, David W.; Daigneau, Peter; Dalton, Greg; Dasgupta, Brahmananda; DeTomaso, David; Diaz-Aguado, Millan; Djordjevic, Blagoje; Donaskowski, Bill; Effinger, Michael; Florinski, Vladimir; Fox, Nichola; Freeman, Mark; Gallagher, Dennis; Gary, S. Peter; Gauron, Tom; Gates, Richard; Goldstein, Melvin; Golub, Leon; Gordon, Dorothy A.; Gurnee, Reid; Guth, Giora; Halekas, Jasper; Hatch, Ken; Heerikuisen, Jacob; Ho, George; Hu, Qiang; Johnson, Greg; Jordan, Steven P.; Korreck, Kelly E.; Larson, Davin; Lazarus, Alan J.; Li, Gang; Livi, Roberto; Ludlam, Michael; Maksimovic, Milan; McFadden, James P.; Marchant, William; Maruca, Bennet A.; McComas, David J.; Messina, Luciana; Mercer, Tony; Park, Sang; Peddie, Andrew M.; Pogorelov, Nikolai; Reinhart, Matthew J.; Richardson, John D.; Robinson, Miles; Rosen, Irene; Skoug, Ruth M.; Slagle, Amanda; Steinberg, John T.; Stevens, Michael L.; Szabo, Adam; Taylor, Ellen R.; Tiu, Chris; Turin, Paul; Velli, Marco; Webb, Gary; Whittlesey, Phyllis; Wright, Ken; Wu, S. T.; Zank, Gary
Abstract: The Solar Wind Electrons Alphas and Protons (SWEAP) Investigation on Solar Probe Plus is a four sensor instrument suite that provides complete measurements of the electrons and ionized helium and hydrogen that constitute the bulk of solar wind and coronal plasma. SWEAP consists of the Solar Probe Cup (SPC) and the Solar Probe Analyzers (SPAN). SPC is a Faraday Cup that looks directly at the Sun and measures ion and electron fluxes and flow angles as a function of energy. SPAN consists of an ion and electron electrostatic analyzer (ESA) on the ram side of SPP (SPAN-A) and an electron ESA on the anti-ram side (SPAN-B). The SPAN-A ion ESA has a time of flight section that enables it to sort particles by their mass/charge ratio, permitting differentiation of ion species. SPAN-A and -B are rotated relative to one another so their broad fields of view combine like the seams on a baseball to view the entire sky except for the region obscured by the heat shield and covered by SPC. Observations by SPC and SPAN produce the combined field of view and measurement capabilities required to fulfill the science objectives of SWEAP and Solar Probe Plus. SWEAP measurements, in concert with magnetic and electric fields, energetic particles, and white light contextual imaging will enable discovery and understanding of solar wind acceleration and formation, coronal and solar wind heating, and particle acceleration in the inner heliosphere of the solar system. SPC and SPAN are managed by the SWEAP Electronics Module (SWEM), which distributes power, formats onboard data products, and serves as a single electrical interface to the spacecraft. SWEAP data products include ion and electron velocity distribution functions with high energy and angular resolution. Full resolution data are stored within the SWEM, enabling high resolution observations of structures such as shocks, reconnection events, and other transient structures to be selected for download after the fact. This paper describes the implementation of the SWEAP Investigation, the driving requirements for the suite, expected performance of the instruments, and planned data products, as of mission preliminary design review.
Simultaneous IRIS and Hinode/EIS Observations and Modelling of the 2014 October 27 X2.0 Class FlarePolito, V.Reep, J. W.Reeves, Katharine K.Simões, P. J. A.Dudík, J.Del Zanna, G.Mason, H. E.Golub, L.DOI: info:10.3847/0004-637X/816/2/89v. 81689
Polito, V., Reep, J. W., Reeves, Katharine K., Simões, P. J. A., Dudík, J., Del Zanna, G., Mason, H. E., and Golub, L. 2016. "Simultaneous IRIS and Hinode/EIS Observations and Modelling of the 2014 October 27 X2.0 Class Flare." The Astrophysical Journal 816:89.
ID: 138776
Type: article
Authors: Polito, V.; Reep, J. W.; Reeves, Katharine K.; Simões, P. J. A.; Dudík, J.; Del Zanna, G.; Mason, H. E.; Golub, L.
