Author name code: sheeley ADS astronomy entries on 2022-09-14 author:"Sheeley, Neil R." ------------------------------------------------------------------------ Title: The Sun's Mean Line-of-Sight Field Authors: Sheeley, Neil R., Jr Bibcode: 2022arXiv220803216S Altcode: We regard the Sun-as-a-star magnetic field (i.e. the mean field) as a filter for the spherical harmonic components of the photospheric field, and calculate the transmission coefficients of this filter. The coefficients for each harmonic, $Y_{l}^{m}$, are listed in three tables according to their dependence on $B_{0}$, the observer's latitude in the star's polar coordinate system. These coefficients are used to interpret the 46-yr sequence of daily mean-field measurements at the Wilcox Solar Observatory. We find that the non-axisymmetric part of the field originates in the $Y_{1}^{1}$, $Y_{2}^{2}$, and a combination of the $Y_{3}^{3}$ and $Y_{3}^{1}$ harmonic components. The axisymmetric part of the field originates in $Y_{2}^{0}$ plus a $B_{0}$-dependent combination of the $Y_{1}^{0}$ and $Y_{3}^{0}$ components. The power spectrum of the field has peaks at frequencies corresponding to the ~27-day synodic equatorial rotation period and its second and third harmonics. Each of these peaks has fine structure on its low-frequency side, indicating magnetic patterns that rotate slowly under the influence of differential rotation and meridional flow. The sidebands of the fundamental mode resolve into peaks corresponding to periods of ~28.5 and ~30 days, which tend to occur at the start of sunspot maximum, whereas the ~27-day period tends to occur toward the end of sunspot maximum. We expect similar rotational sidebands to occur in magnetic observations of other Sun-like stars and to be a useful complement to asteroseismology studies of convection and magnetic fields in those stars. Title: Acceleration of Coronal Mass Ejection Plasma in the Low Corona as Measured by the Citizen CATE Experiment Authors: Penn, Matthew J.; Baer, Robert; Walter, Donald; Pierce, Michael; Gelderman, Richard; Ursache, Andrei; Elmore, David; Mitchell, Adrianna; Kovac, Sarah; Hare, Honor; McKay, Myles; Jensen, Logan; Watson, Zachary; Conley, Mike; Powers, Lynn; Lazarova, Marianna; Wright, Joseph; Young, David; Isberner, Fred; Hart, C. Alexandra; Sheeley, N. R., Jr.; Penn, Debbie; Allen-Penn, Kate; Alder, Bruce; Alder, Ryan; Hall-Conley, Geri; Gerdes, David; Weber, Katherine; Johnson, Jeffrey; Matzek, Gerald; Somes, Steven; Sobnosky, Rob; McGowen, Robert; Meo, Michael; Proctor, Damani; Wessinger, Charlie; Schilling, Jeannine; Kerr, Jay; Beltzer-Sweeney, Alexander; Falatoun, Alex; Higgins, David; Boyce, Grady; Hettick, Jared; Blanco, Philip; Dixon, Scott; Ardebilianfard, Sepehr; Boyce, Pat; Lighthill, Richard; Lighthill, Denese; Anderson, David; Anderson, Mine; Schad, Thomas; Smith, Sonna; Jensen, Declan; Allen, Anthony; Smith, Donavan; Brandon, Gage; Earp, Joe; Earp, Jane; Blair, Bob; Claver, Chuck F.; Claver, Jennifer A.; Claver, Ryan H.; Hoops, Danielle; Rivera, Esteban; Gibson, Llanee; Hiner, Martin; Lann, Rein; Miller, Shaedyn; Briggs, Burton; Davis, Karan; Jackson, Brian; Kautzsch, Kaleb; Sandidge, Wesley; Lucas, Russell; Gregg, Duane; Kamenetzky, Julia; Rivera, Tiffany; Shaw, Joe; Scherrer, Bryan; Sandbak, Dylan; McFate, Richard; Harris, Wilson; Brasier, Zachery; McNeil, Stephen; Jensen, Jack; Jensen, Makai; Moore, Mason; Temple, Alexandria; Vanderhorst, Thomas; Kautz, Richard; Bellorado, Orion; Jenkins, LaVor R.; Pantuso, Corey; Carey, Marley; Byrnes, Josh; Scholtens, Kyle; Web, Julian; Baker, Brain; Barngrover, Katie; Hathaway, Drew; Smith, Kallen; Chandler, Kellyn; Hinkle, Lydia; Chandler, Ione; Gisler, Galen; Benner, Jack; Mas, Madison; Rogers, Maya; Moore, Prescott; Pelofske, Elijah; Gulley, Stephen; Short, Beth; Crooker, Isabel; Hammock, Jennifer; Cardenas, Katsina; Cardenas, Kateri; Wellman, Jennifer; Roy, Mark; Meyer, Joe; Brough, Jalynne; Brough, Kameron; Nelson, Tim; Nelson, Zack; Russell, Caleb; Bautz, Theresa; Weitzel, Eric; Team; Wistisen, Michele; Aagard, Shae; Whipps, Zachary; Neuroth, Logan; Poste, Dawson; Worthen, Connor; Gosain, Sanjay; Steward, Mark; Gosain, Vanshita; Gosain, Ruchi; Jorgensen, Janet; Doucette, Eleanor; Doucette, Reba; Iwen, Elliott; Cochran, Alexus; Stith, James; Scribner, Doug; Kenney, Austen; Pisciotti, Kolby; Pease, Irene; Cynamon, Samuel; Cynamon, Charles; Cynamon, Dawn; Tolbert, Bart; Dupree, Jean A.; Weremeichik, Jeremy; Pindell, Nathan; Stives, Kristen; Simacek, Thomas K.; Simacek, Yolanta G.; Simacek, Anne L.; Boeck, Wayne; Boeck, Andreea; Ryan, Austin; Wierzorec, Gabriel; Klebe, Dimitri; Costanza, Bryan; Cerny, Arnie; Schmale, Trevor; Hoffman, Tessa; Streeter, Sam; Erickson, Jack; McClellan, Michele; Erickson, Ella; Brettell, Brynn; Shoffner, Savannah; McClellan, Emilie; VanVoorhis, Julie; Bramhall, Cole; Stelly, Daniel; Bee, Bentley; Acevedo, Bruno; Kroeger, Madison; Trumpenski, Ben; Sump, Nolan; Brook, Liam; Ernzen, Jagert; Lewis, Jessica; Maderak, Ryan; Kennedy, Charles; Dembinski, David; Wright, Rita; Foster, Michael; Ahmadbasir, Mohammad; Laycox, Monty; Foster, James; Orr, Ethan; Staab, Ashley; Speck, Angela; Baldridge, Sean; Kegley, Lucy; Bavlnka, Jordan; Ballew, Thomas; Callen, Bruce; Ojakangas, Gregory; Bremer, Mark; Angliongto, Maryanne; Redecker, Mark; Bremer, Chris; Hill, Peggy; Rodgers, Michael; Duncan, Jordan; Fincher, Sam; Nielsen, Ben; Hasler, Samantha; Shivelbine, Taylor; Howard, Tyler; Midden, Chris; Patrick, Sean; Glenn, Kerry; Mandrell, Chris; Dawson, Kyle; Cortez, Margaret; Levsky, Alyssa; Gallaba, Dinuka; Perrone, Mason; Taylor, Jasmyn; Yanamandra-Fisher, Padma A.; Harper, Howard; Adams, Lindsay; Springer, Michaela; Menard, BillyJoe; Boggs, Dylan; Lynch, Caitlin; Watson, Jacob; York, Andi; Matthews, David; Brown, Kiley; Garrison, Dylan; Mangin, Jonathan; Mangin, Isaac; Birriel, Jennifer; Birriel, Ignacio; Yess, Capp; Anderson, Jesse; Caudill, Ethan; Smith, Allyn; Buckner, Spencer; Longhurst, Russ; Fagan, Ben; Nations, Christian; DiMatties, Jeffrey; Thompson, Patricia; Garrison, David; Garrison, Thomas; Garrison, William; Kidd, Mary; Baker, Maria; Ledford, Mary-Beth; Winebarger, Amy; Freed, Michael; Church, Morgyn; Dickens, Jim; Anderson, Bob; Smith, Ned; Dorsey, Lynne; Justice, Doug; Zavala, Daniel; Stockbridge, Zach; Brittain, Sean; Jensen, Stanley; Leiendecker, Harrison; Thompson, Erin; Deady, Michelle; Quinn-Hughes, Kelly; Slimmer, David; Granger, Valerie; LaRoche, Michael; Hill LaRoche, Serena; Manspeaker, Rachel; Nguyen, Peter; Smith, Daniel; Payne, Jim; Zissett, Jerry; Roberts, Arianna M.; Roberts, Gabrielle W.; Roberts, Harrison; Riddle, Amy; Ursache, Corina; Ursache, Elena Bibcode: 2020PASP..132a4201P Altcode: The citizen Continental-America Telescopic Eclipse (CATE) Experiment was a new type of citizen science experiment designed to capture a time sequence of white-light coronal observations during totality from 17:16 to 18:48 UT on 2017 August 21. Using identical instruments the CATE group imaged the inner corona from 1 to 2.1 RSun with 1.″43 pixels at a cadence of 2.1 s. A slow coronal mass ejection (CME) started on the SW limb of the Sun before the total eclipse began. An analysis of CATE data from 17:22 to 17:39 UT maps the spatial distribution of coronal flow velocities from about 1.2 to 2.1 RSun, and shows the CME material accelerates from about 0 to 200 km s-1 across this part of the corona. This CME is observed by LASCO C2 at 3.1-13 RSun with a constant speed of 254 km s-1. The CATE and LASCO observations are not fit by either constant acceleration nor spatially uniform velocity change, and so the CME acceleration mechanism must produce variable acceleration in this region of the corona. Title: Memorable Events During a Research Career Authors: Sheeley, Neil R. Bibcode: 2019JGRA..124.4949S Altcode: In this paper, I sketch a path through my research career in solar and heliospheric physics, recalling some memorable events and discoveries that occurred along the way. This chain of events begins with an influential Time magazine article in 1955 and progresses through a summer at Bell Labs, 9 years at Caltech, 7 years at the Kitt Peak National Observatory, 43 years at the Naval Research Laboratory, and ends with a digitized map of the Sun's Ca II K-Line emission in 1919 when the AGU was born. Accidents and puzzling results are often the keys to progress and should be examined carefully. Title: Observational Evidence for the Associated Formation of Blobs and Raining Inflows in the Solar Corona Authors: Sanchez-Diaz, Eduardo; Rouillard, Alexis P.; Davies, Jackie A.; Lavraud, Benoit; Sheeley, Neil R.; Pinto, Rui F.; Kilpua, Emilia; Plotnikov, Illya; Genot, Vincent Bibcode: 2017EGUGA..19.4855S Altcode: The origin of the Slow Solar Wind (SSW) is still a topic of much debate. The continual emergence of small transient structures from helmet streamers is thought to constitute an important sources of the SSW. Determining the height at which these transients are released is an important factor in determining the conditions under which the SSW forms. To this end, we have carried out a multipoint analysis of small transient structures released from a north-south tilted helmet streamer into the slow solar wind over a broad range of position angles during Carrington Rotation 2137. During this period of time, the catalogue in Sheeley & Wang (2014) reported a big number of transient structures collapsing back toward the Sun, referred to as "raining inflows". Combining the remote-sensing observations taken by the Solar-TErrestrial RElations Observatory (STEREO) mission with coronagraphic observations from the SOlar and Heliospheric Observatory (SOHO) spacecraft, we show that the release of such small transient structures (often called blobs), which subsequently move away from the Sun, is associated with the concomitant formation of raining inflows. This is the first direct association between outflowing blobs and raining inflows, which locates the formation of blobs above the helmet streamers and gives strong support that the blobs are released by magnetic reconnection. This work was made with the funding from the HELCATS project under the FP7 EU contract number 606692 Title: Tracking the Magnetic Flux in and around Sunspots Authors: Sheeley, N. R., Jr.; Stauffer, J. R.; Thomassie, J. C.; Warren, H. P. Bibcode: 2017ApJ...836..144S Altcode: We have developed a procedure for tracking sunspots observed by the Helioseismic and Magnetic Imager on the Solar Dynamics Observatory and for making curvature-corrected space/time maps of the associated line-of-sight magnetic field and continuum intensity. We apply this procedure to 36 sunspots, each observed continuously for nine days around its central meridian passage time, and find that the proper motions separate into two distinct components depending on their speeds. Fast (∼3-5 km s-1) motions, comparable to Evershed flows, are produced by weak vertical fluctuations of the horizontal canopy field and recur on a timescale of 12-20 min. Slow (∼0.3-0.5 km s-1) motions diverge from a sunspot-centered ring whose location depends on the size of the sunspot, occurring in the mid-penumbra for large sunspots and at the outer edge of the penumbra for small sunspots. The slow ingoing features are contracting spokes of a quasi-vertical field of umbral polarity. These inflows disappear when the sunspot loses its penumbra, and may be related to inward-moving penumbral grain. The slow outgoing features may have either polarity depending on whether they originate from quasi-vertical fields of umbral polarity or from the outer edge of the canopy. When a sunspot decays, the penumbra and canopy disappear, and the moat becomes filled with slow outflows of umbral polarity. We apply our procedure to decaying sunspots, to long-lived sunspots, and to numerical simulations of a long-lived sunspot by Rempel. Title: Observational Evidence for the Associated Formation of Blobs and Raining Inflows in the Solar Corona Authors: Sanchez-Diaz, E.; Rouillard, A. P.; Davies, J. A.; Lavraud, B.; Sheeley, N. R.; Pinto, R. F.; Kilpua, E.; Plotnikov, I.; Genot, V. Bibcode: 2017ApJ...835L...7S Altcode: 2016arXiv161205487S The origin of the slow solar wind is still a topic of much debate. The continual emergence of small transient structures from helmet streamers is thought to constitute one of the main sources of the slow wind. Determining the height at which these transients are released is an important factor in determining the conditions under which the slow solar wind forms. To this end, we have carried out a multipoint analysis of small transient structures released from a north-south tilted helmet streamer into the slow solar wind over a broad range of position angles during Carrington Rotation 2137. Combining the remote-sensing observations taken by the Solar-TErrestrial RElations Observatory (STEREO) mission with coronagraphic observations from the SOlar and Heliospheric Observatory (SOHO) spacecraft, we show that the release of such small transient structures (often called blobs), which subsequently move away from the Sun, is associated with the concomitant formation of transient structures collapsing back toward the Sun; the latter have been referred to by previous authors as “raining inflows.” This is the first direct association between outflowing blobs and raining inflows, which locates the formation of blobs above the helmet streamers and gives strong support that the blobs are released by magnetic reconnection. Title: The Stereo Electron Spikes and the Interplanetary Magnetic Field Authors: Jokipii, J. R.; Sheeley, N. R., Jr.; Wang, Y. M.; Giacalone, J. Bibcode: 2016AGUFMSH51G..06J Altcode: A recent paper (Klassen etal, 2015) discussed observations of a spike event of 55-65 keV electrons which occurred very nearly simultaneously at STEREO A and STEREO B, which at the time were separated in longitude by 38 degrees. The authors associated the spikes with a flare at the Sun near the footpoint of the nominal Archimedean spiral magnetic field line passing through STEREO A. The spike at STEREO A was delayed by 2.2 minutes from that at STEREOB. We discuss the observations in terms of a model in which the electrons, accelerated at the flare, propagate without significant scattering along magnetic field lines which separate or diverge as a function of radial distance from the Sun. The near simultaneity of the spikes at the two spacecraft is a natural consequence of this model. We interpret the divergence of the magnetic field lines as a consequence of field-line random walk and flux-tube expansion. We show that the field-line random walk in the absence of flux-tube expansion produces an rms spread of field lines significantly less than that which is required to produce to observed divergence. We find that observations of the solar wind and its source region at the time of the event can account for the observations in terms of propagation along interplanetary magnetic field-lines. Klassen, A., Dresing, N., Gomez-Herrero, R, and Heber, B., A&A 580, A115 (2015) Financial support for NS and YMW was provided by NASA and CNR. Title: Can collisions regulate the He++ abundance of the slow solar wind? Authors: Sanchez Diaz, Eduardo; Blelly, A. P. Rouillard. L.; Pinto, R.; Lavraud, B.; Segura, K.; Tao, C.; Sheeley, N. R.; Plotnikov, I. Bibcode: 2016shin.confE..80S Altcode: At solar maximum, the slow solar wind presents an enhanced alpha abundance compared to solar minimum (Aellig et al., 2001; Kasper et al., 2007, 2012). Sanchez-Diaz et al. (2016) found that the yearly averages of alpha abundance in the slow solar wind is very well correlated with the yearly averages of the proton mass flux right above the transition region. This correlation is especially remarkable for the very slow solar wind (V<300 km/s), where this proton flux is very high and variable (5 times bigger than at solar minimum and one order of magnitude bigger than in the fast solar wind). We hypothesized that the alpha abundance might be enhanced due to a non-negligible amount of Coulomb collisions between protons and alphas due to this high proton flux. To explore the role of H+ ? He++ collisions in the acceleration of He++ ions, we input the proton temperature and expansion factor profiles resulting from the combination of a Potential Field Source Model (PFSS) and a 1D hydrodynamic solar wind model described in Pinto et al. (2009) into a collisional two fluid hydrostatic model. The model assumes that there is no heating for the He++ ions in the very slow solar wind. We evaluate the possible role of Coulomb collisions on the escape of He++ for different geometries and boundary conditions. We find that there is a region right above the transition region where the collisions have the effect of transferring momentum from the protons to the alphas. This is the region where the hydrogen may be accelerated by collisions with hydrogen. In the upper Corona it is the alphas that would transfer momentum to the protons and the collisions have the effect of slowing the alphas down.

This study was carried out as part of the HELCATS FP7 project Title: Multipoint observation of coronal inflows Authors: Sanchez Diaz, Eduardo; Rouillard, A.; Davies, J.; Lavraud, B.; Plotnikov, I.; Sheeley, N. R.; Pinto, R. Bibcode: 2016shin.confE.112S Altcode: Corotating Interaction Regions (CIRs) are filled with numerous small-scale transients. Outward moving blobs have been commonly observed in LASCO and SECCHI (Plotnikov et al. 2016; Rouillard et al., 2008, 2009, 2010; Sheeley et al., 1997). Inward moving blobs, or inflows, have been observed in LASCO C2 over the last two solar cycles (Wang et al., 1999a,b; Sheeley et al., 2001,2002,2007,2014). On rare occasions, inflows and outflows are observed together and in apparent association. Outward moving blobs and inflows are thought to be the products of the same process: magnetic reconnection at around 4-5 solar radii producing an inflow-outflow pair. However, only one isolated signature (either inflow or outflow) is reported in most observations. The second signature is thought to usually lie outside the field-of-view (FOV) of the instruments, or below their sensitivity limit.

Here we show observations of the same CIR by combining the SECCHI and LASCO instrument onboard STEREO and SOHO. The FOV of SECCHI-COR2 allows us to see the outflow part associated to the inflows. This outflow can be followed all the way out in the Heliosphere with SECHHI-HI1 and HI2. During May and June 2013, the magnetic field topology of the corona, with a nearly vertical neutral line, and the lack of CMEs was optimal to observe blobs and inflows at all latitudes. We present a 3D reconstruction of all the small-scale transients, both inflows and outflows, entrained by this CIR. This includes the first observation of inflows with COR2 and the first multipoint observation of the inflows entrained by the same CIR from two satellites. We evaluate the presumed connection between coronal inflows, in-out pairs and blobs and discuss the origin of blobs and their likely association to a continuous magnetic reconnection process in the Solar Corona.

This study was carried out as part of the HELCATS FP7 project Title: The very slow solar wind: Properties, origin and variability Authors: Sanchez-Diaz, Eduardo; Rouillard, Alexis P.; Lavraud, Benoit; Segura, Kevin; Tao, Chihiro; Pinto, Rui; Sheeley, N. R.; Plotnikov, Illya Bibcode: 2016JGRA..121.2830S Altcode: Solar wind slower than 300 km/s, hereafter termed very slow solar wind (VSSW), is seldom observed at 1 AU. It was, however, commonly measured inside 0.7 AU by the two Helios spacecraft, particularly during solar maximum. Magnetohydrodynamic (MHD) modeling reveals that the disappearance of VSSW at 1 AU is the result of its interaction with faster solar wind. The acceleration and compression of the VSSW contributes to the observed highly variable structure of the slow solar wind at 1 AU. The VSSW usually contains the heliospheric plasma sheet and current sheet. It has higher density and lower temperature than the regular slow solar wind, extending the known scaling laws below 300 km/s. Its helium abundance increases with solar activity even more significantly than the slow solar wind. Contrary to faster solar winds, the helium ions in the VSSW are slower than the dominant protons. Combining a Potential Field Source Surface (PFSS) model with ballistic back tracing, we study the source region of the VSSW. We show that the proton density flux for the VSSW is much higher than for the faster winds, particularly at solar maximum. Title: Geographically Distributed Citizen Scientist Training for the 2017 Citizen CATE Experiment Authors: Gelderman, Richard; Penn, Matt; Baer, Robert; Isberner, Fred; Pierce, Michael; Walter, Donald K.; Yanamandra-Fisher, Padma; Sheeley, Neil R. Bibcode: 2016AAS...22734902G Altcode: The solar eclipse of 21 August 2017 will be visible to over a half billion people across the entire North American continent. The roughly 100-mile wide path of totality, stretching from Oregon to South Carolina, will be the destination for tens of millions of people. In the decades since 1979, when the last total solar eclipse was visible from the continental USA, the phenomenon of Internet enabled citizen science has grown to be an accepted mode for science. The Citizen Continental-America Telescopic Eclipse (Citizen CATE) experiment has been funded as one of the three 2017 eclipse related NASA STEM agreements to engage citizen scientists in a unique, cutting-edge solar physics experiment. Teams across the USA will be trained to use standardized refracting telescope and digital imager set-ups to observe the solar corona during the eclipse, acquiring multiple exposures to create one high dynamic range image. After observing during the eclipse, the CATE volunteers will upload the combined image to a cloud-storage site and the CATE team will then work to properly orient and align all the images collected from across the continent to produce a continuous 90-minutes movie. A time-compressed first cut of the entire sequence will be made available to media outlets on the same afternoon of the eclipse, with hope that high quality images will encourage the most accurate coverage of this Great American Eclipse. We discuss overall the project, as well as details of the initial tests of the prototype set-up (including in the Faroe Islands during the March 2015 total solar eclipse) and plans for the future night-time and day-time observing campaigns, and for a handful of observing teams positioned for overlapping observations of the March 2016 total solar eclipse in the South Pacific. Title: Coronal Mass Ejections and the Solar Cycle Variation of the Sun's Open Flux Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2015ApJ...809L..24W Altcode: 2021arXiv210407238W The strength of the radial component of the interplanetary magnetic field (IMF), which is a measure of the Sun’s total open flux, is observed to vary by roughly a factor of two over the 11 year solar cycle. Several recent studies have proposed that the Sun’s open flux consists of a constant or “floor” component that dominates at sunspot minimum, and a time-varying component due to coronal mass ejections (CMEs). Here, we point out that CMEs cannot account for the large peaks in the IMF strength which occurred in 2003 and late 2014, and which coincided with peaks in the Sun’s equatorial dipole moment. We also show that near-Earth interplanetary CMEs, as identified in the catalog of Richardson and Cane, contribute at most ∼30% of the average radial IMF strength even during sunspot maximum. We conclude that the long-term variation of the radial IMF strength is determined mainly by the Sun’s total dipole moment, with the quadrupole moment and CMEs providing an additional boost near sunspot maximum. Most of the open flux is rooted in coronal holes, whose solar cycle evolution in turn reflects that of the Sun’s lowest-order multipoles. Title: The Recent Rejuvenation of the Sun's Large-scale Magnetic Field: A Clue for Understanding Past and Future Sunspot Cycles Authors: Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 2015ApJ...809..113S Altcode: The quiet nature of sunspot cycle 24 was disrupted during the second half of 2014 when the Sun’s large-scale field underwent a sudden rejuvenation: the solar mean field reached its highest value since 1991, the interplanetary field strength doubled, and galactic cosmic rays showed their strongest 27-day modulation since neutron-monitor observations began in 1957; in the outer corona, the large increase of field strength was reflected by unprecedentedly large numbers of coronal loops collapsing inward along the heliospheric current sheet. Here, we show that this rejuvenation was not caused by a significant increase in the level of solar activity as measured by the smoothed sunspot number and CME rate, but instead was caused by the systematic emergence of flux in active regions whose longitudinal distribution greatly increased the Sun’s dipole moment. A similar post-maximum increase in the dipole moment occurred during each of the previous three sunspot cycles, and marked the start of the declining phase of each cycle. We note that the north-south component of this peak dipole moment provides an early indicator of the amplitude of the next cycle, and conclude that the amplitude of cycle 25 may be comparable to that of cycle 24, and well above the amplitudes obtained during the Maunder Minimum. Title: Using Running Difference Images to Track Proper Motions of XUV Coronal Intensity on the Sun Authors: Sheeley, N. R., Jr.; Warren, H. P.; Lee, J.; Chung, S.; Katz, J.; Namkung, M. Bibcode: 2014ApJ...797..131S Altcode: We have developed a procedure for observing and tracking proper motions of faint XUV coronal intensity on the Sun and have applied this procedure to study the collective motions of cellular plumes and the shorter-period waves in sunspots. Our space/time maps of cellular plumes show a series of tracks with the same 5-8 minute repetition times and ~100 km s-1 sky-plane speeds found previously in active-region fans and in coronal hole plumes. By synchronizing movies and space/time maps, we find that the tracks are produced by elongated ejections from the unipolar flux concentrations at the bases of the cellular plumes and that the phases of these ejections are uncorrelated from cell to cell. Thus, the large-scale motion is not a continuous flow, but is more like a system of independent conveyor belts all moving in the same direction along the magnetic field. In contrast, the proper motions in sunspots are clearly waves resulting from periodic disturbances in the sunspot umbras. The periods are ~2.6 minutes, but the sky-plane speeds and wavelengths depend on the heights of the waves above the sunspot. In the chromosphere, the waves decelerate from 35-45 km s-1 in the umbra to 7-8 km s-1 toward the outer edge of the penumbra, but in the corona, the waves accelerate to ~60-100 km s-1. Because chromospheric and coronal tracks originate from the same space/time locations, the coronal waves must emerge from the same umbral flashes that produce the chromospheric waves. Title: Coronal Inflows during the Interval 1996-2014 Authors: Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 2014ApJ...797...10S Altcode: We extend our previous counts of coronal inflows from the 5 yr interval 1996-2001 to the 18 yr interval 1996-2014. By comparing stackplots of these counts with similar stackplots of the source-surface magnetic field and its longitudinal gradient, we find that the inflows occur in long-lived streams with counting rates in excess of 18 inflows per day at sector boundaries where the gradient exceeds 0.22 G rad-1. These streams are responsible for the high (86%) correlation between the inflow rate and the longitudinal field gradient. The overall inflow rate was several times larger in sunspot cycle 23 than it has been so far in cycle 24, reflecting the relatively weak source-surface fields during this cycle. By comparison, in cycles 21-22, the source-surface field and its gradient had bursts of great strength, as if large numbers of inflows occurred during those cycles. We find no obvious relation between inflows and coronal mass ejections (CMEs) on timescales of days to weeks, regardless of the speeds of the CMEs, and only a 60% correlation on timescales of months, provided the CMEs are fast (V > 600 km s-1). We conclude that most of the flux carried out by CMEs is returned to the Sun via field line reconnection well below the 2.0 R ⊙ inner limit of the LASCO field of view, and that the remainder accumulates in the outer corona for an eventual return at sector boundaries. Title: Origin of the Wang-Sheeley-Arge Solar Wind Model Authors: Sheeley, Neil R. Bibcode: 2014AAS...22420302S Altcode: A correlation between solar wind speed at Earth and the amount of field line expansion in the corona was verified in 1989 using 22 years of solar and interplanetary observations. This talk will trace the history of this discovery from its birth 15 years earlier in the Skylab era to its current use as a space weather forecasting technique. This research was supported by NASA and ONR. Title: Memories Authors: Sheeley, N. R., Jr. Bibcode: 2013ASPC..478...85S Altcode: This paper highlights some events in solar research, beginning at Caltech in 1959 when Leighton described a technique for obtaining high-resolution observations of solar magnetic fields, and extending to 1971 when his ideas were being pursued with the new spectroheliograph and 82 cm solar image at the Kitt Peak National Observatory. Title: Using Coronal Cells to Infer the Magnetic Field Structure and Chirality of Filament Channels Authors: Sheeley, N. R., Jr.; Martin, S. F.; Panasenco, O.; Warren, H. P. Bibcode: 2013ApJ...772...88S Altcode: 2013arXiv1306.2273S Coronal cells are visible at temperatures of ~1.2 MK in Fe XII coronal images obtained from the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory spacecraft. We show that near a filament channel, the plumelike tails of these cells bend horizontally in opposite directions on the two sides of the channel like fibrils in the chromosphere. Because the cells are rooted in magnetic flux concentrations of majority polarity, these observations can be used with photospheric magnetograms to infer the direction of the horizontal field in filament channels and the chirality of the associated magnetic field. This method is similar to the procedure for inferring the direction of the magnetic field and the chirality of the fibril pattern in filament channels from Hα observations. However, the coronal cell observations are easier to use and provide clear inferences of the horizontal field direction for heights up to ~50 Mm into the corona. Title: Fe XII Stalks and the Origin of the Axial Field in Filament Channels Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Stenborg, G. Bibcode: 2013ApJ...770...72W Altcode: Employing Fe XII images and line-of-sight magnetograms, we deduce the direction of the axial field in high-latitude filament channels from the orientation of the adjacent stalklike structures. Throughout the rising phase of the current solar cycle 24, filament channels poleward of latitude 30° overwhelmingly obeyed the hemispheric chirality rule, being dextral (sinistral) in the northern (southern) hemisphere, corresponding to negative (positive) helicity. During the deep minimum of 2007-2009, the orientation of the Fe XII stalks was often difficult to determine, but no obvious violations of the rule were found. Although the hemispheric trend was still present during the maximum and early declining phase of cycle 23 (2000-2003), several high-latitude exceptions were identified at that time. From the observation that dextral (sinistral) filament channels form through the decay of active regions whose Fe XII features show a counterclockwise (clockwise) whorl, we conclude that the axial field direction is determined by the intrinsic helicity of the active regions. In contrast, generation of the axial field component by the photospheric differential rotation is difficult to reconcile with the observed chirality of polar crown and circular filament channels, and with the presence of filament channels along the equator. The main role of differential rotation in filament channel formation is to expedite the cancellation of flux and thus the removal of the transverse field component. We propose further that, rather than being ejected into the heliosphere, the axial field is eventually resubmerged by flux cancellation as the adjacent unipolar regions become increasingly mixed. Title: The Solar Wind and Interplanetary Field during Very Low Amplitude Sunspot Cycles Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2013ApJ...764...90W Altcode: Cosmogenic isotope records indicate that a solar-cycle modulation persists through extended periods of very low sunspot activity. One immediate implication is that the photospheric field during such grand minima did not consist entirely of ephemeral regions, which produce a negligible amount of open magnetic flux, but continued to have a large-scale component originating from active regions. Present-day solar and heliospheric observations show that the solar wind mass flux and proton density at the coronal base scale almost linearly with the footpoint field strength, whereas the wind speed at Earth is uncorrelated with the latter. Thus a factor of ~4-7 reduction in the total open flux, as deduced from reconstructions of the interplanetary magnetic field (IMF) during the Maunder Minimum, would lead to a similar decrease in the solar wind densities, while leaving the wind speeds largely unchanged. We also demonstrate that a decrease in the strengths of the largest active regions during grand minima will reduce the amplitude of the Sun's equatorial dipole relative to the axial component, causing the IMF strength to peak near sunspot minimum rather than near sunspot maximum, a result that is consistent with the phase shift observed in the 10Be record during the Maunder Minimum. Finally, we discuss the origin of the 5 yr periodicity sometimes present in the cosmogenic isotope data during low and medium amplitude cycles. Title: Calibrating 100 Years of Polar Faculae Measurements: Implications for the Evolution of the Heliospheric Magnetic Field Authors: Muñoz-Jaramillo, Andrés; Sheeley, Neil R.; Zhang, Jie; DeLuca, Edward E. Bibcode: 2012ApJ...753..146M Altcode: 2013arXiv1303.0345M Although the Sun's polar magnetic fields are thought to provide important clues for understanding the 11 year sunspot cycle, including the observed variations of its amplitude and period, the current database of high-quality polar field measurements spans relatively few sunspot cycles. In this paper, we address this deficiency by consolidating Mount Wilson Observatory polar faculae data from four data reduction campaigns, validating it through a comparison with facular data counted automatically from Michelson Doppler Imager (MDI) intensitygrams, and calibrating it against polar field measurements taken by the Wilcox Solar Observatory and average polar field and total polar flux calculated using MDI line-of-sight magnetograms. Our results show that the consolidated polar facular measurements are in excellent agreement with both polar field and polar flux estimates, making them an ideal proxy to study the evolution of the polar magnetic field. Additionally, we combine this database with sunspot area measurements to study the role of the polar magnetic flux in the evolution of the heliospheric magnetic field (HMF). We find that there is a strong correlation between HMF and polar flux at solar minimum and that, taken together, polar flux and sunspot area are better at explaining the evolution of the HMF during the last century than sunspot area alone. Title: The Longitudinal Properties of a Solar Energetic Particle Event Investigated Using Modern Solar Imaging Authors: Rouillard, A. P.; Sheeley, N. R.; Tylka, A.; Vourlidas, A.; Ng, C. K.; Rakowski, C.; Cohen, C. M. S.; Mewaldt, R. A.; Mason, G. M.; Reames, D.; Savani, N. P.; StCyr, O. C.; Szabo, A. Bibcode: 2012ApJ...752...44R Altcode: We use combined high-cadence, high-resolution, and multi-point imaging by the Solar-Terrestrial Relations Observatory (STEREO) and the Solar and Heliospheric Observatory to investigate the hour-long eruption of a fast and wide coronal mass ejection (CME) on 2011 March 21 when the twin STEREO spacecraft were located beyond the solar limbs. We analyze the relation between the eruption of the CME, the evolution of an Extreme Ultraviolet (EUV) wave, and the onset of a solar energetic particle (SEP) event measured in situ by the STEREO and near-Earth orbiting spacecraft. Combined ultraviolet and white-light images of the lower corona reveal that in an initial CME lateral "expansion phase," the EUV disturbance tracks the laterally expanding flanks of the CME, both moving parallel to the solar surface with speeds of ~450 km s-1. When the lateral expansion of the ejecta ceases, the EUV disturbance carries on propagating parallel to the solar surface but devolves rapidly into a less coherent structure. Multi-point tracking of the CME leading edge and the effects of the launched compression waves (e.g., pushed streamers) give anti-sunward speeds that initially exceed 900 km s-1 at all measured position angles. We combine our analysis of ultraviolet and white-light images with a comprehensive study of the velocity dispersion of energetic particles measured in situ by particle detectors located at STEREO-A (STA) and first Lagrange point (L1), to demonstrate that the delayed solar particle release times at STA and L1 are consistent with the time required (30-40 minutes) for the CME to perturb the corona over a wide range of longitudes. This study finds an association between the longitudinal extent of the perturbed corona (in EUV and white light) and the longitudinal extent of the SEP event in the heliosphere. Title: Calibration Of a Century of Polar Field Measurements and what this Tells us About the Long-term Variability of the Solar and Heliospheric Magnetic Field Authors: Munoz-Jaramillo, Andres; Sheeley, N. R.; Zhang, J.; DeLuca, E. E. Bibcode: 2012AAS...22012304M Altcode: In addition to the well known 11-year periodicity, the solar cycle also presents long-term modulations of its amplitude and period which play a determinant role in the evolution of space weather and climate. To this date, the efforts at understanding long-term solar variability have focused on the active parts of the cycle using sunspot properties as their main source of data. However, the recent extend minimum of sunspot cycle 23 has shown us that the quiet parts of the cycle are equally important and thus long-term databases complementary to sunspot properties are necessary.

Here we show how to consolidate Mount Wilson Observatory polar faculae data from four observational campaigns (1906-1964, Sheeley 1966; 1960-1975, Sheeley 1976; 1975-1990, Sheeley 1991; 1985-2007, Sheeley 2008), validate it through a comparison with facular data counted automatically from MDI intensitygrams, and calibrate it against polar field measurements taken by the Wilcox Solar Observatory (1977-2011) and average polar field and total polar flux calculated using MDI line-of-sight magnetograms (1996-2011).

