Author name code: vanbeek ADS astronomy entries on 2022-09-14 author:Van Beek, H. Frank ------------------------------------------------------------------------ Title: The Spectrometer/Telescope for Imaging X-rays (STIX) Authors: Krucker, Säm; Hurford, G. J.; Grimm, O.; Kögl, S.; Gröbelbauer, H. -P.; Etesi, L.; Casadei, D.; Csillaghy, A.; Benz, A. O.; Arnold, N. G.; Molendini, F.; Orleanski, P.; Schori, D.; Xiao, H.; Kuhar, M.; Hochmuth, N.; Felix, S.; Schramka, F.; Marcin, S.; Kobler, S.; Iseli, L.; Dreier, M.; Wiehl, H. J.; Kleint, L.; Battaglia, M.; Lastufka, E.; Sathiapal, H.; Lapadula, K.; Bednarzik, M.; Birrer, G.; Stutz, St.; Wild, Ch.; Marone, F.; Skup, K. R.; Cichocki, A.; Ber, K.; Rutkowski, K.; Bujwan, W.; Juchnikowski, G.; Winkler, M.; Darmetko, M.; Michalska, M.; Seweryn, K.; Białek, A.; Osica, P.; Sylwester, J.; Kowalinski, M.; Ścisłowski, D.; Siarkowski, M.; Stęślicki, M.; Mrozek, T.; Podgórski, P.; Meuris, A.; Limousin, O.; Gevin, O.; Le Mer, I.; Brun, S.; Strugarek, A.; Vilmer, N.; Musset, S.; Maksimović, M.; Fárník, F.; Kozáček, Z.; Kašparová, J.; Mann, G.; Önel, H.; Warmuth, A.; Rendtel, J.; Anderson, J.; Bauer, S.; Dionies, F.; Paschke, J.; Plüschke, D.; Woche, M.; Schuller, F.; Veronig, A. M.; Dickson, E. C. M.; Gallagher, P. T.; Maloney, S. A.; Bloomfield, D. S.; Piana, M.; Massone, A. M.; Benvenuto, F.; Massa, P.; Schwartz, R. A.; Dennis, B. R.; van Beek, H. F.; Rodríguez-Pacheco, J.; Lin, R. P. Bibcode: 2020A&A...642A..15K Altcode:
Aims: The Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter is a hard X-ray imaging spectrometer, which covers the energy range from 4 to 150 keV. STIX observes hard X-ray bremsstrahlung emissions from solar flares and therefore provides diagnostics of the hottest (⪆10 MK) flare plasma while quantifying the location, spectrum, and energy content of flare-accelerated nonthermal electrons.
Methods: To accomplish this, STIX applies an indirect bigrid Fourier imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 coarsely pixelated CdTe detectors to provide information on angular scales from 7 to 180 arcsec with 1 keV energy resolution (at 6 keV). The imaging concept of STIX has intrinsically low telemetry and it is therefore well-suited to the limited resources available to the Solar Orbiter payload. To further reduce the downlinked data volume, STIX data are binned on board into 32 selectable energy bins and dynamically-adjusted time bins with a typical duration of 1 s during flares.
Results: Through hard X-ray diagnostics, STIX provides critical information for understanding the acceleration of electrons at the Sun and their transport into interplanetary space and for determining the magnetic connection of Solar Orbiter back to the Sun. In this way, STIX serves to link Solar Orbiter's remote and in-situ measurements. Title: The spectrometer telescope for imaging x-rays on board the Solar Orbiter mission Authors: Benz, A. O.; Krucker, S.; Hurford, G. J.; Arnold, N. G.; Orleanski, P.; Gröbelbauer, H. -P.; Klober, S.; Iseli, L.; Wiehl, H. J.; Csillaghy, A.; Etesi, L.; Hochmuth, N.; Battaglia, M.; Bednarzik, M.; Resanovic, R.; Grimm, O.; Viertel, G.; Commichau, V.; Meuris, A.; Limousin, O.; Brun, S.; Vilmer, N.; Skup, K. R.; Graczyk, R.; Stolarski, M.; Michalska, M.; Nowosielski, W.; Cichocki, A.; Mosdorf, M.; Seweryn, K.; Przepiórka, A.; Sylwester, J.; Kowalinski, M.; Mrozek, T.; Podgorski, P.; Mann, G.; Aurass, H.; Popow, E.; Onel, H.; Dionies, F.; Bauer, S.; Rendtel, J.; Warmuth, A.; Woche, M.; Plüschke, D.; Bittner, W.; Paschke, J.; Wolker, D.; Van Beek, H. F.; Farnik, F.; Kasparova, J.; Veronig, A. M.; Kienreich, I. W.; Gallagher, P. T.; Bloomfield, D. S.; Piana, M.; Massone, A. M.; Dennis, B. R.; Schwarz, R. A.; Lin, R. P. Bibcode: 2012SPIE.8443E..3LB Altcode: The Spectrometer Telescope for Imaging X-rays (STIX) is one of 10 instruments on board Solar Orbiter, a confirmed Mclass mission of the European Space Agency (ESA) within the Cosmic Vision program scheduled to be launched in 2017. STIX applies a Fourier-imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 pixelized CdTe detectors to provide imaging spectroscopy of solar thermal and non-thermal hard X-ray emissions from 4 to 150 keV. The status of the instrument reviewed in this paper is based on the design that passed the Preliminary Design Review (PDR) in early 2012. Particular emphasis is given to the first light of the detector system called Caliste-SO. Title: The Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) Authors: Lin, R. P.; Dennis, B. R.; Hurford, G. J.; Smith, D. M.; Zehnder, A.; Harvey, P. R.; Curtis, D. W.; Pankow, D.; Turin, P.; Bester, M.; Csillaghy, A.; Lewis, M.; Madden, N.; van