Abstract: We present a study of the X2-class flare which occurred on 2014 October 27 and was observed with the Interface Region Imaging Spectrograph (IRIS) and the EUV Imaging Spectrometer (EIS) on board the Hinode satellite. Thanks to the high cadence and spatial resolution of the IRIS and EIS instruments, we are able to compare simultaneous observations of the Fe xxi 1354.08 Å and Fe xxiii 263.77 Å high-temperature emission (?10 MK) in the flare ribbon during the chromospheric evaporation phase. We find that IRIS observes completely blueshifted Fe xxi line profiles, up to 200 km s-1 during the rise phase of the flare, indicating that the site of the plasma upflows is resolved by IRIS. In contrast, the Fe xxiii line is often asymmetric, which we interpret as being due to the lower spatial resolution of EIS. Temperature estimates from SDO/AIA and Hinode/XRT show that hot emission (log(T[K]) > 7.2) is first concentrated at the footpoints before filling the loops. Density-sensitive lines from IRIS and EIS give estimates of electron number density of ?1012 cm-3 in the transition region lines and 1010 cm-3 in the coronal lines during the impulsive phase. In order to compare the observational results against theoretical predictions, we have run a simulation of a flare loop undergoing heating using the HYDRAD 1D hydro code. We find that the simulated plasma parameters are close to the observed values that are obtained with IRIS, Hinode, and AIA. These results support an electron beam heating model rather than a purely thermal conduction model as the driving mechanism for this flare.
Low-density laboratory spectra near the He ii ?304 lineTräbert, ElmarBeiersdorfer, PeterBrickhouse, Nancy S.Golub, LeonDOI: info:10.1051/0004-6361/201527825v. 586A115
Träbert, Elmar, Beiersdorfer, Peter, Brickhouse, Nancy S., and Golub, Leon. 2016. "Low-density laboratory spectra near the He ii ?304 line." Astronomy and Astrophysics 586:A115.
ID: 139169
Type: article
Authors: Träbert, Elmar; Beiersdorfer, Peter; Brickhouse, Nancy S.; Golub, Leon
Aims: To interpret the EUV spectra of the solar corona, one hopes for laboratory data of specific chemical elements obtained under coronal conditions.
Methods: EUV spectra of He, C, N, O, F, Ne, S, Ar, Fe, and Ni in a 40 Å wide wavelength interval near ?304 were excited in an electron beam ion trap.
Results: We observe some two hundred lines about half of which are not yet identified and included in spectral models.
Conclusions: Our data provide a check on the atomic data bases underlying the spectral models that are used to interpret solar corona data. However, a multitude of mostly weak additional lines taken together represent a flux that is comparable to that of various primary lines. Research supported by the Solar and Heliospherical Physics Program of the National Aeronautics and Space Administration under award NNH10AN31I.
Homologous Helical Jets: Observations By IRIS, SDO, and Hinode and Magnetic Modeling With Data- Driven SimulationsCheung, Mark C. M.De Pontieu, B.Tarbell, T. D.Fu, Y.Tian, H.Testa, P.Reeves, Katharine K.Martínez-Sykora, J.Boerner, P.Wülser, J. P.Lemen, J.Title, A. M.Hurlburt, N.Kleint, L.Kankelborg, C.Jaeggli, S.Golub, L.McKillop, S.Saar, S.Carlsson, M.Hansteen, V.DOI: info:10.1088/0004-637X/801/2/83v. 80183
Cheung, Mark C. M., De Pontieu, B., Tarbell, T. D., Fu, Y., Tian, H., Testa, P., Reeves, Katharine K., Martínez-Sykora, J., Boerner, P., Wülser, J. P., Lemen, J., Title, A. M., Hurlburt, N., Kleint, L., Kankelborg, C., Jaeggli, S., Golub, L., McKillop, S., Saar, S., Carlsson, M., and Hansteen, V. 2015. "Homologous Helical Jets: Observations By IRIS, SDO, and Hinode and Magnetic Modeling With Data- Driven Simulations." The Astrophysical Journal 801:83.
ID: 135643
Type: article
Authors: Cheung, Mark C. M.; De Pontieu, B.; Tarbell, T. D.; Fu, Y.; Tian, H.; Testa, P.; Reeves, Katharine K.; Martínez-Sykora, J.; Boerner, P.; Wülser, J. P.; Lemen, J.; Title, A. M.; Hurlburt, N.; Kleint, L.; Kankelborg, C.; Jaeggli, S.; Golub, L.; McKillop, S.; Saar, S.; Carlsson, M.; Hansteen, V.
Abstract: 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.