We also show that the consolidated polar facular measurements are in excellent agreement with both polar field and polar flux estimates, making them an ideal proxy to study the evolution of the polar magnetic field since 1906 and use this proxy to study the role of polar flux in the evolution of the solar cycle and the Heliospheric Magnetic Field (HMF). Title: Coronal Cells Authors: Sheeley, N. R., Jr.; Warren, H. P. Bibcode: 2012ApJ...749...40S Altcode: We have recently noticed cellular features in Fe XII 193 Å images of the 1.2 MK corona. They occur in regions bounded by a coronal hole and a filament channel, and are centered on flux elements of the photospheric magnetic network. Like their neighboring coronal holes, these regions have minority-polarity flux that is ~0.1-0.3 times their flux of majority polarity. Consequently, the minority-polarity flux is "grabbed" by the majority-polarity flux to form low-lying loops, and the remainder of the network flux escapes to connect with its opposite-polarity counterpart in distant active regions of the Sun. As these regions are carried toward the limb by solar rotation, the cells disappear and are replaced by linear plumes projecting toward the limb. In simultaneous views from the Solar Terrestrial Relations Observatory and Solar Dynamics Observatory spacecraft, these plumes project in opposite directions, extending away from the coronal hole in one view and toward the hole in the other view, suggesting that they are sky-plane projections of the same radial structures. We conclude that these regions are composed of closely spaced radial plumes, extending upward like candles on a birthday cake and visible as cells when seen from above. We suppose that a coronal hole has this same discrete, cellular magnetic structure, but that it is not seen until the encroachment of opposite-polarity flux closes part or all of the hole. Title: On the Nature of the Solar Wind from Coronal Pseudostreamers Authors: Wang, Y. -M.; Grappin, R.; Robbrecht, E.; Sheeley, N. R., Jr. Bibcode: 2012ApJ...749..182W Altcode: Coronal pseudostreamers, which separate like-polarity coronal holes, do not have current sheet extensions, unlike the familiar helmet streamers that separate opposite-polarity holes. Both types of streamers taper into narrow plasma sheets that are maintained by continual interchange reconnection with the adjacent open magnetic field lines. White-light observations show that pseudostreamers do not emit plasma blobs; this important difference from helmet streamers is due to the convergence of like-polarity field lines above the X-point, which prevents the underlying loops from expanding outward and pinching off. The main component of the pseudostreamer wind has the form of steady outflow along the open field lines rooted just inside the boundaries of the adjacent coronal holes. These flux tubes are characterized by very rapid expansion below the X-point, followed by reconvergence at greater heights. Analysis of an idealized pseudostreamer configuration shows that, as the separation between the underlying holes increases, the X-point rises and the expansion factor f ss at the source surface increases. In situ observations of pseudostreamer crossings indicate wind speeds v ranging from ~350 to ~550 km s-1, with O7 +/O6 + ratios that are enhanced compared with those in high-speed streams but substantially lower than in the slow solar wind. Hydrodynamic energy-balance models show that the empirical v-f ss relation overestimates the wind speeds from nonmonotonically expanding flux tubes, particularly when the X-point is located at low heights and f ss is small. We conclude that pseudostreamers produce a "hybrid" type of outflow that is intermediate between classical slow and fast solar wind. Title: Observations of Reconnecting Flare Loops with the Atmospheric Imaging Assembly Authors: Warren, Harry P.; O'Brien, Casey M.; Sheeley, Neil R., Jr. Bibcode: 2011ApJ...742...92W Altcode: 2011arXiv1109.2474W Perhaps the most compelling evidence for the role of magnetic reconnection in solar flares comes from the supra-arcade downflows that have been observed above many post-flare loop arcades. These downflows are thought to be related to highly non-potential field lines that have reconnected and are propagating away from the current sheet. We present new observations of supra-arcade downflows taken with the Atmospheric Imaging Assembly (AIA) on the Solar Dynamics Observatory (SDO). The morphology and dynamics of the downflows observed with AIA provide new evidence for the role of magnetic reconnection in solar flares. With these new observations we are able to measure downflows originating at larger heights than in previous studies. We find, however, that the initial velocities measured here (~144 km s-1) are well below the Alfvén speed expected in the lower corona, and consistent with previous results. We also find no evidence that the downflows brighten with time, as would be expected from chromospheric evaporation. These observations suggest that simple two-dimensional models cannot explain the detailed observations of solar flares. Title: The longitudinal properties of solar energetic particle events investigated using modern solar imaging. Authors: Rouillard, A. P.; Sheeley, N. R.; Tylka, A. J.; Vourlidas, A.; Ng, C. K.; Mason, G. M.; Cohen, C. M. Bibcode: 2011AGUFMSH33D..03R Altcode: On 2011 March 21, the Solar-Terrestrial Relations Observatory (STEREO) imaged the launch (at ~02:10UT) and outward propagation of a fast (>1300 km s-1) and wide (latitudinal extent greater than 90 degrees) coronal mass ejection (CME) which emerged W135 degrees (behind the west-limb as viewed from near-Earth spacecraft). Protons with energies exceeding 90 MeV were first detected by the STEREO-Ahead (STA) spacecraft and a few minutes later by near-Earth orbiting spacecraft. Velocity dispersion analyses of energetic electrons, protons and heavier ions, put the solar particle release (SPR) times along magnetic field lines connected to STA at ~02:30UT and along magnetic field lines connected to near-Earth spacecraft at ~ 03:00UT. The spatial evolution of a pressure wave and its associated shock forming around the CME could be tracked using (critical) high-cadence and high-resolution STA (extreme ultraviolet and white-light) images. We demonstrate that the delay between the SEP onset at STA and Earth is consistent with the time required for the pressure wave to propagate from the launch-site of the CME to the base of coronal streamers that are magnetically connected to near-Earth spacecraft. By considering measured shock speeds and inferred shock geometries along different longitudes and by deriving spectra of energetic protons, this study also presents some interpretation of the longitudinal variability of the SEP event in terms of the evolution of the compression wave. Time permitting, we will also summarise the results of similar analyses carried out for the other energetic CME events in 2010 and 2011. Title: Observations of the White Light Corona from Solar Orbiter and Solar Probe Plus Authors: Howard, R. A.; Thernisien, A. F.; Vourlidas, A.; Plunkett, S. P.; Korendyke, C. M.; Sheeley, N. R.; Morrill, J. S.; Socker, D. G.; Linton, M. G.; Liewer, P. C.; De Jong, E. M.; Velli, M. M.; Mikic, Z.; Bothmer, V.; Lamy, P. L. Bibcode: 2011AGUFMSH43F..06H Altcode: The SoloHI instrument on Solar Orbiter and the WISPR instrument on Solar Probe+ will make white light coronagraphic images of the corona as the two spacecraft orbit the Sun. The minimum perihelia for Solar Orbiter is about 60 Rsun and for SP+ is 9.5 Rsun. The wide field of view of the WISPR instrument (about 105 degrees radially) corresponds to viewing the corona from 2.2 Rsun to 20 Rsun. Thus the entire Thomson hemisphere is contained within the telescope's field and we need to think of the instrument as being a traditional remote sensing instrument and then transitioning to a local in-situ instrument. The local behavior derives from the fact that the maximum Thomson scattering will favor the electron plasma close to the spacecraft - exactly what the in-situ instruments will be sampling. SoloHI and WISPR will also observe scattered light from dust in the inner heliosphere, which will be an entirely new spatial regime for dust observations from a coronagraph, which we assume to arise from dust in the general neighborhood of about half way between the observer and the Sun. As the dust grains approach the Sun, they evaporate and do not contribute to the scattering. A dust free zone has been postulated to exist somewhere inside of 5 Rsun where all dust is evaporated, but this has never been observed. The radial position where the evaporation occurs will depend on the precise molecular composition of the individual grains. The orbital plane of Solar Orbiter will gradually increase up to about 35 degrees, enabling a very different view through the zodiacal dust cloud to test the models generated from in-ecliptic observations. In this paper we will explore some of the issues associated with the observation of the dust and will present a simple model to explore the sensitivity of the instrument to observe such evaporations. Title: Interpreting the Properties of Solar Energetic Particle Events by Using Combined Imaging and Modeling of Interplanetary Shocks Authors: Rouillard, A. P.; Odstřcil, D.; Sheeley, N. R.; Tylka, A.; Vourlidas, A.; Mason, G.; Wu, C. -C.; Savani, N. P.; Wood, B. E.; Ng, C. K.; Stenborg, G.; Szabo, A.; St. Cyr, O. C. Bibcode: 2011ApJ...735....7R Altcode: Images of the solar corona obtained by the Solar-Terrestrial Relations Observatory (STEREO) provide high-cadence, high-resolution observations of a compression wave forming ahead of a fast (940 km s-1) coronal mass ejection (CME) that erupted at ~9:00 UT on 2010 April 03. The passage of this wave at 1 AU is detected in situ by the Advanced Composition Explorer and Wind spacecraft at 08:00 UT on April 05 as a shock followed by a turbulent and heated sheath. These unprecedented and complementary observations of a shock-sheath region from the Sun to 1 AU are used to investigate the onset of a Solar Energetic Particle (SEP) event measured at the first Lagrange point (L1) and at STEREO-Behind (STB). The spatial extent, radial coordinates, and speed of the ejection are measured from STEREO observations and used as inputs to a numerical simulation of the CME propagation in the background solar wind. The simulated magnetic and plasma properties of the shock and sheath region at L1 agree very well with the in situ measurements. These simulation results reveal that L1 and STB are magnetically connected to the western and eastern edges of the driven shock, respectively. They also show that the 12 hr delay between the eruption time of the ejection and the SEP onset at L1 corresponds to the time required for the bow shock to reach the magnetic field lines connected with L1. The simulated shock compression ratio increases along these magnetic field lines until the maximum flux of high-energy particles is observed. Title: The Solar Origin of Small Interplanetary Transients Authors: Rouillard, A. P.; Sheeley, N. R., Jr.; Cooper, T. J.; Davies, J. A.; Lavraud, B.; Kilpua, E. K. J.; Skoug, R. M.; Steinberg, J. T.; Szabo, A.; Opitz, A.; Sauvaud, J. -A. Bibcode: 2011ApJ...734....7R Altcode: In this paper, we present evidence for magnetic transients with small radial extents ranging from 0.025 to 0.118 AU measured in situ by the Solar-Terrestrial Relations Observatory (STEREO) and the near-Earth Advanced Composition Explorer (ACE) and Wind spacecraft. The transients considered in this study are much smaller (<0.12 AU) than the typical sizes of magnetic clouds measured near 1 AU (~0.23 AU). They are marked by low plasma beta values, generally lower magnetic field variance, short timescale magnetic field rotations, and are all entrained by high-speed streams by the time they reach 1 AU. We use this entrainment to trace the origin of these small interplanetary transients in coronagraph images. We demonstrate that these magnetic field structures originate as either small or large mass ejecta. The small mass ejecta often appear from the tip of helmet streamers as arch-like structures and other poorly defined white-light features (the so-called blobs). However, we have found a case of a small magnetic transient tracing back to a small and narrow mass ejection erupting from below helmet streamers. Surprisingly, one of the small magnetic structures traces back to a large mass ejection; in this case, we show that the central axis of the coronal mass ejection is along a different latitude and longitude to that of the in situ spacecraft. The small size of the transient is related to the in situ measurements being taken on the edges or periphery of a larger magnetic structure. In the last part of the paper, an ejection with an arch-like aspect is tracked continuously to 1 AU in the STEREO images. The associated in situ signature is not that of a magnetic field rotation but rather of a temporary reversal of the magnetic field direction. Due to its "open-field topology," we speculate that this structure is partly formed near helmet streamers due to reconnection between closed and open magnetic field lines. The implications of these observations for our understanding of the variability of the slow solar wind are discussed. Title: Carrington Maps of Ca II K-line Emission for the Years 1915-1985 Authors: Sheeley, N. R., Jr.; Cooper, T. J.; Anderson, J. R. L. Bibcode: 2011ApJ...730...51S Altcode: We have used Mount Wilson Observatory calcium K-line images, digitized and flat fielded by the solar group at UCLA, to construct Carrington maps of Ca II 3934 Å intensity for the years 1915-1985. These maps have a spatial resolution comparable to the resolution of Carrington maps of the magnetic field observed at Kitt Peak and a spectral resolution comparable to the width of the K232 emission. Consequently, they provide a way of tracking the spatial distribution of magnetic flux from the present back to the year 1915. In this paper, we compare some of the recent K-line maps with corresponding maps of magnetic field, and show examples of K-line maps during earlier sunspot cycles when high-quality magnetograms were not available. Then, we use butterfly diagrams and super-synoptic displays to summarize the long-term evolution of the patterns of calcium intensity. Although each cycle has characteristics that are similar to the others, cycle 19 is remarkable for its broad latitudinal distribution of active regions, for its giant poleward surges of flux, and for the emergence of a north-south asymmetry that lasted 10 years. Title: The Wide Field Imager for Solar PRobe (WISPR) Authors: Plunkett, S. P.; Howard, R. A.; Vourlidas, A.; Korendyke, C. M.; Socker, D. G.; Morrill, J. S.; Sheeley, N. R.; Linton, M.; Liewer, P. C.; de Jong, E. M.; Mikic, Z. Bibcode: 2010AGUFMSH11B1622P Altcode: The Wide Field Imager for Solar PRobe (WISPR) will image the Thomson-scattered light from the coronal plasma in the inner corona, with unprecedented spatial resolution, cadence, and sensitivity. WISPR follows on the SECCHI Heliospheric Imager (HI) aboard the STEREO mission, and addresses all four key objectives in the Solar Probe Plus: Report of the STDT (2008): (1) Determine the structure and dynamics of the magnetic fields at the sources of the fast and slow solar wind, (2) Trace the flow of energy that heats the solar corona and accelerates the SW, (3) explore the mechanisms that accelerate and transport energetic particles, (4) explore dusty plasma phenomena and their influence on the solar wind and energetic particle formation. Situated in the ram direction of the Solar Probe Plus (SPP) spacecraft (S/C), WISPR will have the unique ability to image the coronal structures when they are close to the Sun, as they approach, and as they pass over the spacecraft. As a remote sensor, WISPR will connect the structures close to the Sun to the spacecraft and provide important spatial and temporal information; measuring, for example, the properties of the structures generating the shocks and SEPs that will be measured in a few minutes at the S/C. Since the S/C is embedded in the corona, WISPR and the in situ instruments will measure for the first time the same plasma. Also as the SPP transits through the corona, the rapidly-varying viewpoint and high spatial resolution of WISPR will enable tomographic imaging of the corona, and lead to higher fidelity and finer scale 3D reconstructions than are possible with the STEREO mission or single-view rotational tomography. The wide field of view will include at times other inner heliospheric probes (e.g. Solar Orbiter) and will image the outflowing wind that is impinging on that probe. In addition to this standard imaging mode, WISPR opens a new capability for imaging instruments, the measurement of pressure turbulence by employing a high cadence mode (~1 sec) to image a small region in the corona. For the first time, the slopes of the power spectral density from images can be compared directly to the density and magnetic field fluctuations seen in situ as a function of coronal spatial structure and heliocentric distance. In addition, the 1 sec cadence can be generated anywhere within the WISPR field, enabling the study of the transition of the solar wind injected at the tops of the helmet streamers to inertial dissipation scales. Title: White Light and In Situ Comparison of a Forming Merged Interaction Region Authors: Rouillard, A. P.; Lavraud, B.; Sheeley, N. R.; Davies, J. A.; Burlaga, L. F.; Savani, N. P.; Jacquey, C.; Forsyth, R. J. Bibcode: 2010ApJ...719.1385R Altcode: The images taken by the Heliospheric Imager (HI) instruments, part of the SECCHI imaging package on board the pair of STEREO spacecraft, provide information on the radial and latitudinal evolution of the plasma transported by coronal mass ejections (CMEs). In this case study, a CME, appearing near 15 UT on 2007 November 15 in SECCHI coronagraph images, leads to the formation of two out-flowing density structures (DSs) in the heliosphere. The analysis of time-elongation maps constructed from images obtained by the HI instruments shows that these DSs were propagating along the Sun-Earth line. A direct comparison of HI images and in situ measurements taken near Earth could therefore be performed. These two DSs are separated by a cavity associated with little brightness variation or equivalently little electron density variation. In situ measurements made in the solar wind near Earth on 2007 November 20 show that this cavity corresponds to a magnetic cloud (MC). While the leading DS is related to the sheath in front of the MC, the second DS is located on the sunward side of the MC where high-speed solar wind from a coronal hole catches up and interacts with the MC. We conclude that HI observes the sub-structures of a merged interaction region (MIR), a region of the interplanetary medium where the total solar wind pressure is greatly enhanced by the interaction of an MC with the ambient solar wind. This MIR caused the largest geomagnetic storm in 2007. Title: Observations of the magnetic field and plasma in the heliosheath by Voyager 2 from 2007.7 to 2009.4 Authors: Burlaga, L. F.; Ness, N. F.; Wang, Y. -M.; Sheeley, N. R.; Richardson, J. D. Bibcode: 2010JGRA..115.8107B Altcode: 2010JGRA..11508107B The density and temperature profiles of the plasma measured by Voyager 2 (V2) behind the termination shock changed abruptly near 2008.6 from relatively large average values and large fluctuations during 2007.7 to 2008.6 (interval A) to relatively low average values and very small-amplitude fluctuations during 2008.6 to 2009.4 (interval B). This paper shows that the change in the magnetic field strength B(t) was less abrupt than the plasma changes, and the fluctuations of the magnetic field strength in interval B were of moderate amplitude, with indications of a quasiperiodic structure in part of the interval. The magnetic field was directed away from the sun (positive polarity) ∼ 78% ± 5% of the time in both interval A and interval B, changing in an irregular way from positive to negative polarities throughout the interval. The polarity distribution indicates that the minimum latitudinal extent of the heliospheric current sheet (HCS) was near V2 throughout the interval, consistent with the extrapolated minimum latitudes of the HCS computed from solar magnetic field observations. Thus, V2 was observing magnetic fields from the southern polar coronal hole most of the time. The distribution of B was lognormal in interval A and Gaussian interval B. Title: On the "Extended" Solar Cycle in Coronal Emission Authors: Robbrecht, E.; Wang, Y. -M.; Sheeley, N. R., Jr.; Rich, N. B. Bibcode: 2010ApJ...716..693R Altcode: Butterfly diagrams (latitude-time plots) of coronal emission show a zone of enhanced brightness that appears near the poles just after solar maximum and migrates toward lower latitudes; a bifurcation seems to occur at sunspot minimum, with one branch continuing to migrate equatorward with the sunspots of the new cycle and the other branch heading back to the poles. The resulting patterns have been likened to those seen in torsional oscillations and have been taken as evidence for an extended solar cycle lasting over ~17 yr. In order to clarify the nature of the overlapping bands of coronal emission, we construct butterfly diagrams from green-line simulations covering the period 1967-2009 and from 19.5 nm and 30.4 nm observations taken with the Extreme-Ultraviolet Imaging Telescope during 1996-2009. As anticipated from earlier studies, we find that the high-latitude enhancements mark the footpoint areas of closed loops with one end rooted outside the evolving boundaries of the polar coronal holes. The strong underlying fields were built up over the declining phase of the cycle through the poleward transport of active-region flux by the surface meridional flow. Rather than being a precursor of the new-cycle sunspot activity zone, the high-latitude emission forms a physically distinct, U-shaped band that curves upward again as active-region fields emerge at midlatitudes and reconnect with the receding polar-hole boundaries. We conclude that the so-called extended cycle in coronal emission is a manifestation not of early new-cycle activity, but of the poleward concentration of old-cycle trailing-polarity flux by meridional flow. Title: What's So Peculiar about the Cycle 23/24 Solar Minimum? Authors: Sheeley, N. R., Jr. Bibcode: 2010ASPC..428....3S Altcode: 2010arXiv1005.3834S Traditionally, solar physicists become anxious around solar minimum, as they await the high-latitude sunspot groups of the new cycle. Now, we are in an extended sunspot minimum with conditions not seen in recent memory, and interest in the sunspot cycle has increased again. In this paper, I will describe some of the characteristics of the current solar minimum, including its great depth, its extended duration, its weak polar magnetic fields, and its small amount of open flux. Flux transport simulations suggest that these characteristics are a consequence of temporal variations of the Sun's large-scale meridional circulation. Title: Tracking Streamer Blobs into the Heliosphere Authors: Sheeley, N. R., Jr.; Rouillard, A. P. Bibcode: 2010ApJ...715..300S Altcode: 2010arXiv1006.5379S In this paper, we use coronal and heliospheric images from the Solar Terrestrial Relations Observatory (STEREO) spacecraft to track streamer blobs into the heliosphere and to observe them being swept up and compressed by the fast wind from low-latitude coronal holes. From an analysis of their elongation/time tracks, we discover a "locus of enhanced visibility" where neighboring blobs pass each other along the line of sight and their corotating spiral is seen edge-on. The detailed shape of this locus accounts for a variety of east-west asymmetries and allows us to recognize the spiral of blobs by its signatures in the STEREO images: in the eastern view from STEREO-A, the leading edge of the spiral is visible as a moving wavefront where foreground ejections overtake background ejections against the sky and then fade. In the western view from STEREO-B, the leading edge is only visible close to the Sun-spacecraft line where the radial path of ejections nearly coincides with the line of sight. In this case, we can track large-scale waves continuously back to the lower corona and see that they originate as face-on blobs. Title: Formation and Evolution of Coronal Holes Following the Emergence of Active Regions Authors: Wang, Y. -M.; Robbrecht, E.; Rouillard, A. P.; Sheeley, N. R., Jr.; Thernisien, A. F. R. Bibcode: 2010ApJ...715...39W Altcode: The low level of solar activity over the past four years has provided unusually favorable conditions for tracking the formation and evolution of individual coronal holes and their wind streams. Employing extreme-ultraviolet images recorded with the Solar Terrestrial Relations Observatory during 2007-2009, we analyze three cases in which small coronal holes first appear at the edges of newly emerged active regions and then expand via flux transport processes, eventually becoming attached to the polar holes. The holes form gradually over timescales comparable to or greater than that for the active regions to emerge, without any obvious association with coronal mass ejections. The evolving hole areas coincide approximately with the footpoints of open field lines derived from potential-field source-surface extrapolations of the photospheric field. One of these coronal-hole systems, centered at the equator and maintained by a succession of old-cycle active regions emerging in the same longitude range, persists in one form or another for up to two years. The other two holes, located at midlatitudes and originating from new-cycle active regions, become strongly sheared and decay away after a few rotations. The hole boundaries and the small active-region holes, both of which are sources of slow wind, are observed to undergo continual short-term (lsim1 day) fluctuations on spatial scales comparable to that of the supergranulation. From in situ measurements, we identify a number of plasma sheets associated with pseudostreamers separating holes of the same polarity. Title: Intermittent release of transients in the slow solar wind: 1. Remote sensing observations Authors: Rouillard, A. P.; Davies, J. A.; Lavraud, B.; Forsyth, R. J.; Savani, N. P.; Bewsher, D.; Brown, D. S.; Sheeley, N. R.; Davis, C. J.; Harrison, R. A.; Howard, R. A.; Vourlidas, A.; Lockwood, M.; Crothers, S. R.; Eyles, C. J. Bibcode: 2010JGRA..115.4103R Altcode: 2010JGRA..11504103R The Heliospheric Imager (HI) instruments on board the STEREO spacecraft are used to analyze the solar wind during August and September 2007. We show how HI can be used to image the streamer belt and, in particular, the variability of the slow solar wind which originates inside and in the vicinity of the streamer belt. Intermittent mass flows are observed in HI difference images, streaming out along the extension of helmet streamers. These flows can appear very differently in images: plasma distributed on twisted flux ropes, V-shaped structures, or “blobs.” The variety of these transient features may highlight the richness of phenomena that could occur near helmet streamers: emergence of flux ropes, reconnection of magnetic field lines at the tip of helmet streamers, or disconnection of open magnetic field lines. The plasma released with these transient events forms part of the solar wind in the higher corona; HI observations show that these transients are frequently entrained by corotating interaction regions (CIRs), leading to the formation of larger, brighter plasma structures in HI images. This entrainment is used to estimate the trajectory of these plasma ejecta. In doing so, we demonstrate that successive transients can be entrained by the same CIR in the high corona if they emanate from the same corotating source. Some parts of the streamers are more effective sources of transients than others. Surprisingly, evidence is given for the outflow of a recurring twisted magnetic structure, suggesting that the emergence of flux ropes can be recurrent. Title: On the Weakening of the Polar Magnetic Fields during Solar Cycle 23 Authors: Wang, Y. -M.; Robbrecht, E.; Sheeley, N. R., Jr. Bibcode: 2009ApJ...707.1372W Altcode: The Sun's polar fields are currently ~40% weaker than they were during the previous three sunspot minima. This weakening has been accompanied by a corresponding decrease in the interplanetary magnetic field (IMF) strength, by a ~20% shrinkage in the polar coronal-hole areas, and by a reduction in the solar-wind mass flux over the poles. It has also been reflected in coronal streamer structure and the heliospheric current sheet, which only showed the expected flattening into the equatorial plane after sunspot numbers fell to unusually low values in mid-2008. From latitude-time plots of the photospheric field, it has long been apparent that the polar fields are formed through the transport of trailing-polarity flux from the sunspot latitudes to the poles. To address the question of why the polar fields are now so weak, we simulate the evolution of the photospheric field and radial IMF strength from 1965 to the present, employing a surface transport model that includes the effects of active region emergence, differential rotation, supergranular convection, and a poleward bulk flow. We find that the observed evolution can be reproduced if the amplitude of the surface meridional flow is varied by as little as 15% (between 14.5 and 17 m s-1), with the higher average speeds being required during the long cycles 20 and 23. Title: A solar storm observed from the Sun to Venus using the STEREO, Venus Express, and MESSENGER spacecraft Authors: Rouillard, A. P.; Davies, J. A.; Forsyth, R. J.; Savani, N. P.; Sheeley, N. R.; Thernisien, A.; Zhang, T. -L.; Howard, R. A.; Anderson, B.; Carr, C. M.; Tsang, S.; Lockwood, M.; Davis, C. J.; Harrison, R. A.; Bewsher, D.; Fränz, M.; Crothers, S. R.; Eyles, C. J.; Brown, D. S.; Whittaker, I.; Hapgood, M.; Coates, A. J.; Jones, G. H.; Grande, M.; Frahm, R. A.; Winningham, J. D. Bibcode: 2009JGRA..114.7106R Altcode: 2009JGRA..11407106R The suite of SECCHI optical imaging instruments on the STEREO-A spacecraft is used to track a solar storm, consisting of several coronal mass ejections (CMEs) and other coronal loops, as it propagates from the Sun into the heliosphere during May 2007. The 3-D propagation path of the largest interplanetary CME (ICME) is determined from the observations made by the SECCHI Heliospheric Imager (HI) on STEREO-A (HI-1/2A). Two parts of the CME are tracked through the SECCHI images, a bright loop and a V-shaped feature located at the rear of the event. We show that these two structures could be the result of line-of-sight integration of the light scattered by electrons located on a single flux rope. In addition to being imaged by HI, the CME is observed simultaneously by the plasma and magnetic field experiments on the Venus Express and MESSENGER spacecraft. The imaged loop and V-shaped structure bound, as expected, the flux rope observed in situ. The SECCHI images reveal that the leading loop-like structure propagated faster than the V-shaped structure, and a decrease in in situ CME speed occurred during the passage of the flux rope. We interpret this as the result of the continuous radial expansion of the flux rope as it progressed outward through the interplanetary medium. An expansion speed in the radial direction of ∼30 km s-1 is obtained directly from the SECCHI-HI images and is in agreement with the difference in speed of the two structures observed in situ. This paper shows that the flux rope location can be determined from white light images, which could have important space weather applications. Title: Radial and solar cycle variations of the magnetic fields in the heliosheath: Voyager 1 observations from 2005 to 2008 Authors: Burlaga, L. F.; Ness, N. F.; Acuña, M. H.; Wang, Y. -M.; Sheeley, N. R. Bibcode: 2009JGRA..114.6106B Altcode: 2009JGRA..11406106B We discuss the magnetic field strength B(t) and polarity observed by Voyager 1 (V1) in the heliosheath at the heliographic latitude ≈34° as it moved away from the Sun from 2005 through 2008.82 (where 2008.0 is the beginning of 1 January 2008). The pattern of the polarity of the magnetic field changed from alternating positive and negative polarities to predominantly negative polarities (magnetic fields pointing along the Archimedean spiral field angle toward the Sun) at ≈2006.23). This transition indicates that the latitudinal extent of the heliospheric current sheet (HCS) was decreasing in the supersonic solar wind, as expected for the declining phase of the solar cycle, and as predicted by extrapolation of the magnetic neutral line near the photosphere to the position of V1. However, the polarity was not uniformly negative in during 2008, in contrast to the predicted polarity. This difference suggests that the maximum latitudinal extent of the HCS was tending to increase in the northern hemisphere in the heliosheath, while it was decreasing in the supersonic solar wind. The large-scale magnetic field strength B(t) was observed by V1 from 2005 through 2008.82. During this interval of decreasing solar activity toward solar minimum, B(t) at 1 AU was decreasing, and the solar wind speed V at the latitude of V1 was increasing. Adjusting the temporal profile of B(t) observed by V1 for the solar cycle variations of B and V in the supersonic solar wind, we find that the radial gradient of B(R) in heliosheath from the radial distance R = 94.2 AU to 107.9 AU between 2005.0 and 2008.82 was 0.0017 nT/AU ≤ grad B ≤ 0.0055 nT/AU, or grad B = (0.0036 ± 0.0019) nT/AU. Title: Remote-sensing Observations of the Corona and Solar Wind Authors: Sheeley, Neil R., Jr. Bibcode: 2009AAS...21410701S Altcode: On June 25, 1908, George Ellery Hale used the 60-foot Tower Telescope on Mount Wilson to make the first measurements of magnetic fields in sunspots. This began a series of studies that led to Hale's Law of sunspot polarities and established the Mount Wilson Observatory as a leading center of solar magnetic field research. The magnetic aura was still present in 1962 when I began solar research there as a Caltech graduate student. Mount Wilson astronomer Horace Babcock and his father had invented the solar magnetograph, discovered the polar fields of the Sun, and observed their reversal near the 1958 sunspot maximum. Caltech physicist Robert Leighton had added new instrumentation to the Mount Wilson spectroheliograph and obtained high-resolution maps of the magnetic field. Babcock had just published his classic paper on the topology of the field and its 22-year cycle. The paper contained a sketch, illustrating the coronal field-line reconnection, which he thought must occur in response to changes of the photospheric field. Some loops flew away in the yet-to-be-discovered solar wind and other loops collapsed back to the Sun.

In this talk, I will present new observations from the SOHO and STEREO spacecraft, which show such coronal changes. Loops stretch out in the expanding corona and tear away from the Sun like drops from a leaky faucet. Simultaneous observations with different perspectives show that the detached loops are really helices in 3-D. Off-pointed heliospheric imagers allow us to track these ejections outward past planets (including Earth) and comets, and to observe their compression into a heliospheric spiral, as a consequence of longitudinal speed gradients on the rotating Sun. And XUV observations of the solar disk show brightness changes associated with reconnections high in the corona, like auroral displays in the magnetosphere. Title: A Multispacecraft Analysis of a Small-Scale Transient Entrained by Solar Wind Streams Authors: Rouillard, A. P.; Savani, N. P.; Davies, J. A.; Lavraud, B.; Forsyth, R. J.; Morley, S. K.; Opitz, A.; Sheeley, N. R.; Burlaga, L. F.; Sauvaud, J. -A.; Simunac, K. D. C.; Luhmann, J. G.; Galvin, A. B.; Crothers, S. R.; Davis, C. J.; Harrison, R. A.; Lockwood, M.; Eyles, C. J.; Bewsher, D.; Brown, D. S. Bibcode: 2009SoPh..256..307R Altcode: The images taken by the Heliospheric Imagers (HIs), part of the SECCHI imaging package onboard the pair of STEREO spacecraft, provide information on the radial and latitudinal evolution of the plasma compressed inside corotating interaction regions (CIRs). A plasma density wave imaged by the HI instrument onboard STEREO-B was found to propagate towards STEREO-A, enabling a comparison between simultaneous remote-sensing and in situ observations of its structure to be performed. In situ measurements made by STEREO-A show that the plasma density wave is associated with the passage of a CIR. The magnetic field compressed after the CIR stream interface (SI) is found to have a planar distribution. Minimum variance analysis of the magnetic field vectors shows that the SI is inclined at 54° to the orbital plane of the STEREO-A spacecraft. This inclination of the CIR SI is comparable to the inclination of the associated plasma density wave observed by HI. A small-scale magnetic cloud with a flux rope topology and radial extent of 0.08 AU is also embedded prior to the SI. The pitch-angle distribution of suprathermal electrons measured by the STEREO-A SWEA instrument shows that an open magnetic field topology in the cloud replaced the heliospheric current sheet locally. These observations confirm that HI observes CIRs in difference images when a small-scale transient is caught up in the compression region. Title: Two Years of the STEREO Heliospheric Imagers. Invited Review Authors: Harrison, Richard A.; Davies, Jackie A.; Rouillard, Alexis P.; Davis, Christopher J.; Eyles, Christopher J.; Bewsher, Danielle; Crothers, Steve R.; Howard, Russell A.; Sheeley, Neil R.; Vourlidas, Angelos; Webb, David F.; Brown, Daniel S.; Dorrian, Gareth D. Bibcode: 2009SoPh..256..219H Altcode: Imaging of the heliosphere is a burgeoning area of research. As a result, it is awash with new results, using novel applications, and is demonstrating great potential for future research in a wide range of topical areas. The STEREO (Solar TErrestrial RElations Observatory) Heliospheric Imager (HI) instruments are at the heart of this new development, building on the pioneering observations of the SMEI (Solar Mass Ejection Imager) instrument aboard the Coriolis spacecraft. Other earlier heliospheric imaging systems have included ground-based interplanetary scintillation (IPS) facilities and the photometers on the Helios spacecraft. With the HI instruments, we now have routine wide-angle imaging of the inner heliosphere, from vantage points outside the Sun-Earth line. HI has been used to investigate the development of coronal mass ejections (CMEs) as they pass through the heliosphere to 1 AU and beyond. Synoptic mapping has also allowed us to see graphic illustrations of the nature of mass outflow as a function of distance from the Sun - in particular, stressing the complexity of the near-Sun solar wind. The instruments have also been used to image co-rotating interaction regions (CIRs), to study the interaction of comets with the solar wind and CMEs, and to witness the impact of CMEs and CIRs on planets. The very nature of this area of research - which brings together aspects of solar physics, space-environment physics, and solar-terrestrial physics - means that the research papers are spread among a wide range of journals from different disciplines. Thus, in this special issue, it is timely and appropriate to provide a review of the results of the first two years of the HI investigations. Title: Remote-sensing Observations of the Corona and Solar Wind Authors: Sheeley, Neil R., Jr. Bibcode: 2009SPD....40.2801S Altcode: On June 25, 1908, George Ellery Hale used the 60-foot Tower Telescope on Mount Wilson to make the first measurements of magnetic fields in sunspots. This began a series of studies that led to Hale's Law of sunspot polarities and established the Mount Wilson Observatory as a leading center of solar magnetic field research. The magnetic aura was still present in 1962 when I began solar research there as a Caltech graduate student. Mount Wilson astronomer Horace Babcock and his father had invented the solar magnetograph, discovered the polar fields of the Sun, and observed their reversal near the 1958 sunspot maximum. Caltech physicist Robert Leighton had added new instrumentation to the Mount Wilson spectroheliograph and obtained high-resolution maps of the magnetic field. Babcock had just published his classic paper on the topology of the field and its 22-year cycle. The paper contained a sketch, illustrating the coronal field-line reconnection, which he thought must occur in response to changes of the photospheric field. Some loops flew away in the yet-to-be-discovered solar wind and other loops collapsed back to the Sun.