Beek, H. F.; Appleby, M.; Raudorf, T.; McTiernan, J.; Ramaty, R.; Schmahl, E.; Schwartz, R.; Krucker, S.; Abiad, R.; Quinn, T.; Berg, P.; Hashii, M.; Sterling, R.; Jackson, R.; Pratt, R.; Campbell, R. D.; Malone, D.; Landis, D.; Barrington-Leigh, C. P.; Slassi-Sennou, S.; Cork, C.; Clark, D.; Amato, D.; Orwig, L.; Boyle, R.; Banks, I. S.; Shirey, K.; Tolbert, A. K.; Zarro, D.; Snow, F.; Thomsen, K.; Henneck, R.; Mchedlishvili, A.; Ming, P.; Fivian, M.; Jordan, John; Wanner, Richard; Crubb, Jerry; Preble, J.; Matranga, M.; Benz, A.; Hudson, H.; Canfield, R. C.; Holman, G. D.; Crannell, C.; Kosugi, T.; Emslie, A. G.; Vilmer, N.; Brown, J. C.; Johns-Krull, C.; Aschwanden, M.; Metcalf, T.; Conway, A. Bibcode: 2002SoPh..210....3L Altcode: RHESSI is the sixth in the NASA line of Small Explorer (SMEX) missions and the first managed in the Principal Investigator mode, where the PI is responsible for all aspects of the mission except the launch vehicle. RHESSI is designed to investigate particle acceleration and energy release in solar flares, through imaging and spectroscopy of hard X-ray/gamma-ray continua emitted by energetic electrons, and of gamma-ray lines produced by energetic ions. The single instrument consists of an imager, made up of nine bi-grid rotating modulation collimators (RMCs), in front of a spectrometer with nine cryogenically-cooled germanium detectors (GeDs), one behind each RMC. It provides the first high-resolution hard X-ray imaging spectroscopy, the first high-resolution gamma-ray line spectroscopy, and the first imaging above 100 keV including the first imaging of gamma-ray lines. The spatial resolution is as fine as ∼ 2.3 arc sec with a full-Sun (≳ 1°) field of view, and the spectral resolution is ∼ 1-10 keV FWHM over the energy range from soft X-rays (3 keV) to gamma-rays (17 MeV). An automated shutter system allows a wide dynamic range (>107) of flare intensities to be handled without instrument saturation. Data for every photon is stored in a solid-state memory and telemetered to the ground, thus allowing for versatile data analysis keyed to specific science objectives. The spin-stabilized (∼ 15 rpm) spacecraft is Sun-pointing to within ∼ 0.2° and operates autonomously. RHESSI was launched on 5 February 2002, into a nearly circular, 38° inclination, 600-km altitude orbit and began observations a week later. The mission is operated from Berkeley using a dedicated 11-m antenna for telemetry reception and command uplinks. All data and analysis software are made freely and immediately available to the scientific community. Title: High-Energy Solar Spectroscopic Imager (HESSI) Small Explorer mission for the next (2000) solar maximum Authors: Lin, Robert P.; Hurford, Gordon J.; Madden, Norman W.; Dennis, Brian R.; Crannell, Carol J.; Holman, Gordon D.; Ramaty, Reuven; von Rosenvinge, Tycho T.; Zehnder, Alex; van Beek, H. Frank; Bornmann, Patricia L.; Canfield, Richard C.; Emslie, A. Gordon; Hudson, Hugh S.; Benz, Arnold; Brown, John C.; Enome, Shinzo; Kosugi, Takeo; Vilmer, Nicole; Smith, David M.; McTiernan, Jim; Hawkins, Isabel; Slassi-Sennou, Said; Csillaghy, Andre; Fisher, George; Johns-Krull, Chris; Schwartz, Richard; Orwig, Larry E.; Zarro, Dominic; Schmahl, Ed; Aschwanden, Markus; Harvey, Peter; Curtis, Dave; Pankow, Dave; Clark, Dave; Boyle, Robert F.; Henneck, Reinhold; Michedlishvili, Akilo; Thomsen, K.; Preble, Jeff; Snow, Frank Bibcode: 1998SPIE.3442....2L Altcode: The primary scientific objective of the High Energy Solar Spectroscopic Imager (HESSI) Small Explorer mission selected by NASA is to investigate the physics of particle acceleration and energy release in solar flares. Observations will be made of x-rays and (gamma) rays from approximately 3 keV to approximately 20 MeV with an unprecedented combination of high resolution imaging and spectroscopy. The HESSI instrument utilizes Fourier- transform imaging with 9 bi-grid rotating modulation collimators and cooled germanium detectors. The instrument is mounted on a Sun-pointed spin-stabilized spacecraft and placed into a 600 km-altitude, 38 degrees inclination orbit.It will provide the first imaging spectroscopy in hard x-rays, with approximately 2 arcsecond angular resolution, time resolution down to tens of ms, and approximately 1 keV energy resolution; the first solar (gamma) ray line spectroscopy with approximately 1-5 keV energy resolution; and the first solar (gamma) -ray line and continuum imaging,with approximately 36-arcsecond angular resolution. HESSI is planned for launch in July 2000, in time to detect the thousands of flares expected during the next solar maximum. Title: The High Energy Solar Spectroscopic Imager (HESSI): A Small Explorer for the Start of the New Millennium Authors: Holman, G. D.; Lin, R. P.; Dennis, B. R.; Crannell, C. J.; Ramaty, R. R.; Rosenvinge, T. T.; Canfield, R. C.; Emslie, A. G.; Hudson, H. S.; Hurford, G. J.; Madden, N. W.; van Beek, H. F.; Benz, A.; Bornmann, P. L.; Brown, J. C.; Enome, S.; Kosugi, T.; Vilmer, N.; Zehnder, A. Bibcode: 1997AAS...191.7416H Altcode: 1997BAAS...29R1326H The High Energy Solar Spectroscopic Imager (HESSI) has been selected for launch in mid 2000, at the peak of the solar activity cycle. The primary scientific objective of HESSI is to understand particle acceleration and explosive energy release in the magnetized plasma at the Sun. HESSI will provide the first high-spectral-resolution x-ray and gamma -ray images of the Sun. It will obtain the first imaging above 100 keV, the first imaging of solar gamma -ray lines, and the first high-resolution spectroscopy of solar gamma -ray lines, including the first determination of line shapes. In two years HESSI is expected to obtain observations of tens of thousands of microflares, thousands of hard x-ray flares, and of order a hundred gamma -ray line flares. HESSI will also monitor and provide high-spectral-resolution observations of cosmic and terrestrial hard x-ray and gamma -ray transients, as well as imaging of the Crab Nebula. HESSI's high spectral, spatial, and temporal resolution and dynamic range will allow the first detailed studies of the evolution of both accelerated particles and hot, thermal plasma in solar flares. Title: The High Energy Solar Spectroscopic Imager - HESSI Authors: Dennis, B. R.; Crannell, C. J.; Holman, G. D.; Ramaty, R.; von Rosenvinge, T. T.; Benz, A.; Bornmann, P. L.; Brown, J. C.; Canfield, R. C.; Emslie, A. G.; Enome, S.; Kosugi, T.; Hudson, H. S.; Hurford, G. J.; Lin, R. P.; Ling, J. C.; Madden, N. W.; van Beek, H. F.; Vilmer, N. Bibcode: 1996AAS...188.7016D Altcode: 1996BAAS...28..941D HESSI will investigate the physics of particle acceleration and energy release in solar flares through an unprecedented combination of high resolution imaging and spectroscopy of X-rays and gamma rays from 2 keV to 20 MeV during the next solar maximum. It uses Fourier-transform imaging with 12 bi-grid modulation collimators and cooled germanium and silicon detectors mounted on a Sun-pointed spin-stabilized spacecraft in a low-altitude equatorial orbit. HESSI will carry out the first imaging spectroscopy in hard X-rays with 2 arcseconds angular resolution, time resolution to tens of ms, and ~ 1 keV energy resolution; the first gamma-ray line spectroscopy from a spacecraft with ~ 1 keV energy resolution; and the first gamma-ray line and continuum imaging with 20 arcseconds angular resolution. Title: Solar Flares Research During MAX'91 with the High Energy Imaging Device (HEIDI) Authors: Orwig, L. E.; Crannell, C. J.; Dennis, B. R.; Starr, R.; Lang, F. L.; Hurford, G. J.; Prince, T. A.; van Beek, H. F.; Greene, M. E.; Johnson, W. N.; Norris, J. P.; Wood, K. S. Bibcode: 1990BAAS...22..792O Altcode: No abstract at ADS Title: Book reviews Authors: Hovenier, J. W.; Ne'Eman, Yuval; Kleczek, J.; Vn Nes, P.; Somogyi, A. J.; Mewe, R.; Klos, Z.; Bertaux, J. L.; van Beek, H. F.; 't Hooft, G. Bibcode: 1989SSRv...51..229H Altcode: No abstract at ADS Title: Book-Review - Visions of Tomorrow - a Focus on National Space Transportation Issues Authors: Soffen, G. A.; van Beek, H. F. Bibcode: 1989SSRv...51..234S Altcode: No abstract at ADS Title: Book-Review - Engineering and Configurations of Space Stations and Platforms Authors: van Beek, H. F. Bibcode: 1986SSRv...44..185V Altcode: No abstract at ADS Title: Book reviews Authors: Gurtovenko, E. A.; Kostik, R. I.; Tlamicha, A.; Zerull, R.; Schadee, Aert; Mészáros, A.; Néeman, Y.; Giese, R. H.; Sinclair, A. T.; Kleczek, J.; Trendelenburg, E. A.; Hillebrandt, Wolfgang; Sehnal, L.; de Graaff, W.; Slottje, C.; Courvisier, T.; van Beek, H. F.; Baud, B.; de Jager, C.; Danby, J. M. A.; Somov, B. V.; Cassinelli, J.; Verbunt, F. Bibcode: 1986SSRv...44..177G Altcode: No abstract at ADS Title: Book reviews Authors: Kleczek, J.; van Gent, R. H.; Rutten, Robert J.; de Munck, J. C.; Slottje, C.; Severne, G.; Pecker, Jean-Claude; Postma, H.; Grishchuk, L. P.; Niewenhuijzen, H.; Schuiling, R. D.; van Beek, H. F.; Reijnen, G. C. M.; Heidmann, Jean; Lemaire, J.; Bleeker, Johan; Icke, V.; Neéman, Y.; Feast, M. W.; de Graaff, W. Bibcode: 1986SSRv...43..383K Altcode: No abstract at ADS Title: Book-Review - Guidance and Control - 1985 Authors: Culp, R. D.; van Beek, H. F. Bibcode: 1986SSRv...43..389C Altcode: No abstract at ADS Title: Coronal interconnection of two active regions observed in 3.5 8.0 keV X-rays Authors: Farnik, F.; van Beek, H. F.; Svestka, Z. Bibcode: 1986SoPh..104..321F Altcode: Using HXIS data, we have studied the further development of the coronal arch extending towards the SE above active region No. 17255 in November 1980. The arch, studied originally by Švestka (1984) disappeared on 10 