In this talk, I will present new observations from the SOHO and STEREO spacecraft, which show such coronal changes. Loops stretch out in the expanding corona and tear away from the Sun like drops from a leaky faucet. Simultaneous observations with different perspectives show that the detached loops are really helices in 3-D. Off-pointed heliospheric imagers allow us to track these ejections outward past planets (including Earth) and comets, and to observe their compression into a heliospheric spiral, as a consequence of longitudinal speed gradients on the rotating Sun. And XUV observations of the solar disk show brightness changes associated with reconnections high in the corona, like auroral displays in the magnetosphere. Title: White-light and in-situ observations of an Earth-impacting CME using the STEREO spacecraft Authors: Rouillard, A. P.; Savani, N. P.; Sheeley, N. R.; Burlaga, L. F.; Lavraud, B.; Davies, J. A.; Forsyth, R. J.; Davis, C.; Lockwood, M. Bibcode: 2009EGUGA..11.8052R Altcode: We use the heliospheric imagers (HIs) onboard the STEREO A and B spacecraft to analyse the propagation of an Earth-impacting Coronal Mass Ejection (CME) during November 2007. The transient is observed continuously in white-light images from the Sun to 1 AU. The 3-D propagation path is determined and a method is outlined to obtain the acceleration profile of the transient. The CME comprises two large density increases in white-light images. Comparison of white-light and in-situ observations shows that the flux-rope is embedded inside these two density increases. The evolution of the CME brightness in white-light images is discussed in terms of the kinematic evolution of the transient and its interaction with the ambient solar wind. Title: The Structure of Streamer Blobs Authors: Sheeley, N. R., Jr.; Lee, D. D. -H.; Casto, K. P.; Wang, Y. -M.; Rich, N. B. Bibcode: 2009ApJ...694.1471S Altcode: We have used Sun-Earth Connection Coronal and Heliospheric Investigation observations obtained from the STEREO A and B spacecraft to study complementary face-on and edge-on views of coronal streamers. The face-on views are analogous to what one might see looking down on a flat equatorial streamer belt at sunspot minimum, and show streamer blobs as diffuse arches gradually expanding outward from the Sun. With the passage of time, the legs of the arches fade, and the ejections appear as a series of azimuthal structures like ripples on a pond. The arched topology is similar to that obtained in face-on views of streamer disconnection events (including in/out pairs and streamer blowout mass ejections), and suggests that streamer blobs have the helical structure of magnetic flux ropes. Title: Understanding the Geomagnetic Precursor of the Solar Cycle Authors: Wang, Y. -M.; Sheeley, N. R. Bibcode: 2009ApJ...694L..11W Altcode: Geomagnetic activity late in the sunspot cycle has been used successfully to forecast the amplitude of the following cycle. This success is somewhat surprising, however, because the recurrent high-speed wind streams that trigger the activity are not proxies of the Sun's polar fields, whose strength is a critical factor in many solar dynamo models. Instead, recurrent geomagnetic activity signals increases in the Sun's equatorial dipole moment, which decays on the ~1-2 yr timescale of the surface meridional flow and does not survive into the next cycle. In accordance with the original empirical method of Ohl, we therefore argue that solar cycle predictions should be based on the minimum level of geomagnetic activity, which is determined by the Sun's axial dipole strength, not on the peak activity during the declining phase of the cycle. On physical grounds, we suggest that an even better indicator would be the total open flux (or strength of the radial interplanetary field component) at sunspot minimum, which in turn can be derived from the historical aa index by removing the contribution of the solar wind speed. This predictor yields a peak yearly sunspot number R max = 97 ± 25 for solar cycle 24. Title: A synoptic view of solar transient evolution in the inner heliosphere using the Heliospheric Imagers on STEREO Authors: Davies, J. A.; Harrison, R. A.; Rouillard, A. P.; Sheeley, N. R.; Perry, C. H.; Bewsher, D.; Davis, C. J.; Eyles, C. J.; Crothers, S. R.; Brown, D. S. Bibcode: 2009GeoRL..36.2102D Altcode: By exploiting data from the STEREO/heliospheric imagers (HI) we extend a well-established technique developed for coronal analysis by producing time-elongation plots that reveal the nature of solar transient activity over a far more extensive region of the heliosphere than previously possible from coronagraph images. Despite the simplicity of these plots, their power in demonstrating how the plethora of ascending coronal features observed near the Sun evolve as they move antisunward is obvious. The time-elongation profile of a transient tracked by HI can, moreover, be used to establish its angle out of the plane-of-the-sky an illustration of such analysis reveals coronal mass ejection material that can be clearly observed propagating out to distances beyond 1AU. This work confirms the value of the time-elongation format in identifying/characterising transient activity in the inner heliosphere, whilst also validating the ability of HI to continuously monitor solar ejecta out to and beyond 1AU. Title: Remote Sensing of the Slow Solar Wind Authors: Sheeley, N. R. Bibcode: 2008AGUFMSH43B..05S Altcode: We are using SECCHI (Sun Earth Connection Coronal and Heliospheric Imager) observations from the STEREO (Solar Terrestrial Relations Observatory) spacecraft to construct elongation/time maps of material moving outward from about 2 solar radii to distances beyond the orbit of Earth. These maps span all position angles within the low-latitude fields of the Heliospheric Imagers and provide synoptic coverage of the motions observed since April 2007. These motions include the gradual acceleration of streamer blobs to solar wind speeds in the range 300-400 km/s. They also include streamer detachments and eruptions, in which the inflating streamers stretch until they separate into collapsing loops and outgoing arches that reach terminal speeds in the range 300-500 km/s. During 2008, the two STEREO spacecraft have separated by 68 degrees, and are now providing complementary views of these ejecta. Recent observations show that some of the streamer blobs and ejections have the helical topology expected for magnetic flux ropes produced by field line reconnection in the corona and solar wind. Title: On the Solar Origins of Open Magnetic Fields in the Heliosphere Authors: Rust, David M.; Haggerty, Dennis K.; Georgoulis, Manolis K.; Sheeley, Neil R.; Wang, Yi-Ming; DeRosa, Marc L.; Schrijver, Carolus J. Bibcode: 2008ApJ...687..635R Altcode: A combination of heliospheric and solar data was used to identify open magnetic fields stretching from the lower corona to Earth orbit. 35 near-relativistic electron beams detected at the ACE spacecraft "labeled" the heliospheric segments of the open fields. An X-ray flare occurred <20 minutes before injection of the electrons in 25 events. These flares labeled the solar segment of the open fields. The flares occurred in western-hemisphere active regions (ARs) with coronal holes whose polarity agreed with the polarity of the beam-carrying interplanetary fields in 23 of the 25 events. We conclude that electron beams reach 1 AU from open AR fields adjacent to flare sites. The Wang & Sheeley implementation of the potential-field source-surface model successfully identified the open fields in 36% of cases. Success meant that the open fields reached the source surface within 3 heliographic deg of the interplanetary magnetic field connected to ACE at 1 AU. Inclusion of five near misses improves the success rate to 56%. The success rate for the Schrijver & DeRosa PFSS implementation was 50%. Our results suggest that, even if the input magnetic data are updated frequently, the PFSS models succeed in only ~50% of cases to identify the coronal segment of open fields. Development of other techniques is in its infancy. Title: A Century of Polar Faculae Variations Authors: Sheeley, N. R., Jr. Bibcode: 2008ApJ...680.1553S Altcode: The numbers of faculae at the poles of the Sun have been estimated from white-light images obtained at the Mount Wilson Observatory during 1985-2006 and combined with prior estimates extending back to 1906, when the observations began. The combined data show an 11 yr cyclic variation with faculae maxima occurring during sunspot minima in each of the past 10 sunspot cycles. Also, these numbers of polar faculae are well correlated with the line-of-sight component of the polar magnetic field measured at the Wilcox Solar Observatory since 1976. The numbers of polar faculae show a secular decrease since 1986, suggesting that the polar fields are now weaker than they have been during any cycle in the past century. Title: A Century of Polar Faculae Variations Authors: Sheeley, N. R. Bibcode: 2008AGUSMSP23A..04S Altcode: The numbers of faculae at the poles of the Sun have been estimated from white-light images obtained at the Mount Wilson Observatory during 1985-2006 and combined with prior estimates extending back to 1906 when the observations began. The combined data show an 11-yr cyclic variation with faculae maxima occurring during sunspot minima in each of the past 10 sunspot cycles. Also, these numbers of polar faculae are well correlated with the line-of-sight component of the polar magnetic field measured at the Wilcox Solar Observatory since 1976. The numbers of polar faculae show a secular decrease since 1986, suggesting that the polar fields are now weaker than they have been during any cycle in the past century. Title: Heliospheric Images of the Solar Wind at Earth Authors: Sheeley, N. R., Jr.; Herbst, A. D.; Palatchi, C. A.; Wang, Y. -M.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.; Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Burlaga, L. F.; Davila, J. M.; Thompson, W. T.; St. Cyr, O. C.; Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Halain, J. P.; Wang, D.; Rich, N. B.; Battams, K.; Esfandiari, E.; Stenborg, G. Bibcode: 2008ApJ...675..853S Altcode: During relatively quiet solar conditions throughout the spring and summer of 2007, the SECCHI HI2 white-light telescope on the STEREO B solar-orbiting spacecraft observed a succession of wave fronts sweeping past Earth. We have compared these heliospheric images with in situ plasma and magnetic field measurements obtained by near-Earth spacecraft, and we have found a near perfect association between the occurrence of these waves and the arrival of density enhancements at the leading edges of high-speed solar wind streams. Virtually all of the strong corotating interaction regions are accompanied by large-scale waves, and the low-density regions between them lack such waves. Because the Sun was dominated by long-lived coronal holes and recurrent solar wind streams during this interval, there is little doubt that we have been observing the compression regions that are formed at low latitude as solar rotation causes the high-speed wind from coronal holes to run into lower speed wind ahead of it. Title: SECCHI Observations of the Sun's Garden-Hose Density Spiral Authors: Sheeley, N. R., Jr.; Herbst, A. D.; Palatchi, C. A.; Wang, Y. -M.; Howard, R. A.; Moses, J. D.; Vourlidas, A.; Newmark, J. S.; Socker, D. G.; Plunkett, S. P.; Korendyke, C. M.; Burlaga, L. F.; Davila, J. M.; Thompson, W. T.; St. Cyr, O. C.; Harrison, R. A.; Davis, C. J.; Eyles, C. J.; Halain, J. P.; Wang, D.; Rich, N. B.; Battams, K.; Esfandiari, E.; Stenborg, G. Bibcode: 2008ApJ...674L.109S Altcode: The SECCHI HI2 white-light imagers on the STEREO A and B spacecraft show systematically different proper motions of material moving outward from the Sun in front of high-speed solar wind streams from coronal holes. As a group of ejections enters the eastern (A) field of view, the elements at the rear of the group appear to overrun the elements at the front. (This is a projection effect and does not mean that the different elements actually merge.) The opposite is true in the western (B) field; the elements at the front of the group appear to run away from the elements at the rear. Elongation/time maps show this effect as a characteristic grouping of the tracks of motion into convergent patterns in the east and divergent patterns in the west, consistent with ejections from a single longitude on the rotating Sun. Evidently, we are observing segments of the "garden-hose" spiral made visible when fast wind from a low-latitude coronal hole compresses blobs of streamer material being shed at the leading edge of the hole. Title: Global structure and dynamics of large-scale fluctuations in the solar wind: Voyager 2 observations during 2005 and 2006 Authors: Burlaga, L. F.; Ness, N. F.; Acũna, M. H.; Wang, Y. -M.; Sheeley, N. R.; Wang, C.; Richardson, J. D. Bibcode: 2008JGRA..113.2104B Altcode: The Voyager 2 (V2) observations of daily averages of the solar wind during 2005 and 2006 from 75.3 AU to 81.6 AU between ~25.7°S and 27.1°S show both a step-like trend in the speed V(t) and ``large-scale fluctuations'' of the magnetic field strength B, speed V, density N and temperature T. The distribution functions of B, N, and NV2 observed by V2 are lognormal and that of V is approximately Gaussian. We introduce a method for specifying the boundary conditions at all latitudes (except near the poles) on a Sun-centered surface of radius of 1 AU, based on solar magnetic field observations. This paper uses only the boundary conditions at the latitude of V2 and a 1-D time-dependent MHD model to calculate the radial evolution of the large-scale fluctuations of B(t), V(t) and N(t) at distances between 1 and 90 AU. This model explains the V2 observations of a lognormal distribution of B and the Gaussian distribution of V, but not the observed lognormal distributions of N and NV2. The lognormal distribution of B observed by V2 was produced primarily by dynamical processes beyond 1 AU. Title: Limits to the Radiative Asymmetry of the Quiet Solar Disk Authors: Livingston, W.; Sheeley, N. R., Jr. Bibcode: 2008ApJ...672.1228L Altcode: Precise data on the uniformity of photospheric radiation over the solar disk seems not to exist. Such information is necessary to separate the radiative behavior of the quiet basal atmosphere from the active (magnetic) atmosphere. Is the latter the sole source of known irradiance variation? How uniform can a solar-like stellar disk be? To obtain this information we have made monochromatic scans along the central meridian of the quiet Sun using single element detectors which do not require flat fielding. The scans were in continua and in selected Fraunhofer lines ranging from 3134 to 46880 Å the observational epoch was near solar minimum: 2006 October to 2007 February. The meridian was chosen to avoid rotational Doppler shifts. We extract the asymmetry between the north and south hemispheres and present it as our main product. In the near-infrared and visible continuum, averaging over granulation and avoiding sunspots, we found that such asymmetry was as low as 0.05% (at 34168 Å on 2007 February 8). In the violet and ultraviolet this asymmetry typically increases to 1%. Asymmetry is larger in the cores of the medium strong photospheric and chromospheric lines, which refer to higher levels in the atmosphere, and may reach 15%. The contrast of faculae increases in the blue (and with improved spatial resolution or seeing), and is the probable source for the measured asymmetries. We also find that line core scans are in general flatter than continuum scans. Title: A Streamer Ejection with Reconnection Close to the Sun Authors: Sheeley, N. R., Jr.; Warren, H. P.; Wang, Y. -M. Bibcode: 2007ApJ...671..926S Altcode: We previously described coronal events that expand gradually outward over an interval of 1-2 days and then suddenly tear apart in the coronagraph's 2-6 Rsolar field of view to form an outgoing flux rope and an inward system of collapsing loops. Now, we combine LASCO white-light images of the outer corona with spectrally resolved EIT images of the inner corona to describe a similar event for which the separation occurs closer to the Sun. The evolution of this 2006 July 1-2 event had four phases: (1) an expansion phase in which magnetic loops rise slowly upward and increase the amount of open flux in the adjacent polar coronal hole and in the low-latitude hole of opposite polarity; (2) a stretching phase in which the legs of the rising loops pinch together to form a current sheet; (3) a transition phase in which field line reconnection produces an outgoing flux rope and a hot cusp of new loops; and (4) an end phase in which the reconnected loops become visible at lower temperatures, and the outgoing flux rope plows through the slow material ahead of it to form a traveling bow wave. During this time, the photospheric field was relatively weak and unchanging, as if the eruption had a nonmagnetic origin. We suppose that coronal heating gradually overpowers magnetic tension and causes the streamer to separate into a system of collapsing loops and a flux rope that is carried outward in the solar wind. Title: Secchi Observations of Mass Flows in the Inner Heliosphere Authors: Sheeley, N. R.; Herbst, A. D.; Palatchi, C. A.; Wang, Y. Bibcode: 2007AGUFMSH42A..01S Altcode: We use SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) observations to construct "height/time" maps of material flows in the heliosphere from the Sun to elongation angles beyond 90 degrees. Close to the Sun, we see accelerating tracks of ejecta (like streamer blobs) close to the sky plane. Farther from the Sun, we see groups of parallel tracks, some near the sky plane and some out of the plane. At the greatest elongations, we see a collection of non-parallel tracks, some merging and some crossing, and mainly from directions well out of the sky plane. These maps and their associated time- lapse movies are providing a new view of mass flows and their interactions in the inner heliosphere. Title: The Solar Eclipse of 2006 and the Origin of Raylike Features in the White-Light Corona Authors: Wang, Y. -M.; Biersteker, J. B.; Sheeley, N. R., Jr.; Koutchmy, S.; Mouette, J.; Druckmüller, M. Bibcode: 2007ApJ...660..882W Altcode: Solar eclipse observations have long suggested that the white-light corona is permeated by long fine rays. By comparing photographs of the 2006 March 29 total eclipse with current-free extrapolations of photospheric field measurements and with images from the Solar and Heliospheric Observatory (SOHO), we deduce that the bulk of these linear features fall into three categories: (1) polar and low-latitude plumes that overlie small magnetic bipoles inside coronal holes, (2) helmet streamer rays that overlie large loop arcades and separate coronal holes of opposite polarity, and (3) ``pseudostreamer'' rays that overlie twin loop arcades and separate coronal holes of the same polarity. The helmet streamer rays extend outward to form the plasma sheet component of the slow solar wind, while the plumes and pseudostreamers contribute to the fast solar wind. In all three cases, the rays are formed by magnetic reconnection between closed coronal loops and adjacent open field lines. Although seemingly ubiquitous when seen projected against the sky plane, the rays are in fact rooted inside or along the boundaries of coronal holes. Title: Limits To The Radiative Asymmetry Of The Quiet Solar Disk Authors: Livingston, W. C.; Sheeley, N. R. Bibcode: 2007AAS...210.2503L Altcode: 2007BAAS...39..131L Precise data on the uniformity of photospheric radiation over the solar disk seems not to exist. Such may be needed for the future detection of planets crossing solar-like stellar disks, for example. To obtain this information we have made monochromatic scans along the central meridian of the quiet Sun using single element detectors which do not require ’flat fielding’. The scans were in continua and selected Fraunhofer lines ranging from 3129 to 46880 A; the observational epoch was near solar minimum: Oct 2006 to Feb 2007. The meridian was chosen to avoid rotational doppler shifts. We extract the asymmetry between the N and S hemispheres and this is our main product. In the near IR and visible continuum, averaging over granulation and discounting sunspots, such asymmetry is as low as 0.01%; 0.005% at 34168 A on 8 Feb 2007. In the violet and UV this increases to 1%. In the cores of medium strength photospheric lines and in chromospheric lines the asymmetry is up to 15%. Faculae are the probable source of our measured quiet disk asymmetries, and the continuum at 34168 A is favorable for this reason. Line core scans are in general flatter than continuum scans because they sample thinner, higher layers of the atmosphere, where the temperature gradient is less. Title: Coronal Pseudostreamers Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Rich, N. B. Bibcode: 2007ApJ...658.1340W Altcode: In a recent study of the 2006 solar eclipse, we noted that there are two kinds of coronal streamers: ``helmet streamers,'' which separate coronal holes of opposite magnetic polarity, and ``pseudostreamers,'' which overlie twin loop arcades and separate holes of the same polarity. It is well known that the heliospheric plasma and current sheets represent the outward extension of helmet streamers. Using white-light data from the Large Angle and Spectrometric Coronagraph (LASCO), we here show that pseudostreamers likewise have plasma sheet extensions, across which the polarity does not reverse; these multiple sheets contribute significantly to the brightness of the K corona, although their internal densities tend to be lower than those in the heliospheric plasma sheet. We use current-free extrapolations of photospheric field measurements to simulate the observed brightness patterns in the outer corona, including the contributions of both helmet streamer and pseudostreamer plasma sheets. Running-difference images show that pseudostreamers are relatively quiescent, resembling large-scale plumes; preliminary analysis suggests flow speeds as high as 200 km s-1 at heliocentric distances of only ~3 Rsolar, supporting the prediction (based on their low flux tube divergence rates) that pseudostreamers are sources of fast solar wind. Title: In/Out Pairs and the Detachment of Coronal Streamers Authors: Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 2007ApJ...655.1142S Altcode: We previously described coronal events that originate in the 2-6 Rsolar field of view of the LASCO white-light coronagraph and involve the simultaneous ejection of material inward toward the Sun and outward away from it. Now, in a study of more than 160 in/out pairs, we have found that these features are density enhancements at the leading and trailing edges of depletions that occur when slowly rising coronal structures separate from the Sun. The outward component is shaped like a large arch with both ends attached to the Sun, and the inward component is often resolved into loops. We also found about 60 additional events in which the outward components began near the edge of the occulting disk and inward components were not visible, as if these events were in/out pairs that originated below the 2 Rsolar radius of the occulting disk. We conclude that in/out pairs belong to a broad class of streamer detachments, which include ``streamer blowout'' coronal mass ejections, and we suppose that all of these events occur when rising magnetic loops reconnect to produce an outgoing helical flux rope and an ingoing arcade of collapsing loops. Title: Sources of the Solar Wind at Ulysses during 1990-2006 Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2006ApJ...653..708W Altcode: The Ulysses spacecraft is now well into its third polar orbit around the Sun. Using stackplot displays, we summarize the wind speeds and interplanetary sector polarities recorded by Ulysses since its launch in 1990 and relate the observed patterns to the global evolution of open magnetic regions (coronal holes) over the solar cycle. We verify that the wind speeds are inversely correlated with the rate of flux-tube divergence in the corona, as derived from a current-free extrapolation of the measured photospheric field. We identify the source of each of the long-lived, high-speed streams encountered by Ulysses and discuss their formation, evolution, and rotational properties. Title: Observations of Flux Rope Formation in the Outer Corona Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2006ApJ...650.1172W Altcode: In previous studies employing the Large Angle and Spectrometric Coronagraph (LASCO), we identified a class of white-light ejections that separate into incoming and outgoing components at distances of ~3-5 Rsolar from Sun center. These events, of which up to several per month are observed during high solar activity, are generally preceded by a gradual outward expansion of faint loops over a period of a day or more. The expansion terminates when the streamer material, in the form of an elongated stalk or a sheetlike structure, suddenly tears apart. The collapsing material is sometimes recognizable as a collection of loops, while the ejected component is usually poorly resolved. Here we describe a streamer detachment observed on 2005 December 11, in which the outgoing component can be clearly identified as a cylindrical flux rope with its ends anchored in the Sun. Based on simple three-dimensional white-light reconstructions, we conclude that in/out pairs in general represent the pinching off of streamer loop arcades to form flux ropes, as seen from different viewing angles. Title: Role of the Sun's Nonaxisymmetric Open Flux in Cosmic-Ray Modulation Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Rouillard, A. P. Bibcode: 2006ApJ...644..638W Altcode: We reexamine the empirical relationship between the Sun's open magnetic flux and the cosmic-ray (CR) intensity over the solar cycle. The single parameter that correlates best with the inverted CR rate is found to be the nonaxisymmetric or longitudinally varying component of the total open flux, rather than the sunspot number or the rate of coronal mass ejections (CMEs). The nonaxisymmetric open flux in turn tracks the evolution of the Sun's equatorial dipole component, which is a function of both the strength and the longitudinal distribution of sunspot activity. Year-long peaks in the equatorial dipole strength coincide with steplike decreases in the CR intensity and with the formation of global merged interaction regions (GMIRs) in the outer heliosphere. During these periods, nonaxisymmetric open flux (in the form of low-latitude coronal holes) is created through the organized emergence of large active regions, resulting in the global injection of magnetic energy into the heliosphere. At the same time, strengthenings of the equatorial dipole are generally accompanied by large increases in the number of fast CMEs. Rotationally induced, compressional interactions between the nonaxisymmetric open flux, fast CMEs, and high-speed streams then give rise to outward-propagating diffusive barriers that extend over all longitudes and to a latitude (>~45°) again determined by the equatorial dipole strength. Title: Solar physics: Back to the next solar cycle Authors: Wang, Y. -M.; Sheeley, N. R. Bibcode: 2006NatPh...2..367W Altcode: Many solar physicists expect the peak sunspot activity during the next solar cycle to be at its weakest in almost a century. A recent prediction to the contrary could turn this prevailing wisdom on its head. Title: Probing Solar Open Magnetic Fields With Near-relativistic Electron Beams. Authors: Haggerty, Dennis K.; Rust, D.; Sheeley, N. R.; Wang, Y. Bibcode: 2006SPD....37.1102H Altcode: 2006BAAS...38R.238H To achieve better understanding of our Sun-Earth environment, NASA's Living with a Star (LWS) program addresses question that cut across discipline boundaries. We present preliminary results on probing solar open magnetic fields with near-relativistic electron beams. This effort is directed at the major question: What determines the topology and evolution of the magnetic fields that stretch from the surface of the Sun to the outer boundary of the heliosphere? During nine years of operation, nearly an entire solar cycle, the ACE/EPAM instrument has measured well over 600 near-relativistic electron events. Approximately 30% of these electron events are impulsive with beam-like anisotropies and are predominantly from flares on the western hemisphere. Near-relativistic electrons are accelerated in the low corona and are released onto open coronal field lines, where they propagate nearly scatter-free out to 1 AU. Near-relativistic electrons are ideal probes of coronal open field lines because the transit time to 1 AU is 10 minutes as compared to lower energy ions that spend more time in the interplanetary medium and are therefore much more subject to transport processes. In this work we use observations of electrons from 1 AU, observations of various electromagnetic emissions associated with electron acceleration at the Sun, and observations and models of open magnetic field lines at the Sun to pinpoint the location of electron acceleration. Title: Carrington Maps of the Upper Photosphere Authors: Sheeley, N. R., Jr.; Warren, H. P. Bibcode: 2006ApJ...641..611S Altcode: We have used images of the Sun's disk, obtained in the 6767 Å continuum with the Michelson Doppler Interferometer (MDI) on the Solar and Heliospheric Observatory (SOHO), to make Carrington maps of the upper photosphere during the years 1996-2005. Each map is constructed from observations near the limb where the continuum radiation originates relatively high in the photosphere and faculae have their greatest visibility. Consequently, the Carrington maps resemble spectroheliograms in temperature-sensitive photospheric lines and show the global distribution of faculae and all but the smallest sunspots (which are obscured by overlying faculae). A time-lapse sequence of the combined east-limb and west-limb maps shows the emergence of active regions and the evolution of large-scale patterns of faculae with an average temporal resolution of 14 days during the sunspot cycle. Also, a longitudinally averaged butterfly diagram of these maps shows that in each hemisphere there is a facula-free zone separating the old-cycle polar field from trailing-polarity flux that is migrating poleward from the sunspot belts. These facula-free zones coincide with the neutral zones of the axisymmetric component of photospheric magnetic field and their arrival at the poles in 2001 marks the reversal of the polar fields. We think that this mapmaking technique can be applied to white-light images obtained daily at the Mount Wilson Observatory since 1905 and that the resulting Carrington maps will provide details about the polar-field reversal process during past sunspot cycles when high-quality magnetograms were unavailable. Title: Multi-Wavelength Observations of CMEs and Associated Phenomena. Report of Working Group F Authors: Pick, M.; Forbes, T. G.; Mann, G.; Cane, H. V.; Chen, J.; Ciaravella, A.; Cremades, H.; Howard, R. A.; Hudson, H. S.; Klassen, A.; Klein, K. L.; Lee, M. A.; Linker, J. A.; Maia, D.; Mikic, Z.; Raymond, J. C.; Reiner, M. J.; Simnett, G. M.; Srivastava, N.; Tripathi, D.; Vainio, R.; Vourlidas, A.; Zhang, J.; Zurbuchen, T. H.; Sheeley, N. R.; Marqué, C. Bibcode: 2006SSRv..123..341P Altcode: 2006SSRv..tmp...60P This chapter reviews how our knowledge of CMEs and CME-associated phenomena has been improved, since the launch of the SOHO mission, thanks to multi-wavelength analysis. The combination of data obtained from space-based experiments and ground based instruments allows us to follow the space-time development of an event from the bottom of the corona to large distances in the interplanetary medium. Since CMEs originate in the low solar corona, understanding the physical processes that generate them is strongly dependant on coordinated multi-wavelength observations. CMEs display a large diversity in morphology and kinematic properties, but there is presently no statistical evidence that those properties may serve to group them into different classes. When a CME takes place, the coronal magnetic field undergoes restructuring. Much of the current research is focused on understanding how the corona sustains the stresses that allow the magnetic energy to build up and how, later on, this magnetic energy is released during eruptive flares and CMEs. Multi-wavelength observations have confirmed that reconnection plays a key role during the development of CMEs. Frequently, CMEs display a rather simple shape, exhibiting a well known three-part structure (bright leading edge, dark cavity and bright knot). These types of events have led to the proposal of the ‘`standard model’' of the development of a CME, a model which predicts the formation of current sheets. A few recent coronal observations provide some evidence for such sheets. Other more complex events correspond to multiple eruptions taking place on a time scale much shorter than the cadence of coronagraph instruments. They are often associated with large-scale dimming and coronal waves. The exact nature of these waves and the physical link between these different manifestations are not yet elucidated. We also discuss what kind of shocks are produced during a flare or a CME. Several questions remain unanswered. What is the nature of the shocks in the corona (blast-wave or piston-driven?) How they are related to Moreton waves seen in Hα? How they are related to interplanetary shocks? The last section discusses the origin of energetic electrons detected in the corona and in the interplanetary medium. “Complex type III-like events,”which are detected at hectometric wavelengths, high in the corona, and are associated with CMEs, appear to originate from electrons that have been accelerated lower in the corona and not at the bow shock of CMEs. Similarly, impulsive energetic electrons observed in the interplanetary medium are not the exclusive result of electron acceleration at the bow shocks of CMEs; rather they have a coronal origin. Title: Multi-Wavelength Observations of CMEs and Associated Phenomena Authors: Pick, M.; Forbes, T. G.; Mann, G.; Cane, H. V.; Chen, J.; Ciaravella, A.; Cremades, H.; Howard, R. A.; Hudson, H. S.; Klassen, A.; Klein, K. L.; Lee, M. A.; Linker, J. A.; Maia, D.; Mikic, Z.; Raymond, J. C.; Reiner, M. J.; Simnett, G. M.; Srivastava, N.; Tripathi, D.; Vainio, R.; Vourlidas, A.; Zhang, J.; Zurbuchen, T. H.; Sheeley, N. R.; Marqué, C. Bibcode: 2006cme..book..341P Altcode: This chapter reviews how our knowledge of CMEs and CME-associated phenomena has been improved, since the launch of the SOHO mission, thanks to multi-wavelength analysis. The combination of data obtained from space-based experiments and ground based instruments allows us to follow the space-time development of an event from the bottom of the corona to large distances in the interplanetary medium. Since CMEs originate in the low solar corona, understanding the physical processes that generate them is strongly dependant on coordinated multi-wavelength observations. CMEs display a large diversity in morphology and kinematic properties, but there is presently no statistical evidence that those properties may serve to group them into different classes. When a CME takes place, the coronal magnetic field undergoes restructuring. Much of the current research is focused on understanding how the corona sustains the stresses that allow the magnetic energy to build up and how, later on, this magnetic energy is released during eruptive flares and CMEs. Multiwavelength observations have confirmed that reconnection plays a key role during the development of CMEs. Frequently, CMEs display a rather simple shape, exhibiting a well known three-part structure (bright leading edge, dark cavity and bright knot). These types of events have led to the proposal of the "standard model" of the development of a CME, a model which predicts the formation current sheets. A few recent coronal observations provide some evidence for such sheets. Other more complex events correspond to multiple eruptions taking place on a time scale much shorter than the cadence of coronagraph instruments. They are often associated with large-scale dimming and coronal waves. The exact nature of these waves and the physical link between these different manifestations are not yet elucidated. We also discuss what kind of shocks are produced during a flare or a CME. Several questions remain unanswered. What is the nature of the shocks in the corona (blast-wave or piston-driven?) How they are related to Moreton waves seen in Hα? How they are related to interplanetary shocks? The last section discusses the origin of energetic electrons detected in the corona and in the interplanetary medium. "Complex type III-like events," which are detected at hectometric wavelengths, high in the corona, and are associated with CMEs, appear to originate from electrons that have been accelerated lower in the corona and not at the bow shock of CMEs. Similarly, impulsive energetic electrons observed in the interplanetary medium are not the exclusive result of electron acceleration at the bow shocks of CMEs; rather they have a coronal origin. Title: Surface Evolution of the Sun's Magnetic Field: A Historical Review of the Flux-Transport Mechanism Authors: Sheeley, Neil R., Jr. Bibcode: 2005LRSP....2....5S Altcode: This paper reviews our attempts to understand the transport of magnetic flux on the Sun from the Babcock and Leighton models to the recent revisions that are being used to simulate the field over many sunspot cycles. In these models, the flux originates in sunspot groups and spreads outward on the surface via supergranular diffusion; the expanding patterns become sheared by differential rotation, and the remnants are carried poleward by meridional flow. The net result of all of the flux eruptions during a sunspot cycle is to replace the initial polar fields with new fields of opposite polarity. A central issue in this process is the role of meridional flow, whose relatively low speed is near the limit of detection with Doppler techniques. A compelling feature of Leighton's original model was that it reversed the polar fields without the need for meridional flow. Now, we think that meridional flow is central to the reversal and to the dynamo itself. Title: The Transport of Photospheric Magnetic Flux (Invited) Authors: Sheeley, N. R., Jr. Bibcode: 2005ESASP.592..233S Altcode: 2005soho...16E..35S; 2005ESASP.592E..35S No abstract at ADS Title: Modeling the Sun's Magnetic Field and Irradiance since 1713 Authors: Wang, Y. -M.; Lean, J. L.; Sheeley, N. R., Jr. Bibcode: 2005ApJ...625..522W Altcode: We use a flux transport model to simulate the evolution of the Sun's total and open magnetic flux over the last 26 solar cycles (1713-1996). Polar field reversals are maintained by varying the meridional flow speed between 11 and 20 m s-1, with the poleward-directed surface flow being slower during low-amplitude cycles. If the strengths of the active regions are fixed but their numbers are taken to be proportional to the cycle amplitude, the open flux is found to scale approximately as the square root of the cycle amplitude. However, the scaling becomes linear if the number of active regions per cycle is fixed but their average strength is taken to be proportional to the cycle amplitude. Even with the inclusion of a secularly varying ephemeral region background, the increase in the total photospheric flux between the Maunder minimum and the end of solar cycle 21 is at most ~one-third of its minimum-to-maximum variation during the latter cycle. The simulations are compared with geomagnetic activity and cosmogenic isotope records and are used to derive a new reconstruction of total solar irradiance (TSI). The increase in cycle-averaged TSI since the Maunder minimum is estimated to be ~1 W m-2. Because the diffusive decay rate accelerates as the average spacing between active regions decreases, the photospheric magnetic flux and facular brightness grow more slowly than the sunspot number and TSI saturates during the highest amplitude cycles. Title: Solar Subsurface Flows of Active Region AR~0696 Authors: Komm, R.; Howe, R.; Donaldson Hanna, K.; Hill, F.; Sheeley, N. Bibcode: 2005AGUSMSP24A..02K Altcode: We use a ring-diagram analysis to determine the subsurface flows in the upper 16~Mm of the convection zone from high-resolution Global Oscillation Network Group (GONG) data obtained during the first two weeks of November 2004. The active region AR~0696 emerges near the eastern limb and moves across the disk during this time period. The region produced several terrestrially effective flares and halo CMEs during its transit across the disk. During its disk passage, AR~0696 is the only large active region in the northern hemisphere and almost the only flare producing region on the sun. This makes it a good candidate for investigating the relation between active regions, their flare activity, and associated subsurface flows. We will present the latest results. This work was supported by NASA grant NAG 5-11703. Title: Global Structure of the Out-of-ecliptic Solar Wind Authors: Whang, Y.; Wang, Y.; Sheeley, N.; Burlaga, L. Bibcode: 2005AGUSMSH13A..03W Altcode: We use the observed photospheric field maps and the wind speed observed from Ulysses to study the out-of-ecliptic solar wind. The model calculates the wind speed from the rate of magnetic flux-tube expansion factor using a conversion function that is determined by least-squares fit of all currently available data from Ulysses. Using the best-fit conversion function we investigate the global solar wind at all latitudes, from 90º south to 90º north, covering a 36-year period from 1968 through 2003. The results complement and expand upon earlier studies conducted with IPS and other in situ spacecraft observations. The rotationally averaged wind speed is a function of two parameters: the heliolatitude and the phase of the solar cycle. The out-of-ecliptic solar wind has a recurrent stable structure, the average wind speed varies like a sine square of latitude profile spanning more than 5 years during the declining phase and solar minimum in each solar cycle. Near solar maximum the structure of the out-of-ecliptic solar wind is in a transient state lasting 2 to 3 years when the stable structure breaks down during the disappearance and reappearance of the polar coronal holes. We also report the Ulysses observations of the stable and transient structure. Title: Global structure of the out-of-ecliptic solar wind Authors: Whang, Y. C.; Wang, Y. -M.; Sheeley, N. R.; Burlaga, L. F. Bibcode: 2005JGRA..110.3103W Altcode: 2005JGRA..11003103W We use the observed photospheric field maps and the wind speed observed from Ulysses to study the out-of-ecliptic solar wind. The model calculates the wind speed from the rate of magnetic flux tube expansion factors using a conversion function that is determined by least squares fit of all currently available data from Ulysses. Using the best fit conversion function, we investigate the global solar wind covering a 36-year period from 1968 through 2003. The results complement and expand upon earlier studies conducted with interplanetary scintillation and other in situ spacecraft observations. The rotationally averaged wind speed is a function of two parameters: the heliolatitude and the phase of the solar cycle. The out-of-ecliptic solar wind has a recurrent stable structure, and the average wind speed varies like a sine square of latitude profile spanning more than 5 years during the declining phase and solar minimum in each solar cycle. Ulysses has observed this stable structure in its first polar orbit in 1992-1997. Near solar maximum the structure of the out-of-ecliptic solar wind is in a transient state lasting 2-3 years when the stable structure breaks down during the disappearance and reappearance of the polar coronal holes. Title: The Origin of Postflare Loops Authors: Sheeley, N. R., Jr.; Warren, H. P.; Wang, Y. -M. Bibcode: 2004ApJ...616.1224S Altcode: We apply a tracking technique, previously developed to study motions in the outer corona by Sheeley, Walters, Wang, and Howard, to 195 Å filtergrams obtained with the Transition Region and Coronal Explorer (TRACE) satellite and obtain height-time maps of the motions in the hot (10-20 MK) plasma clouds above postflare loop systems. These maps indicate the following two main characteristics. (1) Within the plasma cloud, the motions are downward at speeds of approximately 4 km s-1. The cloud itself grows with time, its upper layers being replenished by the arrival and deceleration of fast inflows and its lower layers disappearing when they cool to form the tops of new postflare loops. (2) Early in these events, the inward motions are turbulent, showing a variety of dark elongated features resembling ``tadpoles'' and some bright features. Later, the inflows are visible as dark collapsing loops, changing from initially cusp-shaped features to rounder loops as they move inward. Their speeds initially lie in the range 100-600 km s-1 but decrease to 4 km s-1 in about 3 minutes, corresponding to an average deceleration ~1500 m s-2. Combining these observations with similar observations obtained at reconnection sites in the outer corona by the Large Angle Spectrometric Coronagraph (LASCO), we conclude that postflare loops are the end result of the formation, filling, deceleration, and cooling of magnetic loops produced by the reconnection of field lines blown open in the flare. The formation of collapsing loops occurs in the dark tadpoles; the filling of these initially dark loops occurs via chromospheric evaporation, which also contributes to the deceleration of the loops; and the radiative cooling ultimately resolves the loops into sharply defined structures. Title: Footpoint Switching and the Evolution of Coronal Holes Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2004ApJ...612.1196W Altcode: We discuss the role of footpoint exchanges between open and closed magnetic field lines (also known as ``interchange reconnection'') in the formation and rotational evolution of coronal holes. Such exchanges cause open flux to jump from one location to another when active regions emerge; they also act to untie the rotation of coronal holes from that of the underlying plasma. We introduce a quantitative measure of the footpoint exchange rate and apply it to a variety of idealized configurations. During the formation of coronal holes, footpoint switching dominates over the creation of new open flux if the background (or polar) field is strong compared to that of the emerging active region, so the latter acts to change mainly the direction rather than the magnitude of the Sun's dipole vector. The principal role of footpoint exchanges is to counteract the subsequent rotational shearing of the holes; this result is accomplished by means of continual sideways displacements of open and closed field lines along the hole boundaries. Because the timescale for rotational shearing (~3 months) is less than that for the decay of the Sun's large-scale nonaxisymmetric field (~1 yr), interchange reconnection is expected on average to dominate over the closing down of flux throughout the solar cycle. Title: The termination shock near 35° latitude Authors: Whang, Y. C.; Burlaga, L. F.; Wang, Y. -M.; Sheeley, N. R. Bibcode: 2004GeoRL..31.3805W Altcode: 2004GeoRL..3103805W The termination shock moves outwards and inwards over timescales of a solar cycle in response to the variations in the average solar wind speed. The amplitude is greater than 50 AU near 35° latitude; the maximum (minimum) distance occurs during the rising (declining) phase of the solar cycle. Shock parameters are distinctly different when the shock moves outwards or inwards. During the period of high-speed (low-speed) solar wind, the shock moves outward (inward) and the shock is weaker (stronger). This study assumes that the first crossing of Voyager 1 with the termination shock occurred at 85.5 AU on 2002.6. If Voyager 1 did cross the shock in 2002.6, the spacecraft would likely cross the shock at least two more times before 2010, but no second crossing would occur close to 2003.1. If Voyager 1 did not cross the shock in mid-2002, it might still do so before 2005. Title: The termination shock near 35 degrees latitude Authors: Whang, Y. C.; Burlaga, L. F.; Wang, Y.; Sheeley, N. R. Bibcode: 2003AGUFMSH11C1115W Altcode: The paper calculates the solar cycle variation of the termination shock near 35 degrees latitude. The solution assumes that Voyager 1 crossed the termination shock at 85.5 AU on 2002.6. At mid latitudes, the termination shock is an oblique shock; the shock location is unambiguously solar cycle dependent with amplitude greater than 50 AU. The maximum (minimum) distance occurs during the rising (declining) phase of the solar cycle. During the period of high-speed (low-speed) solar wind, the termination shock moves outward (inward) and the shock is weaker (stronger). The calculation provides the shock speed, the shock strength, the preshock and postshock solar wind speed, and the flow speed in the shock frame of reference. The shock parameters are distinctly different depending on whether the shock moves outward or inward. If Voyager 1 did cross the termination shock in 2002.6, it would likely cross the shock coming back to the solar wind near 98 AU in 2006 during the next outward motion of the termination shock, while in 2010 the spacecraft would cross the termination shock back into the heliosheath near 113 AU during the inward motion of the termination shock near the maximum of Cycle 24. If Voyager 1 did not cross the termination shock in mid-2002, it might still do so before 2005. Title: Relating Interplanetary Helium Variation to Coronal Magnetic Fields and Solar Wind Formation Authors: Kasper, J. C.; Lazarus, A. J.; Steinberg, J. T.; Riley, P.; Sheeley, N.; Wang, Y. Bibcode: 2003AGUFMSH11D1136K Altcode: We have recently identified two new features in the variation of the relative abundance of helium in the solar wind relative to hydrogen as observed by the Wind spacecraft. First, the He/H ratio is a linear function of speed for solar wind speeds ranging from 250-550 km/s. This signal is most evident during the previous solar minimum from 1995 through 1997. Secondly, during that same quiet interval we have identified a six-month periodic modulation of the He/H ratio which can be seen at all solar wind speeds. This modulation is in phase with the orbit of the Earth about the Sun, and maxima in He/H occur at the times when Earth is most distant from the heliographic equator. As we shall demonstrate, these effects are partly in agreement with theoretical models of the magnetic topology of the corona and of the formation of the solar wind. However, these features present challenges to the currently accepted paradigm of solar wind, with helium-poor wind emerging from coronal streamers and fast, helium-rich wind emerging from coronal holes. The abundance of helium is a sensitive test of models of solar wind formation and of the connection between photospheric, coronal, and interplanetary magnetic fields. The observed variations of He/H will be discussed in terms of existing models of coronal magnetic field topology and solar wind acceleration. This research is supported by the NSF/SHINE grant ATM-0327723. Title: On the Topological Evolution of the Coronal Magnetic Field During the Solar Cycle Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2003ApJ...599.1404W Altcode: Using an axisymmetric model that includes the effects of flux emergence and surface transport processes, we calculate the evolution of the photospheric magnetic field over the solar cycle and derive a corresponding sequence of coronal configurations by means of a potential-field source-surface extrapolation. By identifying magnetic neutral points and tracking changes in the total flux within each topological domain, we construct an overall picture of how open and closed flux is transported as the coronal field reverses its polarity:1. During the rising phase of the cycle, an X-point forms above the emerging flux (represented by a bipole structure) in each hemisphere, and the overlying, opposite-polarity field lines are ``stripped away'' (reconnected to each side); at the same time, as the Sun's axial dipole strength decreases, open field lines from the polar coronal holes begin to merge at the equator and close down.2. As the rate of flux emergence peaks, the X-point rises toward the source surface and the bipole opens up, forming a trailing-polarity hole on its poleward side, which evolves into the new-cycle polar hole; the leading-polarity open flux on the equatorward side of the bipole progressively closes down by merging with its opposite-hemisphere counterpart.3. Later in the declining phase of the cycle, the opposite-hemisphere bipoles begin to reconnect with each other at an equatorial X-point, producing long trailing-polarity loops that rise toward the source surface and continue to feed flux into the new-cycle polar holes, and short leading-polarity loops that collapse toward the photosphere and eventually submerge.We compare the case in which the transport of the photospheric field is by supergranular diffusion alone with that in which both diffusion and a 20 m s-1 poleward flow are present; the latter model is shown to reproduce more closely the coronal topologies inferred from the observed photospheric field. Title: Voyager 1 Studies of the HMF to 81 AU During the Ascending Phase of Solar Cycle 23 Authors: Burlaga, L. F.; Ness, N. F.; Wang, Y. -M.; Sheeley, N. R. Bibcode: 2003AIPC..679...39B Altcode: The paper analyzes the magnetic field strength B and polarity observed in the distant heliosphere from 1996 to early 2001 and will be discussed in relation to the variation of B from 1978 through 1996. The observations extend the results of Burlaga et al. [1]. The polarity of the heliospheric magnetic field (HMF) from 1997 to early 2001 is studied in relation to the extrapolated position of the heliospheric current sheet (HCS). These observations of polarity extend the earlier results of Burlaga et al. [2] and Burlaga and Ness [3]. The V1 observations of the heliospheric magnetic field strength B agree with Parker's model of the global heliospheric magnetic field from 1 to 81 AU and from 1978 to 2001, when one considers the solar cycle variations in the source magnetic field strength and the latitude/time variation in the solar wind speed. Parker's model, without adjustable parameters, describe the general tendency for B to decrease with increasing distance R from the Sun, and the solar cycle time variations causing the three broad increases of B around 1980, 1990, and 2000, and the minima of B in 1987 and 1997. The variation of magnetic polarity observed by V1 and V2 was caused by the increasing latitudinal width of the sector zone with increasing solar activity, which in turn was related to the increasing maximum latitudinal extent and the decreasing minimum latitudinal extent of the footpoints of the HCS. Title: Linear Polarization Measurements of Chromospheric Emission Lines Authors: Sheeley, N. R., Jr.; Keller, C. U. Bibcode: 2003ApJ...594.1085S Altcode: We have used the Zurich Imaging Stokes Polarimeter (ZIMPOL I) with the McMath-Pierce 1.5 m main telescope on Kitt Peak to obtain linear polarization measurements of the off-limb chromosphere with a sensitivity better than 1×10-5. We found that the off-disk observations require a combination of good seeing (to show the emission lines) and a clean heliostat (to avoid contamination by scattered light from the Sun's disk). When these conditions were met, we obtained the following principal results:1. Sometimes self-reversed emission lines of neutral and singly ionized metals showed linear polarization caused by the transverse Zeeman effect or by instrumental cross talk from the longitudinal Zeeman effect in chromospheric magnetic fields. Otherwise, these lines tended to depolarize the scattered continuum radiation by amounts that ranged up to 