November (after pronounced revival), but since 9 November HXIS revealed another arch-like structure towards the SW. We have studied the development of this new structure which appeared to be most likely an arch interconnecting AR 17255 with AR 17251, located nearly 30° to the west. This interconnection revived many times during the following days with intensity varying with the activity in both active regions. We have estimated the physical characteristics in this coronal structure and compared them with observations of interconnecting loops made at lower energies by Skylab in 1973. The temperature (maximum values 7.5-14 × 106 K) and the density (1.1-5.0 × 109 cm−3) are found to be higher than in the Skylab loops (a result that could be expected because the HXIS energy range was harder than that of Skylab) and similar to the values deduced for the earlier arch system extending to the SE. However, much shorter decay times of the brightness variations indicate the presence of conduction in contrast to the SE arch in which conduction was clearly inhibited. This supports the assumption that the SE and SW coronal structures were two different phenomena. Title: Book-Review - Guidance and Control Authors: Culp, R. D.; Stafford, P. S.; van Beek, H. F. Bibcode: 1984SSRv...39..379C Altcode: No abstract at ADS Title: Book reviews Authors: Doom, C.; Schrijver, C. J.; Icke, V.; Rakos, Karl D.; Kleczek, J.; Forbes, E. G.; Seboldt, W.; Linssen, P. F. J.; McKenna-Lawlor, S. M. P.; van der Kruit, P. C.; Namba, O.; van Beek, H. F. Bibcode: 1984SSRv...39..375D Altcode: No abstract at ADS Title: Book reviews Authors: van der Hucht, K. A.; Pedersen, A.; Kesák, Ľ.; Zwaan, C.; Fárník, F.; Kovalevsky, J.; van Beek, H. F.; Mewe, R.; Page, D. E.; van Genderen, A. M.; Koch-Miramond, L.; de Jager, C.; Ooms, G.; Pedersen, Arne; de Jager, C.; Hultqvist, Bengt; Waters, R.; Schrijver, J. Bibcode: 1984SSRv...38..179V Altcode: No abstract at ADS Title: A position sensitive detector system consisting of an array of mini-proportional counters. Authors: van Beek, H. F.; Boelee, A.; van der Laan, J. J. M.; Mels, W. A. Bibcode: 1984ITNS...31..791V Altcode: A new position sensitive detector system has been developed for the Hard X-ray Imaging Spectrometer launched aboard the NASA Solar Maximum Mission. The instrument operates in the energy range 3.5 - 30 keV. The Xe-gas filled detector system consists of a photon absorption compartment and an array of 900 mini-proportional counters. The detector lay-out and the system performance are described. Title: Book-Review - Space Manufacturing 1983 Authors: Burke, J. D.; Whitt, A. S.; van Beek, H. F. Bibcode: 1984SSRv...38..183B Altcode: No abstract at ADS Title: Hard X-Ray Studies of the Large Coronal Feature on June 29, 1980 Authors: Harrison, R. A.; Simnett, G. M.; Hoyng, P.; Lafleur, H.; van Beek, H. F. Bibcode: 1984sii..conf..287H Altcode: No abstract at ADS Title: Grazing incidence Focal Plane Instrument for the wavelength range 6.5 - 175 nm. Authors: Werner, W.; van Beek, H. F. Bibcode: 1984SPIE..445..272W Altcode: The result of a design study on a Focal Plane Instrument for the 6.5 to 175 nm wavelength range is described. The instrument is meant to be used in combination with a grazing incidence telescope consisting of a sector out of a full revolution configuration mirror system, type Wolter II. The presented design is based on the principles of grazing incidence reflection and conical diffraction. Simultaneously, radiation from 240 spatial pixels of 1 arcsec × 1 arcsec is analyzed in four wavelength bands. The spectral resolution varies from 0.003 nm to 0.0075 nm. For detection micro-channel arrays are chosen. Title: Book-Review - Low Light Level Detectors in Astronomy Authors: Eccles, M. J.; Sim, M. E.; Tritton, K. P.; van Beek, H. F. Bibcode: 1984SSRv...38..181E Altcode: No abstract at ADS Title: Book-Review - Developing the Space Frontier Authors: Naumann, A.; Alexander, G.; van Beek, H. F. Bibcode: 1984SSRv...38..182N Altcode: No abstract at ADS Title: Coronal interconnection of two active regions observed in 3.5-5.5 keV X-rays Authors: Farnik, F.; van Beek, H. F. Bibcode: 1984AdSpR...4g.243F Altcode: 1984AdSpR...4..243F Using HXIS data, we have studied further development of the coronal arch extending towards SE above the active region (AR) No.17255 in November 1980. The disappearance of that arch was followed by the appearance of another arch-like structure towards SW. We have studied the development of the new structure and classified it as an arch interconnecting AR 17255 with AR 17251, which was ~30° to the west. We estimate physical characteristics of this interconnection and compare them with Skylab data and the earlier arches. Title: Evidence for Extensive Magnetic Structures Between Two Active Regions from Studies of Flares on June 24, 1980 Authors: Simnett, G. M.; Harrison, R. A.; Hoyng, P.; van Beek, H. F. Bibcode: 1984sii..conf..273S Altcode: No abstract at ADS Title: The structure and evolution of a solar flare as observed in 3.5 30 keV X-rays Authors: Harrison, R. A.; Simnett, G. M.; Hoyng, P.; Lafleur, H.; van Beek, H. F. Bibcode: 1983SoPh...84..237H Altcode: On July 5, 1980 the Hard X-Ray Imaging Spectrometer on board the Solar Maximum Mission observed a complex flare event starting at 22 : 32 UT from AR 2559 (Hale 16955), then at N 28 W 29, which developed finally into a 2-ribbon flare. In this paper we compare the X-ray images with Hα photographs taken at the Big Bear Solar Observatory and identify the site of the most energetic flare phenomena. During the early phases of the event the hard X-rays (>16 keV) came from a compact source located near one of the two bright Hα kernels; we believe the latter are at the footpoints of a compact magnetic loop. The kernel identified with the X-ray source is immediately adjacent to one of the principal sunspots and in fact appears to `rotate' around the sunspot over 90° in the early phase of the flare. Two intense X-ray bursts occur at the site of the rotating kernel, and following each burst the loop fills with hot, X-ray emitting plasma. If the first burst is interpreted as bremsstrahlung from a beam of electrons impinging on a collisionally dominated medium, the energy in such electrons, >16 keV, is ∼ 5 × 1030 erg. The altitude of the looptop is 7-10 × 103 km. The temperature structure of the flare is extremely non-homogeneous, and the highest temperatures are found in the top of the loop. Title: Observations of a POST Flare Radio Burst in X-Rays Authors: Svestka, Z.; Hoyng, P.; van Tend, W.; Boelee, A.; de Jager, C.; Stewart, R. T.; Acton, L. W.; Bruner, E. C.; Gabriel, A. H.; Rapley, C. G.; de Jager, C.; LaFleur, H.; Nelson, G.; Simnett, G. M.; van Beek, H. F.; Wagner, W. J. Bibcode: 1982SoPh...75..305S Altcode: More than six hours after the two-ribbon flare of 21 May 1980, the hard X-ray spectrometer aboard the SMM imaged an extensive arch above the flare region which proved to be the lowest part of a stationary post-flare noise storm recorded at the same time at Culgoora. The X-ray arch extended over 3 or more arc minutes to a projected distance of 95 000 km, and its real altitude was most probably between 110 000 and 180 000 km. The mean electron density in the cloud was close to 109 cm−3 and its temperature stayed for many hours at a fairly constant value of about 6.5 × 106 K. The bent crystal spectrometer aboard the SMM confirms that the arch emission was basically thermal. Variations in brightness and energy spectrum at one of the supposed footpoints of the arch seem to correlate in time with radio brightness suggesting that suprathermal particles from the radio noise regions dumped in variable quantities into the low corona and transition layer; these particles may have contributed to the population of the arch, after being trapped and thermalized. The arch extended along the H∥ = 0 line thus apparently hindering any upward movement of the upper loops reconnected in the flare process. There is evidence from Culgoora that this obstacle may have been present above the flare since 15-30 min after its onset. Title: Performance of the hard X-ray imaging spectrometer. Authors: van Beek, H. F.; Fryer, R. J. Bibcode: 1982JSpRo..19..232V Altcode: No abstract at ADS Title: Optical alignment of an x-ray collimator Authors: Hoekstra, R.; D'Arnaud, T. E.; van Beek, H. F. Bibcode: 1981ApOpt..20.3630H Altcode: No abstract at ADS Title: Origin and Location of the Hard X-Ray Emission in a Two-Ribbon Flare Authors: Hoyng, P.; Duijveman, A.; Machado, M. E.; Rust, D. M.; Svestka, Z.; Boelee, A.; de Jager, C.; Frost, K. T.; Lafleur, H.; Simnett, G. M.; van Beek, H. F.; Woodgate, B. E. Bibcode: 1981ApJ...246L.155H Altcode: No abstract at ADS Title: The limb flare of 1980 April 30 as seen by the hard X-ray imaging spectrometer Authors: van Beek, H. F.; de Jager, C.; Schadee, A.; Svestka, Z.; Boelee, A.; Duijveman, A.; Galama, M.; Hoekstra, R.; Hoyng, P.; Fryer, R.; Simnett, G. M.; Imhof, J. P.; LaFleur, H.; Maseland, H. V. A. M.; Mels, W. M.; Schrijver, J.; van der Laan, J. J. M.; van Rens, P.; van Tend, W.; Werkhoven, F.; Willmore, A. P.; Wilson, J. W. G.; Machado, M. E.; Zandee, W. Bibcode: 1981ApJ...244L.157V Altcode: X-ray imaging of the limb event of 1980 April 30 shows that the flaring involved two distinct components: a pointlike component, which was the source of the initial hard X-ray burst and an extensive tongue reaching some 30,000 km above the limb. The tongue had a higher temperature than the other parts of the structure and seemed to be enhanced by energetic