0.2%.2. Lines previously known to show scattering polarization just inside the limb (such as the Na I λ5889 D2 and the He I λ5876 D3 lines) showed even more polarization above the Sun's limb, with values approaching 0.7%.3. The O I triplet at λ7772, λ7774, and λ7775 showed a range of polarizations. The λ7775 line, whose maximum intrinsic polarizability, Pmax, is less than 1%, revealed mainly Zeeman contributions from chromospheric magnetic fields. However, the more sensitive λ7772 (Pmax=19%) and λ7774 (Pmax=29%) lines had relatively strong scattering polarizations of approximately 0.3% in addition to their Zeeman polarizations. At times of good seeing, the polarization spectra resolve into fine structures that seem to be chromospheric spicules. Title: Modeling the Sun's Large-Scale Magnetic Field during the Maunder Minimum Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2003ApJ...591.1248W Altcode: We use a flux transport model to simulate the evolution of the Sun's magnetic dipole moment, polar fields, and open flux under Maunder minimum conditions. Even when the rate of active region emergence is taken to be a factor of ~30 smaller than in recent solar cycles, regular polarity oscillations of the axial dipole and polar fields can be maintained if the speed of the poleward surface flow is reduced from ~20 to ~10 m s-1 and the source flux emerges at very low latitudes (~10°). The axial dipole is then found to have an amplitude of the order of 0.5 G, as compared with ~4 G during solar cycle 21. The strength of the radial interplanetary field component at Earth is estimated to be in the range ~0.3-0.7 nT, about a factor of 7 lower than contemporary values. We discuss the implications of these weak fields for our understanding of geomagnetic activity and cosmic-ray modulation during the Maunder minimum. Title: On the Fluctuating Component of the Sun's Large-Scale Magnetic Field Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2003ApJ...590.1111W Altcode: The Sun's large-scale magnetic field and its proxies are known to undergo substantial variations on timescales much less than a solar cycle but longer than a rotation period. Examples of such variations include the double activity maximum inferred by Gnevyshev, the large peaks in the interplanetary field strength observed in 1982 and 1991, and the 1.3-1.4 yr periodicities detected over limited time intervals in solar wind speed and geomagnetic activity. We consider the question of the extent to which these variations are stochastic in nature. For this purpose, we simulate the evolution of the Sun's equatorial dipole strength and total open flux under the assumption that the active region sources (BMRs) are distributed randomly in longitude. The results are then interpreted with the help of a simple random walk model including dissipation. We find that the equatorial dipole and open flux generally exhibit multiple peaks during each 11 yr cycle, with the highest peak as likely to occur during the declining phase as at sunspot maximum. The widths of the peaks are determined by the timescale τ~1 yr for the equatorial dipole to decay through the combined action of meridional flow, differential rotation, and supergranular diffusion. The amplitudes of the fluctuations depend on the strengths and longitudinal phase relations of the BMRs, as well as on the relative rates of flux emergence and decay. We conclude that stochastic processes provide a viable explanation for the ``Gnevyshev gaps'' and for the existence of quasi periodicities in the range ~1-3 yr. Title: Solar Wind Speed and Temperature Outside 10 AU and the Termination Shock Authors: Whang, Y. C.; Burlaga, L. F.; Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2003ApJ...589..635W Altcode: In this paper we first present a series of pickup proton solar wind solutions following the fluid motion in the upwind direction to show that the wind speed V and temperature T, at a given r outside 10 AU, are primarily functions of the 1 AU wind speed V0. This relationship is attributed to the accumulated effects of the pickup proton process on the heating and deceleration of the solar wind. Because pickup protons are expected to have similar effects on the solar wind at all latitudes in the upwind side of the heliosphere, in the second part of the paper, the two formulae V(r, V0) and T(r, V0) are extended to study the termination shock at 35° latitude. Wang and Sheeley have an empirical model for calculating the 1 AU wind speed V0 from the observed photospheric field. We use the simulated wind speed V0 to calculate V and T outside 60 AU following the fluid motion; then we can study the solar cycle variation of the termination shock. The shock location near 35° is unambiguously dependent on the solar cycle, with a period of approximately 1 solar cycle; the amplitude for variation of the shock location is greater than 50 AU. The new result supports the idea that the first encounter of Voyager 1 with the termination shock may occur during the declining phase of cycle 23. After the first encounter, the spacecraft will cross the shock two more times over a period of 8 years. Title: The Solar Wind and Its Magnetic Sources at Sunspot Maximum Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2003ApJ...587..818W Altcode: We use in situ measurements from the Advanced Composition Explorer and magnetograph data from the National Solar Observatory to relate the properties of the solar wind during 1998-2002 to its source region magnetic fields. The great bulk of the solar maximum wind is characterized by low proton speeds (vp~420 km s-1) and high oxygen charge state ratios (nO7+/nO6+~0.3). This slow wind originates from small, sheared open-field regions located near active regions and characterized by very large flux tube expansion factors (fexp>>10) and high footpoint field strengths (B0~30 G). In contrast, the occasional high-speed streams emanate from weak-field regions (B0~5 G) with small expansion factors (fexp~4) and show relatively low charge state ratios (nO7+/nO6+~0.1) their proton velocities (vp~550 km s-1) are substantially reduced by interactions with the surrounding sea of low-speed wind. We attribute the high freeze-in temperatures of the slow wind to enhanced heating taking place in the low corona in the presence of the very strong, rapidly diverging source fields, which are found to be correlated with high mass and energy flux densities at the coronal base. Title: Modeling the Sun's polar fields and open flux during the Maunder Minimum Authors: Wang, Y.; Lean, J.; Sheeley, N. Bibcode: 2003EAEJA.....2424W Altcode: We use a flux transport model to simulate the evolution of the Sun's polar fields and open magnetic flux under Maunder Minimum conditions. Even when the rate of active region emergence is taken to be a factor of 50--100 smaller than in recent cycles, we find that 11 yr polarity oscillations of the polar fields can be maintained if the speed of the poleward surface flow is reduced from 20 m/s to 10 m/s and the magnetic flux is assumed to emerge at low latitudes. The strength of the radial IMF component is inferred to be in the range ∼0.2--0.6 nT, about a factor of 10 weaker than at present but with a stronger solar-cycle modulation. We discuss the relationship between our simulation results and what is known observationally about the Maunder Minimum. Title: Meridional Flow and the Solar Cycle Variation of the Sun's Open Magnetic Flux Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Lean, J. Bibcode: 2002ApJ...580.1188W Altcode: We simulate the evolution of the Sun's large-scale magnetic field during solar cycle 21, including the effect of surface transport processes and active region emergence. As an important new constraint on the model, we have scaled our source fluxes upward to be consistent with the average measured strength of the interplanetary magnetic field (IMF). By adopting a poleward bulk flow of amplitude ~20-25 m s-1 together with a supergranular diffusion rate of ~500 km2 s-1, we are then able to match the observed variation of the Sun's polar fields and open magnetic flux. The high meridional flow speeds, peaking at low latitudes, prevent the buildup of an overly strong axisymmetric dipole component at sunspot minimum, while accounting for the giant poleward surges of flux and accompanying polar field fluctuations observed near sunspot maximum. The present simulations also reproduce the large peak in the equatorial dipole and IMF strength recorded in 1982. Title: Polarity reversal of the solar magnetic field during cycle 23 Authors: Wang, Y. -M.; Sheeley, N. R.; Andrews, M. D. Bibcode: 2002JGRA..107.1465W Altcode: Using magnetograph data, coronagraph observations, and source surface extrapolations, we examine the evolution of the photospheric magnetic field from 1996 through the 2000-2001 polarity reversal and show how this evolution is reflected in coronal holes, coronal streamers, the heliospheric current sheet (HCS), and the solar wind. The photospheric polarity reversal is completed in the more active Northern Hemisphere in late 2000 and then in the Southern Hemisphere in 2001. The polar coronal holes disappear in 2000 and start to re-form in 2001; during this interval, most of the open magnetic flux resides in the active region latitudes, where small coronal holes with strong footpoint fields generate predominantly slow solar wind. The nondipolar nature of the large-scale coronal field at sunspot maximum gives rise to complex streamer/HCS topologies, in which a four-sector structure and even a secondary, detached current sheet with cylindrical geometry are sometimes present. Comparison of the potential field extrapolations with coronagraph and Ulysses observations suggests that the magnetograph measurements may have underestimated the strength of the south polar field during late 2000. Title: The effect of increasing solar activity on the Sun's total and open magnetic flux during multiple cycles: Implications for solar forcing of climate Authors: Lean, J. L.; Wang, Y. -M.; Sheeley, N. R. Bibcode: 2002GeoRL..29.2224L Altcode: 2002GeoRL..29x..77L We investigate the relationship between solar irradiance and cosmogenic isotope variations by simulating with a flux transport model the effect of solar activity on the Sun's total and open magnetic flux. As the total amount of magnetic flux deposited in successive cycles increases, the polar fields build up, producing a secular increase in the open flux that controls the interplanetary magnetic field which modulates the cosmic ray flux that produces cosmogenic isotopes. Non-axisymmetric fields at lower latitudes decay on time scales of less than a year; as a result the total magnetic flux at the solar surface, which controls the Sun's irradiance, lacks an upward trend during cycle minima. This suggests that secular increases in cosmogenic and geomagnetic proxies of solar activity may not necessarily imply equivalent secular trends in solar irradiance. Questions therefore arise about the interpretation of Sun-climate relationships, which typically assume that the proxies imply radiative forcing. Title: Solar Wind Speed and Temperature Outside 10 AU and the Termination Shock Authors: Whang, Y. C.; Burlaga, L. F.; Wang, Y.; Sheeley, N. R. Bibcode: 2002AGUFMSH11A0376W Altcode: We study the speed V and temperature T of the solar wind in the distant heliosphere obtained from pickup proton magnetohydrodynamic equations that treat interstellar pickup protons and solar wind protons as two distinct proton species. The study uses the 27-day average Omni plasma and magnetic field data as input. We obtain 336 sets of numerical solutions covering the period from the solar minimum of Cycle 20 in 1976 to the maximum of Cycle 23; each represents the extrapolation for the real solar wind conditions at 1 AU to the distant heliosphere following the fluid motion. The result shows that outside 10 AU near the ecliptic V and T at a given r are primarily functions of the 1 AU wind speed. The maximum of the 1 AU wind speed is 615 km/s occurred on March 1989, the minimum at 327 km/s occurred on February 1999. A straight line can be used to represent the relation between V and the 1 AU speed for each given r; and a parabola can represent the relation for T at each given r. These relations are attributed to the accumulated effects of pickup proton process in the distant heliosphere. Because pickup protons are expected to have similar effects on the solar wind at all latitudes on the upwind side of the heliosphere, the relationships for V and T are extended to study the solar cycle and latitudinal variation for the heliocentric distance of the termination shock. Wang and Sheeley have an empirical model to calculate the 1 AU wind speed as a function of latitude and longitude from the observed photospheric field. The calculated latitudinal variation is consistent with the observational results from Ulysses. We use the simulated 1 AU speed to calculate V and T at varying r following the fluid motion. Then we can calculate the solar cycle variation of the shock distance at all latitudes over a 26-year's period. The averaged distance increases with the latitude; from ecliptic to the pole the distance increases by a factor of 2. Title: Characteristics of Coronal Inflows Authors: Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 2002ApJ...579..874S Altcode: This paper describes coronal inflows observed with the Large Angle Spectrometric Coronagraph (LASCO). The inflows are not seen above 5.5 Rsolar, which appears to be a ``point of no return'' for the Sun's plasmas and fields. Below this height, most inflows seem to indicate magnetic flux that is returning to the Sun after its reconnection at sector boundaries. Some inflows have characteristics (like fast, oppositely directed ejections of material) that are easily interpreted in terms of conventional models of field line reconnection. However, the overwhelming majority of coronal inflows have a more complex behavior that typically includes the following characteristics:1. The birth of a very weak, localized density enhancement about 4-5 Rsolar from Sun center and its initially slow downward motion along a coronal ray;2. Acceleration to a maximum speed of 50-100 km s-1, and the formation of a sinking column;3. Deceleration and the appearance of a dark depletion tail, visible against the bright background structures in the lower corona;4. The formation of a stretched loop below about 2.5 Rsolar.We suppose that the initial downward motion is a preparatory stage for reconnection, which occurs in the depleted region in the wake of the sinking column and is later revealed by the formation of a stretched loop in the lower corona. Title: Heliospheric magnetic field strength and polarity from 1 to 81 AU during the ascending phase of solar cycle 23 Authors: Burlaga, L. F.; Ness, N. F.; Wang, Y. -M.; Sheeley, N. R. Bibcode: 2002JGRA..107.1410B Altcode: The Voyager 1 (V1) observations of the heliospheric magnetic field strength B agree with Parker's model of the global heliospheric magnetic field from 1 to 81.0 AU and from 1978 to 2001.34 when one considers the solar cycle variations in the source magnetic field strength and the latitude/time variation in the solar wind speed. In particular, Parker's model, without adjustable parameters, describes the general tendency for B to decrease with increasing distance R from the Sun, the three broad increases of B around 1980, 1990, and 2000, and the minima of B in 1987 and 1997. During 1987 and 1997, B appears to be lower than Parker's model predicts, but that can be attributed to the presence of a heliospheric vortex street at these times and/or uncertainty in the observations. There is no evidence for a significant flux deficit increasing monotonically from 1 to 81.0 AU. By extrapolating these results and considering the limitations of the observations, V1 should continue to make useful measurements during the next few years at least. The magnetic field polarity in the distant heliosphere at V1 and Voyager 2 (V2) changed during the ascending phase of solar cycle 23. In the Northern Hemisphere, V1 observed a decrease in the percentage of positive polarities from ≈100% during 1997 to ≈50% during 2000. In the Southern Hemisphere, V2 observed the opposite behavior, an increase in the percentage of positive polarities from ≈0% during 1997 to ≈50% during 2000. The variation of magnetic polarity observed by V1 and V2 was caused by the increasing latitudinal width of the sector zone with increasing solar activity, which in turn was related to the increasing maximum latitudinal extent and the decreasing minimum latitudinal extent of the footprints of the heliospheric current sheet (HCS). There was a tendency for the speed and proton temperature to decrease and the density to increase at V2 from 1997 (when it observed flows from polar coronal holes) to 2001 (when it observed more complex and dynamic flows). Title: Sunspot activity and the long-term variation of the Sun's open magnetic flux Authors: Wang, Y. -M.; Sheeley, N. R. Bibcode: 2002JGRA..107.1302W Altcode: The interplanetary magnetic field (IMF) originates in open magnetic regions of the Sun (coronal holes), which in turn form mainly through the emergence and dispersal of active region fields. The radial IMF strength is proportional to the total open flux Φopen, which can be estimated from source surface extrapolations of the measured photospheric field, after correction for magnetograph saturation effects. We derive the long-term variation of Φopen during 1971-2000 and discuss its relation to sunspot activity. The average value of Φopen was ∼20-30% higher during 1976-1996 than during 1971-1976 and 1996-2000, with major peaks occurring in 1982 and 1991. Near sunspot minimum, most of the open flux resides in the large polar coronal holes, whereas at sunspot maximum it is rooted in relatively small, low-latitude holes located near active regions and characterized by strong footpoint fields; since the decrease in the total area occupied by holes is offset by the increase in their average field strengths, Φopen remains roughly constant between activity minimum and maximum, unlike the total photospheric flux Φtot. The long-term variation of Φopen approximately follows that of the Sun's total dipole strength, with a contribution from the magnetic quadrupole around sunspot maximum. Global fluctuations in sunspot activity lead to increases in the equatorial dipole strength and hence to enhancements in Φopen and the IMF strength lasting typically ∼1 year. We employ simulations to clarify the role of active region emergence and photospheric transport processes in the evolution of the open flux. Representing the initial field configuration by one or more bipolar magnetic regions (BMRs), we calculate its subsequent evolution under the influence of differential rotation, supergranular convection, and a poleward bulk flow. The initial value of Φopen is determined largely by the equatorial dipole strength, which in turn depends on the longitudinal phase relations between the BMRs. As the surface flow carries the BMR flux to higher latitudes, the equatorial dipole is annihilated on a timescale of ∼1 year by the combined effect of rotational shearing and turbulent diffusion. The remaining flux becomes concentrated around the poles, and Φopen approaches a limiting value that depends on the axisymmetric dipole strengths of the original BMRs. The polar coronal holes thus represent the long-lived, axisymmetric remnant of the active regions that emerged earlier in the cycle. Title: A comparison of mean density and microscale density fluctuations in a CME at 10 Rsolar Authors: Lynch, B. J.; Coles, W. A.; Sheeley, N. R. Bibcode: 2002GeoRL..29.1913L Altcode: 2002GeoRL..29s..19L We have observed intensity scintillation (IPS) of the radio source 0854 + 201 at 8 GHz on August 2, 2000 during the passage of a coronal mass ejection (CME) across the line of sight. The source was at a distance of 10 Rsolar over the north solar pole. Simultaneous observations with the LASCO C3 instrument allow us to model the mean density Ne and the microscale density fluctuations δNe within the CME. We find that Ne increased by a factor of 2.18 but δNe increased by only 1.76, so the ratio δNe/Ne is 19% smaller than in the pre-CME slow wind. During the passage of the CME a short burst of enhanced turbulence doubled the IPS variance but was not visible in the C3 images. This was likely caused by a thin flux tube crossing the line of sight. Detailed modeling indicates that the diameter of the tube was 41,000 km and its density was 14.5 times the CME density. Title: Role of a Variable Meridional Flow in the Secular Evolution of the Sun's Polar Fields and Open Flux Authors: Wang, Y. -M.; Lean, J.; Sheeley, N. R., Jr. Bibcode: 2002ApJ...577L..53W Altcode: We use a magnetic flux transport model to simulate the evolution of the Sun's polar fields and open flux during solar cycles 13 through 22 (1888-1997). The flux emergence rates are assumed to scale according to the observed sunspot-number amplitudes. We find that stable polarity oscillations can be maintained if the meridional flow rate is allowed to vary from cycle to cycle, with higher poleward speeds occurring during the more active cycles. Our model is able to account for a doubling of the interplanetary field strength since 1900, as deduced by Lockwood, Stamper, & Wild from the geomagnetic aa index. We confirm our earlier conclusion that such a doubling of the open flux does not imply that the base level of the total photospheric flux has increased significantly over the last century. Title: Coronal White-Light Jets near Sunspot Maximum Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2002ApJ...575..542W Altcode: During the 1996-1997 activity minimum, the Large Angle and Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) recorded numerous jetlike ejections above the Sun's polar regions. In a previous study, we showed that these white-light ejections were the outward extensions of extreme-ultraviolet (EUV) jets, which in turn originated from flaring bright points inside the polar coronal holes. Here we investigate a number of jetlike events observed with LASCO during the current sunspot maximum. To identify the solar surface counterparts of these events, we again use Fe XII λ195 images obtained by the EUV Imaging Telescope on SOHO. The white-light jets in our sample have angular widths of ~3°-7° and velocities typically of order 600 km s-1 they tend to be brighter and wider than the polar jets observed near sunspot minimum and are distributed over a much greater range of latitudes. Many of the ejections are recurrent in nature and originate from active regions located inside or near the boundaries of nonpolar coronal holes. We deduce that the jet-producing regions consist of systems of closed magnetic loops partially surrounded by open fields; perturbations in the closed fields caused them to reconnect with the overlying open flux, releasing the trapped energy in the form of jetlike ejections. In some events, the core of the active region erupts, producing fast, collimated ejections with widths of up to ~15°. Title: Solar Energetic Particle Production by Shocks in Fast and Slow Solar Wind Structures Authors: Kahler, S. W.; Reames, D. V.; Sheeley, N. R., Jr. Bibcode: 2002AAS...200.3702K Altcode: 2002BAAS...34..694K Gradual solar energetic particle (SEP) events at 1 AU are produced by coronal and interplanetary shocks driven by coronal mass ejections (CMEs). Shocks from fast (V > 900 km/s) CMEs should be produced more easily in slow solar wind regions where the flow and fast-mode MHD wave speeds are low and less easily in fast solar wind regions where those speeds are high. We might therefore expect to observe more intense SEP events at 1 AU when the Earth lies in a slow wind region than when it lies in a fast wind region. While stream-stream interactions wash out the slow-fast stream boundaries in the solar wind speed profiles at 1 AU, the O+7/O+6 signatures of the streams are unchanged at 1 AU. We use the 20 MeV proton intensities from the EPACT instrument on Wind, the associated CMEs observed with the Lasco coronagraph on SOHO, and the ACE SWICS/SWIMS solar wind values of O+7/O+6 to look for variations of peak SEP intensities as a function of O+7/O+6. We find no significant dependence of the SEP intensities on O+7/O+6 for either poorly connected or well connected CME source regions or for different CME speed ranges. While a broad range of angular widths are associated with fast (V > 900 km/s) CMEs, we find that no fast CMEs with widths < 60 degrees are associated with SEP events. On the other hand, nearly all fast halo CMEs are associated with SEP events. Thus the CME widths are more important in SEP production than previously thought, but the solar wind source regions in which SEPs are produced are not a significant factor. Title: Observations of Core Fallback during Coronal Mass Ejections Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 2002ApJ...567.1211W Altcode: White-light observations made with the Large Angle and Spectrometric Coronagraph (LASCO) during the present solar maximum have revealed a multitude of faint, inward-moving features at heliocentric distances of r~2-6 Rsolar. Most of these structures appear to originate above r~3 Rsolar and may be signatures of the closing-down of magnetic flux at the boundaries of coronal holes or in the aftermath of coronal mass ejections (CMEs). Here, we present observations of a different type of inflow, in which material within the bright core of a CME collapses back toward the Sun after rising to heights of r~2.5-6 Rsolar. We have identified roughly 20 such fallback events during 1998-2001. The core structures, which have the form of loops or concave-outward flux ropes, ascend into the coronagraph field of view beyond 2 Rsolar with speeds of ~100-400 km s-1 but return with speeds of only ~50-200 km s-1. The initial deceleration rates of ~20-100 m s-2 are comparable to the local gravitational deceleration GMsolar/r2 but continually decrease with time. The associated CMEs tend to be impulsive but relatively slow, with the leading front moving outward at ~250-450 km s-1 and often showing some deceleration. It is thus not surprising that some fraction of the core material fails to reach escape speeds, remaining bound to the Sun by gravitational and magnetic tension forces. We suggest that the dynamical behavior of the core may be determined in part by momentum exchanges with the background medium, which consists of ongoing outflows of CME material, ambient solar wind, and inflow streams. In particular, we attribute the asymmetry of the up-down trajectories to the action of such drag forces, whose direction changes from inward to outward as the core decelerates. Title: Coronal Mass Ejections Associated with Impulsive Solar Energetic Particle Events Authors: Kahler, S. W.; Reames, D. V.; Sheeley, N. R., Jr. Bibcode: 2001ApJ...562..558K Altcode: An impulsive solar energetic particle (SEP) event observed on the Wind spacecraft on 2000 May 1 was associated with an impulsive solar active region M1 X-ray flare. The timing and position of a fast (v=960 km s-1), narrow CME observed in the LASCO coronagraph on SOHO make clear the connection between the CME and the flare and SEP event. Impulsive SEP events have long been associated with impulsive flares, but only gradual SEP events have thus far been found to be associated with CMEs. A comparison of impulsive SEP events with CME observations from the Solwind and LASCO coronagraphs revealed further good cases of narrow (10°-40°) CMEs associated with impulsive SEP events. A recent model of impulsive flares includes jets or plasmoids that are ejected upward from magnetic reconnection sites over active regions and might therefore be expected to appear in exceptional cases as faint and narrow CMEs in coronagraphs. We suggest that this model allows us to understand better SEP production and propagation in impulsive flares. Title: Coronal Inflows and Sector Magnetism Authors: Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 2001ApJ...562L.107S Altcode: We have remeasured the rate of coronal inflows during 1996-2001, taking into account multiple occurrences per day, and have displayed the results in Carrington stack plots to study their long-term behavior. The stack plots show long-lived recurrence patterns related to the sectorial component of the Sun's large-scale field. In particular, most inflows are parts of streams that last for several months and occur where the sectorial field has strong gradients. The occurrence rate occasionally approaches ~1 hr-1 near sunspot maximum when the sectorial field is strong and the streamer belt is greatly distorted from its flattened equatorial configuration. The link between coronal inflows and sector magnetism suggests that the inflows are by-products of a global recycling process in which nonaxisymmetric open flux is provided by active regions and dissipated by differential rotation, supergranular diffusion, and meridional flow. Title: Associations of Accelerating CMEs with Solar Energetic Particle Events Authors: Kahler, S.; Sheeley, N.; Reames, D. Bibcode: 2001AGUSM..SH22B03K Altcode: Gradual solar energetic particle (SEP) events are well associated with fast coronal mass ejections (CMEs). The times of significant E > 10 MeV SEP events observed with the Goddard Space Flight Center EPACT detector on the Wind spacecraft have been compared with CME observations from the Lasco coronagraph on the SOHO spacecraft. As earlier studies have shown, a correlation exists between peak SEP intensities and the measured speeds of associated CMEs. Of the CMEs associated with SEP events in the period 1996 to 2000, we find 9 CMEs for which the height-time plots of the leading edges show accelerations of at least 13 m/s/s. The heights at which those CMEs attained speeds of 600 km/s ranged from 7 to 20 Ro. The peak 20 MeV intensities of the 9 SEP events are relatively low compared with all gradual SEP events of the same period. We compare the energy spectra and solar event associations of these 9 SEP events with those of the SEP events associated with CMEs of uniform speeds. Title: Coronal Inflows and the Sun's Nonaxisymmetric Open Flux Authors: Sheeley, N. R., Jr.; Knudson, T. N.; Wang, Y. -M. Bibcode: 2001ApJ...546L.131S Altcode: Wang et al. recently described white-light coronagraph observations of faint coronal features moving inward toward the Sun at heliocentric distances of 2-6 Rsolar. In a study of these inflows during 1996-2000, we have found that they occur along bends of the coronal streamer belt and are especially common when the magnetic field has a four-sector structure. The measured inflow rate is dominated by episodic bursts that are correlated with the occurrence of nonpolar coronal holes and other indicators of the Sun's nonaxisymmetric open flux. However, the inflow rate has only a broad long-term correlation with conventional indicators of solar activity like the sunspot number and coronal mass ejection rate. We conclude that most inflows indicate collapsing field lines that occur as nonpolar coronal holes are subjected to photospheric motions and the eruptions of new flux. Title: The dynamical nature of coronal streamers Authors: Wang, Y. -M.; Sheeley, N. R.; Socker, D. G.; Howard, R. A.; Rich, N. B. Bibcode: 2000JGR...10525133W Altcode: Recent high-sensitivity imaging of the Sun's white-light corona from space has revealed a variety of unexpected small-scale phenomena, including plasma blobs that are ejected continually from the cusplike bases of streamers, fine raylike structures pervading the outer streamer belt, and inflows that occur mainly during times of high solar activity. These phenomena can be interpreted as different manifestations of magnetic field line reconnection, in which plasma and magnetic flux are exchanged between closed and open field regions of the corona. The observations provide new insights into a number of long-standing questions, including the origin of the streamer material in the outer corona, the sources of the slow solar wind, and the mechanisms that regulate the interplanetary magnetic field strength. Title: Detection of coronal mass ejection associated shock waves in the outer corona Authors: Sheeley, N. R.; Hakala, W. N.; Wang, Y. -M. Bibcode: 2000JGR...105.5081S Altcode: White light coronal images from the Large-Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) spacecraft show disturbances propagating away from high-speed coronal mass ejections (CMEs). The disturbances are faintly visible ahead of the ejected material at the noses of the CMEs but are strongly visible along the flanks and rear ends, where they produce kinks in the streamers and other raylike features that extend in all directions from the Sun at this phase of the sunspot cycle. The kinks decelerate as they move radially outward along the rays, apparently indicating the slowing of the entire wave front as it passes by. For a fast CME seen head on (or tail on) the deceleration occurs at virtually all position angles around the occulting disk. However, for a CME seen obliquely the speed varies strongly with position angle, being fast and uniform near the nose but slower and decelerating at the sides and rear where the deflected rays are more inclined from the sky plane and farther from the Sun. The initial speeds (~800-1400 km/s) are faster than the nominal MHD speed (~600 km/s) at these heights, implying that these disturbances are shock waves, made visible like ``amber waves of grain'' [Bates, 1895] in the field of coronal rays around the Sun. Title: Understanding the evolution of the Sun's open magnetic flux Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Lean, J. Bibcode: 2000GeoRL..27..621W Altcode: The large-scale magnetic field of the Sun, including the open flux that extends into the interplanetary medium, originates in active regions but is redistributed over the photosphere by differential rotation, supergranular convection, and poleward meridional flow. We use simulations to clarify the role of the surface transport processes in the evolution of the total open flux, Φopen, which determines the strength of the radial interplanetary field component. Representing the initial photospheric field configuration by one or more bipolar magnetic regions (BMRs), we show that Φopen varies approximately as the net dipole strength, determined by vectorially summing the dipole moments of the individual BMRs. As meridional flow carries the BMR flux to higher latitudes, the equatorial dipole component is annihilated on a timescale ∼1 yr by the combined effect of rotational shearing and supergranular diffusion. The remaining flux becomes concentrated around the poles, and Φopen approaches a limiting value that depends on the axisymmetric dipole strength of the original active regions. We discuss the implications of these results for the solar cycle evolution of Φopen. Title: The long-term variation of the Sun's open magnetic flux Authors: Wang, Y. -M.; Lean, J.; Sheeley, N. R., Jr. Bibcode: 2000GeoRL..27..505W Altcode: The interplanetary magnetic field (IMF) has its origin in open magnetic regions of the Sun (coronal holes). The location of these regions and their total open flux Φopen can be inferred from current-free extrapolations of the observed photospheric field. We derive the long-term variation of Φopen during 1971-1998 and discuss its causes. Near sunspot minimum, the open flux originates mainly from the large polar coronal holes, whereas at sunspot maximum it is rooted in small, lower-latitude holes characterized by very high field strengths; the total amount of open flux thus remains roughly constant between sunspot minimum and maximum. Through most of the cycle, the variation of Φopen closely follows that of the Sun's total dipole strength, showing much less dependence on the total photospheric flux or the sunspot number. However, episodic increases in large-scale sunspot activity lead to strengthenings of the equatorial dipole component, and hence to enhancements in Φopen and the IMF strength lasting typically ∼1 yr. Title: Evolution of coronal streamer structure during the rising phase of solar cycle 23 Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Rich, N. B. Bibcode: 2000GeoRL..27..149W Altcode: White-light images of the outer corona recorded with the Large Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) show a rapid widening of the streamer belt during 1998 and early 1999. The observed streamer structure and its evolution from rotation to rotation are reproduced with a model in which the Thomson-scattering electrons are concentrated within a narrow layer centered around the heliospheric current sheet. The latitudinal spreading of the streamer belt is shown to be a consequence of the increased rate of magnetic flux emergence in the sunspot latitudes, which led to a weakening of the Sun’s axisymmetric dipole moment, to a rapid growth in the nonaxisymmetric components of the coronal field, and hence to a strong tilting and warping of the plasma/current sheet. Title: Continuous tracking of coronal outflows: Two kinds of coronal mass ejections Authors: Sheeley, N. R.; Walters, J. H.; Wang, Y. -M.; Howard, R. A. Bibcode: 1999JGR...10424739S Altcode: We have developed a new technique for tracking white-light coronal intensity features and have used this technique to construct continuous height/time maps of coronal ejecta as they move outward through the 2-30Rs field of view of the Large-Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) spacecraft. Displayed as gray-scale images, these height/time maps provide continuous histories of the motions along selected radial paths in the corona and reveal a variety of accelerating and decelerating features, including two principal types of coronal mass ejections (CMEs): (1) Gradual CMEs, apparently formed when prominences and their cavities rise up from below coronal streamers: When seen broadside, these events acquire balloon-like shapes containing central cores, and their leading edges accelerate gradually to speeds in the range 400-600 km/s before leaving the 2-30Rs field of view. The cores fall behind with speeds in the range 300-400 km/s. Seen along the line of sight, these events appear as smooth halos around the occulting disk, consistent with head-on views of optically thin bubbles stretched out from the Sun. At the relatively larger radial distances seen from this ``head-on'' perspective, gradually accelerating CMEs fade out sooner and seem to reach a constant speed more quickly than when seen broadside. Some suitably directed gradual CMEs are associated with interplanetary shocks and geomagnetic storms. (2) Impulsive CMEs, often associated with flares and Moreton waves on the visible disk: When seen broadside, these CMEs move uniformly across the 2-30Rs field of view with speeds typically in excess of 750 km/s. At the relatively larger radial distances seen from a head-on perspective, impulsive events tend to have a more ragged structure than the gradual CMEs and show clear evidence of deceleration, sometimes reducing their speeds from 1000 to 500 km/s in 1 hour. Such decelerations are too large to represent ballistic motions in the Sun's gravitational field but might be caused by shock waves, sweeping up material far from the Sun. Title: Using LASCO observations to infer solar wind speed near the sun Authors: Sheeley, N. R. Bibcode: 1999AIPC..471...41S Altcode: 1999sowi.conf...41S No abstract at ADS Title: Coronagraph observations of inflows during high solar activity Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Cyr, O. C. St.; Simnett, G. M. Bibcode: 1999GeoRL..26.1203W Altcode: Since the start of the SOHO mission three years ago, the Large Angle Spectrometric Coronagraph (LASCO) has recorded numerous examples of small, faint features moving inward through the corona. The inflows are observed at heliocentric distances of 2-4 Rs and became increasingly common during 1998, as solar and coronal mass ejection (CME) activity increased. The inward-moving structures, which are most easily detected in running difference movies, often have a cusplike appearance and tend to leave a density depletion in their wake; the downward velocities range from less than 20 km s-1 to over 100 km s-1. The downflows are observed typically ∼1 day after the passage of a CME, and coexist side by side with continuing outflows of streamer material. We interpret these small-scale events as observational signatures of the gradual closing-down of magnetic flux dragged outward by CMEs or other transient outflows. Title: Streamer disconnection events observed with the LASCO coronagraph Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Rich, N. B.; Lamy, P. L. Bibcode: 1999GeoRL..26.1349W Altcode: We present Large Angle Spectrometric Coronagraph (LASCO) observations of two events that suggest magnetic disconnection in coronal streamers. During the 1-2 days preceding each event, successions of narrow looptops are seen rising slowly through the 2-6 RS field of view, forming a bright streamer stalk which continues to elongate with time. As the streamer becomes ever more constricted, it eventually severs at a heliocentric distance of ∼4 RS. The lower part of the stalk collapses back to form a cusplike structure extending to ∼3 RS, while the disconnected segment is observed as a kink or density enhancement that propagates outward with a speed of order 200 km s-1. We interpret these non-CME events as transient openings and closings of magnetic flux rooted at the boundaries of coronal holes. Title: The Increase in Mass of CMEs due to Propagation Authors: Howard, R. A.; Dere, K. P.; Sheeley, N. R., Jr.; Subramanian, P.; Vourlidas, A.; Wang, D. Bibcode: 1999AAS...19410102H Altcode: 1999BAAS...31..998H The question we would like to address is whether coronal mass ejections snowplow ambient material. Some of the CMEs observed by the LASCO coronagraph on SOHO have a clearly defined loop-like front, meaning that the trailing edge of the front can be clearly defined. We measure the mass in the front of the CME in this subclass. We find that for some of the events, the mass in the leading edge increases, implying that the CME is indeed "snowplowing" ambient material. If there is a significant increase in mass, then the CME frontal speed might decrease to conserve momentum. We estimate the amount of ambient material, using a model of coronal densities, and find that it is consistent with the mass increase. We can also estimate the height in the corona, below the occulting disk, from where the original material in the CME is released. These concepts as well as conditions for when the mass increases will be discussed. Title: Filament Eruptions near Emerging Bipoles Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1999ApJ...510L.157W Altcode: It has been suggested in previous studies that quiescent prominences and filaments erupt preferentially in the vicinity of emerging magnetic flux. We describe three such filament eruptions observed during 1998 with the Extreme-ultraviolet Imaging Telescope on the Solar and Heliospheric Observatory. Comparison with magnetograms and with potential field extrapolations suggests that the new bipole enables the eruption by diverting the flux overlying the filament sideways or to greater heights, allowing the filament to rise out of its channel. Because eruptions sometimes occur in the absence of any observable flux emergence, however, we conclude that new flux may act as a strong catalyst but is not a necessary condition for filament destabilization. Title: Scattering polarization in the chromosphere Authors: Keller, C. U.; Sheeley, N. R., Jr. Bibcode: 1999ASSL..243...17K Altcode: 1999sopo.conf...17K No abstract at ADS Title: Observations of Correlated White-Light and Extreme-Ultraviolet Jets from Polar Coronal Holes Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Socker, D. G.; Howard, R. A.; Brueckner, G. E.; Michels, D. J.; Moses, D.; St. Cyr, O. C.; Llebaria, A.; Delaboudinière, J. -P. Bibcode: 1998ApJ...508..899W Altcode: Time-lapse sequences of white-light images recorded with the Large Angle Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) frequently show long, narrow structures moving outward over the Sun's polar regions at high apparent speeds. By comparing the LASCO observations with Fe XII λ195 spectroheliograms made with the Extreme-ultraviolet Imaging Telescope (EIT) on SOHO between 1997 April and 1998 February, we have identified 27 correlated white-light and extreme-ultraviolet (EUV) jet events. In each case, the EUV jet was observed near the limb of the polar coronal hole 20-60 minutes before the corresponding white-light jet was registered in the coronagraph's 2-6 R⊙ field of view. The jets originate near flaring EUV bright points and are presumably triggered by field line reconnection between magnetic bipoles and neighboring unipolar flux. The leading edges of the white-light jets propagate outward at speeds of 400-1100 km s-1, whereas the bulk of their material travels at much lower velocities averaging around 250 km s-1 at heliocentric distances of 2.9-3.7 R⊙. These lower velocities may reflect the actual outflow speeds of the background polar wind. Title: Heliospheric magnetic field strength out to 66 AU: Voyager 1, 1978-1996 Authors: Burlaga, L. F.; Ness, N. F.; Wang, Y. -M.; Sheeley, N. R. Bibcode: 1998JGR...10323727B Altcode: We discuss Voyager 1 (V1) observations of the heliospheric magnetic field strength from 1978 through 1996. During this period the distance of V1 from the Sun increased from ~3 AU to 66 AU and its heliographic latitude increased from ~5°S to 33°N. The magnetic field strength profile observed by V1 is consistent with Parker's spiral field model when one considers (1) the solar cycle variation of the observed magnetic field strength at 1 AU, B1(t) (which is a measure of the source field strength) and (2) the latitudinal and solar cycle variations of the solar wind speed, V(t,θ). Both B1(t) and V(t,θ) make significant contributions to the variation of the magnetic field strength variations observed by V1. There is no evidence for a ``magnetic flux deficit'' increasing with distance from the Sun. There is a solar cycle variation of the magnetic field strength in the outer heliosphere, which will affect the modulation of cosmic rays. Title: Large-scale coronal heating by the small-scale magnetic field of the Sun Authors: Schrijver, C. J.; Title, A. M.; Harvey, K. L.; Sheeley, N. R.; Wang, Y. -M.; van den Oord, G. H. J.; Shine, R. A.; Tarbell, T. D.; Hurlburt, N. E. Bibcode: 1998Natur.394..152S Altcode: Magnetic fields play a crucial role in heating the outer atmospheres of the Sun and Sun-like stars, but the mechanisms by which magnetic energy in the photosphere is converted to thermal energy in the corona remain unclear. Observations show that magnetic fields emerge onto the solar surface as bipolar regions with a broad range of length scales. On large scales, the bipolar regions survive for months before dispersing diffusively. On the smaller scales, individual bipolar regions disappear within days but are continuously replenished by new small flux concentrations, resulting in a sustained state of mixed polarity. Here we determine the rate of emergence of these small bipolar regions and we argue that the frequent magnetic reconnections associated with these regions (an unavoidable consequence of continued flux replacement) will heat the solar atmosphere. The model that describes the details of these mixed-polarity regions is complementary to the traditional diffusion model for large-scale flux dispersal and a combination of the two should lead to a more complete understanding of the role of magnetic fields in stellar atmospheres. Title: Origin of Streamer Material in the Outer Corona Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Walters, J. H.; Brueckner, G. E.; Howard, R. A.; Michels, D. J.; Lamy, P. L.; Schwenn, R.; Simnett, G. M. Bibcode: 1998ApJ...498L.165W Altcode: We investigate the nature and origin of the outward-moving density inhomogeneities (``blobs'') detected previously with the Large Angle and Spectrometric Coronagraph on the Solar and Heliospheric Observatory. The blobs are concentrated around the thin plasma layer that surrounds the heliospheric current sheet and that constitutes the outer streamer belt; they represent only a small, fluctuating component of the total density within the plasma sheet. As noted before in Sheeley et al., blobs are characterized by low speeds and are continually emitted from the elongated tips of helmet streamers at 3-4 Rsolar from Sun center. We suggest that both the blobs and the plasma sheet itself represent closed-field material injected into the solar wind as a result of footpoint exchanges between the stretched helmet-streamer loops and neighboring open field lines. The plasma sheet is thus threaded by newly reconnected, open magnetic field lines, which lend the white-light streamer belt its filamentary appearance. Since in situ observations at 1 AU show that the slow wind (with speeds below 500 km s-1) spreads over an angular extent much greater than the <~3° width of the plasma sheet, we deduce that a major component of this wind must originate outside the helmet streamers (i.e., from just inside coronal holes). Title: White-Light Coronal Mass Ejections: A New Perspective from LASCO Authors: St. Cyr, O. C.; Howard, R. A.; Simnett, G. M.; Gurman, J. B.; Plunkett, S. P.; Sheeley, N. R.; Schwenn, R.; Koomen, M. J.; Brueckner, G. E.; Michels, D. J.; Andrews, M.; Biesecker, D. A.; Cook, J.; Dere, K. P.; Duffin, R.; Einfalt, E.; Korendyke, C. M.; Lamy, P. L.; Lewis, D.; Llebaria, A.; Lyons, M.; Moses, J. D.; Moulton, N. E.; Newmark, J.; Paswaters, S. E.; Podlipnik, B.; Rich, N.; Schenk, K. M.; Socker, D. G.; Stezelberger, S. T.; Tappin, S. J.; Thompson, B.; Wang, D. Bibcode: 1997ESASP.415..103S Altcode: 1997cpsh.conf..103S No abstract at ADS Title: The high-latitude solar wind near sunspot Maximum Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1997GeoRL..24.3141W Altcode: We use an empirical relation between solar wind speed and coronal flux-tube expansion to predict what Ulysses might have seen had it flown over the solar poles during 1989-1991 instead of 1994-1996. The wind speed patterns, derived from solar magnetograph data, show the following characteristics: (1) high-speed streams having recurrence rates of 28-29 days and originating from midlatitude extensions of the polar coronal holes dominate the rising phase of the sunspot cycle (1987-1989) (2) the persistent high-speed polar wind disappears and low-speed wind is found at all latitudes during 1989-1990 (3) very fast, episodic “polar jets” are generated as active region fields surge to the poles at the time of polar field reversal (1990-1991). The wind speed patterns that Ulysses encounters during its second polar orbit are expected to show the same general characteristics. Title: Solar Wind Stream Interactions and the Wind Speed-Expansion Factor Relationship. Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Phillips, J. L.; Goldstein, B. E. Bibcode: 1997ApJ...488L..51W Altcode: Previous studies have shown that the solar wind speed observed near Earth is inversely correlated with the divergence rate of magnetic flux tubes near the Sun. We test the global validity of this relationship by employing Ulysses wind speed measurements during 1990-1997 as well as inecliptic data for 1976-1997. When the correspondence between wind speeds and expansion factors is adjusted to yield optimal agreement with the high-latitude Ulysses measurements, the model matches the overall patterns of fast and slow wind near the ecliptic but predicts too much very fast wind there. We show how this discrepancy can be resolved by taking account of wind stream interactions, where we apply a crude algorithm based on the propagation times of neighboring wind parcels; the interactions reduce the amount of very fast wind at latitudes where slow wind is present. We also test and reject an alternative model in which the wind speed is assumed to be a function only of angular distance from the heliospheric neutral sheet. Title: Origin and Evolution of Coronal Streamer Structure During the 1996 Minimum Activity Phase Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Howard, R. A.; Kraemer, J. R.; Rich, N. B.; Andrews, M. D.; Brueckner, G. E.; Dere, K. P.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Moses, J. D.; Paswaters, S. E.; Socker, D. G.; Wang, D.; Lamy, P. L.; Llebaria, A.; Vibert, D.; Schwenn, R.; Simnett, G. M. Bibcode: 1997ApJ...485..875W Altcode: We employ coronal extrapolations of solar magnetograph data to interpret observations of the white-light streamer structure made with the LASCO coronagraph in 1996. The topological appearance of the streamer belt during the present minimum activity phase is well described by a model in which the Thomson-scattering electrons are concentrated around a single, warped current sheet encircling the Sun. Projection effects give rise to bright, jet-like structures or spikes whenever the current sheet is viewed edge-on multiple spikes are seen if the current sheet is sufficiently wavy. The extreme narrowness of these features in polarized images indicates that the scattering layer is at most a few degrees wide. We model the evolution of the streamer belt from 1996 April to 1996 September and show that the effect of photospheric activity on the streamer belt topology depends not just on the strength of the erupted magnetic flux, but also on its longitudinal phase relative to the background field. Using flux transport simulations, we also demonstrate how the streamer belt would evolve during a prolonged absence of activity. Title: The Green Line Corona and Its Relation to the Photospheric Magnetic Field Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Hawley, S. H.; Kraemer, J. R.; Brueckner, G. E.; Howard, R. A.; Korendyke, C. M.; Michels, D. J.; Moulton, N. E.; Socker, D. G.; Schwenn, R. Bibcode: 1997ApJ...485..419W Altcode: Images of the green line corona made with the LASCO C1 coronagraph on SOHO are analyzed by applying current-free extrapolations to the observed photospheric field. The Fe XIV λ5303 emission is shown to be closely related to the underlying photospheric field strength. By modeling the observed intensity patterns as a function of latitude and height above the solar limb, we derive an approximate scaling law of the form nfoot ~ <Bfoot>0.9, where nfoot is the density of the green line-emitting plasma and <Bfoot> is the average field strength at the footprints of the coronal loop. The observed high-latitude enhancements in the green line corona are attributed to the poleward concentration of the large-scale photospheric field. The strongest such enhancements occur where the high-latitude unipolar fields become reconnected to active region flux at lower latitudes; the global emission pattern rotates quasi-rigidly at the rate of the dominant active region complex. The validity of the current-free approximation is assessed by comparing the topology of the observed and simulated green line structures. Title: Measurements of Flow Speeds in the Corona Between 2 and 30 R⊙ Authors: Sheeley, N. R.; Wang, Y. -M.; Hawley, S. H.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Koomen, M. J.; Korendyke, C. M.; Michels, D. J.; Paswaters, S. E.; Socker, D. G.; St. Cyr, O. C.; Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; Simnett, G. M.; Plunkett, S.; Biesecker, D. A. Bibcode: 1997ApJ...484..472S Altcode: Time-lapse sequences of white-light images, obtained during sunspot minimum conditions in 1996 by the Large Angle Spectrometric Coronagraph on the Solar and Heliospheric Observatory, give the impression of a continuous outflow of material in the streamer belt, as if we were observing Thomson scattering from inhomogeneities in the solar wind. Pursuing this idea, we have tracked the birth and outflow of 50-100 of the most prominent moving coronal features and find that:

1. They originate about 3-4 R⊙ from Sun center as radially elongated structures above the cusps of helmet streamers. Their initial sizes are about 1 R⊙ in the radial direction and 0.1 R⊙ in the transverse direction.

2. They move radially outward, maintaining constant angular spans and increasing their lengths in rough accord with their speeds, which typically double from 150 km s-1 near 5 R⊙ to 300 km s-1 near 25 R⊙.

3. Their individual speed profiles v(r) cluster around a nearly parabolic path characterized by a constant acceleration of about 4 m s-2 through most of the 30 R⊙ field of view. This profile is consistent with an isothermal solar wind expansion at a temperature of about 1.1 MK and a sonic point near 5 R⊙.

Based on their relatively small initial sizes, low intensities, radial motions, slow but increasing speeds, and location in the streamer belt, we conclude that these moving features are passively tracing the outflow of the slow solar wind. Title: Association of Extreme-Ultraviolet Imaging Telescope (EIT) Polar Plumes with Mixed-Polarity Magnetic Network Authors: Wang, Y. -M.; Sheeley, N. R.; Dere, K. P.; Duffin, R. T.; Howard, R. A.; Michels, D. J.; Moses, J. D.; Harvey, J. W.; Branston, D. D.; Delaboudinière, J. -P.; Artzner, G. E.; Hochedez, J. F.; Defise, J. M.; Catura, R. C.; Lemen, J. R.; Gurman, J. B.; Neupert, W. M.; Newmark, J.; Thompson, B.; Maucherat, A.; Clette, F. Bibcode: 1997ApJ...484L..75W Altcode: SOHO EIT spectroheliograms showing the polar coronal holes during the present sunspot minimum are compared with National Solar Observatory (Kitt Peak) magnetograms taken in Fe I λ8688 and Ca II λ8542. The chromospheric λ8542 magnetograms, obtained on a routine, near-daily basis since 1996 June, reveal the Sun's strong polar fields with remarkable clarity. We find that the Fe IX λ171 polar plumes occur where minority-polarity flux is in contact with flux of the dominant polarity inside each polar hole. Moreover, the locations of ``plume haze'' coincide approximately with the patterns of brightened He II λ304 network within the coronal hole. The observations appear to be consistent with mechanisms of plume formation involving magnetic reconnection between unipolar flux concentrations and nearby bipoles. The fact that minority-polarity fields constitute only a small fraction of the total magnetic flux within the polar holes suggests that plumes are not the main source of the high-speed polar wind. Title: Using LASCO Observations to Infer Solar Wind Flow Near the Sun Authors: Sheeley, N. R., Jr.; Brueckner, G. E.; Dere, K. P.; Howard, R. A.; Korendyke, C. M.; Michels, D. J.; Socker, D. G.; Koomen, M. J.; Paswaters, S. E.; Wang, D.; Lamy, P. L.; Llebaria, A.; Schwenn, R.; St Cyr, O. C.; Simnett, G. M.; Plunkett, S.; Biesecker, D. A. Bibcode: 1997SPD....28.0301S Altcode: 1997BAAS...29..907S We have continued to track individual coronal features as they become detached from helmet streamers and move outward from the Sun. The composite speed profile for 50-100 features has a parabolic shape with a constant acceleration of about 4 m/s(2) over the 2-30 R field of view. This well-determined speed profile contrasts strongly with the nearly uniform scatterplot obtained for about 50 nominal coronal mass ejections (CMEs), and suggests that these detached bits of coronal ``debris'' are passively tracing the speed of the slow solar wind. We have also begun the more difficult task of tracking outflow along polar plumes and will summarize these results as of June 1997. Title: Richard Tousey 1908-1997 Authors: Koomen, M. J.; Hunter, W. R.; Sheeley, N. R. Bibcode: 1997CIBu..140....4K Altcode: No abstract at ADS Title: Near-Sun Magnetic Fields and the Solar Wind Authors: Sheeley, N. R., Jr.; Wang, Y. -M.; Phillips, J. L. Bibcode: 1997cwh..conf..459S Altcode: 2006mslp.conf..459S No abstract at ADS Title: Obituary: Robert B. Leighton, 1919-1997 Authors: Neugebauer, Gerry; Peck, Charles W.; Sheeley, Neil; Trimble, Virginia Bibcode: 1997BAAS...29.1477N Altcode: No abstract at ADS Title: Obituary: Richard Tousey, 1908-1997 Authors: Koomen, M. J.; Hunter, W. R.; Sheeley, N. R., Jr. Bibcode: 1997BAAS...29.1494K Altcode: No abstract at ADS Title: ULYSSES plasma parameters: latitudinal, radial, and temporal variations. Authors: Goldstein, B. E.; Neugebauer, M.; Phillips, J. L.; Bame, S.; Gosling, J. T.; McComas, D.; Wang, Y. -M.; Sheeley, N. R.; Suess, S. T. Bibcode: 1996A&A...316..296G Altcode: Observations by the Ulysses SWOOPS plasma experiment are used to investigate spatial and temporal gradients during the mission, with emphasis on more recent high latitude observations including the recent South Pole to North Pole passage during solar minimum. Compared to lower latitudes, the high latitude solar wind had higher average speed, proton temperature, and momentum flux, and lower number flux density. As the average momentum flux observed in the high speed wind was 21% greater than at the equator, during solar minimum the distance to the heliopause will be comparatively less in the solar equatorial plane than over the poles. The long term temporal gradients of momentum flux over the life of the mission are considerably larger than the latitudinal gradient observed by Ulysses during solar minimum. A modest North-South high latitude asymmetry is observed in the plasma parameters; the velocity is on the average 13km/s to 24km/s greater at Northern latitudes than at Southern, and temperature is also higher. The North-South temperature asymmetry is greater than can be explained by the North-South velocity difference and the dependence of solar wind temperature upon speed. The power law dependence of temperature on heliocentric distance, r, at high latitudes is in range r^-0.81^ to r^-1.03^, where r^-0.81^ is the Southern latitude result and r^-1.03^ the Northern. The parameter T/n^1/2^, where T is temperature and n is proton number density, can be better predicted from speed than can temperature alone. Comparison with calculations based on source models and magnetograph data indicate that the expansion of open coronal field lines close to the Sun was greater in the Southern hemisphere than in the Northern; this anticorrelation with the expansion factor is consistent with previous observational and theoretical work. Title: Elemental Abundance Variations in the Solar Atmosphere Authors: Sheeley, N. R., Jr. Bibcode: 1996ApJ...469..423S Altcode: Skylab solar images in the transition region lines of neon, magnesium, and calcium have been used to trace elemental abundance variations in sunspots and the quiet Sun. Sunspots are invariably accompanied by spikelike features, enriched in elements of low first ionization potential (FIP) such as magnesium and calcium, and extending outward from the penumbras. Material with the normal, unenriched, photospheric-like composition is sometimes seen over the umbra, but it is only seen in the presence of very bright chromospheric emission associated with flares or emerging flux. The salt-and-pepper fields of the quiet Sun give rise to small-scale structures, enhanced in the lines of both helium and neon, and having the "photospheric" composition. However, enrichments of low-Fl P elements are sometimes found at unipolar flux concentrations in coronal holes, and occasionally they have very large enrichment factors. These observations suggest that the composition depends on whether the plasma is coronal or not and that the fractionation process is somehow related to the production of coronal material. Title: The Magnetic Nature of Coronal Holes Authors: Wang, Yi-Ming; Hawley, Scott H.; Sheeley, Neil R., Jr. Bibcode: 1996Sci...271..464W Altcode: Solar wind streams originate from low-density, magnetically open regions of the sun's corona, known as coronal holes. The locations, areal sizes, rotation, and solar-cycle evolution of these regions can be reproduced and understood by applying simple extrapolation models to measurements of the photospheric magnetic field. The surprisingly rigid rotation displayed by many coronal holes suggests that field-line reconnection occurs continually in the corona, despite the high electrical conductivity of the coronal plasma. The magnetic field strengths and field-line divergence rates in coronal holes can be related empirically to the bulk speed and the mass and energy flux densities of the solar wind plasma. Such relations may help to illuminate the physical processes responsible for heating the corona and driving the solar wind. Title: Coronal Plumes and Their Relationship to Network Activity Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1995ApJ...452..457W Altcode: Using Skylab extreme-ultraviolet spectroheliograms, we address the question of what lies under a coronal plume. Plumes and their base areas, both inside polar coronal holes and within lower latitude holes near central meridian, are identified in the Mg IX λ368 emission line. While some (usually spike-shaped) plumes show a strongly enhanced Mg IX core, others (sheetlike in appearance) are characterized by a much more diffuse base which may extend over several supergranules. The base areas are found to contain collections of compact (although not always intense) Ne VII λ465 features, whose locations in turn generally coincide with enhancements in the He II λ304 network inside the coronal hole. Bright plumes always show intense network features within their base areas, but the converse does not hold: not every Ne VII or He II bright point has an associated Mg IX plume. By comparing the locations of plumelike Mg IX "haze" in a lower latitude hole with a simultaneous high-resolution magnetogram, we infer that coronal plumes occur near regions of mixed magnetic polarity. We suggest a mechanism for plume formation, whereby small bipoles within a coronal hole reconnect with unipolar flux concentrations located at network junctions. Title: Coronal flux-tube expansion and the polar wind Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Phillips, J. L. Bibcode: 1995AdSpR..16i.365W Altcode: 1995AdSpR..16..365W Empirical and theoretical studies indicate an inverse correlation between the areal expansion rate of magnetic flux tubes near the Sun and the solar wind speed far from the sun. This relationship is combined with solar magnetograph measurements to predict the wind speed structures at high latitudes, and the results are compared with observations now being carried out by Ulysses. Based on the evolution of the polar fields during previous sunspot cycles, we also discuss how the high-latitude wind is likely to evolve between 1994 and the next solar maximum. Our main predictions are as follows: (1) As the cycle declines, the fastest wind streams are expected to be centered at mid-latitudes (above the polar-hole extensions), not at the poles themselves. (2) The fastest wind at the poles is predicted to occur not at sunspot minimum, when the polar fields are strongest and large axisymmetric polar coronal holes are present, but just after sunspot maximum, when the polar fields undergo their polarity reversal. Title: Solar Implications of ULYSSES Interplanetary Field Measurements Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1995ApJ...447L.143W Altcode: Recent observations by the Ulysses magnetometer team have shown that the strength of the radial interplanetary field component, |Br| , is essentially independent of latitude, a result which implies that the heliospheric currents are confined entirely to thin sheets. Using such a current sheet model, we extrapolate the observed photospheric field to 1 AU and compare the predicted magnitude and sign of Br with spacecraft measurements during 1970--1993. Approximate agreement can be obtained if the solar magnetograph measurements in the Fe I lambda 5250 line are scaled upward by a latitude-dependent factor, similar to that derived by Ulrich from a study of magnetic saturation effects. The correction factor implies sharply peaked polar fields near sunspot minimum, with each polar coronal hole having a mean field strength of 10 G. Title: Comparing ULYSSES wind speed with coronal flux-tube expansion factor Authors: Sheeley, N. R., Jr.; Wang, Y. -M.; Phillips, J. L.; Bame, S. J.; Goldstein, B. E. Bibcode: 1995sowi.confR..63S Altcode: We have been comparing measurements of solar wind speed at the Ulysses spacecraft with coronal flux-tube expansion rates, derived from photospheric field measurements using a current-free coronal model. The large-scale patterns of derived speed have continued to reproduce the observed patterns from launch through south polar passage to the present 40S latitude of the spacecraft. The fastest non-transient wind speeds of approx. 860 km/s were encountered at midlatitudes en route to the south pole, rather than during polar passage when the peak speeds were approx. 820 km/s. Although this result is in qualitative agreement with the idea that the wind speed is controlled by the coronal flux-tube expansion rate, the 40 km/s difference is significantly smaller than the 100-150 km/s difference based on our in-ecliptic calibration. This paper will summarize our attempts to resolve this discrepancy and will show the observational status of our coronal/interplanetary comparison at the time of the meeting. Title: Identification of Low-Latitude Coronal Plumes in Extreme-Ultraviolet Spectroheliograms Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1995ApJ...446L..51W Altcode: Using Skylab extreme ultraviolet images of the solar disk, we have identified plumelike features inside low-latitude coronal holes undergoing limb passage. Like their polar counterparts, these diffuse Mg IX structures are located above enhancements in the weak neon and helium background emission within the coronal hole. We conclude that coronal plumes are not unique to the polar regions but may occur in open magnetic regions at any latitude. Title: Source regions of the solar wind Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1995sowi.conf...31W Altcode: Using Skylab XUV data, we examine some properties of the source regions of the solar wind. In particular, we discuss the physical nature of polar plumes and their relationship to the polar wind, the nature of the source regions of the slow solar wind, and the relationship between abundance anomalies (the FIP effect) determined from the Skylab data and the sources of fast and slow wind. Title: Observations of Elemental Abundance Variations in the Solar Atmosphere Authors: Sheeley, N. R. Bibcode: 1995SPD....26..610S Altcode: 1995BAAS...27Q.963S No abstract at ADS Title: A Volcanic Origin for High-FIP Material in the Solar Atmosphere Authors: Sheeley, N. R., Jr. Bibcode: 1995ApJ...440..884S Altcode: Photospheric magnetograms and Skylab images in the lines of Ne VI and Mg VI near 400 Å have been used to study the relation between magnetic field topology and solar composition. Although plasma with the neon-rich photospheric composition is rare in the corona, it always occurs where new flux is emerging. This suggests that the neon richness of the plasma reflects its recent photospheric origin, not its closed-loop magnetic topology as has been assumed in the past. Such a "volcanic" process would be consistent with our observations of sunspots, which have the Ne-rich composition when they lie next to a neutral line where flux is emerging, but have the Mg-rich composition when they are surrounded by a "buffer zone" of like-polarity flux. Title: The Rotation of Photospheric Magnetic Fields: A Random Walk Transport Model Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1994ApJ...430..399W Altcode: In an earlier study of solar differential rotation, we showed that the transport of magnetic flux across latitudes acts to establish quasi-stationary patterns, therby accounting for the observed rigid rotation of the large-scale photospheric field. In that paper, the effect of supergranular convection was represented by a continuum diffusion, limiting the applicability of the calculations to large spatial scales. Here we extend the model to scales comparable to that of the supergranulation itself by replacing the diffusive transport with a discrete random walk process. Rotation curves are derived by cross-correlating the simulated photospheric field maps for a variety of time lags and spatial resolutions. When the lag between maps is relatively short less than or approximately = 15 days), the midlatitude correlation functions show two distinct components: a broad feature associated with the large-scale unipolar patterns and a narrow feature originating from small magnetic structures encompossing from one to several supergranular cells. By fitting the broad component we obtain the rigid rotation profile of the patterns, whereas by fitting the narrow component, we recover the differential rate of the photospheric plasma itself. For time lags of 1 month or greater, only the broad feature associated with the long-lived patterns remains clearly identifiable in the simulations. Title: Ulysses at 50° south: constant immersion in the high-speed solar wind Authors: Phillips, J. L.; Balogh, A.; Bame, S. J.; Goldstein, B. E.; Gosling, J. T.; Hoeksema, J. T.; McComas, D. J.; Neugebauer, M.; Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 1994GeoRL..21.1105P Altcode: We present speed observations from the Ulysses solar wind plasma experiment through 50° south latitude. The pronounced speed modulation arising from solar rotation and the tilt of the heliomagnetic current sheet has nearly disappeared. Ulysses is now observing wind speeds in the 700 to 800 km s-1 range, with a magnetic polarity indicating an origin in the large south polar coronal hole. The strong compressions, rarefactions, and shock waves previously seen have weakened or disappeared. Occasional coronal mass ejections characterized by low plasma density caused by radial expansion have been observed. The coronal configuration was simple and stable in 1993, indicating that the observed solar wind changes were caused by increasing spacecraft latitude. Trends in prevailing speed with increasing latitude support previous findings. A decrease in peak speed southward of 40° latitude may indicate that the fastest solar wind comes from the equatorial extensions of the polar coronal holes. Title: Global evolution of interplanetary sector structure, coronal holes, and solar wind streams during 1976-1993: Stackplot displays based on solar magnetic observations Authors: Wang, Y. M.; Sheeley, N. R., Jr. Bibcode: 1994JGR....99.6597W Altcode: We use potential field calculations and solar magnetic observations during 1976-1993 to infer the evolution of interplanetary sector structure, coronal holes, and solar wind streams at heliographic latitudes ranging from 80°S to 80°N. The results are presented in the form of stackplots, which show long-lived patterns that rotate quasi-rigidly at rates determined by the photospheric distribution of nonaxisymmetric magnetic flux. The fastest wind streams and their coronal hole sources form slowly rotating patterns near the poles just after sunspot maximum but migrate to lower latitudes and tend to rotate at near-equatorial rates as sunspot activity declines. Title: Returning to the random walk Authors: Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 1994ASIC..433..379S Altcode: No abstract at ADS Title: Understanding the Rotation of Coronal Holes Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1993ApJ...414..916W Altcode: In an earlier study we found that the rotation of coronal holes could be understood on the basis of a nearly current-free coronal field, with the holes representing open magnetic regions. In this paper we illustrate the model by focusing on the case of CH1, the rigidly rotating boot-shaped hole observed by Skylab. We show that the interaction between the polar fields and the flux associated with active regions produces distortions in the coronal field configuration and thus in the polar-hole boundaries; these distortions corotate with the perturbing nonaxisymmetric flux. In the case of CH1, positive-polarity field lines in the northern hemisphere 'collided' with like-polarity field lines fanning out from a decaying active region complex located just below the equator, producing a midlatitude corridor of open field lines rotating at the rate of the active region complex. Sheared coronal holes result when nonaxisymmetric flux is present at high latitudes, or equivalently, when the photospheric neutral line extends to high latitudes. We demonstrate how a small active region, rotating at the local photospheric rate, can drift through a rigidly rotating hole like CH1. Finally, we discuss the role of field-line reconnection in maintaining a quasi-potential coronal configuration. Title: Coronal Flux-Tube Expansion and the Solar Wind Speed at Ulysses Authors: Sheeley, N. R., Jr.; Wang, Y. -M.; Bame, S. J.; Phillips, J. L.; Goldstein, B. E. Bibcode: 1993BAAS...25.1203S Altcode: No abstract at ADS Title: Flux Emergence and the Evolution of Large-Scale Photosphenc Field Patterns (Abstract) Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1993ASPC...46..487W Altcode: 1993mvfs.conf..487W; 1993IAUCo.141..487W No abstract at ADS Title: A New Determination of the Solar Rotation Rate Authors: Sheeley, N. R., Jr.; Wang, Y. -M.; Nash, A. G. Bibcode: 1992ApJ...401..378S Altcode: We use 'stackplot' displays to compare observations of the photospheric magnetic field during sunspot cycle 21 with simulations based on the flux-transport model. Adopting nominal rates of diffusion, differential rotation, and meridional flow, we obtain slanted patterns similar to those of the observed field, even when the sources of flux are assigned random longitudes in the model. At low latitudes, the slopes of the nearly vertical patterns of simulated field are sensitive to the rotation rate used in the calculation, and insensitive to the rates of diffusion and flow during much of the sunspot cycle. Good agreement between the observed and simulated patterns requires a synodic equatorial rotation period of 26.75 +/- 0.05 days. Title: Obituary: Ana Gomes Nash, 1957-1992 Authors: Sheeley, Neil R.; Wang, Yi-Ming Bibcode: 1992BAAS...24.1329S Altcode: No abstract at ADS Title: On Potential Field Models of the Solar Corona Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1992ApJ...392..310W Altcode: It is shown that the line-of-sight matching procedure involved in potential field models of the solar corona do not make good use of the available data because there is strong evidence that the magnetic field is nearly radial, and therefore nonpotential, at the photosphere. It is argued that the observed photospheric field should first be corrected for line-of-sight projection and then matched to the radial component of the potential field. It is shown that this procedure yields much stronger polar fields than the standard method and produces better agreement with high-latitude coronal holes and with white-light structures in the outer corona. The relationship of both methods to the observed inclination angles of polar plumes is also discussed. Title: The relationship between solar wind speed and the areal expansion factor Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1992sws..coll..125W Altcode: Empirical studies indicate that the solar wind speed at Earth is inversely correlated with the divergence rate of the coronal magnetic field. This result suggests that the mechanical energy flux at the coronal base (in the form of Alfven waves, for example) is roughly constant within open field regions. Title: The Flux-Transport Model and Its Implications Authors: Sheeley, N. R., Jr. Bibcode: 1992ASPC...27....1S Altcode: 1992socy.work....1S No abstract at ADS Title: Coronal holes and solar wind streams during the sunspot cycle Authors: Sheeley, N. R., Jr. Bibcode: 1992sws..coll..263S Altcode: Complementary synoptic observations of the Sun and interplanetary space have been obtained nearly continuously for more than two sunspot cycles and have led to new ideas about the origin of the solar wind. These observations show an inverse correlation between wind speed at Earth and magnetic flux tube expansion in the corona, with fast wind originating from slowly diverging tubes and vice versa. Although this result is consistent with the Skylab-era concept that fast wind originates from the center of a large isolated coronal hole, it implies that the wind may be even faster at the facing edges of like-polarity holes where the flux-tubes converge as they begin their outward extension. Thus, very fast wind ought to originate from the high-latitude edges of the circumpolar holes soon after sunspot maximum and from the mid-latitude necks of the polar-hole lobes during the declining phase of the cycle. The observed inverse correlation may be understood physically in terms of a model in which Alfven waves boost the wind to high speed provided that the wave energy flux is distributed approximately uniformly at the coronal base. Title: A New Solar Cycle Model Including Meridional Circulation Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Nash, A. G. Bibcode: 1991ApJ...383..431W Altcode: A kinematic model is presented for the solar cycle which includes not only the transport of magnetic flux by supergranular diffusion and a poleward bulk flow at the sun's surface, but also the effects of turbulent diffusion and an equatorward 'return flow' beneath the surface. As in the earlier models of Babcock and Leighton, the rotational shearing of a subsurface poloidal field generates toroidal flux that erupts at the surface in the form of bipolar magnetic regions. However, such eruptions do not result in any net loss of toroidal flux from the sun (as assumed by Babcock and Leighton); instead, the large-scale toroidal field is destroyed both by 'unwinding' as the local poloidal field reverses its polarity, and by diffusion as the toroidal flux is transported equatorward by the subsurface flow and merged with its opposite hemisphere counterpart. The inclusion of meridional circulation allows stable oscillations of the magnetic field, accompanied by the equatorward progression of flux eruptions, to be achieved even in the absence of a radial gradient in the angular velocity. An illustrative case in which a subsurface flow speed of order 1 m/s and subsurface diffusion rate of order 10 sq km/s yield 22-yr oscillations in qualitative agreement with observations. Title: Out-of-ecliptic tests of the inverse correlation between solar wind speed and coronal expansion factor Authors: Sheeley, N. R., Jr.; Swanson, E. T.; Wang, Y. -M. Bibcode: 1991JGR....9613861S Altcode: In this paper we address the question of whether out-of-ecliptic measurements satisfy the inverse correlation between wind speed at 1 AU and flux tube divergence in the corona, already found from measurements in the ecliptic. Using the in-ecliptic calibration, we derive out-of-ecliptic speeds from coronal expansion factors determined from global observations of photospheric field and their current-free coronal extension. These derived speeds are compared with speeds inferred from interplanetary scintillation measurements during 1972-1988 and with in situ speeds measured by the Pioneer 11 spacecraft at 16°N latitude during 1984-1988. These three sets of wind speed show the same overall variation with latitude and time during the sunspot cycle, with higher latitudes having more years of fast wind than lower latitudes and all latitudes having slow wind at sunspot maximum. Although some detailed discrepancies are also present, the overall agreement is comparable to that achieved in the ecliptic plane. Title: Magnetic Flux Transport and the Sun's Dipole Moment: New Twists to the Babcock-Leighton Model Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1991ApJ...375..761W Altcode: The mechanisms that give rise to the sun's large-scale poloidal magnetic field are explored in the framework of the Babcock-Leighton (BL) model. It is shown that there are in general two quite distinct contributions to the generation of the 'alpha effect': the first is associated with the axial tilts of the bipolar magnetic regions as they erupt at the surface, while the second arises through the interaction between diffusion and flow as the magnetic flux is dispersed over the surface. The general relationship between flux transport and the BL dynamo is discussed. Title: Polar Faculae: 1906--1990 Authors: Sheeley, N. R., Jr. Bibcode: 1991ApJ...374..386S Altcode: The numbers of faculae at the sun's poles have been estimated from white-light images obtained at the Mount Wilson Observatory during 1970-1990 and have been combined with previous measurements extending back to 1906 when the observations began. The combined measurements now span four complete 22 year cycles and show the following: (1) the numbers of north and south polar faculae were about 50 percent larger around sunspot minimum in 1986 than in 1976, but were still smaller than some of the very large numbers that occurred near sunspot minima in earlier cycles; (2) in 1974, the number of south polar faculae exhibited a short-lived increase which coincided with the arrival of a surge of trailing-polarity flux at the pole, suggesting that similar poleward surges may have been responsible for previously unexplained bursts of faculae such as the one that occurred at the south pole in 1959; and (3) the numbers of polar faculae have been highly correlated with the Wilcox Solar Observatory polar field strengths since these magnetic measurements began in 1976. Title: Why Fast Solar Wind Originates from Slowly Expanding Coronal Flux Tubes Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1991ApJ...372L..45W Altcode: Empirical studies indicate that the solar wind speed at earth is inversely correlated with the divergence rate of the coronal magnetic field. It is shown that this result is consistent with simple wind acceleration models involving Alfven waves, provided that the wave energy flux at the coronal base is taken to be roughly constant within open field regions. Title: Deriving Solar Wind Speed from Solar Magnetic Field Measurements Authors: Nash, A. G.; Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1991BAAS...23..821N Altcode: No abstract at ADS Title: Magnetic Field Configurations Associated with Fast Solar Wind Authors: Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 1991SoPh..131..165S Altcode: In this paper, we consider the implications of the observed inverse correlation between solar wind speed at Earth and the expansion rate of the Sun-Earth flux tube as it passes through the corona. We find that the coronal expansion rate depends critically on the large-scale photospheric field distribution around the footpoint of the flux tube, with the smallest expansions occurring in tubes that are rooted near a local minimum in the field. This suggests that the fastest wind streams originate from regions where large coronal holes are about to break apart and from the facing edges of adjacent like-polarity holes, whose field lines converge as they transit the corona. These ideas lead to the following predictions: Weak holes and fragmentary holes can be sources of very fast wind. Title: Photospheric and coronal magnetic fields Authors: Sheeley, N. R., Jr. Bibcode: 1991RvGeo..29S.925S Altcode: 1991RvGeS..29..925S; 1991RvGeo..29..925S Research on small-scale and large-scale photospheric and coronal magnetic fields during 1987-1990 is reviewed, focusing on observational studies. Particular attention is given to the new techniques, which include the correlation tracking of granules, the use of highly Zeeman-sensitive infrared spectral lines and multiple lines to deduce small-scale field strength, the application of long integration times coupled with good seeing conditions to study weak fields, and the use of high-resolution CCD detectors together with computer image-processing techniques to obtain images with unsurpassed spatial resolution. Synoptic observations of large-scale fields during the sunspot cycle are also discussed. Title: The solar activity cycle. Authors: Rabin, Douglas M.; DeVore, C. R.; Sheeley, Neil R., Jr.; Harvey, Karen L.; Hoeksema, J. T. Bibcode: 1991sia..book..781R Altcode: Study of the solar cycle is entering a new era dominated by objective, precise measurements of magnetic, velocity and radiation fields over the surface of the Sun. This review emphasizes observations of photospheric magnetic flux during cycle 21 (1976 - 1986) and how these measurements have been used to model the cyclic variability of the heliospheric magnetic field. Indices of solar activity are discussed in terms of their potential to figure in theoretical or empirical models. Other recent data, such as measurements of large-scale surface flows and information on the Sun's internal rotation from helioseismology, as well as the magnetic flux observations, are considered in the context of Babcock's phenomenological model of the solar cycle: can this model still serve? Is there anything better to replace it? Title: Magnetic Flux Transport and the Sunspot-Cycle Evolution of Coronal Holes and Their Wind Streams Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1990ApJ...365..372W Altcode: The relationships between magnetic flux transport from active regions and the formation and evolution of coronal holes are examined through numerical simulations. The model utilized is based on the assumption that coronal holes represent open field regions, and that the solar-wind speed at 1 AU is universely correlated with the divergence rate of the coronal field. The evolution of coronal holes and wind streams during 1980 - 1990 is discussed, along with flux transport and the evolution of open field regions, and focus is placed on declining, rising, and maximum phases. It is concluded that supergranular diffusion spreads active region flux over the solar surface and wipes out pockets of mixed polarity, thus creating unipolar areas containing open field lines; differential rotation spreads flux in longitude and it combines with diffusion to create axisymmetric polar holes from the original active-region fields; and meridional flow accelerates the decay of low-latitude holes by carrying flux to midlatitudes. Title: Latitudinal distribution of solar-wind speed from magnetic observations of the Sun Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Nash, A. G. Bibcode: 1990Natur.347..439W Altcode: Empirical studies suggest a close relationship between the solar-wind speed near the Earth and the magnetic structure of the solar corona. The correlation can be used to infer the latitudinal distribution of wind speed at different phases of the sunspot cycle, and to identify the sources of fast, high-latitude wind streams such as those that might be encountered by the Ulysses spacecraft on its journey toward the solar poles during 1992-1995. Title: Solar Wind Speed and Coronal Flux-Tube Expansion Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1990ApJ...355..726W Altcode: The hypothesis that the solar wind speed at 1 AU and the rate of magnetic flux-tube expansion in the corona are inversely correlated is shown to be consistent with observations extending over the last 22 years. This empirical relationship allows the daily wind speeds at earth to be predicted from a current-free extrapolation of the observed photospheric field into the corona. The narrow boundaries of high-speed wind streams are attributed to steep gradients in the flux-tube expansion rates at the edges of coronal holes. When a heliospheric current sheet is included in the model, it is found that the flux tubes near the hole axis, although diverging more slowly than those near the hole boundary in the corona, have undergone the greatest net expansion at 1 AU, an effect consistent with the low densities within high-speed streams. Title: Coronal Mass Ejections and the Injection Profiles of Solar Energetic Particle Events Authors: Kahler, S. W.; Reames, D. V.; Sheeley, N. R., Jr. Bibcode: 1990ICRC....5..183K Altcode: 1989ICRC....5..183K; 1990ICRC...21e.183K Previous studies using Skylab and Solwind coronagraph observations have shown that almost all E greater than 10 MeV solar energetic proton (SEP) events are associated with the occurrence of a coronal mass ejection (CME). These earlier studies did not address the relationship between the position of the associated CME and the timing of the injection of particles into the interplanetary medium. Ten cases are selected in which a SEP event observed with the GSFC detectors on the IMP 8 or ISEE 3 spacecraft was correlated to a CME well observed by the Solwind coronagraph. The height of the leading edge of the CME is compared with the particle injection profiles for several energy ranges using the solar release times for the particles. The derived injection profiles are found to be increasing and sometimes reaching maximum while the associated CMEs are at heights of 2-10 Ro. Title: Evolution of the Sun's Polar Fields during Sunspot Cycle 21: Poleward Surges and Long-Term Behavior Authors: Wang, Y. -M.; Nash, A. G.; Sheeley, N. R., Jr. Bibcode: 1989ApJ...347..529W Altcode: Longitudinally averaged observations of the photospheric field during 1976-1986 are analyzed using a flux transport model. The way in which source eruptions, supergranular diffusion, and meridional flow collaborate to produce strong, highly concentrated polar fields near sunspot minimum is clarified as follows: (1) widespread eruptions of individual bipolar magnetic regions, with their leading polarity flux equatorward of their trailing polarity flux, collectively establish a large-scale separation of polarities in latitude; (2) the low-latitude, leading polarity flux diffuses across the equator and merges with its opposite hemisphere counterpart; and (3) meridional flow carries the resulting surplus of trailing polarity flux to the poles, and concentrates it there against the spreading effect of diffusion. Episodic 'surges' of flux to the poles are induced by fluctuations in the source eruption rate. Simulations indicate that relatively weak, trailing polarity surges may occur even in a steady flow field. However, in order to account for the giant surges of alternating polarity and the resulting oscillations in the polar field strength observed during 1980-1982, both accelerated flow and enhanced eruption rates are required. Title: Two Eruptive Prominences and a CME on 1982FEB9 Authors: Wang, J. L.; Nelson, G. J.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Kawabata, K.; Ogawa, H. Bibcode: 1989AcApS...9..260W Altcode: 1989AcApS...9..265W No abstract at ADS Title: The Effect of Newly Erupting Flux on the Polar Coronal Holes Authors: Sheeley, N. R.; Wang, Y. -M.; Harvey, J. W. Bibcode: 1989SoPh..119..323S Altcode: He I 10830 Å images show that early in sunspot cycles 21 and 22, large bipolar magnetic regions strongly affected the boundaries of the nearby polar coronal holes. East of each eruption, the hole boundary immediately contracted poleward, leaving a band of enhanced helium network. West of the eruption, the boundary remained diffuse and gradually expanded equatorward into the leading, like-polarity part of the bipolar magnetic region. Comparisons between these observations and simulations based on a current-free coronal model suggest that: The Sun's polar magnetic fields are confined to relatively small caps of high average field strength, apparently by a poleward meridional flow. Title: Coronal Mass Ejections and Associated X-Ray Flare Durations Authors: Kahler, S. W.; Sheeley, N. R., Jr.; Liggett, M. Bibcode: 1989ApJ...344.1026K Altcode: It is found that 22 percent of a sample of M1 or greater impulsive soft X-ray flares were associated with coronal mass ejections (CMEs) observed in the Solwind coronagraph. These flares were more energetic than similar impulsive flares without CMEs, and the associated CMEs were narrow (5-40 deg) in angular width. A survey of all CMEs associated with M1 or greater X-ray flares reveals a good correlation between flare duration CME angular width. The H-alpha characteristics of impulsive, CME-associated flares suggest that they are not the dynamic or eruptive flares presumed to be associated with CMEs, but rather, are confined flares. The H-alpha flare locations are neither centered under the CME legs. The disparity in size scales between the CMEs and their associated flares leaves the basis of the correlation between CME width and X-ray flare duration unresolved. Title: Magnetic Flux Transport on the Sun Authors: Wang, Y. -M.; Nash, A. G.; Sheeley, N. R., Jr. Bibcode: 1989Sci...245..712W Altcode: Although most of the magnetic flux observed on the sun originates in the low-latitude sunspot belts, this flux is gradually dispersed over a much wider range of latitudes by supergranular convective motions and meridional circulation. Numerical simulations show how these transport processes interact over the 11-year sunspot cycle to produce a strong ``topknot'' polar field, whose existence near sunspot minimum is suggested by the observed strength of the interplanetary magnetic field and by the observed areal extent of polar coronal holes. The required rates of diffusion and flow are consistent with the decay rates of active regions and with the rotational properties of the large-scale solar magnetic field. Title: Average Properties of Bipolar Magnetic Regions during Sunspot CYCLE-21 Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1989SoPh..124...81W Altcode: We examine the statistical properties of some 2700 bipolar magnetic regions (BMRs) with magnetic fluxes ≥3 × 1020 Mx which erupted during 1976-1986. Empirical rules were used to estimate the fluxes visually from daily magnetograms obtained at the National Solar Observatory/Kitt Peak. Our analysis shows the following: (i) the average flux per BMR declined between 1977 and 1985; (ii) the average tilts of BMRs relative to the east-west line increase toward higher latitudes; (iii) weaker BMRs had larger root-mean-square tilt angles than stronger BMRs at all latitudes; (iv) over the interval 1976-1986, BMRs with their leading poles equatorward of their trailing poles contributed a total of 4 times as much flux as BMRs with `inverted' tilts, but the relative amount of flux contributed by BMRs with inverted or zero tilts increased as the sunspot cycle progressed; (v) only 4% of BMRs had `reversed' east-west polarity orientations; (vi) although the northern hemisphere produced far more flux during the rising phase of the sunspot cycle, the southern hemisphere largely compensated for this imbalance during the declining phase; (vii) southern-hemisphere BMRs erupted at systematically higher latitudes than northern-hemisphere ones through most of sunspot cycle 21. Title: Implications of a Strongly Peaked Polar Magnetic Field Authors: Sheeley, N. R., Jr.; Wang, Y. -M.; DeVore, C. R. Bibcode: 1989SoPh..124....1S Altcode: Using the flux-transport equation in the absence of sources, we study the relation between a highly peaked polar magnetic field and the poleward meridional flow that concentrates it. If the maximum flow speed νm greatly exceeds the effective diffusion speed κ/R, then the field has a quasi-equilibrium configuration in which the poleward convection of flux via meridional flow approximately balances the equatorward spreading via supergranular diffusion. In this case, the flow speed ν(θ) and the magnetic field B(θ) are related by the steady-state approximation ν(θ) ≃ (κ/R)B'(θ)/B(θ) over a wide range of colatitudes θ from the poles to midlatitudes. In particular, a general flow profile of the form sinpθ cosqθ which peaks near the equator (q ≪ p) will correspond to a cosnθ magnetic field at high latitudes only if p = 1 and νm = n κ/R. Recent measurements of n ∼ 8 and κ ∼ 600 km2 s−1 would then give νm ∼ 7 m s−1. Title: The Evolution of the Sun's Polar Magnetic Field Authors: Sheeley, N. R., Jr.; Wang, Y. -M.; Nash, A. G. Bibcode: 1989BAAS...21..827S Altcode: No abstract at ADS Title: Average Magnetic Properties of Active Regions during Sunspot Cycle 21 Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1989BAAS...21Q.827W Altcode: No abstract at ADS Title: Giant solar arches and coronal mass ejections in November 1980 Authors: Svestka, Zdenek F.; Jackson, Bernard V.; Howard, Russell A.; Sheeley, Neil R., Jr. Bibcode: 1989SoPh..122..131S Altcode: Using data from the SOLWIND coronagraph and photometers aboard HELIOS-A we examine coronal mass ejections from an active region which produced a series of giant post-flare coronal arches. HXIS X-ray observations reveal that in several cases underlying flares did not disrupt these arch structures, but simply revived them, enhancing their temperature, density and brightness. Thus we are curious to know how these quasi-stationary X-ray structures could survive in the corona in spite of recurrent appearances of powerful dynamic flares below them. We have found reliable evidence that two dynamic flares which clearly revived the preexisting giant arch were not associated with any mass ejection. After two other flares, which were associated with mass ejections, the arch might have been newly formed when the ejection was over. In one of these cases, however, the arch had typical characteristics of a revived structure so that it is likely that it survived a powerful mass ejection nearby. In a magnetic configuration of the arch which results from potential-field modelling (Figure 1(b)) such a survival seems possible. Title: Coronal mass ejections and coronal structures. Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.; Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing, R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos, P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Stewart, R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T. Bibcode: 1989epos.conf..493H Altcode: The work of this team was concerned with modelling of post-flare arches, the reconnection theory of flares, the slow variation of coronal structure, and the coronal and interplanetary detection, evolution, and consequences of mass ejections. Title: The solar origin of long-term variations of the interplanetary magnetic field strength Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1988JGR....9311227W Altcode: Spacecraft measurements over the past two sunspot cycles have shown that the average strength of the interplanetary magnetic field (IMF) undergoes surprisingly modest long-term variation, unlike the total magnetic flux observed on the Sun. Our attempt to model the IMF during sunspot cycle 21, based on a current-free extrapolation of the observed photospheric field out to a fixed source surface where the field lines become radial, yields calculated IMF intensities which vary by an order of magnitude and which are far too low near sunspot minimum. We obtain much better agreement with a model containing both heliospheric sheet currents, which deflect polar flux toward the ecliptic, and volume currents, which maintain a residual latitudinal gradient in the IMF intensity. In order to match the observed IMF intensity levels, however, the measured photospheric fields had to be scaled up by approximately a factor of 2. Our composite model has the following main consequences: (1) The source of the radial component of the IMF may be represented to a first approximation by the dipole component of the photospheric field. (2) The radial IMF intensity is strongest in the direction of the dipole axis, which is aligned with the Sun's rotation axis near sunspot minimum but tilts toward the ecliptic near sunspot maximum. (3) The average strength of the photospheric field above latitude 55° is of order 10 G around sunspot minimum. Title: Mechanisms for the Rigid Rotation of Coronal Holes Authors: Nash, A. G.; Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 1988SoPh..117..359N Altcode: We show that the rotation of coronal holes can be understood in terms of a current-free model of the coronal magnetic field, in which holes are the footpoint locations of open field lines. The coronal field is determined as a function of time by matching its radial component to the photospheric flux distribution, whose evolution is simulated including differential rotation, supergranular diffusion, and meridional flow. We find that ongoing field-line reconnection allows the holes to rotate quasi-rigidly with their outer-coronal extensions, until their boundaries become constrained by the neutral line of the photospheric field as it winds up to form stripes of alternating magnetic polarity. This wind-up may be significantly retarded by a strong axisymmetric field component which forces the neutral line to low latitudes; it is also gradually halted by the cross-latitudinal transport of flux via supergranular diffusion and a poleward bulk flow. We conclude that a strong axisymmetric field component is responsible for the prolonged rigid rotation of large meridional holes during the declining phase of the sunspot cycle, but that diffusion and flow determine the less rigid rotation observed near sunspot maximum, when the holes corotate with their confining polarity stripes. Title: The Quasi-rigid Rotation of Coronal Magnetic Fields Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Nash, A. G.; Shampine, L. R. Bibcode: 1988ApJ...327..427W Altcode: Assuming that the coronal magnetic field can be approximated by a current-free extension of the photospheric field, the authors use spherical harmonic analysis and numerical simulations to study its rotational properties. In the outer corona, they find that the rotation rate is determined by three principal factors: 1. "Coronal filtering". 2. Global averages of the photospheric rotation rate. 3. Ongoing source eruptions. These principles allow to understand the observationally inferred rotational properties of the outer coronal field. The overall rigidity of the rotation profile reflects the tendency for the photosphere's non-axisymmetric flux to be concentrated toward lower latitudes, where the rotational shear is small; increased curvature and asymmetry occur during the rising phase of the sunspot cycle because of the presence of higher latitude flux. The coronal rotation rate shows a progressive acceleration due to the equatorward migration of sunspots. Title: A Model for Long-Term Variation of Interplanetary Magnetic Field-Strenght Authors: Wang, Y. -M.; Sheeley, N. R., Jr. Bibcode: 1988BAAS...20..705W Altcode: No abstract at ADS Title: Two eruptive prominences and a CME on February 9, 1982. Authors: Wang, J. L.; Nelson, G. J.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Kawabata, K.; Ogawa, H. Bibcode: 1988sscd.conf..547W Altcode: Two H-alpha eruptive prominences located at N10W90 and S14W90, respectively, were observed simultaneously on 9 February 1982. A CME corresponding to the northern one was observed by the satellite P78-1. No CME was seen for the much larger southern prominence which was associated with an intense radio burst. A comparison of the two eruptive prominences shows that the shape of a eruptive prominence and its change with time could be an important factor in its association with a CME. Title: Energetic interpanetary shocks, radio emission, and coronal mass ejections Authors: Cane, H. V.; Sheeley, N. R., Jr.; Howard, R. A. Bibcode: 1987JGR....92.9869C Altcode: The interplanetary shocks which generate detectable low-frequency (<1 MHz) radio emission, represent as a group, the most energetic shocks produced by the sun. For all interplanetary (IP) shocks which generated so-called IP type II events, we find when observations were available, that the associated solar events involved fast (>500 km/s) coronal mass ejections (CMEs). In comparison with the set of all CMEs detected by the Solwind coronagraph the CMEs associated with IP type II events are the most massive and energetic. The majority (>50%) belong to the structural classes described by the Solwind researchers as ``curved front'' or ``halo.'' Evidence presented suggest that these are the same class viewed from a different persective. Our results are consistent with there being a close relationship between interplanetary shocks and fast CMEs. Title: Sunspot - Cycle Variations of the Interplanetary Field Strength: Implications for Coronal Models Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; DeVore, C. R. Bibcode: 1987BAAS...19.1133W Altcode: No abstract at ADS Title: A Mechanism for the Rigid Rotation of Coronal Holes Authors: Nash, A. G.; Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 1987BAAS...19.1133N Altcode: No abstract at ADS Title: Solar activity and heliosphere-wide cosmic ray modulation in mid-1982 Authors: Cliver, E. W.; Mihalov, J. D.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Schwenn, R. Bibcode: 1987JGR....92.8487C Altcode: A major episode of flare activity in June and July 1982 was accompanied by a pair of heliosphere-wide cosmic ray modulation events. In each case, a large Forbush decrease (FD) at earth was followed in turn by apparently related decreases at Pioneer 11 (P11) and Pioneer 10 (P10). The Pioneer spacecraft were separated by ~155° in ecliptic longitude. We reviewed white light coronagraph and near-sun (<=1 AU) satellite data to identify plausible solar origins of these modulation events. The first widespread intensity decrease (FD 1) can be attributed to the combined effects of a backside flare on June 3 from solar active region 18382/18383, located 23° in ecliptic longitude from Pioneer 10, and a visible disk flare from 18405 on June 6, when this region was 9° from Pioneer 11. The second widespread modulation event during this period (FD 2) may be linked to flares from active region 18474 on July 12 and 22. The July 12 flare was located 34° in azimuth from Pioneer 11, and the July 22 flare was 24° from Pioneer 10. Since even fast shocks would take ~1 month to propagate to Pioneer 11 (12 AU) and ~2 months to reach Pioneer 10 (28 AU) in mid-1982, these ``one-to-one'' associations must be regarded with caution. The processes of entrainment and coalescence can cause a given traveling interplanetary disturbance to lose its identify enroute to the outer heliosphere. The fact that we were able to identify plausible solar flare candidates for each of the four Forbushlike decreases observed at the Pioneer satellites (two each at P10 and P11), however, removes the need to invoke a chock from a single flare as the sole cause of either FD 1 (at both P10 and P11) or FD 2. Such single-flare scenarios have recently been suggested by several investigators to account for the widespread intensity decreases in mid-1982. Instead, the heliosphere-wide modulation during this period appears to result primarily from a sustained episode of powerful flares from a relatively narrow range of active solar longitude.