electrons that derived their energy from the initial source. Title: Structural development of the X-ray limb flare of 30 April 1980 Authors: de Jager, C.; Hoyng, P.; Lafleur, H.; Schadee, A.; Svestka, Z.; van Beek, H. F.; van Tend, W.; Fryer, R.; Simnett, G. M. Bibcode: 1981AdSpR...1m.251D Altcode: 1981AdSpR...1..251D We describe the development of the limb flare of 30 April 1980, 20:20 UT, as observed by the Hard X-ray Imaging Spectrometer (HXIS) aboard the Solar Maximum Mission (SMM). It consisted of a short-lived bright nucleus (FWHM < 10,000 km), just inside the Sun's limb; a longer lasting tongue, extending to a height of ~ 30,000 km, and a more complicated feature, approximately situated at the Sun's limb. The tongue was a pre-existing magnetic structure that started emitting X-rays only a few seconds after the bright nucleus, and which had a slightly higher temperature than the nucleus; its X-ray emission may be caused by electrons escaped from the nucleus. Title: Solar maximum mission experiment: Early results of the hard X-ray imaging experiment Authors: Boelee, A.; de Jager, C.; Duijveman, A.; Galama, M.; Hoekstra, R.; Hoyng, P.; Imhof, J. P.; Lafleur, H.; Maseland, H. V. A. M.; Mels, W. A.; Schadee, A.; Schrijver, J.; Svestka, Z.; van Beek, H. F.; van Rens, P.; van der Laan, J. J. M.; van Tend, W.; Werkhoven, F.; Wiersma, G.; Zandee, W.; Simnett, G. M.; Charlton, C. P.; Fryer, R.; Willmore, A. P.; Wilson, J. W. G.; Machado, M. E. Bibcode: 1981AdSpR...1m.255B Altcode: 1981AdSpR...1R.255B We have selected four widely different flares from the early period of operations of the Hard X-Ray Imaging Spectrometer (HXIS) on SMM to illustrate the characteristic imaging properties of this experiment. For the small flare of April 4, 1980, we demonstrate the instrument's capability for locating a compact source. In the weak, but extensive, flare of April 6 we show how well the instrument can display spatial structure, and also the low level of the instrument background. In the 1B flare of April 7 we are able to locate positions of the X-ray emission in the soft and hard channels, and estimate the positional variations of the emission patches. Finally, in the IN flare of April 10, which produced the strongest hard X-ray burst we have seen so far, we repeat some of the studies made for the April 7 event, and also demonstrate the capability of the HXIS instrument to study the development, with high time resolution, of individual 8'' × 8'' elements of the flare. Title: Structural development of the X-ray limb flare of 30 April 1980. Authors: de Jager, C.; Fryer, R.; Hoyng, P.; Lafleur, H.; Schadee, A.; Simnett, G. M.; Svestka, Z.; van Beek, H. F.; van Tend, W. Bibcode: 1981hea..conf..251D Altcode: No abstract at ADS Title: Solar Maximum Mission experiment: early results of the hard X-ray imaging experiment. Authors: Simnett, G. M.; Boelee, A.; Charlton, C. P.; de Jager, C.; Duijveman, A.; Fryer, R.; Galama, M.; Hoekstra, R.; Hoyng, P.; Imhof, J. P.; Lafleur, H.; Machado, M. E.; Maseland, H. V. A. M.; Mels, W. A.; Schadee, A.; Schrijver, J.; Svestka, Z.; van Beek, H. F.; van Rens, P.; van der Laan, J. J. M.; van Tend, W.; Werkhoven, F.; Wiersma, G.; Willmore, A. P.; Wilson, J. W. G.; Zandee, W. Bibcode: 1981hea..conf..255S Altcode: No abstract at ADS Title: The HXIS instrument aboard the Solar Maximum Mission Authors: van Beek, H. F.; Schrijver, H. Bibcode: 1980Ruimt..29..225V Altcode: After a review of the Solar Maximum Mission (SMM) and SMM satellite, the paper presents a detailed description of the Hard X-ray Imaging Spectrometer (HXIS) and associated equipment. Attention is given to the collimator, the detector system, the analog electronics, and the onboard computer system. The planning of observations is described, and first results are presented from April 1980. Title: The hard X-ray imaging spectrometer (HXIS). Authors: van Beek, H. F.; Hoyng, P.; Lafleur, B.; Simnett, G. M. Bibcode: 1980SoPh...65...39V Altcode: The HXIS, a joint instrument of the Space Research Laboratory at Utrecht, The Netherlands, and the Department of Space Research of the University of Birmingham, U.K., images the Sun in hard X-rays: Six energy bands in energy range 3.5-30 keV, spatial resolution 8″ over Ø 2'40″ and 32″ over Ø 6'24″ field of view, and time resolution of 0.5-7 s depending on the mode of operation. By means of a `flare flag' it alerts all the other SMM instruments when a flare sets in and informs them about the location of the X-ray emission. The experiment should yield information about the position, extension and spectrum of the hard X-ray bursts in flares, their relation to the magnetic field structure and to the quasi-thermal soft X-rays, and about the characteristics and development of `type IV' electron clouds above