A significant fraction (1/2 to 3/4) of the major coronal mass ejections (CMEs) and near-sun shocks observed during June and July 1982 originated in flares occurring in a 45° band of Carrington longitude. Because of solar rotation these flares occur over the full range of ecliptic longitude and can generate an outward propagating shell of CMEs and shocks that encompasses the sun to produce the observed azimuthal symmetry in the cosmic ray modulation. The prolonged high-speed wind stream at P10 in the second half of 1982 may have resulted, at least in part, from the coalescence of a series of fast transient streams directed toward that distant spacecraft into an extended compound stream. Title: The Origin of Rigidly Rotating Magnetic Field Patterns on the Sun Authors: Sheeley, N. R., Jr.; Nash, A. G.; Wang, Y. -M. Bibcode: 1987ApJ...319..481S Altcode: Using analytical calculations and numerical simulations, it is shown that a meridional component of magnetic-flux transport will offset the shearing effect of differential rotation and give rise to rigidly rotating patterns of large-scale magnetic field. The nonaxisymmetric field attains a striped polarity pattern which rotates rigidly like a barber pole while its individual small-scale flux elements rotate at the differential rate of the latitudes they are crossing. On the sun, the meridional transport is provided by supergranular diffusion possibly assisted by a small poleward flow. New sources of flux retard this process and exclude the rigid rotation from the sunspot belts until well into the declining phase of the sunspot cycle. This mechanism accounts for a number of heretofore unexplained phenomena including the tendency for coronal holes to rotate rigidly during the declining phase of the sunspot cycle. Title: The Origin of Rigidly Rotating Solar Magnetic Field Patterns Authors: Nash, A. G.; Sheeley, N. R., Jr.; Wang, Y. -M. Bibcode: 1987BAAS...19..938N Altcode: No abstract at ADS Title: Rotation of Coronal Holes during Sunspot Cycle 21 Authors: Harvey, J.; Sheeley, N. R., Jr. Bibcode: 1987BAAS...19Q.935H Altcode: No abstract at ADS Title: The Quasi-Rigid Rotation of Coronal Magnetic Fields Authors: Wang, Y. -M.; Sheeley, N. R., Jr.; Nash, A. G.; Shampine, L. R. Bibcode: 1987BAAS...19..939W Altcode: No abstract at ADS Title: Simulations of the Sun's Polar Magnetic Fields during Sunspot CYCLE-21 Authors: DeVore, C. Richard; Sheeley, Neil R., Jr. Bibcode: 1987SoPh..108...47D Altcode: Regarding new bipolar magnetic regions as sources of flux, we have simulated the evolution of the radial component of the solar photospheric magnetic field during 1976-1984 and derived the corresponding evolution of the line-of-sight polar fields as seen from Earth. The observed timing and strength of the polar-field reversal during cycle 21 can be accounted for by supergranular diffusion alone, for a diffusion coefficient of 800 km2 s-1. For an assumed 300 km2 s-1 rate of diffusion, on the other hand, a poleward meridional flow with a moderately broad profile and a peak speed of 10 m s-1 reached at about 5° latitude is required to obtain agreement between the simulated and observed fields. Such a flow accelerates the transport of following-polarity flux to the polar caps, but also inhibits the diffusion of leading-polarity flux across the equator. For flows faster than about 10 m s-1 the latter effect dominates, and the simulated polar fields reverse increasingly later and more weakly than the observed fields. Title: Interpreting Coronal Evolution in Terms of the Eruption and Transport of Photospheric Magnetic Fields Authors: Sheeley, N. R., Jr.; Wang, Y. -M.; Nash, A. G.; Shampine, L. R. Bibcode: 1987sowi.conf..322S Altcode: No abstract at ADS Title: The Correlation of CME Angular Sizes and Soft X-Ray Time Scales of Solar Eruptive Events Authors: Kahler, S. W.; Sheeley, N. R., Jr.; Howard, R. A. Bibcode: 1987sowi.conf..232K Altcode: No abstract at ADS Title: Solar Energetic Proton Events and Coronal Mass Ejections Near Solar Minimum Authors: Kahler, S. W.; Cliver, E. W.; Cane, H. V.; McGuire, R. E.; Reames, D. V.; Sheeley, N. R., Jr.; Howard, R. A. Bibcode: 1987ICRC....3..121K Altcode: 1987ICRC...20c.121K; 1987ICRC....3..121C No abstract at ADS Title: Interplanetary Effects of Coronal Mass Ejections Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.; Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing, R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos, P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward, R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T. Bibcode: 1986epos.conf.6.52H Altcode: 1986epos.confF..52H No abstract at ADS Title: Interplanetary shocks preceded by solar filament eruptions Authors: Cane, H. V.; Kahler, S. W.; Sheeley, N. R., Jr. Bibcode: 1986JGR....9113321C Altcode: We discuss the solar and interplanetary characteristics of six interplanetary shock and energetic particle events associated with the eruptions of solar filaments lying outside active regions. The events are characterized by the familiar double-ribbon Hα brightenings observed with large flares, but only very weak soft X ray and microwave bursts. Both impulsive phases and metric type II bursts are absent in all six events. The energetic particles observed near the earth appear to be accelerated predominantly in the interplanetary shocks. The interplanetary shock speeds are lower and the longitudinal extents considerably less than those of flare-associated shocks. Three of the events were associated with unusual enhancements of singly ionized helium in the solar wind following the shocks. These enhancements appear to be direct detections of the cool filament material expelled from the corona. We suggest that these events are part of a spectrum of solar eruptive events which include both weaker events and large flares. Despite their unimpressive and unreported solar signatures, the quiescent filament eruptions can result in substantial space and geophysical disturbances. Title: Initiations of Coronal Mass Ejections Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.; Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing, R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos, P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward, R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T. Bibcode: 1986epos.conf.6.27H Altcode: 1986epos.confF..27H No abstract at ADS Title: The Slowly Varying Corona Near Solar Activity Maximum Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.; Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing, R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos, P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward, R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T. Bibcode: 1986epos.conf.6.57H Altcode: 1986epos.confF..57H No abstract at ADS Title: Modelling of Coronal Mass Ejections and POST Flare Arches Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.; Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing, R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos, P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Steward, R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T. Bibcode: 1986epos.conf6.366H Altcode: 1986epos.confF.366H No abstract at ADS Title: Simulations of the Gross Solar Magnetic Field during SUNSPOT-CYCLE-21 Authors: Sheeley, Neil R., Jr.; DeVore, C. Richard; Shampine, Lauree R. Bibcode: 1986SoPh..106..251S Altcode: Regarding new bipolar magnetic regions as sources of flux, we have simulated the evolution of the radial component of the solar photospheric magnetic field during 1976-1984 with a spatial resolution of about 34 000 km, and have derived the corresponding evolution of its absolute value averaged over the visible disk. For nominal values of the transport parameters, this simulated gross field is in close, though imperfect, agreement with the observed gross field and its associated indices of solar activity. By analyzing the response of the simulated gross field to variations in the transport parameters and the source properties, we find that the simulated field originates in newly erupted bipolar regions. The lifetimes of these regions are almost always less than 3 mo. Consequently, the strength of the simulated gross field is a measure of the current level of solar activity, and any recurrent patterns with lifetimes in excess of 6 mo must reflect the continuing eruption of new flux at `active longitudes' rather than the persistence of old flux in long-lived magnetic structures. Title: Solar Gradual Hard X-Ray Bursts and Associated Phenomena Authors: Cliver, E. W.; Dennis, B. R.; Kiplinger, A. L.; Kane, S. R.; Neidig, D. F.; Sheeley, N. R., Jr.; Koomen, M. J. Bibcode: 1986ApJ...305..920C Altcode: White-light coronagraph, H-alpha and radio data are presented as well as hard X-ray data for a sample of 10 gradual hard X-ray bursts (GHBs) in an attempt to better understand the nature of these events. It is found that: (1) the hard X-ray photon energy spectrum began to harden near the onset of the GHBs and continued in this fashion during the decay phase; (2) a coronal mass ejection (CME) occurred in association with at least nine of the GHBs; (3) the GHBs occurred in the late phase of major flares; (4) the centimeter wavelength bursts associated with the GHBs had relatively low frequency spectral maxima, and in relation to the observed hard X-ray emission, they were microwave-rich; (5) the associated decimetric bursts showed significant intensity variations on time scales ranging from 0.1 to approximately greater than 1 minute; and (6) the GHBs were most strongly associated with type IV events. It is concluded that the acceleration and trapping of radiating electrons occurs in the postflare loop systems following CMEs. Title: Comet 1983 XX (Solwind 6) Authors: Howard, R.; Koomen, M.; Michels, D.; Sheeley, N.; Marsden, B. G. Bibcode: 1986IAUC.4229....1H Altcode: R. Howard, M. Koomen, D. Michels and N. Sheeley, Naval Research Laboratory, report identification of another comet in the SOLWIND coronagraph data. The apparent heliocentric separation F (solar radii) and position angle O (counted from the solar north pole) have been converted to R.A. and Decl. by the undersigned. On the sixth data frame the coma was behind the occulting disk. 1983 UT F O R.A. (1950.0) Decl. Sept. 24.863 8.1 230.5 11 54.4 - 0 50 24.870 7.8 230.4 11 54.8 - 0 49 24.878 7.6 231.2 11 55.0 - 0 47 24.885 7.3 230.6 11 55.3 - 0 47 24.892 7.2 230.5 11 55.5 - 0 47 25.062 < 2.5 231.8 (12 00.9 - 0 32) Preliminary examination of the raw data suggests that SOLWIND 6 was brighter than SOLWIND 2-5 (but certainly not SOLWIND 1). The tail was still quite bright on Sept. 25.08 and present but fainter on Sept. 25.14. Careful scrutiny of subsequent data reveals no trace of the comet reappearing from behind the occulted area. The line of sight was clearly very nearly in the comet's orbital plane. Computations by the undersigned suggest that the comet was very probably a member of the Kreutz group, a representative set of orbital elements being as follows: T = 1983 Sept. 25.19 ET, Peri. = 78.39, Node = 357.94, Incl. = 143.95 (equinox 1950.0), q = 0.0076 AU. Title: Properties of Metre-Wavelength Solar Bursts Associated with Coronal Mass Ejections Authors: Robinson, R. D.; Stewart, R. T.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, J.; Michels, D. J. Bibcode: 1986SoPh..105..149R Altcode: An investigation is made to determine the relationship between a coronal mass ejection (CME) and the characteristics of associated metre-wave activity. It is found that (1) the CME width and leading edge velocity can be highly influential in determining the intensity, spectral complexity and frequency coverage of both type II and continuum bursts; (2) the presence of a CME is possibly a necessary condition for the production of a metric continuum event and (3) metric continuum bursts as well as intense, complex type II events are preferentially associated with strong, long lasting soft X-ray events. Title: The Origin of the 28-DAY to 29-DAY Recurrent Patterns of the Solar Magnetic Field Authors: Sheeley, N. R., Jr.; DeVore, C. R. Bibcode: 1986SoPh..104..425S Altcode: Numerical simulations of the Sun's mean line-of-sight magnetic field suggest an origin for the 28-to 29-day recurrent patterns of the field and its associated interplanetary phenomena. The patterns are caused by longitudinal fluctuations in the eruption of new magnetic flux, the transport of this flux to mid latitudes by supergranular diffusion and meridional flow, and the slow rotation of the resulting flux distributions at the 28- to 29-day periods characteristic of those latitudes. Title: SOLWIND observations of coronal mass ejections during 1979-1985 Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1986sfcp.nasa..241S Altcode: Coronal observations have been processed for parts of each year during the interval 1979-1985. Around sunspot maximum, coronal mass ejections (CMEs) occurred at the rate of approximately 2 per day, and had a wide range of physical and morphological properties. During the recent years of relatively low sunspot number, CMEs occurred at the rate of only 0.2 per day, and were dominated by the class of so-called streamer blowout. These special CMEs maintained a nearly constant occurrence rate of roughly 0.1 per day during the entire interval. Title: Complimentary Aspects of the Mean and Gross Solar Magnetic Fields Authors: DeVore, C. R.; Sheeley, N. R., Jr. Bibcode: 1986BAAS...18..710D Altcode: No abstract at ADS Title: Solar Filament Eruptions and Energetic Particle Events Authors: Kahler, S. W.; Cliver, E. W.; Cane, H. V.; McGuire, R. E.; Stone, R. G.; Sheeley, N. R., Jr. Bibcode: 1986ApJ...302..504K Altcode: The 1981 December 5 solar filament eruption that is associated with an energetic (E greater than 50 MeV) particle event observed at 1 AU. The eruption was photographed in H-alpha and was observed by the Solwind whitelight coronagraph on P78-1. It occurred well away from any solar active region and was not associated with an impulsive microwave burst, indicating that magnetic complexity and a detectable impulsive phase are not required for the production of a solar energetic particle (SEP) event. No metric type II or IV emission was observed, but an associated interplanetary type II burst was detected by the low-frequency radio experiment on ISEE 3. The December 5 and two other SEP events lacking evidence for low coronal shocks had unusually steep energy spectra (gamma greater than 3.5). In terms of shock acceleration, this suggests that shocks formed relatively high in the corona may produce steeper energy spectra than those formed at lower altitudes. It is noted that the filament itself maybe one source of the ions accelerated to high energies, since it is the only plausible coronal source of the He(+) ions observed in SEP events. Title: The Decay of the Mean Solar Magnetic Field Authors: Sheeley, N. R., Jr.; DeVore, C. R. Bibcode: 1986SoPh..103..203S Altcode: We have analyzed the effects that differential rotation and a hypothetical meridional flow would have on the evolution of the Sun's mean line-of-sight magnetic field as seen from Earth. By winding the large-scale field into strips of alternating positive and negative polarity, differential rotation causes the mean-field amplitude to decay and the mean-field rotation period to acquire the value corresponding to the latitude of the surviving unwound magnetic flux. For a latitudinally broad two-sector initial field such as a horizontal dipole, the decay is rapid for about 5 rotations and slow with a t−1/2 dependence thereafter. If a poleward meridional flow is present, it will accelerate the decay by carrying the residual flux to high latitudes where the line-of-sight components are small. The resulting decay is exponential with an e-folding time of 0.75 yr (10 rotations) for an assumed 15 m s−1 peak meridional flow speed. Title: Coronal mass ejection associated with the stationary post-flare arch of 21 22 May 1980 Authors: McCabe, Marie K.; Švestka, Zdeněk F.; Howard, Russell A.; Jackson, Bernard V.; Sheeley, Neil R. Bibcode: 1986SoPh..103..399M Altcode: By using a combination of X-ray (HXIS), Hα (Haleakala), white-light corona (Solwind), and zodiacal light (Helios) images on 21-22 May, 1980 we demonstrate, and try to explain, the co-existence of a coronal mass ejection with a stationary post-flare coronal arch. The mass ejection was seen, both by Solwind and Helios, in prolongation of the path of a powerful spray, whereas the active region filament did not erupt. A tentative comparison is made with other occurrences of stationary, or quasi-stationary post-flare coronal arches. Title: Erratum - Numerical Simulations of Largescale Solar Magnetic Fields Authors: DeVore, C. R.; Sheeley, N. R., Jr.; Boris, J. P.; Young, T. R., Jr.; Harvey, K. L. Bibcode: 1986AuJPh..39..115D Altcode: No abstract at ADS Title: Solar gradual hard X-ray bursts: Observations and an interpretation Authors: Cliver, E. W.; Dennis, B. R.; Kiplinger, A.; Kane, S.; Neidig, D. F.; Sheeley, N.; Koomen, M. Bibcode: 1986AdSpR...6f.249C Altcode: 1986AdSpR...6..249C A recent study of solar gradual hard X-ray bursts is summarized. The data are interpreted in terms of a model involving the acceleration and trapping of electrons in post flare loop systems following coronal mass ejections. A controversy about the classification of the metric continuum that typically accompanies gradual hard X-ray events is addressed. Title: Coronal mass ejections and coronal structures. Authors: Hildner, E.; Bassi, J.; Bougeret, J. L.; Duncan, R. A.; Gary, D. E.; Gergely, T. E.; Harrison, R. A.; Howard, R. A.; Illing, R. M. E.; Jackson, B. V.; Kahler, S. W.; Kopp, K.; Low, B. C.; Lantos, P.; Phillips, K. J. H.; Poletto, G.; Sheeley, N. R., Jr.; Stewart, R. T.; Svestka, Z.; Waggett, P. W.; Wu, S. T. Bibcode: 1986NASCP2439....6H Altcode: Contents: 1. Introduction. 2. Observations. 3. Initiation of coronal mass ejections - observations. 4. Modelling of coronal mass ejections and post-flare arches. 5. Interplanetary effects of coronal mass ejections. 6. The slowly varying corona near solar activity maximum. 7. Summary. Title: The Solar Cycle Dependence of Coronal Mass Ejections Authors: Howard, R. A.; Sheeley, N. R., Jr.; Michels, D. J.; Koomen, M. J. Bibcode: 1986ASSL..123..107H Altcode: 1986shtd.symp..107H The Solwind white light coronagraph on P78-1 has been making routine observations of the solar corona since March 28, 1979. Data from the 1984/1985 time period has just been analyzed. During this interval, a period of low-solar-activity coronal mass ejections (CMEs) occurred at the rate of 0.2-0.4/day, in contrast to the rate of 1.8/day during the period around solar maximum, 1979-1981. The rate of equatorial CMEs also dropped by the same amount during this period. A class of CMEs, 'streamer blowouts', occurred at the same rate during the two epochs. Many of the parameters associated with CMEs, their type, their angular span, central latitude, mass, speed, and energy, have changed from their distributions at solar maximum. During the 1984/1985 period, CMEs are confined to low latitudes, rarely reaching the high latitudes seen during the maximum years. They are smaller, slower, less massive, and less energetic. Title: Solwind observations of coronal mass ejections during 1979 - 1985. Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1986NASCP2421..241S Altcode: Around sunspot maximum, coronal mass ejections (CMEs) occurred at the rate of approximately 2 per day, and had a wide range of physical and morphological properties. During the recent years of relatively low sunspot number, CMEs occurred at the rate of only 0.2 per day, and were dominated by the class of so-called "streamer blowouts." These special CMEs maintained a nearly constant occurrence rate of roughly 0.1 per day during the entire interval. Title: Simulations of Magnetic-Flux Transport in Solar Active Regions Authors: DeVore, C. R.; Sheeley, N. R., Jr.; Boris, J. P.; Young, T. R., Jr.; Harvey, K. L. Bibcode: 1985SoPh..102...41D Altcode: We simulate the evolution of several observed solar active regions by solving a transport equation for magnetic flux at the photosphere. The rates of rotation, meridional flow, and diffusion of the flux are determined self-consistently in the calculations. Our findings are in good quantitative agreement with previous measures of the rotation rate and diffusion constant associated with photospheric magnetic fields. Although our meridional velocities are consistent in direction and magnitude with recently reported poleward flows, relatively large uncertainties in our velocity determinations make this result inconclusive. Title: Probable Sungrazing Comets Authors: Sheeley, N. R., Jr.; Howard, R.; Koomen, M.; Michels, D.; Marsden, B. G. Bibcode: 1985IAUC.4129....1S Altcode: N. R. Sheeley, Jr., Naval Research Laboratory, reports observations of two more probable sungrazing comets (cf. IAUC 3640, 3718, 3719) in the coronagraphic data from the P78-1 SOLWIND satellite. R. Howard, M. Koomen and D. Michels were also involved with these observations of what are tentatively called SOLWIND 4 and 5, and the Central Bureau in fact received the provisional data below some months before the deliberate destruction of the satellite on Sept. 13. Improved positions are anticipated for all five objects. The apparent heliocentric separation F (solar radii) and position angle O have been converted to R.A. and Decl. by the undersigned. SOLWIND 4 UT F O R.A. (1950.0) Decl. 1981 Nov. 3.999 10.5 205.0 14 29.5 -17 42 4.038 9.7 205.0 14 30.0 -17 31 4.105 8.4 203.0 14 31.2 -17 15 4.171 7.2 200.6 14 32.3 -17 01 4.238 5.8 197.1 14 33.5 -16 43 4.304 4.6 195.5 14 34.3 -16 26 4.371 3.3? 188.5? 14 35.4 -16 08 SOLWIND 5 UT F O R.A. (1950.0) Decl. 1984 July 28.302 6.7 243.4 8 22.4 +18 15 28.309 6.6 243.8 8 22.5 +18 16 28.316 6.4 244.2 8 22.7 +18 18 28.324 6.4 244.9 8 22.7 +18 19 28.331 5.9 246.0 8 23.2 +18 24 28.368 4.8 247.6 8 24.4 +18 32 28.375 4.6 248.3 8 24.6 +18 34 28.383 4.4 249.2 8 24.8 +18 36 28.390 4.2 250.2 8 25.0 +18 38 28.397 3.9 250.8 8 25.3 +18 41 28.435 2.7 258.5 8 26.6 +18 52 28.443 2.7 259.0 8 26.6 +18 52 Computations by the undersigned suggest that SOLWIND 5 is a member of the Kreutz group with T = 1984 July 28.48 ET, Peri. = 62.28, Node = 337.30, Incl. = 139.14 (equinox 1950.0), q = 0.0044 AU. Of all the comets SOLWIND 4 is least likely to belong to the Kreutz group, and the following very hypothetical elements have been derived: T = 1981 Nov. 4.6 ET, Peri. = 97.2, Node = 25.6, Incl. = 113.7, q = 0.008 AU. Title: Coronal mass ejections: 1979-1981 Authors: Howard, R. A.; Sheeley, N. R., Jr.; Michels, D. J.; Koomen, M. J. Bibcode: 1985JGR....90.8173H Altcode: In an examination of the Solwind coronagraph images obtained during the interval March 28, 1979, to December 31, 1981, we have identified 998 coronal mass ejections and recorded their structural classes, central latitudes, latitudinal spans, speeds, excess brightnesses, and relative importances. A statistical analysis revealed the following general results. (1) The properties of coronal mass ejections (CMEs) depended strongly on their structure. Curved front, halo, and complex CMEs were the most energetic, and single spike, streamer blowout, and diffuse fan CMEs were the least energetic. CMEs occurred over a wide range of position angles, broadly centered on the equator, and had an average angular span of 45°. The leading edge moved at an average of approximately 470 km/s, and the average ejected mass and kinetic energy were 4.1×1015 g and 3.5×1030 erg, respectively. The average CME proton flux at the equator at 1 AU was 2.2×107 cm-2 s-1 or approximately 5% of the measured in situ flux during 1971-1976. (2) During 1979-1981, the average occurrence rate was 1.8/day for all CMEs, 0.9/day for ``major'' CMEs, and 0.15/day for all CMEs that crossed the equator and had an angular span of at least 45°. (3) The temporal variations in the CME occurrence rate did not show an obvious persistent relation to the variations in the sunspot number on time scales ranging from 7 to 180 days. During 1979-1981 the maximum in the 180-day average CME rate peaked in the second half of 1980, whereas the 180-day average sunspot number peaked during the firt half of 1980.

The 180-day average rate of fast CMEs (speeds of at least 800 km/s) had a monotonic increase that seemed to be more closely associated with the occurrence rate of large solar flares than with the variation of the sunspot number. Title: Simulations of the Mean Solar Magnetic Field during Sunspot CYCLE-21 Authors: Sheeley, N. R., Jr.; DeVore, C. R.; Boris, J. P. Bibcode: 1985SoPh...98..219S Altcode: Regarding new bipolar magnetic regions as sources of flux, we have computed the evolution of the photospheric magnetic field during 1976-1984 and derived the corresponding evolution of the mean line-of-sight field as seen from Earth. We obtained a good, but imperfect, agreement between the observed mean field and the field computed for a nominal choice of flux transport parameters. Also, we determined the response of the computed mean field to variations in the transport parameters and the source properties. The results lead us to regard the mean-field evolution as a random-walk process with dissipation. New eruptions of flux produce the random walk, and together differential rotation, meridional flow (if present), and diffusion provide the dissipation. The net effect of each new source depends on its strength and orientation (relative to the strength and orientation of the mean field) and on the time elapsed before the next eruption (relative to the decay time of the field). Thus the mean field evolves principally due to the contributions of the larger sources, which produce a strong, gradually evolving field near sunspot maximum but a weak, sporadically evolving field near sunspot minimum. Title: White Light and Radio Sounding Observations of Coronal Transients Authors: Bird, M. K.; Volland, H.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Sheeley, N. R., Jr.; Amstrong, J. W.; Seidel, B. L.; Stelzried, C. T.; Woo, R. Bibcode: 1985SoPh...98..341B Altcode: A concerted search for coronal transients was conducted with the `Solwind' coronagraph during the solar occultations of the two Helios spacecraft in October/November 1979. The polarization angle and bandwidth of the linearly polarized S-band downlink signal were monitored at the three 64-m tracking stations of the NASA Deep Space Network to determine coronal Faraday rotation and spectral broadening. A one-to-one correspondence could be established between abrupt disturbances in the two signal parameters and the passage of a white-light transient through the signal ray path from spacecraft to Earth. The white-light morphology and the additional information provided by the radio sounding coverage are presented for each of the five distinct events recorded. Although no specific example could be observed in sufficient detail in both white light and Faraday rotation to derive the small-scale magnetic structure, some qualitative descriptions of the orientation and rough estimates of the magnitude of the transient magnetic field could be made. Title: Energetic Protons from a Disappearing Solar Filament Authors: Kahler, S. W.; Cliver, E. W.; Cane, H. V.; McGuire, R. E.; Stone, R. G.; Sheeley, N. R., Jr. Bibcode: 1985ICRC....4...94K Altcode: 1985ICRC...19d..94K A solar energetic (E 50 MeV) particle (SEP) event observed at 1 AU began about 15000 UT on 1981 December 5. This event was associated with a fast coronal mass ejection observed with the Solwind coronagraph on the P78-1 satellite. No metric type 2 or type 4 burst was observed, but a weak interplanetary type 2 burst was observed with the low frequency radio experiment on the International Sun-Earth Explorer-3 satellite. The mass ejection was associated with the eruption of a large solar quiescent filament which lay well away from any active regions. The eruption resulted in an H alpha double ribbon structure which straddled the magnetic inversion line. No impulsive phase was obvious in either the H alpha or the microwave observations. This event indicates that neither a detectable impulsive phase nor a strong or complex magnetic field is necessary for the production of energetic ions. Title: Helios spacecraft and earth perspective observations of three looplike solar mass ejection transients Authors: Jackson, B. V.; Howard, R. A.; Sheeley, N. R., Jr.; Michels, D. J.; Koomen, M. J.; Illing, R. M. E. Bibcode: 1985JGR....90.5075J Altcode: Three looplike mass ejection transients observed from earth with the SOLWIND coronagraph and the solar maximum mission coronagraph are imaged by Helios spacecraft zodiacal light photometers. Because the Helios spacecraft are not earth orbiting, views of these ejections from the two perspectives allow conclusions to be drawn about their three-dimensional shapes. The mass ejection of May 24, 1979, in Helios data is concentrated in an outer structure followed by bright features separated by a region of depleted material. The ejections of June 18 and 29, 1980, appear restricted in position angle in Helios observations to less and the same, respectively, as in coronagraph observations. The observations imply that the ejections essentially retain their basic structure and speed out to heights (0.2-0.4 AU) observed by the Helios spacecraft. Title: The Frequency of Long-Duration Solar X-Ray Events Authors: Koomen, M. J.; Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J. Bibcode: 1985SoPh...97..375K Altcode: It is shown that the long-duration X-ray events tend to ignore the sunspot cycle. This is particularly true for events with durations of 6 hr or more. Title: High-resolution X-ray spectra of solar flares. VII - A long-duration X-ray flare associated with a coronal mass ejection Authors: Kreplin, R. W.; Doschek, G. A.; Feldman, U.; Sheeley, N. R., Jr.; Seely, J. F. Bibcode: 1985ApJ...292..309K Altcode: It has been recognized that very long duration X-ray events (lasting several hours) are frequently associated with coronal mass ejection. Thus, Sheeley et al. (1983) found that the probability of the occurrence of a coronal mass ejection (CME) increases monotonically with the X-ray event duration time. It is pointed out that the association of long-duration, or long-decay, X-ray events (LDEs) with CMEs was first recognized from analysis of solar images obtained by the X-ray telescopes on Skylab and the Naval Research Laboratory (NRL) slitless spectroheliograph. Recently high-resolution Bragg crystal X-ray spectrometers have been flown on three spacecraft, including the Department of Defense P78-1 spacecraft, the NASA Solar Maximum Mission (SMM), and the Japanese Hinotori spacecraft. In the present paper, P78-1 X-ray spectra of an LDE which had its origin behind the solar west limb on November 14, 1980 is presented. The obtained data make it possible to estimate temperatures of the hottest portion of the magnetic loops in which the emission arises. Title: A comparison of solar helium-3-rich events with type II bursts and coronal mass ejections Authors: Kahler, S.; Reames, D. V.; Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Koomen, M. J. Bibcode: 1985ApJ...290..742K Altcode: The authors ask whether the energetic particles of 3He-rich events are accelerated in the same process as that resulting in particles of normal-abundance events. They first present a list of 66 3He-rich events observed with the Goddard Space Flight Center particle detector on ISEE 3. It is then shown that these events are not statistically associated with either of the two common signatures of normal-abundance events, metric type II bursts and coronal mass ejections. This indicates that enhanced abundance events may be produced only in the impulsive phases of flares, while normal abundance events are produced in subsequent flare shock waves. Title: The Mass Distribution of Coronal Mass Ejections Authors: Jackson, B. V.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Sheeley, N. R., Jr. Bibcode: 1985BAAS...17..636J Altcode: No abstract at ADS Title: A Stochastic Model for the Mean Solar Magnetic Field During the Sunspot Cycle Authors: DeVore, C. R.; Sheeley, N. R., Jr. Bibcode: 1985BAAS...17..642D Altcode: No abstract at ADS Title: Numerical Simulations of the Mean Solar Magnetic Field During the Sunspot Cycle Authors: Sheeley, N. R., Jr.; DeVore, C. R. Bibcode: 1985BAAS...17R.642S Altcode: No abstract at ADS Title: Doppler scintillation observations of interplanetary shocks within 0.3 AU Authors: Woo, Richard; Armstrong, J. W.; Sheeley, N. R.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Schwenn, R. Bibcode: 1985JGR....90..154W Altcode: Near-sun spacecraft Doppler scintillation observations have been combined with Solwind coronagraph and Helios 1 plasma measurements to provide more definitive measurements of the evolution and propagation of interplanetary shock waves between the sun and earth orbit than have been available from previous observations. This study shows that substantial deceleration of fast shocks (shock speeds exceeding 1000 km s-1) takes place near the sun and that the amount of deceleration increases with shock speed. This is consistent with the significantly lower and rather narrow range of shock velocities observed by direct spacecraft near earth orbit. When coronal mass ejection (CME) speeds are available for the fast shocks, they are considerably lower than the speeds measured farther out but near the sun. This implies that either the fast shocks first accelerate before decelerating on their way out from the sun (assuming the CME front is identified with the shock) or the CME speeds do not represent and substantially underestimate the shock speeds in the outer corona. If the CME speeds underestimate the shock speeds of the fast shocks, they do not appear to do so for the slow shocks. If the shocks are being driven over distances indicated by the acceleration region or to the point where deceleration begins, then their velocity profiles imply that the slower shocks are being driven farther out than the faster shocks. The analysis of one piston-driven shock shows the velocity of the contact surface is about 0.58 that of the shock front velocity. Title: Numerical simulations of large-scale solar magnetic fields Authors: DeVore, C. R.; Boris, J. P.; Young, T. R., Jr.; Sheeley, N. R.; Harvey, K. L. Bibcode: 1985AuJPh..38..999D Altcode: The authors have solved numerically a transport equation which describes the evolution of the large-scale magnetic field of the Sun. Data derived from solar magnetic observations are used to initialize the computations and to account for the emergence of new magnetic flux during the sunspot cycle. The authors' objective is to assess the ability of the model to reproduce the observed evolution of the field patterns. They discuss recent results from simulations of individual active regions over a few solar rotations and of the magnetic field of the Sun over sunspot cycle 21. Title: Coronal mass ejections and interplanetary shocks Authors: Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Koomen, M. J.; Schwenn, R.; Muehlhaeuser, K. H.; Rosenbauer, H. Bibcode: 1985JGR....90..163S Altcode: A comparison between Solwind observations of coronal mass ejections (CME's) and Helios 1 observations of interplanetary shocks during 1979-1982 indicates that 72% of the shocks were associated with large, low-latitude mass ejections on the nearby limb. Most of the associated CME's has speeds in excess of 500 km/s, but some of them had speeds in the range 200-400 km/s. An additional 26% of the shocks may have been associated with CME's, but we were less confident of these associations because the sizes and locations of the CME's did not seem appreciably different from those of the numerous CME's without Helios shocks. Only 2% of the shocks clearly lacked CME's. As the average level of sunspot activity declined during 1982, the shock frequency also declined, but the observed shocks and some of their associated CME's had unusually high speeds well in excess of 1000 km/s. Title: Characteristics of coronal mass ejections associated with solar frontside and backside metric type II bursts Authors: Kahler, S. W.; Cliver, E. W.; Sheeley, N. R.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1985JGR....90..177K Altcode: We compare fast (v>=500 km s-1) coronal mass ejections (CME's) with reported metric type II bursts to study the properties of CME's associated with coronal shocks. We confirm an earlier report of fast frontside CME's with no associated metric type II bursts and calculate that 33+/-15% of all fast frontside CME's are not associated with such bursts. Faster CME's are more likely to be associated with type II bursts, as expected from the hypothesis of piston-driven shocks. However, CME brightness and associated peak 3-cm burst intensity are also important factors, as might be inferred from the Wagner and MacQueen (1983) view of type II shocks decoupled from associated CME's. We use the equal visibility of solar frontside and backside CME's to deduce the observability of backside type II bursts. We calculate that 23+/-7% of all backside type II bursts associated with fast CME's can be observed at the earth and that 13+/-4% of all type II bursts originate in backside flares. CME speed again is the most important factor in the observability of backside type II bursts. Title: Associations beteen coronal mass ejections and solar energetic proton events Authors: Kahler, S. W.; Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Koomen, M. J.; McGuire, R. E.; von Rosenvinge, T. T.; Reames, D. V. Bibcode: 1984JGR....89.9683K Altcode: We have used data from the Naval Research Laboratory (NRL) white light coronograph on the P78-1 spacecraft and energetic (E>4 MeV) proton data from the Goddard Space Flight Center (GSFC) detectors on the IMP 8 and ISEE 3 spacecraft to investigate the association between proton events originating in flares and coronal mass ejections (CME's). The primary data were 50 prompt proton events observed between April 1979 and February 1982 for which reduced coronograph data were available. H alpha flares could be confidently associated with 27 of these events, and in 26 of these 27 cases an associated CME was found, indicating a high but not perfect association of prompt proton events with CME's. Peak proton fluxes correlate with both the speeds and the angular sizes of the associated CME's. We show that the CME speeds do not significantly correlate with CME angular sizes, so that the peak proton fluxes are correlated with two independent CME parameters. With larger angular sizes, CME's are more likely to be loops and fans rather than jets and spikes and are more likely to intersect the ecliptic. Which of these factors is important to the peak proton flux correlation cannot be determined from the data. We find weak evidence that steeper proton spectra are associated with faster and wider CME's. Two of the 50 proton events of the study and two additional events, all with no associated CME's share common characteristics: relatively short duration (~1) day proton events with low fluxes, parent flares with short (~10 min) soft x ray duration, close magnetic connection to the earth, and gamma ray and metric type II emission. Title: Coronal Mass Ejections and Sudden Filament Disappearances Authors: Sheeley, N. R., Jr.; Howard, R. A.; Harvey, K. L. Bibcode: 1984BAAS...16..930S Altcode: No abstract at ADS Title: Characteristics of Flares Producing Metric Type-II Bursts and Coronal Mass Ejections Authors: Kahler, S.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1984SoPh...93..133K Altcode: We attempt to study the origin of coronal shocks by comparing several flare characteristics for two groups of flares: those with associated metric type II bursts and coronal mass ejections (CMEs) and those with associated metric type II bursts but no CMEs. CMEs accompany about 60% of all flares with type II bursts for solar longitudes greater than 30°, where CMEs are well observed with the NRL Solwind coronagraph. Hα flare areas, 1-8 Å X-ray fluxes, and impulsive 3 cm fluxes are all statistically smaller for events with no CMEs than for events with CMEs. It appears that both compact and large mass ejection flares are associated with type II bursts. The events with no CMEs imply that at least many type II shocks are not piston-driven, but the large number of events of both groups with small 3 cm bursts does not support the usual assumption that type II shocks are produced by large energy releases in flare impulsive phases. The poor correlation between 3 cm burst fluxes and the occurrence of type II bursts may be due to large variations in the coronal Alfvén velocity. Title: The concentration of the large-scale solar magnetic field by a meridional surface flow Authors: DeVore, C. R.; Boris, J. P.; Sheeley, N. R., Jr. Bibcode: 1984SoPh...92....1D Altcode: We calculate analytical and numerical solutions to the magnetic flux transport equation in the absence of new bipolar sources of flux, for several meridional flow profiles and a range of peak flow speeds. We find that a poleward flow with a broad profile and a nominal 10 m s−1 maximum speed concentrates the large-scale field into very small caps of less than 15° half-angle, with average field strengths of several tens of gauss, contrary to observations. A flow which reaches its peak speed at a relatively low latitude and then decreases rapidly to zero at higher latitudes leads to a large-scale field pattern which is consistent with observations. For such a flow, only lower latitude sunspot groups can contribute to interhemispheric flux annihilation and the resulting decay and reversal of the polar magnetic fields. Title: Associations between coronal mass ejections and metric type II bursts Authors: Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Robinson, R. D.; Koomen, M. J.; Stewart, R. T. Bibcode: 1984ApJ...279..839S Altcode: A statistical comparison of metric type II bursts and coronal mass ejections (CMEs) during 1979-1982 was carried out. Type II bursts without CMEs were associated with short-lived (0.5 hr) soft X-ray events, but not with interplanetary shocks at the Helios 1 spacecraft. Type II bursts with CMEs were associated with longer-lived X-ray events (3 hr on the average) and interplanetary shocks, and the CMEs had speeds greater than 400 km/s. CMEs without metric type II bursts were divided equally into groups faster and slower than 455 km/s. The faster CMEs were associated with interplanetary shocks, some of which originated on the visible disk where metric type II bursts should have been observed if they had occurred. These results suggest that (1) shocks without CMEs have a relatively impulsive origin and may die out sooner than many shocks with CMEs which are piston driven, and (2) either some fast CMEs do not reach shock-producing super-Alfvenic speeds until they leave the lower corona where the metric emission originates, or these CMEs form shocks that are unable to excite type II emission in the lower corona. Title: The Propagation of Transient Solar Events Authors: Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Koomen, M. J. Bibcode: 1984BAAS...16Q.454S Altcode: No abstract at ADS Title: The Temporal Variation of Coronal Mass Ejections During 1979-1981 Authors: Howard, R. A.; Sheeley, N. R., Jr.; Michels, D. J.; Koomen, M. J. Bibcode: 1984BAAS...16..454H Altcode: No abstract at ADS Title: Solar Energetic Proton Events Unassociated with Coronal Mass Ejections Authors: Kahler, S.; Evenson, P.; McGuire, R. E.; Reames, D. V.; von Rosenvinge, T. T.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1984BAAS...16..453K Altcode: No abstract at ADS Title: Synoptic observations of coronal transients and their interplanetary consequences Authors: Michels, D. J.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Schwenn, R.; Mulhauser, K. H.; Rosenbauer, H. Bibcode: 1984AdSpR...4g.311M Altcode: 1984AdSpR...4..311M A small coronagraph has been placed in orbit to monitor the sun's outer corona from 2.5 to 10.0 solar radii, and five years of nearly continuous synoptic observations have now been completed. Rapid and sensitive image processing techniques have been developed to screen the data for transient phenomena, particularly coronal mass ejections (CMEs). About 50,000 coronal images have been examined, out of a five-year total of 68,000, and a standardized listing of more than 1,200 coronal transients for the period 1979-1982 has been prepared. These data have been analysed in the light of other available information, particularly on conditions in the interplanetary plasma. The dynamical characteristics of the active corona, as they are beginning to emerge from the data, are presented. We find that coronal mass ejections exercise significant influence on the interplanetary solar wind. They are the source of disturbances that are frequent and energetic, that tend to be somewhat focussed, that often reach shock intensity, and that propagate to large heliocentric distances, sometimes causing major geomagnetic storms. Title: Evolution of solar magnetic flux. Authors: Boris, J. P.; DeVore, C. R.; Golub, L.; Howard, R. F.; Low, B. C.; Sheeley, N. R., Jr.; Simon, G. W.; Tsinganos, K. C. Bibcode: 1984NASRP1120....3B Altcode: Contents: Introduction. Appearance of magnetic flux: models for flux emergence, unexplained observations. Dynamics of surface magnetic flux: magnetic flux transport, magnetic flux structure. Disappearance of magnetic flux: theoretical considerations, observations of flux disappearance. Summary. Title: Coronal transients and their interplanetary effects. Authors: Hundhausen, A. J.; Burlaga, L. F.; Feldman, W. C.; Gosling, J. T.; Hildner, E.; House, L. L.; Howard, R. A.; Krieger, A. S.; Kundu, M. R.; Low, B. C.; Sheeley, N. R., Jr.; Steinolfson, R. S.; Stewart, R. T.; Stone, R. G.; Wu, S. T. Bibcode: 1984NASRP1120....6H Altcode: Contents: 1. Introduction. 2. Background material: Ancient history - solar flares and geomagnetic storms. Modern history - interplanetary shock waves. Coronal transients or mass ejections. 3. The present: Theoretical models. New observations of coronal mass ejections. 4. The future: Solar origins. Interplanetary effects. Title: Evidence for Directivity of Coronal Transients Authors: Michels, D. J.; Howard, R. A.; Sheeley, N. R., Jr.; Koomen, M. J. Bibcode: 1984sii..conf..319M Altcode: No abstract at ADS Title: Long-term synoptic observations of Solar coronal mass ejections Authors: Michels, D. J.; Howard, R. A.; Koomen, M. J.; Sheeley, N. R. Bibcode: 1984stp..conf..367M Altcode: No abstract at ADS Title: The Gle-Associated Flare of 21 August 1979 Authors: Cliver, E. W.; Kahler, S. W.; Cane, H. V.; Koomen, M. J.; Michels, D. J.; Howard, R. A.; Sheeley, N. R., Jr. Bibcode: 1984sii..conf..205C Altcode: No abstract at ADS Title: The statistical properties of coronal mass ejections during 1979-1981 Authors: Howard, R. A.; Sheeley, N. R.; Koomen, M. J.; Michels, D. J. Bibcode: 1984AdSpR...4g.307H Altcode: 1984AdSpR...4..307H The Solwind coronagraph on the P78-1 earth-orbiting satellite has been monitoring the Sun routinely at 10-minute intervals during the 5-year interval from April, 1979 to the present. In a statistical analysis of about 1000 mass ejections observed through the end of 1981, we find an average occurrence rate of 1.8 mass ejections per day. Histograms of speed, central latitude, angular span, brightness, and other parameters have been constructed, and properties such as shape classification have been tabulated. These characteristics are summarized for these years near sunspot maximum. The average speed and mass estimate are found to be similar to those found at the declining phase of the previous sunspot cycle. The angular span and central latitude distributions are quite different than seen during the declining phase, and are very dependent upon structural class. The fluctuations in the occurrence rate of CMEs does not seem to match the fluctuations in the sunspot number. There is a tendency for high speed CMEs to occur more frequently in 1981 than in 1980, and more frequently in 1980 than in 1979. Title: Radio and Visible Light Observations of a Coronal Arcade Transient Authors: Gergely, T. E.; Kundu, M. R.; Erksine, F. T., III; Sawyer, C.; Wagner, W. J.; Illing, R.; House, L. L.; McCabe, M. K.; Stewart, R. T.; Nelson, G. J.; Koomen, M. J.; Michels, D.; Howard, R.; Sheeley, N. Bibcode: 1984SoPh...90..161G Altcode: We discuss simultaneous visible-light and radio observations of a coronal transient that occurred on 9 April, 1980. Visible-light observations of the transient and the associated erupting prominence were available from the Coronagraph/Polarimeter carried aboard SMM, the P78-1 coronagraph, and from the Haleakala Observatory. Radio observations of the related type III-II-IV bursts were available from the Clark Lake and Culgoora Observatories. The transient was extremely complex; we suggest that an entire coronal arcade rather than just a single loop participated in the event. Type III burst sources observed at the beginning of the event were located along a nearby streamer, which was not disrupted, but was displaced by the outmoving loops. The type II burst showed large tangential motion, but unlike such sources usually do, it had no related herringbone structure. A moving type IV burst source can be associated with the most dense feature of the white-light transient. Title: Coronal Transients Observed during Solar Occultation of the HELIOS Spacecraft in STIP Interval VIII Authors: Bird, M. K.; Volland, H.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Sheeley, N. R., Jr.; Armstrong, J. W.; Seidel, B. L.; Stelzried, C. T.; Woo, R. Bibcode: 1984sii..conf..101B Altcode: No abstract at ADS Title: The GLE-associated flare of 21 August, 1979 Authors: Cliver, E. W.; Kahler, S. W.; Cane, H. V.; Koomen, M. J.; Michels, D. J.; Howard, R. A.; Sheeley, N. R., Jr. Bibcode: 1983SoPh...89..181C Altcode: We use a variety of ground-based and satellite measurements to identify the source of the ground level event (GLE) beginning near 06∶30 UT on 21 August, 1979 as the 2B flare with maximum at ∼06∶15 UT in McMath region 16218. This flare differed from previous GLE-associated flares in that it lacked a prominent impulsive phase, having a peak ∼9 GHz burst flux density of only 27 sfu and a ≳20 keV peak hard X-ray flux of ≲3 × 10-6 ergs cm-2s-1. Also, McMath 16218 was magnetically less complex than the active regions in which previous cosmic-ray flares have occurred, containing essentially only a single sunspot with a rudimentary penumbra. The flare was associated with a high speed (≳700 km s-1) mass ejection observed by the NRL white light coronagraph aboard P78-1 and a shock accelerated (SA) event observed by the low frequency radio astronomy experiment on ISEE-3. Title: Associations between coronal mass ejections and interplanetary shocks. Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Schwenn, R.; Muhlhauser, K. H.; Rosenbauer, H. Bibcode: 1983NASCP.2280.693S Altcode: 1983sowi.conf..693S The authors are in the process of comparing nearly continuous complementary coronal observations and interplanetary plasma measurements for the years 1979 - 1982. Their preliminary results show that almost all low-latitude high-speed coronal mass ejections (CME's) were associated with shocks at HELIOS 1. Some suitably directed low-speed CME's were clearly associated with shocks while others may have been associated with disturbed plasma (such as NCDE's) without shocks. A few opposite-hemisphere CME's associated with great flares also seemed to have been associated with shocks at HELIOS. Title: Associations between coronal mass ejections and soft X-ray events Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1983ApJ...272..349S Altcode: The association between white light coronal mass ejections (CMEs) and full-disk X ray events have been examined as a function of X ray duration during the recent years of high sunspot activity (1979-1981). On a time scale of hours, no duration interval has been found that separates X ray events into two distinct classes depending on whether or not they have associated CMEs. Rather, the tendency for long-duration X ray events to have associated CMEs reflects the fact that, as X ray duration increases, the differential distribution of events without CMEs falls off faster than the distriution of X ray events with CMEs. Title: The Correlation of Coronal Mass Ejections with Energetic Flare Proton Events Authors: Kahler, S. W.; McGuire, R. E.; Reames, D. V.; von Rosenvinge, T. T.; Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Koomen, M. J. Bibcode: 1983ICRC....4....6K Altcode: 1983ICRC...18d...6K Proton events of energies of at least 4 MeV presumed due to solar flares are compared with coronal mass ejections (CMEs) observed with an orbiting coronagraph. H alpha flares are associated with 27 of the 50 flare proton events of the study. Each of these 27 flares is then associated temporally and spatially with a CME, confirming the earlier conclusion, based on Skylab data, that a CME may be a necessary condition for a flare proton event. Peak 4-22 MeV proton fluxes correlate with both the speeds and the angular sizes of the associated CMEs. CMEs of larger angular sizes are more likely to be loops or fans rather than jets or spikes and are more likely to intersect the ecliptic. Title: Helios Images of a Coronal Mass Ejection Transient Authors: Jackson, B. V.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Sheeley, N. R. Bibcode: 1983BAAS...15..705J Altcode: No abstract at ADS Title: Major Mass Ejection Rate From Three Space Coronagraphs Authors: Sawyer, C.; Howard, R.; Sheeley, N.; Koomen, M.; Michels, D. Bibcode: 1983BAAS...15..706S Altcode: 1983BAAS...15..683M No abstract at ADS Title: On the Nature of Coronal Mass Ejections During the Period 28 March 1979 through 30 June 1981 Authors: Howard, R. A.; Sheeley, N. R., Jr.; Koomen, M. J.; Michels, D. J. Bibcode: 1983BAAS...15R.703H Altcode: No abstract at ADS Title: The solar corona on 31 July, 1981 Authors: Fisher, R. R.; Lacey, L. R.; Rock, K. A.; Yasukawa, E. A.; Sheeley, N. R., Jr.; Michels, D. J.; Howard, R. A.; Koomen, M. J.; Bagrov, A. Bibcode: 1983SoPh...83..233F Altcode: Various instruments were used to observe the solar corona near or at the time of total eclipse, 31 July, 1981. The High Altitude Observatory (HAO) coronal eclipse camera and the MK-III K-coronameter recorded the lower portions of the corona; the distribution of white light material above 3 R⊙ was observed with the Naval Research Laboratory (NRL) satellite coronagraph on P78-1. These data sets are used to describe coronal structure and to identify coronal active regions. The polar coronal holes, as developed at this time in the solar cycle, were offset from the poles of rotation; both were seen displaced eastward on eclipse day. High latitude streamers appear in all three data sets, extending from the base of the corona outward to at least eight solar radii from Sun center. At least two transients were observed by the NRL experiment on the eclipse day, but it is likely that no transient was in progress during any observation along the eclipse path. A distribution of the white-light corona, derived from synoptic K-coronameter data, is given. Title: Meridional Flows and Magnetic Flux Transport on the Sun Authors: Boris, J. P.; Sheeley, N. R., Jr.; Young, T. R., Jr.; DeVore, C. R.; Harvey, K. L. Bibcode: 1983BAAS...15R.701B Altcode: No abstract at ADS Title: Coronal Mass Ejections and Interplanetary Disturbances Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Schween, R.; Muhlauser, K. H.; Rosenbauer, H. Bibcode: 1983BAAS...15..699S Altcode: No abstract at ADS Title: Observations of Major Flares in He I 10830 Authors: Harvey, K. L.; Recely, F.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1983BAAS...15..712H Altcode: No abstract at ADS Title: Associations between Coronal Mass Ejections and Solar Energetic Proton Events Authors: Kahler, S. W.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; McGuire, R. E.; von Rosenvinge, T. T.; Reames, D. V. Bibcode: 1983BAAS...15..699K Altcode: No abstract at ADS Title: A White-Light / Fex / Hα Coronal Transient Observation to 10-SOLAR-RADII Authors: Wagner, W. J.; Illing, R. M. E.; Sawyer, C. B.; House, L. L.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Smartt, R. N.; Dryer, M. Bibcode: 1983SoPh...83..153W Altcode: Multi-telescope observations of the coronal transient of 15-16 April, 1980 provide simultaneous data from the Solar Maximum Mission Coronagraph/Polarimeter, the Solwind Coronagraph, and the new Emission Line Coronagraph of the Sacramento Peak Observatory. An eruptive prominence-associated white light transient is for the first time seen as an unusual wave or brightening in Fe Xgl6374 (but not in Fe XIVgl5303). Several interpretations of this fleeting enhancement are offered. Title: A quantitative study of magnetic flux transport on the Sun Authors: Sheeley, N. R., Jr.; Boris, J. P.; Young, T. R., Jr.; DeVore, C. R.; Harvey, K. L. Bibcode: 1983IAUS..102....2S Altcode: A computational model, based on diffusion, differential rotation, and meridional flow, has been developed to simulate the transport of magnetic flux on the Sun. Using Kitt Peak magnetograms as input, as have determined a best-fit diffusion constant by comparing the computed and observed fields at later times. This paper presents the initial results of a project to simulate the transport of solar magnetic flux using diffusion, differential rotation, and meridional flow. The study concerns the evolution of large-scale fields on a time scale of weeks of years, and ignores the rapid changes that accompany the emergence of new magnetic regions and the day-to-day changes of the supergranular network itself. Title: A Quantitative Study of Magnetic Flux Transport on the Sun Authors: Sheeley, N. R., Jr.; Boris, J. P.; Young, T. R., Jr.; DeVore, C. R.; Harvey, K. L. Bibcode: 1983IAUS..102..273S Altcode: A computational model, based on diffusion, differential rotation, and meridional circulation, has been developed to simulate the transport of magnetic flux on the Sun. Using Kitt Peak magnetograms as input, the authors have determined a best-fit diffusion constant by comparing the computed and observed fields at later times. The results suggest that diffusion may be fast enough to account for the observed polar magnetic field reversal without requiring a significant assist from meridional currents. Title: The observation of a coronal transient directed at Earth. Authors: Howard, R. A.; Michels, D. J.; Sheeley, N. R., Jr.; Koomen, M. J. Bibcode: 1982ApJ...263L.101H Altcode: The paper reports the observation of a large coronal transient that can only be interpreted as a three-dimensional structure. Its form is one which has not been observed before: a gradually expanding, sun-centered disk of excess brightness, whose projected radius increased from 4 to 8 solar radii during 0832-0958 UT on November 27, 1979. This earth-directed transient was the source of an interplanetary shock wave that reached ISEE 3 at 0649 UT, November 30, and earth at 0738 UT, November 30. Fitting the shock speed at ISEE 3 and the average transit speed from the sun to ISEE 3 to a power law of the form V = (V0)(r exp -n), it is found that V0 = 1980 km/s and n = 0.294, in good agreement with shock wave models. The shock speed predicted by the power law at 10 solar radii is 1000 km/s, in good agreement with the estimated frontal speed of the transient. Title: A magnetic cloud and a coronal mass ejection Authors: Burlaga, L. F.; Klein, L.; Sheeley, N. R., Jr.; Michels, D. J.; Howard, R. A.; Koomen, M. J.; Schwenn, R.; Rosenbauer, H. Bibcode: 1982GeoRL...9.1317B Altcode: An interplanetary magnetic cloud observed by the Helios 1 spacecraft was found to be associated with a coronal mass ejection observed by the NRL Solwind coronagraph on the spacecraft P78-1. The magnetic cloud was observed on June 20, 1980 when Helios 1 was at 0.54 AU and nearly 90° west of the earth-sun line. This was associated with a large loop-like coronal mass ejection observed over the west limb on June 18, 1980, moving toward Helios 1. The speed of the front of the event at Helios 1 was (470 ± 10) km/s, which is close to the mean transit speed (∽ 500 km/s). The magnetic cloud was similar to others described in the literature: The magnetic field strength was higher than average; the density was relatively low; the magnetic pressure greatly exceeded the ion thermal pressure; and the magnetic field direction changed through the cloud by rotating parallel to a plane which was highly inclined with respect to the ecliptic. Title: Simultaneous radio scattering and white light observations of a coronal transient Authors: Woo, R.; Armstrong, J. W.; Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Koomen, M. J. Bibcode: 1982Natur.300..157W Altcode: Reports that a coronal transient observed by the Solwind coronagraph off the west limb of the sun was also seen in the spectral broadening observations of the Helois-2 2.3 GHz radio signal. These simultaneous data are compared and applied to studies of the shock front. UT difference images show a time difference of up to 2 h between shock and white light occurrences. Helios and Voyager shock speed measurements are consistent, implying that the event observed by Helios is a shock. These coronal transient data show that the shock front is ahead of the white light front, but additional observations of larger events will contribute information to the understanding of coronal transient evolution as they propagate away from the sun. Title: Coronagraphic observations of two new sungrazing comets Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1982Natur.300..239S Altcode: We recently reported the discovery1 of a comet (Howard-Koomen-Michels: 1979 XI) that apparently collided with the Sun on 30 August 1979. We now report observations of two additional sungrazers that encountered the Sun on 27 January 1981 and 20 July 1981, respectively. Like comet 1979 XI, these two new comets seem to have been members of the Kreutz group of sungrazers2-4, and like 1979 XI the new comets did not reappear after their encounters with the Sun. The discovery of three previously unreported comets during the initial 2.3 yr of our satellite coronal observations leads us to suspect that sungrazers are much more common than one might suppose from the list of only nine known sungrazers observed during the years 1668-19705,6. Title: A Model for the Evolution of Large-Scale Magnetic Fields in the Solar Photosphere Authors: DeVore, C. R.; Boris, J. P.; Young, T. R., Jr.; Sheeley, N. R., Jr.; Harvey, K. L. Bibcode: 1982BAAS...14..978D Altcode: No abstract at ADS Title: Probable Sungrazing Comet Authors: Michels, D. J.; Sheeley, N.; Harlow, F.; Marsden, B. G. Bibcode: 1982IAUC.3718....1M Altcode: D. J. Michels, Naval Research Laboratory. reports that continued analysis of the P78-l SOLWIND data has revealed a second sungrazing comet (cf. IAUC 3640, 3647). The 15 observations below were obtained as the comet approached the sun on 1981 Jan. 26-27. The discovery team Includes N. Sheeley, 0. Roberts and F. Harlow. Calculations at N.R.L. Indicate that the observations are consistent with a Kreutz-type orbit and that the comet possibly hit the sun. The object brightened from ~ mag 0.0 at 8 solar radii to mag -2.5 or brighter at 3 solar radii, apparently with a fading to mag +1.0 near 5.5 solar radii. Contrary to the situation with the earlier object (comet 1979 XI), there was this time no evidence of residue from the comet after its presumed perihelion passage. 1981 UT rho theta R. A. (1950) Decl. Jan. 26.860 8.07 118.0 20 43.40 -19 21.3 26.867 7.87 117.8 20 43.22 -19 19.8 26.874 7.83 117.6 20 43.22 -19 19.1 26.881 7.63 117.1 20 43.10 -19 16.9 26.888 7.30 116.8 20 42.74 -19 14.7 26.927 6.12 115.6 20 41.72 -19 06.4 26.934 5.97 115.3 20 41.66 -19 05.1 26.941 5.93 114.8 20 41.66 -19 04.1 26.947 5.67 114.0 20 41.42 -19 01.7 26.954 5.41 113.7 20 41.18 -19 00.0 26.994 4.01 109.7 20 39.92 -18 49.6 27.001 3.71 109.4 20 39.62 -18 48.4 27.008 3.66 109.0 20 39.62 -18 47.7 27.014 3.40 107.9 20 39.38 -18 45.9 27.021 3,05 105.6 20 39.02 -18 43.1 The heliocentric separations rho are given in units of the instantaneous solar radius, and the position angle theta is measured counterclockwise from the sun's north pole. The followIng parabolic orbital elements, derived by the undersigned on the assumption that the comet's perihelion direction agrees with the Kreutz group, satisfy the observations within 2'.5: T = 1981 Jan. 27.076 ET Peri. = 71.982 Node = 349.967 1950.0 q = 0.00488 AU (= 1.05 Rs) Incl. = 142.738 Title: Magnetic measurements of coronal holes during 1975 1980 Authors: Harvey, K. L.; Sheeley, N. R., Jr.; Harvey, J. W. Bibcode: 1982SoPh...79..149H Altcode: Photospheric magnetic fluxes and average field strengths have been measured beneath 33 coronal holes observed on 63 occasions during 1975-1980. The principal result is that low-latitude holes contained 3 times more flux near sunspot maximum than near minimum despite the fact that their sizes were essentially the same. Average magnetic field strengths ranged from 3-36 G near sunspot maximum compared to 1-7 G near minimum. Evidently the low-latitude coronal holes received a proportion of the extra flux that was available at low latitudes near sunspot maximum. Title: The coronal field lines of an evolving bipolar magnetic region Authors: Sheeley, N. R., Jr. Bibcode: 1982ApJ...255..316S Altcode: A simple potential field model is presented to illustrate that loops of magnetic flux rise upward through the corona during the relatively short growth phase of a bipolar magnetic region but contract back to the sun's surface during the much longer decay phase of the photospheric region. To reconcile this behavior with the unidirectional, solar-wind-driven convection of flux outward from the sun, one must postulate the existence of an X-type neutral line in the middle corona where open field lines can be converted back to closed ones. Title: Observations of coronal structure during sunspot maximum. Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Harvey, K. L.; Harvey, J. W. Bibcode: 1982SSRv...33..219S Altcode: This paper presents some of the results that have been obtained from the Kitt Peak observations of coronal holes and the NRL observations of coronal transients during the recent years near sunspot maximum (1979 1981). On the average, low-latitude coronal holes of comparable size contained 3 times more flux near sunspot maximum than near the previous minimum. In the outer corona, transients occurred at the observed rate of at least 2 per day, and quiet conditions persisted during less than 15 % of the observed days. We describe a sample of the more than 800 events that we have observed so far, including the observation of a comet apparently colliding with the Sun. Title: The observation of a coronal transient directed at earth. Authors: Michels, D. J.; Howard, R. A.; Koomen, M. J.; Sheeley, N. R., Jr. Bibcode: 1982BAAS...14R.572M Altcode: No abstract at ADS Title: Observations of a Comet on Collision Course with the Sun Authors: Michels, D. J.; Sheeley, N. R.; Howard, R. A.; Koomen, M. J. Bibcode: 1982Sci...215.1097M Altcode: A brilliant new comet (1979 XI: Howard-Koomen-Michels) was discovered in data from the Naval Research Laboratory's orbiting SOLWIND coronagraph. An extensive sequence of pictures, telemetered from the P78-1 satellite, shows the coma, accompanied by a bright and well-developed tail, passing through the coronagraph's field of view at a few million kilometers from the sun. Preliminary orbital calculations based on the observed motion of the comet's head and morphology of the tail indicate that this previously unreported object is a sungrazing comet and may be one of the group of Kreutz sungrazers. It appears from the data that the perihelion distance was less than 1 solar radius, so that the cometary nucleus encountered dense regions of the sun's atmosphere, was completely vaporized, and did not reappear after the time of closest approach to the sun. After this time, however, cometary debris, scattered into the ambient solar wind, caused a brightening of the corona over one solar hemisphere and to heliocentric distances of 5 to 10 solar radii. Title: Probable Sungrazing Comet Authors: Howard, R.; Koomen, N.; Michels, D. J.; Sheeley, N.; Marsden, B. G. Bibcode: 1981IAUC.3640....1H Altcode: Images of a probable comet have been found at the Naval Research Laboratory, Washington, on coronagraph exposures obtained from the satellite P78-1 in 1979. The object was found by R. Howard as a result of instrumentation developed and operated by N. Koomen and D. J. Michels. The following heliocentric separations rho (in units of the instantaneous solar radius) and position angles theta (measured counterclockwise from the sun's north pole) have been derived by N. Sheeley and converted to R.A. and Decl. by the undersigned. The head of the object was somewhat brighter than Venus, and a tail was directed roughly away from the center of the sun. 1979 UT rho theta R.A. (1950) Decl. Aug. 30.789 5.96 234.2 10 26.47 + 8 45.1 30.796 5.67 233.8 10 26.80 + 8 45.5 30.802 5.27 234.3 10 27.22 + 8 47.8 30.809 5.16 234.6 10 27.36 + 8 48.6 30.816 5.09 235.4 10 27.43 + 8 49.8 30.856 3.65 235.7 10 29.07 + 8 54.8 30.867 3.11 236.1 10 29.67 + 8 56.9 30.885 2.56 239.2 10 30.28 + 9 00.7 At the last observation the object's head was at the edge of the coronagraph's occulting disk. On the next exposure, taken at Aug. 30.989 UT, the tail is still present, and during the next several hours cometary material evidently diffused around to p.a. ~ 360o. The comet's orbit cannot be unequivocally determined, but computations by the undersigned suggest that a retrograde solution is to be preferred, for this better explains the previous failure to detect the comet in a twilit sky. Other possible coronagraphic or hitherto unreported visual detections of the object would of course be very useful. Retrograde orbit solutions show some resemblance to the orbits of the members of the Kreutz sungrazing comet group; there would seem to be a good chance that the comet hit the sun (for the head was not detected after perihelion). The following possible orbital solution has been selected solely because of its general resemblance to the Kreutz-type orbits: T = 1979 Aug. 30.92 ET Peri. = 83.42 Node = 9.81 1950.0 q = 0.001 AU (assumed) Incl. = 142.42 Title: Coronal holes, solar wind streams, and geomagnetic disturbances during 1978 and 1979 Authors: Sheeley, N. R., Jr.; Harvey, J. W. Bibcode: 1981SoPh...70..237S Altcode: We have extended our long-term study of coronal holes, solar wind streams, and geomagnetic disturbances through the rising phase of sunspot cycle 21 into the era of sunspot maximum. During 1978 and 1979, coronal holes reflected the influence of differential rotation, and existed within a slowly-evolving large-scale pattern despite the relatively high level of sunspot activity. The long-lived 28.5-day pattern is not produced by a rigidly-rotating quasi-stationary structure on the Sun, but seems to be produced by a non-stationary migratory process associated with solar differential rotation. The association between coronal holes and solar wind speed enhancements at Earth continues to depend on the latitude of the holes (relative to the heliographic latitude of Earth), but even the best associations since 1976 have speeds of only 500-600 km s-1 rather than the values of 600-700 km s-1 that usually occurred during the declining phase of sunspot cycle 20. Title: A Comet on Collision Course with the Sun: Observations on August 30-31, 1979 Authors: Howard, R. A.; Koomen, M. J.; Michels, D. J.; Sheeley, N. R., Jr. Bibcode: 1981BAAS...13..875H Altcode: No abstract at ADS Title: A Comet on Collision Course with the Sun: Orbital Data Deduced from the Observations of Aug 30-31, 1979 Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1981BAAS...13..875S Altcode: No abstract at ADS Title: Coronagraph Observations of a Sun-directed Comet, Aug. 30-31, 1979: Images, Analysis and Photometry Authors: Koomen, M. J.; Michels, D. J.; Sheeley, N. R., Jr.; Howard, R. A. Bibcode: 1981BAAS...13R.891K Altcode: No abstract at ADS Title: A Comet on Collision Course with the Sun: Dynamical Interpretation of the Observations of Aug 30-31, 1979 Authors: Michels, D. J.