flare regions. Title: Solar MeV protons recorded with Experiment S99 on board ESRO-IV in 1973. Authors: van Beek, H. F.; van Gils, J. N.; de Graaff, W.; van Hees, R. M. Bibcode: 1979smpr.book.....V Altcode: No abstract at ADS Title: Solar Maximum Mission. Authors: van Beek, H. F. Bibcode: 1978nisa.symp..295V Altcode: 1978nisa.conf..295V No abstract at ADS Title: A Grid Telescope for Imaging Hard X-Rays Authors: Hudson, H. S.; Hurford, G. J.; Peterson, L. E.; van Beek, H. F. Bibcode: 1978nisa.symp..297H Altcode: 1978nisa.conf..297H No abstract at ADS Title: A Hard X-Ray Imaging Collimator Authors: van Beek, H. F. Bibcode: 1976SSI.....2..197V Altcode: The characteristics of a new type of imaging collimator, operating in the energy range 3.5-30 keV, are described. The collimator is part of an instrument (the 'Hard X-ray Imaging Spectrometer') which aims at the production of pictures in six energy bands and which has been proposed for the NASA Solar Maximum Mission. The properties of the collimator are compared with those of other imaging collimator devices and modulation collimator systems. Title: High time resolution analysis of solar hard X-ray flares observed on board the ESRO TD-1A satellite. Authors: Hoyng, Peter; Brown, John C.; van Beek, H. Frank Bibcode: 1976SoPh...48..197H Altcode: The Utrecht solar hard X-ray spectrometer S-100 on board the ESRO TD-1A satellite covers the energy range above 25 keV with 12 logarithmically spaced channels. Continuous sun-pointing is combined with high time resolution: 1.2 s for the four low energy channels (25-90 keV) and 4.8 s for the others. It is emphasized that the instrument design and calibration yield data virtually free of pile-up and other instrumental defects. Title: Elementary flare bursts. Authors: van Beek, H. F.; de Feiter, L. D.; de Jager, C. Bibcode: 1976spre.conf..819V Altcode: 1976spre.proc..819V Two hard X-ray flares observed on 2 and 7 August 1972 with the hard X-ray detector of the Utrecht Space Research Laboratory aboard ESRO's TD-1A satellite are examined in detail. It is shown that both flares can be decomposed completely into a number of individual Elementary Flare Bursts (EFB's) with no residual radiation left. For one and the same flare all EFB's seem to have approximately the same time profile but these profiles are different for the two flares investigated: the full widths at half maximum (FWHM) of the EFB's are 5 and 15 s respectively. Title: Determination of the height of hard X-ray sources in the solar atmosphere by measurement of photospheric albedo photons. Authors: Brown, J. C.; van Beek, H. F.; McClymont, A. N. Bibcode: 1975A&A....41..395B Altcode: The importance and difficulties of determining the altitude of hard X-ray sources in the solar atmosphere are discussed. It is argued that the only unambiguous means of making this measurement is by utilizing the photospherically scattered component of the radiation. Specifically, it is proposed that this can be done by measurement of the angular distribution of the large patch of photospheric albedo X-rays which is shown to accompany bright point primary X-ray sources. Quantitative predictions are made of the brightness distribution of this albedo 'image' and the practical feasibility of observing it is demonstrated in terms of the hard X-ray imaging spectrometer currently under development at the Space Research Laboratory in Utrecht. Title: Hard X-rays from the sun. Authors: van Beek, H. F.; Hoyng, P.; de Jager, C.; Stevens, G. A. Bibcode: 1975NTNA...41..101V Altcode: No abstract at ADS Title: Determination of the Height of Hard X-Ray Sources in the Solar Atmosphere by Measurement of Photospheric Albedo Photons Authors: Brown, J. C.; van Beek, H. F. Bibcode: 1975IAUS...68..239B Altcode: No abstract at ADS Title: High Time Resolution Analysis of Solar Flares Observed on the ESRO Td-Ia Satellite Authors: Hoyng, P.; Brown, J. C.; Stevens, G.; van Beek, H. F. Bibcode: 1975IAUS...68..233H Altcode: No abstract at ADS Title: High time resolution analysis of solar flares observed on the ESRO TD-1A satellite. Authors: Hoyng, P.; Brown, J. C.; Stevens, G.; van Beek, H. F. Bibcode: 1975IAUS...68Q.233H Altcode: No abstract at ADS Title: High time resolution analysis of solar flares observed on the ESRO TD-1A satellite. Authors: Hoyng, P.; Brown, J. C.; Stevens, G.; van Beek, H. F. Bibcode: 1975IAUS...68R.233H Altcode: No abstract at ADS Title: Determination of the height of hard X-ray sources in the solar atmosphere by measurement of photospheric albedo photons. Authors: Brown, J. C.; van Beek, H. F. Bibcode: 1975IAUS...68R.239B Altcode: No abstract at ADS Title: Determination of the height of hard X-ray sources in the solar atmosphere by measurement of photospheric albedo photons. Authors: Brown, J. C.; van