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J. Bibcode: 1981BAAS...13..875M Altcode: No abstract at ADS Title: A comet on collision course with the sun: orbital data deduced from the observations of August 30 - 31, 1979. Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1981BAAS...13R.875S Altcode: No abstract at ADS Title: A comet on collision course with the sun: observations on August 30 - 31, 1979. Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J. Bibcode: 1981BAAS...13Q.875S Altcode: No abstract at ADS Title: The influence of differential rotation on the equatorial component of the sun's magnetic dipole field Authors: Sheeley, N. R., Jr. Bibcode: 1981ApJ...243.1040S Altcode: This paper examines the effect that solar differential rotation would have on a hypothetical large-scale equatorial dipole field. The evolving large-scale field pattern is expressed as a series of non-axisymmetric moments. As time increases, power is transferred to progressively higher order moments. In the 27d rotating coordinate system, each moment undergoes a small retrograde drift which remains nearly uniform until that mode begins to fade. The synodic rotation periods of the first few moments are comparable to the observed 28.5d period of the sun's large-scale field near sunspot maximum. Differential rotation may be the source of this 28.5d period, but the eruption of new flux is necessary to keep the pattern going. Title: Coronal Transients Near Sunspot Maximum Authors: Poland, A. I.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Sheeley, N. R., Jr. Bibcode: 1981SoPh...69..169P Altcode: The Naval Research Laboratory's most recent Earth-orbiting coronagraph, called Solwind, has been observing the Sun's outer corona (2.6-10.0 R⊙) at 10-min intervals since March 28, 1979. These observations provide the first comprehensive view of coronal transients near the peak of a sunspot cycle. Six, well-defined transients in our quick-look data have masses ranging from 7 × 1014 g to 2 × 1016 g and outward speeds ranging from 150 km s−1 to 900 km s−1. These values are comparable to the ones that were obtained with the OSO-7 and Skylab observations during the declining phase of the last sunspot cycle. Although the amount of quick-look data is not sufficient to provide meaningful statistics, the coronal transients near sunspot maximum seem to occur with a greater frequency and a wider latitude range than the transients during the declining phase of the cycle. In both eras, there is a good, but imperfect, association between the occurrence of coronal transients and surface phenomena such as eruptive prominences and flares. Title: The overall structure and evolution of active regions. Authors: Sheeley, N. R., Jr. Bibcode: 1981sars.work...17S Altcode: The evolutionary characteristics and structure of the magnetic fields and atmospheric phenomena associated with the development of a solar magnetic region are discussed. Bipolar magnetic regions are introduced as the source of all solar magnetic fields, formed as bundles of magnetic flux rise to and break through the solar surface and spread throughout the photosphere, chromosphere and corona. The photospheric magnetic region is shown to be characterized by bipolar flux regions of various sizes emerging rapidly for a few days, then expanding and decreasing in flux for several months and fragmenting. Sunspots and faculae are considered as tracers of the magnetic regions in the upper photosphere or lower chromosphere, while chromospheric tracers include arch filaments, field transition arches, long chromospheric threads, disk filaments and dark fibrils in chromospheric lines. The transition region and lower corona exhibit a multithermal plasma distribution, with low-temperature plasmas confined to the footprints and legs of magnetic field lines and high-temperature plasmas originating in loops or systems of unresolved loops. The bipolar magnetic region is also shown to interact with its surroundings to produce an interconnected field line pattern. Title: Coronal Evolution and Transients: 1979-1980 Authors: Howard, R. A.; Koomen, M. J.; Sheeley, N. R.; Michels, D. J. Bibcode: 1980BAAS...12R.898H Altcode: No abstract at ADS Title: The Solar Origin of An Interplanetary Shock Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Rompolt, B.; Schwenn, R. W.; Mihalov, J. D. Bibcode: 1980BAAS...12..920S Altcode: No abstract at ADS Title: Coronal Holes and the Sun's Mean Magnetic Field Authors: Harvey, K. L.; Sheeley, N. R., Jr. Bibcode: 1980BAAS...12..918H Altcode: No abstract at ADS Title: A Three-Coronagraph Record from 1 to 10 RO of the Energetics of a Coronal Transient Authors: Wagner, W. J.; Sawyer, C.; Illing, R. M. E.; House, L. L.; Querfeld, C. W.; Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Smartt, R. N. Bibcode: 1980BAAS...12Q.902W Altcode: No abstract at ADS Title: The equatorial latitude of auroral activity during 1972 1977 Authors: Sheeley, N. R., Jr.; Howard, R. A. Bibcode: 1980SoPh...67..189S Altcode: The equatorial latitude of auroral activity has been derived from both electron and optical observations with the DMSP satellites. Virtually all of the observations that were obtained during the 5-year interval June 1972-September 1977 have been used to construct a nearly continuous plot of invariant geomagnetic latitude versus time. Title: Recent Satellite Observations of the Corona Authors: Koomen, M. J.; Sheeley, N. R., Jr.; Michels, D. J.; Howard, R. A. Bibcode: 1980S&T....60..102K Altcode: Observations of the solar corona by the DOD satellite P78-1 are discussed and compared with previous findings by OSO-7 and Skylab. The satellite carries a coronagraph and several other solar instruments, including X-ray spectrometers for analyzing the spectra of solar flares and for monochromatic imaging of X-ray emission from active regions. Computer analysis of the pictures obtained in a three-day span in May 1979 shows that many of the day-to-day changes in the streamers result from the rapid ejection of coronal matter, which disrupts the streamers and leaves gradually fading structures in their place. The findings of P78-1 as well as OSO-7 and Skylab seem to agree on a connection between eruptive prominences and coronal transients, but the exact nature of the association is not yet clear. Title: The observation of a high-latitude coronal transient Authors: Sheeley, N. R., Jr.; Howard, R. A.; Koomen, M. J.; Michels, D. J.; Poland, A. I. Bibcode: 1980ApJ...238L.161S Altcode: On 1979 September 27 NRL's earth-orbiting coronagraph (Solwind) observed a coronal mass ejection whose outward direction in the plane of the sky was within 12 deg of the sun's north polar axis. Such high-latitude transients were not observed by the OSO 7 and Skylab coronagraphs during the declining phase of the last sunspot cycle, but may be relatively common near sunspot maximum. Title: Initial observations with the SOLWIND coronagraph Authors: Sheeley, N. R., Jr.; Michels, D. J.; Howard, R. A.; Koomen, M. J. Bibcode: 1980ApJ...237L..99S Altcode: The NRL Solwind coronagraph has provided the first systematic, temporally (10 minute intervals) resolved view of the outer solar corona near the peak of a sunspot cycle. It observes a 2.6-10.0 solar radii annular field of view with a spatial resolution of 1.25 arc min, and the Solwind observations allow the study of the evolution of streamers at high latitude for the first time. It is noted that most coronal structures changed significantly from day to day, which changes were associated with the ejection of material outward across the coronagraph's field of view. Attention is given to a transient which was observed to have a well-defined curved front which advanced outward across the field of view at an essentially constant speed of 500 km/s, but unlike most Skylab loop-type mass ejections, left no remnants 24 hours later. Title: Temporal Variations of Loop Structures in the Solar Atmosphere Authors: Sheeley, N. R., Jr. Bibcode: 1980SoPh...66...79S Altcode: Unique timelapse sequences of Skylab/ATM spectroheliograms reveal the following characteristics of normal (i.e. non-flare) loop structures in the solar atmosphere: At the 0.5 × 106 K temperature of Ne VII, emission is concentrated into individual spiky structures that project 104-105 km from their magnetic footpoints and live on the order of 30 min. Title: Simultaneous Measurement of Coronal Faraday Rotation and Total Electron Content During Solar Occultation of PSRO525+21 Authors: Howard, R. A.; Bird, M. K.; Koomen, M. J.; Michels, D. J.; Sheeley, N. R., Jr. Bibcode: 1980BAAS...12..545H Altcode: No abstract at ADS Title: The evolution of the polar coronal holes Authors: Sheeley, N. R., Jr. Bibcode: 1980SoPh...65..229S Altcode: He I 10830 Å synoptic maps, obtained at the Kitt Peak National Observatory during 1974-1979, show that the Sun's polar coronal holes have contracted significantly during 1977-1978. Prior to the accelerated increase of sunspot activity in mid-1977, the area of each polar cap was on the order of 8% of the Sun's total surface area (4πR2), whereas toward the end of 1978 these areas fell below 2% of 4πR2. Synoptic polar plots show that the vestigual holes had irregular shapes and were often well removed from the poles themselves. These results are consistent with the changes that one would expect when the polar magnetic fields are weakening just prior to sunspot maximum. Title: Coronal Holes, Solar Wind Streams, and Geomagnetic Disturbances During 1978 and 1979 Authors: Sheeley, N. R., Jr.; Harvey, J. W. Bibcode: 1980BAAS...12R.545S Altcode: No abstract at ADS Title: The Lateral Expansion of the August 14, 1979 Coronal Transient Authors: Koomen, M. J.; Michels, D. J.; Howard, R. A.; Sheeley, N. R., Jr. Bibcode: 1980BAAS...12..515K Altcode: No abstract at ADS Title: The Contraction and Disappearance of the Polar Coronal Holes Authors: Sheeley, N. R., Jr. Bibcode: 1980NASCP2098..219S Altcode: 1980sscs.nasa..219S He I 10830 A spectroheliograms obtained during 1974-1979 were used to study the evolution of the Sun's polar coronal holes. Synoptic polar plots show that the holes have decreased in size to the point that only vestigual holes remain and even these remnants fluctuate with detailed sunspot activity. Title: Satellite observations of the outer corona near sunspot maximum Authors: Michels, D. J.; Howard, R. A.; Koomen, M. J.; Sheeley, N. R., Jr. Bibcode: 1980IAUS...86..439M Altcode: 1980IAUS...89..439M This paper shows the first satellite observations of the Sun's white light corona (2.6 R_⊙ - 10.0 R_⊙) during the active phase of a sunspot cycle. Since March 28, 1979, these observations have been obtained routinely with a spatial resolution of 1.25 arc min and a repetition rate of 10 minutes during the one-hour sunlit portion of each 97-minute satellite orbital period. As an illustration of these new observations, we show the coronal changes associated with the great mass of May 8, 1979. Title: The solar mass ejection of 8 May 1979 Authors: Michels, D. J.; Howard, R. A.; Koomen, M. J.; Sheeley, N. R., Jr.; Rompolt, B. Bibcode: 1980IAUS...91..387M Altcode: The solar mass ejection of May 8, 1979 is characterized using images from the NRL SOLWIND coronagraph on board the P78-1 satellite. The eruption of the polar crown filament began at about 0810 UT and reached maximum distance of 1.5 solar radii from the center of the sun at 1021 UT. The eruptive prominence subsequently faded, and some of the material fell back to the solar surface. Vestiges of the H-alpha prominence disappeared by 1120 UT. The bulk of the prominence material displayed radial velocities averaging 40 km/sec with 165 km/sec the maximum velocity observed. From 1028 UT to 1246 UT, the leading edge of the ejecta moved outward with a constant radial velocity of approximately 500 km/sec. Projected back to the solar limb, this indicated an onset near 0950 UT. Title: Solar observations with a new earth-orbiting coronagraph Authors: Sheeley, N. R., Jr.; Howard, R. A.; Michels, D. J.; Koomen, M. J. Bibcode: 1980IAUS...91...55S Altcode: No abstract at ADS Title: Rapid changes in the fine structure of a coronal "Bright point" and a small coronal "active region". Authors: Sheeley, N. R., Jr.; Golub, L. Bibcode: 1979SoPh...63..119S Altcode: A coronal `bright point' is resolved into a pattern of emission which, at any given time, consists of 2 or 3 miniature loops (each ∼2500 km in diameter and ∼12 000 km long). During the half-day lifetime of the `bright point' individual loops evolved on a time scale ∼6 min. A small `ctive region' seemed to evolve in this way, but the occasional blurring together of several loops made it difficult to follow individual changes. Title: Coronal Holes and Solar Magnetic Fields (Article published in the special issues: Proceedings of the Symposium on Solar Terrestrial Physics held in Innsbruck, May- June 1978. (pp. 137-538)) Authors: Harvey, J. W.; Sheeley, N. R., Jr. Bibcode: 1979SSRv...23..139H Altcode: Since 1972, nearly continuous observations of coronal holes and their associated photospheric magnetic fields have been made using a variety of satellite and ground-based equipment. The results of comparisons of these observations are reviewed and it is demonstrated that the structure and evolution of coronal holes is basically governed by the large-scale distribution of photospheric magnetic flux. Non-polar holes form in the decaying remnants of bipolar magnetic regions in areas with a large-scale flux imbalance. There is strong indirect evidence that the magnetic field in coronal holes is always open to interplanetary space but not all open-field regions have associated coronal holes. The well-observed declining phase of the last solar cycle was characterized by stable magnetic field and coronal hole patterns which were associated with recurrent, high-speed wind streams and interplanetary magnetic field patterns at the Earth. The ascending phase of the current cycle has been characterized by transient magnetic field and coronal hole patterns which tend to occur at high solar latitudes. This shift in magnetic field and coronal hole patterns has resulted in a less obvious and more complicated association with high-speed wind streams at the Earth. Title: Comparison of Satellite and Rocket Coronal Observations around April 13, 1979 Authors: Howard, R. A.; Michels, D. J.; Koomen, M. J.; Sheeley, N. R., Jr.; Kohl, J. L.; Munro, R. H.; Weiser, H. Bibcode: 1979BAAS...11..408H Altcode: No abstract at ADS Title: Discussion Authors: Anzer, U.; Raadu, M. A.; Rompolt, B.; Rust, D. M.; Sheeley, N.; Spicer, D. S. Bibcode: 1979phsp.coll..171A Altcode: 1979IAUCo..44..171A No abstract at ADS Title: Discussion Authors: Engvold, O.; Gaizauskas, Gaizauskas; Rust, D. M.; Sheeley, N.; Tandberg-Hanssen, E.; Ohman, Y.; Zirin, H. Bibcode: 1979phsp.coll..207E Altcode: 1979IAUCo..44..207E No abstract at ADS Title: Discussion Authors: Acton, L. W.; Kundu, M. R.; Maltby, P.; Malville, J.; Orrall, F. Q.; Sheeley, N.; Spicer, D. S. Bibcode: 1979phsp.coll..225A Altcode: 1979IAUCo..44..225A No abstract at ADS Title: Discussion Authors: Anzer, U.; Chiuderi-Drago, F.; Kundu, M. R.; Leroy, J. L.; Malville, J.; Rompolt, B.; Sheeley, N.; Stenflo, J.; Tandberg-Hanssen, E.; Öhman, Y. Bibcode: 1979phsp.coll...77A Altcode: 1979IAUCo..44...77A No abstract at ADS Title: Coronal holes, solar wind streams, and geomagnetic activity during the new sunspot cycle. Authors: Sheeley, N. R., Jr.; Harvey, J. W. Bibcode: 1978SoPh...59..159S Altcode: The paper presents results obtained for 1976-1977 using daily He I 10830 A spectroheliograms and photospheric magnetograms. It was found that as the magnetic field patterns changed, the solar atmosphere evolved from a structure with a few large long-lived low-latitude coronal holes to one with numerous small short-lived high-latitude holes. High-latitude holes recurred with a synodic rotation period of 28-29 days instead of the 27-day period already known to be characteristic of low-latitude holes. A Bartels display of the occurrence of holes, wind speed, and geomagnetic activity is considered. Title: Coronal holes, solar wind streams, and geomagnetic activity during the new sunspot cycle Authors: Harvey, J. W.; Sheeley, N. R. Bibcode: 1978SoPh...59..159H Altcode: We have extended our previous study of coronal holes, solar wind streams, and geomagnetic disturbances from the declining phase (1973-1975) of sunspot cycle 20 through sunspot minimum (1976) into the rising phase (1977) of cycle 21. Using daily He I 10830 Å spectroheliograms and photospheric magnetograms, we found the following results: As the magnetic field patterns changed, the solar atmosphere evolved from a structure having a few, large, long-lived, low-latitude coronal holes to one having numerous small, short-lived, high-latitude holes (in addition to the polar holes which persisted throughout this 5-year interval). Title: The equatorward extent of auroral activity during 1973 1974 Authors: Sheeley, N. R., Jr. Bibcode: 1978SoPh...58..405S Altcode: The equatorward boundary of auroral activity during 1973-1974 has been derived from DMSP photographs and their associated `auroral analysis records'. On a time scale of days, the equatorward position of the northern auroral oval varied in phase with the average level of geomagnetic activity. In general, this variation was associated with the occurrence of solar flares and coronal holes. On a time scale of hours, the equatorward position of the oval correlated with the AE index of substorm activity and with the strength of the southward component of the interplanetary magnetic field. Title: Coronal Holes, Solar Wind Streams and Geomagnetic Activity During the New Solar Cycle. Authors: Sheeley, N. R.; Harvey, J. W. Bibcode: 1978BAAS...10Q.461S Altcode: No abstract at ADS Title: Extreme ultraviolet observations of coronal holes. II. Association of holes with solar magnetic fields and a model for their formation during the solar cycle. Authors: Bohlin, J. D.; Sheeley, N. R., Jr. Bibcode: 1978SoPh...56..125B Altcode: Extreme-ultraviolet Skylab and ground-based solar magnetic field data have been combined to study the origin and evolution of coronal holes. It is shown that holes exist only within the large-scale unipolar magnetic cells into which the solar surface is divided at any given time. A well-defined boundary zone usually exists between the edge of a hole and the neutral line which marks the edge of its magnetic cell. This boundary zone is the region across which a cell is connected by magnetic arcades with adjacent cells of opposite polarity. Three pieces of observational evidence are offered to support the hypothesis that the magnetic lines of force from a hole are open. Kitt Peak magnetograms are used to show that, at least on a relative scale, the average field strengths within holes are quite variable, but indistinguishable from the field strengths in other quiet parts of the Sun's surface. Title: A survey of coronal holes and their solar wind associations throughout sunspot cycle 20. Authors: Broussard, R. M.; Sheeley, N. R., Jr.; Tousey, R.; Underwood, J. H. Bibcode: 1978SoPh...56..161B Altcode: To gain insight into the relationships between solar activity, the occurrence and variability of coronal holes, and the association of such holes with solar wind features such as high-velocity streams, a study of the period 1963-1974 was made. This period corresponds approximately with sunspot cycle 20. The primary data used for this work consisted of X-ray and XUV solar images obtained from rockets. The investigation revealed that: The polar coronal holes prominent at solar minimum, decreased in area as solar activity increased and were small or absent at maximum phase. This evolution exhibited the same phase difference between the two hemispheres that was observed in other indicators of activity. Title: A comparison of He ii 304 Å and He i 10 830 Å spectroheliograms Authors: Harvey, J. W.; Sheeley, N. R., Jr. Bibcode: 1977SoPh...54..343H Altcode: Spectroheliograms were obtained simultaneously in the He II 304 Å emission line and the He I 10 830 Å absorption line with an angular resolution of approximately 5″. A negative print of the 304 Å image is matched with a positive print of the 10 830 Å image so that corresponding features of the chromospheric network (including active regions) appear identical in the two images. Differences between these images include the facts that: Disk filaments and limb darkening are strongly visible in the 10 830 Å positive image, but they are weakly visible (as lightenings) in the 304 Å negative image. Title: A pictorial comparison of interplanetary magnetic field polarity, solar wind speed, and geomagnetic disturbance index during the sunspot cycle. Authors: Sheeley, N. R., Jr.; Asbridge, J. R.; Bame, S. J.; Harvey, J. W. Bibcode: 1977SoPh...52..485S Altcode: Observations of interplanetary magnetic field polarity, solar wind speed, and geomagnetic disturbance index (C9) during the years 1962-1975 are compared in a 27-day pictorial format that emphasizes their associated variations during the sunspot cycle. This display accentuates graphically several recently reported features of solar wind streams including the fact that the streams were faster, wider, and longer-lived during 1962-1964 and 1973-1975 in the declining phase of the sunspot cycle than during intervening years (Bame et al., 1976; Gosling et al., 1976). The display reveals strikingly that these high-speed streams were associated with the major, recurrent patterns of geomagnetic activity that are characteristic of the declining phase of the sunspot cycle. Finally, the display shows that during 1962-1975 the association between long-lived solar wind streams and recurrent geomagnetic disturbances was modulated by the annual variation (Burch, 1973) of the response of the geomagnetic field to solar wind conditions. The phase of this annual variation depends on the polarity of the interplanetary magnetic field in the sense that negative sectors of the interplanetary field have their greatest geomagnetic effect in northern hemisphere spring, and positive sectors have their greatest effect in the fall. During 1965-1972 when the solar wind streams were relatively slow (500 km s-1), the annual variation strongly influenced the visibility of the corresponding geomagnetic disturbance patterns. Title: Analysis of Solar-Flare Plasmas Using EUV and X-Ray Data. Authors: Tandberghanssen, E.; Sheeley, N.; Smith, J. B. Bibcode: 1977BAAS....9..311T Altcode: No abstract at ADS Title: Observations During the Impulsive Phase of the August 7, 1973, Solar Flare. Authors: Sheeley, N. R., Jr.; Kane, S. R.; Vorpahl, J. A.; Chapman, G. A. Bibcode: 1977BAAS....9..311S Altcode: No abstract at ADS Title: A Comparison of He II 304 Å and He I 10830 Å Spectroheligrams. Authors: Harvey, J. W.; Sheeley, N. R., Jr. Bibcode: 1977BAAS....9..325H Altcode: No abstract at ADS Title: An improved measurement of a spectrogram of a "gap". Authors: Chapman, G. A.; Sheeley, N. R., Jr. Bibcode: 1977SoPh...51...61C Altcode: A spectrogram of the 5250 Å region previously obtained during a period of excellent seeing has been remeasured and calibrated by reference to the preliminary KPNO photometric atlas. This analysis, using the logarithm of opacitance instead of an H-D plot, has reduced some of the effects of scattered light and shows greater facular line contrast. Title: Observations of Coronal Holes Throughout Sunspot Cycle 20. Authors: Broussard, R. M.; Underwood, J. H.; Tousey, R.; Sheeley, N. R., Jr. Bibcode: 1976BAAS....8..557B Altcode: No abstract at ADS Title: Coronal holes, solar wind streams, and recurrent geomagnetic disturbances: 1973 1976 Authors: Sheeley, N. R., Jr.; Harvey, J. W.; Feldman, W. C. Bibcode: 1976SoPh...49..271S Altcode: Observations of coronal holes, solar wind streams, and geomagnetic disturbances during 1973-1976 are compared in a 27-day pictorial format which shows their long-term evolution. The results leave little doubt that coronal holes are related to the high-speed streams and their associated recurrent geomagnetic disturbances. In particular, these observations strongly support the hypothesis that coronal holes are the solar origin of the high-speed streams observed in the solar wind near the ecliptic plane. Title: High-latitude observations of solar wind streams and coronal holes Authors: Ricket, B. J.; Sime, D. G.; Crockett, W. R.; Tousey, R.; Sheeley, N. R., Jr. Bibcode: 1976JGR....81.3845R Altcode: Interplanetary scintillation observations of the solar wind velocity during 1973 and the first part of 1974 reveal several corotating high-speed streams. These streams, of heliographic latitudes from +40° to -60°, have been mapped back to the vicinity of the sun and have been compared with coronal holes identified in wide band XUV solar images taken during the manned portions of the Skylab mission. There is some evidence that the high-speed streams are preferentially associated with coronal holes and that they can spread out from the hole boundaries up to about 20° in latitude. However, this association is not one to one; streams are observed which do not map back to coronal holes, and holes are observed which do not lie at the base of streams. To the extent that a statistical interpretation is possible the association is not highly significant, but individual consideration of streams and holes suggests that the statistical result is biased somewhat against a strong correlation. Title: Polar faculae during the interval 1906-1975 Authors: Sheeley, N. R., Jr. Bibcode: 1976JGR....81.3462S Altcode: In a previous study (Sheeley, 1964, 1966) the numbers of faculae at the poles of the sun were counted and used to estimate the strengths of the polar magnetic fields during the period 1906-1964. The present paper extends this study to include the recent period 1964-1975. The new observations show the following: (1) The polar fields are stronger now than they have been for a decade. At the south pole, most of this increase in strength occurred in 1973 during the Skylab mission. At the north pole the change occurred gradually during 1972 and 1973. (2) Except for a relatively brief interval during 1959 the south polar field has been weaker during the last magnetic cycle than it has been during any cycle since this uniform set of observations began at Mount Wilson in 1906. Title: Energy released by the interaction of coronal magnetic fields. Authors: Sheeley, N. R., Jr. Bibcode: 1976SoPh...47..173S Altcode: Comparisons between coronal spectroheliograms and photospheric magnetograms are presented to support the idea that as coronal magnetic fields interact, a process of field line reconnection usually takes place as a natural way of preventing magnetic stresses from building up in the lower corona. This suggests that the energy which would have been stored in stressed fields is continuously released as kinetic energy of material being driven aside to make way for the reconnecting fields. However, this kinetic energy is negligible compared to the thermal energy of the coronal plasma. Therefore, it appears that these slow adjustments of coronal magnetic fields cannot account for even the normal heating of the corona, much less the energetic events associated with solar flares. Title: Coronal Changes Associated with a Disappearing Filament Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V. E.; Tousey, R.; Smith, J. B., Jr.; Speich, D. M.; Tandberg Hanssen, E.; Wilson, R. M.; de Loach, A. C.; Hoover, R. B.; McGuire, J. P. Bibcode: 1975SoPh...45..377S Altcode: This paper describes Skylab/ATM observations of the events associated with a disappearing filament near the center of the solar disk on January 18, 1974. As the filament disappeared, the nearby coronal plasma was heated to a temperature in excess of 6 × 106K. A change in the pattern of coronal emission occurred during the 11/3 hr period that the soft X-ray flux was increasing. This change seemed to consist of the formation and apparent expansion of a loop-like coronal structure which remained visible until its passage around the west limb several days later. The time history of the X-ray and microwave radio flux displayed the well-known gradual-rise-and-fall (GRF) signature, suggesting that this January 18 event may have properties characteristic of a wide class of X-ray and radio events. Title: The Calculation of Force-Free Fields from Discrete Flux Distributions Authors: Sheeley, N. R., Jr.; Harvey, J. W. Bibcode: 1975SoPh...45..275S Altcode: This paper presents particularly simple mathematical formulas for the calculation of force-free fields of constant α from the distribution of discrete sources on a flat surface. The advantage of these formulas lies in their physical simplicity and the fact that they can be easily used in practice to calculate the fields. The disadvantage is that they are limited to fields of `sufficiently small α'. These formulas may be useful in the study of chromospheric magnetic fields by the comparison of high-resolution Hα photographs and photospheric magnetograms. Title: Skylab/ATM Observations of Transient Events Having the GRF X-Ray and Microwave Character. Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Scherrer, V. E.; Tousey, R. Bibcode: 1975BAAS....7..429S Altcode: No abstract at ADS Title: The Sun's Polar Caps as Coronal Holes: Their Sizes, Evolution, and Phenomenology During the Skylab Mission. Authors: Bohlin, J. D.; Rubenstein, D. M.; Sheeley, N. R., Jr. Bibcode: 1975BAAS....7..457B Altcode: No abstract at ADS Title: X-Ray Event of August 13-15, 1973. Authors: Scherrer, V.; Sandlin, G.; Sheeley, N.; Tousey, R. Bibcode: 1975BAAS....7..430S Altcode: No abstract at ADS Title: A newly observed solar feature: macrospicules in He II 304 Å. Authors: Bohlin, J. D.; Vogel, S. N.; Purcell, J. D.; Sheeley, N. R., Jr.; Tousey, R.; Vanhoosier, M. E. Bibcode: 1975ApJ...197L.133B Altcode: He II 304 A spectroheliograms, obtained with the NRL extreme-ultraviolet slitless spectrograph during the Skylab mission, show spikelike structures at the sun's polar limb which resemble the familiar H-alpha spicules. However, the relatively large size and long life of these He II features has led to distinguishing them by the name 'macrospicules'. The macrospicules appear as protuberances or jets, ranging from 5 to over 60 sec in length, from 5 to 30 sec in width, and from 5 to over 40 minutes in lifetime. Perhaps the most radical departure from H-alpha spicules is that macrospicules occur only within the chromospheric boundaries of coronal holes. Thus macrospicules are most easily visible over the solar poles due to the coronal holes normally present there, and much less frequently at lower latitudes during limb passage of relatively rare, low-latitude coronal holes. Title: Polar Plumes in XUV Emission-Line Corona Authors: Bohlin, J. D.; Purcell, J. D.; Sheeley, N. R., Jr.; Tousey, R. Bibcode: 1975BAAS....7..356B Altcode: No abstract at ADS Title: Macro-Spicules in He II 304 Å Over the Sun's Polar Cap Authors: Bohlin, J. D.; Vogel, S. N.; Purcell, J. D.; Sheeley, N. R.; Tousey, R.; van Hoosier, M. E. Bibcode: 1975BAAS....7R.354B Altcode: No abstract at ADS Title: The High-Energy Limb Event of January 17, 1974 Authors: Tousey, R.; Bohlin, J. D.; Moe, O. K.; Purcell, J. D.; Sheeley, N. R. Bibcode: 1975BAAS....7..348T Altcode: No abstract at ADS Title: The reconnection of magnetic field lines in the solar corona. Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V. E.; Tousey, R. Bibcode: 1975ApJ...196L.129S Altcode: Skylab XUV coronal spectroheliograms and photospheric magnetograms are compared. This comparison shows that, as new bipolar magnetic fields emerge through the solar surface into the corona, the new coronal fields interact with the old ones in a manner that suggests the reconnection of the field lines. Title: Interpreting XUV Spectroheliograms in Terms of Coronal Magnetic Field Structures Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V. E.; Tousey, R. Bibcode: 1975BAAS....7Q.346S Altcode: No abstract at ADS Title: XUV Observations of Coronal Magnetic Fields Authors: Sheeley, N. R., Jr.; Bohlin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V.; Tousey, R. Bibcode: 1975SoPh...40..103S Altcode: Spectroheliograms obtained with the Naval Research Laboratory's Extreme Ultraviolet Spectrograph (S082A) on Skylab are compared with Kitt Peak National Observatory magnetograms. A principal result is the characteristic reconnection of flux from an emerging bipolar magnetic region to previously existing flux in its vicinity. Examples of the disappearance of magnetic flux from the solar atmosphere are also shown. The results of a particularly simple, potential field calculation are shown for comparison with the Skylab observations. Title: Structure of the sun's polar cap at wavelengths 240 - 600 Å. Authors: Bohlin, J. D.; Sheeley, N. R.; Tousey, R. Bibcode: 1975spre.conf..651B Altcode: No abstract at ADS Title: The 1175 Å to 1900 Å Ultraviolet Spectrum of Solar Flares Authors: Brueckner, G. E.; Bohlin, J. D.; Moe, O. K.; Nicolas, K. R.; Purcell, J. D.; Scherrer, V. E.; Sheeley, N. R., Jr.; Tousey, R. Bibcode: 1974BAAS....6..285B Altcode: No abstract at ADS Title: A Preliminary Study of Coronal Structures by Means of Time-Lapse Photography Authors: Sheeley, N. R.; Bohlin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V.; Tousey, R. Bibcode: 1974BAAS....6Q.294S Altcode: No abstract at ADS Title: Cinematographic Observations for ATM and their Comparison with some ATM Results Authors: Zirin, H.; Holt, J.; Brueckner, G. E.; Bohlin, J. D.; Purcell, J. D.; Scherrer, V. E.; Sheeley, N. R.; Tousey, R. Bibcode: 1974BAAS....6R.298Z Altcode: No abstract at ADS Title: Preliminary Results from the Nrl/atm Instruments from SKYLAB SL/2 Authors: Tousey, R.; Bartoe, J. D. F.; Bohilin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V. E.; Schumacher, R. J.; Sheeley, N. R.; Vanhoosier, M. E. Bibcode: 1974IAUS...57..491T Altcode: No abstract at ADS Title: The eruptive prominence of August 21, 1973 observed from Skylab in the white light corona and in the He II 304 Å chromosphere. Authors: Poland, A. I.; Bohlin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V. E.; Sheeley, N. R.; Tousey, R. Bibcode: 1974BAAS....6..219P Altcode: No abstract at ADS Title: The Eruptive Prominence of August 21, 1973 Observed from Skylab in the White Light Corona and in the He II 304Å Chromosphere. Authors: Poland, A. I.; Bohlin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V. E.; Sheeley, N. R.; Tousey, R. Bibcode: 1974BAAS....6..220P Altcode: No abstract at ADS Title: A Preliminary Study of the Extreme Ultraviolet Spectroheliograms from Skylab Authors: Tousey, R.; Bartoe, J. D. F.; Bohlin, J. D.; Brueckner, G. E.; Purcell, J. D.; Scherrer, V. E.; Sheeley, N. R., Jr.; Schumacher, R. J.; Vanhoosier, M. E. Bibcode: 1973SoPh...33..265T Altcode: Some of the first observations obtained with the Naval Research Laboratory's Extreme Ultraviolet Spectrograph (S082A) during the first Skylab mission are presented and compared with magnetograms and other ground-based data. The instrument is a slitless objective-type grating spectrograph covering 170-630 Å and described in Solar Phys.27, 251 (1972). Chromospheric network, loop prominences, active regions, a flare, limb brightening, XUV bright points, and `coronal holes' are among the phenomena shown and discussed. Title: Magnetic Outflow - A Stage in the Development of an Active Region Authors: Allen, R.; Edberg, S.; Labonte, B.; Sheeley, N. R. Bibcode: 1973BAAS....5Q.268A Altcode: No abstract at ADS Title: Observations of the Horizontal Velocity Field Surrounding Sunspots Authors: Sheeley, N. R., Jr. Bibcode: 1972SoPh...25...98S Altcode: During the summer and fall of 1971, Doppler spectroheliograms were obtained for several sunspots located near the solar limb. These observations confirm a previous result based on the study of only a few sunspots that in the plage-free photosphere surrounding sunspots the spatially-averaged, horizontal flow tends to be outward at 0.5-1.0 km s−1 for distances typically 10000-20000 km beyond the outer boundary of the penumbra. It is suggested that these material motions are the means by which small-scale fragments of magnetic flux are carried away from sunspots. Title: The Photospheric Velocity Field in and Around Sunspots Authors: Sheeley, N. R., Jr. Bibcode: 1972BAAS....4Q.391S Altcode: No abstract at ADS Title: Time behavior of Ca ii K2v spectral features in non-magnetic regions of the solar disk Authors: Liu, S. Y.; Sheeley, N. R.; Smith, Elske V. P., Jr. Bibcode: 1972SoPh...23..289L Altcode: No abstract at ADS Title: New Observations of Solar Magnetic and Brightness Fields Authors: Sheeley, N. R., Jr.; Liu, S. Y. Bibcode: 1972lfpm.conf..285S Altcode: No abstract at ADS Title: A comparison of the intensity variations of the CN photospheric and K line chromospheric network with time Authors: Liu, S. Y.; Sheeley, N. R., Jr. Bibcode: 1971SoPh...20..282L Altcode: No abstract at ADS Title: Using CN λ 3883 spectroheliograms to map weak photospheric magnetic fields Authors: Sheeley, N. R., Jr. Bibcode: 1971SoPh...20...19S Altcode: By photographically averaging time sequences of high-resolution CN λ 3883 spectroheliograms, the noise level due to the rapidly fluctuating intensity of the solar background has been reduced significantly. Very faint faculae that are lost in the noise on a single frame are easily visible on such an enhanced picture. A comparison between these enhanced spectroheliograms and a photoelectric magnetogram suggests that the brightness-magnetic field correlation extends to much weaker field strengths and fainter faculae than can be detected on a single, high quality CN λ 3883 spectroheliogram. Title: Two-Dimensional Observations of the Velocity Fields in and around Sunspots Authors: Sheeley, N. R., Jr.; Bhatnagar, A. Bibcode: 1971SoPh...19..338S Altcode: Doppler spectroheliograms of sunspots and their surroundings have been obtained with a spatial resolution approaching one second of arc and a time resolution of 20 s per frame. Observations of 5 sunspots, located 18°, 45°, 56°, 60° and 72° from the disk center respectively, showed considerable long-lived fine structure and, in particular, indicated the following: The Evershed outflow terminated in spoke-like structures that constitute the ragged outer boundary of the penumbra. Some of these spokes extended more than 8000 km beyond the average outer boundary. Title: Measurements of the Oscillatory and Slowly-Varying Components of the Solar Velocity Field Authors: Sheeley, N. R., Jr.; Bhatnagar, A. Bibcode: 1971SoPh...18..379S Altcode: Spectroheliograms with high spatial resolution are presented to illustrate the decomposition of the solar velocity field into its oscillatory and slowly-varying components. An analysis of data obtained in the lines FEIλ 5434 and FeIIλ 4924 yield essentially the same principal results: Spectroheliograms of the oscillatory component have a mottled appearance of rising and falling elements ranging from 2000 km to 3000 km in size. These elements oscillate vertically with a period in the range 275-300 s and an amplitude of 0.5 km/s. Although most oscillations last two cycles some have been observed for as many as four cycles. Title: The Reduction of the Solar Velocity Field into Its Oscillatory and Slowly-Varying Components Authors: Sheeley, N. R., Jr.; Bhatnagar, A. Bibcode: 1971SoPh...18..195S Altcode: Spectroheliogram movies of the solar velocity field have been made in the λ4924 line of FeII with a time resolution of 20 sec/frame and a spatial resolution in the range 1-2 sec of arc. A conventional doppler movie has been used to generate two additional movies which show the slowly-varying and oscillatory components of the velocity field separately. A basic result is the simplicity of the field patterns into which the relatively complex velocity field can be decomposed. Title: The Time Dependence of Magnetic, Velocity and Intensity Fields in the Solar Atmosphere Authors: Sheeley, N. R., Jr. Bibcode: 1971IAUS...43..310S Altcode: No abstract at ADS Title: Simultaneous Measurements of Magnetic Fields and Brightness Fields Using a 4-Image Spectroheliograph Authors: Sheeley, N. R., Jr.; Engvold, O. Bibcode: 1970SoPh...12...69S Altcode: The use of an auxiliary beamsplitter with the Kitt Peak 15-foot spectroheliograph permits spectroheliograms to be taken simultaneously in 4 identical images of the sun. By using two of these images for a Zeeman spectroheliogram, a third image for a FeI λ4071 spectroheliogram, and the fourth image for a 6107Å continuum spectroheliogram, simultaneous measurements of magnetic fields and brightness fields have been obtained. Within the limits of intensity variations imposed by doppler shifts and brightness fluctuations of the continuum, a quantitative relation does exist between the measured values of brightness and magnetic field strength of the photospheric network. For intensities measured +0.12 Å from the core of FeI λ4071, this relation is ln(1 +ΔI/I) = α¦B∥¦, whereB∥ refers to the component of magnetic field normal to the solar surface,ΔI/I is the fractional excess of brightness of the magnetic regions relative to the brightness of non-magnetic regions, and α = (6±2)%/100 gauss. Title: The Evolution of the Photospheric Network Authors: Sheeley, N. R., Jr. Bibcode: 1969SoPh....9..347S Altcode: A time-lapse sequence of spectroheliograms in the bandhead of CN at λ3883 reveals the following behavior of the photospheric network with time: There is a steady flow of bright `points' (≃ 1000 km in diameter) laterally outward from sunspots at speeds on the order of 1 km.sec−1. After traveling about 10 000 km from a sunspot they either conglomerate to form fragments of the photospheric network or disappear. Title: Spectroheliograms in Fe II λ4924 Authors: Sheeley, N. R., Jr.; Engvold, O. Bibcode: 1969BAAS....1T.292S Altcode: No abstract at ADS Title: The Photospheric Network Authors: Chapman, G. A.; Sheeley, N. R., Jr. Bibcode: 1968SoPh....5..442C Altcode: Spectroheliograms, obtained in certain Fraunhofer lines with the 82-cm solar image at the Kitt Peak National Observatory, show a bright photospheric network having the following properties: It resembles, but does not coincide with, the chromospheric network, the structure of the photospheric network being finer and more delicate than the relatively coarse structure of the chromospheric network. Title: Correlations Between Brightness Fields and Magnetic Fields on the Sun Authors: Chapman, G. A.; Sheeley, N. R., Jr. Bibcode: 1968IAUS...35..161C Altcode: No abstract at ADS Title: Observations of Small-Scale Solar Magnetic Fields Authors: Sheeley, N. R., Jr. Bibcode: 1967SoPh....1..171S Altcode: Spectrograms, obtained during moments of good seeing with the high spatial resolution afforded by the 80-cm solar image at the Kitt Peak National Observatory, show the following: Magnetic fields of several hundred gauss occur in tiny areas easily as small as 500 km in extent in regions of the solar surface sometimes well removed from areas of sunspot activity. Title: The Average Profile of the Solar K-Line during the Sunspot Cycle Authors: Sheeley, N. R., Jr. Bibcode: 1967ApJ...147.1106S Altcode: Measurements of the fraction of the solar disk covered by bright K2 emission at various phases of the sunspot cycle are presented together with measurements of the K2 emission intensity of various solar features. It is estimated that at the time of the last sunspot maximum approximately 20 per cent of the visible disk was covered by K2 emission with intensity at least three times that of the quiet disk. This corresponds to a 40 per cent increase in the average intensity of K2 emission at the time of sunspot maximum over the average intensity at the time of sunspot minimum. A smaller variation associated with solar rotation is alsd estimated. Average K-spectra for the separate hemispheres of the Sun, as they currently appear, are presented. These spectra show considerable differences which are attributed to the differences in solar activity presently existing in the two hemispheres. It is concluded that, if one regards the Sun as a point source of light, as it would appear from the vicinity of a distant star, there would be a significant variation in the intensity of its K2 emission with time corresponding to the variation of the sunspot number with time. This result emphasizes the possibility of finding "sunspot cycles" in stars by observing the intensity of K2 emission. Title: Measurements of Solar Magnetic Fields Authors: Sheeley, N. R., Jr. Bibcode: 1966ApJ...144..723S Altcode: Using the photographic technique of Leighton, high spatial resolution measurements of photospheric magnetic fields have been obtained with the following chief results: 1. Regarding sunspot groups as sources of magnetic flux and defining a "source flux" that may be determined uniquely for a sunspot group from flux measurements, we found a variation in source fluxes from group to group ranging from less than 0.2 SFU (1 SFU [solar flux unit] = 1021 maxwells) for very "small" spot groups to more than 20 SFU for very "large" groups. This variation of source flux with sunspot group "size" is described by the rule-of-thumb = 1.2 Am, where is the source flux in SFU and Am is the group size in 1018 cm2 defined as the maximum area attained by the sunspot group during its development. 2. Zeeman photographs emphasize that as a bipolar magnetic region (BMR) develops in time and as its magnetic flux spreads over a progressively larger area, the flux density does not decrease smoothly from the vicinity of the source to the outer limit of detectable flux but is distributed in successively smaller bits and fragments. Moreover, measurements obtained from these Zeeman photographs reveal magnetic field strengths of 200-700 gauss in these bits and fragments, showing that fields of a few hundred gauss are not uncommon for small magnetic features even in quiet regions of the Sun. 3. Numbers of polar faculae have been calibrated to give magnetic flux on the polar caps of the Sun as a function of time during the period 1905-1964. The fluxes vary cyclicly with time approximately 90 out of phase with the variation of the sunspot number for the whole solar disk with time during the same period (provided the sunspot number is given a polarity corresponding to the magnetic polarity of the following sunspots of the relevant hemisphere). The maxima of the polar fluxes vary considerably from cycle to cycle (just as the maxima of the sunspot number vary considerably from cycle to cycle), maximum fluxes ranging from 6 to 21 SFU, with 12 SFU being a typical maximum polar flux during 1905-1964. These results are consistent with the hypothesis that emerging BMR's are the sources of all the flux on the solar surface, and that the random walk plus differential rotation is the dominant mechanism for the distribution of the flux provided by these sources. More important, these measurements provide a means of testing this hypothesis in more detail than has been possible heretofore. Title: Measurements of Solar Magnetic Fields. Authors: Sheeley, Neil Rolfson, Jr. Bibcode: 1965PhDT.........4S Altcode: No abstract at ADS Title: Polar Faculae during the Sunspot Cycle. Authors: Sheeley, Neil R., Jr. Bibcode: 1964ApJ...140..731S Altcode: The numbers of north and south polar faculae have been counted for the period 1935-1963. The chief result is a variation of the numbers of polar faculae with time, approximately 180 out of phase with the time variation of the sunspot number for the whole solar disk. If the number of polar faculae and sunspot number both are plotted versus time with "polarities," the important feature appears that the numbers of polar faculae lag behind the sunspot number by approximately 90 . This is consistent with the supposition (Leighton 1963, 1964) that the sunspots provide a source of magnetic flux which is carried to the poles in a few years' time by means of a random-walk process associated with the convective supergranulation (Leighton, Noyes, and Simon 1962; Simon 1963) Comparison between the numbers of polar facuiae and measurements of the polar magnetic field since 1952 (Babcock 1961; Howard 1963) suggests that the past observations of polar faculae can be used to extend measurements of polar magnetic field prior to 1952.