Beek, H. F. Bibcode: 1975IAUS...68Q.239B Altcode: No abstract at ADS Title: Time Profiles and Photon Spectra of Solar Hard X-rays Authors: van Beek, H. F.; de Feiter, L. D.; de Jager, C. Bibcode: 1974ASSL...42..533V Altcode: 1974cimo.symp..533V With a spectrometer aboard the ESRO TD-1A satellite, time profiles and photon spectra of solar X-rays have been observed in the energy range above 24 keV. Most of the X-ray bursts studied thus far appear to consist of numerous short-lived spikes with rise and decay times of a few seconds. Such spikes, called 'Elementary Flare Bursts' (EFB's) cluster together in large numbers and constitute the conventional high energy flare. The form of the photon spectra could be determined very accurately and was in all cases of the power-law type. For the Aug. 4, 1972 flare, the photon spectra appear to be combinations of two power-law spectra; for the lower energies the spectral coefficient is smaller than for the higher energies. The transition energy is about 60 keV. Title: Hard X-ray observations of elementary flare bursts, and their interpretation. Authors: van Beek, H. F.; de Feiter, L. D.; de Jager, C. Bibcode: 1974spre.conf..447V Altcode: 1974spre.meet..447V Recent observations of solar hard X-ray bursts, performed with high time resolution aboard the ESRO TD-1A satellite, show that often these bursts consist of numerous short-lived spikes with rise and decay times of the order of a few seconds. It is argued that these spikes, which are called elementary flare bursts (EFB), are the essential physical phenomena, which, clustered together in large numbers, constitute the conventional high-energy flare. For some cases studied it is found that the rise and decay times can be as low as 1 to 2 seconds; individual points deviate only slightly from this average value. These times do not depend on the photon energy; this seems to indicate that the EFBs occur at a fairly low level in the chromosphere (less than or equal to 1500 km above the photosphere). For one particular case studied this conclusion is corroborated by the observation of short-lived flashes as observed optically with an interference filter centered at 3835 A. In this region a considerable part of the ambient electrons are accelerated to energies of several tens of kiloelectron volts. Title: First results of the solar hard X-ray spectrometer on board the ESRO TD-1A satellite. Authors: van Beek, H. F.; de Feiter, L. D. Bibcode: 1973spre.conf..777V Altcode: No abstract at ADS Title: Development and performance of a solar hard x-ray spectrometer Authors: van Beek, H. F. Frank Bibcode: 1973PhDT........38V Altcode: No abstract at ADS Title: The Hard Solar X-Ray Spectrometer on Board the ESRO Td-1 a Satellite Authors: van Beek, H. F.; de Feiter, L. D. Bibcode: 1973sari.conf..103V Altcode: No abstract at ADS Title: Electron-ion and ion-ion reaction rate coefficients at low altitudes during a PCA event. Authors: Larsen, T. R.; Jespersen, M.; Murdin, J.; Bowling, T. S.; van Beek, H. F.; Stevens, G. A. Bibcode: 1972JATP...34..787L Altcode: Based on experimental data from several ESRO PCA rocket flights some considerations are presented regarding the mean values of the electron-ion dissociative recombination coefficient ( αd) and the ion-ion neutralization coefficient ( αi). The estimates yield values for αd = 10 -5cm3sec-1 for heights between 60 and 67 km. The data indicate that αi is smaller than αd by a factor of 100. Title: De suksesvolle lancering van ESRO's Thor-Delta 1A satelliet. Authors: van Beek, H. F.; de Jager, C.; Lamers, H. Bibcode: 1972HemD...70..171V Altcode: No abstract at ADS Title: An Automatic Stabilized Detection System for Measuring Soft Celestial X-Rays Authors: den Boggende, A. J. F.; van Beek, H. F.; Brinkman, A. C.; Lafleur, H. Th. J. A. Bibcode: 1971IAUS...41..211D Altcode: No abstract at ADS Title: Rocket observations of protons and alpha particles at Andøya after the solar flares of 24 and 25 February 1969. Authors: van Beek, H. F.; van Gils, J. N. Bibcode: 1970spre.conf..831V Altcode: No abstract at ADS Title: Rocket Observations of Protons and α-Particles at Andøya after the Solar Flares of 24th-25th February 1969 Authors: van Beek, H. F.; Stevens, G. A. Bibcode: 1970ASSL...19..508V Altcode: 1970iso..conf..508V No abstract at ADS Title: A measurement of auroral electrons in the 1-10 MeV range Authors: Van Gils, J. N.; Van Beek, H. F.; De Fetter, L. D.; Hendrickx, R. V. Bibcode: 1969P&SS...17..255V Altcode: Particle fluxes have been measured by means of shielded Geiger-Müller telescopes mounted m a rocket, which was launched from ESRANGE(Kiruna) into a diffuse aurora. The analysis of the dependence of the counting rates on altitude indicates that a weak flux of energetic electrons, 1-10 MeV, has been detected.